32 - 1985 - LEG Recent Developments

7/30/2019 32 - 1985 - LEG Recent Developments

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OATION

CONENTONASH DESIGN

g. Copaison of he oneniona an LEG shoe esgns

PressrzedSppy (Fooded) Bearng

Ths style of conventional thrust beang has been fullydescribed in reference 2] and other literature, bu a brief

description of ts lubricant supply metod shoud provebeneficial The bearing is supplied wit a specfic volume ofoil tha enters an annulus n e base ing From there, e oilflows adially inward throug slos n he back face of hebase ring and ten axially through the clearance between thebase ring bore and saft Wen he oi reaches the roatngthrus collar t is pumped radially ouward between the soesRotaion of the colla caries some of it into e oi film oneach shoe Due o he pumpng action of the collar, suppypressures of only 003-014 MP gage (-20 ps) are all ha isrequired As he oil ravels hroug he bearing t is warmedconsdeably, so ha ol supplied a 46C (F) s 4-60C(30-40F) by the time eners the oil flm wedges

Only a small porion of he oal oil flow supplied to thebearing (aound 10 percent) actually finds is way into the

hydrodynamic wedges 3]. Most of te oil is intended o beused for coolng of the beaing components. In the processhowever i ncreases the chuning osses around the collar Areduction in the volume of oil supplied wil heefore reducehe collar churning losses, but it will also reduce te beneficialcooling available whch wil be refleced by an increase inshoe babbit temperaures

Leadng-EdgeGroove (LEG) Bearng

The orginal design of the LEG bearing is descbed nreference ]. Since that time, further design efinemens havebeen introduced The LEG design inroduces cool, undlutedil drectly into he hydrodynamic wedge Tis intially coollayer in intimate conac with te shoe babbit resuls ndramatic temperaure reducions

The leading edge of he shoe is exended o accommodatethe distributon groove by the additon of nonloadcaryingareas as shown in Fig 2 A chamfe on he trailing edge sdeof he groove s used to facitate oil flow even wen te shoeconacs the collar such as an "at rest condition Tepressurized oil supply is diectly conneced at he OD. withte dstribution goove by means of an oi feed tube that sdesigned to provide a positve ing seal wile at esame me, allowing unencumbered shoe movement Tegroove is relieved to te .D o facilitae oil flow down thefull length of te groove Te oi path through the bearing wasredesigned to reduce inernal leakage and at e same timepressure dop These impovements have esulted in not onlyareduction of the oil supply pressue necessay to supply thedesignated amount of oil to the disribution grooves, but also

2 Vol 17 1985

Fig. 2 eangegegooe beaing showng the o ee tube

any oil leakage from e oil supply sysem before the oil enteshe distbution groove

Reverse Rotation

Orgnally, was staed ha the EG design precludesoperation in two directions of rotaon because of hedstribuon groove [1] Recent tests, wi e EG bearingpurposey insalled with the dsbution at the ralng edge,pove that e bearng can suppot oads up o 3.4 MP a (00psi wit some loss of efficiency Tese tests wll be detailed ina subsequent paper.

O Sppy Fo Rates

The influence of oil supply flow rates on rust bearingperformance as been found to be significant [1, 2] f powerloss is o be minmized, then so must oil flow raes (all otherhings being equal) Unfotunaely, he babbitt temperauresand safe load capacity of te bearing usually suffe as eflow aes are reduced Wh is adeoff n mind, the EGwas developed and laer refned in order to effectvey managereduced oil flows in such a way as to elimnate hs usualtradeoff.

The most ecent development work on te LEG desgndescribed in ts paper, has ceneed on two subjecs: 1) afurhe reduction in toal ol flow ates; 2) maximzing te oilflow trough the distrbuion groove and into he

ydrodynamic wedge.Oveall, oil flow raes o the EG beangs during te mosrecen testng wee educed by cutting back te slack bearingflows as sown in Fg 3 The rationale behnd his was a,because the dsbuton goove had poven so effecve apacing the oi ino he loaded beang's hydrodynamc wedge, soud be us as effecive n he slack sde beaing. Teslack bearng o flows were educed on a siding scale themaximum reducon occurng at noload and e minmumreducton at maximum load Figures 4 and show the loadedand slac beang o fow ates of ISO VG 32 lgt tubine oia loads of 207 and 3.4 MP (300 and 00 psi) Tess of teLEG beaing using heavy oi were only conduced wthreduced slack oil flows as shown in Fgs 6 and 7.

Desgn modificaons o the orignal LEG beaig wee

Tansactions of the


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R L VERGE OF MNMU AX VLESRSSRZED SPY-ODED BE

EG OR G LO D BR G EST ODE BRGESSRD SYSCK BEEG ORSLCK BRG E TS SK BERGOL 'S O G 3Zt 7.S' C

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Fg 3 A coprison o the verge o fow re suppied to echbering Ths verge ws coputed s foows:

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Averge o fow te

fow re t tested od = nube of ods ested fo ech shft speed M

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Fg. 4 A coprison of o fows o he indivdu thust beringswhen oded to 2.07 MP fon O VG 32 ubcn suppied 46

de to edce intern ekge nd ere dro toge erng. ee deign cnge ve reted n redctonin te y rere fro 0.10-0.1 MP gge (10 ig)to 0080069 MP gge (7 10 ig).

Bearing Operang Temperatures

erocoe dded n te t itef roitey08 (13 i ew te e ce e ed toere oertn eere. Secifc e o terocoe ceen e n erene ]. Soefce teee e c t e f octionnd od eqzton Acro te oe rfce tere eny eting teertre ec fnction of oction own in te tyc ret Fig 8 S vritin in te

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Fig. An Isother a 1012 n hrus bearing shoe loaded to 345MP at a shaf speed of 7000 pm, showing the tepeatue gadentacoss the shoe In degrees Fahenhet when using the ight ubine

HOES 75/7% LOCAION TE BEARIGO RESSURZE SUPY LEG-ORGA LE-LAES160 AD' 345MPq 0S)

I S O VG 327.8DC

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' 20 250 " '

0

200

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4 0 2 SAF SE, RM" 10

Fg A coparson o he hottest 75/75 pecent ocaion babbitemperatue for each Indvidua bearing hen oaded to 345 MP andusing an O VG 32 ubcan supped at 46'C

peratue etween soes of e same earing an also esulfom less an optimal load eualization

Bait temperaures sere as a onenient indiao ofoeall earing pefomane Baitt emperatures an eus o proide informaion egading a earings loadapity [4] load equalizaion and te ondition of eait itself

Two soe surfae emperaures are used to ealuate teelaive perfomane of ea eaing Te firs is temaximum measued ait temperaure regardless ofloation and te seond is te ottest "75-5 perenloaion found on any of te si eaing soes

Figues 9 to 12 illustrate e inuene at earing designas on empeature performane Figues 9 and 0 repot eemperature data olleted usng te lig tuine oil a aonsan load of 3. MPa 00 psi) and Figs 11 and 12 arefor te eaier oil at a onsan load of 2.07 MP a 300 psi)Te respetie oil flow rates were sown in Figs 5 and 6

Figure 9 ompares te ottest 55 peren loaiontemperatues for o te original and impoed LEG designand te onentional flooded design Bo LEG designs aea emperatue adantage oer e fooded earing until 1000

2 Vo 17 1985

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OES SRE EMPERARE I EARIG

O PRSSRED SPP LEORGIA LEG LAES6 LOAD 4 Mo 500 PSI

0

0 1 2SAF SE E R 0-

.

O

200

Fig 0 A coparison of the hotest easured babbitt epeaturesof ech indivdua bearng when oaded to 345 MP and using an OVG 32 ubricant suppied at 46C

O S 55-, OAIO I EARIGIO RSSURI ZED SUPLY 0 LEORGIA EGLAES

LOO 2.07 o (SIl0 OI 00 s fec

( SSU 00'F)00

' ! 20

10

0

2SAF SEED RPM 0 -

Fig 1 A coparison of the hottest 7575 percen ocaion babbttemperature or each ndivdua bearing when oaded to 207 P andusing a 0.067 s ubricant supped at 46C

OT ES MEASURED EMERAURE I E EARIG1 RESSRIZED SU LEGORGINAL LEAES

LOAO 2 o (00SI0 O 00 Po 7a

(75SSU@ 00F)

0

0

8

0SAF SPEE M x 0

& w

200

Fig. 12 A compason o he hottest easured babbitt tepeatuesof each ndividua bearing when oaded to 207 MP and using an OVG 32 ubcant supped at 4SC

Tnsctions of the


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EE PWE PRERIE Y300 EG RG EG E

2.01 a ( 3I 250 II VG 3238 00 '

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stanial power oss advantage of he EG design over theconventiona design is eviden The difference between theoriginal and latest EG designs is also evident The benefis ofimproved sealing and reduced slack bearing flows account forthe difference between he EG designs in Fig 13 while inFig 14, the difference is due solely to he improved sealing ofthe oil supply path The improved sealing reduced parasiticchurning losses hat result from lubricant hat is not supplieddirectly ino the oil film []

Figures 1 and 16 show he bearing power loss vauesmeasued for each bearing when the heavier oil was usedOnce again, the significant advantage approximaely a 0percent reduction) of he EG design over the conventionadesign is evident The difference between the two EG designscan only be due to the improved sealing of he oil supply pathincorporaed in the laes design because both were run withreduced slack side flows

Cocusos

The leading-edge-groove EG bearing demonsraedan abiliy o operate at oi fow rates tha were up to percent less than those suppied o he convenional flooded

thrust bearing wih the heavy oil These reduced oi owsproduced power loss savings as high as 6 percen Similar,although somewha less dramatic resus were produced wihthe ligher SO VG oil 66 percen oil flow and 4 percenpower loss reduction) While it is rue tha similar ow ratereductions to a flooded bearing would produce lower powerloss values, unaccepably higher bearing operaing emperaures resul

Improvements o he EG design hat reduced oil pathleakage resuled in furher power loss reducions in comparinghe present resuls to hose previously published [] Th EGdesign also proved capable of operaing wih reduced slackside bearing lows This resulted in additional power ossreductions

3 Shoe babbit temperaures for shaft speeds under 1000

DISCUSSI ON

F t _

The leadingedge groove bearing would appear o be mostsuitable for direc lubricaion in he pads with a freely drainedcasing was first envisaged that this was the topic of hethors paper since the absract refers to performance of heleding edge groove bearing design and constraststhe resulswith a pessurized supply bearing design On reading thepaper further i is undersood that the casing in these particular tests is subjected o supply pressures from 010 o 014MPa for the origina EG bearing ests and 0048 to 0069MPa for he latest EG results and that all tests were con-ducted with a discharge restriction. Te discusser is now ofhe optinion tha he auhors presen resuls all reate topressurized casing flooded) bearings f this is so it would beusefu to know the genea goba tempeatue ise though theassembly compared wih oher bearings

As commented on in previous papers the tests results forthe pressurized supply bearing without leading edge groove)used by the author relaes o a centrally pivoted bearing As

incipa Enginee, epamen of Appicaons EngineeingThe GacieMea Co d MddlesexHAO IHD Engad.

2 7, 85

rpm were found to be up to 20 percent lower with he Gdesign This is atributed to the introduction of cool, undiluted supply oil directly into the oil film wedge This cool oilis believed to insuate the shoe surface from the hot oil carryover adhering to the roating colar At sliding velocitiesabove 11000 rpm the combined effects of the significantEG oil low rate reductions and he turbulent oil film ow[ 8 9] in the conventional design produced mixed resultsReducions o he slack side bearing's oil fow rate generaly

produced no increase in shoe surface emperaures becausehis assembly was unloaded

Ackowlgm

The author wishes to express his graiude to Kingsbury,nc for the opporunity to publish hese results

Rfrcs

I Mika A. M and Gegoy R S. "A Copaso of Tiing PadThs Beang bican Sppy Mehods ASME JOUA OF UlRCnONECHNOLOGY, Yol 105 No. IJan. 983pp 3947

2 Gegoy R. S Pefoance of hs Beaings a High OpeaingSpeeds ASME OURNA > LUBATIN EHNOLOGY Yol 96, No Jan97 pp 74

Elwe

R.C st-Beaing Tepeae/Pa

Machin Dsgnne29, pp 8\4 Elwe R C., ThsBeang Tepeaue/Pa 2 Mahne DeignJy 81971 pp 9194

eopad A J Ths Bangs fo Powe Gas Tbines ASMEPape No 71GT-9971p. 6

6 Grgory R. S. Facos nencing Powe Loss of iingPad ThsBeaings, ASME JOURNAL OF LURICAnON CHNOLOGY Yo. 01 No 2Ap. 979pp 154162

7 Gegoy R. S, "Opeaig Chaaceisics of a Flid F ThsBeaing Sbjeced o High Shaft Speed Supramna w n BearngMechanical Engineeing Pbicatios d.ondon Englandp 14.

8 Capiao J W. Pefoance Chaaceisics of TilingPad TsBeangs a High Opeang Speeds ASME ORNA O UBIATIONHNOLOGY Yo 98No ,Jan 976 pp 8189

9 Sganai T, and Szei A Z A Theohydrodynamic Aaysis ofJoa Beag ASME ON O RCAT EHNOOG Yo 0No I,Jan 979pp217

he EG bearings have offset pivots it would appear moreappropriae o compare hem with oher offset pivot bearingsraher than with the specia case of cenrally pivoed bearingswhich must have different performance characeristics theater reying on the crownng of the pad by machining

thermal and elastic disorion for successful operation Theauhors experimenta results are always a welcome input to

the literature However, does the pivot position cloud thecomparison of resuls and are hese particular EG ests for anominally pressurized casing?

W Gd

As he author indicaes, the present paper is a supplementto an eaier paper [1], both giving test results of the leadingedge-groove bearing as compared to a convenional designn he present paper, as in he discussion o the first paper, itis noed that he EG bearing uses circumferentially offsepivots 06) as compared to center pivots 0) for he con

venional bearing

Yice Pesden Engineeing Wakesha Beangs Cop. WakeshaWisc587

ransactions o the


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(a)-CENTER PIVO (0,5)b)OFFSE PIVO .6)

310 MPa 40 S) UNT LOADING5'C13) IETSO V32 OI

RPM THUSAND

Fig A A compson o e ge 7575 ocion bbbi empeues o cene nd ose po pds

he educed opeang empeaue found wh he LEGbeaing hae been aibued (in boh pape o he change inhe ubcaion uppy mehod he dcuon of he fpape uggeed ha he ue of offe po n he LEGbeaing wa conibuing o educed pad empeaue heauho eponded o h n he coue wih e daa fomhe coneniona beang ha howed no empeaue adanage fo he offe po conucon a compaed ocene po beow abou 11000 RPM

he dicu accep hi bu wan o noe ha i i no inageemen wh h expeience n e wok on beang mao he auho' "conenona beaing In hi epec Fg gie e daa fom a 26 mm (10 36 q cm (1q n x pad hu beang in boh cene (0 and offe(06 pio conucon Unfounaey he opeaingondiion ae no denca o hoe of he auho bu aompaon o Fig 9 can be made he empeaueaue n he dcue Fig ae he aeage of he

hemocoupe n he - ocaion ahe han he hoe ofhee a he auho ha ued

ecognized ha h (Fig I) i no neceay acompaon of he ho po on he pad hi i ceainy oneof he pobem in uch e wok becaue a he auhonoe he ho po ocaion aie depending on he opeaingcondiion and beang deign Howee Fig indicae

ha educed empeaue (ma o hoe in Fg 9) caneu fom offeing he po he queion fo he auhofom a h whehe any e hae been un on a cenepio LEG beang h woud aow a diec compaon ohe coneniona beaing and ioae he nfuence of heeading edge gooe fom any inuence of he offe po

In he Concuon o h pape he auho ae hafow ate eduction n a fooded beang mia o hoe n

ur f Tbg

he LEG beang eu in unaccepaby hgh beang empeaue Ha h been confimed by e

Auhor'sCosure

he auho woud ike o expe hi gaiude and appeciaon o boh M Gadne and M Man fo hecommen and inee hey hae expeed in hi pape

he queion of whehe o no he excepiona empeauepefomance of he Leadng Edge Gooe (LEG Beainghoud be aibued o po ocaion o ubican uppymehod ha been aed by boh M Gadne and M Manhi i he ame queon ha wa aied n he dcuon ofefeence [1] he epy o h queion ha no canged buhe fac ha h quetion i aed agan uge ha a moedefniie anwe i equied o eoe h queion equehe conucion and eng of a cenay pioed LEGbeaing Unfounaey e eu ae no cuenyaaiabe bu wi be n he nea fuue

M Gadne queon concenng e eu fo a

fooded beaing opeaing a educed o fow ae addeed n Fig 1 A a ue beaing opeang babbiempeaue in a high im peue egion uch a he /pecen ocaion ha exceed 130C (266F ae conideedexceie fo mo appicaon Ceay fo a haf peedexcep 000 and 000 pm he educed o fow poducedunaccepabe / pecen babbi empeaue

M Man ao queoned whehe a he beang ewee conduced wh peuized (fooded caing he

HS % B % W % W

: ( S)

IS V 32 t 78 'u:2

P -

Fig. 7 A compison o he oes 7575 pecen ocion bbbempeue o beng suppied wh 00 nd 5 pecen o ecommended oow es

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answer to this is "n. Th cnfusin prbaly rsults frmth statmnt in th txt that sats All tsts wr nductdwith a disharg rstrictin h rstrictin is nt n asingdrais Wich wr p uly, t th tngntia dishargpt of th il ring OR Th prps f th il cntrol ring

\

4301 Vol 7 JULY 985

is t miniiz aring pumping and chrning lsss y x-pditiousy rmoving th from arund th aring carPrssur asurmnts ma ing th LE tsts indicattht th static prssr ithin th O nr dd MPa(2i)

Transactis f the ASME

Documents

32 - 1985 - LEG Recent Developments