US2681788A

US2681788A - Gas turbine vane structure

Info

Publication number: US2681788A
Application number: US227806A
Authority: US
Inventors: Leon R Wosika
Original assignee: Solar Aircraft Co
Current assignee: Solar Aircraft Co
Priority date: 1951-05-23
Filing date: 1951-05-23
Publication date: 1954-06-22
Anticipated expiration: 1971-06-22

Description

Tine 1954 L. R. WOSIKA 2,68%78 GAS TURBINE VANE STRUCTURE Filed May 25, 1951 INVENTOR LEON R. \NosmA ATTORNEYS Patented June 22, 1954 UNITED STATES PATENT OFFICE GAS TURBINE VANE STRUCTURE Leon 1%. Wosika, San Diego, (Jalifl, assignor to Solar Aircraft Company, San Diego, Calif., a corporation of California Application May 23, 1951, Serial No. 227,806

4 Claims. 1

This invention relates to the construction of turbine vanes generally and is particularly directed to the construction of turbine stator vanes for use in gas turbines where high temperatures and corrosive effects are encountered. This application is a continuation-in-part of copending application serial No. 61,329, filed November 22, 1948 now abandoned, by Leon R. Wosika and em titled Gas Turbine Vane structure.

Gas turbine stator vanes of the prior art are customarily welded at their inner and outer ends to relatively thick inner and outer ring members suitably apertured to receive the inner and outer ends of the vanes, a body of welding metal between the vane ends and the rings functioning to securely fasten the vanes to both ring structures. Such a vane structure is generally referred to as a bucket wheel. Such bucket wheels, due to the fact they are subjected to the extremely high temperatures of combustion gases immediately passing from the combustion chamhere, are subjected to extremely high thermal and. pressure forces with the result that critical localized stresses are produced, particularly in the outer ends of the vanes and the weld connections to the outer ring as well as in the outer ring itself. These bucket wheels are extremely rigid and as a result such stresses have a tendency to fracture the vanes and ring structures reducing the eflicient operation of the bucket wheel and oftentimes producing chips of metal which fall into the rotor structure and completely wreck a turbine unit.

It has heretofore been proposed to overcome these problems by providing a bucket wheel struc ture having relatively heavy inner and outer rings and vane receiving slots to slidably receive the ends of the stator vanes or at least having either the inner or outer ends in free sliding cooperation with the respective ring. Such constructions are dificult to handle as a unit in shipping and assembly and, under normal thermal and pressure forces and localized distortion resulting therefrom, one or more blade ends are likely to become disassociated from the receiving slot in the ring structures. As a result, the vanes are free to become misaligned with respect to their ring receiving slots and even broken off or chipped with the fragments ralling into the turbine rotor completely damaging the turbine unit.

It is, therefore, the primary object of the present invention to provide a bucket wheel of unitary structure capable of easy handling in shipping and assembly in which the danger of breakage is substantially avoided.

It is a further important object of the present invention to provide a bucket wheel in which the vanes are connected to the inner and outer rings in a novel manner to assure flexibility of the bucket wheel while eliminating the build up of objectionable localized stresses upon distortion thereof.

It is still another object of the present inven tion to provide a bucket wheel structure in which the inner and outer ring members are of a thickness of the order of sheet metal and securing the bucket wheel vanes to such rings in a manner to assure localized flexibility of the bucket wheel to accommodate high thermal pressure expansions without creation of critical localized stresses.

Another object of the present invention is to facilitate and reduce the cost of manufacture of turbine vane structures.

Still another object or" the invention is to provide a turbine vane structure in which the vanes are welded to a pair of supporting bands in such a way that high stress concentration at the points of joinder are eliminated.

Still another object of the invention is to provide a turbine vane structure consisting of inner and outer concentric bands having normally bendable characteristics with vanes extending therebetween and connected thereto in a manner to provide for differential expansion of the two bands and the vanes.

Further objects of the invention will become apparent from the description as it proceeds in connection with the appended claims and attached drawings wherein:

Figure 1 is a side elevational view with a portion of outer Wall broken away of a gas turbine employing vane structure made in accordance with the present invention;

Figure 2 is a transverse sectional view taken substantially on the plane of line 2-2 of Figure 1;

Figure 3 is a side elevational view of a bucket wheel structure made in accordance with the present invention;

Figure 4 is a sectional view taken substantially on the plane of line 4-4 of Figure 3;

Figure 5 is a fragmental perspective View of a portion of the bucket wheel structure of this invention;

Figure 6 is a fragmental sectional View illustrating the manner in which the bucket wheel structure of this invention is supported in the turbine housing; and

Figure '7 is fragmental sectional View taken through one of the bucket wheel vanes and illustrating the contour of the vane, the head structures provided at the opposite ends of the vanes, and the opening provided in the inner ring structure to receive the inner vane head.

Referring now to Figure 1 there is shown a typical gas turbine comprising an air compressor E6 of the axial flow type which receives air at its end as indicated by the arrow compresses it, and delivers it through a scroll E2 to combustion chamber I3 where it is burned with a suitable fuel. The products of combustion are delivered through a scroll I 4 to a gas turbine indicated generally at I5. The gas turbine contains as essential components a stationary bucket wheel. or

vane structure l6 which receives gas from the I scroll I4 and directs it at suitable angle against the vanes of a rotor IT. After leaving the rotor I? the hot gas passes through an exhaust duct, preferably in the form of a thrust nozzle it. The rotor I! may be mounted on a common shaft 59 with the rotor within the compressor it or in some other conventional arrangement since these features do not constitute a part of the present invention and are not disclosed in the drawings. The invention resides in the stationary bucket vheel or vane structure it which will now be described.

Bucket wheel It made in accordance with the present invention comprises a pair of inner and outer cylindrical bands or rims 2! and 22 of relatively thin metal concentrically disposed with respect to each other and supporting the inner and outer ends respectively of a plurality of stator vanes 23 having intermediate portions 2d and inner and outer head portions and 26. any suitable metal may be employed in the production of the cylindrical bands, the present invention contemplates a metal which, when formed in a thin ring, has a substantial amount of flexibility to permit localized distortion in a radialdirection while preventing circumferential and transverse shifting of the stator vanes. Actual experience indicates rings or bands made of stainless steel having a body thickness approximating that or" sheet metal are particularly suited for this purpose when associated with stator vanes formed and attached thereto in the manner to be presently described.

Such rings are provided with

vane receiving openings

21 and 28, respectively, circumferentially spaced around and radially aligned to freely receive the respective vane heads or ends 25 and The inner vane heads 25 are all secured by welding to the inner ring structure 2!! while only certain of the outer vane heads 2%; are secured to the outer ring structure 22. Such a structure provides a bucket wheel which is readily handled as a unit and is of light weight, simple construction and highly efiective. While the preferred embodiment disclosed in the drawings and described in this specification, contemplates the welding of all the inner vane ends to the inner ring structure and only certain of the outer vane ends to the outer ring structure, it is to be understood that substantially the same results can be obtained by welding all the outer vane ends to the outer ring structure and only certain of the inner vane ends to the inner ring structure.

Such thin rings have been found to be particularly adapted to punching operations to form the

vane receiving openings

21 and 28, which pursuant to this invention, correspond in crosssectional shape to that of the vanes 23 but are appreciably larger. The invention further contemplates making each vane 23 with an inter- While 5 correspond with rings 22.

mediate portion 24 of desired cross-sectional shape and size extending between the inner and outer bands and

head portions

25 and 26 of the same general shape but of larger size which extend through correspondingly shaped apertures 2'! and 28 provided in the inner and outer bands 2! and 22, respectively. The head portions of the vanes are of substantially greater radial thickness than rings 2| and 22 (Figures 4 and 6) and snugly fit the apertures in the bands so that the vanes are held against movement in all directions except a radial direction. To prevent undesired radial movement of the vanes relative to the rings, the heads at one end of the vanes, for example heads 25, are all welded to bands 2i and a portion only of the heads 26 are welded to the outer band 22. This permits relative radial distortion between the two bands at circumferentially spaced intervals in response to unequal thermal expansion of the parts.

Referring now to Figures 2 to '7, the inner band 2i is of cylindrical form while outer band 22 is transversely stepped (Figure 6) to provide a discharge end of greater area facing in a downstream direction. The plurality of vanes 23 ex tend substantially radially between the inner and outer bands and have the outer ends stepped to The inner band ZI is formed of a metal having a thickness of the order of .062 inch while the outer band is formed of a metal having a thickness of .094 inch. While these rings may be formed in any suitable manner, such as casting in the form of an integral annular band structure, they may also be formed of sheet metal pressed into the desired shape, punched to form

apertures

27 and 23, and bent into annular form and butt-welded along a transverse seam. The drawing illustrates the inner band ZI as a sheet metal band having a trans verse butt weld seam formed by abutting the opposing ends 2 la as illustrated in Figures 2 and 5.

Each vane 23 comprises an intermediate portion is of suitable cross-section, and inner and

outer head portions

25 and 26 respectively, of the same cross-sectional shape as the intermediate portion 24 but of larger dimensions. The intermediate portion 24 of each vane extends between the inner and outer bands ZI and 22 and the inner head portions 25 extend through the correspondingly shaped apertures Zlformed in the inner band 2I by punch operations. The outer heads 26 extend through correspondingly shaped apertures 23 formed in the outer band 22 also by suitable punch operations. It will, of course, be

. understood that the apertures in the inner and outer rings 2| and 22 are equal in number and properly spaced so that when the rings are concentrically disposed the inner and outer ring apertures will be properly aligned to assure proper radial disposition of the respective vanes 23.

The enlarged and thickened heads 25 and 2.5 are particularly desirable to assure a proper weld connection between the rings and vane ends and a long punch life, particularly at the punch end forming the trailing or downstream end of the

vane slots

21 and 28 since the larger dimen sions of the vane heads permit this end of the punch to be formed on a curve of a diameter of .148 inch rather than .03 inch which would be required if the vanes 23 were of uniform thickness from their inner to outer ends. This larger curvature of the

heads

25 and 26 also assures a sufficient mass of metal at the trailing edges of the vanes along the line of welding to better withstand the welding heat necessary to effect a good weld joint. This invention also contemplates having

heads

25 and 26 of the same crosssectional shape and size so that

apertures

21 and 28 can be punched with the same dies.

As shown in Figure 4, all of the inner heads 25 are welded at their inner edges to the inner ring 2|, and every third outer head 29 is welded along its outer edges to the outer band '22. The welds to the inner band 21 are indicated at 35 in Figures 4 and 5, and the welds to the outer band 22 are indicated at 3| in Figures 2 and 4. This permits a slight relative bowing between the inner band 2| and the outer band 22 at those circumferential points where the blades are not welded to the outer band. To accommodate this bowing the bucket wheel 16 as clearly seen.

in Figure 6 is supported by the thickened edges 32 of ring 22 in suitable grooves 32 of substantially greater radial dimensions provided in the turbine casing sections and AI. Casing sections 40 and ii also provide a well 42 surround ing the intermediate section of bucket wheel it into which the vane heads 26 extend. This well also permits the outward distortion of the bucket wheel.

It will be observed that because of the use of the

enlarged heads

25 and 26, all welding is removed from areas of high stress concentration immediately adjacent to the nozzle blades and the vane heads project slightly inwardly beyond the inner ring 2|, the supporting spider or web 43 being designed to freely receive these projecting ends.

In addition to the foregoing advantages, the use of the

enlarged heads

25 and 26 result in correspondingly larger apertures '21 and 28 which are more easily punched than smaller apertures would be.

The enlarged heads also provide greater strength for support of the outer ends of those vanes that are not welded to the outer ring 22 and assure that the limited localized distortions of the outer ring will not result in disassociation of the free vane ends from their receiving apertures.

The complete structure described with reference to Figures 3, 4 and 5 can be mounted in a turbine in various ways. As shown in Figures 1 and 2, the outer ring 22 is clamped between two casing sections 40 and 4! respectively of the gas turbine [5.

Certain changes in the flow characteristics of a vane assembly as described can be made while still employing the same vane elements 23 and the same punches for punching the aper tures 21 and 28, by simply punching the aper tures 21 and 28 at different angles. This permits a variation in the angles of inclination of the vanes 23 which is sufiicient to provide for oft needed slight adjustment from originally calculated design.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. A turbine vane structure and supporting casing assembly comprising a casing structure providing an inwardly facing annular Well; and a stator vane assembly supported for relative radial movement in said well in radially inwardly spaced relation to the bottom wall of said well and comprising concentric inner and outer bendable vanesupporting rims of diiierent diameters having apertures to receive in a close fit portions of suitable vanes, and circumierentially spaced vanes disposed between and having portions ex tending through said inner and outer rims respectively, all the vanes being secured to one cf said rims, only one of each adjacent series three vanes being secured to the other of said rims and the remainder of the vanes being slidably supported in the other of said rims thereby providing a unitary vane assembly having adjacent, circumferentially disposed, flexible sections adapted for independent relative radial movement in said well in response to varying thermal conditions.

2. The combination defined in claim 1. wherein all of said vanes are welded to said inner rim, and said outer rim and said remainder of the vanes, when subjected to temperature changes, are free to expand and move radially with respect to said inner ring, the other vanes, and said casing structure thereby avoiding undesired localized stresses within said vane assembly.

3. A turbine vane structure comprising a pair of vane-supporting rims of diiierent diameter and having a thickness of the order of sheet metal concentrically disposed one within the other in radially spaced relation and provided. with opposed circumferentially spaced through openings; circumferentially spaced vanes having intermediate piortions extending between said rims and rim-entering portions extending into and through said opposed through openings and having a sliding fit therein; and means securing only one of each adjacent series of three vanes to both of said rims and the remainder of said vanes being secured to the inner rim and slidably supported in the outer rim thereby providing a vane structure having adjacent independently distortable sections wherein said inner and outer rings are free for relative radial movement in response to thermal variations.

4. The combination defined in claim 3 wherein said outer rim is provided along each side edge with a protruding annular support flange adapted to mount said vane structure in a suitable turbine casing.

References Cited in the file of thi patent UNITED STATES PATENTS Number Name Date 2,110,679 Robinson Mar. 8, 1938 2,232,611 Keller Feb. 18, 1941 2,252,817 Van Rijswijk Aug. 19, 1941 2,402,418 Kroon June 18, 1946 2,447,942 Imbert et al Aug. 24, 1948 2,488,867 Judson Nov. 22, 1949 2,488,875 Morley Nov. 22, 1949 2,606,741 Howard Aug. '12, 1952 2,625,013 Howard et al Jan. 13, 1953 FOREIGN PATENTS Number Country Date 225,221 Switzerland Apr. 16, 1943 267,782 Switzerland July 1, 1950