US2910269A

US2910269A - Axial-flow fluid machines

Info

Publication number: US2910269A
Application number: US631887A
Authority: US
Inventors: Haworth Lionel; Petrie James Alexander
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1956-01-13
Filing date: 1956-12-31
Publication date: 1959-10-27
Anticipated expiration: 1976-10-27
Also published as: GB804922A; FR1164080A

Description

Oct. 27, 1959 L. HAwoRTH ETAL 2,910,269

AxIAL-FLow FLUID MACHINES Filed Dec. s1, 195e llllllllm United States. Paw/H2O "we o AXIAL-FLOW FLUD MACHINES Application December 3'1, 1956, Serial: o. 631,3@

Claims priority, application Great Britain January 13, 1956v s Claims. (ci. ass-49) This invention comprises improvementsin or'- relating to axial-flow fluid machines, such as, forexample, axialow compressors. and turbines of gas-turbine engines.

This inventionA has for an object to provide a construction of axial-flow fluid machine in which difficulties experienced with known multi-stage machines due toz distortion and relative thermal expansion are avoided.

'According to the present invention,- amultistag'e axialflow fluid machine comprisesV rotor means` including a plurality of axially-spaced rows of'rotor blades; and a stator structure enclosing. the rotor means and comprising a main casing, and. a plurality of axially-spaced rows of stator blades or vanes, there being one row of said' stator blades or vanes just upstream ofeaclh row' of said rotor blades,- the. stator blades being provided at their radially-outer ends with platforms tofornr pai-t'sof the wall ofthe' workinguid annulus of the' machine around the, stator blades ori varies,` each said platformlbeingvv siip-A ported'i'frorn the main casing, andthe platforms of'adjacentJ rows of said stator blades or vanas-'having aligned axial extensions which togethernalfordrlan annular stator shroud: encircling the: tips of the row -of rotor blades iri-l termediate they adjacent. rows of stator bladesl or varies.- By faligned?v is meant. that the extensions of adjaeer'it`A rows" of stator'bla-des have parts at substantially the' sarne Iradialv distance from theraxis` of rotation of thev rotor j means,.which thus co-operate to afford said shroud;

Heretoforie it; has been the practice toy provide an annular shroud of substantially the same axial dimension as the rotor blades, which encircles the rotorv bladesand is formedin a small number of arcuate pieces; say'six; with such an arrangement not only are diicult-ies experienced in design in order to allow for thermal expansion but it has been found thattheseV pieces are liable to distortion inV operation of the machine. These diniculties are. avoided by the vconstruction of the present invention.` l Y v j The invention is applicable both to machines' whereof the rotor blades have integral' shrouds at their: tips,l and to machines whereof' the rotor blades are not provided with integral shrouds,

According to a preferred feature of the invention, the rotor bladesl have" integral tip' shrouds, Vthe axial extensions of the platforms at the radially-outer ends of the stator blades are radially offset from the radially-inner surfaces of the platforms, thereby to provide achannel into which the integral tip shrouds of rotor blades extend, and the integral tip shrouds are arranged to co-operate with the axial extensions of the platforms'to provide gas seals to prevent excessive flow of working uid around the tips of the rotor blades. In the preferred arrangement the integral vtip shrouds have on their outer surfaces axially-spaced ribs which have radial surfaces, and'there are provided radial surfaces on the axial extensions of the varies, which have for gassealing purposes small axial clearances from the radial surfaces on the axiallyspaced ribs, all other clearances between the tip shrouds 2,910,269 et..V 27,. 1959 and the axial extensions being substantially gieat'i' said small laxial clearances` 'Y one embodiment er this inventiit linee vbe dei scribed' Y'with reference to 'the aceornpflying' drawing, which shovvs in axial' section part 'of an axial-now i'l'tisttifgetureiiie. Y

The turbine comprises the rowsY offiot'o" blades 10; 11, meunted aft t tpm-,ries er esifesponaing iot'oi dises; andi a stator v'structui'e including a rc'asliii'g 13v andE tlirer ws' f izle guide varies 14, 15,116", the ravis et gti-ide:

vases

14, 15,- 1eV Being fes'peetiveryjjt upstream of the rows ef the' iotereldes 10,11, 122. L

VThe guide vanes have both inner and outer

bladepl forms

14a, 14b;,15a, 15b; 16a,`16b, and the ilir blade p'latfoit'sy 142i; 15a', 16a of each; row aie 'secured rigidly tegetlieiin annuliyassjetiibiy: by Suitable strutture. lThe outer blade?pllatter-"ni"S1421,Y 15b, 16h` of each row are'fre frein one another.Y Y y n n l l The high-pressurel nozzle guide vane's 174' 'have' oat'er platforms-146 fixed axially an circumf'erentitrlly with respect to'tle casing 13 but left `free 1`tadial-ly'. For this'- pu'rposa the casing 1131 is provided outsidev the roteir blades 1'# iivitliaj radially-inwardly-projectiiig annular'. rib 17 frn'ed with a"inwardlyfacing annular` 'clianne'l'x 8f, andthe blade` platforms 14b` are provided along their downstream edges with axial extensions 19frw'hicl`1'telriii'-l than 19t-intr zsiiieetiitg with Slight clearance-andeeieg'rdiauy onset from the inner' initiates` ofthe platforms i425; 15b te pif-avide tf channel 23a receivingtip siiftids 221 ein theA Bla roaj'ffne'A radially'{it'tjrneri surfaces fL tl'e 'i exten' r9; areY snapt-: 1 teY affetti" at' parer radial' plane snrffa'cles 19t; which; in' epe-tation df the machine' havef-'axial ,clearances froinf corresponding ra'li'al siii"- fties'zs sir aaiaiiyspaeed iatiiauy oiitwatdiy'feiteiiditfg l j fofprovidegais-seals1i tiiiggtiie new afwerkinginiidi aroiidtlietiti istiretidsl--w t t Thea-varies" 1s;- 16'fre'1'ocatediti tite s'in'gr'sf ifi's'innar ways. Y Thus` etten van@ 1s; lsa's on itsfpitfriii 15b-ei rsbtadjaeent its upstream and dewnstieaa edges' hooked'fom'tion's 2517281 29j 3( )`"whi"cli engager'espectively; in axially-rating eliminar' ehnnels 31332; 33; 34", theF @nati-nels seing frnied respectively iiittie radial ri 17.'Y and tnreefrtheif ribes-'5, 36; 37' providea any off tite-'easing 132 T efpiatfqrms `155,155ar'ethuslcated? 'r`-z`1`dially. The ri-bs" If, 35;, 36and` 37varLe' alsoiprl' vided with radially-inwardly-projecting dogs 38 co-operating with dogs 39 on the platforms 15b, 16b to locate them circumferentially. The platforms 15b are also l0- cated axially .by axially extending ring members 40, 41 extending toward each other between the ribs 35, 36 and abutting radial flanges 42 on axial extensions 43 of the trapped between the rib 37 and a ring 50.

` The blades 11 have tip shrouds 24 and stator shrouding for these rotor blades is provided in amanner similar to that described for the blades 10, by the axial extensions 43 of the platforms 15bA and axially-aligned cooperating extensions 44 on the upstream edges of the 'edf on theV outer Sartenes ef tnetip sii-ferias i Y, `amazes platforms 16b, the extensions 43 being shaped Vto alford plane surfaces l25 on ribs 26 such as to afford gas seals to prevent excessive leakage of gas around the tip shroudsZ4. ky I It will be seen that the platforms 14b, 15b, 161: of the guide vanes are spaced radially fromthecasing 13 and cooling air is fed into this space from between the casing 13 and the nozzle discharge chutes leading from the flame tubes of the gas turbine engine to the high-pressure nozzle guide vanes 14. The air passes through the ribs 17, 35 and 36 by means of

drillings

45, 46, 47, therein and also through cut-away portions on the hooked

formations

28 and 29, and through drillings 48 in ring member 40. The air passes into the working fluid channel through the small clearances between the platforms 14h, 15b and 16b.

:We claim:

l. A multistage axial-dow fluid machine comprising rotor means including axially-spaced first and second rows of rotor blades and a stator structure enclosing the rotor means which stator structure comprises `a main casing having internally thereof a series of axially-spaced inwardly-projecting circumferential ribs, artirst row of guide vanes upstream of said first row of rotor blades, a second row of guide vanes in flow series between*` said first and second rows of rotor blades, each of said guide vanes having an inner platform and an outer platform, means rigidly securing the inner platforms of the first row of guide vanes together in annular assembly, means rigidly securing the inner platforms 4of the secondl row vof guide vanes together in annular assembly, each of the outer platforms of the first row of guide vanes having an axial downstream extension projecting downstreamtherefrom axially part way over the outer endsof the first4 row'of rotor blades and, at the downstream end of said downstream extension a radial flange, one ofv said ribs of fthe main casing having an inwardlyfacing annular channel engaged by saidradial` flanges to locate the first row of guide vanes axially in the casing and also having a downstream-facing annular channel, means locating the first row of guide vanes circumferentially in themain casing, each of the outer platforms of the second row of guide vanes having an axial upstream extension projecting upstream therefrom axiallyl part way over the outer ends ofthe first row of rotor blades and terminating adjacent the downstream ends of said downstream extensions of the first row of guide x/anes, each of the outer platforms of the second row of guide vanes y.also having radially outwardly-projecting hooked formations adjacent both its 'Y' outwardly projecting flanges, and a pair of ring members, planeA radial surfaces 24 which havel clearances fromY upstream edge and its'downstream edge, the hooked for-` mations adjacent the upstream edges engaging said downstream-facing annular channel of said one rib,- a-second of said ribs of the main casing havinga downstreamfacing annular channel engaged by said hooked formations adjacentthe downstream edges ofthe outer plat-k forms, lsaid outer platforms of the second rowv of guide vanes and one of said ribs also having interengaging'dogs locatingthese guide vanes circumferentially in the casing, and each of said outer platforms of the second l,row of guide vanes having at their downstream edges radially- .one oneach of the upstream and downstream sides of the radially outwardly projecting flanges, each of said ring members axially abutting by one end the radiallyoutwardly projecting flanges and by the other end said main casing to locate the second row of guide vanes axially in the main casing.

2. A multi-stage axial-How uid machine according to claim 1, comprising a third row of guide vanes downstream of said second row of rotor blades, which guide vanes have inner and outer platforms, means rigidly securingthe inner platforms of the third row of guide vanes together in annular assembly, each outer platform of the third row of guide vanes having at its upstream and downstream edges radially outwardly projecting hooked formations, a third of said ribs and a fourth of said ribs each having a downstream-facing annular chan nel engaged respectively by the hooked formations at the upstream edges of the platforms and the hooked formations at the downstream edges of the platforms, means maintaining said hooked formations in the annular channels, and interengaging dogs on said ribs and the outer platforms of the third row of guide vanes to locate them circumferentially on the main casing, downstream axial extensions of the outer platforms of the second row guide vanes axially projecting part way over the second row of rotor blades, and upstream axial extensions of the outer platforms of the third row guide vanes projecting axially upstream and terminating adjacent the downstream edge of the'downstream axial extensions of the second row guide vanes. l3. A multi-stage axial-flow ud machine according to claim 2, wherein said first and second rows of rotor blades have integral tip ,shrouds at their outer ends, the tip shrouds having axially-spaced radially outwardly projecting ribs which have at their outer ends upstreamfacing radial surfaces, wherein said axial downstream extensions of the outer platforms of the first and second rows of guide vanes and the axial upstream extensions of the outer platforms of the second and third rows of guide vanes are radially offset outwardly from the inner surfaces of the outer platforms to form channels receiving the tip shrouds of the rotor blades, and wherein the axial downstream extensions have each a pair of axiallyspaced downstream-facing radial surfaces having small axial clearance from the upstream yfacing radial surfaces of the ribs on the tip shrouds to provide gas seals, the remaining portions of the tip shrouds having a substantially greater clearance from the stator structure than s aid small axial clearance.

I References Cited in the file of this patent UNITED STATES YPACI`EN'-1`S 911,616 Roth -i Feb. 9, 1909 1,482,031 Parsons Ian. 29, 1924 2,314,289 Salisbury 1 Mar. 16, 1943 2,488,875 Money -v Nov. 22,1949

Y FOREIGN PATENTS 200,055

l, Australia Nov. 4, 1955