Modeling and Experimental Investigation on the Internal Leakage in a CO2 Rotary Vane Expander

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1 urdu Univrsiy urdu -ubs Inrnaional Comprssor Enginring Confrnc School of chanical Enginring 2008 odling and Exprimnal Invsigaion on h Inrnal Lakag in a CO2 Roary Van Expandr Bingchun Yang Xi an Jiaoong Univrsiy Shaoyi Sun Xi an Jiaoong Univrsiy Xuyuan ng Xi an Jiaoong Univrsiy Bi Guo Xi an Jiaoong Univrsiy Ziwn Xing Xi an Jiaoong Univrsiy Follow his and addiional works a: hps://docs.lib.purdu.du/icc Yang, Bingchun; Sun, Shaoyi; ng, Xuyuan; Guo, Bi; and Xing, Ziwn, "odling and Exprimnal Invsigaion on h Inrnal Lakag in a CO2 Roary Van Expandr" (2008). Inrnaional Comprssor Enginring Confrnc. apr hps://docs.lib.purdu.du/icc/1852 This documn has bn mad availabl hrough urdu -ubs, a srvic of h urdu Univrsiy Libraris. las conac pubs@purdu.du for addiional informaion. Compl procdings may b acquird in prin and on CD-RO dircly from h Ray W. Hrrick Laboraoris a hps://nginring.purdu.du/ Hrrick/Evns/ordrli.hml

2 1319, ag 1 odling and Exprimnal Invsigaion on h Inrnal Lakag in a CO 2 Roary Van Expandr Yang Bingchun*, Sun Shaoyi, ng Xuyuan, Xing Ziwn Insiu of Comprssors, School of Enrgy and owr Enginring Xi an Jiaoong Univrsiy, Xi an, China, Tl: , Fax: , bcyang@mail.xju.du.cn ABSTRACT A roary van xpandr has bn dvlopd o rplac h hroling valv for improving h CO of ranscriical CO2 rfrigraion sysm. Du o h srious inrnal lakag, h xpandr fficincy is no saisfacory. This papr prsns h horical and xprimnal invsigaion on h inrnal lakag in a roary van xpandr prooyp. Firsly, h lakag flow ra hrough h inrnal lakag pahs wih varid clarancs wr masurd undr various prssur diffrncs as h xpandr was saic. Thn, h nozzl and fricion pip modl was usd o simula h flow in h lakag gaps for calculaing h lakag flow ra, and h commrcial CFD sofwar FLUENT was usd o solv h quaions in h modl. Finally, h calculaion rsuls wr compard wih h xprimnal daa. I was shown ha h lakag hrough h sal arc bwn h cylindr and roor is dominan and h prcnag is 41%. Th lakag hrough h nd surfac gaps accouns for 32% and h ohr lakag was mainly associad wih h van. Th roaion spd has lil influnc on h lakag flow ra, hough h volumric fficincy incrass wih h spd dircly. Th sal arc lngh and h gap claranc has a rmarkabl ffc on h lakag flow ra. Springs pu in h van slo wr provn o b abl o hlp h van conac wih h cylindr ighly. Th incrasing roaional spd can improv h volumric fficincy of h xpandr o h valu of 60 a h roaional spd of 3000 rpm. 1. INTRODUCTION Rcnly CO2 bcoms mor and mor popular in h rfrigraion sysm. Th sysm CO is lowr han h radiional rfrigraion sysm du o h high hroling loss associa h hroling valv. any rsarchrs hav mad much ffors o dvlop various xpandrs o rplac h hroling valv for h CO improvmn[1-7]. Roary van yp xpandr has also bn focusd bcaus of is good characrisics such as simpl srucur, small siz, ligh wigh and no nd of inl and oul valvs. Compard wih h radiional rfrigraion sysm, h prssur diffrnc acing on h sucion and discharg pors of h xpandr is much highr, and h flow ra is much lowr. Th lakag bcoms on of h largs challng ha good xpandr prformanc is ampd o achiv, spcially for h roary van xpandr. In his papr h lakag flow hrough h lakag pahs on h roary van xpandr hav bn masurd and mahmaical mod was sablishd o find appropria way o solv h lakag problm. 2. THE EXANDER ROTOTYE 2.1 Basic srucur As shown in Fig. 1, h doubl acing roary van xpandr mainly consiss of cylindr, roor, a baring hous, a shaf, wo ball barings and svn vans. Thr ar wo sucion and discharg pors. As h van numbr is 7, 14 working procsss occur in on cycl. Th sucion procss nds as h working chambr rachs h dsign maxim sucion volum and h discharg procss bgins whn h volum of h working chambr rachs h maxim valu. Thus h sucion and discharg valvs ar boh omid. Owing o h symmrical naur of h srucur, h radial Inrnaional Comprssor Enginring Confrnc a urdu, July 14-17, 2008

3 1319, ag 2 forcs can b balancd, and wo ball barings jus nd o ndur h axial forc acing on h shaf. A shaf sal is usd o prvn h high prssur gas from lak ino h ambin along h shaf. 2.2 Lakag pahs Fig. 1 Th xpandr prooyp. Thr ar 5 main lakag pahs in h roary van xpandr, as shown in Fig. 2. Lakag pah 1 is h lakag dircly from h sucion por o h discharg por hrough h small gap bwn h cylindr and h roor, i.. h sal arc. Lakag pah 2 is h claranc bwn h roor and h nd covr. If h van can no conac h cylindr wall ighly, lakag pah 3 xis bwn h op of vans and h cylindr wall. Similar as lakag pah 2, high prssur gas can pass h claranc bwn h nd surfac of h van and h nd covr o h low prssur chambr, calld lakag pah 4. Lakag pah 5 indicas h gaps bwn h vans and van slos in h roor. Fig.2 Lakag pahs 3. EXERIENTAL INVESTIGATION 3.1 Exprimnal sup As shown in Fig. 3, h prformanc s sysm consiss of on high prssur vssl and on low prssur vssl from which h sucion and discharg prssur hav bn aaind. Th valvs bfor h sucion por and afr h discharg por can conrol h working prssur. A nozzl s is usd o g h flow ra of h air and a gnraor is s for h oupu powr of h xpandr. And h roaion spd of h xpandr can b adjusd by h load on h gnraor. Inrnaional Comprssor Enginring Confrnc a urdu, July 14-17, 2008

4 1319, ag 3 Fig.3 Schmaic diagram of h xprimnal sysm In ordr o g h amoun of h lakags, h shaf of h xpandr is fixd whn h xpandr is filld wih air in diffrn prssur and springs ar addd bwn h vans o nsur h conac bwn h op of h van and h cylindr wall. Th flow ra go by h nozzl s is h amoun of h oal lakag. As shown in fig.4, sal van is arrangd bwn h sucion and discharg por, which prvn h dirc lakag from h sucion por and h discharg por. Th diffrnc of h masurd flow is h lakag from h sal arc. And an aluminum foil is usd o forbid h lakag form h gap bwn h roor and h nd covr, also h diffrnc valu is h lakag from h nd gap. Fig.4 saling masurs 3.2 High Spd Imaging Sysm A high spd imaging sysm is usd o find whhr h op of h van is conacing wih h cylindr all h im. Th yp of high spd vido rcordr is hanom V 7.2 which can g 6888 picurs pr scond and picur siz is A ransparn nd covr is usd o rplac h sl on in ordr o find h innr working procss. Inrnaional Comprssor Enginring Confrnc a urdu, July 14-17, 2008

5 1319, ag 4 Fig.5 High spd vido rcordr 4. THEORETICAL ODEL FOR SEAL ARC LEAKAGE Th lakag hrough h sal arc is a dircly lakag bwn sucion and discharg prssur, and i is dpndd on wo arcs as shown in fig. 6. In his papr, nozzl and fricion pip modl is usd o analysis h lakag mass flow ra[8]. Fig.6 High spd vido According o h gas dynamic hory, ach numbr, and h lngh of h fricion pip l f, saisfis Equaion (1). 2 k L (1 ) 1 1 f k ( ) ln k 2 2 k 1 k 2 (1 ) 2 1 Whr, is h rsisanc cofficin andl f R. If h fluid vlociy a h xi,, is qual o h vlociy of sound. I can b simpl as Equaion (2) as follow. L 1 k 1 ( k1) ln ( 1) 2 2 f 2 2 k k k 2 Inrnaional Comprssor Enginring Confrnc a urdu, July 14-17, 2008

6 1319, ag 5 Thn h prssur raions of and c can b givn as follows: 1 k ( k1) c k k k 1 4 If h oal prssur c in is lss hn h givn prssur raio of h xpandr, h flow choks. Th ach ou numbr is qual o 1, and h mass flow ra can b gon by Equaion (5). m L v R T c g 5 2 Whr, T Tc /[1 ( k 1) / 2] v kr g T. If hr is no chok, h inl ach numbr Equaion (6). ' should b assumd, and h oul ach numbr can b givn by L L k ' 2 2 f f 1 k 1 ( 1) 2 ln 2 2 k 2k 2 ( k 1) 6 ' ' c Whr, l f can b gon by Equaion2using assum valu of.if h nw prssur raion is qual o h in acual givn prssur raio, h righ ach numbrs of and can b calculad. Thn h lakag mass ou ' flow ra is on h way. If h prssur raios ar no qual, h inl ach numbr will b changd unil h righ rsul is gon. 5. RESULTS AND DISCUSSION 5.1 Lakag disribuion in diffrn lakag pahs Fig. 7 shows h flow ras in various lakag pahs undr diffrn prssur diffrncs. I can b found ha lakags incrass wih h prssur diffrncs, bu h incras bcoms smallr and smallr. Th lakag hrough h sal arc is h largs on. Undr h lowr prssur diffrnc, h lakag from h nd covr is smallr, bu h incrasing spd is fasr han in h ohr lakag pahs. Whn h prssur diffrnc is 0.3a, h lakag prcnags hrough h nd covr, sal arc and h rs lakag pahs ar 21.89%, 41.76% and 36.35%, rspcivly. And whn h prssur diffrnc rachs 1.7a, h prcnags chang o 32.06%, 41.16% and 26.77%, corrspondingly. Inrnaional Comprssor Enginring Confrnc a urdu, July 14-17, 2008

7 1319, ag 6 Fig. 7 lakag amouns for diffrn prssur diffrnc Fig. 8 lakag hrough h sal arc 5.2 Lakag hrough h sal arc Th calculad and h xprimnal rsuls of h lakag flow ra hrough h sal arc ar shown in Fig.8. Th solid lin is h calculad rsul from h nozzl and fricion pip modl and h dash lin is aaind by h Spalar- Allmaras modl. Th xprimn rsuls ar rprsnd by h do circl. From his fig, i is shown ha h lakag flow ra grows wih h prssur diffrncs, bu whn h prssur diffrnc is largr han 1.3a, hr is lil chang in h mass flow ra. Furhr compard wih h rsuls from h hr diffrn ways, good agrmn has bn gon in h high prssur diffrnc. Whn h prssur diffrnc is lowr han 1.0pa, h xprimnal daa is a lil largr han h calculad rsuls. Bu forunaly, h xpandr prooyp is usually opraing a high prssur diffrnc condiions. Furhr simulaion is prformd by h wo diffrn modls, focusing h influnc of h gap claranc and h lngh of h sal arc. I is found ha h incrasd angl of h sal arc from 5 dgr o 30 dgr, h mass flow ra will b dcrasd abou 40%, and h rducing gap claranc from 30 m o 10 m h flow ra will b lssn o abou 30%. Th influnc on h roaion spd of h roor is analyzd, and h dcras in h mass flow of abou 3% is found whn h roaional spd is 5000rpm, so h concrn on h varid roaing spd can b nglc. 5.3 Lakags hrough h op of h van For h roary van xpandr, h closur of h working chambr rquirs ha h adjacn vans which conac h cylindr wall ighly. Fig. 9 shows wo picurs caugh by h vido which rcords wo of h working procss. In h s, springs wr pu in four slos. I can b sn ha h vans wihou springs do no conac wih h cylindr wall ighly. Whn h vans pass h inl por, h high prssur gas coming hrough h por pushs h vans back o h van slo. If hr ar springs undr h van, i will com back quickly o conac h cylindr. Bu for h van wihou spring, i will com back much slowly and impac h cylindr wall and rbound back, and h impacing and rbounding procsss will las unil h discharg por is opn. By xamining h hr vans wihou springs carfully, h movmn characrs ar found o b slighly diffrn. Van1 and van 3 almos has h sam working condiion as discussd abov. Bu van 2, similar o vans wih springs, can conac h cylindr wall ighly almos all h im, which agrs wih h p- diagrams analysis[7]. Inrnaional Comprssor Enginring Confrnc a urdu, July 14-17, 2008

8 1319, ag 7 a) roaional angl1 b) roaional angl 2 Fig. 9 van posiion in h working procss 6. CONCLUSIONS In his papr, lakags hrough h hr main lakag pahs of h roary van xpandr hav bn invsigad by mahmaical modls and xprimn. Som conclusions can b drawn as follows: 1) Among various lakags pahs, h lakag from h sal arc is h mos srious, and h prcnag is abou 41%, whn h lakag from h nd covr is abou 32% and h rs is 27%. 2) Th mass flow ra hrough h lakag pahs incras wih h prssur diffrnc, bu h incrasing spd bcoms smallr and smallr. 3) Th nozzl and ficion pip modl and Flun can saisfacorily prdic h lakag flow ra hrough h sal arc spcially a high prssur diffrnc. By h wo modls, i can b found ha nhancing h lngh and rducing h gap claranc of h sal arc can dcras h lakag mass obviously. And h roaional spd has lil influnc on h lakag. 4) Th vans wihou springs hlp can no conac h cylindr wall ighly, bu h prssur diffrnc bwn adjacn chambrs can mak h middl van bwn h hr vans work wll. 5) Whn h roaional spd is 500 rpm, h volumric fficincy of h xpandr is abou 10%. Bu h incrasing roaional spd can improv h volumric fficincy of h xpandr o h valu of 60 a h roaional spd of 3000 rpm. REFERENCES [1] Bak J S, Groll E A, and Lawlss B. ison-cylindr work producing xpansion dvic in a ranscriical carbon dioxid cycl. ar I: xprimnal invsigaion [J]. Inrnaional Journal of Rfrigraion, 2005, 28 (2): [2] Huff H. and Radrmachr R. Exprimnal Invsigaion of a Scroll Expandr in a Carbon Dioxid Air- Condiioning Sysm [C] // rocdings of Inrnaional Congrss of Rfrigraion Washingon, D.C: [s. n.], 2003 [3] Nickl J, Will G, Quack H, al. Ingraion of a hr-sag xpandr ino a CO2 rfrigraion sysm [J]. Inrnaional Journal of Rfrigraion, 2005, 28 (8): [4] Fukua. and Yanagisawa T. rformanc prdicion of van yp xpandr for CO2 cycl [C] // rocdings of Inrnaional Congrss of Rfrigraion Washingon, D.C: [s. n.], 2003 [5] Zhang Bo, ng Xu-yuan, Zhang Fang-xi, a. Dvlopmn and Exprimnal Validaion of Novl Fr ison Expandr [J] Journal of Xi'an Jiaoong Univrsiy. 2006, 40 (7): (Chins) [6] Li in-xia, A Yi-ai, SU Wi-chn, al. Rsarch and Dvlopmn of Rolling ison Expandr in CO2 Transcriical Cycl. [J] Journal of Tianjin Univrsiy. 2004, (9). (Chins) [7] Yang Bingchun, Guo Bi, ng Xuyuan, al. Exprimn Rsarch on h Inrnal Working rocss of a Roary Van Expandr in h CO2 Rfrigraion Sysm [J]. Journal of Xi'an Jiaoong Univrsiy. 2008, (3) (Chins) [8] T.yanagisawa and T.shimizu Lakag losss wih a rolling pison yp roary comprssor. I. Radial claranc on h rolling pison [J]. Inrnaional Journal of Rfrigraion, 1985, 8: Inrnaional Comprssor Enginring Confrnc a urdu, July 14-17, 2008

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