Stator construction

April 12, 1960

L. C. SMALL, JR., ETAL

STATOR CONSTRUCTION

2,932,485

Filed Oct. 1, 1954

Sheets-Sheet 1

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April 12, 1960

2,932,485

L. C. SMALL, JR., ET AL

STATOR CONSTRUCTION

Filed Oct. 1, 1954

Sheets-Sheet 2

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BY &amp; (£&amp;++&amp;«

ATTORNEY

United States Patent Office _{B J} 2,932,485

Patented Apr. 12, I960

2,932,485

STATOR CONSTRUCTION

Leslie C. Small, Jr., South Glastonbury, and Lawrence A. Haines, Hartford, Conn., assignors to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware

Application October 1,1954, Serial No. 459,639

Claims. (Cl. 253—78)

This invention relates to nozzle vanes for a turbine and particularly to the mounting of the vanes in a supporting structure.

The nozzles have been supported in inner and outer shroud rings which have openings to receive the vanes and which carry both the axial thrust on the vanes due to the pressure drop through the nozzle and also the circumferential thrust from the torque applied to the vanes. The loading of the shroud rings has been found to be so high, especially at the operating temperatures of the nozzles vanes and shroud rings, that the shrouds have been subject to severe cracking, frequently to such an extent as to cause failure. A feature of the invention is an arrangement by which to relieve the shroud rings of a substantial part of the load acting on these rings.

Another feature is the transfer of the thrust loading on the vanes directly from the vanes to a support structure without transmitting this thrust through the shrouds. One feature of the invention is an arrangement by which to permit expansion and contraction of the shroud without affecting the nozzle vanes and without interfering with the device by which the thrust loading on the vanes is absorbed.

Other objects and advantages will be apparent from the specification and claims, and from the accompanying drawings which illustrate an embodiment of the invention.

Fig. 1 is a longitudinal sectional view through a turbine.

Fig. 2 is a fragmentary sectional view substantially on the line 2—2 of Fig. 1.

Fig. 3 is a longitudinal sectional view through a part of a turbine engine.

The invention is shown in conjunction with a turbine having nozzle vanes 2 directly upstream of a row of turbine blades 4 carried by a rotor 6. The rotor is supported centrally of a casing 8 by suitable bearings supported from the casing, as shown, for example, in the Willgops Patent 2,639,579. The casing 8 is made up of support rings 10 and '12 attached together in axial align-: ment as by bolts 14 and these rings carry the outer ends of the Turbine vanes. The support ring 10 is shown as providing support for the outer ends of the row of vanes 2. The inner ends of the vanes 2 are supported by an inner ring 16.

The rings 10 and 16 are so mounted that they are held in concentric relation with respect to each other and are prevented from moving axially with respect to each other. This may be done, for example, by the attachmefit of the outer casing 8 to a surrounding supporting ring 18 which in turn is secured to the outer annular wall 20 of the combustion chamber of the engine. The wall 20 at its forward end is connected to the outer wall 22 of the diffuser section into which a compressor, not shown, discharges. The inner wall 24 of the diffuser is held in predetermined relation to the outer wall by radial struts 26.

The inner casing ring 16 is attached to a sleeve 28 forming the inner wall of the combustion chamber and extending forwardly for attachment to the inner wall 24 of the diffuser as by a ring 29. With this arrangement it will be clear that the rings 10 and 16 are supported so that they are held in predetermined radial and axial relation to each other and can have axial loads applied thereto without detrimentally affecting the arrangement of the 5 parts.

Associated with the outer casing ring 10 is a shroud ring 30 having openings 32 therein through which the outer ends of the vanes 2 extend. As shown each vane has an enlarged head 34 at the outer end which fits within the 10 opening 32 and the latter is made large enough so that the vane can move freely therein, permitting the vane to move radially with respect to the shroud ring.

Any axial pressure loads applied to the vane 2 are transmitted through projecting lugs 36 on each vane which 15 engage with an inwardly extending rib 38 on the casing ring 10. As shown, the radial dimensions of the rib and lugs are such that radial movement of the vane is not interfered with. That is to say, there is radial clearance provided between the casing rib and the vane and be20 tween the lug and the casing. The rib 38 may be continuous or may be interrupted to form a plurality of projecting lugs with which the vane lugs engage.

As shown, the cooperating surfaces on the rib 38 and lugs 36 are in a plane substantially at right angles to the 25 axis of the nozzle such that relative circumferential movement of any of the lugs with respect to rib 36 is permissible except as the circumferential movement of each vane is limited by the shroud ring. That is to say, the axial load only is transmitted directly from the vane through the 30 lugs 36 to the casing and the circumferential loading on the vane is through the shroud to the casing thereby relieving the shroud of any axial loads.

The shroud ring 30 has a number of radially extending projections 40 at its downstream edge which fit within 35 radially extending grooves 42 in a ring 44 attached to the casing 10 by the bolts above mentioned. With this arrangement the shroud ring is prevented from turning within the casing ring but is free to move radially so that thermal expansion of the shroud ring with respect to the 40 casing ring 10 is not restricted. It will be apparent ..that the essential contact between the shroud ring and the outer supporting structure is the interengagement of the projections 40 with the ring 44 and the radial overlapping of the ring.44 with the shroud, as shown at 45, Fig. 2, by which 45. ^{t0 limit} rearward axial movement of the shroud ring.

This overlap, which results from the tongues .43 defined between the grooves 42 extending radially inward beyond the outer surface 35 of the ring 30, is best shown in Fig. 2· The forward axial movement of the shroud ring 34 is 50 limited by engagement of the forward edge of the ring in a notch 47 in the casing ring 10. It will be apparent that the outer end of each vane 2 is free to move in a circumferential direction except as limited by slot 32 so that the torque loading on the vanes is transmitted directly 55 to the shroud ring. Nevertheless, a substantial part of the load, that is to say, the axial thrust loading on the vanes, is not imparted in any way to the shroud ring but is transferred directly from the vane to the casing ring. The upstream end of the shroud may be positioned in a notch _eo 45 in casing ring 10 but not in contact with the ring as shown.

A similar arrangement is utilized at the inner ends of the vane 2. In this arrangement the inner casing ring 16 carries, in spaced relation thereto, a shroud ring 46 55 having openings 48 to receive the enlarged inner ends 50 of the vanes 2. Because the thermal expansion problem is not as severe at the inner ends of the vanes the upstream end of the shroud ring 46 may be bolted , directly to the casing ring 16 without providing for relative therγθ mal expansion. As at the outer ends of the vanes, each vane has a projecting lug 52 which engages with a circumferential rib 54 on the casing ring 16 so that the

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axial thrust loading on each vane is transmitted directly to the ring 16 without being transferred through the shroud ring. It will be understood that the lugs 36 extend outwardly from the outer vane end whereas the lugs 52 extend inwardly from the inner vane end. Also as at the Outer ends of the vanes the torque loading on each vane is transmitted to the shroud ring since the circumferential movement of the vanes is limited only by the opening in the shroud ring through which the vanes extend.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.