Optimal Design Schemes of Centrifugal Pump Compound Impeller at Super-Low Specific Speed

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1 811 A publication of CHEMICAL ENGINEERING TRANSACTIONS VOL., 15 Gust Editors: Piyu Rn, Yancang Li, Huiping Song Copyright 15, AIDIC Srvizi S.r.l., ISBN ; ISSN 8-1 Th Italian Association of Chmical Enginring Onlin at DOI: 1./CET151 Optimal Dsign Schms of Cntrifugal Pump Compound Impllr at Supr-Low Spcific Spd Yabing Tian* a, Jin Wang b, Liang Wang a a Institut of civil nginring and architctur, Southwst Univrsity of Scinc and Tchnology, Mianyang 11 Sichuan b Jinchuan Group Corporation Ltd. Jinchang 771 Gansu tianyb8@1.com Th papr has stablishd sixtn dsign schms for supr-low spcific spd cntrifugal pump compound impllr with orthogonal mthod, basd on th main factors impacting th dsign of compound impllr, lik short blads numbr of compound impllr, th rlativ position of blad radial inlt, blad circumfrntial bias dgr, dflction angl, tc.,. By numrical simulation, th optimal dsign schm has bn dtrmind. Compard with th mthod of prmutation and combination, th optimal dsign schm can gratly rduc th workload of th dsignrs. In th mantim, by applying th orthogonal mthod for compound impllr dsign, th compound impllr intrnal prssur and vlocity fild distribution bcom quit rasonabl, th curv HQ is mor flat, th η Q curv xcurss to th big flow, and also th work prformanc is fairly good. 1. Introduction Rcntly, lots of works hav bn don to improv th prformanc of supr-low spcific spd cntrifugal pump compound impllr(ns ),and th rsults show that compound impllr with matchd long and short blads can ffctivly prvnt th mrgnc and dvlopmnt of wak flow, thus improving th vlocity distribution in th impllr. With finit blad corrction cofficint incrasd, th pump lift will b improvd, on of th ffctiv ways to nhanc th prformanc of low spcific spd cntrifugal pump(cui Baoling t al. (), Majidi. (5), rgourlay G t al. (7), Yuan Shouqi t al.( 7), Yuan Shouqi(17)). With compound impllrs consisting of long and short blads bing abl to tak many forms, th diffrnt stting placs of long and short blads will produc diffrnt dsign ffcts, and will also impact th fficincy of th compound impllr. Basd on th analysis of th short blad bias dgr, th factors influncing th compound impllr short blad bias dsign hav bn providd in Rf. (Zhang Jinfng (7)). And in Rf.( CHEN Song-shan t al. (5), Yuan Shouqi t al. (8)), orthogonal mthod is usd to calculat and analyz th prformanc of diffrnt short blads by slcting thr factors, thr lvls L ( ), thr factors, and four lvls L ( ). Although crtain valuabl rsults of compound impllr hav bn achivd in rcnt yars, th dsign of high-spd low spcific spd cntrifugal pump is still dficint, with maximum flow dsign, ara ratio principl dsign, non-ovrload dsign, tc., adoptd to dsign supr-low spcific spd cntrifugal pump in gnral. According to th main factors influncing th compound impllr dsign, this papr prsnts a mthod of using th orthogonal mthod and numrical simulation mthod to slct a high prformanc supr-low spcific spd cntrifugal pump compound impllr among numrous dsign modls.(francsco M, t al. (8), Hayashi I, anko S,(1), Spnc R, Amaral-Tixira J. (),Spnc R, Amaral-Tixira J.( 8), Yao Zhifng t al. (1), Wu Yulin t al. (1)). Th functional rprsntation Th main prformanc paramtrs of supr-low spcific spd cntrifugal pump ar as following: lift:, flow:, rotation rat: 8, fficincy, nt positiv suction had. According to th abov dsign paramtrs and rquirmnts, basd on th dsign tradition and xprincs on supr-low spcific spd cntrifugal pump, Plas cit this articl as: Tian Y.B., Wang J., Wang L., 15, Optimal dsign schms of cntrifugal pump compound impllr at supr-low spcific spd, Chmical Enginring Transactions,, DOI:1./CET151

2 81 th long and short blads will b spatial warping blads, qual in numbr, and placd altrnatly. According to th documnts (Zhang Jin-fng (7), Zhu Zu-chao (7)), th basic gomtric paramtrs ar prliminarily dtrmind as in tabl1: Tabl 1: th basic gomtric paramtrs of impllr D / mm D / mm β /( ) β /( ) b / mm b / mm S /( mm ) Orthogonal dsign mthod According to orthogonal dsign principl, th factors and lvls that influnc th compound impllr dsign will b slctd as following: (1) Factor (A): short blad numbr is rprsntd by z ; Lvl:,, 5, and ; () Factor (B): rlativ position of short blad radial inlt, namly th ratio of th short blad inlt diamtr Di and impllr xtrnal diamtr D ; Lvl:.55,.,.5, and.. () Factor(C): short blad circumfrntial bias dgr ti t: t i mans th lattic spacing btwn short blad working fac and th long blad back sid; t mans th lattic spacing btwn two long blads; th ratio of th two lattic spacing ti t mans th circumfrntial bias dgr; Lvl:.5,.5,.5,.5; () Factor (D): dflction anglα ; Lvl:,, and. Basd on th abov factors and lvls, and th principl of orthogonal mthod, as wll as L ( ) dsign 1 schm, sixtn diffrnt kinds of compound impllr dsign schms hav bn dtrmind. Tabl shows xprimntal factors and lvls, and tabl rflcts orthogonal dsign schms. Tabl : Orthogonal xprimntal factors Factor A Factor B Factor C Factor D Lvl Blads No. Short blad radial position short blad circumfrntial dflction angl z Di D bias dgr t i t α Tabl : Dsigning schms Schm factors Schm factors Schm factors Schm factors No. Matchd No. Matchd No. Matchd No. Matchd Numrical simulation and analysis of orthogonal dsign schms.1 Numrical calculation mthod By using FLUENT softwar, th papr has adoptd thr-dimnsional unstady incomprssibl Rynolds N S quation and standard κ ε turbulnc modl to raliz th coupling of prssur and vlocity with SIMPLEC algorithm. For discrt format, th prssur has applid scond-ordr cntral diffrnc format. Vlocity, turbulnt kintic nrgy and turbulnt kintic nrgy cofficint hav applid scond ordr upwind diffrnc format. During th itrativ calculation, th rlaxation itration has bn applid, and th strss rlaxation cofficint is., whil th spd is.7, turbulnt kintic nrgy is.8, and th turbulnt kintic nrgy dissipation rat is.8.

3 81. Simulation tst rsults of orthogonal mthod Th abov 1 kinds of compound impllr cntrifugal pump dsign schms hav bn prformd simulating calculation, as shown in figur 1. Lift and fficincy valu undr ach dsign condition hav bn obtaind, sing th rsults in tabl. Th lift and fficincy valu of compound impllr in schm (5), (7), (8), namly factor lvl B-1, orthogonal dsign schm with short blads ratio z =, havn t mt th dsign rquirmnts. Th lift of compound impllr in dsign schm () is highr, whil th fficincy valu is lowr. It s du to unrasonabl collocation of long and short blads. Th rsults furthr prov that not all compound impllrs with long and short blads ar rasonabl, among which thr must b impllrs with bttr or poor prformancs. According to th tsts data, lift and fficincy indxs from all othr dsign schms hav satisfid th dsign rquirmnts. Compard with th dsign indxs, th lift valu and fficincy valu hav incrasd at diffrnt lvls. Lift valu has bn improvd 11.15% and th fficincy valu has bn nhancd.%. Tabl : Exprimntal rsults at point of Dsign condition Schm H m η % Schm H m η % Schm H m η % Schm H m η % ⑴ ⑵ ⑶ ⑷ ⑸ ⑹ ⑺ ⑻ ⑼ ⑽ ⑾ ⑿ ⒀ ⒁ ⒂ ⒃ Rang analysis of tst rsults Th tst rsults hav bn furthr analysd and procssd according to rang analysis mthod, th rang valu btwn lift valu and fficincy valu and short blad orthogonal dsigning factor lvl hav bn obtaind. Exactly, i mans th sum of corrsponding lvl calculation rsults; i mans th avrag calculation rsult of corrsponding lvl; R mans th rang valu, and th rsults hav bn shown in tabl 5. It can b obsrvd from th rang valu diffrnc R that among short blad dsign influncing factors: th primary and scondary squnc that influncs lift is ACDB. For fficincy valu, th affcting primary and scondary ordr is ABCD Tabl 5: Rang analysis rsults at point of Dsign condition Lvl H η A B C D A B C D R

4 81 (1) () (5) () () (1) () () (7) (8) (11) (1) Figur 1: Static prssur distribution of diffrnt impllrs at th point of Dsign condition. Analysis of various factors influncing on th short blad dsign According to th abov rang analysis rsults, th factors changing with th lift and fficincy valu ar as following: Factor A: with th incrasing of blad numbr, th lift dcrass at first and thn gradually incrass. Th lift valu is th lowst whn th blads numbr is, and whil th blad numbr is 5, th lift valu is th highst. Sam as lift valu changing trnd, th fficincy valu is th lowst whn th blad numbr is. Th fficincy incrass along with th incrasing of blad numbr. Takn lift and fficincy valu togthr, th idal blad numbr is fiv. Factor B: short blad radial inlt locats in th scond lvl, namly taking Di D =. ; th corrsponding fficincy rachs th highst. In th first lvl, taking th valu Di D =.55, th lift valu is slightly lowr than th valu in th scond lvl, but th fficincy valu is much lowr. By comparison, th lift and fficincy valus of all othr lvls ar lowr, thus, th scond lvl has bn slctd as th lvl valu of factor B. Factor C: In addition to th scond lvl t i t =.5, in which th lift valu has not mt th dsign rquirmnts, lift indxs of all othr lvls hav rachd th dsign rquirmnts. Efficincy is rising gradually with th incrasing of short blad circumfrntial bias dgr and has rachd th highst at th

5 815 fourth lvl. Thrfor, th fourth lvl has bn slctd for factor C, namly th short blad circumfrntial bias dgr is t t =.. i Factor D: Whn th dflction angls ar, and, which mans that th horizontal lvls ar on, two, and thr; lift indxs of pump ar similar. Whn th α =, th lift valu nhancs obviously. Thrfor, th fourth lvl has bn chos for factor D, namly th angl of short blad turning to th long blad back sid is α =. According to th abov factors and lvls analysis, th optimal compound impllr dsign schm will b as following: th short blad numbr is prliminary dtrmind as z = 5, th rlativ position of radial inlt is D D =., and th angl of short blad turning to th long blad back sid is i α =. 5. Th numrical simulation of convntional impllr and compound impllr Th optimal compound impllr dsign schm undr orthogonal mthod has bn compard with th convntional impllr with th sam numbr of long blads. Numrical simulation for both typs of impllrs has also bn carrid out undr th dsign conditions. Through numrical simulation, th prformanc fficincy valu of compound impllr is around 8.1%, whil th prformanc fficincy of rgular impllr is about 1.5%. As shown from th rsults, th fficincy of compound impllr was obviously highr than that of th convntional impllr. Th static prssur distribution and th rlativ vlocity distribution of both impllrs hav bn shown in figur 1 and figur. From th rlativ vlocity distribution figurs, it can b concludd that flow sparation phnomnon of th long blad back sid has bn obviously rducd aftr adding short blads btwn long blads. And also, backflow phnomnon of two long blads outlt has bn rducd. From static prssur figur, it can b sn that comparing with convntional impllr, th high prssur ara of compound impllr outlt and laryngal of th volut hav bn significantly dcrasd. Th static prssur has distributd mor uniformly, and th flow ability is also bttr than convntional impllr. Morovr, intrnal static prssur distribution and th rlativ vlocity distribution of compound impllr ar suprior to th convntional impllr. Figur : Static prssur distribution of two impllrs on dsign conditions Figur : Rlativ vlocity distribution of two impllrs on dsign conditions. Conclusion (1)Among all impllr prformanc influncd factors, th orthogonal dsign mthod has bn applid. Undr numrical simulation and analysis, th optimal compound impllr dsign schm can b obtaind, which is also mor convnint than th traditional mthod, prmutation and combination, and th workload of th

6 81 dsignrs will b gratly rducd. Thrfor, it can b boild down that th mthod is a fasibl optimal dsign mthod. ()Undr th sam dsign condition, comparing dsign schm applying th orthogonal mthod with convntional dsign schm, th intrnal prssur fild and vlocity fild distribution of th optimal compound impllr ar mor rasonabl with highr fficincy and bttr prformanc, Q H curv is smoothr, and Q η curv xcurss to th big flow. ()Compound impllr dsign mthod is on of ffctiv ways to improv th fficincy of supr- low spcific spd cntrifugal pump. Howvr, if th long and short blads inappropriat combind, th fficincy of th pump will b rducd. Thrfor, only in th rasonabl collocation of th long and short blads, can th compound impllr dsign gain th optimal dsign rsults. Acknowldgmnts Projct (1zx715) supportd by Rsarch Foundation for PHD of Southwst Univrsity of Scinc and Tchnology (1zx715).Mianyang, applid tchnology rsarch and dvlopmnt projct funding (1G - - ). Rfrnc Chn S.S., Zhou Z.F., G Q., 5, Orthogonal xprimntal study on cntrifugal pump with dviatd splittr vans [J]. Journal of Yangzhou Univrsity: Natural Scinc Edition, 8():5-8(in Chins). Cui B.L., Zhu Z.C., Zhang J.C., Chn Y.,, Th flow simulation and xprimntal study of low-spcificspd high-spd complx cntrifugal impllrs[j]. Chins Journal of Chmical Enginring: English Edition, 1():5-1. DOI: ()-7. Francsco M., Francsco M.C., Maurizio A., 8, Prssur pulsation in rollr pumps: A validatd lumpd paramtr modl [J]. Mdical Enginring & Physics, : Hayashi I., anko S., 1, Prssur pulsations in piping systm xcitd by a cntrifugal turbo machinry taking th damping charactristics into considration[j].journal of Fluids and Structurs, 5: 1-. rgourlay G., Younsi M., Bakir F., 7, Influnc of splittr blads on th flow fild of a cntrifugal pump:tst-analysis comparison[j]. Intrnational Journal of Rotating Machinry, Articl ID: 85. Majidi., 5, Numrical study of unstady flow in a cntrifugal pump [J]. Journal of Turbo machinry, 17(1):-71.DOI: Spnc R., Amaral-Tixira J.,, A CFD paramtric study of gomtrical variations on th prssur pulsations and prformanc charactristics of a cntrifugal pump[j].computrs & Fluids, 8: DOI: Spnc R., Amaral-Tixira J., 8, Invstigation into prssur pulsations in a cntrifugal pump using numrical mthods supportd by industrial tsts [J]. Computrs & Fluids, 7: -7. DOI: Wu Y.L., Liu S.H., Dou H.S., Wu S.F., Chn T.J., 1, Numrical prdiction and similarity study of prssur fluctuation in a prototyp aplan turbin and th modl turbin[j]. Computrs & Fluids, 5, 18-1.DOI: Yao Z.F., Wang F.J., Xiao R.F., 1, y issus in prssur fluctuation xprimnts for cntrifugal pumps [J]. Journal of Drainag and Irrigation Machinry Enginring, 8(): 1-. Yuan S.Q., 17, Thory and dsign of low spcific spd cntrifugal pump [M]. Bijing: China Machin Prss,. Yuan S.Q., Zhang J.F., Yuan J.P., 7, Effcts of splittr blads on th law of innr flow with in a cntrifugal pump impllr [J]. Chins Journal of Mchanical Enginring: English Edition, (5):5-.DOI: Yuan S.Q., Zhang J.F., Yuan J.P., 8, Orthogonal xprimntal study ffct of main gomtry factors of splittr blads on pump prformanc [J].Drainag and Irrigation Machinry, ():1-5.(in Chins) Zhang J.F., 7, Th whol flow fild numrical forcast and dsign mthod studis on splittr blad cntrifugal pump [D]. Zhnjiang: Jiangsu Univrsity. Zhu Z.C., 7, Thory and dsign application of high spd cntrifugal pump at low spcific spd [M]. Bijing: China Machin Prss, 7.