A STUDY OF PARAMETERS THAT AFFECT PIVOTED SHOE JOURNAL BEARING PERFORMANCE IN HIGH-SPEED TURBOMACHINERY

Transcription

1 A STUDY OF PARAMETERS THAT AFFECT PIVOTED SHOE JOURNAL BEARING PERFORMANCE IN HIGH-SPEED TURBOMACHINERY by Scan DCamillo Managr, Rsarch and Dvlopmnt Kingsbury, Inc. Philadlphia, Pnnsylvania and Kith Brockwll Snior Rsarch Officr National Rsarch Council of Canada Institut for Arospac Rsarch Ottawa, Ontario, Cauada Scan DCamillo is Managr of Rsarch and Dvlopmnt for Kingsbury, Inc., in Philadlphia, Pnnsylvani H is rsponsibl for dsign, tsting, analysis, and dvlopmnt of Kingsbury fluid film barings for worldwid industrial and military applications. H bgan work in this fild in 1975 and has sinc providd nginring support to industry rgarding problm solving, dsign improvmnt, application, and opration of hydrodynamic barings in various machinry. During th cours of his work, Mr. DCamillo has dvlopd plformanc and structural tools for baring analysis, stablishd dsign critriafor powr, naval, and nuclar applications, and has contributd information to ASM, AISI, EPRI, NASA, and API for various publications and spcifications. H is an invntor and author of svral tchnical paprs. Mr. DCamillo rcivd his B.S. dgr (Mchanical Enginring) from Drxl Univrsity. H is a rgistrd Profssional Enginr in th Stat of Pnnsylvania and a mmbr of th Vibration Institut, ASM, ASME, and STLE. Kith Brockwll is a Snior Rsarch Officr with th National Rsarch Council of Canada's Institut for Arospac Rsarch, in Ottawa, Ontario, Canad His major rsarch intrsts ar tribology, fluid film lubrication, and baring tchnology. H has authord and coauthord clos to tchnical paprs and rports daling with ths topics. Mr. Brockwll rcivd his postgraduat training from Imprial Collg and Nwcastl Polytchnic, England. Prvious UK appointmnts includd th Glacir Mtal Company and Michll Barings whr h was Managr of th Dsign Srvics Dpartmnt. H is a Chartrd Enginr (UK), a Mmbr of th Institution of Mchanical Enginrs, and a Fllow of th Socity of Tribologists and Lubrication Enginrs. Mr. Brockwll is a mmbr of th STLEIASME Tribology Confrnc Planning Committ, and was formrly an Adjunct Profssor at th Univrsity of British Columbia, whr his taching intrst was tribology. ABSTRACT Journal baring pad tmpraturs, oil flow rquirmnts, and powr losss can impos limitations on th dsign and opration of high-spd turbomachinry. Ovr th past fw yars, th authors hav conductd xtnsiv tsts and studis of paramtrs that affct pivotd sho journal baring prformanc. A spcial, high-spd tst rig is dscribd, which was dsignd and built for th purpos of masuring baring stady-stat prformanc charactristics undr light to modratly havy loads, and to vry high oprating spds that ar bing approachd in nw turbin and comprssor dsigns. Instrumntation includs a dtaild array of pad tmpratur dtctors and th dirct masurmnt of frictional torqu. Data ar prsntd that compar th ffcts of pivot offst, oil flow, load orintation, mthod of lubrication, and oil discharg configuration on 6 inch diamtr pivotd sho journal baring prformanc. Th paramtrs ar shown to significantly influnc baring pad tmpratur and powr loss, particularly at high loads and spds. Pad tmpratur profils, isothrms, torqu, and oil outlt tmpraturs ar compard and valuatd. Discussions addrss th prdiction and application of ths paramtrs, and how thy may b usd to improv th capacity and prformanc of high-spd turbomachinry. Th data and discussions ar intndd to provid usful information to nginrs, programmrs, and prsonnl involvd with th study or opration of pivotd sho journal barings. INTRODUCTION Turbomachinry oprating spds and loads hav incrasd ovr tim rsulting in incrasd baring tmpraturs and powr losss. Gardnr and Ulschmid (1973) addrssd th concrn of journal baring limitations at turbulnt opration, documnting a dramatic incras in pad tmpratur and powr loss of a 17 inch pivotd sho baring at 30 rpm (267 fps surfac spd). Th pad was a cntr pivot dsign, which has th advantag of bing abl to oprat in ithr dirction of rotation. Thr ar many tchnical paprs that study cntr pivot journal barings. Offst pivots improv journal baring pad tmpratur limitations, but ar not as wll documntd in litratur. Larg stam and gas turbin dsignrs ar prsntly considring 22 inch and largr diamtr journal barings for powr gnration whr surfac spds at 30 rpm xcd 330 fps. Dsignrs of stam turbins and comprssors hav intntions for oprating spds approaching 400 fps. Such conditions ar wll into th turbulnt rgim whr convntional baring losss and 9

2 10 PROCEEDINGS OF THE 30TH TURBOMACHINERY SYMPOSIUM tmpraturs bcom so high that options must b considrd to addrss limitations. Dirct lubrication is on solution that has bn succssfully applid in thrust barings for many yars, and also in spcial journal baring applications dating back to th mid-sixtis. It is only rcntly that dirct lub journal barings hav bn sriously considrd for gnral turbomachinry applications bcaus high surfac spds now warrant such a considration. As in th cas of offst pivots, tchnical paprs on dirct lub journal barings ar spars. Data ar publishd by Tanaka (1991) and Tanaka and Mishima (1989) comparing 100 mm (3.94 inch) diamtr dsigns to 137 fps; Harangozo, t a1. (1991), tstd 5 inch diamtr barings to 152 fps; and Fillon, t a1. (1993), rport on 100 mm (3.94 inch) diamtr data to fps. Th authors' (Brockwll, t ai., 1992, 1994; Dmochowski, t ai., 1993) tstd 3.88 inch diamtr, lading-dg-groov (LEG) dsigns to 2 fps; DCamillo and Clayton (1997) provid data on an 18 inch LEG gnrator baring at 283 fps; and Edny, t a1. (1996), rport on 5 inch diamtr LEG stam turbin barings running to 312 fps. In assssing baring limitations, thr ar many paramtrs that affct rsults including gomtry, oprating conditions, and vn instrumnt location. For xampl, DChoudhury and Barth (1981) show that th drop in oil outlt tmpratur btwn th baring and drain lin can lad to significant diffrncs in thrmal balanc calculation of powr loss. Pinkus (1990) dscribs pculiar bhavior btwn laminar, transitional, and high-spd turbulnt rgims of baring opration. Pttinato and DChoudhury (1999) not high dg tmpraturs from misalignmnt in ball-in-sockt pivot gomtry. Wygant, t a1. (1999), show diffrncs in stadystat and dynamic prformanc attributd to rstriction of pad motion by friction in sliding contact pivots. Convntional floodd journal barings wr usd in ths rfrncs. Th floodd journal baring dsign has bn studid for many yars, and information is availabl for a wid rang of oprating loads and spds. In contrast, th fw publishd paprs on dirct lub journal barings citd arlir mostly rport on low spd opration, in th laminar to transitional rang of opration. Thr is som disagrmnt rgarding th magnitud of th bnfits of dirct lubrication. This may b du to laminar/transitional influncs, but thr ar also diffrncs in th mthod of dirct lubrication, as wll as th typ of pivot, instrumnt location, tc. In gnral, all rfrncs agr that dirct lubrication provids pad tmpratur bnfits that appar to improv with load and spd. Thr is also agrmnt that dirct lub powr loss is lowr, although most authors rport that thrmal balanc mthods ar of insufficint prcision to allow an accurat assssmnt. Bnfits ar typically attributd to liminating sal losss and rducing churning losss, but ths ar hypothtical bcaus thr ar littl data availabl for confirmation. In ordr to addrss such issus, a spcial tst rig was dsignd and built to masur stady-stat prformanc undr light to modratly high loads, and to vry high oprating spds that ar bing approachd in nw turbin and comprssor dsigns. An important fatur of th rig is th dirct masurmnt of frictional torqu, which provids a mor prcis masurmnt of powr loss than thrmal balanc tchniqus. Ovr th past fw yars, th authors hav conductd xtnsiv tsts and studis of paramtrs that affct th prformanc of pivotd sho journal barings. Th purpos of this work is to improv th capacity and prformanc of high-spd turbomachinry by xtnding baring spd and/or load limitations and improving fficincy. TEST RIG Tsts wr prformd on a nw rig dsignd to invstigat stady-stat prformanc undr high oprating spds and light to modratly havy unit loads. Th tst apparatus is illustratd in Figur 1 and consists of a tst baring, th shaft and driv systm, th loading systm, and th rig supporting structur. co. l1li. _a_a _BII_--.J o ' Figur 1. Tst Rig SchmCltic. Tst Rig 6 inch Tst Shaft Spd to 100 rpm Loads to 50 Ibs Th tst shaft is drivn by also hp variabl spd DC lctric motor. A blt and pully systm conncts th motor to th tst shaft and provids a 4.5: 1 spd stp-up giving a maximum shaft spd of just ovr 16,000 rpm. Th DC motor is linkd to an lctronic controllr that nsurs spd control to within ± 1 prcnt accuracy. Th tst shaft is supportd by two 3.5 inch diamtr pivotd sho journal barings spacd approximatly 28 inchs apart. Th tst shaft journal is 6 inchs in diamtr with circularity within inch. Shaft spd is masurd using a slottd optical switch in conjunction with a shaft-mountd disk containing a numbr of drilld hols. This was found to b a robust systm capabl of rliabl opration vn at th top spd of th tst facility. An important fatur of th rig is th dirct masurmnt of frictional torqu. This is accomplishd by th dsign of th tst housing (Figur 2). Th two-pic housing is positiond on th tst shaft, midway btwn th support barings. Th bottom fac has bn accuratly machind and sits in a sphrical hydrostatic baring that liminats friction btwn th housing and th loading dvic. Th housing is hld against rotation by a 100 lb capacity load cll mountd to a torqu arm. Powr loss is dtrmind from th masurd frictional forc, and radii of th torqu arm and baring bor. Th sphrical hydrostatic baring also provids good alignmnt btwn th tst baring and shaft. A scond plan hydrostatic baring supports th sphrical hydrostatic baring. This provids latral frdom and allows th load lin to b adjustd in rlation to th tst baring. Proximity probs mountd on both nds of th tst baring housing masur th horizontal and vrtical displacmnts of th tst baring with rspct to th position of th shaft. Ths probs also provid an indication of th lvl of alignmnt btwn th tst baring and th shaft. A pnumatic cylindr locatd btwn th tst housing and bas of th rig (Figur 1) gnrats th static load. This has a capacity of 50 lb. Thr load clls locatd btwn th top of th load applicator and th bottom surfac of th plan hydrostatic baring masur th vrtical load applid to th tst baring. Th load clls ar arrangd in such a way that thy ach shar an qual proportion (on-third) of th load applid to th baring. In calculating th nt load on th tst baring, th combind wight of th tst baring, housing, and th hydrostatic baring systm is accountd for. A pump with a capacity of 20 gpm and a maximum supply prssur of 300 psig dlivrs oil to th tst baring from also gallon capacity tank. Th flowrat is masurd by a turbin typ flowmtr with a linar flow rang of 2.5 to 29 gpm. Fd oil tmpratur is masurd bfor it ntrs th tst baring, and is controlld by a watr-oil hat xchangr to ± 1 C (33.8 F). An industrial typ prssur transducr with a prssur rang of zro to

3 A STUDY OF PARAMETERS THAT AFFECT PIVOTED SHOE JOURNAL BEARING PERFORMANCE IN HIGH SPEED TURBOMACHINERY Typ T thrmos.020" blow surfac Load Masurmnt of Frictional Torqu (Powr Loss) Figur 2. Tst Housing and Torqu Masurmnt Systm. psig masurs oil supply prssur to th tst baring. Thrmocoupls masur th oil inlt tmpratur, and th oil outlt tmpratur from ach sid of th tst baring. Flowrat and inlt and outlt oil tmpraturs ar usd in thrmal hat balanc calculations of powr loss for comparison with valus obtaind from masurd torqu. A spcial data acquisition systm was dvlopd for rcording th dat In this systm, procss signals from th tst facility ar rcordd using a Windows graphical usrs intrfac program. This program provids an intrfac btwn th analog/digital hardwar and th oprator, prmitting ral-tim display of procss conditions, th acquisition of tst data, and signal procssing such as data trnding, frquncy analysis, and digital filtring. Signals procssd and displayd by th data acquisition systm includ tst and support baring tmpraturs; oil supply and outlt tmpratur, supply prssur, tank tmpratur, and flow; shaft spd, baring load, tst bating friction forc, and X and Y displacmnts. Th data acquisition hardwar cards ar ratd at 1 MHz and th display scrn is updatd vry scond. Masurmnt uncrtaintis of th quipmnt ar listd in Tabl 1. Tabl 1. Tst Rig Masurmnt Uncrtaintis. Masurmnt Tyj> of snsor Limit of rror of snsor Tmpratur Typ T thrmocoupl I 'c or 0.75% (whichvr is gratr) Shaft spd Optical switch ± 5 rpm Baring load lb. load clls (x 3) ± 5 lb. at full scal Friction forc lb. load cll ± 0.1 lb. at full scal Displacmnts Eddy currnt proximity probs ± in Oil flowrat Turbin flow mtr ± 0.5% of rading Oil supply prssur Prssur transducr ± 0.6Iblin" Lading dg groov Miniatur prssur transducr ± 0.75 Ib/in oil prssur Driv motor powr Powr cll ± 10 hp consumption TEST BEARINGS AND OPERATING CONDITIONS Th tst barings ar 6 inchs in diamtr, hav a lngthto-diamtr ratio, a.0045 inch assmbld radial claranc, and a.25 prload. Th tst baring pads ar of th sam gomtry, consisting of fiv pivotd pads with dgr pad angls. Th pivot is a rolling contact dsign with curvatur in both th axial and circumfrntial dirctions. This allows for axial alignmnt capability, and frdom of movmnt undr changs in oprating conditions. Th tst baring pads ar instrumntd with an altay of 45 typ T thrmocoupls with th tip of ach thrmocoupl locatd.020 inchs blow th babbitt surfac (Figur 3). Th loadd shos ar mor havily instrumntd along th cntrlin, and hav additional thrmocoupls along th dgs of th pads (Figur 4). c'cw rotation Figur 3. Babbitt Thrmocoupl Locations. % of arc lngth t ,.,. III.., o c'cw rotation Figur 4. Loadd Sho Instrumntation Locations. Tsts wr prformd ovr a rang of loads and spds to compar th ffcts of pivot offst, oil flow, load orintation, mthod of lubrication, and oil discharg configuration. A dscription of th spcific paramtr bing tstd is dtaild in th associatd sction of this papr. Th lubricant usd in this sris of tsts was an ISO VG 32 turbin oil, with a masurd viscosity of cntistoks at 40 0 (l04 F), and 5.41 cntistoks at looo (212 F). All tsts wr run with an oil supply tmpratur of 49 (.2 F). CONVENTIONAL FLOODED BEARING TESTS AND DISCUSSIONS In hydrodynamic lubrication, th journal surfac drags oil into th spac btwn th journal and baring pads. Th trms "convntional" and "floodd" ar trms usd to dscrib th mthod of lubrication that provids oil to th journal surfac. Th convntional mthod is to rstrict th hot discharg oil by saling th sids of th baring around th shaft such that th baring cavity is floodd. This provids oil to th journal surfac by filling th spacs btwn th pads. Thr ar a coupl of variations. Floating sal rings ar somtims usd with tight shaft-to-sal clarancs. Oil discharg is thn rstrictd by oil outlt hols, sizd to provid a slight back prssur to flood th housing. Anothr discharg configuration uss labyrinth sals whr oil discharg is controlld by th gap btwn th sals and shaft. Labyrinth sals wr usd for th floodd baring tsts in this rport. RflTing to Figur 5, oil is supplid to an outr annulus around th baring, through radial oil supply hols btwn ach pad, and is rstrictd by sals on ach sid of th baring. Cntr Pivot Vrsus Offst Pivot Tsts This sris of tsts was prformd with convntional, floodd pivotd sho journal barings, to compar th ffct of pad pivotlocation on baring prformanc. Th pivot locations tstd ar

4 12 PROCEEDINGS OF THE 30TH TURBOMACHINERY SYMPOSIUM Cntr Pivot I'J Offst Pivot Sals Sals 1.==.' 1 Oil outlt 4t Figur 5. Convntional (Floodd) Baring Lubrication. shown schmatically in Figur 6. Th cntr pivot dsign has th pivot locatd in th cntr of th pad, prcnt of th pad arc lngth from th lading dg in th dirction of rotation. Th offst pivot dsign has th pivot locatd at prcnt of th pad arc lngth from th lading dg. Othr than th location of th pivot, th baring gomtry for th two sts of pads is idntical. % offst % offst (cntr pivot) (offst pivot) Figur 6. Cntr and Offst Pivot Gomtry. Pad Tmpratur Profils Pad tmpratur profils ar obtaind by plotting th cntrlin thrmocoupl tmpraturs against th rlativ angular position of th dtctor in th barings as dpictd in Figur 7. This figur is for a load-on-pad (LOP) orintation whr th load is dirctd toward a singl pad. Th loadd pad data ar in th cntr of th figur. As spd and load ar incrasd (Figurs 8 and 9), th loadd pad tmpratur incrass and will vntually limit th application. Figur 10 compars th loadd pad tmpratur profils plottd according to position along th pad arc lngth. }--!J : 110 l E " 100 '" Co r Cntr Pivot GEl Offst Pivot LOP.. ()? - -Coad r} + Baring Load On \':, Pad =::::::::::::::::::::::::::::::::::::::::::====:::::::::::==--.. Rotation position (dg.) Figur 7. Pad Tmpratur Profils, LOp, 200 PSI, 30 RPM. : lid " 100 Co " "0 80 f I \rr"" position (dg.) Figur 8. Pad Tmpratur Profils, LOP, 200 PSI, 9000 RPM. 140 : 110 " 100 " Co 80 Cntr Pivot I'J Offst Pivot f /.J " ()? +L t::t:::: po ; position (dg.) Figur 9. Pad Tmpratur Profils, LOP, 320 PSI, 9000 RPM. Cntr Pivot ill Offst Pivot : 110 E " 100 " Co -g L- -L L- -L _-L_ o position (%arc)loadd pad Figur 10. Loadd Pad Tmpratur Profils, LOp, 320 PSI, 9000 RPM. Pad SUifac Isothrms Bfor any comparisons ar mad, it is usful to look at th ntir pad surfac profil. This is gnratd by curv fitting data from th array of thrmocoupls in th loadd pad surfac. Figur II is an isomtric viw of th loadd, cntr pivot pad. Figur 12 is th sam data looking dirctly at th babbitt fac. Figurs 13 and 3 3

5 A STUDY OF PARAMETERS THAT AFFECT PIVOTED SHOE JOURNAL BEARING PERFORMANCE IN HIGH-SPEED TURBOMACHINERY ar similar plots for th loadd, offst pivot pad undr idntical conditions of load, spd, and oil flow. Th surfac tmpratur profils ar important in that thy show if th pad is alignd with th shaft or if thr is dg or skw loading that can distort comparisons and lad to rronous conclusions. Th symmtric pattrns of Figurs II through 14 indicat good axial alignmnt btwn th loadd pad and shaft, which is attributd to th alignmnt capability of th rolling contact pivot dsign. Anothr obsrvation is that thr is a fairly substantial axial tmpratur gradint noticabl in th figurs. Tmpratur drops 15 to 20 D (59 to 68 D F) from th cntr hot spot to th sids of th pad for th oprating conditions shown. ilil-:135! i L'i! 125-; '11!l-125: L'i! : ; ':=i i id I!O if] id80-85, i El75-80 I Iii! -75 1l11li65- :1I!I-65 I 1 l1li 55- i Figur 11. Cntr Pivot Pad Suifac Isothrm, Isomtric, LOP, 320 PSI, 9000 RPM. :-D-135-! 1II1II I Gill !1J115-! IIi!l SE I EiiJ ! f! I i I Ci ' E I '0 ; &. li!il 75-80,: Gill -75 i l1li65- igill-65 i I Gill 55-, ' i O:.2 J Figur 12. Cntr Pivot Pad Surfac Isothrm, Plan Viw, LOp, 320 PSI, 9000 RPM. Pad Tmpratur Comparisons, Cntr Vrsus Offst Pivot A study of pad surfac isothrms indicatd that th pads wr alignd with th shaft, and that pak tmpraturs wr locatd along th circumfrntial cntrlin for th conditions tstd. With this assuranc, cntrlin pad tmpratur profils can b usd to provid an accurat indication of th highst pad tmpraturs. Figurs 15 through 17 ar pad tmpratur profils for a loadbtwn-pad (LBP) orintation whr th tst load is applid dirctly btwn th two bottom pads. LBP pad tmpratur rspons is similar to th LOP data of Figurs 7 through 9 in that as spd and load ar incrasd, th loadd pad tmpraturs also ii!!l--;35i 135! 1iII125-! Iliil-125i jill! ilill !Cci [ : i!::l ! 'IU95-100' ! : [] I'] I-, 'tl ii2l75-80 &. I Ill! I!III i IU55- I LiII -55 _J Figur 13. Offst Pivot Pad Suifac Isothrm, Isomtric, LOp, 320 PSI, 9000 RPM. SE.a l11li125-:!ill -125!Jl! 115-; :&\l ! : Ell ' -: r: <l> i:j : E ill [] I- " <U n.! & Ill! -75,11165-, 1IlI-65 'l1li55 lq:!5!5._ Figur 14. Offst Pivot Pad SUifac Isothrm, Plan Viw, LOp, 320 PSI, 9000 RPM. incras. For LBP orintation, it is notd that th scond loadd pad in dirction of rotation runs hottr than th first loadd pad, Th ffct is most noticabl at th highr load and spd. This is attributd to hot oil carryovr. That is, a pad's tmpratur is influncd by oil from th prcding pad. Th unloadd pad prcding th first loadd pad has rlativly cool tmpraturs. Th scond loadd pad is influncd by much hottr oil from th first loadd pad. And so, for LBP orintation, th scond loadd pad tmpratur bcoms th limiting factor. Figur 18 compars scond loadd pad tmpratur profils for th cntr and offst pivot dsigns. StUdying LOP Figurs 7 through 9 and LBP Figurs 15 through 17, similar trnds can b dtctd for th cntr and offst pivot dsigns and for LOP and LBP orintation. Excpt at th lowst spd and load whr tmpratur profils ar fairly lvl, tmpraturs for all pads ar lowst at th lading dg and incras toward th trailing dg. Th tmpratur lvls of all pads, and th tmpratur gradint from lading to trailing dg of all pads incras with spd. Th tmpratur lvls and gradint of th loadd pads incras with load. Othr trnds obsrvd in this study ar difficult to show in th fw, rducd figurs. A minor rduction in unloadd pad tmpraturs was noticd with incrasd load. Th hottst tmpratur location of th loadd pads movd toward th trailing dg as spd was incrasd. This trnd is rvrsd for incrasd load.

6 14 PROCEEDINGS OF THE 30TH TURBO MACHINERY SYMPOSIUM Cntr Pivot [gjj Offst Pivot J , : 110 :l f 100 Co " 80 LBP Load Btwn Pads Baring Load I 0. F==========:@ Rotation position (dg.) Figur 15. Pad Tmpratur Profils, LBP, 200 PSI, 1800 RPM. 140 fl : 110 :l 100 " Co I- " "0 0. " 80 + Cntr Pivot III Offst Pivot )J. +co.. jj position (dg.) Figur 16. Pad Tmpratur Profils, LBP, 200 PSI, 9000 RPM. Cntr Pivot III Offst Pivot 140 r / position (dg.) nd loadd pad Figur 17. Pad Tmpratur Profils, LBP, 320 PSI, 9000 RPM. Diffrncs btwn cntr and offst pivot tmpraturs ar also noticabl in Figurs 7 through 9 and 15 through 17. In all cass, th offst pivot runs with coolr ovrall pad tmpraturs, particularly noticabl on th loadd pads. Figur 10 for LOP and Figur 18 for LBP focus on th hottr, loadd pad. For th cntr pivot, th pad tmpratur is noticd to incras to a maximum at a position of 82 and 89 prcnt of th arc lngth for LOP and LBP, rspctivly, aftr which it falls to a lowr lvl. For th offst pivot Cntr Pivot III Offst Pivot 140r ,_ , position (%arc) 2nd loadd pad Figur 18. Loadd Pad Tmpratur Profils, LBP, 320 PSI, 9000 RPM. dsign, th pad tmpraturs rach a maximum clos to th trailing dg of th pad. Ths obsrvations ar consistnt with 3.88 inch diamtr rsults in arlir work by th authors (Brockwll, t ai., 1994). For th rang of loads and spds tstd, th cntr pivot maximum tmpratur varid btwn th 65 prcnt and 90 prcnt location. Th offst pivot maximum tmpratur varid btwn th 82 prcnt location and trailing dg. Th spcific location of th maximum tmpratur varid with spd and load. To furthr rduc th data for gnralizd comparison, it is hlpful to viw a singl location. Th 75 prcnt position is a typical location usd in industry (Nicholas, 1994) and is rcommndd in many spcs such as Amrican Ptrolum Institut (API). With th ntir profil masurd in dtail, and data showing diffrnt maximum tmpratur locations for th cntr and offst pivot dsigns, som authors choos to compar maximum masurd tmpraturs (Simmons and Lawrnc, 1996). Figurs 19 through 22 compar 75 prcnt location and maximum tmpraturs for LOP and LBP orintation at 100 prcnt of rcommndd flow. Th spd rang for ths comparisons was limitd bcaus th lubrication systm could not provid th rcommndd flow for highr spds. Howvr, tsts wr also prformd with prcnt flow, shown in Figurs 23 and , , - Cntr Pivot... Offst Piv ot i u 110 ::s 100 (]) Co (]) I- -g 80 c.. o Figur Prcnt Location Pad Tmpraturs, LOP Th chang in slop and inflction noticabl in Figurs 23 and 24 indicat that th spd rang covrs laminar, transitional, and turbulnt oprating conditions. Figurs 19 through 24 show that th offst pivot dsign has lowr 75 prcnt location and lowr maximum tmpraturs than th cntr pivot dsign for all conditions

7 A STUDY OF PARAMETERS THAT AFFECT PIVOTED SHOE JOURNAL BEARING PERFORMANCE IN HIGH-SPEED TURBOMACHINERY , u 110 ::l... C I- "C 80 <U Cntr Pivot... Offst Pivot Figur 20. Maximum Pad Tmpraturs, LOP. 140, , Q: 110.a I!! C. - I- "C 80 <U Cntr Pivot... Offst Piv ot _...8 <::::r Q---1T.,..,p Figur Prcnt Location Pad Tmpraturs, LBP , , - Cntr Pivot... Offst Pivot u 110 ::l 100- C. - -g , ----, , ,---_,----,_-- o Figur 22. Maximum Pad Tmpraturs, LBP. tstd. Th 75 prcnt location tmpraturs ar as much as 20 C (68 F) coolr, and maximum tmpraturs ar up to looc ( F) coolr than th cntr pivot pad tmpraturs. Th bnfit is noticd to improv with spd and load, and xtnds through th laminar, transitional, and turbulnt rgims of opration. 140-, _ - Cntr Pivot... Offst Pivot Q: 110.a I!! 100 C. 0'- - "C 80. "g.'.,- -f.y ".G"' " +---_.----,_--_,----,----,----,_---- o Figur Prcnt Location Pad Tmpraturs, LOp, Prcnt Flow. 140, , - Cntr Pivot... Offst Piv ot u ::s I!! 100 C1>,.' c. - C1> I- "C 80 <U (J.'"", Figur 24. Maximum Pad Tmpraturs, LOp, Prcnt Flow. Powr Loss Comparisons, Cntr Vrsus Offst Pivot Powr loss using frictional torqu masurmnts ar compard in Figurs 25 and 26 for slct cass of load orintation and flow. Ths figurs ar rprsntativ of th cass studid. For 100 prcnt flow (Figur 25), thr was a slight but noticably highr powr loss for th offst pivot dsign, which is consistnt with thory. Coolr tmpraturs hav highr oil viscositis and, thrfor, mor frictional drag. In th cas of prcnt flow (Figur 26), thr was no masurabl diffrnc in powr loss btwn th offst and cntr pivot dsigns. It may b that th highr pad tmpraturs ngat any masurabl diffrnc. Considring all tst cass, a fair conclusion is that offst pivot powr losss wr th sam to slightly highr than th cntr pivot dsign. Rducd Oil Flow Figur 27 compars th ffcts of rducing oil flow by prcnt for th cntr pivot LOP configuration. On would xpct pad tmpraturs to incras with rducd flow across th rang of conditions. Howvr, Figur 27 shows that only highr spd trn praturs ar affctd, a phnomnon also notd by DChoudhury and Mastrs (1983). Th authors hav similar xprinc in indpndnt thrust baring tsts. Spcifically, som variation in pad tmpratur with flow at low spd, an intrmittnt rang whr flow has littl ffct, and a significant variation of pad tmpratur

8 16 PROCEEDINGS OF THE 30TH TURBOMACHINERY SYMPOSIUM , I/) I/).3 40 o Cntr Pivot... Offst Pivot B that as it may, th purpos of th work is to improv baring limitations. Flow rduction for th cntr pivot dsign is inappropriat bcaus pad tmpraturs (Figur 27) ar alrady high. Howvr, th lowr tmpraturs of th offst pivot dsign may allow for an improvmnt in fficincy with rducd oil flow. With cntr pivot pad tmpraturs as a baslin, Figur 28 compars th ffcts of dcrasing th offst pivot baring oil flow for a LOP orintation at 320 psi projctd load and 10,6 rpm. For a prcnt rduction in flow, th offst pivot loadd pad tmpraturs incras fairly vnly from lading to trailing dg, such that th ntir pad is running approximatly loo ( F) hottr. With prcnt flow, th offst pivot 75 prcnt location is still coolr than th cntr pivot baslin, but th maximum pad tmpratur is hottr. Th qustion as to which comparison should b usd to judg th two dsigns bcoms mor rlvant.... cntr pivot 100% flow o Figur 25. Cntr Vrsus Offst Pivot Powr Loss, LOP, 100 Prcnt Flow. 80, ,.. I/) Q) I/) J :: Cntr Pivot... Offst Piv ot o Figur 26. Cntr Vrsus Offst Pivot Powr Loss, LEP, Prcnt Flow. 140, Q: 110 l!! 100 Q) Cntr Pivot, 100% Flow... Cntr Pivot, % Flow 140 r otffstpivot5o%flow_, i... qffst pivot 100% flow ----_ -' " ! lid! E 100 " " Co -g 80 Q. i I i _+7"" r i - L- _L L L o position (%arc) loadd pad Figur 28. Effcts of Flow on Loadd Pad Tmpratur Profils, LOp, 320 PSI, 10,6 RPM. In th authors' xprinc, both ar important. Maximum pad tmpratur is of concrn in rgard to th oil, whr additivs and bas stock can brak down or dposit on th pad surfacs causing baring tmpraturs to incras ovr tim. In rgard to th baring, th 75 prcnt location is a gnral ara known from xprinc to suffr distrss undr advrs conditions. This is typifid by Figur 29, which shows mchanical fatigu of th babbitt nar th 75 prcnt location of a cntr pivot pad. Th 75 prcnt location is only a rul-of-thumb. Th actual location changs with load and spd and is also influncd by othr paramtrs. A tchnically valid comparison rquirs an analysis of prssur and tmpratur rlatd to mchanical critria for th babbitt. On mthod usd by th authors is as follows: -g 80 o Figur Prcnt Location Pad Tmpraturs, LOp, Vrsus 100 Prcnt Flow. with flow at high spds. Ths appar to coincid with th laminar, transitional, and turbulnt film rgims. And so it would sm that th obsrvd phnomnon is associatd with film turbulnc. Figur 29. Mchanical Fatigu on a Cntr Pivot Pad. rt

9 A STUDY OF PARAMETERS THAT AFFECT PIVOTED SHOE JOURNAL BEARING PERFORMANCE IN HIGH SPEED TURBOMACHINERY 17 Figur 30 is a plot of yild point vrsus tmpratur basd on data from ASTM-B23 for grad 2 babbitt. In th normal rang of baring oprating tmpraturs, th yild point is approximatly 4000 psi at C (I58 F), and rducs to 2000 psi at C (266 F). Th purpos of th figur is to stablish a matrial rfrnc point to judg th two dsigns Q. -; til 3000!l ASTM 8-23 Grad 2 Whit Mtal Yild Point (O.125% of Gag lngth) o ,----. o M W M 1W Tmpratur (C) Figur 30. Babbitt.125 Prcnt Offst Yild Point. Figur 31 plots th calculatd prssur profil and curv-fittd masurd pad tmpraturs for th cntr pivot pad of Figur 28. Notic that th paks occur at diffrnt locations such that at pak tmpratur, th prssur on th babbitt is vry low and at pak prssur, th tmpratur is low. Figur 32 is a similar plot for th offst baring with prcnt flow. By comparing th prssur and tmpratur to th babbitt yild point, th condition along th pad arc can b valuatd. For xampl, from Figur 31 at th 52 prcnt location, th film prssur and tmpratur ar 1400 psi and 91 C (195.8 F), rspctivly. From Figur 30, th yild point at 91 C (195.8 F) is 3200 psi. Th ratio of th film prssur to yild point is 1400/3200 psi =.46 for this location. By rpating this procdur for ach position along th pad, a map of th prssur to yild ratio can b gnratd as shown in Figur 33. Th closst approach to th yild point is found at th 62 prcnt location for th cntr pivot dsign, and at th 82 prcnt location for th offst pivot dsign. Th highst ratio for ach is approximatly.47 or, in othr words, both hav a worst cas prssur location that is 47 prcnt of th babbitt yild point. Prssur (psi) II1II Tmpratur (C) 140 Q: '" C. E ll 90 ll 80 I- Prssur Profil Tmp, Profil i1l 7 D. --, ,--O position (% arc) loadd pad Figur 31. Cntr Pivot Loadd Pad Prssur and Tmpratur Profils, 100 Prcnt Flow. Th comparison shows that th offst pivot baring running with prcnt flow and th cntr pivot baring running with ill Prssur (psi) r:il Tmpratur (C) 140, Q: 110.a E 80 Prssur Profil i1l 7 D ,--,--,--0 o position (% arc) loadd pad Figur 32. Offst Pivot Loadd Pad Prssur and Tmpratur Profils, Prcnt Flow : 0.80 '8. 0. '0 ]! 0. > 'w C.OAO E 'i: 0.30 g 0.20 ns!r f--. I I. J Cntr Pivot, 100% flow 1:_. Offfit P;"'tj='n-- --_. : L --'L 1- K' -. '... - "'-.,/ /1-'"'. 1\ A'" <'".'\,\ \ / '1'--- \ :::--- 1, o position (% arc) Figur 33. Ratio of Film Prssur to Babbitt Yild Point, LOp, 320 PS1, 10,6 RPM. prcnt flow ar quivalnt in rgard to th intgrity of th babbitt for th oprating condition shown. This xrcis also brings out two important points. First, th closst approach to th yild point occurs at a location bfor th pak tmpratur. Scond, this location is quit diffrnt btwn th offst and cntr pivot dsigns, and is not obvious from th tmpratur profils of Figur 28 alon. To complt th study on improving fficincy, Figur 34 compars powr loss for th offst pivot pad with prcnt flow to th cntr pivot pad with 100 prcnt flow. Thr is a rduction in powr loss on th ordr of 10 to 20 prcnt, which provids a small incras in machin fficincy. With rducd flow, th offst pivot baring's oil outlt tmpraturs ar 5 C (41 F) highr (Figur 35). Th highr outlt tmpraturs would nd to b chckd to assur thy ar still within accptabl spcification limits. (Plas not that this sction compars only on tst condition, and is not intndd as rcommndation to rduc flow by prcnt in all applications.) LOP Vrsus LBP Orintation Whn a LOP baring application is running hot, it is straightforward to assum that rorinting th baring for LBP will significantly rduc pad tmpratur, bcaus th load would thn b shard by two shos. In a fiv-pad baring, th unit pad load is rducd 38 prcnt going from LOP to LBP orintation. Howvr, arlir figurs indicat that th scond loadd pad ran up to l2 C (53.6 F) hottr than th first loadd pad in LBP tsts.

10 ]8 PROCEEDINGS OF THE 30TH Tl'RBOMACHI:\ERY SYMPOSIUM (/j (/j J t o - Cntr Pivot... Offst Pivot,',.0 -' -,"If" Figur 34. Powr Loss-Cntr Pivot 100 Prcnt Flow Vrsus Offst Pivot Prcnt Flow. 90-, , Q: 75 :::> E o - Cntr Pivot... Offst Pivot Figur 35. Drain Tmpratur-Clltr Pivot 100 Prcnt Flow Vrsus Offst Pivot Prcllt Flow. Figur 36 compars tmpratur profils for LOP and LBP orintations for th cntr pivot baring at idntical oprating conditions. It is noticd that th hottst pad tmpratur for ach orintation rachs similar lvls, just abov looo (212 F). In othr words, thr is not a significant rduction in pad tmpratur going from LOP to LBP orintation for th cas shown. Figur 37 compars pad tmpratur profils of th LOP loadd pad with th LBP scond loadd pad. Thr is littl diffrnc in pad tmpratur profil btwn th two orintations. Figur 38 plots cntr pivot 75 prcnt location pad tmpraturs, and Figur 39 plots offst pivot powr loss masurmnts comparing LOP and LBP prformanc. Ths figurs wr chosn to rprsnt gnral obsrvations of a study of all oprating conditions tstd that includ cntr and offst pivots at various flows and ovr a rang of oprating loads and spds. LBP orintation in most cass ran with lowr pad tmpraturs than th LOP configuration, but not as much as would b xpctd. This is attributd to th ffcts of hot oil canyovr. In gnral, th tmpratur bnfits of LBP orintation improv with load and spd. In rgard to powr loss, thr was no masurabl diffrnc btwn LOP and LBP orintation (Figur 39) E " 100 c. " f- " -g 80 l- f LOP Q L B P 0- A. r LOP loadd pad LBP 2nd loadd pad!s rp 1/ I position (d g.) Figur 36. LOP Vrsus LBP Pad Tmpratur Profils, 200 PS1, 77 RPM, Prcnt Flow. LOP ( 1 st pad) Q L B P ( 2nd pad) 140, : 110 " f 100,! position (%arc) Figur 37. LOP Vrsus LBP Loadd Pad Tmpratur Profils, 200 PS1, 77 RPM, Prcnt Flow. Q: :::>... r: 0- E I- "0 co 140, LOP (1st pad)... LBP (2nd pad)!!, psi o Figur Prcnt Location Loadd Pad Tmpraturs, Cntr Pivot, Prcnt Flow. FLOODED VERSUS DIRECT LUBE TEST DATA AND DISCUSSIONS This sction compars th ffcts of dirct lubrication and discharg configuration. As mntiond arlir, th trm "floodd"

11 A STUDY OF PARAMETERS THAT AFFECT PIVOTED SHOE JOURNAL BEARING PERFORMANCE IN HIGH-SPEED TURBOMACHINERY n n o 30 c o 1 - Offst Pivot, LOP... Offst Pivot, LBP ::-_.----;=-5OP:SI -J o Figur 39. Powr Loss-Offst Pivot, LOP and LBP, Prcnt Flow. rfrs to a mthod of lubrication. For th floodd dsign tstd, oil is providd to th baring btwn th pads and th discharg is rstrictd by labyrinth sals, which provids oil to th journal surfac by flooding th spacs btwn pads (Figur 40). Ladingdg-groov is a mthod of lubrication that provids oil dirctly to th journal surfac at th ntranc to th oil film (Figur 41). In both of ths mthods, th principls of hydrodynamic opration ar th sam. Spcifically, th journal drags oil into th spac btwn th journal and baring pads. Floodd Oil outlt Evacuatd Opnd Sal Claranc Figur 40. Discharg Configuration, Floodd Vrsus Evacuatd. Convntional j\ / \ % offst / ' (offst PiV/"_6_. \ /-'. -j. /c:tj/< Oil inlt 0 '" i-'; Pivot LEG Pivot Figur 41. Mthod of Lubrication, Convntional Vrsus Dirct Lub. In th cas of dirct lubrication, it is dsirabl to allow th hot oil to xit frly from th baring to rduc parasitic losss and fficintly rmov hat. Thr ar a fw diffrnt mthods for vacuating th baring cavity. For tst data rportd in this papr, th labyrinth sal clarancs wr nlargd (Figur 40). This is a most fficint mthod bcaus th sid lakag (xiting oil) is dischargd btwn th nd sals and shaft without bing capturd and rcirculatd within th baring. Not that in ths comparisons, two paramtrs ar changd-th mthod of lubrication and th discharg configuration. Othrwis, th floodd and LEG barings ar th sam. Th pads hav prcnt offst pivots (Figur 41), and data ar compard undr idntical oprating conditions and oil flow. Convntional (Floodd) Vrsus LEG (Evacuatd) Figur 42 compars convntional, floodd baring pad tmpratur profils to dirct lub, vacuatd pad tmpratur profils at conditions of 320 psi and 10,6 rpm. Th dirct lub dsign has noticably lowr pad tmpratur lvls, spcially at th lading dgs of th pads. This is attributd to providing cool oil dirctly to th lading dg, which affcts th ntir loadd pad (Figur 43). Comparing 75 prcnt location tmpraturs for 200 psi in Figur 44, and 320 psi in Figur 45, this bnfit is notd to improv with load and spd, up to 16 C (.8 F) coolr at xtrm tst conditions. It is also noticd that th diffrncs bgin around th turbulnt transition, vidnt by th inflction in th curvs. This sms to ti in with th bhavior of pad tmpratur and flow with turbulnc discussd in th rducd oil flow sction of this papr. [J Conv. floodd LEG vacuatd 140, , : 110 :J 100 C ' -0. L L L L o position (dg.) Figur 42. Pad Tmpratur Profils, LOp, 320 PSI, 10,6 RPM, Prcnt Flow. 140 : llo! i {!. 80 Conv. floodd LEG vacuatd It-... I---- f--- y l-----' V J-- L---- 1/ / V -'l- V) I position (%arc) loadd pad Figur 43. Loadd Pad Tmpratur Profils, LOP, 320 PSI, 10,6 RPM, Prcnt Flow.

12 20 PROCEEDINGS OF THE 30TH TliRBOMACHINERY SYMPOSIUM 140 'I I Cony. Floodd [... LEG yacuatd j u_ 110! 100 c _ a -- _---cr Q- -, _r------_,----_r o Figur Prcnt Location Pad Tmpraturs, LOp, Prcnt Flow, 200 PSI , -- Cony. Floodd... LEG vacuatd : 110! ::l... I!! II) c.,-- (!!.../Q-' 't) os 80 0,.., Figur Prcnt Location Pad Tmpraturs, LOp, Prcnt Flow, 320 PSI. Figur 46 compars powr losss for th two dsigns. Powr loss in th vacuatd, dirct lub baring masurd significantly lowr than th floodd baring dsign, on th ordr of 45 prcnt at xtrm oprating conditions. Rsulting oil drain tmpraturs ar plottd in Figur 47. It is noticd that th floodd dsign oil outlt tmpraturs ar vry high, xcding typical spcification limits at th highr spds. Th vacuatd, dirct lub dsign oil outlt tmpraturs ran up to 15 C (59 F) coolr, and support th rduction in powr loss from masurd torqu. As with pad tmpraturs, a study of powr loss and oil outlt tmpraturs indicats that th bnfits improv with incrasd spd and load. Effcts of Discharg Configuration on Dirct Lubrication To distinguish btwn th ffcts of dirct lubrication and vacuatd discharg, dirct lub tsts wr also prformd in a floodd configuration with rstrictiv labyrinth sals. Pad tmpratur rsults ar ovr plottd in Figur 48. In th floodd condition, th dirct lub loadd pad tmpraturs incrasd to a lvl btwn th LEG vacuatd and convntional floodd baring dsigns. Basd on this and comparisons of othr tst conditions, part of th dirct lubrication pad tmpratur rduction is attributd to th mthod of lubrication, and part is attributd to th discharg configuration. 80, , - Cony. floodd... LEG vacuatd - II) II) J "- II) ;;: o ,---_, ,_----._-- o Figur 46. Powr Loss-Convntional (Floodd) Vrsus Dirct Lub (Evacuatd), Prcllt Flow. 90., Conv. floodd LEG vacuatd 80 : 75 -! ::J (!) c. 65- I o Figur 47. Oil Outlt Tmpraturs-Convntional (Floodd) Vrsus Dirct Lub (Evacuatd), Prcnt Flow. 140, ,.: " c. -g Cony. floodd.fi!i. LEG floodd... LEG vac position (%arc) 2nd loadd pad Figur 48. Affcts of Oil Discharg Rstriction on Dirct Lub Pad Tmpratur. Rsulting powr losss ar compard in Figur 49, which also shows an incras to a lvl btwn th LEG vacuatd and convntional floodd baring losss. Th data indicat that a significant portion of th powr loss rduction is du to th discharg configuration, and a smallr portion to th mthod of lubrication.

13 A STUDY OF PARAMETERS THAT AFFECT PIVOTED SHOE JOURNAL BEARING PERFORMANCE IN HIGH-SPEED TURBOMACHINERY (f) (f) J 4- Conv. floodd G LEG floodd 30 - <II- LEG vac. II j/'/ /1 i 0 c... I 20 "F I I Figur 49. Affcts of Oil Discharg Rstriction on Dirct Lub Powr Loss. SUMMARY Rturning to th original purpos of th work, th tsts wr undrtakn to improv th capacity and prformanc of high-spd turbomachinry by xtnding baring spd and/or load limitations and improving fficincy. Extnsion of spd and load capability is accomplishd by paramtrs that rduc baring tmpraturs. In this rspct, th offst pivot rducs tmpraturs. Rfrring to Figur 19 for a comparativ xampl (say a 100 C (212 F) tmpratur limit and 320 psi load) th offst pivot can xtnd th application's spd to 11,000 rpm compard to th cntr pivot, which rachs 100 C (212 F) at approximatly 00 rpm. For a constant spd, say 11,000 rpm, th offst allows loads on th ordr of 320 psi whr th cntr pivot dsign is at 200 psi. In rgard to improving machin fficincy, this can b attaind by rducing oil flow and powr loss, xplaind arlir with Figur 34. Bcaus of th lowr pad tmpraturs, it is possibl to rduc oil flow in th offst dsign without jopardizing th intgrity of th babbitt. This is accompanid by a small incras in machin fficincy, on th ordr of 10 to 20 prcnt. With rducd flow, th oil outlt tmpraturs ar highr and nd to b chckd to assur that th lvls do not xcd accptabl limits. Tmpraturs ar furthr rducd in th dirct lub dsign (Figurs 44 and 45). Continuing th xampl, th LEG vacuatd dsign allows for 320 psi opration to 15,000 rpm compard to th convntional floodd dsign which rachs 100 C (212 F) at 9000 rpm (both with prcnt flow). For fficincy, dirct lubrication with an vacuatd discharg configuration can attain most significant rductions in powr loss, on th ordr of 45 prcnt (Figur 46), with lowr pad tmpraturs as wll as a significant rduction in oil outlt tmpratur (Figur 47). Th rductions in powr loss ar significant nough to allow an additional bnfit considring dsign for a smallr lubrication systm. CONCLUSIONS Convntional (Floodd) Barings This sris of tsts was prformd with convntional, floodd pivotd sho journal barings to compar th ffct of pad pivot location on baring prformanc. Th pivot locations tstd wr cntr ( prcnt) and offst ( prcnt). Othr than th location of th pivot, baring gomtry for th two sts of pads was idntical. Th barings wr tstd in LOP and LBP configurations. Conclusions arising from ths tsts ar as follows: Cntr Pivot Vrsus Offst Pivot o Cntr pivot maximum tmpraturs occurrd btwn th 65 prcnt and 90 prcnt location. Offst pivot maximum tmpraturs occurrd btwn th 82 prcnt location and trailing dg. As spd incrass, th hottst tmpratur location of th loadd pads movs toward th trailing dg. Th trnd is rvrsd for incrasing load. Th offst pivot dsign ran coolr in all cass tstd, as much as 20 C (68 F) lowr than th cntr pivot dsign. Th bnfit improvd with spd and load. Offst pivot powr losss wr th sam to slightly highr than th cntr pivot pad. Effcts of Rducd Flow Offst pivot dsign oil flow can b rducd without jopardizing th intgrity of th babbitt compard to a cntr pivot dsign at similar oprating conditions. Rducing th flowrat to th offst pivot baring by prcnt rducd powr losss 10 to 20 prcnt. This provids a small incras in machin fficincy. For conditions tstd, oil outlt tmpraturs ran 5 C (41 F) highr with a prcnt flow rduction. LOP Vrsus LBP Orintation For LBP orintation, th scond loadd pad ran up to 12 C (53.6 F) hottr than th first loadd pad. This is attributd to hot oil CalTyovr. Th LBP orintation in most cass ran coolr than LOP, but not as cool as xpctd, which is also attributd to hot oil carryovr. Th bnfits of LBP orintation improv with load and spd. Thr was no masurabl diffrnc in powr loss btwn LOP and LBP orintation. Floodd Vrsus Dirct Lltbrication This sction compars th ffcts of dirct lubrication and discharg configuration. Th convntional, floodd baring has oil discharg rstrictd by labyrinth sals. Th dirct lub LEG dsign is tstd with two discharg configurations dscribd blow. Othr than this, th two barings ar of th sam gomtry and compard at idntical oprating conditions and oil flow. Convntional Floodd Vrsus Dirct Lub (Evacuatd) In ths comparisons, th dirct lub baring has an vacuatd discharg configuration via larg claranc nd sals. Dirct lubrication with an vacuatd discharg dsign has significantly lowr pad tmpratur, powr loss, and oil outlt tmpratur. At xtrm conditions, pad lading dg tmpraturs wr significantly coolr than th convntional, floodd dsign. (I Dirct lub, 75 prcnt location pad tmpraturs ran up to 16 C (.8 F) coolr than th floodd baring at xtrm oprating conditions. Maximum pad tmpraturs wr as much as 12 C (53.6 F) coolr. (I Th dirct lub dsign with an vacuatd discharg rducs powr loss on th ordr of 45 prcnt compard to th convntional, floodd dsign. Oil outlt tmpraturs wr up to 15 C (59 F) coolr. Th pad tmpratur and powr loss bnfits improvd with incrasd spd and load. Dirct Lub (Floodd) Vrsus Dirct Lub (Evacuatd) In this sction, th ffcts of oil discharg configuration on dirct lub prformanc wr compard. Th LEG floodd discharg configuration had th oil discharg rstrictd by

14 22 PROCEEDINGS OF THE 30TH TURBO MACHINERY SYMPOSIUM labyrinth sals. Th LEG vacuatd discharg configuration had larg claranc nd sals. Th conclusions ar: Part of th rduction in LEG pad tmpraturs is du to th dirct lub dsign, and part is du to th vacuatd discharg configuration. A significant portion of th powr loss rduction is attributabl to vacuation of th housing, and a smallr portion to th mthod of lubrication. ADDITIONAL COMMENTS Data containd in this rport show th ncssity to considr othr parasitic losss (such as churning and sal losss) in computr modls. Parasitic influncs ar discussd by many authors (.g., Boosr, 1990), and ar rquird to prdict th highr losss in floodd dsigns, and th lowr losss in vacuatd dsigns. Othr phnomna mntiond throughout th papr nd to b bttr undrstood to dvlop accurat computr modls. A study of pad tmpratur profils can giv valuabl insight into hydrodynamic bhavior, and is ncssary for programming modls to accuratly prdict prformanc. Th surfac isothrms showing axial tmpratur gradints ar also usful data for program dvlopmnt. It is hopd that th information and high-spd data containd in this papr will nhanc th study and prdiction of baring prformanc in turbomachinry. REFERENCES Boosr, E. R., 1990, "Parasitic Powr Losss in Turbin Barings," STLE Tribology Transactions, 33, (2), pp Brockwll, K., Dmochowski, w., and DCamillo, S., 1992, "Prformanc Evaluation of th LEG Tilting Pad Journal Baring," I Mch E Sminar Plain Barings-Plain Barings-Enrgy Efficincy and Dsign, MEP, London, England, pp Brockwll, K., Dmochowski, W., and DCamillo, S., 1994, "Analysis and Tsting of th LEG Tilting Pad Journal Baring-A Nw Dsign for Incrasing Load Capacity, Rducing Oprating Tmpraturs, and Consrving Enrgy," Procdings of th Twnty-Third Turbomachinry Symposium, Turbomachinry Laboratory, Txas A&M Univrsity, Collg Station, Txas, pp DCamillo, S. and Clayton, P. J., 1997, "Prformanc Tsts of an 18-Inch Diamtr, Lading Edg Groov Pivotd Sho Journal Baring," Procdings of th Scond Intrnational Confrnc on Hydrodynamic Baring-Rotor Systm Dynamics, Xi' an, China, pp DChoudhury, P. and Barth, E. w., 1981, "A Comparison of Film Tmpraturs and Oil Discharg Tmpratur for a Tilting-Pad Journal Baring," ASME Journal of Lubrication Tchnology, 103, pp DChoudhury, P. and Mastrs, D. A., 1983, "Prformanc Tsts of Fiv-Sho Tilting-Pad Journal Baring," ASLE Transactions, 27, (1), pp Dmochowski, w., Brockwll, K., and DCamillo, S., 1993, "A Study of th Thrmal Charactristics of th Lading Edg Groov and Convntional Tilting Pad Journal Barings," ASME Journal of Tribology, 115, pp Edny, S. L., Wait, J. K., and DCamillo, S. M., 1996, "Profild Lading Edg Groov Tilting Pad Journal Baring for Light Load Opration," Procdings of th Twnty-Fifth Turbomachinry Symposium, Turbomachinry Laboratory, Txas A&M Univrsity, Collg Station, Txas, pp Fillon, M., Bligoud, J. C., and Frn, J., 1993, "Influnc of th Lubricant Fding Mthod on th Thrmohydrodynamic Charactristics of Tilting-Pad Journal Barings," Procdings of th Sixth Intrnational Congrss on Tribology, Budapst, Hungary, 4, pp Gardnr, W. W. and Ulschmid, 1. G., 1973, "Turbulnc Effcts in Two Journal Baring Applications," ASME Papr No. 73-LubS-7. Harangozo, A. v., Stolarski, T. A., and Gozdawa, R. J., 1991, "Th Effct of Diffrnt Lubrication Mthods on th Prformanc of a Tilting Pad Journal Baring," STLE Tribology Transactions, 34, pp Nicholas, 1. c., 1994, "Tilting Pad Baring Dsign," Procdings of th Twnty-Third Turbomachinry SymposiulIl, Turbomachinry Laboratory, Txas A&M Univrsity, Collg Station, Txas, pp Pttinato, B. and DChoudhury, P., 1999, "Tst Rsults of Ky and Sphrical Pivot Fiv-Sho Tilt Pad Journal Barings-Part I: Prformanc Masurmnts," STLE Tribology Transactions, 42, (3), pp Pinkus, 0., 1990, Thrmal Aspcts of Fluid Film Tribology, Nw York, Nw York: AS ME Prss. Simmons, J. E. L. and Lawrnc, C. D., 1996, "Prfonnanc Exprimnts with a 200 mm, Offst Pivot Journal Pad Baring," STLE Prprint No. 96-AM-7B-4. Tanaka, M., 1991, "Thrmohydrodynamic Prformanc of a Tilting Pad Journal Baring With Spot Lubrication," ASME Journal of Tribology, 113, pp Tanaka, M. and Mishima, N., 1989, "Thrmo hydrodynamic Prformanc of a Spot-Fd Tilting Pad Journal Baring," Procdings of Eurotrib89, 3, pp Wygant, K. D., Flack, R. D., and Barrtt, L. E., 1999, "Influnc of Pad Pivot Friction on Tilting-Pad Journal Baring Masurmnts-Part I and Part II," STLE Tribology Transactions, 42, pp and ACKNOWLEDGEMENT Th authors sincrly thank all prsonnl at Kingsbury, Inc., and th National Rsarch Council of Canada, who contributd to th work documntd in this papr. Th authors ar gratful to Kingsbury, Inc., and th National Rsarch Council of Canada, for prmission to publish this information.