US3026087A

US3026087A - Stator ring assembly

Info

Publication number: US3026087A
Application number: US677933A
Authority: US
Inventors: Harvey W Welsh
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1957-08-13
Filing date: 1957-08-13
Publication date: 1962-03-20
Anticipated expiration: 1979-03-20
Also published as: GB840873A

Description

March 20, 1962 H. w. WELSH 3,026,087

STATOR RING ASSEMBLY F'iled Aug. 13, 1957 5 Sheets-Sheet 1 INVENTOR.

A TTORNE Y.

March 20, 1962 H. w. WELSH 3,026,087

STATOR RING ASSEMBLY Filed Aug. 13, 1957 3 Sheets-Sheet 2 ATTORNE).

March 20, 1962 H. w. WELSH 3,026,087

STATOR RING ASSEMBLY Filed Aug. 13, 1957 3 Sheets-Sheet 3 IN VEN TOR.

Z! a I ar digs ZZZ 2 4 2321 /Z A TZ'ORNEY- llnited States Patent 91 3,026,087 STATOR RING ASSEMBLY Harvey W. Welsh, Indianapolis, Ind., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Aug. 13, 1957, Ser. No. 677,933 Claims. (Cl. 253-78) My invention relates to stator vane ring assemblies for axial-flow turbomachines and, more generally, to such axial-flow machines. It is particularly adapted to the requirements of axial-flow compressors such as are employed in aircraft gas turbines, but is not limited thereto.

By way of explanation and background, it is well known that most axial-flow compressors and turbines have alternating annular rows of fixed and moving blades. A ring of fixed blades may be referred to as a stator ring. In most cases, the stator ring comprises an outer shroud, an inner shroud, and vanes extending radially between and fixed to the shrouds. The outer shroud is fixed to the compressor case and the inner shroud ordinarily provides or supports a labyrinth seal acting against the rotor. In order to assemble the compressor, that is, to mount the rotor in the stator structure, the compressor case ordinarily is split along a plane containing the axis of the compressor into two segments, or halves, which are fixed together at what is called the split line on each side of the case. The stator vane rings likewise are made in 180 degree sectors, or halves. The stator vane ring halves are fixed to the halves of the compressor case. After the rotor has been mounted in one half of the case, the other half is placed over the rotor and the two halves of the case are bolted together or otherwise joined at the split lines.

- One purpose of the inner shroud is to increase the strength and stifiness of the stator vane structure. However, the usual practice of dividing the inner shroud into two sections greatly reduces the strength of the inner shroud and the restraint it places on the deflection of the vanes. It also increases local stresses in the shroud and vanes. Since the vane ring is deflected axially of the compressor by the load put on the vanes by air flow, a rigid structure which minimizes this deflection is highly desirable because it makes it possible to reduce stage clearances in the compressor and reduce distortion of the seal between the inner shroud and the rotor.

My invention substantially eliminates the defects of the previous split vane ring assemblies by providing a strong mechanical attachment between the adjoining ends of the sections of the inner shroud so that the inner shroud becomes a mechanical equivalent of a continuous ring. This is effected by a coupling device which may be readily applied to fasten the two halves of the inner shroud together. Preferably, although not necessarily, the attachment is such as to put the inner shroud rings in tension. Thus, if a small clearance is provided between the shroud sections and the coupling pulls these together, the inner shroud and the vanes will be put in tension by the coupling and the outer shroud will receive a com pressive load.

By this means, a vane assembly is provided which may be taken apart for assembly and disassembly of the compressor but which has mechanical strength substantially equivalent to a continuous 360 degree vane assembly. The rigidity of the structure is high, and distortions with the undesirable efiects referred to above are minimized.

A further advantage of a structure according to the invention and a further feature of the invention is that the rigid fixing together of the halves of the vane ring assembly makes it unnecessary to provide a rigid attachment between the outer shroud and the case.

ice

In the succeeding description of the preferred embodiments of the invention, a structure is shown in which the case and vane rings are in two sections. Three or more sections could be provided if desired, but two secticns are sufiicient to provide for assembly of the compressor. For conciseness, the term shroud or ring will be applied to the arcuate sections thereof as well as to the assembled 360 degree shroud or ring.

The nature of the invention and the advantages thereof will be more clearly apparent from the succeeding detailed description of the preferred embodiments of the invention and the accompanying drawings thereof.

FIGURE 1 is a fragmentary sectional view of an axialfiow compressor taken on a plane containing the axis of the compressor.

FIGURE 2 is a partial transverse sectional view of the stator taken on the plane indicated by the line 22 in FIGURE 1.

FIGURE 3 is a fragmentary view of a first form of shroud coupling taken on the plane indicated by the line 33 in FIGURE 2, with parts cut away.

FIGURE 4 is a sectional view taken on the plane indicated by the line 44 in FIGURE 3.

FIGURE 5 is a sectional view taken on the plane indicated by the line 5-5 in FIGURE 3.

FIGURE 6 is a view similar to the view of FIGURE 3 showing a second form of shroud coupling.

FIGURE 7 is a sectional view taken on the plane indicated by the line 77 in FIGURE 6.

FIGURE 8 is a sectional view taken on the plane indicated by the line 88 in FIGURE 6.

FIGURE 9 is a view similar to that of FIGURE 3 showing a third form of shroud coupling.

FIGURE 10 is a sectional View taken on the plane indicated by the line 10-40 in FIGURE 9.

FIGURE 11 is a view similar to that of FIGURE 3 of a fourth form of shroud coupling.

' FIGURE 12 is a sectional view taken on the plane indicated by the line 1212 in FIGURE 11.

FIGURE 13 is a sectional view taken on the plane in dicated by the line 13-13 in FIGURE ll.

Referring first to FIGURES 1 and 2, which illustrate the general arrangement of the compressor stator, the invention is illustrated as embodied in a compressor having a case fabricated from light metal sections. The case 15 includes a cylindrical outer shell 16 welded to a bolting flange 17 at one end and having a suitable flange or the like (not shown) at the other end. The cylindrical casing 16 is defined by two semi-cylindrical segments or sections 13 having longitudinal bolting flanges 19 which may be fixed together by bolts 21 or any other suitable attachment. The bolting flange 17 is fixed by bolts 22 to a further casing section 23 of the engine. Generally L-shaped rings or stiffeners 24 are welded or brazed to the inner surface of the case sections 18 to reinforce the case and locate the stator ring assemblies. Rings 26, extending axially from the inner edges of rings 24 and bands 27 brazed to the inner surface of the rings act to provide a labyrinth seal against the rotor blade shrouds. The successive stages of rotor blades 28 are mounted on a rotor structure (not shown) and extend in proximity to the case. The rotor blades are provided with shrouds 29 which include circumferential flanges 3i) cooperating with the seal bands 27.

Each stator vane ring comprises an outer shroud 32 made up of a flat ring 33 and a hat-section ring 34 welded or brazed together. The stator vanes 36 are fixed to the outer shroud and include tangs 37 extending through the web of ring 34. The flanges 38 at each edge of the outer shroud bear against the seal rings 26 and the'side walls of the hat-section ring 34 bear against circumferen- 3 tial ribs 39 on the rings 24 which locate the vane axially of the compressor.

To restrain the vane ring assemblies against rotation about the axis of the compressor, small keys or blocks 41 are brazed to the radial surfaces of the hat-section rings 34. These blocks engage in notches 42 cut in the ribs 39 of the rings 24. Two such locating means are provided substantially half-way between the split lines, one on each half of the outer shroud.

The inner ends of vanes 28 are rigidly fixedto the inner shroud ring 43, which is in two semi-circular sections. Suitable coupling means, indicated generally at 45 in FIGURE 2, are provided between the two sections of the inner shroud. The preferred structuresof these coupling means and typical inner shroud structures are shown in FIGURES 3 to. 13.

Referring now to FIGURES 3 to 5, the inner shroud 43 comprises an outer frusto conical band 46 and an inner hat-section ring 47, these being spotwelded together at their abutting margins. The vanes 28 are suitably attached as, for example, by brazing to the inner shroud 43. The coupling 45 between the sections of the inner shroud is provided by structure including cross mem ring here 48 spotwelded to the inside of the radial walls of the ring 47. A single tongue 49 which, as will be seen most clearly in FIGURE 5, is a sheet metal member folded into an I-section, is spotwelded to one of the cross members 48. Two tongues 51 of similar structure to tongue 49 are spotwelded to the other cross member 48 and extend so as to lie on either side of the tongue 49. These tongues define inclined wedging or ramp surfaces 52 which face toward the shroud section on which the tongue is mounted and which face each other when the intermediate tongue 49 is inserted between theouter tongues 51 in the assembly of the vane ring. As will be noted, the ramp surfaces are skewed to the axis of the compressor so that the coupling fits readily between the vanes '28. This skewing need be provided only where the limited space between the vanes makes it desirable.

The two halves of the inner shroud are fixed together by two wedging members 53 and 54 which are of sheet metal formed into a trapezoidal cross section to provide wedging surfaces 56 to cooperate with the ramp surfaces 52'of the tongues. The wedge members 53 and 54 are pulled together by a socket head screw 57, the head of which bears against the inner web of the wedge 53 and which cooperates with a self-locking nut 58 spotwelded to the inner web of wedge 54. As will be apparent, upon tightening the bolt into the nut, the Wedges are pulled together and force the ramp surfaces. 52 apart, pulling the shrouds together. When the stator ring is fully assembled, the ends of the shroud sections, which are shown spaced by a gap 59, are pulled into abutting relation. A very strong and rigid attachment between the stator rings is thus provided and the inner shroud is put in tension.

, As will be apparent, both of the couplings 45 at the two 'SPllt lines may be identical. The bolt 57 may be reached by a suitable tool to tighten or release the coupling through the clearances between the stages or through a hole (not shown) in theouter shroud before the top half of the case is assembled onto the lower half. The bolt 57 extends through a hole 61 in the tongue 49 which has suificient clearance circumferentially of the shroud to allow movement of the tongue relative to the bolt.

The second form of coupling, illustrated in FIGURES 6 to 8, employs the same principle of wedging action to pull the shroud sections together as that previously described, but isstructurally different. The inner shroud may be substantially the same as that previously described, made up of an outer band 46 and an inner hatsection ring 47. A projecting channel section tongue 63 is welded to the bottom and side flanges of one hata section 47 and a similar tongue 64 is similarly fixed to the other hat-section 47. Tongue 64 has a radial ofiset this tongue is narrower than tongue 63 so that tongue 64'may enter into tongue 63 with'the shroud sections in proper alignment. Tapered slots 68 and 69 are machined in the side webs of tongues 63 and 64, respectively. A wedge or tapered block 71 is pulled radially into the slots 68 and 69 by socket head bolt 72 which threads into a self-locking nut 73 spotwelded to the tongue 63. A paral lelogram-shaped plate 74 fixed to the wedge 71 substantially closes the gap between the shroud bands 46. The bolt 72 passes through suitable clearance openings 76 and 77 in the tongues 63 and 64. When the shroud ends have been brought into proper relation with the tongues overlapping, the wedge 71 may be placed in the slots 68 and 69 and the bolt 72 is inserted and tightened. The wedge 71, acting on the ramp. surfaces of the slots, pulls the parts of the stator ring together and puts them in tension. The wedge 71 is pulled in until it engages both sides of the slots' 68 and 69, firmly locking the sections. The figure shows the partsas they appear before the coupling has been tightened fully.

FIGURES 9 and 10 illustrate a third form of coupling similar in many respects to that of FIGURES 3 to 5. The overlapping tongue members are an inner tongue 78 fixed to one shroud and outer tongues 79 fixed to the other shroud. As in FIGURE-'3, these-tongues are generally of I-section and aregfixed to cross members 48. However, the tongues 78 and 79 are small machined metal blocks rather than folded sheet metal. They have slots 80 which provide ramp surfaces 86 similar to those previously described-with respect to FIGURE 3, except that there are ramp surfaces at each side of the slot, and are pulled together by two wedges 81 and 82 which are similar in exterior contour to those-previously described. but which are solid metal. A parallelogram-shaped metal sheet 83, fixed to the outer surface of wedge '81 and extending the full width of band 46, substantially fills the gap between the ends of the adjoining'bands 46. A socket head bolt 84 mounted in the wedge 81 threads into wedge 82, pulling the wedges against the ramp sur faces 86 of the tongues to draw the shroud sections to gether. A self-locking nut is not employed in this form. Instead, tabs 87 extending from-the sheet 83 may be bent down into slots. 88. These tabs prevent the bolts from loosening because of vibration of the structure. The bolt 84 is tightened until the wedges engage both sides of slots 80, bearing against all the ramp surfaces, or until the ends of the shroud parts: 46 and 47 engage the wedges. The structuremay be proportioned for-either result.

The fourth embodiment of the invention, shown in FIG- URES 11 to 13, is more closely related to the form of FIGURE 6 than to the others previously described. In this form, the inner shroud 43 may be similar to those previously described, but the ends of the sections of the shroud are joined on a plane 91 containing the axis of the compressor. Two tongues 92 on one of the shrouds are defined by strap members spotwelded to the radial walls of the hat-section 47. The tongues 92 have tapered or V-shaped slots 93 cut into-them. A channel section tongue 94, the web of which lies adjacent the band 46, is spotwelded to the other shroud section. The projecting end of tongue 94 is reduced in width so as. to fit closelyv between the tongues 92. Slots 96 are cutin the tongue 94 which are of the same proportionsasthe slots 93. A countersunk bushing 97 is welded to the inner surface of the shroud ring 46 on which the tongues 92 are mounted. A slot 98 in the web of tongue 94 provides clearance for this bushing. The wedge 99 which draws the shroud sections together is a rectangular block with chamfered ends, asindicated at 101-. A machine screwltlZ received in the bushing 97 and threaded into the wedge 99 pulls the wedge radially outward, the chamfered surfaces engaging the ramp surfaces of the slots 93 and 96 to pull the endsof the shrouds into firm abutment at the plane 91.

:It will be apparent that the several forms of the invention disclosed have a common principle of action, although the structures are diversified. Depending upon the dimensions of the shroud and the vane ring structure and other considerations, one or another might be most suitable in a particular installation. All provide a strong, rigid connection between the sections of the shroud ring and all are easily applied and released.

In the assembly of the compressor incorporating the invention, the lower vane ring sections may be inserted into the lower half of the case. The rotor is then mounted on the lower half of the case and the upper halves of the vane rings are fixed to the lower halves. The upper half of the case is then mounted over the vane ring assemblies and rotor and bolted to the lower half.

While structure to bolt each outer shroud section of the vane ring to the corresponding section of the case may be provided, as is conventional, such bolting may be accomplished after the case has been assembled. However, since the invention provides essentially a rigid 360 degree vane ring assembly, such bolting may be dispensed with. When the vane rings are lowered into the lower half of the case or the upper of the case is lowered onto the vane rings, the keys 41 are engaged in the slots 42 in the case, thus holding the vane rings against rotation.

The detailed description of the preferred embodiments of the invention is not to be construed as restricting the invention, as many modifications of structure may be made by exercise of skill in the art within the scope of the invention.

I claim:

1. An axial-flow turbomachine comprising, in combination, a case including at least two segments joined along longitudinal split lines, a stator vane ring mounted in the case comprising at least two arcuate sectors, each vane ring sector comprising an outer shroud, an inner shroud, and vanes connected to the shrouds, and means for rigidly coupling the adjacent ends of the inner shrouds including structures on each inner shroud at the ends thereof and means attached to said structures locking said structures together.

2. An axial-flow turbomachine comprising, in combination, a case including at least two segments joined along longitudinal split lines, a stator vane ring mounted in the case comprising at least two arcuate sectors, each vane ring sector comprising an outer shroud, an inner shroud, and vanes connected to the shrouds, and means for coupling the adjacent ends of the inner shrouds including structures on each inner shroud at the ends thereof and removable connecting means engaging said structures and exerting a force circumferentially of the shrouds pulling the segments mutually together.

3. An axial-flow turbomachine comprising, in combination, a case including at least two segments joined along longitudinal split lines, a stator vane ring mounted in the case comprising at least two arcuate sectors, each vane ring sector comprising an outer shroud, an inner shroud, and vanes connected to the shrouds, and means for rigidly coupling the adjacent ends of the inner shrouds including structures fixed on each inner shroud at the ends thereof providing ramp surfaces thereon, a wedging mem ber movable transversely to the inner shrouds into engagement with the ramp surfaces of both shrouds, and means connected to the wedging member and one of the shrouds for forcing the wedging member into engagement with the ramp surfaces.

4. An axial-flow turbomachine comprising, in combination, a case including at least two segments joined along longitudinal split lines, a stator vane ring mounted in the case comprising at least two arcuate sectors, each vane ring sector comprising an outer shroud, an inner shroud, and vanes connected to the shrouds, and means for rigidly coupling the adjacent ends of the inner shrouds including structures fixed on each inner shroud at the ends thereof each having opposed notches therein providing ramp sur faces thereon, two opposed wedging members movable radially into respective notches into engagement with the ramp surface of both shrouds, and means connected to the wedging members operable to draw the wedging members together.

5. An axial-flow turbomachine comprising, in combination, a case including at least two segments joined along longitudinal split lines, a stator vane ring mounted in the case comprising at least two arcuate sectors, each vane ring sector comprising an outer shroud, an inner shroud, and vanes connected to the shrouds, means for rigidly detachably coupling the adjacent ends of the inner shrouds, and radially slidable interengaging means on the vane ring and the case restraining the vane ring against rotation about its axis.

6. A vane ring structure for an axial-flow turbomachine comprising, in combination, at least two arcuate sectors, each sector comprising an outer shroud, an inner shroud, and vanes connected to the shrouds, and detachable coupling means directly connected to the inner shrouds at the ends thereof rigidly detachably coupling adjacent inner shrouds together.

7. A vane ring structure for an axial-flow turbomachine comprising, in combination, at least two arcuate sectors, each sector comprising an outer shroud, an inner shroud, and vanes connected to the shrouds, and coupling means on the inner shrouds at the ends thereof rigidly coupling adjacent inner shrouds together comprising parts fixed on each shroud and means dctachably connecting the said parts adapted to draw the shrouds together circumferentially.

8. A vane ring structure for an axial-flow turbomachine comprising, in combination, at least two arcuate sectors, each sector comprising an outer shroud, an inner shroud, and vanes connected to the shrouds, and coupling means fixed on the inner shrouds at the ends thereof for rigidly coupling adjacent inner shrouds together comprising tongues projecting from one shroud, a tongue projecting from the other shroud adapted to extend between the firstmentioned tongues, the tongues having spaced ramp surfaces thereon facing the shrouds from which they project, a member extending transversely of the shrouds engaging between and against the ramp surfaces, and means coupling the member to one of the shrouds adapted to force the member transversely of the shroud into the space between the ramp surfaces to draw the shrouds together.

9. A vane ring structure for an axial-flow turbomachine comprising, in combination, at least two arcuate sectors, each sector comprising an outer shroud, an inner shroud, and vanes connected to the shrouds, and coupling means fixed on the inner shrouds at the ends thereof for rigidly coupling adjacent inner shrouds together comprising tongues projecting from one shroud, a tongue projecting from the other shroud adapted to extend between the firstmentioned tongues, the tongues having notches in opposite faces thereof providing ramp surfaces thereon facing the shrouds from which they project, two members extending transversely of the shrouds seated in the respective notches between and against the ramp surfaces, and means coupling the members together operable to draw the said members toward each other into the notches.

10. A vane ring structure for an axial-flow turbomachine comprising, in combination, at least two arcuate sectors, each sector comprising an outer shroud, an inner shroud, and vanes connected to the shrouds, and coupling means fixed on the inner shrouds, at the ends thereof for rigidly coupling adjacent inner shrouds together comprising tongues projecting from one shroud, a tongue projecting from the other shroud adapted to extend between the firstmentioned tongues, the tongues having spaced ramp surfaces thereon facing the shrouds from which they project, a member extending transversely of the shrouds engaging between and against the ramp surfaces, and

7 means coupling the member to one of the shrouds adapted to force the member transversely of the shroud into the space between the ramp surfaces to draw the shrouds together, the member including a plate extending across and substantially filling said space between the inner 5 shrouds.

Goeller June 25, 1940 8 Chester et al. Mar. 20, 1945 Summers May 25, 1948 Howard Sept. 16, 1952 Clausen' Oct. 12, 1954 Boyd Nov. 9, 1954 Russell et a1. Aug. 6, 1957 FOREIGN PATENTS Canada Ian. 8, 1957