Free Memorandum - District Court of Federal Claims - federal

Case 1:05-cv-00187-JFM

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EXHIBIT D

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EXHIBIT E

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EXHIBIT F

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EXHIBIT G

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Sept. 20, 1966

GAS T U R B I N E POWERPLANT HAVING AN EXTREMELY S I G H PRESSURE RATIO CYCLE Filed Nov. 22, 1963 2 Shaets-Shsot 1

T. N.

HULL. JR

3,273,340

T H A A! A/#!< JE d M 5

INVENTOR

DA86

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Sept. 20, 1966
Filed NOV. 22.

GAS T U R B I N E POWRPLANT HAVING AN EXTREMELY HIGH PRESSURE RATIO CYCLE 1963 2 SheetsShsot

T.

N. HULL, J R

3,273,340
z

INVENTOR

/It/dMAS/L! HULL, JE
BY

DA87

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United States Patent Oflice

3,273,340
,ep,

,,

,, ,,

This invention relates to gar turbinc powerplnnts and, more particularly, to an improved arrangement for gas 10 turbioe engines of the bypass o r turbofan type, thc SINEtural arrangcmcnt of this invention providing an extrcme[y high prcrnurc mtio cyde c h a r a c l c k d by a relativcly low compressor discharge temperature. A jet propulsion powcrplant used for propelling an 16 airplanc achiurer iD maximum efficiency when thc forward velocity of the airplone npproaches as ncorly as possible tbs vclocily of tho propulsioo jcl relative lo tho nirplnne. Undcr such conditions, relatively little excess cnergy is dissipated in thc nlmasphere sin- Lhc products 20 of combustion are discharged with low abrolute velocity. A conventional jet en&c, which exhausts its high lemperalure productr of comhustioo as a high velocity jd, is thus most cfficicnt whcn uscd to propel an airplane at high spceds. The incRiciency of the conveotional jet 26 cnginc whcn propelling an airplane a t nlativcly low spceds is due to t discharge of the producu of cambush lion with greater absolute velocity, a substantial m o u n t of excess cncrgy thereby bcing dissipated in the almosphere. It has been found that both the cmcicncy and 30 thrust of thc engine at low speeds can be incrcascd substantially by means of a thrust augmentcr. A thrust augmenlcr incrcasw the eiicctive totnl momentum of the propulu'on jet by incressing the mass flow and dacreasing the velocity of the propulsion jet. In operation, 35 a thrust augmentor extracts energy, and eonsequeotly velocity, f m m the products of combustion and uses tho extracted cnergy to accelcrnfc enginc bypass air. A net incrcosc in thrust results since the increase in totnl mnss flow more than compensates for the decreasc in vclocity 40 of the propulsion jet. The amount of incrense in thrust depends in large part upon tho bypass ratio, which is the ratio of the mass of bypsn air to the mass of combustion products. As the bypass ratio increases, the availnble thrust increases and the velocity of the propulsion jet 46 decreases. Thc bypass n t i o is not, however, the only factor which dclcrmines the net thrust of a bypass or turbofan engine. I t is also known that increased thrust at vniious .bybypass ratios can hc obtainedin theory by increasing the pressure 60 ratio of the gns gcoerator compressor or, in other words, by compieising the motive fluid to a highcr presntre. The pre3sure n t i o cannot, however, bc increawd without limit since therc nre practical which crally dictate the maximum prcrsuic ratio compressor 65 for a given engine derigu. or example, when high pressure ratio compressor is used, compressor aWU may occur under part load operation or under vnrious other operating conditions such as during cnginc acceleration, such operation bcinp koown as "offdesign" operation. 00 Compressor stall is a conditiao which exists when the prcssurc ratio across the compressor is greater than the compressor is cnpablc of maintaining. T o alleviate this condition in the lower panions of the operating speed range, i l is porsiblc to vary thc engine fluid flow chnrac. 06 teristia to correspond to the operating speed of the cndine. One way this can k nccomplishcd is b y mcnns of monnting the compressor rotor rtages on fwa or more indcpendenlly rolclcd rotors, the high prunurc atages bcing m u t e d nt highcr qpeeda than the law prersurc slog- 70 during pnR power operation. Even where the comprcssor slJU problem is alleviated by varying tbe fluid flow

compresson. thc c o m p m m r discharge temperature cm be su&ienlly high to h i t severcly the amount of energy which can hc added to the motive Enid during the combustion process without producing temperatures which exceed the tcmpcrature capabilities o f thc Nrbine elements. It will therefore bc obvious to those skidled in tho art that turbine temperature limitations, combined with the characteristics of tbc combustion proccss, cao dictate the madmum pressure ratio which may bc pmclicably attained. An object of this invention is to provide n high prcssurc ratio gas turbine cngine having high net thrust and efficiency. an imA further object of this invention is to Provcd gas turbinc engine of the bypnss or turbofan type providing high thrurt and efficiency without exceeding the high tsmpenlure capabilities of the turbine elcmcnts o r the pressure ratio capabilities of the engioe compressor during ohl-design operation. A still furlhcr object of this invention is to provide a gas turbine eogiac having high thrust efficiency which is simple in design, relatively easy to manufacture, and both economical and rclirrble to opcrnte. Briefly stated, in accordance with the illustrnted embodiments of the invention, the foregoing and other ob~ C C U dt8incd by providing a gas turbine powerplant are of the bypas3 or turbofan type wilh a heat exchanger in which relativsiy cool bypass sir is used to cool highcr temperature compressed sir. the cooled air then bcing supplied to the powcrplant combustor. Cooling the compressed air makes possiblc the use of a n exvcmcly high PrcSSurC ratio compressor without execeding the maximUn tcmperaturc capahiiitie~ of the turbine dcmcnts. More particularly, a gas turbine powerplnnt ls provided with a1 leas1 two compressors, the Ant k i n g connccled to the engine inlet. Two ducts s r e connected to the d i r charge side of the fint compnrsor from which each receivcs a portion af the total flow of motive fluid and ultimately supplies thc fluid to the engine outlcL The fitst of thc ducts dcfincs a bypass passage, the duct dircctins the fluid through n hsnl ~ x c h n ~ g c r to ddivcring prior if to ihc outict. The second of the ducts defines the main flow Passage of the enginc, lhc duct serially directing the motive fluid through at least onc additional compressor, the heat excbnogcr in which it is pnsred in heat cxchange relation with the bypass Ruid in tho fimt duct, the engine combustor, and nt l e a l one turbine prior to delivering the fluid to thc engine outlet. Whilc the invention is distinctly claimed and parlic' J ~ w ~pointed out in the claims appended hereto, the Y invention, both as to orsaniwtian and content, will b c k t t e r understood and apprcciatcd, along with other oblech and features thereof, from the following detailed description when taken in conjunction with the drawings, in which: FIG. 1 is a graph showing theoretical variation in net Output thrust with compressor prcssure ratio for turbofan c n s i n c ~having various bypars ratios; and FIG. 2 is a graph illustrating how thr actual variations i net output thrust with c o m p r e w r pressure ratio for n actual turbofan engines compare with the l b e 0 ~ t i C d CUrVcs 01 FlG. 1; and FIO. 3 is a schematic side view of a turbofan engine utilizing the improved cyclc of this invention; and

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s,am,s40
3
FIGS. 4-6 illustrate alternative gas turbine arrangements which utilize the invention. FIG. 1 illustrates the manner in which the net output thrust wbich can be obtained LhsoreticaUy from a bypars o r turbofan cnginc vnriw w i d changes in thc pressure ratio across tho gas gcncrator compressor, each of the curves nprcscoting a constant bypass ratio. As illustraled, curve A represents a constant bypass ratio, curve B a higher bypass ratio, and curvc C n still higher bypass ralio. From thc graph, it will bc wen that a turbofan cngine having a c o m p r s o r prcssurc ratio of a and a bypass ratio delermincd .by curvc A can produce n net thrust of n mensurcd along the vcrtical axis of the graph. By increasing the gar generator picssurc ratio to a', tbc ncl thrust is increased to the value represented by a' on the vertical mis. From FIG. 1, it would thcrcfore appear that it is a simple mafler to increase output thrust of a turbofan eoginc by going to ever highcr prcraurc ratios. In practice, howcver, it is found that tbe attainable ncl output thrusts of actual turbofan engines v.uy significantly from thcorclical values at high pressure mtios. This nclual variation is iilustralcd by FIG. 2. Referring now to FIG. 2, curve A rcprerents the nct ti~rust theoretically obtainable at various comprcrsor pressure ratios for a turbofan engine having a conrlant bypass ratio. In other words, curve A corresponds to one of the curves of FIG. 1. Curve B rcprcrcnts the actual variation in net autput tbrunt wilh compiesror prcrrurc ratio for an actual turbofan cnginc having tho some bypass ratio nod not utilizing thc improved thermodynamic cycle of the present invention. It will be ootcd from the grnph that curve B corresponds very clos~lywith tho theoretical cum8 A a t relatively low prcsrurc ratios. At highcr pressure ratios, however, the net output thrust drops afi rapidly, the reason for tbc dccrcase io thrust being the practical lempcraturc limitations discussed above. At pressure ratios of less Lhm 0, the maximum possiblc amaunt of hcat can be added in thc cngine combustor without producing tempcrnturu which sxcccd tho maximum tempcralures which the various turbine elemcnts arc capable of wilhstaodiing. A t prcssure ratios greater than a, however, the isentropic comprernion process produccs tempcrnhlres sufficiently high to require fhat the amount of COergY added in tbc combustor be limited. The amount of heat wbich can be addcd in the combustor thus dccrcases witb increasing pressure ratio. At o compressor prersurc ratio of o', thc comprcssor discharge tcmperaturc is almost a3 high as the maximum aUowable turbinc inlet temperature. This meoos that very littie energy cnn be odded in the camhusior; in iact, a t n', the energy added is suRcient to supply losses only. As a result, there is no net output thrust at thc prcssure ratio a'. I t will be obviouli to those skilled in tbc art fhat the prcssurc ratio cannot be incrcvscd above that represenled by a' in an actual turbofan cngins of tho type illustrated by curve B sincc such nn cnginc cannot cvcn be self-sustaining a t such a prcssurc ratio without producins tcmPeralures which excccd the maximum e m Pcralures the turbine elements arc capnble of withrtmdiug. The turbofan arrangement of this invention makcs possiblc the usc of an extremely high pressure ratio engine without praducing cxtrcmcly high comprcssor discharge temperatures which would wvcrcly limit the amount of hcat added in the combustor. In accordance with the present invention, the compresscd fluid is cooled in a heat cxcivngcr prior to being supplicd to thc combustor at a high preslure. As a rcsult of the woliog, mare encrsy cno be added by the combustion process at high prcssurc p t i o s without producing excessive tcmpenturcr. The overall cycle efficiency is not, howevcr, ndverSEly aifcclcd since tbs prerrnt invention u s u thc turbofan bypays fluid to cool thc high tcmpcraturc compressed molive fluid, the hcat removed from thc compressed fluid increaring the e w g y of thc bypass flrrid, which i mixed with . the hot cambustion products issuing i m m the turbinc lo produce the total propulsive thrust. Curve C of FIG. 2 illurlratcs the variation in net output thrust wilh pressure ratio for a turbofan conswclcd in accordancc wilh the present invcolion. I t will be noted Ihat curve C corrcsponda clowly with the theorctical curve A over n much broader range of pressure ratios thnn the curvc B reprercnting the thrust variation of prior art turbofan eogines. It will be obvious to tharc rkiilcd in the art that a oumbcr of various arraosemcnlr of cngine components can bc used to practicc tbc invention. Tbc invention will be described in detail witb respect to FIG. 3, which whcmatically illuswales n preferred embodiment of the invcnlion. h illustrated by FIG. 3, a turbofan engioc 10 bas a cylindrical outcr casing 11 having nn inlet opcning 12 at one end and an outlct opcning 13 at the other end. A first compressor 14 is mounled within Lhc casing 11 adjacent the inlet I2 and receives a stream of motive fluid thcrcfrom. Thc compressor 14 actually functions as a fan rather than ns n true compressor since it accclcratcs Lhc motive fluid only and does not reduce the flow area. O n tbc discharge side of the compicssor 14, an inncr casing 15 concentric with f h c cnginc casing 11 divides the motivc fluid into aqouter ztrcom rind un inner streurn. The outer stream of high vclocity motivc fluid comprises the bypass streom and ir directed by bypass ducting mcanr through a heat exchanger 16 prior lo being supplied to the engine outict 13. Thc inncr strcam comprising tho main strcam of motive fluid for the engine is supplicd to a sccood compressor 17 in which its prersurc and lemperaturc are iocreaacd substantially. Thc inner duMiog means directs the molivo fluid discharged From tho wmpressor 17 through the hcat exchanger 16 in hcat cxchnngc relation with tho bypass fluid in the outcr duct, after which the cooled motive fluid is supplicd to n third compressor 18 in which its prerruro is raised still further. Fram ihc third sompirssor 18, tbo molivc fluid is s u p plied to the engine combustor 1 9 wilhin which combustion occurs. Because of the cooling the inner motive fluid etrcam in the heat exchanger 16, the fluid supplied l o thc camburtor 19 is at a much lowcr temperature than it would be in prior art turbofan engines having the same prcssure ratio and not utiliriog the prcscnt invention. As a compietc combustion in thc combustor can occur at much higher pressure ratios without producing cxcessivc turbine inlet lcmptmturea. The ovornll efficiency is not materially affected since the energy extracted from the inner stream is not last to the cycle, but increases the cnergy of the bypass stream and thus still produus thrusr. From the combustor 19, the combustio~ produch am supplied to first, second, and third turbincs 20,21, and 22, respectively. The first turbine 20 drives the third compressor 18, the second turbinc 21 drives the recond compressqr 17, nnd the third turbinc 22 drives the Arsl compressor 14 through concentric outcr. intcrmediale, nnd inner drive-shafts 23, 24, and 25, respeclivcly. After passing through tbc turbincs 20, 21, and 22, the combus iioo pioducts are mpplied to thc cnginc outlet 13 for mixing with the bypass fluid and producing output thrust Since the three comprmors 14, 17 and 18 are independently mounted and rotated, the cngine can bc designed such that the compressors are rotated at differ. cnt spec&. In this manner, the Buid flow characterijtirr can bc controlled during off-dc~ign operation. Therefore, cxtrernely high p i e ~ s u r e ratios can be ntijmtd without in. troducing lignificam comprcssor stall difficulties. In the foregoing dihcussioo, the heat exchanger 16 has not been described in detail. This har. been donc by design since many diffcrcot fonns of heat exchangers can be used in practicing the invention, the only rcquiremeot being that the bypass Buid be used to cool thc main strsam of high tcmperohlre comprclvrd motive fluid. In practice, howcver, thc heat exchaoger 16 is preferably nnnuiar.

4

6

lo

16

20

26

30

36

40

46

60

66

(10

a5

70

76

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5

.

~

6
A g ~ turbine poverphnt comprising, in wmbination: s ( a ) ao ialcl far admitting motive Buid iola mid poaernimt and an axially spaced oullct for cahaustiog the i o t i v c fluid from s-aid powerplant; f b ) a h axial flow mmpnssor connected to said d e t l for receiving motive fluid therefrom; ( c ) Rrst and sccond ducting means dcfiningindcpcndent concentric annular axially extending Bow passageways connccLing the outlet of said first axid flow compressor to said paworplant outlet, each of said ducting means n m g e d to receive a portion of the total flow of motive fluid from snid first c o m p m o r , the pessagcway d c h c d by said &st ducting meens surrounding the passageway d c h e d by said xcond ducliog means; ( d ) second and third axial flow compressors; ( c ) a bent erchmgcr having Rrst and second sets of indcpendcnl ~ U S J S C S thcretn, said fint r l of pnsroges forming a portion of raid Grrt ductrng means and said rccood re1 o f pnrrogcn fonning o poilion of soid sccond ducling means, said first and rccood scts of pasages being disposed io beat cxc5mge rclaliousbip; i f ) a combustor: &st, second; and third axial flow turbines; ( h ) nn outer driveshaft, said first turbine and said third compressor mounted on said outer drivcshrdt for rotation thercrvilh; (i) an intermedlatc driveshaft concentrically mounted within said outer drivcshaft, soid second wbic and snid sccond compressor mounted on said intermediate driveshaft for rotation therewith; (i) an inner driverhaft wncenlriwUy mounted within raid intermedlntcdrivcshsff, said third turbine nnd said first compressor mounted on said inner driveshaft f o r rotation therewith; (k) said first ducling means ~OMccling said f i s t wmpressor, said heat exchanger, and said powerplant outIct in serial flow a ~ a n g c m c n t , and said sccond ductin0 means connecting said f i s t compressor, said second compicssor, said heat cxchangcr, said third compressor, said combustor, said first turbine, said seeond turbine, 8aid third turbine, and said powerplant outlet In serial flow arrangement; (1) whereby the motive fluid in said first ducling means is healed and the motive fluid in said sccond ducting mcans is coolcd as a result of hcal trsnsfer therebetween in the passages of said heat exchanger.

The Buids can be passed through the heat exchanger in essentially parallel paths as illnslrated. If desired, however, allcmativc Bow arrangements cun he used for providing more eGective heat t r w h r . For example. each of could be directed ththrough the heat uchanger 5 the stretwice in rndial counterilow passes. It is thus m n t i a l that there be two sets of independent passages dispoxd io heat uchnngc rclntiomhip wilhio the heat exchange, the bypass Buid flowing through one set of passagcs and the c o m p m e d fluid Rowing through thc other set of pussages. lo As pointed out previouily in thu description, it will occur to thore =killed in the ntl that allemativc structural arnngemcnts of engine componcnk c m be utilized to practice the invention. Three such &emalive arrangements arc illustrated by PIGS. 4, 5, and 6. In view of 15 the detailed description of the powerplant illustrated by FIG. 3, these nrrangcments will not bc desc"hcd at length. For thc most part, tha d e p a m r m only from the turbofan engine of FIG. 3 will he pointed out, the components simliar to componems of the engine of FIG. 3 bcing i - 20 n dicated by similar numerals. Turning now to RG. 4, it will bc noted that the illustrated turbofan enginc diGcrs from the engine 1 0 of FIG. 3 only in that the third high pressure comprcssor 18, its driving Nrbinc 20. and connecting driveshaft 23 have 25 been deleted. In the enginc of FIG. 4, the high tempcralure compressed air dischnrgcd from the compressor 17 is cooled by tho bypass fluid prior to btiog supplicd to lbe combustor 19. I n view of the foregoiog discusrion, it will bc obvious that the engine illustrated can safely 30 operate s t bigber pressure ratios than prior art turbofan engincs not equipped with the bypass heat excbnnger ,

(6

. 10.

T h s turbofm eogine illustrated by FIG. 5 is aubstantially identical to the engine of FIG. 3 excapt in that both the flrst comprcssor 14 and the second compressor 17 nn driven by B single turbine 30 through n d~iveshafl31. A gcnr rcduccr 32 is provided bchvcen the hva wmprcssors so that the Rrst comprcssor 14 can bc driven at a slower speed than the sccond comprcssor 17. It will also be obvious that all three compresson could be driven by a single turbine if deslrcd. Referring now to FIG. 6, an alternative first wmpressor IJ' is illustrnted in which the first few rotor stages have enlongsled blades whore outer exhrmiliu act a, a fan for the bypass duct. Tha downstream singes nre shorter and compress the motive fluid flowing through the powcrplant's i ~ c stream. r I t will thus he seen that the turbofan engine nrmngemenk just described are capable of producing high net output thrust and efficiency a t extremely high preuure ratios since motive fluid is supplied to the enginc combustor a t a rclativcly low tcmpcrature. As a result, complcts combustion can be maintained at high presure ratios without producing uccstiive turhinc inlet temperatures. As pointcd out previously, other embodimenk of the invention may be utilized. Thercfora, whilc pnrticular smbodimenk of t h t invention have been shown and dcscribed, it will be undcrslwd h t it is intended to cover in the sppended claim ail modifications and changes which may be made without departing from the spirit and scope of the invention. What is claimed as ncw and desired lo x c u m b y Leltcn Patent of the Unitcd Slates is:

3s

40

46

60

65

2,430,398 2,430,399 2,465,099 2,588,512 2,638,744 2,803,943 994,130 793,316

References Cited by the E d n c r UNITED STATES PATENTS 11/1947 Hcppncr ---------.-60-35.6 11/1947 Heppncr ------------ 6 G 3 5 . 6 3/1949 Johnsan -----------.. 3 5 . 6 6L 3/1952 Johnson 6k35.6 5/.1953 Price -------------- 6 L 3 9 . 3 3 7/1957 Rainbow ----------- 60--35.6 FOREIGN PATENTS 7/1951 France. 4/19-58 Great Britain.

------.-----

MARK NEWMAN, Primary E.rarniner. CARLTON R. CROYLE, Emminer.

DA90