let. - vol. 48 (2002) {t. - no. 10 STROJNIŠKI VESTIMIK 10 JOURNAL OF MECHANICAL ENGINEERING strani - pages 519 - 568 ISSN 0039-2480 . StrojV . STJVAX cena 800 SIT 4. " CM -------------------1» CO -------------------l_» l^. ^- O) imuliranje nastajanja gru~ dispergiranih delcev pod vplivom -z-u--n- anjega magnetnega polja A Simulation of the Cluster- Formation Process in a Dispersio of Fine Particles Under the Influen of an External Magnetic Field Analiza parametrov reverzibilne ~rpalne francisove turbine ------- An Analysis of the Parameters of Reversible Francis-Type Pump Turbines Analiza shranjevanja toplote v vodonosnikih - mo`nost uporabe v Sloveniji ------- The Analysis of Thermal Energy Storage in Aquifers - the Possibility of Application in Slovenia Analiza porazdelitve toplote bru{enju titanove zlitine VT 9 njena povezava do z ------- Analysis of the Heat when Grinding e toplote pri litine VT 9 in zaostalih napetosti t Distribution a VT 9 Ti Alloy and its Relation to Residual Stresses © Strojni{ki vestnik 48(2002)10,519 Mese~nik ISSN 0039-2480 © Journal of Mechanical Engineering 48(2002)10,519 Published monthly ISSN 0039-2480 Vsebina Contents Strojni{ki vestnik - Journal of Mechanical Engineering letnik - volume 48, (2002), {tevilka - number 10 Razprave Pristovnik, A., Krope, J., Črepinšek-Lipuš, L.: Simuliranje nastajanja gruč dispergiranih delcev pod vplivom zunanjega magnetnega polja 520 Mrkič, M.: Analiza parametrov reverzibilne Črpalne francisove turbine 528 Stritih, U., Studen, S., Brenčič, M., Lapanje, A.: Analiza shranjevanja toplote v vodonosnikih - možnost uporabe v Sloveniji 541 Neslušan, M., Czan, A., Župerl, U.: Analiza porazdelitve toplote pri brušenju titanove zlitine VT 9 in njena povezava do zaostalih napetosti 557 Osebne vesti Navodila avtorjem 565 567 Papers Pristovnik, A., Krope, J., Črepinšek-Lipuš, L.: A Simulation of the Cluster-Formation Process in a Dispersion of Fine Particles Under the Influence of an External Magnetic Field Mrkič, M.: An Analysis of the Parameters of Reversible Francis-Type Pump Turbines Stritih, U., Studen, S., Brenčič, M., Lapanje, A.: The Analysis of Thermal Energy Storage in Aquifers - the Possibility of Application in Slovenia Neslušan, M., Czan, A., Župerl, U.: Analysis of the Heat Distribution when Grinding of a VT 9 Titanium Alloy and its Relation to Residual Stresses Personal Events Instructions for Authors © Strojni{ki vestnik 48(2002)10,520-527 © Journal of Mechanical Engineering 48(2002)10,520-527 ISSN 0039-2480 ISSN 0039-2480 UDK 628.16.04/.09:004.94 UDC 628.16.04/.09:004.94 Izvirni znanstveni ~lanek (1.01) Original scientific paper (1.01) Simuliranje nastajanja gru~ dispergiranih delcev pod vplivom zunanjega magnetnega polja A Simulation of the Cluster-Formation Process in a Dispersion of Fine Particles Under the Influence of an External Magnetic Field Andrej Pristovnik - Jurij Krope - Lucija ^repin{ek-Lipu{ Naprave za magnetno obdelavo vode (MOV) so učinkovita, gospodarna in dobra ekološka rešitev za preprečevanje izločanja vodnega kamna. Na podlagi laboratorijskih preskusov so ugotovili, da je učinkovitost MOV odvisna od sestave obdelovanega disperznega sistema in obratovalnih razmer naprave. Na temelju teorije Derjagin-Landau in Verway-Overbeek (DLVO) in statistične metode Monte Carlo Metropolis smo razvili teoretični model nastajanja gruč dispergiranih delcev pod vplivom zunanjega magnetnega polja. Nadalje smo po načelu “odprtega vira” na podlagi omenjenega modela razvili računalniški program za simulacijo in grafično predstavitev nastajanja gruč pod vplivom zunanjega magnetnega polja. Rezultate izračunov smo analizirali z metodo delitve in metodo stopenjske porazdelitve. © 2002 Strojniški vestnik. Vse pravice pridržane. (Ključne besede: obdelava vode magnetna, vodni kamen, metode Monte Carlo Metropolis, analize gruč) Magnetic water-treatment (MWT) devices for scale control can be used with good economic and ecological benefits. From experimental results under well-controlled laboratory conditions we have established that the effects of MWT devices are very dependent on the composition of the treated dispersion system and their working conditions. To investigate the effects of magnetic field on the process of cluster formation in a fine-particle dispersion under the influence of the external magnetic field of a MWT device a theoretical model based on the Derjagin-Landau and Verway-Overbeek (DVLO) theory and the statistical Monte Carlo Metropolis method was used. The open-source computer programs for the simulation and the graphical presentation of clustering under the influence of an external magnetic field were developed. The results were analysed by cluster analysis, based on the partitioning and hierarchical methods. © 2002 Journal of Mechanical Engineering. All rights reserved. (Keywords: magnetic water treatment, scale prevention, Metropolis Monte Carlo, cluster analysis) 0 UVOD Magnetna obdelava vode je pogosto uporabljana metoda nekemične obdelave vode za nadzor izločanja vodnega kamna. Nadzor vodnega kamna se dosega z vodenjem napajane vode skozi magnetno polje. Je gospodarna metoda, vendar še vedno daje nezanesljive rezultate. Kljub več desetletnim proučevanjem na tem področju še ni izdelana dokončna znanstvena teorija, kako te naprave natančno delujejo in kakšni so pogoji za njihovo optimalno delovanje. Naravne vode so bogati disperzni sistemi, ki vsebujejo različne koloide, ione in druge sestavine. Zaradi naravne prenasičenosti ali pa vzpostavitve prenasičenja ob spremembah med predelavo vode (npr. sprememba temperature, tlaka ali pH) lahko na stenah cevovodov in naprav pride do izločanja nekaterih izmed teh snovi v obliki težko odstranljivih 0 INTRODUCTION Magnetic water-treatment is a frequently used non-chemical method for scale control. The scale prevention is achieved by passing the water through the magnetic field. It is an economically favorable technique, but it still gives unreliable results. Despite several decades of intensive research done in this area, no scientifically confirmed theoretical explanation exists yet that adequately describes how MWT devices work and the conditions for their effective and optimum operation. Natural waters are rich dispersion systems that contain many colloids, ions, etc. Due to the natural supersaturating of water supplied to various systems or the supersaturating as a result of changed conditions during water processing (such as pressure drop, temperature and pH) a hard scale precipitates on the pipeline and the walls of the equipment. The 0 BnnBjfokJ][p)l]Olf|i[gO | | ^SsFvWEIK | stran 520 Pristovnik A., Krope J., ^repin{ek-Lipu{ L.: Simulacija tvorbe - A Simulation of the Formation oblog vodnega kamna. MOV je še posebej obetavna metoda za uravnavanje interakcij med koloidnimi delci v vodnih disperzijah [1]. Čeprav mnogi postopki vplivajo na koloidni sistem, pomeni ravnotežje med interakcijami privlakov in odbojev (pri določeni termični dejavnosti) kriterij za stabilnost koloidnih disperzij v naravnih vodah. Natančnejše razumevanje tega vzajemnega delovanja podaja teorija DLVO [2]. Težnji delcev, da bi se združili zaradi delovanja van der Waals-Londonovih sil kratkega dosega, nasprotuje električni naboj na trdni površini, ki deluje tudi na večjih razdaljah med delci. Tako je celotna interakcijska energija med dvema koloidnima delcema (E) vsota energije elektrostatskega odboja (E ; ko se električni dvojni plasti delcev prekrivata) in energije medmolekularnega privlaka (E ; delovanje van der Waals-Londonovih sil) [2]: " MOV is a particularly promising technique for controlling the interactions among colloidal particles in water dispersions [1]. Although many processes affect colloidal behavior, the balance between attraction and repulsion interactions (for a particular level of thermal activity) is a criterion for the stability in colloid dispersions. A detailed understanding of this interplay is the basis of the DLVO theory [2]. The tendency of particles to aggregate as a result of the short-range van der Waals–London forces is counter acted by the electrically charged layer on the particles’ surfaces. Thus, the total interaction energy (Et) between two colloidal particles is the sum of the repulsion energy (Er; electric repulsion, when double layers of two particles overlap) and the attraction energy (Ea; the particles’ interaction as a result of the van der Waals–London forces) [2]: E =E +E (1). Energija elektrostatskega odboja (E) med delcema je odvisna od polmera teh delcev (a), razdalje med njunima centroma (R), elektrokinetskega potenciala (ep) in dielektrične konstante disperznega medija (e). Med enakima, okroglima, razmeroma majhnima delcema s široko električno dvojno plastjo (majhen k-«) je energija odboja: The repulsion energy (Er) between two particles depends on the radius (a), the distance between the centres of the particles (R), the electrokinetic potential (jd) and the dielectric constant (er) of the dispersion medium. For identical, spherical and relatively small particles with a wide electric double layer (ka is small) the repulsion energy is: ere0ajd2 exp(-ka(s 2)) s (2), kjer sta: s razmerje med razdaljo med središčem in premerom delca (s=R/a) in k Debye-Huckelov parameter (njegova obratna vrednost je v prvem približku enaka debelini električne dvojne plasti): where parameter s is the ratio between the distance and the radius (s=R/a) and k is the Debye-Huckel parameter (its reciprocal value is considered as a first approximation for the length of the electric double layer): k=* i ere0kBT Za okside, dispergirane v vodi, je električni potencial na trdni površini (^ določen s pH disperzije ([2] in [3]). Energija medmolekularnega privlaka (E) med dvema enako velikima, okroglima delcema je določena z enačbo: (3). For oxide minerals in water, the surface potential (jd) of the particles is determined by the pH of the dispersion ([2] and [3]). The energy of attraction (Ea) between two spherical particles with an identical radius is defined by the equation: 22 s2 + +ln kjer je kH Hamakerjeva konstanta. Magnetostatične interakcije med delci spreminjajo obnašanje tekočine in lahko destabilizirajo koloidni sistem. Ko je disperzija koloidnih delcev izpostavljena zunanjemu magnetnemu polju, se pojavijo magnetne sile, ki zmanjšujejo stabilnost koloidnega sistema. Energija magnetnega privlaka (E ) med dvema okroglima delcema na razdalji Ri je odvisna od gostote (B) in smeri delovanja zunanjega magnetnega polja, velikosti delcev (a) in magnetnih lastnosti minerala. Pri vzporedni usmeritvi magnetnih (4), where the parameter kH is the Hamaker constant. Magnetostatic particle interactions modify the behavior of the fluid and can affect the colloidal stability. When a dispersion of colloid particles is placed in an external magnetic field an additional magnetic force arises, which decreases the stability of the colloid system. The energy of the magnetic attraction (Em) between two spherical particles separated by a distance Rij depends on the magnetic density (B) and the angle of the external magnetic field, the radius of the particles (a) and the magnetic properties of the particles. For the Pristovnik A., Krope J., ^repin{ek-Lipu{ L.: Simulacija tvorbe - A Simulation of the Formation momentov dveh enakih, okroglih delcev je energija parallel-orientated magnetic moments of two identical magnetnega privlaka: particles, the energy of the magnetic interaction is: 32n2a6c2B2 9m0Ri (5). 0 ij Celotna energija (Et) interakcij med koloidnima delcema v sistemu, izpostavljenemu zunanjemu magnetnemu polju, je tako: Thus, the total energy of the interaction (Et) for colloid particles in an external magnetic field is: E =E +E +E (6). Statistične numerične metode, znane kot metode Monte Carlo, za simulacijo uporabljajo zaporedja naključnih števil. Model za proučevanje lastnosti koloidnih vodnih disperzij pod vplivom magnetnega polja ([2] do [8]) temelji na metodi Monte Carlo Metropolis ([4] in [13]). Osnova modela je dvorazsežna kvadratna celica z dolžino stranice A , z N-timi naključno razporejenimi delci (sl.1). Vsi delci so okrogli in enaki. Lega slehernega delca je znana in označena s koordinatami (x, y,Q), kjer je 9 kot med magnetnim momentom delca in zunanjim magnetnim poljem [6] (sl.2). Celotna energija sistema (ES) je enaka vsoti vseh energij interakcij med koloidnimi delci v prostoru: Metoda vsebuje izračunavanje energijskih sprememb (D E), medtem ko se koordinate enega delca v analizirani celici naključno spremenijo za majhne Statistical numerical methods, known as Monte Carlo methods, are methods that utilize sequences of random numbers to perform the simulation. The presented model is based on the Monte Carlo Metropolis ([4] and [13]) method and has been used to investigate the properties of colloid particle dispersions in water under the influence of a magnetic field ([2] to [8]). The model is based on a two-dimensional square cell with a side of length A, containing N randomly distributed particles (Fig. 1). All the particles are spherical and identical. The position of any particle is known and can be specified with coordinates (x, y,q), where q is the angle between the magnetic moment of the particle and the applied magnetic field [6] (Fig. 2). The total energy of the system (ES) is the sum of the total energies of the interactions amongst all the colloid particles: N (i) (7). The method consists of calculating the energy change (DE) when the coordinates of one particle in the analyzed cell are changed, at random, by small 70 -- ¦ *.- .-"' . - .-s. - . -- : - = s - - 60 _ _ «-. ¦- .1 : - - 50 - : '- : .- - 40 .- - - -_ - .-" 30 • _- - i. "i s-- —. 20 I - i - --_ : :. 10 0 "i : r v - .- 10 20 30 40 50 60 70 Sl. 1. Naključna porazdelitev okroglih delcev v Sl. 2. Par delcev (i j) - okrogle oblike v dvorazsežnem prostoru kvadratne oblike dvorazsežni celici ob delovanju zunanjega (A=70 mm, a=0,5 mm, N=300) magnetnega polja pod kotom y [9] Fig. 1. Randomly distributed spherical particles in Fig. 2. A pair of spherical particles (ij) in a two- a two-dimensional square cell dimensional square cell under a magnetic field (A=70 mm, a=0.5 mm, N=300) applied at an angle y[9] 0 BnnBjfokJ][p)l]Olf|i[gO | | ^SSfiflMlGC | stran 522 Pristovnik A., Krope J., ^repin{ek-Lipu{ L.: Simulacija tvorbe - A Simulation of the Formation vrednosti. V primeru, da je nova vrednost celotne energije sistema nižja od predhodne, delec ostane v novi legi; v nasprotnem primeru se izračuna faktor P in primerja z naključno vrednostjo L Le[0,1]: amounts. If the new total energy of the system is less than the previous one the particle stays in its new position; otherwise a factor P is calculated and compared with the random number L Le[0,1]. P = exp(-DE / kBT ) Če je faktor P večji od naključnega števila, delec ohrani novo lego, sicer se vrne na prvotno lego. Opisani postopek se izvede za vseh N delcev v kvadratni celici. 1 RAČUNALNIŠKI PROGRAM ZA SIMULACIJO NASTAJANJA GRUČ Pri proučevanju magnetne obdelave vode smo uporabili teorijo koloidov, matematike in statistike. Računalniški program Open Source (MCM) [15] smo priredili za dvorazsežno simulacijo postopka nastajanja gruč v finih disperzijah pod vplivom zunanjega magnetnega polja. Do takšnega nastajanja naj bi namreč prišlo v napravah MOV, kot predvidevajo nekateri avtorji ([10] in [11]). Za grafično predstavitev smo uporabili sklop računalniških programov MCM View [9] in za analizo gruč Fanny in Twins [12]. Podatki so vneseni z dvema vhodnima datotekama. V prvi datoteki so podani: velikost celice, število in fizikalne lastnosti delcev; določena je tudi struktura vmesnih izhodnih datotek. V drugi vhodni datoteki je določena izhodiščna lega delcev. Rezultati simulacije so zapisani v različnih oblikah in so lahko predstavljeni s programi, kakršna sta Microsoft Excel [15] ali Microcal Origin [15]. Za grafično predstavitev je razvit CM View program Compaq Array Visualizer [15]. Rezultati so bili nadalje ovrednoteni z metodo delitve in metodo stopenjske porazdelitve za analizo gruč po Kaufmanu in Rousseauwu [12]. V ta namen sta bila uporabljena programa Fanny in Twins. 2 REZULTATI SIMULACIJE Kot primerjalni podatki za primarne numerične izračune so bile uporabljene fizikalne lastnosti hematitnih delcev (Fe2O3) v vodni disperziji. Na podlagi tega so bili izvedeni numerični izračuni za nekatere minerale, ki ustvarjajo vodni kamen v vodi: diamagnetni kalcijev karbonat (CaCO3), kalcijev sulfat (CaSO4), silicijev dioksid (SiO2), antiferomagnetna hematit (Fe2O3), getit (FeOOH) in feromagnetni magnetit (FeO4). Za vse naštete minerale je bila simulacija nastajanja gruč izvedena v naslednjih razmerah: - različno število delcev v kvadratni celici in različni polmer a, (8). If the P factor is greater than the random number the particle retains its new position, otherwise it is returned to its original position. This procedure is applied for all N particles in a square cell. 1 A COMPUTER PROGRAM FOR THE SIMULATION OF CLUSTER FORMATION Well-known theories from the field of colloid science, statistics and mathematics have been taken into consideration and applied in magnetic water-treatment research. An open-source computer program (MCM) [15] for the two-dimensional simulation of the cluster-formation process in a fine-particles dispersion under the influence of an external magnetic field was developed. According to some authors ([10] and [11]) such a cluster formation might occur in MWT devices. A set of computer programs, MCM View [9] and Fanny and Twins [12], were used for the graphical presentation and the cluster analysis, respectively. The data are entered with two input files. In the first input file the size of the cell, the number and the physical properties of the particles are determined and the structure for the intermediate output files is defined. In the second input file the original position of the particles is determined. The results of the simulation are written in various formats and can be presented with the programs such as Microsoft Excel [15] or Microcal Origin [15]. For the graphical presentation, the MCM View program was developed on the basis of the Compaq Array Visualizer [15]. The results were further analysed with the partitioning and hierarchical methods for cluster analysis of Kaufman and Rousseauw [12]. For this purpose we used the Fanny and Twins programs. 2 RESULTS OF THE SIMULATION As the reference data for the primary numerical calculations, the physical properties of hematite particles (Fe2O3) in an aqueous dispersion were used. On this basis, the numerical calculations for some of the scale-forming minerals in the water, such as diamagnetic calcium carbonate (CaCO3), calcium sulfate (CaSO4), silicon dioxide (SiO2), antiferromagnetic hematite ( Fe 2O3), goethite (FeOOH ) and ferromagnetic magnetite (Fe3O4), were carried out. For all these minerals a simulation of cluster formation was carried out for the following conditions: - a different number of particles in the square cell and a different radius a Pristovnik A., Krope J., ^repin{ek-Lipu{ L.: Simulacija tvorbe - A Simulation of the Formation - razlicni kot y uporabljenega magnetnega polja (0, 30, 60 in 900), - različni elektrokinetski potencial ^ (10, 20 in 30 - različna gostota B uporabljenega magnetnega polja (od 0 do 1T) in - različne pH vrednosti vodnih disperzij in drugo [9]. Celotna energija interakcije je bila izračunana za delce hematita (N=40 do 300) s polmerom a=0,5 do 5 mm, volumsko magnetno susceptibilnostjo =0,02 in Hamakerjevo konstanto kH=5 10- J v kvadratni celici z dolžino stranice A=25 do 70 mm. Absolutna temperatura disperzije je bila nastavljena na 300 K in pH na 7,0. Konvergenca je glede na prejšnje raziskave [6] naravnana na 600 premikov na delec. Izhodiščna lega delcev je bila naravnana z matriko 5x8. Slika 3 prikazuje lego delcev pri 10 in 600 premikih pod vplivom magnetnega polja z gostoto 0,5 T in kotom 30°. UDI __________________________________________ ¦ ¦ -; L "J i« ta hm U3 uii Sl. 3.a. Porazdelitev delcev po 10 premikih [9] Fig. 3.a. Position of the particles after 10 shifts [9] Na sliki 3.b je razvidno nastajanje ene večje in dveh manjših gruč, ki so razporejene v smeri magnetnega polja. Iz slike ni moč neposredno ovrednotiti intenzivnosti in velikosti gruč, zato je treba rezultate analizirati z ustrezno matematično metodo. V računalniškem programu Fanny je bila uporabljena metoda logično mehke tvorbe gruč, ki je posplošitev metode delitve. Intenzivnost postopka nastajanja gruč je bila ovrednotena z normalizirano vrednostjo razdelitvenega koeficienta ( sk 5). Slika 5 prikazuje intenzivnost postopka nastajanja gruč delcev hematita pri različnih elektrokinetskih potencialih in različnih kotih uporabljenega magnetnega polja. V skladu z eksperimentalnimi rezultati [13] so učinki naprav za magnetno obdelavo vode močno odvisni od sestave obdelovanega disperznega sistema in obratovalnih razmer. Vrednost pH v sistemu 0 srinataleflMllflilrSO | ^BSfirTMlliC | stran 524 - a different angle y of the applied magnetic field (0, 30, 60 and 900) - a different electrokinetic potential » (10, 20 and 30 mV) - a different density B of the applied magnetic field (from 0 to 1T) - different pH values of the aqueous dispersions and others [9]. The total interaction energy for the hematite particles (N = 40 to 300) with the radius a=0.5 to 5 m the volume magnetic susceptibility =0.02 and the Hamaker constant kH =510- J in a square unit cell with side length A=25 to 70 mm was computed. The absolute temperature was set to 300 K and the pH was set to 7.0. According to earlier research [6], the recommended rate of convergence is up to 600 shifts per particle. The original position of the particles was set up as a 5x8 matrix. Figure 3 shows the positions of the particles after 10 and 600 shifts under a magnetic field of 0.5 T, applied at an angle of 30°. v -:- | -¦' . ¦¦' : - ¦ it ta an ii.-i. ibH b. Porazdelitev delcev po 600 premikih[9] b. Position of the particles after 600 shifts [9] In Figure 3.b the formation of one major and two minor clusters is very clear, these are well aligned in the direction of the applied magnetic field. From the same figure the intensity and the size of the cluster cannot be evaluated directly, thus the results have to be analyzed with an appropriate mathematical method. The fuzzy clustering method, as a generalization of partitioning, was used in the Fanny computer program. The intensity of the cluster-formation process was measured with the value of the normalized version of the partition coefficient ( s k =5 ). Figure 5 shows the intensity of the cluster-formation process of the hematite particles at the different electrokinetic potentials and under a magnetic field applied at different angles. According to the experimental results [13], the effects of magnetic water-treatment devices are very dependent on the composition of the treated dispersion system and working conditions. The pH value of Pristovnik A., Krope J., ^repin{ek-Lipu{ L.: Simulacija tvorbe - A Simulation of the Formation 0,70 0,65 0,60 0,55 0,50 0,45 0,40 0,35 0,30 0,25 4 * *¦ sf'" —^. ¦v. / y: \ t s. / i N /'¦^ t i i \ \ . ^ « S*' v- *...' m *<•*. ' • *. v _____^ / i i 1 2 3 4 5 6 7 8 9 10 11 12 13 1 HM) pH (/) HM Poly. ( Sl. 4. Intenzivnost nastajanja gruč v odvisnosti od pH obdelovanega sistema in aproksimacija krivulje s polinomom druge stopnje [9] Fig. 4. The intensity of the cluster-formation process versus pH and a graphical approximation with a polynomial of the second order [9] 0,80 0,70 0,60 0,50 0,40 0,30 0,20 0,80 0,70 0,60 0,50 0,40 0,30 0,25 0,50 0,75 B(T) 1,00 0,20 0,25 0,50 0,75 B(T) 1,00 Y = 30o ,j = 20mV Y = 30o,j = 30mV 0,80 0,70 0,60 0,50 0,40 0,30 0,20 0,25 0,50 0,75 B(T) 1,00 0,80 0,70 0,60 0,50 0,40 0,30 0,20 0,25 0,50 0,75 B(T) 1,00 Y = 60o ,j = 20mV Y = 60o,j = 30mV 0,80 0,70 0,60 0,50 0,40 0,30 0,20 0,25 0,50 0,75 B(T) 1,00 0,80 0,70 0,60 0,50 0,40 0,30 0,20 0,25 0,50 0,75 B(T) 1,00 Y = 90o ,j = 20mV Y = 90o,j = 30mV Sl. 5. Intenzivnost nastajanja gruč (normalizirana vrednost Dunnovega koeficienta ~sk 5 ) pod vplivom zunanjega magnetnega polja gostote 0,5 T pri različnih kotih in različnih vrednostih elektrokinetskega potenciala [9] Fig. 5. The intensity of the cluster-formation process (normalized version of Dunn’s partition coefficient, ~sk 5 ) under a magnetic field of 0.5 T applied at different angles and different retardation potentials [9] ^vmskmsmm 02-10 stran 525 |^BSSITIMIGC Pristovnik A., Krope J., ^repin{ek-Lipu{ L.: Simulacija tvorbe - A Simulation of the Formation je eden najbolj vplivnih parametrov v postopku nastajanja gruč. Za uspešno nastajanje gruč delcev hematita je optimalni pH v obdelovani disperziji 5,6 do 10,3 (sl. 4). 3 SKLEP V zadnjih desetletjih je bilo opravljenih veliko raziskav na področju magnetne obdelave vode, a je še vedno vprašljiv sam mehanizem delovanja naprav za MOV. Mehanizem je zapleten in neposredno odvisen od kemične sestave vode in obratovalnih razmer naprave MOV. Zaradi slabega poznavanja mehanizma delovanja ostaja tako njihova učinkovitost naključna. Model simulacije nastajanja gruč smo priredili za področje magnetne obdelave. Začetni izračuni so temeljili na delcih hematita. Model je utemeljen na teoriji DLVO, statistični metodi Monte Carlo Metropolis in na teoriji analize gruč. Na temelju predstavljenega modela smo z računalniškim programom simulirali in analizirali nastajanje gruč za večino snovi, ki ustvarjajo vodni kamen. Predstavljeni rezultati dobro ponazarjajo pogoje delovanja naprav za MOV ob znani kemični sestavi vode. the system is one of the most influential parameters for the cluster-formation process. For the successful clustering of hematite particles, the optimum pH range of the treated dispersion is from 5.6 to 10.3 (Fig. 4). 3 CONCLUSION Despite the large amount of research work over past decades a theoretical understanding of the MWT mechanism is still incomplete. This is the main problem when it comes to the design of efficient MWT devices. The MWT mechanism is complex and directly depends on the chemical composition of the water and the working conditions. A theoretical model for the simulation of cluster formation with hematite particles as reference data was supplemented to the region of magnetic water-treatment. The model is based on the DLVO theory, the Monte Carlo Metropolis method and the cluster-analysis theory. Numerical calculations for most of the scale-forming minerals were done with computer programs based on the presented model. The obtained results show that the model predicts well the operational conditions for the effective use of MWT devices, providing the chemical composition of the supplied water is known. 4 OZNAČBE 4 SYMBOLS polmer delca gostota magnetnega polja energija medmolekularnega privlaka energija elektrostatskega odboja energija magnetnega privlaka celotna energija interakcij Boltzmannova konstanta (1,38 . 10- J/K) Hamakerjeva konstanta število delcev Avogadrovoštevilo delcev (6,022 . 1023/mol) faktor po enačbi (8) razdalja med središčema delcev razmerje med razdaljo R in polmerom a absolutna temperatura koordinati lege delca valenca iona magnetna susceptibilnost minerala dielektrična konstanta vakuuma (8,85 . 10- As/Vm) relativna dielektrična konstanta vode elektrokinetski potencial na trdni površini Debye-Hiickelov parameter kot med magnetnim momentom delca in uporabljenim magnetnim poljem naključna vrednost med 0 in 1 kot delovanja zunanjega magnetnega polja a B ci e o Ea Er Em Et kB k H N NA P R s T x,y zi c e m Vs/m2 mol/L As J J J J J/K J 1/mol m K m m As/Vm er jd V k 1/m m0 Vs/Am q x y rad rad radius of interacting spheres magnetic field density molar concentration of ions i in the solution electron charge (1,6 . 10- As) inter-molecular attraction energy electrostatic repulsion energy magnetic attraction energy total interaction energy) Boltzmann constant (1,38 . 10-23 J/K) Hamaker constant factor by equation (8) distance between centers of particles ratio between distance R and radius a absolute temperature coordinates of particle’s position valence of ion i magnetic susceptibility of the mineral dielectric constant of vacuum (8,85 . 10- As/Vm) relative dielectric constant of water electrokinetic potential at a solid surface Debye-Hiickel parameter magnetic permeability of vacuum (4*10-7 Vs/Am) angle between the magnetic moment of the particle and the applied magnetic field random number from 0 to 1 angle of the external magnetic field 0 BnnBjfokJ][p)l]Olf|i[gO | | ^SSfiflMlGC | stran 526 Pristovnik A., Krope J., ^repin{ek-Lipu{ L.: Simulacija tvorbe - A Simulation of the Formation 5 LITERATURA 5 REFERENCES [I] Grier, D.G., S.H. Behrens (2001) Interactions in the colloidal suspensions, The James Franck Institute, The University of Chicago. [2] Svoboda, J. (1981) A theoretical approach to the magnetic flocculation of weakly magnetic minerals. International Journal of Mineral Processing, No. 8, 377-390. [3] Svoboda, J. (1982) Magnetic flocculation and treatment of fine weakly magnetic minerals. IEEE Transactions on Magnetics, No. 2, Vol. 18, 796-800. [4] Metropolis, N, A.W. Rosenbluth, M.N. Rosenbluth, A.H. Teller, E. Teller (1953) Equation of state calculations by fast computing machines. J. Chem. Phys. 21, 1087-1092. [5] Chantrell, R. W., A. Bradbury, J. Popplewell, S.W. Charles (1980) Particle cluster configuration in magnetic fluids. J. Phys. D: Appl. Phys. 13(3), UK, 119-122. [6] Chantrell, R. W., A. Bradbury, J. Popplewell, S.W. Charles (1982) Agglomerate formation in a magnetic fluid. J. Appl. Phys. 53(3), USA, 2742-2744. [7] Miles, J. J., R.W. Chantrell, M.R. Parker (1985) Model of magnetic field induced ordering in dispersions of fine paramagnetic particles. J. Appl. Phys. 57(1), USA, 4271-4273. [8] Lipus, L.C., J. Krope, L. Crepinsek, L. (2001) Dispersion destabilization in magnetic water treatment. Journal of Colloid and Interface Science 235, 60-66. [9] Pristovnik, A. (2002) Configuration and formation of clusters from dispersion particles during the magnetic water treatment. Doctoral thesis, University of Maribor, Faculty of Chemistry and Chemical Engineering. [10] Iovchev, M. (1966) The effect of magnetic field on an iron-oxygen water system. Khim. Tekhnol. Inst. 19:73-84. [II] Herzog, R. E., O. Shi, J. Patil, J.L. Katz (1989) Magnetic water treatment - the effect of iron on calcium carbonate nucleation and growth. Langmuir, Vol. 5, No. 3, 861-867. [12] Kaufman, L., J. Peter (1990) Rousseeuw finding groups in data - an introduction to cluster analysis. A Wiley-Interscience Publication, New York, Toronto. [13] Kulskii, LA., V.Z. Kochmarsky, V.V. Krivtsov (1983) Intensifying and destabilizing factors of magnetic antiscale treatment of water. Himija i tehnologija vody, Vol. 5, No. 4, 296-301. [14] CSEP Introduction to Monte Carlo Methods (1991 - 1995) electronic book, Copyright (C) by the Computational Science Education Project, http://csep1.phy.ornl.gov/CSEP/MC/MC.html [15] Računalniški programi/Computer programs: MCM, MCMr_z_a in MCM view, Copyright© 1997-2001 Andrej Pristovnik COMPAQ ARRAY VISUALIZER 1.1 Copyright© 1998-1999 Digital Equipment Corporation MicrosoftExcel, version 97, Copyright© 1985-1996 Microsoft Corporation Microcal TM Origin, version 6.0, Copyright© 1991-1990 Microcal Software, Inc. Naslova avtorjev: dr. Andrej Pristovnik dr. Lucija Črepinšek-Lipuš Univerza v Mariboru Fakulteta za strojništvo Smetanova 17 2000 Maribor Authors’ Addresses: Dr. Andrej Pristovnik Dr. Lucija Črepinšek-Lipuš University of Maribor Faculty of Mechanical Eng. Smetanova 17 2000 Maribor, Slovenia prof. dr. Jurij Krope Univerza v Mariboru Fakulteta za kemijo in kemijsko tehnologijo Smetanova 17 2000 Maribor Prof. Dr. Jurij Krope University of Maribor Faculty of Chemistry and Chemical Engineering Smetanova 17 2000 Maribor, Slovenia Prejeto: 6.3.2002 Received: Sprejeto: 22.11.2002 Accepted: © Strojni{ki vestnik 48(2002)10,528-540 © Journal of Mechanical Engineering 48(2002)10,528-540 ISSN 0039-2480 ISSN 0039-2480 UDK 621.311.21:621.224.24:621.224.7 UDC 621.311.21:621.224.24:621.224.7 Pregleni znanstveni ~lanek (1.02) Preview scientific paper (1.02) Analiza parametrov reverzibilne ~rpalne francisove turbine An Analysis of the Parameters of Reversible Francis-Type Pump Turbines Milo Mrki} Pri projektiranju reverzibilnih hidroelektrarn (RHE) mora imeti projektant na voljo čim bolj podrobne podatke o parametrih hidravličnih strojev, ki bodo v hidroelektrarno vgrajeni. Ta pogoj je se posebej pomemben, kadar gre za reverzibilne črpalno-turbinske agregate, saj morajo le-ti optimalno ustrezati režimu obratovanja v obeh smereh pretoka (črpalni in turbinski režim), da bi bila lahko vgrajena moč agregata optimalno izrabljena, tako pri polnjenju kakor tudi pri praznjenju zgornje akumulacije, in to v skladu z zahtevami elektroenergetskega sistema. Ko se projektant loti projektiranja RHE, izbere po nomenklaturi ustrezen tip turbine, potem pa -upoštevajoč splošne karakteristike in nomenklaturne diagrame - določa osnovne parametre reverzibilne črpalke - turbine (RPT). Glede na to, da je nomenklatura RPT pomanjkljiva in da obstajajo splošne karakteristike samo za omejeno število tipov, je primerno v začetni fazi projekta najprej definirati osnovne parametre RPT, v prvem koraku na temelju specifične vrtilne frekvence. V prispevku je podanih nekaj rezultatov študij razpoložljive tehnične literature kakor tudi rezultatov teoretičnega dela, modelnih preiskav in preiskav v dejanskih razmerah, ki so bile ob sodelovanju avtorja prispevka opravljene na Katedri za izkoriščanje vodnih virov v Moskvi (Institut MISI). © 2002 Strojniški vestnik. Vse pravice pridržane. (Ključne besede: projektiranje hidroelektrarn, turbine francis, črpalke reverzibilne, analize parameters) When designing pumping reservoir hydroelectric power stations the designer must have available detailed data on the parameters of the hydraulic machines that will be installed in the power plant. This is particularly important when reversible pumping-turbine units are installed, since they must best suit the working mode in both directions of the flow (pumping and turbine mode) so that the installed power of the unit is best utilized in the case of filling as well as emptying the upstream reservoir in accordance with the requirements of the public electric power system. When the planning engineer starts to project, according to the nomenclature he chooses the appropriate type of turbine and then determines the basic parameters for the reversible pump-turbine (RPT) by using universal characteristics or graphical nomenclature. Since the RPT nomenclature still does not exist and the universal characteristics only exist for a limited number of types it is appropriate at the initial stage of the design to define the basic parameters of the RPT, initially according to the specific number of revolutions. In the work in this context some results of the study of available technical literature as well as the results of theoretical works are given. The results of model researches and researches in real conditions which were performed in “exploitation of water power” university department in Moscow (institute MISI), with participation of the author are also presented. © 2002 Journal of Mechanical Engineering. All rights reserved. (Keywords: hydroelectric power stations, Francis turbines, reversible pump turbines, parameter analysis) 1 OSNOVNE KARAKTERISTKE DELOVNEGA PROCESA RPT Reverzibilni hidravlični stroj francisovega tipa ima značilnosti, ki se kažejo pri razliki njihovih osnovnih geometrijskih parametrov in obratovalnih karakteristik glede na klasične črpalke in turbine. 1 BASIC CHARACTERISTICS OF WORKING PROCESS RPT THEORY A reversible hydraulic machine of the Francis type has some specific features whose basic geometrical parameters and operating characteristics differ from the conventional pump and turbine. 0 BnnBjfokJ][p)l]Olf|i[gO | | ^SsFvWEIK | stran 528 Mrki} M.: Analiza parametrov reverzibilne - An Anlysis of the Parameters of Reversible ¦ ¦ ¦ I •!•!>. . J I/J Sl. 1. Shema reverzibilne hidroelektrarne Fig. 1. Working plan of the reversible hydro power station Predvsem je treba vedeti, da sta padec vode In particualr, it is necessary to realise that the reverzibilne hidroelektrarne (RHE) v turbinskem fall of the reversible hydroelectric power plant in the režimu (H) in višina RHE v črpalnem režimu (H) turbine working mode (H) and the head in the pump različna (sl. 1). p working (H) mode are different (Fig. 1). V turbinskem režimu je padec vode določen In the turbine working mode the fall is defined kot: as follows. Ht=Hst-ht (1), v črpalnem režimu pa višina kot: Hp=Hst+hp and the head in the pump working mode is defined as: (2), pri čemer so: H - hidrostatični padec vode (višina) h , h - hidravlične izgube. p Hidravlične izgube pri turbinskem obratovanju (ht) niso enake izgubam v črpalnem (h) are not the same as the losses in the pump working where: Hst is the water head ht , hp are the hydraulic losses The hydraulic losses during turbine operation režimu (h ) obratovanja, ker sta pretoka v enem in drugem režimu v osnovi različna in ker tudi koeficienti lokalnih izgub v dovodnem in odvodnem sistemu niso enaki v turbinski in črpalni smeri pretoka vode (sl. 3). Eulerjeva enačba za hidravlični reverzibilni stroj ima obliko: - za turbinski režim mode (h) because in principle the two flows in the first and second modes are different, and also because the coefficients of the local losses in the conduit and in the outflow system are not identical in the turbine direction and in the pump direction of the water flow (Fig. 3). Euler's equation for a reversible hydraulic machine has the following form: - for the turbine working mode ht u1-c0-cos a0 - u2 ¦ c3 • cos a3wt ( G1-G2 DGt-wt - za črpalni režim hp g-Ht g-Hp 2-n-g-Ht 2-n-g-Ht - for the pump working mode _______________________= 2-n-g-Hp = 2-n-g-Hp u1-c0-cos a0-u2-c3-cos a3 wp(G1-G2) DGp-wp pri čemer je: where: G = 2-n-r-cu- obtok (cirkulacija), G = 2 • n ¦ r ¦ cu is the circulation (3), (4), iz-n iz-n w= - kotna hitrost. w= is the angular speed Indeks 1 se nanaša na vhod v delovno kolo, The index 1 refers to the inlet to the working indeks 2 pa na izhod iz delovnega kolesa v wheel and the index 2 refers to the outlet from the turbinskem režimu. Ustrezajoči trikotniki hitrosti za working wheel in the turbine working mode. Figure 1 gfin^OtJJIMISCSD 02-10 stran 529 |^BSSITIMIGC Mrki} M.: Analiza parametrov reverzibilne - An Anlysis of the Parameters of Reversible črpalni in turbinski režim so prikazani na sliki 2. Črte vhodnih (0-0) in izhodnih (3-3) površin delovnega področja kolesa so glede na črte vhodnih (1-1) in izhodnih (2-2) robov lopatic pomaknjene, da bi se izognili vplivu končnega števila lopatic na pretok vhodnih in izhodnih prerezov (sl. 2.). črpalni režim pump regime shows the relevant triangles of the speeds in the pump and turbine working modes. The contours of the input (0-0) and outputs (3-3) working area surfaces are shifted with respect to the contours of the input (1-1) and output (2-2) edges of the moving blades to avoid influence at definitive numbers of blades on the flow in input and output cross sections (Fig. 2.). \ turbinski režim \ turbine regime Sl. 2. Osnovni geometrijski parametri RPT francisovega tipa in trikotniki hitrosti v črpalnem in turbinskem režimu Fig. 2. Basic geometrical parameters of the reversible pump - turbine of Francis type and triangles of speeds in the pump and turbine working modes Če vpeljemo oznaki: T1 -r2 =Ar oziroma I\ - r2 = ATp, dobita enačbi (3) in (4) obliko: If the terms G1 -G2 = DG and G1 -G2 = DGp are introduced, equations (3) and (4) assume the following form : 6rt-wt=2-n-g-Ht-ht 2-n-g-Hp ATp-wp hp oziroma razmerje: and/or the ratio : ATp-wp = Hp aYt wt h-ht-Ht (3') (4') (5). Če predpostavimo, da so izgube višine v If it is assumed that the head losses in the turbinskem in črpalnem režimu enake in znašajo turbine and the pump working modes are identical h =hp=0,05 • Ht , potem je skladno z (1) in (2): o ht =hp=0.05 • Ht, the following applies in accordance with (1) and (2): Ht=0,95-Hst ; H =1,05-Hst 02-10 grin^(afcflM]SCLD I ^BSfiTTMlliC | stran 530 Mrki} M.: Analiza parametrov reverzibilne - An Anlysis of the Parameters of Reversible 2 ODVISNOST OSNOVNIH PARAMETROV RPT OD SPECIFIČNE VRTILNE FREKVENCE Glede na to, da v obratovanjih RHE ni mogoče doseči enako velike stopnje izkoristka, je ugodneje imeti večjo stopnjo izkoristka v turbinskem režimu obratovanja kakor v črpalnem režimu (sl. 3), saj je cena vršne električne energije nekajkrat večja od cene električne energije v obdobjih najmanjše obremenitve elektroenergetskega sistema (sl. 4). Predpostavimo, da sta ht = 0,93 in hp = 0,90, ti dve vrednosti vstavimo v enačbo (5), dobimo: 2 DEPENDENCE OF BASIC RPT PARAMETERS ON SPECIFIC NUMBER OF REVOLUTIONS As an identical degree of efficiency cannot be reached with reversible hydroelectric power plants in both working modes (Fig. 3.) it is more convenient to have a higher degree of efficiency in the turbine working mode than in the pump working mode since the price of peak electric power is several times higher than the price of electric power during the period of least loading of the public electric power system, i.e. the price of free energy in the public electric power system (at the time when the reversible power plant operates in the pump working mode) Fig. 4. If it is assumed accordingly that ht = 0,93 and hp = 0,90 and if these values are entered into equation (5), the following is obtained: DG 1,05-H Ar-a) 0,90• 0,93-0,95-H 1, 3 (5') Na podlagi analize (5') lahko povzamemo, da moramo pri definiranju obratovalnih karakteristik reverzibilne črpalne turbine upoštevati naslednji predpostavki: 1. Če predpostavimo, da je razlika obtoka (cirkulacije) na vstopu in izstopu iz delovnega kolesa v turbinskem in črpalnem režimu enaka, to je A7" = ATt, potem mora biti vrtilna frekvenca v črpalnem režimu večje od vrtilne frekvence v turbinskem režimu (co = 1,3-cot). V praksi pomeni to uporabo dvohitrostnih generatorjev (MG), ki imajo dve vrtilni frekvenci, vendar v nasprotnih smereh. Pri tem je treba pri prehodu iz enega v drugi režim obratovanja zamenjati število parov polov, ki so trenutno v obratovanju. Pomanjkljivost te rešitve je, da se cena generatorja, električnih aparatov, sistema avtomatike in zaščite v tem primeru poveča za 25 do 30 % ob hkratnem zmanjšanju stopnje izkoristka generatorja (sl. 1). 2. V primeru enake vrtilne frekvence (cop = cot) je treba zagotoviti pogoj AT = 1,3-Art. To je mogoče doseči samo s predpostavko, da je premer delovnega kolesa v črpalnem režimu večji od premera delovnega kolesa v turbinskem režimu. Za rešitev tega problema je uporabljenih več konstrukcijskih rešitev reverzibilnih hidravličnih strojev z dvema delovnima kolesoma (črpalnim in turbinskim), ki se s posebnimi napravami vključujeta v en ali drug režim obratovanja. Primeri take rešitve so reverzibilne črpalne turbine Isogyre (Švica), Hone (ČSSR) in druge. Znane so tudi konstrukcijske rešitve s samo enim vgrajenim delovnim kolesom, katerega premer se spreminja glede na vrsto obratovanja. Vse te rešitve pa so dokaj zapletene, zato pridejo v poštev samo za agregate manjših moči. V svetovni praksi gradnje reverzibilnih agregatov velikih moči prevladuje uporaba After analyzing equation (5') we come to the conclusion that for defining the operating characteristics of the reversible pump-turbine the following assumptions must be taken into account: 1. If it is assumed that the difference of circulation at the entry into and the exit from the working wheel in the turbine and pump working mode is identical, i.e. AT" = ATt, then the number of revolutions in the pump working mode must be greater than the number of revolutions in the turbine working mode (co = 1,3 • cot). In practice this imposes the use of two-speed generators (MG), having two rotating speeds in opposite directions. When switching from one to the other working mode it is necessary to change the number of pole pairs currently in operation A disadvantage of this solution is that in this case the price of the generator, the electrical equipment and the automatic control system and protection is increased by 25-30 %, whereas the degree of efficiency of the generator is reduced (Fig. 1.). 2. In the case of an identical number of revolutions (cop = cot ) it is necessary to ensure the condition ATp = 1,3 • AT"t. This can only be reached with the assumption that the diameter of the working wheel in the pump working mode is greater than the diameter of the working wheel in the turbine working mode. In order to solve this problem in practice several design solutions for reversible hydraulic machines with two working wheels (pump and turbine working wheel), activated in one or other operating mode by special devices, are used Examples of such a solution are the reversible pump-turbines Isogyre (Switzerland) and Hone (Czechoslovakia). In addition, design solutions with one incorporated working wheel, whose diameter changes with respect to the working mode, are well known. However, all these solutions are rather complicated and so they can only be considered for low-power generating units. In most parts of the world, when building reversible power-generation units, the prevailing Mrki} M.: Analiza parametrov reverzibilne - An Anlysis of the Parameters of Reversible generatorjev z eno hitrostjo z izbiro primerne konstrukcijske rešitve delovnega kolesa hidravličnega reverzibilnega stroja z visokimi energijskimi lastnostmi v turbinskem in črpalnem režimu obratovanja (zaradi pravilne izbire profila lopatic delovnega kolesa in lopatic vodilnika). Toda iz navedenih razlogov tudi v tem primeru ni mogoče doseči optimalnih karakteristik črpalnega im turbinskega režima. To je razvidno s slike 3, na kateri so v koordinatah Q - H predstavljene tipične delovne karakteristike črpalke - turbine, pri čemer ima pretok v črpalnem režimu negativni predznak. Posebno konstrukcijo je razvil prof. Krivčenko [6]. Ta ima zaradi učinka delno pomičnih lopatic delovnega kolesa skoraj optimalno vrtljivo rešetko delovnih lopatic v turbinskem in črpalnem režimu. concept is the use of one-speed generators with the selection of a compromise design solution of the working wheel of the hydraulic reversible machine with high-power properties in the turbine and pump working mode (as a consequence of the correct selection of the contour of the working wheel blades and flow device blades). However, for the above reasons it is also not possible in this case to achieve the optimum characteristics of the pump and turbine working mode. This can be seen in Figure 3, showing in coordinates Q – H the typical working characteristics of the pump-turbine where the flow in the pump working mode has a negative sign. A special structure of RPT was developed by Prof. Krivchenko, who has a nearly optimal rotation grating of the working blade in the turbine and pump modes, on the basis of the effect at partly moveable mobile blades of the working wheel (1). Sl. 3. Tipične delovne karakteristike francisove RPT v obeh režimih obratovanja Fig. 3. Typical operating characteristics of the Francis reversible pump-turbine in both working modes Na sliki 3 je karakteristika črpalnega režima prikazana za primer nspremenljivega odprtja vodilnika (a0), kakor je to na RHE običajno. Sprememba a0 malo vpliva na vrednost pretoka, moč in stopnje izkoristka, odstopanje od optimalne vrednosti a0 pa povzroča pojav precejšnjih utripov tlaka v pretočnem prostoru turbine. Za turbinski režim so podane krivulje nespremenljivih odprtij vodilnika a0 in stopnje izkoristka do h = 0, to je do režima pobega turbine. Povečanje višine z namenom prehajanja delovnega področja na področje optimalnega izkoristka turbine pomeni hkrati prehod na področje zelo majhnih pretokov in nizkih stopenj izkoristka v primeru črpalnega režima (sl. 3). Nomenklatura reverzibilnih črpalnih turbin je pomanjkljiva, obstajajo pa glavne univerzalne karakteristike za zelo omejeno število tipov. Toda, glede na to, da se dandanes projektira vrsta RHE za zelo širok pas višin od 100 do 1200 metrov, se pokaže potreba po določanju osnovnih parametrov črpalnih turbin, v odvisnosti od teh parametrov pa tudi potreba po določanju samih RHE. Na današnji stopnji raziskav lahko izbiro reverzibilnih črpalnih turbin opravljamo na temelju In addition, Figure 3 shows the characteristic pump working mode for the case of a constant cross section of the flow device (a0), as is usual for reversible hydroelectric power plants, since the change a0 only slightly influences the value of the flow, the power and the degree of efficiency, and the deviation from the optimum value a0 results in considerable fluctuations of the pressure in the turbine flow space. For the turbine working mode the isoclines of constant cross section of the flow device a0 and of the degree of efficiency up to h = 0 i.e. up to the turbine over speed are given. The increase of the head, aimed at the working area passing into the range of optimum efficiency of the turbine, simultaneously implies passing into the range of very small flows and low degrees of efficiency in the case of the pump working mode (Fig. 3). The parts lists of reversible pump-turbines are not yet available, whereas the principal universal characteristics for a very limited number of types are available. However, considering the fact that nowadays the type of reversible hydroelectric power plants for a very wide range of heads from 100 to 1200 m is designed, the need for determining the basic parameters of the pump-turbines and, depending on those parameters, the need for determining the reversible hydroelectric power plant itself are imposed. At today’s level of research the selection of reversible pump-turbines can be made on the basis of 0 tSyTTTsJfoWJpv^DgicCD I I ^[M^lTD^DDtrS | stran 532 Mrki} M.: Analiza parametrov reverzibilne - An Anlysis of the Parameters of Reversible Sl. 4. Glavna splošna karakteristika RPT Fig. 4. Main universal characteristic of RPT (1) sistematizacije in analize statističnih podatkov sedanjih RHE, ki so že v obratovanju ali pa so v fazi projektiranja oziroma gradnje. Na inštitutu MISI v Moskvi, na Katedri za izkoriščanje vodne moči, je bila pod vodstvom prof. Aršenevskega in ob sodelovanju avtorja tega prispevka opravljena analiza več ko 40 reverzibilnih agregatov različnih zahodnih izdelovalcev. Ob tej priložnosti je bila ugotovljena naslednja odvisnost specifične vrtilne frekvence francisovih reverzibilnih črpalnih turbin v turbinskem režimu: the systematization and analysis of statistical data from the reversible hydroelectric power plants that are already in operation, being designed, or being built. At the MISI institute in Moscow, in the Department of Utilization of Water Power, an analysis of more than 40 reversible power generation units from different Western manufactures was made under the leadership of Professor Arshenevski, in cooperation with the author of this paper. On that occasion the following dependence of the specific number of revolutions of the Francis reversible pump-turbines in the turbine working mode was found: n•1,36-P 1212 H 4HH0. tmax S/-" tmax tm .4 max (6), pri čemer so: n - vrtilna frekvenca, min1 P - največja moč, kW H - največji turbinski padec RHE, m. enačba: Z analizo podatkov [1] se dobi naslednja where n is the rated number of revolutions (min-1) P is the maximum power (kW) Ht is the maximum turbine fall on the reversible hydroelectric power plant (m) If these facts are processed (1) the following ratio is obtained: 1000^1300 n= sRPT 0,4 H (6'). t max Analiza parametrov reverzibilnih hidravličnih strojev nekaterih RHE v nekdanji ZSSR in v ZDA je pokazala, da obstaja tendenca povečanja specifične vrtilne frekvence, zato je bolj However, an analysis of the parameters of reversible hydraulic machines on some reversible hydroelectric power plants in the former USSR and the USA showed that there is a tendency towards an I IgfinHŽšlbJlIMlIgiCšD I stran 533 glTMDDC Mrki} M.: Analiza parametrov reverzibilne - An Anlysis of the Parameters of Reversible primeren naslednji izraz: increase in the specific number of revolutions, therefore the following relation is more appropriate: ns = RPT 1200 + 1500 H (6''). Zanimivo je primerjati specifično vrtilno frekvenco običajnih turbin (nst) in reverzibilnih črpalnih turbin (ns ). Za klasične HE s francisovimi turbinami lahko ta parameter izrazimo kot funkcijo imenskega padca [3]: tmax It is interesting to make a comparison of the specific number of revolutions of a conventional turbine (nst ) and that of reversible pump-turbines (nsRPT ). For conventional hydroelectric power plants with Francis turbines this parameter can be expressed as a function of the rated fall: nst = 2300 H (7). opt Za klasične HE velja razmerje: On the other hand, the following ratio applies for conventional hydroelectric power plants: H opt H 0,78 - 0,95 max Če vzamemo srednjo vrednost Hop/Hmax = 0,88, dobi enačba (7) obliko: nst = Razmerje med specifično vrtilno frekvenco reverzibilnih in klasičnih francisovih turbin tako izračunamo z enačbo: If the mean value Hopt/Hmax = 0.88 is adopted, equation (7) assumes the following form: 2070 JH (8). max The ratio of the specific number of revolutions of the reversible and conventional Francis turbines gives the following relation: n sRPT = 0,58H 0.1 n st t max (9). Na podlagi H in P lahko po enačbi (6) določimo vrtilno frekvenco turbine: n = 1040 Dobljeno vrednost zaokrožimo na najbližjo sinhrono vrtilno frekvenco. Na sliki 5 so podani rezultati analize odvisnosti glavnih izmer delovnih koles nekaterih že izvedenih reverzibilnih črpalnih turbin (RPT) pri H od specifične vrtilne frekvence ns . Odvisnost enotske RPT vrtilne frekvence n11 =f(ns ) lahko na temelju izvedene analize priporočimo v obliki: As Htmax, and P are known, the number of turbine revolutions can be determined according to equation (6): H0.5 tmax 4p (10). The value obtained is approximated to the nearest synchronous number of revolutions. Figure 5 gives the results of the analysis of dependence of the main working wheel dimensions of some reversible pump-turbines already in operation, with Htmax on the specific number of revolutions nsRPT . The dependence n11 =f(nsRPT ) can be recommended in the following form on the basis of the analysis carried out: n11=82 + 0,05-ns (11). V tem primeru bo premer delovnega kolesa: In this case the working wheel diameter will be: D 1Ht max (82 + 0,05-nsRPT)7^Htm 1040-H0 (12). Če dobljeno vrednost D1 zaokrožimo na višjo vrednost do 0,1 m, moramo preveriti, ali smo dobili največjo višino v črpalnem režimu. Iz teorije črpalk je poznano razmerje [5]: If the obtained value D1 is approximated to a higher value of up to 0.1 m it is necessary to check whether the maximum head in the pump working mode has been obtained. The following ratio is known from the theory of pumps: H =K u12 = K (n'D^n 2g 2g{ 60 (13), 0 BnnBjfokJ][p)l]Olf|i[gO | | ^SsFvWEIK | stran 534 Mrki} M.: Analiza parametrov reverzibilne - An Anlysis of the Parameters of Reversible Sl. 5. Odvisnost izmer delovnega kolesa RPT od n [2] Fig. 5. Dependence of RPT working wheel dimensions s on ns [2] pri čemer je K=0,8 - 0,9, iz tega izhaja: where K=0.8-0.9, therefore: Hpmax =(0,000111- 0,000126)-n2-D12 (14). od: Tako dobimo premer D1 ki ne sme biti manjši Thus the diameter D1 is obtained, which must not be smaller than: D1 = (89 - 95)Hpm Obdelava statističnih podatkov že izdelanih reverzibilnih hidravličnih strojev je pripeljala do izkustvene odvisnosti enotnega pretoka Q11 (l/s) pri obratovanju v turbinskem režimu pri H v obliki [2]: n (15). The processing of statistical data on reversible hydraulic machines that are already built has led to the experimental dependence of the unit flow Q11 (l/s) in the case of maximum operation in the turbine working mode in the following form [2]: Q11 =(0,008 - 0,012)ns2RP (16). Po drugi strani pa lahko vrednost Q11 določimo po enačbi za specifično vrtilno frekvenco [2]: On the other hand, the value Q11 can be determined according to the equation for the specific number of revolutions: 3,65-n11-y]Q11-h (17), pri čemer ima Q11 mero m3/s. Če vzamemo vrednost h = 0,9, dobimo povezavo: where Q11 has the dimension m3/s. If the value h = 0.9 is assumed, the following relation is obtained: Q11 =(0,029 - 0,032)n1sR.8P (18). Glede na to je premer delovnega kolesa So the diameter of the working wheel upoštevajoč (11) in (16): considering (16) and (11) is: 1,166-n11-yfP D sRPT tmax (19). Premer delovnega kolesa se lahko izračuna tudi iz enačbe za moč in enotski pretok Q11 z upoštevanjem enačb (16) in (18): On the otherr hand, from the equation for the power and unit flow Q11 and by taking into account the relation (16) and (18) it is also possible to calculate the diameter of the working wheel: gfin^OtJJIMISCSD 02-10 stran 535 |^BSSIfTMlGC Mrki} M.: Analiza parametrov reverzibilne - An Anlysis of the Parameters of Reversible D1 = P 9,81 H Jh-Q11-h (20). Bodimo pozorni na koeficiente v števcu enačbe (15). To so vrednosti n11 v Črpalnem režimu za H kjer je n11t > n11p , saj je Htmax < Hpmax. Ob znani vrednosti D1 lahko izhodni premer delovnega kolesa (v turbinskem režimu) D2 , višino dovodnega aparata B1 in celotno višino delovnega kolesa B (sl. 2) določimo po diagramu na sliki 5. 3 DOLOČITEV SESALNE VIŠINE RPT Eden izmed najpomembnejših parametrov, ki odločujoče vpliva tudi na zasnovo RHE, je lega delovnega kolesa reverzibilnega stroja glede na najmanjšo koto vode v spodnji akumulaciji oziroma sesalna višina reverzibilnih hidravličnih strojev. Za RHE je značilno, da je treba sesalno višino določiti izhajajoč iz pogojev obratovanja v črpalnem režimu. Koeficient kavitacije je v tem režimu večji kakor v turbinskem režimu. Tako je na primer za RPT Kijevske RHE kavitacijski koeficient v optimalnem turbinskem obratovanju sT = 0,12 v črpalnem pa sP = 0,33. To je razlog, da je črpalka v primeru trojnih agregatov vedno vgrajena pod turbino. Po drugi strani pa je vgradnja delovnega kolesa na globinah 20 do 50 m ali več odvisna od zasnove podzemeljske ali polpodzemeljske strojnice RHE, kar ima za posledico povečanje Let us look at the coefficients in the numerator of equation (15). These are the values n11 in the pump working mode for Hpmax, where n11t >n11 p , because of Ht max Tm celotna shranjena energija (11). Za spremenljivki sta bila vzeta debelina vodonosnika h v m in pretok vode pri polnjenju Qin v m3 /d. Rezultati so za drugi krog, to je drugo leto obratovanja sistema. Pomemben dejavnik je temperatura vode pri polnjenju. Za majhne sisteme (Qi <100m3/d) in nizko temperaturo polnjenja (Ti <60 °C) je izkoristek precej majhen (manj ko 30 %). Drug pomemben dejavnik je naravna konvekcija skozi površino ter podlago vodonosnika. Za določeno debelino vodonosnika obstaja optimalen pretok, tako da preprečimo prevelike izgube. Hidravlična prevodnost K, manjša od 10 4m, zmanjša naravno konvekcijo in zato tudi vpliv debeline vodonosnika na izkoristek. A horizontal aquifer with a constant height was used. Rock basement and upper layer are also horizontal. The diameter of the well is 0.4 to 1 m, depending on aquifer depth and injected flow. Minimal temperature of backflow from the heating system is T =30°C. Temperature of filling the aquifer is constant. Water flow at filling Q and extracting Q is constant, it is valid also: Q = Q . Time for filling and emptying is the same: 180 days without additional time for storing. The efficiency is defined as: out 0____________________________________ in (pc)lQin(Tin-T0)dt 0 Depth of aquifer h and water flow at injection Q were taken as variables. The results presented are for the second cycle, which is for the second year of system operation. The minimum return temperature for the user is an important factor of the thermal efficiency of aquifer thermal energy storage. Small systems (Qin <100m3/d) and low temperature stock (T <60FC) present terefore weak thermal recovery rates (less than 30%). Natural convection is another important and unfavorable factor. For a given injection flow rate Q an optimum aquifer thickness exists, allowing to avoid buoyancy phenomena and excessive conductive losses through the bedrock and cap rock. Aquifer hydraulic conductivity K smaller than 104 m/s reduces the natural convection cells appearance, and, consequently the importance of aquifer thickness as a factor of efficiency. 0,8 0,6 0,4 h 0,2 0 h =50m, Q=1000m3 /d 60 70 80 90 100 pri/at Tmin=15°C pri/at T =30°C 110 120 Tin[°C] 0,8 0,6 h 0,4 0,2 0 h=25m, Q=500m3/d '-------- " 40 50 60 70 80 pri/at T =15°C pri/at Tmin=30°C 90 100 Sl. 4. Izkoristek sistema kot funkcija temperature vode pri polnjenju Tin, T =30 °C in T in=15 °C Fig. 4. System efficiency as a function of water temperature at min njecting Tin, "* Tmin = 30°C, Tmin = 15C Preglednica 2. Izkoristek sistema v odvisnosti od vodoravne hidravlične prevodnosti Kh Table 2. System efficiency as a function of hydraulic conductivity Kh (second cycle Tmin=30°C) h Kh h=5 26,0 29,2 32,3 h=10 h=25 h=50 h=100 h [m], Kh 10-3 12,6 Qin=100m3/d 10-4 17,6 10- 29,1 15, 8,7 10-5 24,6 10-5 31,2 34,7 10- 5,7 Qin=500m3/d 5. 10-4 -4 13,3 35,0 33,4 1,1 2,7 20,2 32,5 43,9 17,3 5. 10- -5 41,1 44,0 42, 10- 37,5 40,1 14,7 Qin=1000m3/d 5. 10- -4 23,6 43,1 47,6 21,4 10-5 46,1 [m/s], h [%] Stritih U. - Studen S. - Bren~i~ M. - Lapanje A.: Analiza shranjevanja - Tha Analysis of Storage 6 MOŽNOST UPORABE VODONOSNIKOV KOT HRANILNIKOV TOPLOTE V SLOVENIJI Slovenija je navkljub majhni površini geološko zelo pestra. Prevladujejo kamnine iz srednje zemeljske dobe, navzoče pa so tudi kamnine iz številnih drugih geoloških dob. Za slovensko ozemlje je značilna pestra tektonska dejavnost. Kamnine so prepredene s številnimi prelomi in narivi, zaradi časov so kamnine zelo poškodovane, v njih se pojavljajo številne razpoke, ki pomembno vplivajo na njihove hidrogeološke lastnosti. Tudi na porazdelitev naplavin močno vplivajo tektonske razmere. Glede na različne tipe poroznosti lahko Slovenijo razdelimo na več hidrogeoloških enot. Takšna razdelitev je dokaj groba, vendar pa v grobem poda hidrogeološke lastnosti slovenskega ozemlja. Medzrnski vodonosniki ležijo predvsem v nižinskih predelih in v dolinah velikih rek. Pokrivajo 22 odstotkov površine države. Medzrnske vodonosnike najdemo v Prekmurju, na Dravskem in Ptujskem polju, v Ljubljanski kotlini in Ljubljanskem barju, Krško-Brežiški kotlini ter v Celjski kotlini. V medzrnskih vodonosnikih praviloma leže največja in najizdatnejša črpališča pitne vode. 6 THE POSSIBILITY OF USING AQUIFERS AS THERMAL STORAGE IN SLOVENIA Despite its small area, Slovenia is geologically very diverse. Mesozoic rocks prevail, and there are also rocks from numerous other geological periods. Intensive tectonic activity is typical of the Slovenian territory. The rocks are cut with faults and thrusts, therefore they are damaged to a large extent, and numerous joints have an important influence on their hydrogeological properties. Tectonic conditions also have a strong impact on the distribution of sediments. With regard to different types of porosity Slovenia can be divided into several hydrogeological units. Such division is rather inexact, yet it can roughly define the hydrogeological properties of the Slovenian territory. Intergranular aquifers lie mainly in lowlands and in the valleys of big rivers. They cover 22% of the country’s surface. Intergranular aquifers are found in Prekmurje, in the Dravsko and Ptujsko Polje, in the Ljubljana basin and in the Ljubljansko Barje, in the Krško-Brežice basin and in the Celje basin. Intergranular aquifers generally provide the biggest and richest drinking water reservoirs. Sl. 5. Pregledna hidrogeoloska karta Slovenije (1 - kraški vodonosniki; 2 - medzrnski vodonosniki; 3 - vodonosniki z dvojno poroznostjo; 4 - razpoklinski vodonosniki; 5 - slabo prepustne kamnine) Fig. 5. Hydrogeological map of Slovenia (1 - karst aquifers; 2 - intergranular aquifers; 3 - aquifers with double porosity; 4 - interstitial aquifers; 5 - rocks with low permeability) Slovenija je znana po številnih kraških pojavih. Kraški vodonosniki prekrivajo največjo površino Slovenije, njihov delež znaša 32 odstotkov. To so predvsem apnenci, ki jih najdemo na območju Alp in Dinarskega krasa v južni Sloveniji. Kamnine, v katerih se pojavljajo le razpoke, ki pa so lahko zaradi različnih pojavov Slovenia is known for numerous karst phenomena. Karst aquifers cover the largest part of Slovenia, their share amounting to 32%. These are mostly limestones in the alpine region and in the Dinaric karst in southern Slovenia. Rocks with interstices that can also be somewhat dilated, are 02-10 grin^(afcflM]SCLD I ^BSfiTTMlliC | stran 552 Stritih U. - Studen S. - Bren~i~ M. - Lapanje A.: Analiza shranjevanja - Tha Analysis of Storage tudi nekoliko razširjene, so uvrščene v kategorijo razpoklinskih vodonosnikov, pri tem gre predvsem za različne vrste dolomitov. Ti vodonosniki prekrivajo 15% površine Slovenije. Z dvojno poroznostjo so opredeljeni predvsem peščenjaki terciarne starosti. V teh kamninah se pojavljata tako medzrnska kakor tudi razpoklinska poroznost. Te kamnine pokrivajo 11 odstotkov površine. Kot posebno kategorijo lahko izločimo slabo prepustne kamnine. To so tiste kamnine, pri katerih le stežka govorimo o njihovem potencialu za izkoriščanje podzemne vode, pokrivajo pa le dobro petino države. Sem sodijo različne vrste glinavcev, laporovcev in nekatere magmatske ter metamorfne kamnine. Za shranjevanje energije so primerni le vodonosniki z majhno hitrostjo podzemne vode. Pomembno pa je tudi, da so v bližini večjih središč, kjer je mogoče to energijo tudi dokaj poceni prenesti do uporabnikov. Na kratko si oglejmo nekaj vodonosnikov. v katerih bi bilo mogoče uskladiščiti energijo. Osnovne lastnosti teh vodonosnikov so zbrane v preglednici 3. Velenjska kadunja je mlada pliocenska tektonska udorina, ki jo zapolnjujejo rečne in potočne naplavine, predvsem gline in peski. Za tisti del vodonosnika, ki ga tvorijo peščene naplavine, so značilne srednje hidravlične prevodnosti, podzemna voda pa ima nizek gradient. Krško-Brežiško polje je obsežna kotanja, ki je zasuta s kvartarnimi naplavinami, ki se navzdol nadaljujejo v pliocenske naplavine. Skupna debelina teh sedimentov na nekaterih delih presega 200 m. V zgornjem delu imamo opraviti z dokaj visokimi hidravličnimi prevodnostmi, v spodnjem pliocenskem delu pa se te hidravlične prevodnosti močno zmanjšajo, zaradi česar se močno upočasni tudi tok podzemne vode. Kamniško-Mengeško polje je tektonska udorina, zapolnjena z mladimi kvartarnimi naplavinami, ki so po svojem izvoru predvsem ledeniškega nastanka. Debelina kvartarnih naplavin se od Kamnika proti Domžalam veča in doseže debelino večko 70 m. Zaradi strmo nagnjene predkvartarne podlage so tudi hidravlični gradienti razmeroma visoki. Na območju Prekmurskega in Murskega polja imamo opraviti z obsežnim vodonosnikom kvartarne starosti, ki se navzdol nadaljuje v pliocenske, nekoliko slabše prepustne naplavine. V kvartarnem delu vodonosnika imamo opraviti z relativno hitrim tokom podzemne vode, v pliocenskem vodonosniku, pa je tok podzemne vode počasnejši in zaradi tega primernejši za skladiščenje toplote. Gričevje Goričkega je sestavljeno iz pleistocenskih in pliocenskih rečnih naplavin v katerih je razmerje med peščeno - prodnato in glinasto - meljasto frakcijo 1 : 2. Za te peske in prode so značilne dobre do srednje hidravlične prevodnosti. Glede na geološko sestavo, ki tone v smeri severozahod -jugovzhod, te naplavine v Moravskih toplicah segajo že do globine 1000 m. V tej globini pa se pojavlja podzemna voda s temperaturo prek 60 "C. Ti peski na classified as interstitial aquifers, and are mainly different types of dolomites. These aquifers cover 15% of Slovenia. Aquifers with double porosity are mainly found in sandstones of Tertiary age. These rocks have intergranular as well interstitial porosity and have an 11% share. Rocks with low permeability are classified as a separate category. These are rocks that can hardly be considered to have any groundwater exploitation potential, and they cover only a good fifth of the country. Different types of clays, marls and some volcanic and metamorphic rocks belong into this group. Only aquifers with slow groundwater flow are suitable for heat storage. It is also very important that they are in the vicinity of larger centres where the energy can also be relatively cheaply transported to consumers. The following is a short list of some aquifers where energy could be stored. The basic properties of these aquifers are summarized in Table 1. The Velenje valley is a young Pleistocene tectonic depression filled with fluvial deposits, mainly clays and sands. The sandy part of the aquifer has medium porosity, while groundwater has a low gradient. The Krško-Brežice field is an extensive basin, filled with Quaternary sediments that are downwards followed by Pliocene sediments. Total thickness of these deposits exceeds 200 m in some parts. The upper zone has relatively high permeability which is reduced to a large extent in the lower, Pliocene part, causing also the groundwater flow to slow down. The Kamnik-Mengeš field is a tectonic depression filled with young Quaternary sediments of mostly alluvial origin. The thickness of Quaternary sediments increases from Kamnik towards Domžale and reaches more than 70 m. Because of the steep Pre-Quaternary bedrock also hydraulic gradients are relatively high. The Prekmurje and Mura field has an extensive aquifer of Quaternary age that is downwards followed by Pliocene sediments of somewhat lower permeability. Groundwater flow is relatively fast in the Quaternary part of the aquifer and slower in the Pliocene aquifer, which is consequently more suitable for heat storage. The hills of Goričko are composed of Pleistocene and Pliocene fluvial deposits with a 1:2 ratio between sand-gravel and clay-silt fractions. High to medium porosities are typical of sand and gravel. Because of the geological structure that declines in the NW-SE direction, these sediments reach already a depth of 1000 m in Moravske toplice. At this depth groundwater temperature is over 600C. The thickness of the saturated zone in these sands in Goričko is sufficient for storing energy, however it has to be | lgfinHi(š)bJ][M]lfi[j;?n 0210 stran 553 I^BSSIfTMlGC Stritih U. - Studen S. - Bren~i~ M. - Lapanje A.: Analiza shranjevanja - Tha Analysis of Storage Goričkem sicer nudijo dovolj debelo omočeno plast, ki omogoča skladiščenje energije. Ljubljansko barje je mlada tektonska udorina, v kateri se dobro prepustne plasti izmenjujejo s slabše prepustni. Opraviti imamo z dvema obsežnima vodonosnikoma V zgornjem delu imamo opraviti z odprtim vodonosnikom, v spodnjem delu pa z obsežnim zaprtim vodonosnikom, ki bi bil primeren za skladiščenje energije. pointed out that there is no source of surplus industrial heat in this area. The Ljubljansko barje is a young tectonic depression in which layers with high porosity alternate with those with lower porosity. There are two large aquifers: an open aquifer in the upper part and a closed aquifer in the lower part, which would be suitable for energy storage. Preglednica 3. Ocenjeni parametri nekaterih vodonosnikov v Sloveniji, ki so primerni za skladiščenje toplote Table 1. Estimated parameters of some aquifers in Slovenia that are suitable for heat storage lokacija in sestava location and composition Pomurje kvartarni prodi (odprt) quaternary gravels (open) pliocenski peski (zaprt) pliocene sands (closed) Goričko pliocenski peski (zaprt) pliocene sands (closed) Velenje pliocenski peski (zaprt) pliocene sands (closed) Krško globina do depth up to 3 do 5 8 – 55 0 - 50 100 10 debelina thickness 5 do 50 50 – 200 50 – 200 hidravlična prevodnost porosity m/s 10-4 -10-6 1*10-3 0,25 3,5e-02 10-6 10-6 10-6 pliokvartarni zaglinjeni prodi (zaprt) plio-quaternary clayey gravels (closed) 50 10-6 Kamnik - Mengeš kvartarni prodi (odprt) quaternary gravels (open) Lj. barje 5 - 20 10 - 50 10-4 kvartarni prodi in peski (zaprt) quaternary gravels and sands (closed) 50 15 10-4 gradient 1*10-3 1*10-3 <1*10-3 0,5 - 1*10-3 0,5 – 1*10-2 poroznost porosity 0,2 0,2 0,2 0,15 <1*10-3 0,2 hitrost flow rate m/dan m/day 4,3e-04 4,3E-04 4,3E-04 2,8E-04 0,25 1,7E-01 4,3E-04 V Sloveniji so glede na hidrogeološke lastnosti številni vodonosniki primerni za skladiščenje toplote, vendar pa so to praviloma tudi vodonosniki, ki pomenijo pomemben vir pitne vode. Zaradi tega je pri nadaljnjih raziskavah izkoriščanja vodonosnikov za potrebe uskladiščenja toplote v Sloveniji veliko pozornosti treba posvetiti morebitnim vplivom na kakovost in količino podzemne vode. Skladiščenje toplote v vodonosnike je smiselno tam, kjer obstaja vir odvečne industrijske toplote. Za vsako možno lokacijo je treba pripraviti podrobne hidrogeološke in tehnološke osnove, s katerimi se oceni bistvene parametre podzemnega skladiščenja toplote, ki so v zvezi z naravnimi pogoji skladiščenja (hitrost razširjanja toplote v vodonosniku), s tehnološkimi pogoji skladiščenja (razporeditev nalivalnih in črpalnih vodnjakov in With regard to hydrogeological properties, several aquifers in Slovenia are suitable for heat storage, yet these are as a rule also the aquifers providing an important drinking water resource. Because of this fact, further investigations of aquifer exploitation for heat storage will have to pay much attention to possible impacts upon the quality and quantity of groundwater. The storing of heat in aquifers is reasonable where there is a resource of excessive industrial heat. For each potential location, detailed hydrogeological and technological bases have to be prepared in order to estimate essential parameters of underground heat storage that are in connection with natural storage conditions (how fast heat spreads in the aquifer), with technological conditions of storage (the distribution of injection and pumping wells and their 0 BnnBjfokJ][p)l]Olf|i[gO | | ^SSfiFlMlGC | stran 554 Stritih U. - Studen S. - Bren~i~ M. - Lapanje A.: Analiza shranjevanja - Tha Analysis of Storage njihova konstrukcija, interakcija tople vode s podzemno vodo v vrtinah) ter z zakonodajnimi pogoji, povezanimi s toplotnim onesnaževanjem v vodonosnikih in vplivi na vire pitne vode. 7 SKLEP Možnost za uporabo vodonosnikov kot hranilnikov toplote se v svetu izraziteje raziskuje zadnjih petindvajset let. Po posameznih državah gredo raziskave v različne smeri, pač glede na to, kaj je lokalno pomembno. Na Japonskem iščejo rešitev v smeri le ene vrtine, medtem ko primer iz Kanade kaže rezultate raziskave o uporabi še dodatne odpadne vrtine. Posamezne države imajo različno geološko sestavo. Povsem različni sta Nizozemska in Švica. Prvo skoraj v celoti pokrivajo medzrnski vodonosniki, medtem ko so ti v Švici, katere primer je prikazan v prispevku, le v ledeniških dolinah in na redkih ravninskih delih. Za popis shranjevanja termalne energije v vodonosniku je potrebno zelo natančno poznavanje geoloških razmer. Poznati moramo hitrosti in pretoke podzemne vode. Ti se lahko po globini zelo razlikujejo, kar dodatno oteži računalniška simuliranja. Spregledati ne smemo niti naravnega vzgona. Zaradi tega je treba namestiti odvzem tople vode na manj ši globini kakor je izvedeno vbrizganje. V Sloveniji delujočega sistema, kjer bi iz vodonosnika črpali in nato vračali vodo, še ni. Izvedenih je le nekaj primerov z vkopanimi cevmi. Glede na to, da večino vodonosnikov v Sloveniji uporabljamo za črpanje pitne vode, je shranjevanje toplote v njih dokaj tvegano, ker vsako vbrizganje v vodonosnik pomeni nevarnost onesnaženja. construction, the interaction of warm water with groundwater in wells) and with legislative conditions pertaining to the heat pollution of aquifers and influences on drinking water resources. 7 CONCLUSION The possibility of aquifer utilization has been investigated in the world for the last 25 years. In different countries the research is directed towards different objectives, depending on the specific conditions in each country. The solution in Japan is directed towards one well only, whereas the example form Canada shows the utilization of one pumping well and one refuse well. Netherlands and Swiss are different. The first is almost entirely covered by intergranular aquifers whereas in Swiss aquifers are usually in glacial valleys and rare flat areas. For the description of thermal energy storage in aquifers, a detailed knowledge of the aquifer’s structure is necessary, together with the speed and flows of underground water. Those can vary considerably with the depth, presenting difficulties at computer simulations. Natural convection cannot be neglected. This is the reason why the pumping of warm water has to be performed at smaller depths than the injection of cold water. Systems that would pump warm water from the earth and inject cold water back are not known in Slovenia. The fact that most aquifers in Slovenia are used for drinking water, makes thermal energy storage in aquifers very risky. 8 SIMBOLI 8 SYMBOLS koordinate kartezičnega koordinatnega sistema specifičen tok prostorninski tok površina hidravlična prevodnost hidravlična višina gostota toplotnega toka toplotni tok toplotna prevodnost temperatura čas specifična toplota tekočine specifična toplota kamenine gostota tekočine gostota kamnine poroznost stisljivost polmer transmisivnost vodonosnika hitrost tekočine x,y,z q Q A K h j . Qt l T t cw cg rw rg f So r ta coordinates of the Cartesian system m/s specific flow m3 volumetric flow /s m2 area m/s hydraulic conductivity h hydraulic height W/m2 heat flux density W heat flux W/mK thermal conductivity K temperature s time J/kgK specific heat of fluid J/kgK specific heat of rock kg/m3 fluid density kg/m3 rock density % porosity m-1 compressibility m radius m2/d transmisivity of aquifer m/s fluid velocity gfin^OtJJIMISCSD 02-10 stran 555 |^BSSITIMIGC Stritih U. - Studen S. - Bren~i~ M. - Lapanje A.: Analiza shranjevanja - Tha Analysis of Storage komponente hitrosti tekočine gravitacijski pospešek u,v,w m/s components of fluid velocity g m/s2 gravitational acceleration 9 LITERATURA 9 REFERENCES [1] Thermische Energiespeicherung: Statusbericht 1983, Bundesministers ffir Forschung und Technologie, Jiilich 1983. [2] Sanner, B., M. Klugesheid, K. Knoblich: Numerical modelling of conductive and convective heat transport in the ground for underground thermal energy storage (UTES). [3] Anderson, O. (1991) Environment and chemical aspects of thermal energy storage in aquifers and research and development of water treatment methods. [4] Holm, T, S. Eisenreich, H. Rosenberg, N. Holm (1987) Groundwater geochemistry of short-therm aquifer thermal energy storage test cycles. [5] Dupasquir, S., A. Parriaux (2000) Parametric study of single well seasonal ATES, 8th International Conference on Thermal Energy Storage, Stuttgart. [6] Brenčič, M., J. Prestor, A. Ločniškar (2001) The analysis of the influence of highways construction on groundwater in Slovenia. In: Seiler & Wohnlich (eds.): New Approaches Characterizing Groundwater Flow. Balkema, 467 - 471, Lisse. Naslova avtorjev: dr. Uroš Stritih Sašo Studen Univerza v Ljubljani Fakulteta za strojništvo Aškerčeva 6 1000 Ljubljana uros.stritih@fs.uni-lj.si Authors‘ addresses: Dr. Uroš Stritih Sašo Studen University of Ljubljana Faculty of Mechanical Eng. Aškerčeva 6 1000 Ljubljana, Slovenia uros.stritih@fs.uni-lj.si dr. Miha Brenčič mag. Andrej Lapanje Geološki zavod Slovenije Dimičeva 14 1000 Ljubljana miha.brencic@geo-zs.si andrej.lapajne@geo-zs.si Dr. Miha Brenčič Mag. Andrej Lapanje Geological Survey of Slovenia Dimičeva 14 1000 Ljubljana, Slovenia miha.brencic@geo-zs.si andrej.lapajne@geo-zs.si Prejeto: 25.10.2002 Received: Sprejeto: 22.11.2002 Accepted: 0 SšnrKitafcflM]! ma stran 556 © Strojni{ki vestnik 48(2002)10,557-564 © Journal of Mechanical Engineering 48(2002)10,557-564 ISSN 0039-2480 ISSN 0039-2480 UDK 621.923:669.295:669.018 UDC 621.923:669.295:669.018 Strokovni ~lanek (1.04) Speciality paper (1.04) Analiza porazdelitve toplote pri bru{enju titanove zlitine VT 9 in njena povezava do zaostalih napetosti Analysis of the Heat Distribution when Grinding of a VT 9 Titanium Alloy and its Relation to Residual Stresses Miroslav Neslu{an - Andrej Czán - Uro{ @uperl Porazdelitev toplote pri strojni obdelavi je ena od fenomenoloških značilnosti tega postopka, ker pomembno vpliva na funkcionalne lastnosti obdelanih površin. Prispevek obravnava porazdelitev toplote pri brušenju titanove zlitine VT 9 in njeno razmerje do kakovosti brušenih delov, ki jo predstavljajo zaostale napetosti. Analiza porazdelitve toplote temelji na merjenju temperature na stiku brusa in obdelovanca ter obodne komponente rezalne sile. Porazdelitev toplote pri brušenju titanove zlitine VT 9 se razlikuje od porazdelitve toplote pri brušenju običajnega jekla za kotalne lezaje (14 209.4), kot tipičnega predstavnika brušenih kaljenih jekel in sicer predvsem zaradi majhne toplotne prevodnosti titanijevih zlitin. Nadalje, uporaba CBN in diamantnih brusov znatno zmanjša izpostavljenost brušenih delov toploti, predvsem kadar se uporablja hladilno-mazalna tekočina. To dejstvo pomembno vpliva na zaostale napetosti po brušenju. Rezultati analize kažejo, da obstaja močna povezava med porazdelitvijo energije in zaostalimi napetostmi. © 2002 Strojniški vestnik. Vse pravice pridržane. (Ključne besede: brušenje, zlitine titana, porazdelitve toplote, zaostale napetosti) Heat distribution during machining is one of the phenomenological characteristics of this process because it significantly influences the functional properties of machined surfaces. This paper deals with heat distribution during the grinding of a VT 9 titanium alloy and its relationship to the quality of ground parts in terms of residual stresses. The analysis of the heat distribution is based on a measurement of the temperature in the contact of the grinding wheel and workpiece, and the tangential component of the cutting force. The heat distribution when grinding a VT 9 titanium alloy differs from the heat distribution when grinding a conventional (14 209.4) roll-bearing steel (a typical representative of ground-hardened steels) mainly because of the low heat conductivity of titanium alloys. Also the application of CBN and diamond grinding wheels significantly reduces the thermal exposition of the ground parts, primarily when applying cutting fluid. This fact significantly influences the residual stresses after grinding. The results of the analysis show that there is a strong correlation between energy partitioning and residual stresses. © 2002 Journal of Mechanical Engineering. All rights reserved. (Keywords: grinding, titanium alloys, heat distributions, residual stresses) 0 UVOD Titan in njegove zlitine so priljubljeni materiali zaradi njihovega edinstvenega velikega razmerja med trdnostjo in težo, ki se ohranja pri zvišanih temperaturah ter zaradi njihove izjemne odpornosti proti koroziji. Titanove zlitine se uvrščajo med težko obdelovane materiale. Strojno obdelani deli iz titanovih zlitin so običajno izpostavljeni utrujanju, kajti najpogosteje se titan uporablja v letalski in vesoljski industriji za ogrodja letal in komponente motorjev. Fine operacije strojne obdelave imajo običajno za posledico nihajno utrujenostno trdnost, ki je mnogo večja (do približno 5-krat) kakor pri ustreznih neugodnih rezalnih razmerah [1]. Kahles idr. [2] trdijo, da se površina titanovih zlitin zlahka 0 INTRODUCTION Titanium and its alloys are attractive materials due to their very high strength-to-weight ratio, which is maintained at elevated temperatures. and their exceptional corrosion resistance. Titanium alloys are classified as difficult-to-machine materials. The machined parts made from titanium alloys are usually exposed to the fatigue load because the major applications of titanium have been in the aerospace industry, where titanium is used in airframes and engine components. Gentle machining operations usually result in a high cyclic fatigue strength that is much higher (as much as five times) than that of the corresponding unfavourable cutting conditions [1]. Kahles et al. [2] claim that the surface of titanium gfin^OtJJlMISCSD 02-10 stran 557 |^BSSITIMIGC Neslu{an M., Czán A, @uperl U.: Analiza porazdelitve toplote - Analysis of the Heat Distribution poškoduje med postopki strojne obdelave, zlasti med brušenjem. Celo ustrezna praksa brušenja z uporabo običajnih parametrov ima za posledico znatno nižjo utrujenostno trdnost zaradi poškodb površine. Poškodbe obdelovanca pri brušenju so običajno termično povzročene, in sicer ne samo zaradi toplote, nastale v coni rezanja, ampak tudi zaradi temperature na površini brušenega dela, njenega gradienta in koeficienta R - razmerja porazdelitve (razmerje med toploto, ki vstopi v obdelovanec in celotno toploto). Zaostale natezne napetosti, ki so termičnega izvora, so lahko nesprejemljive. Pri raziskavah je bilo ugotovljeno, da se ugodne tlačne napetosti bolj verjetno dosežejo z brusi CBN in diamantnimi brusi. Rezultati raziskav [3] kažejo, da je ugodneje uporabiti bruse CBN in diamantne bruse, pri katerih je vstop energije v obdelovanec manjši Razmerje porazdelitve je zato koristen pokazatelj učinkovitosti brusa glede na verjetnost nateznih napetosti. Pri brušenju običajnih jekel za kotalne ležaje in pri uporabi brusa iz korunda večina energije vstopa v obdelovanec (90%) ([3] in [4]). To je podano s kinematičnimi pogoji in z dejstvom, da je toplotna prevodnost običajnih ležajnih jekel (46 W/mK) večja kot toplotna prevodnost brusa iz korunda (6.30 W/ mK, veliko področje podanih vrednosti). Porazdelitev toplote pri brušenju titanove zlitine VT 9 se razlikuje od porazdelitve toplote pri brušenju običajnih jekel za kotalne ležaje, zaradi slabih termičnih lastnosti titanovih zlitin (toplotna prevodnost titanovih zlitin je 7,5 W/mK) in zato ta prispevek obravnava analizo toplotne porazdelitve in njeno razmerje do kakovosti brušenih delov, ki je odvisno od zaostalih napetosti. 1 EKSPERIMENTALNA METODA Eksperimentalna analiza porazdelitve toplote temelji na ‘’teoriji pomičnega vira toplote’’ [5]. Vir toplote s stalnim tokom toplote na enoto površine q, dolžino 2l, se premika vzdolž površine polneskončnega mirujočega telesa z nespremenljivo hitrostjo v . Izhodišče koordinatnih osi x, z je v središču izvora toplote. Dobimo dvorazsežno, ustaljeno porazdelitev toplote: alloys is easily damaged during machining operations, especially during grinding. Even proper grinding practice using conventional parameters results in an appreciably lower fatigue strength due to surface damage. The damage to a workpiece when grinding is usually thermally induced and comes not just from the heat generated in the cutting zone, but also by the temperature on the surface of a ground part, its gradient and R coefficient (the partition ratio: the ratio of the heat entering the workpiece to the total heat). Residual tensile stresses, which are primarily thermal in origin, may be unacceptable. Investigations have found that preferred compressive stresses are more likely to be achieved with CBN and diamond grinding wheels. Results of investigations [3] indicate an advantage of CBN and diamond grinding is a smaller proportion of the energy entering the workpiece. The partition ratio is therefore a useful indicator of grinding-wheel performance relevant to the likelihood of tensile stresses. Most of the energy enters the workpiece (90%) when grinding conventional roll-bearing steels using an alumina grinding wheel ([3] and [4]). This is given by kinematics conditions and the fact that the thermal conductivity of conventional roll-bearing steels (46 W/mK) is higher than that the alumina grinding wheel (6.30 W/mK, wide range of the presented values). The heat distribution when grinding a VT 9 titanium alloy differs from the heat distribution when grinding conventional roll-bearing steels because of the poor thermal properties of titanium alloys (the thermal conductivity of titanium alloys is 7.5 W/mK) and so this paper deals with its analysis and the relation to quality of the ground parts in terms of residual stresses. 1 EXPERIMENTAL METHOD The experimental analysis of the heat distribution is based on the “Moving Heat Source Theory” [5]. The heat source of constant heat flux per unit area q, length 2l, moves along the surface of a semi-infinite stationary body at a constant velocity v . The origin of the coordinate axes x, z is at the centre of the heat source. The two-dimensional, steady-state temperature distribution for this model is: q2kqvaw = \X-Le K0{(Z +u ) }du (1), kjer pomenijo: q - dvig temperature nad temperaturo okolice v C°, a - termično difuzivnost v m2/s, k - toplotno prevodnost v W/mK q - toplotni tok v m2kg/s, l - polovično dolžino območja izvora v m, K0 - modificirano Bessel-ovo funkcijo, u - specifično energijo brušenja v J/m3, X, Z, L - brezrazsežne vrednosti (X=v x/2a, Z=v z/ 2a, L=vl/2a). where: q – temperature rise above ambient temperature (oC), a – thermal diffusivity (m2/s), k – thermal conductivity (W/mK), q – heat flux (m2kg/s), l – half length of the band source (m), K0 – the modified Bessel function, u – specific grinding energy (J/m3), X, Z, L – dimensionless quantities (X=vw.x/2a, Z= vw.z/ 2a, L= vw.l/2a). 0 SšnrKitafcflM]! mn stran 558 Neslu{an M., Czán A, @uperl U.: Analiza porazdelitve toplote - Analysis of the Heat Distribution Takazawa je dobil rešitev za enačbo (1) z numerično integracijo. Njena poenostavljena oblika je: Takazawa obtained a solution for equation (1) by using numerical integration. Its simplified form is: ^ = 3.1L053exp(-0,69L in enačba za največji dvig temperature qd (z=0) je: 7Z) (2) and the equation for a maximum temperature rise qd (z = 0) is: qd = 0,947a0,47k-1FcRwvcvw (3), kjer pomenijo: Fc vc l c - obodno komponento sile v N, - hitrost brusa v m/s, - dolžino dotika v m. F v je skupna energija, ustvarjena v področju rezanja Q. Porazdelitev energije R se lahko izračuna tako, da vstavimo največji dvig temperature qd in obodno silo brušenja F v enačbo (3). Meritev vrednosti F je bila izvedena s piezoelektričnim merilnikom sile KISTLER skupaj z meritvijo temperature. Temperatura je bila izmerjena z metodo termoelementa (sl. 1), ki jo je uvedel Peklenik [6] in ki sta jo izboljšala Gu in Wager [7] (obe vrednosti sta bili merjeni z uporabo kartice A/D na osebnem računalniku). Rezalne razmere: v = 25 m/s, v = 4 m/min, brus A99 60LVS, profilno brušenje, s hladilno mazalno tekočino in brez nje (Emulzin z 2 % koncentracijo). Strojno obdelani materiali: 1. titanova zlitina VT 9 - termična difuzivnost 2,87 10 6 m2/s, meja plastičnosti Rm = 900 MPa po žarjenju. Sestava zlitine VT 9 je iz faze a in b. Njena kemična sestava je podana v preglednici 1. 2. Kaljeno jeklo za kotalne ležaje (14 209.4) - termična where: F - tangential force component (N), v - wheel speed (m/s), l - contact length (m). F v is the total energy created in the cutting zone Q. The c energy partition Rw can be calculated by entering the maximum temperature rise qd and the tangential grinding force F into equation (3). The measurement of F was made with a piezoelectric KISTLER dynamometer together with the measurement of temperature. The temperature was measured with the thermocouple technique (Fig.1) introduced by Peklenik [6] and improved by Gu and Wager [7] (both quantities measured through an A/ D card to a PC). Cutting conditions: v = 25 m/s, v = 4 m/min, grinding wheel A99 60LVS, p c ane plunge grinding, with and without cutting fluid (Emulzin 2 % concentration). Machined materials: difuzivnost 12,4.10-6 m2 podana v preglednici 2. /s. Kemična sestava je 1. 2. VT 9 titanium alloy - thermal diffusivity 2.87.10-6 m2/s, yield strength Rm = 900 MPa, after annealing. The structure of VT9 consists of a and b phase. Its chemical composition is given in Table 1. hardened roll-bearing (14 209.4) steel - thermal diffusivity 12,4.10-6 m2/s. Its chemical composition is given in Table 2. premazan vroči spoj kovine smeared metal - hot junction obdelovanec workpiece izolacija insulation krom-nikljev vodnik Cr-Ni wire conductor Sl. 1. Peklenikova metoda za merjenje temperature na stiku brusa in obdelovanca Fig.1 Peklenik method for the measurement of the temperature in the contact of the grinding wheel and the workpiece stran 559 Neslu{an M., Czán A, @uperl U.: Analiza porazdelitve toplote - Analysis of the Heat Distribution Preglednica 1. Kemična sestava titanove zlitine VT 9 Table 1. Chemical composition of the VT 9 titanium alloy element Al Mn Si Zr O2 N2 H2 C Fe % 5,8-7 2,8-3,8 0,2-0,3 0,8-2,5 <0,15 < 0,05 < 0,015 <0,1 < 0,25 Preglednica 2. Kemična sestava jekla za kotalne ležaje (14 209.4) Table 2. Chemical composition of the hardened roll-bearing (14 209.4) steel element % Cr Mn Si 1,3-1,6 0,9-1,2 0,3-0,6 < 0, 25 <0, 03 Cu S P Ni C < 0, 03 <0, 3 1 2 EKSPERIMENTALNI REZULTATI Temperaturo na površini 6> smo dobili tako, da smo dali gladko krivuljo skozi merjeno območje. Slika 3 kaže odnos med temperaturo površine in globino rezanja. Skupna toplota je ugotovljena tako, da smo izmerili obodno silo in hitrost koluta (sl. 4). 1200 oC 1000 800 600 400 200 0 2 EXPERIMENTAL RESULTS The temperature on the surface, qd, was obtained by putting a smooth curve through the measured trace. Figure 3 presents the relation between the surface temperature and the cutting depth. The total heat was determined by measuring the tangential force and the wheel speed (Figure 4). f\ f \ ' \ ^-v čas / time Sl. 2. Tipični izmerjeni dvig temperature pri brušenju titanove zlitine VT 9 (a = 0,03 mm) Fig.2. Typical measured temperature rise when grinding the VT 9 titanium alloy (ap = 0.03 mm) 1000 oC 800 /N 600 400 200 VT 9 EI 698 VD 14 209.4 0 a p 0,005 0,01 ------------> 0,015 0,02 0,025 0,03 mm 0,035 Sl. 3. Temperatura površine kaljenega jekla za kotalne ležaje 14 209.4 in titanove zlitine VT 9 Fig. 3. Surface temperature for the hardened roll-bearing 14 209.4 steel and the VT 9 titanium alloy 0 BnnBjfokJ][p)l]Olf|i[gO | | ^SSfiflMlGC | stran 560 0 Neslu{an M., Czán A, @uperl U.: Analiza porazdelitve toplote - Analysis of the Heat Distribution 4 3 190 J 170 150 130 110 90 70 50 30 10 -10 0,005 ap 0,01 0,015 0,02 0,025 0,03 mm 0,035 Sl. 4. Skupna toplota Q in obodna komponenta brusne sile F na 1 mm širine brušenja Fig. 4. Total heat, Q, and tangential component of grinding force, Fc, per 1mm of grinding width 100 % 90 80 70 60 50 40 30 20 10 0 14209.4 VT9 0 0,005 0,01 0,015 0,02 0,025 0,03 mm 0,035 Sl. 5. Razmerje porazdelitve Rw Fig. 5. Partition Ratio Rw Razmerje porazdelitvetf (sl. 5) je deležtoplote, ki vstopi v obdelovanec, proti celotni toploti, ki jo izračunamo tako, da vstavimo največji dvig temperature 0d s slike 3 in obodno silo brušenja F s slike 4 v enačbo (3). Pri postopku brušenja se skoraj vsa energija brušenja spremeni v toploto na majhnem območju brušenja. Pri suhem brušenju so trije pomembni toplotni ponori: obdelovanec, brus in odrezki. Največja mogoča toplota, ki vstopi v odrezke, se lahko izrazi z specifično odstranitvijo kovine, gostoto, specifično toplotno kapaciteto in razliko med temperaturo taljenja in temperaturo okolice [8]. Na temelju te predpostavke je največja toplota, ki vstopi v odrezke, približno 8 % pri 14 209.4 in približno 4,5 % pri titanovi zlitini. Velik del nastale toplote preide v obdelovanec, kar ima The partitioning ratio Rw (Figure 5) is the ratio of the heat entering the workpiece to the total heat, calculated by entering the maximum temperature rise, qd, from Figure 3 and the tangential grinding force, Fc, from Figure 4 into equation (3). In a grinding operation almost all the grinding energy is converted into heat within a small grinding zone. There are three significant heat sinks in dry grinding: the workpiece, the grinding wheel and the grinding chips. The maximum possible heat entering the grinding chips can be expressed in terms of the specific metal removal, the density, the specific heat capacity and the difference between the melting temperature and the ambient temperature [8]. On the basis of this assumption the maximum heat entering the grinding chips is about 8% for 14 209.4 and about 4.5% for the titanium alloy. A large part of the generated heat flows into the workpiece, which gfin^OtJJIMISCSD 02-10 stran 561 |^BSSITIMIGC 5 2 0 0 Neslu{an M., Czán A, @uperl U.: Analiza porazdelitve toplote - Analysis of the Heat Distribution za posledico skrajno visoke temperature na stiku med brusom in obdelovancem. Na podlagi eksperimentalnih rezultatov je mogoče trditi, da majhen delež energije vstopi v brus pri brušenju kaljenega jekla. Pri brušenju titanove zlitine v brus vstopi približni 65 % toplote. Velika mehanska in termična obremenitev zrn pri brušenju titanove zlitine vodi do velike obrabe zrn in močne adhezije med obdelovanim materialom in rezalnim zrnom [9]. Največji dvig temperature pri titanovi zlitini je mnogo večji kakor pri ležajnem jeklu, čeprav je čisti vnos energije pri titanovi zlitini manjši kakor pri kaljenem jeklu. To je zato, ker je toplotna prevodnost titanove zlitine mnogo manjša kakor pri kaljenem jeklu (koncentracija toplote na stiku brusa in obdelovanca pri brušenju titanove zlitine). Rezultati naslednjih preskusov kažejo, da uporaba diamantnih brusov in brusov CBN omogoča, da zmanjšamo nagnjenje k termičnim poškodbam brušenih površin na delih iz titanove zlitine VT 9. Temperature površine pri brusih CBN in diamantnih brusih, izmerjene z isto metodo, so znatno nižje od temperature površine, izmerjene pri Al O , in sicer predvsem pri uporabi hladilno mazalne tekočine (Emulzin H z 2-odstotno koncentracijo), pregl. 3. Nadalje, vrednosti porazdelitvenih razmerij so mnogo nižje pri brusih CBN in diamantnih brusih ter pri uporabi hladilno mazalne tekočine, pregl. 4. Titanova zlitina se oprime brusnih zrn in tako ustvari močno oviro za prenos toplote (predvsem pri uporabi brusov CBN in diamantnih brusov, zaradi njihove mnogo večje termične prevodnosti v primerjavi z brusom iz Al2O3). Hladilno mazalna tekočina ustvari film na brusnih zrnih in tako prepreči močno adhezijo titanove zlitine. results in extremely high temperatures at the interface between the wheel and the workpiece. On the basis of the experimental results it is possible to say that a small portion of energy enters the grinding wheel when grinding hardened steel. On the other hand, about 65% of the heat is entering the grinding wheel when grinding the titanium alloy. The high mechanical and thermal load of the grains when grinding the titanium alloy leads to a high grain-wear rate and strong adhesion between the machined material and the cutting grain [9]. The maximum temperature rise for the titanium alloy is much higher than that of the roll-bearing steel, although the net energy input for the titanium alloy is lower than for the hardened steel. This is because the thermal conductivity of the titanium alloy is much smaller than that of the hardened steel (the concentration of heat in the contact of the grinding wheel and the workpiece when grinding the titanium alloy). The results of the next experiments show that the use of diamond and CBN grinding wheels reduces the tendency to induce thermal damage to the ground surfaces of parts made from the VT 9 titanium alloy. The surface temperatures for the CBN and diamond grinding wheels, measured with the same technique, are significantly lower than those measured for Al2O3, primarily when applying cutting fluid (Emulzin H 2 % concentration), Table 3. Next, the values of the partitioning ratios are much lower with CBN and diamond grinding and the use of cutting fluid, Table 4. Titanium alloy adheres to the grinding grains and so creates a strong barrier against heat transfer (mainly when using CBN and diamond grinding wheels, because of their much higher thermal conductivity in comparison with an Al2O3 grinding wheel). The cutting fluid creates a film on the grinding grains and so eliminates the strong adhesion of titanium alloy. Preglednica 3. Vpliv hladilno mazalne tekočine (Emulzin H - 2 % koncentracijo) na temperaturo na stiku brusa in obdelovanca, v = 25 m/s, v = 4 m/min, a = 0,02 mm Table 3. The influence of cutting fluid (Emulzin H - 2 % concentration) on the temperature in the contact of the grinding wheel and the workpiece, v = 25 m/s, v = 4 m/min, a = 0.02 mm Al2O3 oC CBN oC Diamant / Diamond oC suho / dry Emulzin H suho / dry Emulzin H suho / dry Emulzin H 14 209.4 455 275 300 180 222 167 VT 9 695 580 610 235 340 180 Preglednica 4. Vpliv hladilno-mazalne tekočine (Emulzin H - 2 % koncentracijo) na razmerje porazdelitve RW, v = 25 m/s, v = 4 m/min, a = 0,02 mm Table 4. Influence of cutting fluid (Emulzin H - 2 % concentration) on the partitioning ratio R, v = 25 m/s, v = 4 m/min, a = 0.02 mm 14 209.4 VT 9 suho / dry Al2O3 % Emulzin H suho / dry CBN % Emulzin H 88 68 77 48 64 48 40 38 33 12 29 19 Diamant / Diamond % suho / dry Emulzin H 0 SšnrKitafcflM]! ma stran 562 Neslu{an M., Czán A, @uperl U.: Analiza porazdelitve toplote - Analysis of the Heat Distribution 400 MPa 300 200 100 0 -100 -200 0,2 0,22 mm Sl. 6. Zaostale napetosti po brušenju titanove zlitine VT 9 brez uporabe hladilno mazalne tekočine, v = 25 m/s, v = 4 m/min, a = 0,02 mm Fig. 6. Residual stresses after grinding the VT 9 titanium alloy without cutting fluid, vc = 25 m/s, vw = 4 m/min, ap = 0.02 mm 400 -MPa 300 0 0,02 0,04 0,06 0,08 0,1 0,12 0,14 0,16 0,18 0,2 0,22 mm 200 100 0 - -100 -200 -300 -400 -500 -600 Sl. 7. Zaostale napetosti po brušenju titanove zlitine VT 9 z uporabo hladilno mazalne tekočine (Emulzin H - 2 % koncentracijo), v = 25 m/s, v = 4 m/min, a = 0,02 mm Fig. 7. Residual stresses after grinding the VT 9 titanium alloy with cutting fluid (Emulzin H - 2 % concentration), v = 25 m/s, v = 4 m/min, a = 0.02 mm povrina pod slojem Zmanjšanje termične obremenitve brušenega dela znatno vpliva na njegovo kakovost, ki jo predstavljajo zaostale napetosti (sl. 6 in 7). Rezultati merjenja zaostalih napetosti kažejo, da obstaja močna zveza med razmerjem porazdelitve R in zaostalimi napetostmi. Tlačne zaostale napetosti so postale bolj verjetne pri nižjih vrednostih razmerja porazdelitve R (manjši delež energije vstopi v obdelovanec). Tako brušenje titanove zlitine VT 9 z brusi CBN in diamantnimi brusi ter z uporabo hladilno-mazalne tekočine omogoča, da dosežemo sprejemljive zaostale napetosti. Po drugi strani pa visoki stroški brusov CBN in diamantnih brusov omejujejo njihovo uporabo. Čeprav temperatura površine ne sme presegati delovne temperature, pri delih iz titanovih zlitin, lahko imajo natezne zaostale napetosti, ki jih povzroči ta temperatura, za posledico znatno nižjo utrujenostno trdnost zaradi poškodb površine. Reducing the thermal load on the ground part significantly influences their quality, represented by residual stresses, Fig. 6 and Fig. 7. Results of the measurement of residual stresses show that there is a strong correlation between the partition ratio, Rw, and the residual stresses. Compressive residual stresses become more likely with lower values of partition ratio (smaller proportion of the energy entering the workpiece). And so CBN and diamond grinding of the VT 9 titanium alloy with cutting fluid enables us to achieve acceptable residual stresses. On the other hand, the high costs of CBN and diamond grinding wheels limit their application. Even though the surface temperature must not exceed the working temperature for the parts made of titanium alloys, the tensile residual stresses induced at this temperature can result in an appreciably lower fatigue strength due to the surface damage. Neslu{an M., Czán A, @uperl U.: Analiza porazdelitve toplote - Analysis of the Heat Distribution Zaradi tega se dandanes nagibamo k temu, da se vključi dodaten postopek mehanskega utrjevanja brušenih površin pri vseh delih v letalski in vesoljski industriji. ZAHVALE Avtorji se želijo zahvaliti za finančno podporo, ki jo je dala VEGA za ta projekt (projekt št. 1/9406/02), in je bil vključen v raziskovalni program na Oddelku za proizvodno strojništvo Univerze v Žilini. For these reasons there is a current tendency to include an additional operation of mechanically hardening the ground surfaces of all the parts made for the aerospace and space industries. ACKNOWLEDGEMENTS The authors would like to acknowledge the financial support provided by VEGA for this project (project n.1/9406/02), which is included in the research programme at the Department of Technological Engineering of the University of Žilina. 3 LITERATURA 3 REFERENCES [I] Zlatin, N., M. Field (1973) Procedures and precautions in machining titanium alloys, Titanium Science and Technology, 1,489-504. [2] Kahles, J.F, M. Field, E. Eylon, FH. Froes (1985) Machining of titanium alloys, Journal of Metals, IV, 27 - 35. [3] Rowe, W.B., S.C. Black, B. Mills, H.S. Qi, M.N. Morgan (1995) Experimental investigation of heat transfer in grinding, CIRP 44/1, 329-332. [4] Kato, T, H. Fujii (1999) Energy partition in conventional surface grinding, Journal of Manufacturing Science and Engineering 121, 393-398. [5] Jeager, J.C. (1942) Moving source of heat and the temperature at sliding contact, Proc. of the Royal Society of New South Wales, 76, 203-224. [6] Peklenik, J. (1957) Ermittlung von geometrischen and physikalischen Kenngrossen fiir die Grundlagenforschung des Schleifens, PhD. Thesis, Aachen. [7] Gu, DY., J.G Wager (1988) New evidence on the contact zone in grinding, CIRP 37/1/, 335-338. [8] Rowe, W.B., J.A. Pettit, A. Boyle, J.L. Moruzzi (1988) Avoidance of thermal damage in grinding and prediction of the damage threshold, CIRP 37/1, 327-330. [9] Vasilko, K., G. Bokučava (1988) Brusenie kovovych materialov, ALFA Bratislava. [10] Darecky, J., S. Novak (1998) Silove atepelne zafaženie nastroja pri obrabani Ni-zliatiny EP 742 VD. Materidlove inžinierstvo 12, ŽU Žilina. [II] Branesky L., J. Zajac (1997) Rezne kvapaliny vo vyrobe ložisk a ostatnych strojarenskych technologiach, Strojdrenskd technologia a valive ložiskd 97, Žilina, 46. Naslova avtorjev: dr. Miroslav Neslušan dr. Andrej Czan Oddelek za proizvodno strojništvo Univerza v Žilini Vefkydiel 010 26 Žilina, Slovaška miroslav_neslusan@kti.utc.sk Authors’ Addresses: Dr. Miroslav Neslušan Dr. Andrej Czan Dept. of Technological Eng. University of Žilina Vefkydiel 010 26 Žilina, Slovak Republic miroslav_neslusan@kti.utc.sk mag. Uroš Župerl Univerza v Mariboru Fakulteta za strojništvo Smetanova 17 2000 Maribor uros.zuperl@uni-mb.si Mag. Uroš Župerl University of Maribor Faculty of Mechanical Eng. Smetanova 17 2000 Maribor, Slovenia uros.zuperl@uni-mb.si Prejeto: 29.1.2002 Received: Sprejeto: 22.11.2002 Accepted: 0 SšnrKitafcflM]! ma stran 564 © Strojni{ki vestnik 48(2002)10,565-566 ISSN 0039-2480 Osebne vesti Osebne vesti © Journal of Mechanical Engineering 48(2002)10,565-566 ISSN 0039-2480 Personal Events Personal Events Zoisova nagrada Zoisovo nagrado za vrhunske znanstvene dosežke na področju strojništva je prejel Prof.dr. Jože Vižintin Jože Vižintin, redni profesor na Fakulteti za strojništvo Univerze v Ljubljani, je vodilni slovenski strokovnjak na področju tribologije. Z dolgoletnim znanstvenoraziskovalnim, razvojnim in strokovnim delom si je pridobil velik ugled doma in v tujini. Njegove raziskave so posvečene predvsem vprašanjem utrujanja materiala pri majhnih amplitudah in velikih frekvencah ter vprašanjem uporabe trdih prevlek za strojne elemente. Na teh področjih je profesor Vižintin skupaj s sodelavci v zadnjih sedmih letih objavil 51 izvirnih znanstvenih del, od tega 31 v revijah, ki jih citira SCI, in 20 v drugih revijah, ki jih priznava stroka kot pomembne. O mednarodni odmevnosti njegovih del pričajo citati v bazi SCI. Najodmevnejše rezultate je profesor Vižintin s sodelavci dosegel pri določanju trenutne temperature v tornem stiku. Dokazal je, da te temperature dosegajo 1000 stopinj Celzija in več in so določujoče za nastanek poškodb. Pravilnost te ugotovitve, ki je bila v nasprotju s splošnim prepričanjem, da trenutna temperatura v tornih stikih ne presega 100 stopinj Celzija, so potrdili zadnji citati tujih raziskovalcev. Značilno za profesorja Vižintina je, da skrbi tudi za prenos svojih temeljnih in uporabnih raziskav v prakso, predvsem z razvojem novih izdelkov za industrijo. V zadnjih sedmih letih ima dva patenta v Sloveniji in dve patentni prijavi v ZDA. V raziskovalno delo vključuje mlade raziskovalce in sodelavce iz drugih ustanov ter s sodelovanjem s tujimi ustanovami uveljavlja slovensko znanje. Med drugim je ustanovil prvi Tribološki laboratorij v Sloveniji, ki je pozneje prerasel v Center za tribologijo in tehnično diagnostiko. Pomemben je bil njegov prispevek pri ustanovitvi Evropskega virtualnega tribološkega inštituta. Profesor Vižintin je celovita osebnost, ki je z izvirnimi raziskovalnimi dosežki prispeval k razvoju tribologije v svetovnem merilu, obenem pa je s svojim razvojnim in strokovnim delom odločilno vplival na razvoj te stroke v Sloveniji. Doktorati, magisteriji, specializacije, diplome DOKTORATI Na Fakulteti za strojništvo Univerze v Ljubljani sta z uspehom zagovarjala svoji doktorski disertaciji,: dne 29. oktobra 2002: mag. Simon Strgar, z naslovom “Optodinamski opis in novi načini laserskega označevanja” in mag. Marjan Gantar, z naslovom “Tokovne razmere v stranskih prostorih rotorjev pri hidravličnih turbostrojih in njihov vpliv na aksialne obremenitve”. S tem sta navedena kandidata dosegla akademsko stopnjo doktorja tehničnih znanosti. MAGISTERIJI Na Fakulteti za strojništvo Univerze v Mariboru je dne 10. oktobra 2002 Zvonko Kremljak z uspehom zagovarjal svoje magistrsko delo z naslovom: “Povezava livarskega in obdelovalnega sistema s povečanimi sinergijskimi učinki”. S tem je navedeni kandidat dosegel akademsko stopnjo magistra tehničnih znanosti. SPECIALIZACIJE Na Fakulteti za strojništvo Univerze v Mariboru sta z uspehom zagovarjala svoji specialistični deli: dne 11. oktobra 2002: Jernej Tahirovic, z naslovom “Načrtovanje in vodenje zagotavljanja nemotene proizvodnje” in Rolando Koren, z naslovom “Humanizacija dela na liniji sestave vrat hladilnih naprav”. S tem sta navedena kandidata dosegla akademsko stopnjo specialista. DIPLOMIRALI SO Na Fakulteti za strojništvo Univerze v Ljubljani so pridobili naziv univerzitetni diplomirani inženir strojništva: gfin^OtJJlMISCSD 02-10 stran 565 |^BSSITIMIGC Strojni{ki vestnik - Journal of Mechanical Engineering dne 1. oktobra 2002: Martin DEŽELAK, Mihael DOBNIKAR, Boštjan GUŠTIN, Andrej PUNGERČIČ in Primož ŽAGAR. * Na Fakulteti za strojništvo Univerze v Ljubljani so pridobili naziv diplomirani inženir strojništva: dne 10. oktobra 2002: Roman KIRN, Breda LUKANEC, Boštjan PERDAN, Jurij REPIČ in Blaž WEBER dne 11. oktobra 2002: Štefan ANČIMER, Damjan GLINŠEK, Gregor ISTENIČ, Andrej JEJČIČ, Tomaž MEDVED, Alojzij PRAH, Sebastjan STERNAD in Marjan ŽULIČ; dne 14. oktobra 2002: Gregor ANDROJNA, Iztok ČUFER Primož GOSTINČAR Tomaž MUNIH, Andreja PENKO, Janez ZUPAN in Samo ŽVEGLA. Na Fakulteti za strojništvo Univerze v Mariboru je pridobil naziv diplomirani inženir strojništva: dne 24. oktobra 2002: Igor SVEČKO. 0 BnnBjfokJ][p)l]Olf|i[gO | | ^SSfiFlMlGC | stran 566 © Strojni{ki vestnik 48(2002)10,567-568 ISSN 0039-2480 Navodila avtorjem © Journal of Mechanical Engineering 48(2002)10,567-568 ISSN 0039-2480 Instructions for Authors Navodila avtorjem Instructions for Authors Članki morajo vsebovati: - naslov, povzetek, besedilo članka in podnaslove slik v slovenskem in angleškem jeziku, - dvojezične preglednice in slike (diagrami, risbe ali fotografije), - seznam literature in - podatke o avtorjih. Strojniški vestnik izhaja od leta 1992 v dveh jezikih, tj. v slovenščini in angleščini, zato je obvezen prevod v angleščino. Obe besedili morata biti strokovno in jezikovno med seboj usklajeni. Članki naj bodo kratki in naj obsegajo približno 8 tipkanih strani. 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The Abstract should state the principal objectives and the scope of the investigation, the methodology employed, summarize the results and state the principal conclusions. - An Introduction, which should provide a review of recent literature and sufficient background information to allow the results of the paper to be understood and evaluated. - A Theory - An Experimental section, which should provide details of the experimental set-up and the methods used for obtaining the results. - A Results section, which should clearly and concisely present the data using figures and tables where appropriate. - A Discussion section, which should describe the relationships and generalisations shown by the results and discuss the significance of the results making comparisons with previously published work. (Because of the nature of some studies it may be appropriate to combine the Results and Discussion sections into a single section to improve the clarity and make it easier for the reader.) - Conclusions, which should present one or more conclusions that have been drawn from the results and subsequent discussion. - References, which must be numbered consecutively in the text using square brackets [1] and collected together in a reference list at the end of the paper. Any footnotes should be indicated by the use of a superscript1. The layout of the text Texts should be written in A4 format, with double spacing and margins of 3 cm to provide editors with space to write in their corrections. Microsoft Word for Windows is the preferred format for submission. One hard copy, including all figures, tables and illustrations and an identical electronic version of the manuscript must be submitted simultaneously. Please do not use a LaTeX text editor, since this is not compatible with the publishing procedure of the Journal of Mechanical Engineering. Graphs, tables and equations in LaTeX may be supplied in good quality hard-copy format, so that they can be copied for inclusion in the Journal. Equations should be on a separate line in the main body of the text and marked on the right-hand side of the page with numbers in round brackets. Units and abbreviations Only standard SI symbols and abbreviations should be used in the text, tables and figures. Symbols for physical quantities in the text should be written in Italics (e.g. v, T, n , etc.). Symbols for units that consist of letters should be in plain text (e.g. ms-1, K, min, mm, etc.). All abbreviations should be spelt out in full on first appearance, e.g., variable time geometry (VTG). stran 567 Strojni{ki vestnik - Journal of Mechanical Engineering Slike Slike morajo biti zaporedno oštevilčene in označene, v besedilu in podnaslovu, kot sl. 1, sl. 2 itn. Posnete naj bodo v kateremkoli od razširjenih formatov, npr. BMP, JPG, GIF. Za pripravo diagramov in risb priporočamo CDR format (CorelDraw), saj so slike v njem vektorske in jih lahko pri končni obdelavi preprosto povečujemo ali pomanjšujemo. Pri označevanju osi v diagramih, kadar je le mogoče, uporabite označbe veličin (npr. t, v, m itn.), da ni potrebno dvojezično označevanje. V diagramih z več krivuljami, mora biti vsaka krivulja označena. Pomen oznake mora biti pojasnjen v podnapisu slike. Vse označbe na slikah morajo biti dvojezične. Za vse slike po fotografskih posnetkih je treba priložiti izvirne fotografije ali kakovostno narejen posnetek. V izjemnih primerih so lahko slike tudi barvne. Preglednice Preglednice morajo biti zaporedno oštevilčene in označene, v besedilu in podnaslovu, kot preglednica 1, preglednica 2 itn. V preglednicah ne uporabljajte izpisanih imen veličin, ampak samo ustrezne simbole, da se izognemo dvojezični podvojitvi imen. K fizikalnim veličinam, npr. t (pisano poševno), pripišite enote (pisano pokončno) v novo vrsto brez oklepajev. Vsi podnaslovi preglednic morajo biti dvojezični. Seznam literature Vsa literatura mora biti navedena v seznamu na koncu članka v prikazani obliki po vrsti za revije, zbornike in knjige: [1] Tarng, Y.S., Y.S. Wang (1994) A new adaptive controler for constant turning force. Int J Adv Manuf Technol 9(1994) London, pp. 211-216. [2] Čuš, F., J. Balič (1996) Rationale Gestaltung der organisatorischen Ablaufe im Werkzeugwesen. Proceedings of International Conference on Computer Integration Manufacturing Zakopane, 14.-17. maj 1996. [3] Oertli, PC. (1977) Praktische Wirtschaftskybernetik. Carl Hanser Verlag Minchen. Podatki o avtorjih Članku priložite tudi podatke o avtorjih: imena, nazive, popolne poštne naslove, številke telefona in faksa ter naslove elektronske pošte. Sprejem člankov in avtorske pravice Uredništvo Strojniškega vestnika si pridržuje pravico do odločanja o sprejemu članka za objavo, strokovno oceno recenzentov in morebitnem predlogu za krajšanje ali izpopolnitev ter terminološke in jezikovne korekture. Avtor mora predložiti pisno izjavo, da je besedilo njegovo izvirno delo in ni bilo v dani obliki še nikjer objavljeno. Z objavo preidejo avtorske pravice na Strojniški vestnik. Pri morebitnih kasnejših objavah mora biti SV naveden kot vir. Rokopisi člankov ostanejo v arhivu SV Vsa nadaljnja pojasnila daje: Uredništvo STROJNIŠKEGA VESTNIKA p.p. 197/IV 1001 Ljubljana Telefon: (01) 4771-757 Telefaks: (01) 2518-567 E-mail: strojniski.vestnik@fs.uni-lj.si Figures Figures must be cited in consecutive numerical order in the text and referred to in both the text and the caption as Fig. 1, Fig. 2, etc. Figures may be saved in any common format, e.g. BMP, GIF, JPG. However, the use of CDR format (CorelDraw) is recommended for graphs and line drawings, since vector images can be easily reduced or enlarged during final processing of the paper. When labelling axes, physical quantities, e.g. t, v, m, etc. should be used whenever possible to minimise the need to label the axes in two languages. Multi-curve graphs should have individual curves marked with a symbol, the meaning of the symbol should be explained in the figure caption. All figure captions must be bilingual. Good quality black-and-white photographs or scanned images should be supplied for illustrations. In certain circumstances, colour figures may be considered. Tables Tables must be cited in consecutive numerical order in the text and referred to in both the text and the caption as Table 1, Table 2, etc. The use of names for quantities in tables should be avoided if possible: corresponding symbols are preferred to minimise the need to use both Slovenian and English names. In addition to the physical quantity, e.g. t (in Italics), units (normal text), should be added in new line without brackets. All table captions must be bilingual. The list of references References should be collected at the end of the paper in the following styles for journals, proceedings and books, respectively: [1] Tarng, Y.S., Y.S. Wang (1994) A new adaptive controler for constant turning force. Int J Adv Manuf Technol 9(1994) London, pp. 211-216. [2] Čuš, F., J. Balič (1996) Rationale Gestaltung der organisatorischen Ablaufe im Werkzeugwesen. Proceedings of International Conference on Computer Integration Manufacturing Zakopane, 14.-17. maj 1996. [3] Oertli, PC. (1977) Praktische Wirtschaftskybernetik. Carl Hanser Verlag Minchen. Author information The following information about the authors should be enclosed with the paper: names, complete postal addresses, telephone and fax numbers and E-mail addresses. Acceptance of papers and copyright The Editorial Committee of the Journal of Mechanical Engineering reserves the right to decide whether a paper is acceptable for publication, obtain professional reviews for submitted papers, and if necessary, require changes to the content, length or language. Authors must also enclose a written statement that the paper is original unpublished work, and not under consideration for publication elsewhere. On publication, copyright for the paper shall pass to the Journal of Mechanical Engineering. The JME must be stated as a source in all later publications. Papers will be kept in the archives of the JME. You can obtain further information from: Editorial Board of the JOURNAL OF MECHANICAL ENGINEERING P.O.Box 197/IV 1001 Ljubljana, Slovenia Telephone: +386 (0)1 4771-757 Fax: +386 (0)1 2518-567 E-mail: strojniski.vestnik@fs.uni-lj.si 0 &nnBjfokJ][p)l]Olf|i[gO | | ^SSfiflMlGC | stran 568