Numerical Simulation Of Three-dimension Unsteady Flow In The Compression Chambers Of A Scroll Compressor

Transcription

1 Prde Unversy Prde e-pbs Inernaonal omressor Engneerng onference Scool of Mecancal Engneerng 2014 Nmercal Smlaon Of Tree-dmenson Unseady Flow In Te omresson ambers Of A Scroll omressor Sangla L omressor and Moor Inse of Gree Elecrc Alances, Inc. of Za, na, Peole's Reblc of, sangla89@163.com Xaol Kang omressor and Moor Inse of Gree Elecrc Alances, Inc. of Za, na, Peole's Reblc of aa San omressor and Moor Inse of Gree Elecrc Alances, Inc. of Za, na, Peole's Reblc of Yseng H omressor and Moor Inse of Gree Elecrc Alances, Inc. of Za, na, Peole's Reblc of Follow s and addonal wors a: ://docs.lb.rde.ed/cec L, Sangla; Kang, Xaol; San, aa; and H, Yseng, "Nmercal Smlaon Of Tree-dmenson Unseady Flow In Te omresson ambers Of A Scroll omressor" (2014). Inernaonal omressor Engneerng onference. Paer ://docs.lb.rde.ed/cec/2277 Ts docmen as been made avalable rog Prde e-pbs, a servce of e Prde Unversy Lbrares. Please conac ebs@rde.ed for addonal nformaon. omlee roceedngs may be acqred n rn and on D-ROM drecly from e Ray W. Herrc Laboraores a s://engneerng.rde.ed/ Herrc/Evens/orderl.ml

2 1200, Page 1 Nmercal Smlaon of Tree-dmenson Unseady Flow n e omresson ambers of a Scroll omressor Sangla L, Xaol Kang, aa San, Yseng H omressor and Moor Inse of Gree Elecrc Alances, Inc. of Za, Jn Wes Rd., Za y, , P. R. na Pone: , Fa: , E-mal: sangla89@163.com ABSTRAT De o e movemen of orbng scroll and leaage n scroll comressor cambers, e nseady flow as sgnfcan nflence on comresson rocess. I's necessary o aes accon of bo flow and ermodynamcs rocess n analyss of comresson. Ts aer as carred o a nmercal smlaon of e wole comresson rocess n scroll comressor, nvolvng scon, comresson and dscarge rocess. By solvng mass, momenm and energy eqaons of e refrgeran, e velocy, ressre and emerare dsrbon n all comresson cambers rogo e enre comresson cycle as been obaned, wc aes accon of all e nflence of flow and ermodynamcs rocess. Te feld qanes ave sown nonnform dsrbon n every comresson camber, and leaage beween dfferen cambers s obvos. Frer, e overall arameers, sc as mass flow rae and comresson ower consmon, ave been calclaed from e feld qanes. Te general comarsons beween nmercal and eermenal resls sow a reasonable good agreemen. Te researc s sefl for e omal desgn of e comressor geomerc srcre. 1. INTRODUTION Energy-savng and envronmen roecon becomes e mos seros roblem n recen days. Te scroll comressor, as a osve dslacemen macne w g effcency and less nose, s very olar and wdely sed n arcondonng and refrgeraon ndsry. W e ncreasng need of develong more effcen and relable scroll comressor, reqres more effor o sdy e deals of scroll comressor. In scroll comressor, several crescen-saed cambers ave been solaed by delcae desgned orbng scroll wra and fed scroll wra. W e movemen of orbng scroll, e comresson camber from osde of e scroll s gradally sqeezed owards dscarge camber and e refrgeran s comressed. Drng e comresson rocess, e flow feld n worng camber connes o move and deform, wc soldn be negleced n mos saon of analyss. B e comresson rocess s so comle a sll oses a grea callenge for nmercal smlaon of e nseady, ree-dmensonal, comressble flow n a scroll comressor. To smlfy e roblem, e flow and ea ransfer cold be comed sng one-dmensonal flow models w varos emrcal correlaons (en,2002 and Wnandy,2002). However, ese emrcal correlaons are sally no sable well for dfferen srcre and oerang condon, and one-dmensonal flow models only focs on e averaged qanes n worng camber. Te deals of flow and ea ransfer can no be resened, and also s dffcl o carry o e frer analyss, sc as force and ermal deformaon. In s aer, a nmercal smlaon as been develoed o sdy e wole comresson rocess n scroll comressor. Te real movemen and sae deformaon of e worng camber as been realzed w e movng mes meod rovded by commercal FD sofware. Ts researc s eeced o rovde a descron and analyss of feld qanes wn e scroll comressor, wc cold be sefl for e frer omal desgn of e comressor geomerc srcre. 22 nd Inernaonal omressor Engneerng onference a Prde, Jly 14-17, 2014

3 1200, Page 2 2. PHYSIAL MODEL OF SROLL OMPRESSOR Fgre 1 sows e confgraon of e scroll comressor. Te refrgeran flows no e comressor rog e scon or. And en, w e movemen of orbng scroll wc s drven by e cran saf, e refrgeran s comressed. Afer e comresson rocess s over, e refrgeran s dscarged no comressor sell rog e dscarge or of e fed scroll. Te comresson rocess s demonsraed n Fgre 2. From oer erery o cener, ere are ree ars of camber, e scon, frs, second gas camber and one dscarge camber. I aes wo orbng cycles from e gas oces fnsng scon o e refrgeran dscarged. Te sarng se 0 s defned as e momen wen e oermos cambers are sealed off. As refrgeran moves owards e cener, e comresson cambers conne deformng and movng, and e raed gas s comressed. Te dscarge se begns a abo 482, wle e comresson cambers reac e cener of e scrolls and e of orbng scroll s nable o cover e dscarge or of e fed scroll. Te dscarge rocess wll conne o ne cycle. Te man geomerc and oerang arameers of e scroll comressor sded n s aer are resened n Table 1. Fgre 1: Geomery of scroll comressor Fgre 2: omresson rocess 22 nd Inernaonal omressor Engneerng onference a Prde, Jly 14-17, 2014

4 1200, Page 3 22 nd Inernaonal omressor Engneerng onference a Prde, Jly 14-17, 2014 Table 1: Man arameers of scroll comressor arameer Vale Dslacemen volme [cm³] 55 Wra cness [mm] 4 Wra Heg[mm] 27.3 Nomnal seed [rm] Refrgeran R410a Evaorang emerare [º] 7.2 ondensng Temerare [º] 54.4 Scon Temerare [º] NUMERIAL SIMULATION PRORDURE Wen e refrgeran flows no e worng camber, sows srong ransen enomena w e scroll orbng. Te ressre, densy and emerare of e refrgeran sgnfcan cange as e volme of worng camber decreases. Te governng eqaons are me deendan and nvolvng mass, momenm and energy conservaon eqaons. Te mass and momenm eqaons for ransen comressble fld flows, as nown as e Naver- Soes eqaons, can be eressed n aresan ensor noaon (Wars, 1981): 0 (1) s (2) Hea ransfer s solved rog e followng general form of e enaly conservaon eqaon (Jones, 1980): eff s c (3) Te sandard -ε model s sed o solve e rblen flow. Transor eqaons for rblence nec energy and dssaon rae are as follows (El Tary, 1983) NL P g s 3 2 1, (4) NL B P P P (5) Te comaonal doman ncldes e scon or, worng cambers and dscarge or. A Srcred mes s generaed for e flow feld, and e oal mes as abo 300,000 eaedral elemens. A movng mes meod s sed o regenerae e mes for e doman nvolvng scrolls a every me se. In comaonal model, e aal clearance of scroll s negleced, b e radal clearance s reserved. And e flow feld s only occed by refrgeran, wo lbrcang ol consdered. Te ressre bondary condon s aled on nle and ole, wc s eqal o 0.997MPa (evaorang emerare 7.2 º ) and 3.36MPa (condensng emerare 54.4º ) resecvely. Te nle as consan scon emerare of 18.3 º. Te scroll wra s consdered as smoo no-sl and adabac wall. Te varyng velocy bondary s mosed on orbng scroll wra, accordng o e roaonal seed of e cran saf.

5 1200, Page 4 Governng eqaons are dsersed sng fne volme meod (FVM) and algebrac eqaons are solved by PISO algorm. Te solon s consdered as convergence wen normalzed absole resdal sm over all cells n e comaonal doman s redced o 10 3 and 10 2 for ressre and oer varables a every me se, resecvely. Te ermodynamc and ransor roeres of R410A are calclaed by REFPROP 9.0 wc s develoed by Naonal Inse of Sandards and Tecnology (NIST, USA). Fgre 3: Mes for comaonal doman 4. RESULTS VALIDATION AND DISUSSIONS 4.1 Resls valdaon An eermen es as been carred o nder e oerang condon sown n Table 1. Te nmercal and eermen resls abo mass flow rae and senroc effcency ave been comared o valdae e nmercal smlaon. Te senroc effcency η can be defned as follow w s n ds, s (6) wc n ds, ac Were W s s senroc comresson ower, W c s acal comresson ower, n s secfc enaly of nle, ds,s s senroc secfc enaly of dscarge gas, ds,ac s acal secfc enaly of dscarge gas. In nmercal smlaon, e comresson ower W c s drecly obaned from e wor a s done by gas ressre on e orbng scroll. Fgre 4 sows e comared resls wle e scroll comressor rnnng a dfferen roaonal seed. Te nmercal resls of mass flow rae are slgly ger an eermen, and e mos devaon s lower an 3.2%. Te dfferences beween nmercal and eermen resls abo senroc effcency are less an 3.5%, as sown n Fgre 4(b). Fgre 4: omarson of eermen and smlaon: (a) mass flow rae, (b) senroc effcency 22 nd Inernaonal omressor Engneerng onference a Prde, Jly 14-17, 2014

6 1200, Page Flow caracersc n worng cambers Fgre 5 sows e overall caracerscs of e flow feld. Alog eac ar of worng camber resens a general symmerc flow, e slgly dfference sll cold be fond n some ars of e flow feld. Te leaage s sgnfcan n comresson camber and e ressre dfference cases gas flow no downsream camber wle oer gas flow from sream camber. From oer o e cener of scroll wra, e ressre and emerare ncrease gradally. Fgre 5: Overall caracersc of e flow feld: (a) velocy, (b) ressre, (c) emerare Te velocy, ressre and emerare dsrbon n one worng camber from nal se θ=0 o se θ=360 are sown n Fgre 6-8. W e movemen of e worng camber, e refrgeran flows from oer corner o nner corner of e crescen camber and e velocy fnally decreases meanwle. Also, e leaage flow s fond n bo corners of e camber, and seems more sgnfcan as e camber s aroacng e cener of nvole. Te movemen of scroll wra and e leaage beween cambers ave moran nflence on e flow fled. Te ressre and emerare along camber bo sow nonnform dsrbon. I sold been noed a e ressre of e camber a nal se θ=0 s acally ger an scon ressre, wc means e refrgeran s already slgly comressed before e comresson se sars de o e orbng of scroll. And s feare of recomresson resls a slgly ger volmerc effcency an eorecal analyss cold be fond n scroll comressor f e leaage s small enog o be negleced. As sown n Fgre 8, e leaage as sgnfcan nflence on emerare dsrbon, and condces o more nonnform enomenon an ressre dsrbon, esecally a e of camber. Fgre 6: Velocy of e worng camber 22 nd Inernaonal omressor Engneerng onference a Prde, Jly 14-17, 2014

7 1200, Page 6 Fgre 7: Pressre of e worng camber Fgre 8: Temerare of e worng camber 4.3 Gas forces on orbng scroll Several forces and momen are acng on orbng scroll drng e comresson. As seen n Fgre 9, e gas forces manly conss of aal, radal and angenal force. Te orzonal forces, ncldng radal and angenal force, case e overrnng momen. Tese forces ave a very moran nflence on e frcon loss and e relably of e scroll comressor. Te overrnng momen rases a rend of ng e orbng scroll and ncreases e clearance beween scrolls, wc cold resl n more frcon and leaage loss n scroll comressor. Fgre 9: Illsraon of gas forces on orbng scroll 22 nd Inernaonal omressor Engneerng onference a Prde, Jly 14-17, 2014

8 1200, Page 7 Fgre 10 sows e forces and overrnng momen crves acng on orbng scroll n wo orbng cycles. Obvosly, all crves erodcally cange w e roaon of cran saf. Te aal and angenal force frs ncrease as e comresson rocess connes, and ey reac e ea a abo θ=210 n every orbng cycle. Te nder-comresson rocess acally occrs n comressor a crren oerang condons. I means e ressre of second comresson camber s lower an dscarge ressre wen comresson se s endng, and afer a e second comresson camber s merged no dscarge camber. Ts, e comresson sll connes nl dscarge camber aceves ermnal ressre a e begnnng of dscarge se. Once dscarge camber reaces e fnal ressre, as dscarge rocess connes, e aal and angenal force begns o decrease. Also, as s seen, e angenal and radal force flcaes radly, wereas e aal force s more le a smoo crve. In radonal analyss, nform ressre dsrbon s assmed n comresson camber. Te angenal and radal force need only consder e gas ressre acng on some ars of scroll as sown n Fgre 9, wle e ressre of res ars can be elmnaed w eac oer. However, ressre dsrbon as sgnfcan dfference n e comresson camber, as dscssed above. As e orbng scroll moves, e varey of ressre dsrbon cases e flcaon of angenal and radal force. Te overrnng momen bascally deends on angenal force, wc as e smlar feare w angenal force as seen n Fgre 10(b). Fgre 10: Gas forces and momen: (a) aal, radal and angenal force, (b) overrnng momen 5. ONLUSION A nmercal smlaon as been develoed o sdy e nseady ree-dmensonal comressble flow n scroll comressor. By solvng mass, momenm and energy eqaons of e refrgeran, e velocy, ressre and emerare dsrbon n all comresson cambers rogo e enre comresson cycle as been obaned. Te nmercal and eermen resls abo mass flow rae and senroc effcency sow a reasonable good agreemen. Te nmercal resls of mass flow rae are slgly ger an eermen, and e mos devaon s lower an 3.2%. Te dfferences beween nmercal and eermen resls abo senroc effcency are less an 3.5%. Te feld qanes ave sown nonnform dsrbon n comresson camber, wc s manly cased by e movemen and leaage. Te leaage flow s sgnfcan n comresson camber, esecally as e camber s aroacng e cener of nvole. De o e orbng of scroll, e refrgeran s already slgly comressed before e comresson se sars. Te aal, radal and angenal forces on orbng scroll erodcally cange w e roaon of cran saf, and e nonnform dsrbon of ressre cases e flcaon of angenal and radal force. 22 nd Inernaonal omressor Engneerng onference a Prde, Jly 14-17, 2014

9 1200, Page 8 REFERENES en, Y., Halm, N. P., Groll, E. A., and Bran, J. E., Maemacal Modelng of Scroll omressors. Par I: omresson Process Modelng. Inernaonal Jornal of Refrgeraon, vol. 25: Wnandy, E. L., and Lebrn J., Scroll comressors sng gas and lqd necon: eermenal analyss and modelng. Inernaonal Jornal of Refrgeraon, vol. 25: Wars, Z.V.A., onservaon form of e Naver-Soes eqaons n general nonseady coordnaes. AIAA, Jornal, vol.19: Jones, W. P., Predcon meods for rblen flames. Hemsere, Wasngon, D.., El Tary, S. H., ε eqaon for comressble recrocang engne flows. AIAA, J. Energy, vol.7, no.4: nd Inernaonal omressor Engneerng onference a Prde, Jly 14-17, 2014