US3017159A

US3017159A - Hollow blade construction

Info

Publication number: US3017159A
Application number: US623943A
Authority: US
Inventors: Foster Tom; Werner E Howald
Original assignee: Curtiss Wright Corp
Current assignee: Curtiss Wright Corp
Priority date: 1956-11-23
Filing date: 1956-11-23
Publication date: 1962-01-16
Anticipated expiration: 1979-01-16

Description

Jan. 16, 1962 T. FOSTER ETAL HOLLOW BLADE CONSTRUCTION 4 Sheets-Sheet 1 INVENTOREI TEIM FDEITER WERNER E. HIJWALD M ATTDBLNEY F iled Nov. 23, 1956 Jan. 16, 1962 T. FOSTER ETAL HOLLOW BLADE CONSTRUCTION 4 Sheets-Sheet 2 Filed NOV. 23, 1956 JNVENTOREI v TDM Fun-ran WERNER EL'HDWALD ATTORNEY T. FOSTER E' l'AL HOLLOW BLADE CONSTRUCTION Jan. 16, 1962 Filed Nov. 23, 1956 INVENTOREI TEIM FD ER WERNER E.HD

ATTORNEY 4 Sheets-Sheet 3 Jan. 16, 1962 T. FOSTER ETAL HOLLOW BLADE CONSTRUCTION 4 Sheets-Sheet 4 Filed Nov. 25, 1956 'lll'llll'lll s ,0 o a a o a 6 9 O O G V EN TOR: T M FEISTER D M w .u H v E R E N R E w ATTORNEY 3,017,159 HQLLOW BLADE CQNSTRUCTIGN Tom Foster and Werner E. Howalrl, Ridgewood, N.J., as-

signors to Cnrtiss-Wright Corporation, a corporation of Delaware Filed Nov. 23, 1956, Ser. No. 623,943 3 Claims. ((31. 253-3915) This invention relates to hollow blades for turbines, compressors or the like and is particularly directed to such blades designed for the flow of heat exchange fluid therethrough.

object of the present invention comprises the provision of a novel hollow air-cooled blade for turbines, compressors or like apparatus such that high cooling efficiency of the blade is provided. A further object of the invention comprises the provision of a hollow air-cooled blade in which the blade is provided with a plurality of passages each controlled by a restricted discharge orifice disposed along the trailing edge of the blade. With this arrangement, the cooling air passages all discharge into the surrounding fluid in a region of substantially known pressure velocity and temperature thereby permitting accurate control of the cooling air flow through each passage. Also because of the restricted discharge orifices the cooling air discharges from the blade trailing edge at high velocity thereby insuring good cooling at the normally hot blade trailing edge. Furthermore, by properly proportioning the relative areas of the restricted discharge orifices of saidblade passages any desired distribution of relative magnitudes of the mass air flow through the blade passages can be obtained. Thus with the present invention it is possible to provide for a substantial amount of cooling air flow along the normally hot leading edge of the blade.

Other objects of the invention will become apparent upon reading the annexed detailed description in connection with the drawing in which:

FIG. 1 is an axial sectional view through a gas turbine rotor having blades embodying the invention;

FIG. 2 is an elevation view of a blade embodying the invention;

FIG. 3 is a side View taken along line 33 of FIG. 2;

FIGS. 4, 5, 6, 7, 8, 9 and 10 are sectional views taken along lines 44, 5-5, 6-6, 77, 8-8, 9, 161t} of FIG. 2, respectively;

FIGS. 11 and 12 are elevation views of the inner surface of the two halves of the blade prior to their assembly;

FIG. 13 is a view similar to FIG. 2 but illustrating a modified structure; and

FIG. 14 is a sectional view taken along line 14-14 of FIG. .13.

Referring first to FIG. 1 of the drawing, a gas turbine rotor has a plurality of circumferentially-spaced blades 12 secured to and extending from the periphery of the disc portion of said rotor across the flow path of the turbine motive fluid. A shroud 13 forms the outer boundary of said flow path. For the purpose of supplying cooling air or other cooling fluid to the turbine blades, an annular shroud 14- is co-axially secured to :a plurality of bosses 15 projecting axially from the disc portion of turbine rotor. The inner edge of the shroud 14 terminates short of the hub of the turbine rotor to leave an annular entrance 18 for cooling air flow into the space between the shroud 3,fll?,l59 Patented Jan. 16, 1962 14 and the turbine rotor. A plurality of radially-disposed and circumferentially-spaced vanes 19 may be disposed between the shroud 14 and the turbine rotor 10 to help blow cooling air from said air entrance 18 to the periphery of the turbine rotor disc and thence into the root ends of the turbine rotor blades 12 for flow through said blades. The outer edge of the shroud 14 engages flanges 15 on the rotor blades 12 and projecting axially upstream therefrom for restricting said cooling air to flow into the root ends of said blades as hereinafter described. The structure so far described is largely conventional and, for example, is more fully illustrated in copending application Serial No. 557,051, filed January 3, 1956, now US. Patent No. 2,951,340, and the cooling air flow may be regulated in the manner described in said copending application.

The details of the rotor blades 12 are illustrated in FIGS. 2-12. As hereinafter described the blade 12 is fabricated in two halves 12a and 1212 (see FIGS. 11 and 12) and the junction between said halves is indicated by the line I in FIGS. 3-10. Each blade 12 has a working portion 211 and a root portion 22. The working portion 20 of the blade has an airfoil-like shape for co-action with the turbine motive fluid passing between the blades for driving the turbine. The root portion 22 of the blade is adapted for securement to the periphery of the turbine rotor disc. For this purpose, the root portion is illustrated as having ribs 24 formed thereon to form a fir tree shaped root portion arranged to be received in slots of complementary configuration in the turbine rotor disc. Each blade 12 also has a circumferentially-extending shelf 26 between its working or airfoil-like portion and root portion, said blade shelves being arranged to abut each other to form a continuous annular inner boundary for the turbine motive fluid, the blade airfoil or working portions 21 projecting across the flow path of said motive fluid from their respective shelves 26. The blade shelves 26 are disposed outwardly of their previously described flanges 15.

A cavity or chamber 28 is formed in the root portion of each blade between its shelf 26 and its fir tree configuration 24- and an opening 30 in the upstream side of the blade root portion communicates with this cavity. Each blade opening 31 is disposed on the radially inner side of its flange 15. The blade flanges 15 form a substantially-continuous axially-extending annular flange which is engaged by the outer edge of the aforedescribed blower shroud 14 for causing the cooling air to flow into the turbine blade root openings 30.

The working or airfoil portion 20 of each blade also has a hollow construction. Thus the Working portion 20 of each blade comprises

thin walls

34 and 36 forming the blade convex and concave faces, respectively, said walls preferably having a tapering thickness so that their thickness is a minimum at the outer ends of the blade. In addition a plurality of webs or partitions 38 extend across the hollow interior of the blade from one blade face to the other to divide said hollow blade interior into a plurality of passages 40. As hereinafter described, each web 38 comprises a part 384 formed integral with convex blade face 3 1 and a part 38b formed integral with the concave blade face 36, said web parts abutting and being joined together when the blade halves are joined. At the root end of the blade working portion, the webs 33 3 are spaced chordwise across the blade and said webs extend lengthwise of the blade from its root end for varying distances and then turn chordwise across the blade to its trailing edge 42. The web 38, disposed adjacent to the leading edge 44 of the blade, extends for substantially the entire length of the blade while the lengthwise extent of each of the other webs 38 progressively decreases chordwise across the blade so that the web 33 disposed adjacent to the trailing edge 42 of the blade has the shortest dimension lengthwise of the blade.

A narrow slot is formed along the trailing edge of each blade and the Webs 38 terminate at said slot 45 so that the portion 46 of said slot between each adjacent pair of webs 38 forms a restricted discharge opening or orifice 46 for the passage 44) formed by said pair of webs.

At the blade root portion the webs 38 extend into the root portion cavity or chamber 28 but each web separates into two spaced

ribs

38a and 38b each formed on one face of the blade and each progressively decreasing in height as it extends farther into said cavity so that the root end of each said rib blends into the adjacent outer wall of the blade. With this arrangement, the cavity or chamber 28 in the root portion of the blade is in communication with each of the blade passages 4% so that cooling air supplied to said cavity through the opening 39 flows through the passages 40 and discharges from the trailing edge of the blade through the restricted openings 46.

A web 48 extends chordwise across the blade working portion at its outer end to close said end in order that cooling air cannot discharge radially from the outer end of the blade. Also one or more short chordwise extending webs 5t) divide the chordwise portion of certain of the passages 4h into a plurality of parallel passages to help distribute the cooling air across said passages 40.

With the aforedescribed construction, the airflow through the blade is controlled by the restricted openings 46 disposed along the blade trailing edge 42 for each of the passages 46 so that said restricted openings 46 control the airflow distribution through the blade. Accordingly, the passages 40, with their restricted discharge openings 46, can be designed to provide any desired airflow distribution through the blade which distribution Will be unaifected by change in operating conditions of the turbine. This is in contrast to hollow blades having passages discharging air at the outer end of the blade since there obviously is a different pressure variation on the concave and convex faces of the airfoil and there is a pressure gradient chordwise across the outer end of a turbine blade, said pressures changing with changes in the operating conditions of the turbine. In addition, with air discharging from the outer end of a blade the air flow distribution in the blade will be affected by the small clearance between the blade and the adjacent stator wall which clearance is difficult to control accurately.

Because of the restricted openings 46, the cooling air discharges at relatively high velocity from the trailing edge of the blade. The trailing edge of a turbine blade normally runs hot. The high velocity flow'of the cooling air through the restricted openings in-provides for high heat transfer from the adjacent Portions of the blade thereby effectively cooling'the blade trailing edge.

The leading edge of a turbine blade is the other region of such a blade which normally runs hot and therefore like the trailing edge requires more effective cooling than the portions of the blade between its said leading and trailing edges. In order to efiectively cool the leading edge of the blade 12 the restricted openings 46 along the trailing edge are designed to provide for a relatively large amount of air flow through the passage 40 disposed along said leading edge. For this purpose, the length of the discharge opening 46, as measured along the blade trailing edge 42, for the leading edge passage 40 is relatively long compared to the discharge openings 46 for the other passages 49 whereby the area of the restricted opening 46 for said leading edge passage 4% is relatively large.

The temperature distribution pattern of the turbine motive fluid usually is such that the highest temperatures occur midway along the blade. To increase the cooling midway along the leading edge 44 of the blade 12 the passage as along said leading edge converges slightly in this region as indicated at 52 thereby increasing the velocity of the cooling air flow and hence the cooling in this region.

in order to fabricate a blade 12, it is made in two halves 12a and 1212 as previously mentioned and as best seen in FIGS. 11 and 12. The blade half 12a includes the convex face 34 with part of the leading and trailing edges of the blade working or airfoil portion and the major portion 22a of the blade root. In addition rib portions or

halves

38a, 48a and 50a of the

Webs

38, 48 and 50' respectively are formed integral with the blade half 1212. Likewise the blade half 1211 includes the con cave face 36 with remaining part of the leading and trailing edges of the blade working portion and the remaining portion 22b of the blade root. Also the other rib portions or

halves

38b, 48b and 50b of the

Webs

38, 43 and 50, respectively, are formed integral with their blade half 12b. The rib halves 33a and 38b as well as the other of said rib halves all abut each other so that the portion of the junction I between the leading and trailing edges of the blades is defined by the abutting surfaces of said ribs.

Each

blade half

12a and 12b preferably is a precision casting and the surfaces of each blade half to be joined to the complementary or mating surfaces of the other blade half are machined to provide an accurate fit with the other blade half. The shape and position of the mating surface junction J of the two halves is shown in FIGS. 310 and is so chosen that mating surfaces can be machined by a straight line pass of the cutter without any relative twisting of the blade or cutter. In other words the mating surface junction J of each

blade half

12a and 12b is a cylindrical surface, although as illustrated, not necessarily a circular cylindrical surface, in that it can be defined by a straight line moving parallel to itself. In the blade illustrated the generating line of said cylindrical mating surface I is inclined to the longitudinal axis of the blade. The two blade halves are then brazed together at their mating surfaces. Following the brazing operation the fir treeribs 24 and the shelf portions of the blade root are accurately machined. The trailing edge portions of the two blade halves are formed so as to pro vide the trailing edge slots 46 when the two halves are brazed together.

It is known that the heat transfer efficiency of a plurality of short webs is substantially better than that of a single long web having the same length as the combined length of the short webs. The heat transfer efiiciency increases as the length of the webs along the flow path is decreased so that a short web having the shape of a pintype projection has even superior heat transfer properties. Accordingly it is within the scope of the invention to add and/or substitute a plurality of short webs and/or pin-type projections within the airfoil portion of the hollow blade. Such a modification, illustrated in FIGS. 13 and 14, although superior from the standpoint of the cooling effectiveness of the air flowing through the blade is more complex from a fabrication standpoint. For ease of understanding the parts of FIGS. 13 and 14 corresponding to parts of FIGS. 1 12, have been designated by the same but primed reference numerals. 7

Referring to FIGS. 13 and 14 at least one of the lengthwise extending webs has been eliminated to widen the leading edge passage 40 and a plurality of pin-type projections of circular cross-section are spaced along the leading edge portion of this passage and along a portion of the adjacent passage in order to increase the cooling effectiveness of the cooling airflowing through said passages. Each of the projections 60 comprises two

parts

60a and 60b. The

parts

60a and 60b of each projection 60 are formed integral with the convex and concave blade faces 34' and 36' respectively with each part extending part way across its hollow blade passage into abutting engagement with the other part of its projection 60.

A plurality of relatively short webs 62 are spaced along the chordwise portions of the various blade passages 40' in the region of the trailing half of the blade to increase the cooling effectiveness of the air in this portion of the blade. For this purpose certain of the chordwise webs 50 have been replaced by a plurality of 'short chordwise extending webs 62 and other webs 62 have been added. Short webs 62 are used along the trailing half of the blade instead of the pin-type projections because this half of the blade is relatively thin. Thus if pins 60 were used in this thin portion of the blade then because of the large fillets desired at the junction of each pin with its blade face the average width of each pin would be much greater in this thin portion of the blade.

Each of the webs 62 comprises two

short ribs

62a and 62b. The

ribs

62a and 62b are formed integral with the convex and concave blade faces 34' and 36' respectively with each rib extending part way across its hollow blade passage into abutting engagement with the other rib of its web 62.

The two

parts

60a and 60b of each pin type projection 60 and the two

parts

62a and 62b of each short web 62, like the halves of the various ribs between the blade faces, all abut each other along the aforementioned junction J.

While we have described our invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding our invention, that various changes and modifications may be made therein without departing from theh spirit or scope thereof. We aim in the appended claims to cover all such modifications.

We claim as our invention:

1. A rotor blade for turbines, compressors or the like; said blade having a hollow airfoil portion and a root portion, said root portion having a cavity therein and an opening for the supply of a heat exchange fluid to said cavity for flow therefrom through said blade airfoil portion, said airfoil portion having opposed faces extending lengthwise of the blade and leading and trailing edges also extending lengthwise of the blade and joining said faces, said blade airfoil portion also having a plurality of spaced partitions dividing the hollow interior of said airfoil portion into a plurality of passages communicating at one end with said root portion cavity such that all of said heat exchange fluid flowing through said airfoil portion flows through said passages, said passages being spaced chordwise across the blade airfoil portion adjacent to the root portion of the blade and all of said passages extending lengthwise of the blade from the blade root portion but for varying distances and then turning toward and terminating in individual discharge openings spaced along the trailing edge of the blade airfoil portion, the passage adjacent to the leading edge of the blade airfoil portion extending lengthwise substantially the entire length of the blade airfoil portion and the lengthwise extent of the other of said passages progressively decreasing chordwise across the blade airfoil portion so that the passage adjacent to the blade trailing edge has its discharge opening disposed adjacent to the blade root portion and so that the discharge openings of said passages are disposed along substantially the entire length of said trailing edge, each of said passages having a restriction at its discharge opening and said leading edge passage having a reduced area region in its leading edge portion and disposed approximately midway along the blade leading edge.

2. A rotor blade for turbines, compressors or the like; said blade having a hollow airfoil portion and a root portion, said root portion having a cavity therein and an opening for the supply of a heat exchange fluid to said cavity for flow therefrom through said blade airfoil portion, said airfoil portion having opposed faces extending lengthwise of the blade and leading and trailing edges also extending lengthwise of the blade and joining said faces, said blade airfoil portion also having a plurality of spaced partitions dividing the hollow interior of said airfoil portion into a plurality of passages communicating at one end with said root portion cavity such that all of said heat exchange fluid flowing through said airfoil portion flows through said passages, said passages being spaced chordwise across the blade airfoil portion adjacent to the root portion of the blade and all of said passages extending lengthwise of the blade from the blade root portion but for varying distances and then turning toward and terminating in individual discharge openings spaced along the trailing edge of the blade airfoil portion, the passage adjacent to the leading edge of the blade airfoil portion extending lengthwise substantially the en tire length of the blade airfoil portion and the lengthwise extent of the other of said passages progressively decreasing chordwise across the blade airfoil portion so that the passage adjacent to the blade trailing edge has its discharge opening disposed adjacent to the blade root portion and so that the discharge openings of said passages are disposed along substantially the entire length of said trailing edge, said blade having a narrow slot formed along the blade trailing edge and the blade partitions, separating the blade passages, terminating at said slot so that each portion of said slot between a pair of adjacent partitions forms the restricted discharge opening for the passage formed by said pair of partitions.

3. A rotor blade for turbines, compressors or the like; said blade having a hollow airfoil portion and a root portion, said root portion having a cavity therein and an opening for the supply of a heat exchange fluid to said cavity for flow therefrom through said blade airfoil'portion, said airfoil portion having opposed faces extending lengthwise of the blade and leading and trailing edges also extending lengthwise of the blade and joining said faces, said blade airfoil portion also having a plurality of spaced partitions dividing the hollow interior of said airfoil portion into a plurality of passages communicating at one end with said root portion cavity such that all of said heat exchange fluid flowing through said airfoil portion flows through said passages, said passages being spaced chordwise across the blade airfoil portion adjacent to the root portion of the blade and all of said passages extending lengthwise of the blade from the blade root portion but for varying distances and then turning toward and terminating in individual discharge openings spaced along the trailing edge of the blade airfoil portion, the passage adjacent to the leading edge of the blade airfoil portion extending lengthwise substantially the entire length of the blade airfoil portion and the lengthwise extent of the other of said passages progressively decreasing chordwise across the blade airfoil portion so that the passage adjacent to the blade trailing edge has its discharge opening disposed adjacent to the blade root portion and so that the discharge openings of said passages are disposed along substantially the entire length of said trailing edge, the leading edge portion of the blade leading edge passage having a plurality of cylindrical projections spaced along and extending across said leading edge passage portion and the trailing edge portions of at least some of the blade passages having a plurality of short webs spaced along and extending across said trailing edge passage portions with the sides of each web being disposed substantially parallel to the sides of its passage, each of said cylindrical projections and webs being formed integral with at least one of the faces of the blade airfoil portion.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Kane Apr. 24, 1951 Williams June 9, 1953 Cangerni July 7, 1953 Tn'ebbnigg Aug. 4, 1953 Kempe June 1, 1954 Smith Aug. 24, 1954 Daugherty Jan. 18, 1955 Williams Jan. 25, 1955 8 Roush Sept. 24, 1957 H011 Dec. 30, 1958 FOREIGN PATENTS Switzerland May 1, 1942 Switzerland July 16, 1943 Switzerland Sept. 1, 1953 Great Britain Aug. 2, 1950 Great Britain May 11, 1955 Great Britain Dec. 7, 1955 Great Britain Aug. 8, 1956 Germany Dec. 4, 1952