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8j Lincoln VoLfvnateln, ten* L. Iterar,

Aircraft teglna BMMieh Laboratory Cl»T»l*nd, Ohio

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COOLffO (V GAS TUKBIWB

ii • Trr.xrrivmBs or tm COOLXKI or BLAISE

hj Mac In Woir<mat«lnd§eM L. Meyer, and John 8. McCarthy

«n analjralo la presented of rla exiling of gas-turbine blsdeo, that la, reducing the •.uap--ra»uro at the base of thu bladu (wheel r.a), which so-la thu bladu by conduction alone. Fonatlaa for tea- puratura and stress distributions along thu blade arc derived, and, b. thv us* of experimental .atrose-rupture data for a typical bladu alloy, a relation ta established betveoa blade life (Mac for rup- ture), operating spued, and eaount of rla cooling for auroral gas • sm rature«. Th> affuot of a blade par—iitur eoMblnlug thu offocta i blftdu dlaunolona, blado thnranl ocoductlYlty, and beat-tranarur coufrietont la detoralaod. Thu offoot of radiation on tao results la appro* Meted. Thu ama taaasratarue raagud froa 1300° to 1900° r and t)i<: rta toaporaturoa, froa 0° to 1000° T bolow the gas teapora- • -i*. . Thla rapcrt la concerned oaly with bladoa of unifora oroaa section, but the conclusions draaa aru generally oppllcable to Beet aodorn turblno bladoa. For aoat bladoa, goa-teaporaturo laoroaass aru Halted to about £00° T for 400s to S0O° T of cooling of the blade baae below gas toaporature, and additional eoollag bring* rrigreaalTcly sanll.r Increases. In order to obtain laaroaaoa la gas toaporatur* of the ortor of 400° T either Tory lavas Increases in thorns! condoctlTtty or Tory large ducrcaauo In hcat-trnnofur coefficient or bladu lungth are nocoaaary. tka lasreoaoa la gas t •!<• r.'-ur allowabl vtth rta'eoollag oro particularly aan.ll for turblnea cf large dlaunaloaa aad high apeaifte aaaa flows. Substan- tial Increases la blod. lire, howuror, ore poaalblo with relatively •mail eaovate of rla eoollag. Elongation das to oruap la not a practical limit to thu operation of aoat turbine bladoa.

I

8

IOB

At thu request of thu Air Tuchnleal 3 rric. Ccaaand, Aray Air Forea*. the RACA Is conducting an inveatlaatlca of the eoollag of tr~> turbiiv a that will include direct bladu cooling by thu passage

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of liquid or e!r through hollow bladea and Indirect blade cooling by r—i nl t heat fro* the blade root or tip. in part Z of thia eertea of reports (reference 1) • calculation la aada of tba com- plete teaperature dlatrlbutloa in a gas turbine in which the bladoa ara o '•• i indirectly by air blown over finned eurfaeaa on the dlak and blade ahroude. It vae round that the baae of the blade waa -led about 500° * below gas taaperature. In toe present report *.h benefits of blade cycling are determined In tmu of turbine operating conditions by combining the teaperattiro dlatrlbutlon In the bladoa with the mechanical 11ml tatlona to blade operation. The ruDort la United to rlm-cocl«d blades; that la, bladeo cooled only at the baa*.

Only tvf typu* of mechanical limitation to blade operation are canalderad: (..) rupture due to centrifugal stress, and (b) elonga- • • .-. of the blade beyond the design tip elearaneu due to exceealve creep t the blade aatal at high atr ee«e and tonperatttraa. Actu- ally, tbeee two limitation* are both manifestations of the aaaa property of the material because fracture occurs at the polat along the blade whore the looal plaatlc elongation la greater than the aetal can withstand. Contributiona.to failure froa vibration atreeaea or corroelon are not considered.

The bencflte of blade cooling any be asasured bjr lnoreaaaa In allowable gas teaperature, blame apaad, or blade XUm, where life la the tlaw to rupture due to centrifugal stress. Spaed it ordinarily Halted for aarodyaaaic reasons bjr the deal go hash auaher sad the purpose for which the turbine Is used usually detaralaes the desired life. The purpose of this report Is to deteralae the effectiveness of rla cooling ss indicated bjr the Increases la allowable gas tiapir- ature that can he obtained without shsnges la blade Nash nuabur or blade life. The Increaae la blade life that could be obtained by a saerlf ice of aoae of the Increase la allowable gas tiaayaratura is indicated, and the effecta on rla-coollog effectiveness of blade dlaaaslons, blade theraal conductivity, and hoat-tranafur coefficient froa the hot gases to the blade aatal are evaluated. The elongation of the blade due to oreop. and its lamortsnee as a imitation on blade operation are determined.

Although the Quantitative results of the saalysls sra dependent on a nuaber of slapllfytng ••aiauitions, psrtleulsrly that of a uniform blade croaa eecti :n. tho treads indicated and tho order of magnitude of the results aru beliuvod to apply gunorally to aoat turbine blades.

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blade ercae-eeetlunal araa, («q ft)

matter of blades

•ran dlaneter of turbine bladae (2rt - 1), (ft)

percontam* elongation at any blade point -

percentage elongation of blade natal

total parentage elongation of blada

fraction of blade surface araa exposed to radiation fro* one aide

acceleration of gravity, St.Z (ft/seo2)

heat-transfer coefficient baaed on Ta, Btu/(hr)(aq ft)(°»)

blade themnl conductivity, Bt ./(hr)(rt)( >)

blada length, (ft)

tip Mesa nunber index. V/a

Uniting tip Nash nunber index, T_./a

blada perteeter, (ft)

radtua at turbine at any point on blade, (ft)

tip radlua of turbine, (ft)

gas conatant, U.5 (ft-lb)/(lb)(°R)

actual atreaa at any point on blade, (lb/aq In )

atreaa for rupture for Riven life and temperature, (lb/aq In.)

tenperaturw of blade at any point, l°U)

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i-.ra'.aaibK uwronac in offuctlYu on* tuajporaturc duo fee bladj cooling for ruuatant K^^, (°F)

titul t'«p-:r-itur>. of lnl-a #»e, (°R)

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Although • relation totWMB tfce eff«ctire «M toaperatuiv T, and u.c —MB of cooling % - T0 for • c.matant Halting Much KBtmt !nde» M^x !• dMlnl, the aetftpd of annljreie Mh>i It neceeearjr to calculate flrat the valuea of «*• »•- —

' fill* Mfc^f... J

—- wpvccaa Diadv 1 •***• •»*• and L/r. .. ..mm or fl» (II—nalonleaa . —. -M. and L/rt. Meana of accounting fur radiation and calculating the blad> along**Ion duw to creep are alau preaet .. _..r MB crwp are alau presented.

Aeeunetlone- - In the derivation of ojcpreaalona far the taaper •turn and strew distributions, th« following alaplif>ing oaauap- • r.» are aedoj

1. law blade la of unlfoaa oroae-eoot tonal ore* and perlaawr.

e. The heat-transfer coefficient and the affective gu teapara- turu are conatant over the blade height, da average value for tha theflaal cnnduotlvlty can be used orer the blade height beoouee the Torlation of conductivity vita taageraturu la —" -— aetal*. •eight

"1 for •oat turblnu

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l<*a>uraturo llfo. t0" * aai, thi • *•»«««, "Lj^Mad. lUu lm - .MV la apeclflud. thu HUIBUB taaporattuv

Xauationa (3) and (4) aa/ be ooablnad to flat tb« allowable toaper- • t .r at any blade point and for anj blade apood for • glren blade

aot«l and coaatant valuea of blade life, au toapuratun 7 , aaount f r!« eoolla* (Tu - T0), and the paraautera oi and t/r,.-

A faall/ or curroa of T( n> function of x/l with f M • p«rea ' r aay * dram.

failure oeeura «Bua too actual blade toaperaturo at one blada point la creator than the allowable toaporaaarij. the Halting tip aptud la that for whleh thu allowable Uanxrature la Juat equal to the actual t ap- retur at oao point on the blada, which la celled the critical bled point hueauao thu blade would fracture at thla P in* if the tip epwod were lacreaaod. Mataaaatloally, thu Halting tip apuod aad the orlUeal bladu point aiv defined by two elaulta- neotie uanattone

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Blade creep. - Experlsantal data an the creer propertlea of blarte aetals air* the percentage* elongation for a fivm life a* a f-irt! r. of astal tsaparature and stress

a, - % (I, a) (S)

When equation (a) la coabiaad with tha actual stress-distribution •1'rt'Mi (3) and ta« t —inratura-diatrlbutloa aquation (1) or (2), tha actual percentage elongation of the blade at anr point and for wyr tip speed aay ba found

of tha 1 ado spaa

Tha t.tnl percentage elongation of tha blade la found by lntugratl.r. <*ar «h" blade height for any Hade apaad,

(10)

Thia equation la useful only for valuua of T f T_. bucauaa, for greater valuea, tha elongation of tha blade bee rates infinite, cul-re- spcndlng to blada fracture. Iha evaluation of equation (10) nay be carried out graphically.

ATP1ICA1ICI Of AhALWIB

.TM. foraajulng analyala la general and applies to any blada of unlfora crosa aeotlon. A blada section waa aaau—d and the corre- «? nd.n«r »aluea of tha ItnenaIonia— par—Iar al. ant l/rt ware -eed to obtain quantitative reaulta. These valuea are raferrad to aa the "baslo" valuea. la oraer to aha* tha affaet of heat-transfer

vfrieient, blada conductivity, and blade dlaanaloaa on tha reaulta, saleulattcaa war* aade for valuea of oj. equal to 1/3. 1/2, 1, 2, and S tlaaa tha haale value. A single value of t/rt waa uaed throughout bcnaaaa tha affeotiveneaa of cooling dapoaia vary llttlo on L/rt for tha usual range of values for constant oX. The quan- titative reaulta ara alao dependent oa tha aaaiea.il aeohejiloal prop- erttaa Of the blade aatal. Values of tha effective gas teaperatuiv froa 1500° to 1900° F and of aaounta of rla cooling froa 0° to 1000° P

value of tha Halting hash latad for each pair of values of of l.n.

uaber latex ana oelcu- Tc for a value of y

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flafl alarnalons. conduct! T'.ty. and heat-transfer coefficient. ttf beale VUNM at3 and L/rt were determined from valuta of the blade dlaeaalons, the blade — ta 1 conductivity, and the heat- transfer eooffletent repxvsontattvj of those found la modern hi<*- '-vmperature «u turbines:

Arc* of blade oroaa wctin A, at ft 0.000728 (or o.ioiT «q in.)

"oriaet--r of blade cross auction p. ft 0.20 (or 2.40 in.)

Biadc, i-mrh L, rt 0.146 (or l.TS la.)

Pad'us at tip r,. ft . 0.570 ( >r 6.S4 la.)

Thermal conductivity of the blaAa k, Btu/(hr)(ft)(°F) .... 12 Seat-transfer ooofflolent b. Btu/(hr)(«q ft)(°r) 40 Beale value of oi 4.42 Basic value of lfr% 0.26

The T- ije of h r 40 Btu/(hr)(so. ft)(°F) corresponds to relatively low aaas flows; beocuee of tfc.i> relatively law valua of a and tttu ch< lee < a fairly abort blade, the baa la value of oL probably la a* low as la obtainable at present.

Hoohanlonl proysrtlea of blade metal. - The aarwari mechanical properties of the blada ratal ara mom la figures 2 and 9. Ihoae properties are baaed on available data (references 3 and 4) for 3497 alloy, which la a forged ferrous alloy, high la nickel, chrc- alum, and cobalt content with a density of 0.31 pound par cubic Inch, and are extrapolated to Include a wide range of taapiraturea. The «ti- ••-rapture proasrtloa (fig. 2) ara typical of the stronger alloys now available for turbine blades but tho creep proportion (fig. S) are relatively poor. 8497 was aalaoted In carter to aoouatuete any nosslble creep limitations la blade dealga.

affective aaa temperature. • las effective gaa taap>rature T, rather than the total temperature at the lnleb to the turbine T. la isod In the analysts beuauaa U la U»« temperature that outers into the heat-transfer equation. The power and the efficiency of a stmprveeor-turbine unit, however, depend on T , and the relation between these twr. tuaoeraturea should be known.

Taw affective temperature la approximately ecuel to the total temperature relative to the Moving blades, the ratio of the total inlet temperature to the effective temperature calculated at the bled, diameter la therefore

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Is a i* F< r b ciutant bledv Much nuabvr end o given velocity d'.agraR, uhleh 4*t«imttM>a *„/*_, M> inlet total t.Bp-mturv la direotly propor- tltnel to the •ffMctlrv tunswraturu. for osanple, if the Hash nunbor ndv* la a»t a* 0.5 (an* 5/2r, - 0.81), T-/T# « 1.041 Tor V^/Vj, >•-

(tjpiaa' «T reaction blades) and tJtu > I.06S for •*/»» - 2.0 (typical * lnpuleo hladue).

Badlatlon. • The effect of radiation on the temperature distri- bution ScpuSS to a great extent upon thu particular Installation of the turbine, which detemlaoa the values of ttaa taaneraturos Tj ana Tj, a* v.n a* the validity of thv approxlaatlona ueud in treating radiation. (Sao appendix.) The results Mrs calculated without radiatlt*!. but th. ananer in much tbo various radiation eaeunptlone aodiriod these r.riiti was investigatud.

In the application of the ladlatlon equation (za), the following Ions ware andei

I . Tbf> average blade teapurature TR uaod in the approximation

T* - «,,* T - 3Ta* «!»««. In the appendli as equation (IS), was sot equal to Te '0/*)(7v ' To'» °»l« *»Uu *** datamlnad by comparing tho torn* perature dlatrlhutlua given hy equation (2) for several valaos of T. with one found by numerical Integration of the east differential .quatlon for a typical easo. for extremely blab eonduotlvltlss or

'j-\

low heat-transfer coefficients, this valuo of T- gives blade tem- peratures that ar- slightly low. A v .11 bo aor«. accurate for thia ease.

.0, 0.9,

lower value for Tu

0 with

l.SK, m valid, x Tl t

inlet total

•ore gan-relly, If Tt to values

0 times tbo value of of E.O,

respectively. Th. a given Tu duponda in thu dlfforonoo between

thu offootlve gas tampnmturc and .« thu extent to which thu noaalca are eoolod. on the exit side of the blades la particularly dependant on thu installation because the value exhaust to the atators of another stage, to on directly to th* atmosphere.

MACA m • . niso n

.». The factor CF. which enters equations (2b) and (2c), wao ••t equal ij U.S1Z. In.a value waa obtained bjr assualng oloaelj "•paced Mad'-a far whleh the total blade-aurface area expoaed to radiatirat froa either alda la approxlaately equal to the annulua araa aft.. Consequently, F waa aat equal to •fiL/Bpi vhlch wait evaluated aa 0.312 ualng the baalc blada dlaenalons and a value of B f S> the value of c vaa eonaldarad equal to 1, which !a th«> value for oxtdiied aatal aurfacea.

RSBULTB AID DI8CUBBIDN

affectlvoneea J rla ooollna. for baalc blade. • The over-all •rfoct of rS cooling for SS baalc blada fSC » 4.42) la abown in f jf.r- 4; radlatlan effecta and blade elongation are nut Included. B«au*<i the boal • value f U. '.« lower than that fur aost nvdorn tu-fiei, theav reaulta for the baa la blade aay be considered ropre- oontatlve of the turbine* for which rla cooling la aost effective. S ad. Ufa la plotted on a logarlthalc acalu against the Halting Hach nuabar index; famllloa of curvea, each for a constant affoctlvu gas temperature and aeveral aaounta of rla cooling are shown. Largo increases in blade life ean b- obtained with aanll lnoreeaee in the aajoaat of cooling at a constant Mach iwabur indux. For exaaple, Increasing the amount of cooling from 200° to 400° F at a ana tonp- r- tture of 1600' F and a conatant Halting Much number Index of 0.5 r.aulte in Increasing the allowable life eightfold. Because thu .-urvea € figure 4 are approxiaatoly parallel, results for a alnglu valae * blade lire are fairly typical of all values.

A cross plot of curvea of the type In figuro 4 at 1000 hours (fig. 5) shows the effective gas toaporature as a function of thu aaount of rla cooling for constant values of the Halting Mach nuabur ndi Figure 5 lndleatea the effect of different aaoants of rla

• '.T*' n the allowable gae tuapereturu for a glvon design bocauae the llaltlngjlaeh nuabar index at which a turbine Is to be operated ta doteratnud by the dualist.

Th* data <«r riguru S for a constant Halting Much nuabur index of 0.6 have hvon roplottod In figure 6 aa the increase la gas tan* pvraturv ATa greater than that allowablj without cooling. The urrvapadlng Increase in the inlet total taaaeratare la froa 2 to

10 percent greater than the value of ATt, depending on the velocity d'.agrwa of thu turbine. Line of constant Halting Mach nuabar Index f 0.4 and 0.6 give value a of *T0 that vary less than 90° F froa

those in f :gur>' 6. Th:e aaall uffect r M*eh nuabor lndox ean bo - »pl(. n~d by thu fact that thu lines of conatant Halting Mach nuabcr ;ndva erv ^ppruslaatuly parallel In f Iguru 5. At lower Halting Mach

12

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nuabera. the value* of »r0 are alight ]j leaa; therefore, rla c ling la »ae«faa' !••«* effective at high gas toaperstures.

It should *» —*-•

•""d *ltbur „_~*£- a. ^tu#a • _*"£»«• would b» mnriS?

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. .. .« coat _,—». ir th< •<. actual operating conditions *<n > vn in figures 4 ami .% the only alanlfJcaat change would be a

>twral dlsplaeoaunt of the eurvea relative to the axes. If the cter of oafetjr Is introduced col; by swans of a specified reduc- -«» in thu offuctlve gaa t^apurnturv, the curvua of figure 0 arc lid for the act .ml operating conditions ae well aa for those at

Increase* •- ~-

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_j L— conduct'rlt>. and heai-transf«r .... . - mo value of the dlaenslonless parameter ateoa> r»Hij d<stemlnes the iff vat of blad. disjanslons, conduct ivity, and h>-a' -transfer coeff icier.ta an th.< results when radiation is nogl<ietud and thv ratio l/rt la eonatant.

Ike Weaaeratur* distribution In the blade la shown In figure 0 r r an fr.ctiv gaa toaperaturv of 1500° t and a r*tSC~& (?~ : ?c) r '(X? t tor sovon values or al including the Halting values of

m and 0; theai curves an euperlapoeed an a faalljr of allowable. '-•ejperature currea for a 1000-hour llfo to dotemlnc the erin—' '" de polats. for values of at groatn* «•>- »t4ixa art verv »i—~ •••*» pouta0"*!*" '•* • 10t»-hoar7E*,d °° • *"«»11» or"Lr^1*1** * ao-...r•t«- **; **»««, of i*L"£" «• doteiajjncJ* *"o»abi„_

LtlSr'» -U*-Taa22r2-^ «ft haar^.^- • • -•* w»v critical -.—» poiata. fnr value* _ «». greater than 4.42, the blad, toa>

poraturea art vary cloao to the gaa tuaiperaturu c*wr half the length of th* blade, whvraaa for aaall r valaoa of at all blade Uap n- '•#« <ire ooaaldarablr lower than that of the gaa. The critical •led r> lot la elcae to the root for aaall rulu.a of at, and uppr<««hee the blodV tip ae at la iacreaaod t. a Taluu of about 4, but for Largur »alu a <g at thu critlcii point again beccatua eloaer W tha ruot. At low raluea of at, tho critical »•>-'• "—* point again t._T" «#

Point actuaii,

.

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tmm&tm at ta» r «>t for to* f lrat •.»»r«X hundr«d d*e*waa of ooollaa but thua a> *•>• nuito rapldlj tuaord thw tip aa eoollag la looraaaud (fi«. n.

Th*. variation la taa aff octlvaaaaa of rla cooling with oaanga* la oL la ahcwa la f lguru 6 tor a bladu lifu of 1000 hour*. Tan laoraaaa la allowable affactive gaa taanaraturu la much graatar fur the lnwur valuaa of oL; thua, for a aolau of t# • to of 600° f, to* tneraaaa la 440° » for at. of 1.47, 818° V ror 4.48, and only 3" T for 13.26. at valuaa of at grantor than 4.48 thara la llttl* \ncr «• la «T, with laoruoalng amount* of cooling abovo 900° to * ' r but, r r thv »«rj low valuta of at, 4TU ooatlnnaa to lncrvaa> aln- at propurtlonmUy vita t, - 10 ovwr tha aatlra rune e JMUUIV*. Vila cooling aaa ha aaaa, of eourae. to lneraaaa biad. lif« b-jond 1000 houra ay aacrtf lclag aon» of tho lneraaaa la gun tenmeroturas for "SampU, a aacririou of about 60" 1 In gaa tianir- eture ror at of 4.42 amkaa poaalbla a tenfold incruoa. In life..

the Uw valaeo of at n»oiaaary for rla ooollng to ha Tory orfaetlvu could poeelbly ha obtained hy Inoraaalng th« talae of - n&jf tvltj or duoroaalag ta value of thv heat-tronafer ooaff 1- eUnt from ta* haalo value*. For uxanpl*. too vnluu OL la halved if k U laareaaaa from u tc 48 »tu/(hrUrt)(°r) or tf h la dooruaaad froa 40 to 10 Btu/(hrK*«. ft)(°Vi. Unfortunately, noae of tha alloy* no* avallablu for aaa at high toaworaturua and atroa*.» hoa a oonduotlvlty aucn grout r than U. ta a jlr;n turblna tha

ncr> a»ud cooling effeotivonoao ohtalnid hy Imriaalag tha ounductiv- Ity might ha offeat hy tha fast that additional haat auat ho froa taa Mat* to maintain the anno rt

I •

A relatively low value of h might ho ohtalnad hy a proper edjuatauat of the doolga wlooltloa over tha hlaioa, hat tbaaa voice- tioa aro nanally reatrlotod hy aerodynnalci eaaatmoratlona. It uae

cf laaulntlng ooatlaea on thu alamo rooulta la email reduction* la tiu over-all auat>tranafor ooaff lolaat froa thu hot gaaoa to thu axtol hlaha fraB an initially low valwo of h, amah aa 40 Bt->/(arH»<t ft)(°r). althovah th - cat lag aaa aro4u»o Klatlvoly larau reduction* froa a hi«h «alao. To* oaamplo, If h la 40. c cjatlag 0.011 lash thlok vita a oontaatlvlty of 0.5 Btu/(hr)(rt)(°r) «111 roaaaa tha o**r»all ooaff lolaat only 6 paraoatt If h la MO, ta* aonu aoatUax will roiuaa tha ovur-oll ooaff lolaat 30 parooat. A eating, hoaxer, any aoaaaa tho hlana or lanraaac tha ratio p/A and tarn* at. ahlok alntt ooaalataly counteract tho raTorahlo offaot of thv nduct.ua la thu >t r-all rila coufflolaat.

A lov amltts of at can alao hu 6btalaod by tha a*o of a abort tl->4 or a blad- «nth a anall p/A ratio. la ardor to obtain tho ••ov anaa flow «hua th%. blad* length la aaoruaaod, thu tip raalua

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auet t>* UMWMd, «hlch •••nil that tha lncr»aaed cooling afTacttY. MM 1* gained at UM. price of tow—lug the alt* of the turbine. Th* value of L/rt la also dooroaaed In thia oeee with tha result that the oeloulatlono are not atrtetly applicable; it mag ba ahown, howaear, that although a dearaaae la L/rt oauaaa a eonalderable loereeee la the Halting Hash number index tha dooreaae baa little offaet on tha eurvea of aT„ agalnat Ta - T0 (fig. 6). tha ratio

.' blade purlaeter to area, ahleh dap and • upon tha ahapa and tha alt* of tha blade, la Halted by aerodynanlo aoaalderatlone and no •i«ntfleant nbanga In oL ean usually ba obtained bjr a variation In p/A.

On the othar hand, larg* hlgh-pueer turbines ara Ukoiy to have valaee of oL conaldarabljr greater than 4.48 for t«o mesons: (a) thaaa turbinaa have larga epeslflo aase fIon and oanseeuently tha value of h la graatar than 40; and (b) thaaa turblaaa hare dlaanalona graatar than tho bnatd values enssasd. For uxaaplu, if tha boat-transfer eoaffioluat la lnereased froa 40 to 1£0 and all tha dlaanalona ara aultlpllad by S (thua anltlplylng Jp/A t bjr Ji), OL ia laanaaid from d.dt to 13.86. -•r

Jaffa oreoa. - The d the blado length and j»or

lttrlhitl

dlatrlbuttoa of local elongation duo to er«op tha corresponding stress and toaparature

In figure 9 for a particular aat of coodi- tlona. the total blada alongattoa obtainad bjr Integration of the dlatrlbatlon of local alongatlon la alao given la tho figure for aaeh tip apaad. flat poroantaga alongntlon of tha blada at rupture dapanda prlaarlly on tha teaaerature at tho critical point vaoro aoat of tha alongatlon uccure. at lanpnratan at tha critical point for afreo- tlve gna tonparaturoa froa 1400° to 1500° P la la tha neighborhood or US0° F, at valoh teaparatura thu elongation of the blade la a

(rig. 3){ accordingly, the aaxlaum blade uionaatton for these ild ba tha ailna elongation for an* ga

Tho elongation of the baale blade for a gaa teaperature of 1900° W la plotted agalnat Nash number Index for several aaounte or coollag In figure 10. the anilana olongetlon indicated ta only

ne-slsteeath inch, valoh la leaa than aoat blade-tip elear- If a short »r bijd life were asausud, the aavlaim elongation

at ruptare would be expected to be acawahat larger and algfct be •.xr-aaiv-.. For longer bladea tho nwTiana peroentagr elongation la expected to be about the aaau: for auoh bladea, tharefora, the total ol'waatlon at rupture nay be eonaldorabljr greater than allowed by the tip clo

i m tea,' -

3

15 •ASAMS *... mao

netaal bias* aloagatloaa, hoaawar, will ha «uch auaUer . •b« awanai valu*« ladlotad hagaBBl UM. turblnu la actually jp»r- atad vl'-h • raetor of aafoiy and tha alonantlon 1* groatly —"—** -j » aanll IIWIMI la hash nuabur index or a aaall laoraa eoollag. An actual turbine wuuU aavar ba aparatad at a «. corruaacavtlnc to tho vertical port loo <vt th» oareea of f tpm 10, fur ««r> little nwnraaeaa would reault in rupture. Ineaaucn aa the creep prnpxrttaa aaaaaed for tha blade autal an relatively pour, actual turbit*. operation mil not ka Halted by

in

arfaflt of radiation- «ari.a gr-tly %44k tk. a T, aai T,. If then* to

incrvaaea »»»i«> «- ^^ «rf«atl»uBIM o

effect of radiation on theae reaulta nltti of the radlatl m tuapuratur.a

oaanl to the ana tonpuratur., n» ..._. _ aa tho uffoct of n ineruaaod value of too haat-tranafor coamcieut or cd* oL. Iho .nf luaaee of radiation on the affeotlvuntea of cooling can than bo rowed by uaing velaea of Jf L aa offactive valuua of at, la, rig- ara «. Ik* —aUadi of the laanaa depuoda upon h and To, alono for a HaHHt value of «F (oauatlro (»)). For aaall veluoe of h ant larff> velaea of lfc (ecrroepondlng to blah (aa tuapuraturua), tha vale* of Jt t any bu aa aueh aa two or threw tlava tha value of aX; however, for tha baala valao of h (40 Btu/(hr)(a« ft)(°F)), Jx I U «ly about 1.3 tlaoe tha veluo of at.

r

If T. or T8 U oaa-a d loaa than ia «. -. T , aa la likely for aoat titrblaaa, tho effoetlvo Inoroaau In ai will ba counteracted by a dueraaaa In ift, ahteh baa tbo eaac offast on thu teaperaturo 4io- trlbatlon aa aocreaalng Tu. In fIgor- IX, tho toaporeturo dlatrlbu- tion for tha baala value of at of 4.4c ana no radiation la eanparod with that for four radiation appraslaetlona. Aa the volut. of Ig/Tii ant eurrvapondlagly tft, la doeroaeod, all blada teaaoreturee aro doemaaat ant tho Halting Mash nnabor indicia lanronaat bna Halting Maeb naabvr lalox f rr no radiation la apnroKtaatoly tho aaan of tb- •Uim for dlfforunt radiation aaauaptloaa and thu critical blado , lnt la aoauWAat eloaur to tho tip than for thu aiaanloa that lnoludo radiatton. Tb^ liwriaai In allowable gaa toaporattiro with radiation la coaparud in tb*. following tablu with that for no radiatton for

T. m T_. > I9600 K, and a 1000-hour 1UN:

'"

1.1 1

aBPunta of eoollng.

won** tstto

40 40

aao 40

4*6 624 SSI sts

\.v s.-»», s."»

4SS 400

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17

1I7 la*»> '•new— la pi taaporaturo la aaoriftoad, hovavar, «•».__-. IKK-IMI la blada Ufa ara poaalblo. For thle typical bladu, th- «ffartlv« gaa taaparatura could ba ralaud 200° F for • 500° r duervan* In rla taaparatun. bale* gu taaparatura at a eoaataat Halting amah —air lndaa. A'.tamatiTely, If tha gaa taaparatura and tha Mask nartir laftac ara halt content, tho axpaotad Ufa could b« aaltlpllad by a hwlnd for tha aan» —wait of cooling.

Z. Thu dapendenco • * thu affaotlvanaaa of rla cool lag on thu »»•>•*. •tranaf -r ooofflelant, tha binds dlaonalona, and tha bladu taor- aai conductivity la dataralaad by a alnglo blada paraavtar. In oatar to obtain lawraaaaa la au taaparatura of thu ardor or 400° F, •xtrea* Inaraaaia In tharaal conductivity or daoraaaaa la baat- tranafar coefficient or blada length aro nooeoaary. For turbines

>f large dlnenalona and high apaotf tc aaa* flowa tha lnereeaoa In gaa teaaeratarv poaalblo vtth rla cooling ara particularly aaall.

S. Ma cooling la a*et affeotlre for tha flrat 250° to 900° t of cool lag of tha rla (below gaa liaaninturo) 1 with aora ooollag,

-!•-• baecao progrtaelrely aaallur. for tha typical blade, — ..«v LUTO laaaaaaa of t00° F, banaf Ita aaaoaa y i^, 500° F of cooling allowo a gaa teapura>nrti Inariaan 01 *w • . wbotaag \axT 9 of ooollac a***" an additional laaaaaaa of call 60° F. Thia uffact la Inhiria* la thu Indlrentanaa of rla ooollag b-aauat-, m tha amount of cooling to Inanaail, tha critical point on tha bladu aovee farthar frca tha aeaaoa of cooling (blade baee) and cooling thoraforo bueaana prijgraailwuly aera difficult. la ordur to obtain largo incrcnaoa la gaa toaporaturo, aoao dlraet aothod of ooollag would probably bam to ba oaod, la ablch a con- elderaelu portion of tha blada lungth la coolod by contact with a coolant fluid.

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Aircraft Bn^Uv. Ruaoorch Lub>>rator>, »»*!«al Advisory COBBUttou for Auruooutlca,

Cluvoland, Ohio, SV.ptdBjbor 20, IMS.

Lincoln Wolf aajftaln, Pbjralclat.

Qono L. Major,/ Muohanlcol Engineur.

John 8. JtoCnrthjr, Mechanical Jtagtaaor.

/.ppivrod: Oacar W. Schojr,

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Z. Slaw, M. W., and Rurrla, R. H.: Teaperatvuv Distribution Analyalr r r Buekata oa* Gu Turblnea. Data Folder Ho. 71252, Oan. Big. Ub., Oenoral llaetrlo Co., May 16, 1941.

S. Croaa, I C, Stewart, W. C, and McCann W. J.i Compilation of Currant Data on Beleetad Allcya Suitable for Klgn Tanparature ferrtev In Gaa Turblao and Swpareharaar Parte. Sar. 11-12, OSRD Rap. 722, Nat. Aoad. Scl., Rat. Roa. Council, War Metal- lurgy Coaalttaa, Julj 22, 1942.

4. Croaa, Inward C, and SUamona, Ward P.: Prcgreaa Report on Heat- Realatlng Metal* for Oaa Turblna Parta (R.102). 068S1I . 3651, Ser R . M-2W, R9RC. OSRD, War Muttillurgjr Dlv., MajaBa^l944. I ,

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Wolfenstein, L. Meyer, Gene

• McCarthy, John

AUTHOR(S)

DIVISION: Power Plants, Jot and Turbine (5) SECTIONs' Cooling (1) CROSS REFERENCES! Turbine blades - Cooling (95308);

Cooling conduction (27200)

j&VO* 153W

'OBIG. AGENCY NUMBEn

KR-E5I20 ,

REVISION

IAMER. TITLE: Cooling of gas turbines - Il~- Effectiveness of rim cooling of blades

FORG'N. TITLE:

ORIGINATING AGENCY: Na TRANSLATION:

tional Advisoiy Committee for Aeronautics, Washington, D. C.

COUNTRr U.S.

IANGUAGE FORG'NrWSS Eng.

U. S.CLASS. Restr.

DATE Sep'U5

PAGES 21

IU.US. 1 FEATURES 12 1 table, graphs !

flOOTQACT i An analysis of rim cooling, which cools the blade by conduction alone, was conducted.

Gas temperatures ranged from 1300° to 1900°F and rim temperatures from 0° to 10OO°F below gas temperatures. Results show that gas temperature increases up to 200°F are permissible provided that the blades are cooled by 1*00° to 500°F below the gas tempera- ture. Relatively small amounts of blade cooling, at constant gas temperature, give large- increases in blade llfei' Dependence of rim cooling on heat-transfer coefficient, blade dimensions, and thermal conductivity is determined by a single parameter.

NOTE: Requests for copies of this report must be addressed to» N.A.C.A., Washington, D. C. ,

T-2, HO, AIR MATERIEL COMMAND Au "UECKNKAI DNOEX WRIGHT FIELD, OHIO. USAAF " ' • .

WIK FOK 89 »(B 1*147) Wolfenstein, L. Meyer, Gene McCarthy, John

AUTHORIS!

DIVISION: Povrer Plants, Jet and Turbine (5) ' SECTION: Cooling (1) CROSS REFERENCES: Turbine blades - Cooling (95308);

Cooling conduction (27200)

ATI- 15&6 ORIG. AGENCY NUMBER

HR-E5I20

AMER TITLE: Cooling of gas turbines - II - Effectiveness of rim cooling of blades

FORGN. TITLE: — , 5 NOV 1953 £0 1C£C! C ORIGINATING AGENCY: National Advisory Committee for Aeronautics, Washington, D

TRANSLATION:

C.

COUNTRY U.S.

LANGUAGE Eng.

FORG'NrUSSl U. S.CLASS. Restr.

OATf Sep'l^

PAGES 21

IUUS. 12

K AZURES table, graphs

ABSTRACT An analysis of rim cooling, which cools the blade by conduction alone, was conducted.

Gas temperatures ranged from 1JC0° to 1900°F and rim temperatures from 0° to 1000°F below gas temperatures. Results show that gas temperature increases up to 200°F are permissible provided that the blades are cooled by li00° to 500°F below the gas tempera- ture. Relatively small amounts of blade cooling, at constant gas temperature, give large- increases in blade life'/ Dependence of rim cooling en heat-transfer coefficient, blade dimensions, and thermal conductivity^ determined by a single parameter.

NOTE: Requests for copies of this report must be addressed to: N.A.C.A., Washington, D. C. ,

T-2. HQ.. AIR MATERIEL COMMAND AIR TECHNICAL INDEX WRIGHT FIELD, OHIO. USAAF * ' WKO-2.1 MAI 47 23,300