US2923525A - Hollow gas turbine blade - Google Patents

Description

Feb. 2, 1960 J. o. CREEK HOLLOW GAS TURBINE BLADE Filed April 4, 1958 FIG. I

FIG.3

mvewron J. o. CREEK BY: ATTORNEYS 2,923,525 HOLLOW GAS TURBINE BLADE John Oliver Creek, Brampton, Ontario, Canada, assignor to Orenda Engines Limited, Malton, Ontario, Canada, a corporation of Canada Application April 4, 1958, Serial No. 726,382 4 Claims. (Cl. 253-3945 7 This invention relates to hollow gas turbine blades.

. -It is well known that one of the factors limiting the efficiency of gas turbine engines is the restriction imposed upon the maximum gas temperatures that maybe employed by the ability of the blading to withstand these temperatures. It will be therefore appreciated that if the blading can be adequately cooled, higher gas temperatures can be employed with an increase in eificiency; alternatively, or in addition, inferior or more common materials can be employed in. the construction of the blades. In addition, due to the high rotational speeds of modern gas turbine engines, it is desirable to employ agas turbine blade which is light in weight and the hollow gas turbine blade achieves this desirable result. Hollow gas turbine blades are, in the main, rather difficult to manufacture since they involve either complicated-castings or intricate work with sheet metal components. g 1

It is an object of the present invention, accordingly, to provide a hollow gas turbine blade which is relatively simple to manufacture and which will possess the advantages of rigidity, dimensional stability andstrength of the-solid blade while possessing'the advantages of lightness in weight and the ability to be cooled of a hollow turbine blade.

The invention will be described with reference to two embodiments illustrated in the accompanying drawings in which like reference numerals denotelike parts in the various views and in which: a

Figure 1 is a top plan view of a gas turbine blade made in accordance with one embodiment of the invention;

Figure 2 is a perspective view of the blade shown in Figure 1 with part of the side wall cut away to show the internal construction;

Figure 3 is a top plan view of a gas turbine blade made in accordance with a further concept of the invention,

-and

Figure 4 is a perspective view of the blade shown in Figure 3 with a portion of the side wall cut away to show the internal construction.

Before proceeding further vwith the specific'descn'ption of this invention it is believed desirable to define certain terms which will be given a specific meaning in the following specification and in the claims.

Gas turbine blade.In the present specification the term gas turbine blade is intended to mean a blade or bucket adapted for use'in a gas turbine engine. as either a compressor rotor blade, a compressor stator blade, a turbine rotor blade or a turbine stator blade. More specificallythe term gas turbine blade is intended to. denote primarily the aerofoil portion of the blade as distinct from the root portion of the blade, the present invention dealing only with the aerofoil portion which may be fitted to any conventional form of root or, alternatively, may be employed in certain environments Withoutaconventional root of anykind.

with reference to the particular blades described in the present application is that side of the bladewhich, over;

its external surface, is of concave configuration.

Convex side of blade.,-Th,e convex side of the blade:

described in the present specification is that side of the blade which, over its external surface, is of convex con-' figuration.

lnner.When used in the'specification and claims an inner surface is any surface which is substantially parallel to the immediately adjacentexternal surface of they blade and which surface faces away from that external surface towards-a point mid-way between the adjacent surface and the opposite surface of the blade.

0uter.When used in the present specification and in the claims the termouter; such as outer surface denotes a surface which faces away from the interior of the blade.

ParalleL-In the present specification and in the claims the term fparallel is intended to mean that two lines, surfaces or edges lie adjacent one another and are always the same distance apart throughout their length rather than being given the classicaldefinition of two lines which, no matter'how' far extended, never intersect. 1

Having clarified the use of the above terms it will now beconvenient to refer to Figures-1 and 2 of the accompanying drawings which illustrate a gas turbine blade made in accordance with the present invention.

Referring in particularto Figure 1 a hollow gas tur-.

bine blade 10 will be seen to. comprise a- .skin S10 formed from a piece ofsheetmetal bent over upon itselfalong afold line, the fold linecorresponding with the leading edge 11 of the blade, .the skin 8' being formed to have a convex side 12 and a concave side '13, two;

edges of the skin srsubstantially' parallel to the fold line' being. joined together 'to 'form'. a atrailingidge 14. The edges of the skin S may be joinedstogether' to form. the'trailing edge 14 byaany suitablezimeans such as brazing.

The hollow interior of the blade will be seen to be; divided up into a plurality of spanwise passages 15A,

15B, 15C, 15D, 15E and 15F by means of spars 1,6

7 extending across -the-thickness;of theblade through the hollow interior. Each of passages ISBHtoISE inclusiveis divided .into.

three passages by means of a pair of baffles 17 and 18j .which divides each of passages 15Bqto -15E inclusive I into sub-passages indicated by-reference characters x, y. and 2. v, ,7 1;;

Re'ferring-now to Figure 2 it will be seen that the; convex side 12 of the skin Sis provided with a plurality.

of spaced, parallel ribs '16 extendinginwardly. from :the

- 16 extend through apertures in the bafileg17 into the space inner surface 12a of the convex side 12. r The baffle 17 is secured to the inner surfacelfia of these ribs 16 and, thereby, is held in spaced, parallel relationship to thc convex side 12 of the blade. Projections 19 on the ribs between the bafiles 17 and 18 as seen in Figure 1. 'Any' given projection 19 onany given rib 16 engages and is secured to a corresponding projection 19:; on a corresponding rib 16 on the other side of'the blade 10 so,

, that, as seen in Figure 1, there is; a direct connection LConpavc side of blade..-Th.cbn08e.side of the blade,

between the convex side 12 of the blade andthe concave side 13 through the projections 19 and 19a on ribsj16'.

It will further be observed that there are an even. number of spaced, parallel ribs 716 formedintegrally with the convex side 12 of the skin 8, the fold' line. cone,

stituting the leading edge of the blade ll dividing the plurality of ribs' into a first setintegral with the inner surface of the convexside of the blade andga second set integral i the inn q iacc o the nc ve side 13 of b ade nd. equal numberrto the first. set- The Patented Feb. 2, 1960 second--set-of ribs is directly-opposed to'the firstsetof ribssso that the projections 19 on the first set, extending into the spacebetween the baflies through apertotfi'e-crrespondingprojections ribs extending into the s ace aperturesiri thes'econdibafliem; l i I Referring now to Figuress and'4 an alternative em bddiment of the invention' will be described. t This alter native embodiment will be seen, in substance, to' beve'ry similarto that described with reference to Figures 1 and 2 and constitutes a bladelo having aaskimS'which" includes a convex: side 12, a concave Side" 13, a leading edge Hand, a trailing edge 14; The"convex sideof' the provided with a first 'set of blade on its inner surface"; is 7 v v 16 extending 'inwardly from the spaced, parallel ribs interior surface and thes concave side of the blade :is

of the ribs and are secured thereto. Each ofthe ribs.

19 which extend: A

16 has a plurality of projections through apertures 20 in the baffles 117 and 118 and engage the corresponding'projections 19 on the. directly. opposed ribs 16 on the other side of the blade.

of the blade into 'a plurality of brazingoven andbrazed into it a single unitary structure,

It is believed that a novel ;;and improved form of gas turbine blade has been described in the present specification which is intendedto be construed in an illustrative manner, minor modifications being contemplated by the invention within the scope of the-appended claims.

What I claim as my invention is: g 1. A hollow-gas turbine "blade comprisingta one piecc skin of sheet metal havinga.convex side, a concave side a'leadiilg edge and'a tranmgeagea first set of at least two spaced ribs extending spanwise ofthe blade and extending inwardlvfrom the interior of the convex side, a

and spanning the space betweenthe ribs, a second set of at least two spaced ribs extending spanwise of the blade and directly opposed to the first set and extending inwardly from the interior surface of the concave side of theblade,-"a secofid'sheetnnetal bafile secured to the inner-surfaces of the s'econdset of ribs spanningthe space between them and spaced fro'rn the first baffle, and spaced projections' on the first-set of ribs extending into the space".

between-the 'baflles through 'apertures in the firstbafile' and secured toprojections' on the second set of ribs ex tending'into the space; between t the baffles throughaper -2A hollowgas turbine' blade comprising a one piece skin of sheet-metal havinga convex side, a concave side;

' 3 a'leading edge aiid atrailing edge, a first set' of atfleast The difference between the embodiment shown in Fig V ure's 1- and 2 and the embodiment shown inFigu'r'es'B and 4, is-that the baffies 117 and 118 are displaced out wardly between adjacent ribs 16 soithat over that distance between adjacent ribs they lie closer to the skinnof the. blade than at the point 21 where they are secured tothe.

' a'second set-eras leasttwo spaced ribs extending span-' surface 16 of theribs 1'6.

Referring. now to Figures '1 and Bit will be seen that the baffies 17 and 18 and 117 and 118 are secured to-- gethe'rwalong. a line' substantially parallel to the. leada ing edge, theline lying between the leading edge '11 and that rib 16 adjacent the leading edge 11 and, at;their' trailing edges, are secured together at 22- along aflline substantially parallel to the trailing edge 14; the line lying between the trailing edge 14 of the blade, and that rib 16 adjacent the trailingedge 14 ofthe blade.- Thus, spanwise passages 15A and 15F are not divided into threes'ub passages x, y andz asare passages 15B @155 inclusive, H

' ,The blade manufactured in accordance with th mes ent- 'iriveiition possesses certain advantages over-othcr light "as a blade made from sheet metal it is mdreafigid diie re the" fac'tthat the ribs 16, in conjunction with'the" projections 19, provide for integral spars joining; the convex surface 12 with the concave surface across" the thickness of the blade 10. In addition, certain rigidity is imparted tothe blade by virtueof the baffles 17 and 18-and [117 and 118 which'are brazed to thefsurfaces 16ii'of the ribs 16;within the hollow interior of the'blade. The bracing afforded by the ribs 16 and the projections 19 provides'a greater dimensonal" stability inthe blade" than 'has heretofore been obtainable' in blades of sheet r'netalconstruction; The blade described in the present application 1 is quite simple to manufacture, the manufachiring process cbmprising the steps ofmachining the ribs 16 -ii'1 a flat sheetof materialfthere being provided an equal number of ribs on'either sideof the fold line11, maehifiiiigtheheight of the ribs so asto provide for a suit ame-se rofeir cross-section when the sheet is folded over upenx itselffalong the fold line, 'folding the sheet to' the configuration shown in Figure 1 or 3,- 'seeurihg the twoispacedribs extending spanwise of thetblade and" extending"inwardly from-the interior of the convex side;

slih over the distance Between the" -rib"s so that it lies closer to the skin of the blade between theribs than at;

the pent where it contacts ar'id' i's secured to theribs,

wise of the blade directly o posed tdthe first set and extending inwardly from the interior of the concave side? of the blade; asecond sheet metal baffle spaced from thefirstsheetdnetalbaflie securedto' the second scrofj ribs and spanning the space between them, thesecond baffiebeing displacedtoward the skinflof the blade over the distance between the ribs so that it lies closer tothe skin of the blade'between'the ribs than at the'point where it is secured to the ribs and projections" on the "first set types of hollow gas turbine blades in that, although as l or ribs *'extending into" the: space between the' baffles through apertures in the first baffieandsecur'edto' projec tions on the second set of ribs extending into the s ace between thebat'fles through apertures in'ithe second baffle. a f

3. A hollow gas turbine bladeas claimed in-"clair'ni in which one frib of each of thefirst and secondset lies,

twe eages cr me shee together awngne trailing dge 14 after navnrg' srsz in nee meqbamesi'laiid 18for ad acent theleading edge of'the 'bladeand another rib of each of the first and second set lies adjacent the t-raile; ing edge ofthe blade." g

4.A' hollow gas turbine bladeas claimed in claim-*3 wherein the sheet metal bafiies are joinedtogether along a' line substantially parallel to the leading," edge .ofthe blade, the line lying 'between the leading edge of the blade andthat'ribofieach set adjacent the said leading, edge andalso joined together along a line substantially" parallel to' the trailing edge of the-blade, the line lying between thetrailingedge and that rib of each set-adjacent' the said trailing edge, of the blade;

References Cited in the-:file of this patent UNITED STATES PATENTS 2,779,555 Brucki'n'an Jan. 29, 19.57" 72,737,049 Stalker Apr. 2 ,"19'572 2 ,823,892 Gerd'an' Feb. 18,1958 A wFO'IiEiGN PATENTS j GreBt 'Bfitain--- ea;- Ls==.aa-N0W 15 1,2217:- Great hriteinessasss-tss fiugi 8,41%6

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