US2836393A

US2836393A - Stator construction for axial-flow fluid machine

Info

Publication number: US2836393A
Application number: US598909A
Authority: US
Inventors: Payne Nigel Edward; Freeman Frederick
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1955-08-05
Filing date: 1956-07-19
Publication date: 1958-05-27
Anticipated expiration: 1975-05-27
Also published as: GB803137A; DE1038343B

Description

May 27, 1958 N. E. PAYNE ETAL 2,836,393

vS'I'ATOR CONSTRUCTION FOR AXIAL-FLOW FLUID MACHINE Filed July 19, 1956 2 Sheets-Sheet 1 Z2 Z1 Z g' 16 K 20 19 160/ 1% fifl 15 if Y 34 May 27, 1958 N. E. PAYNE ET AL 2,836,393

STATOR CONSTRUCTION FOR AXIAL-FLOW FLUID MACHINE Filed July 19, 1956 2 Sheets-Sheet 2 Fig.6..

Unite rates Patent STATOR CGNSTRUCTION FOR AXIAL-FLOW FLUID MACHINE Nigel Edward Payne, Burton-on-Trent, and Frederick Freeman, Derby, England, assignors to Rolls-Royce This invention relates to axial-flow fluid machines such as turbines or compressors of gas-turbine engines.

This invention has for an object to provide a construction of stator with hollow blades showing advantages in manufacture and operation.

According to the present invention, a stator of an axialflow fluid. machine comprises a ring of hollow stator blades secured at their inner and outer ends in hollow, box-like inner and outer blade platform structures, the passages through the blades opening into the interiors of the box-like platform structures, an outer casing structure wherein the blades are mounted through the outer platform structures, first duct connections connecting the interiors of the outer platform structures to externally of the outer casing structure, and second duct connections connecting the interiors of the inner platform structures to a chamber within internal stationary structure of the engine.

The construction of this invention enables low-pressure air to be passed through the blades, say for cooling, as compared with high-pressure air usually employed hitherto, the air flowing either from a low-pressure chamber internally of the engine to externally of the outer casing structure, or in the reverse direction; a more efiicient operation of the fluid machine is thus achieved.

The blades may have individual inner and outer platform structures, but preferably the blades are arranged in a plurality of sets, there being say three blades in a set, and the blades of a set have common inner and outer platform structures which act as manifolds for distributing air to and collecting air from the blades of the set. Such a blade and platform arrangement improves the loadbearing capacity of the structure, and at the same time reduces the number of duct connections and the number of ports necessary in the outer casing structure as compared with constructions in which each blade has individual platform structures.

In one preferred construction, the radially outer walls of the common outer platform structures and the outer casing structure have ports therein formed by hollow bosses, and tubular plugs engage by their ends in the bores to connect the interiors of the outer platform structures to externally of the outer casing structure, and the common inner platform structures have ports to their interiors formed by hollow radial bosses on their radially inner walls to engage plug-wise in radial sockets provided on a wall of the chamber and opening into the chamber. In this case, the socket-engaging bosses may also be employed to locate internal engine structure coaxially within the ring of stator blades.

There will now be described a gas turbine having nozzle guide vanes at the entry of the turbine constructed in accordance with this invention. The description refers to the accompanying drawings in which- Figure 1 is a part axial section through the turbine,

Figure 2 is a section on the line II-II of Figure 1,

Figure 3 is an axial section through a modified construction, and

Figure 4 is a section on the line IVIV of Figure 3.

Referring to the drawings, the turbine comprises a rotor having a shaft 10 which has secured to one end thereof a turbine disc 11 with a ring of rotor blades 12 mounted on its periphery. The turbine also comprises a stator having an outer load-bearing casing structure 13 from which is supported a ring of nozzle guide vanes 14 through the passages between which hot gas from cornbustion equipment 15 flows to be directed onto the rotor blades 12, and the nozzle guide vanes 14 in turn support a bearing 16 for the downstream end of the turbine shaft 10.

The nozzle guide vanes 14 which are hollow are arranged in sets of three (see Figure 2) and each set of three nozzle guide vanes 14 has associated with it a hollow, box-like inner platform structure and a hollow boxlike outer platform structure.

The outer platform structure of each set of vanes comprises a plate 17 having slots in which the outer ends of the vanes are secured as by welding or brazing and the plate 17 forms a portion of the wall of the working fiuid annulus of the turbine. The plate 17 is secured to flanges 18a around the edges of an outer wall part 18 so that the plate 17 is in spaced relation to the outer wall part 18 and so that a manifold space 19 is formed into which open the outer ends of the passages through the vanes 14. The outer wall part 18 of the outer platform. structure has formed integrally with it a hollow boss 20, the bore of which opens into the manifold space 19 and forms a socket to receive one end of a tubular plug 21, the opposite end of which is engaged in a socket formed by a hollow boss 22 provided on the outer casing structure 13 and forming a port opening through the outer casing structure to atmosphere. A cross pin 23 is fitted in the boss 22 to prevent the disengagement of the plug 21. The plug 21 has part-spherical end portions by which it engages the bores of the

hollow bosses

20 and 22.

The outer wall part 18 is also provided externally with outwardly-extending dogs 24 at axially-spaced points to co-operate with corresponding dogs 25 on the outer casing structure 13 so as to locate the outer platform structure circumferentially in the turbine. The outer wall part 18 also is provided with a thickened edge 26 at its downstream end, which edge is provided with an axially-facing groove to receive the upstream edge of a shroud ring 27 for the turbine rotor blades 12-. The shroud ring 27 is located both axially and circumferentially with respect to the outer casing structure 13. Since the gas loads on the vanes 14 tend to displace the vanes downstream, the shroud ring 27 also serves to locate the vanes axially.

The inner platform structure associated with a set of vanes comprises a plate 28 which has an inward flange at its upstream edge and also is formed with slots in which the inner ends of the vanes 14 are secured as by welding or brazing. The plate 28 forms a portion of the inner wall of the working fluid annulus of the turbine. The inner platform structure also comprises an inner Wall part 29 having flanges 29:: along its circumferentially spaced edges and its downstream edges and the plate 23 is secured to the flanges 29a, so that the plate 28 is spaced from the wall 29 and forms a manifold space 30 into which open the inner ends of the passages in the vanes 14.

Theinner wall part 2 9 has formed integrally with it a hollow boss 31 which forms the plug of a plug and socket duct connection between the manifold space 30 of the inner platform structure and an annular chamber 47 formed in a support for the bearing 16.

The bearing support comprises an upstream radiallyextending annular diaphragm 32, a downstream radiallyextending annular diaphragm 33 and an annular rim member 34. The rim member 34 is formed with a number of hollow bosses 35 which form the sockets to receive the plugs 31 and it is also formed with a number of swellings 36 the purpose of which will appear below.

v The

diaphragms

32, 33 at their outer perioheries lie against the upstream and downstream faces of the rim member 3 4 and are held in position by upstream and downstream clamping rings 37, 33 and by bolts which pass through the clamping rings, the peripheries of the '

diaphragrns

32, 33 and the swellings 36 of the rim member34. ,7

V J At an inner radius the diaphragms as,

with axial flanges 3?, which abut one another and an "A as are provided hold the

diaphragms

32, 33 in axially-spaced relation at this radiusv The diaphragm 3?. is also provided 'internally with a radially-inwardly-extending fiange 41 1 having atits free edge a spiined axial extension 42 which receives the splined outer race 16a of the bearing 16.

v The clamping rings 37, 38 not only serve to hold the

diaphragms

32, 33 against the rim member 34 but also serve to locate the inner ends of the nozzle guide vanes 14 opensthe outer end of the passage through the associated lade.

The pans 118 are formed each with a hollow boss 12%"? wherein is engaged one end of a tubular plug 121,

the opposite end being engagedin a corresponding hollow boss 122 on the outer casingstructure 313.

The parts ill also have outwardly extending ribs 124 which form dogs to engage between corresponding dog s 125011 the casing structure 13 to locate the outer platform structure in position.

ing, a ring of stator blades extending radially between with respect to one another and for this purpose the clamping ring 37 is provided with a flange portion 43 with an axially-facing annular'slot to receive axial proj'ections at the upstream edgesof'the inner wall parts 23 and the clamping ring 33 is providedwith an axial flange 45 having therein an axially-facing annular slot to receive projections 45mm the downstream edges of the inner wall parts 2 V The annular chamber 47 is 32, 33, flanges 39, 49 and the rim member 34, and the chamber is used as a collector manifold for low-pressure air to be conveyed through the hollow nozzle guide vanes 14 to atmosphere. The air may be low-pressure air which leaks into space 5i) adjacent the compressor, say through a compressor rotor seal, and this air may pass into the chamber 47 through holes 51 in the diaphragm 32. Alternatively or in addition, the air may below-pressure cooling air tapped oli from a low-pressure stage of the engine compressor and conveyed through the shaft 16 to flow through ports 2 therein adjacent bearing 16 into space 53 and thence through rotating'seal 55 which acts as a flow restrictor to space 56. The air then flows through ports 54 in flange 4% from space se to the chamber 47. The air flows'outwardly from the annular chamber 47 through the ducts formed by the hollow "bosses 35 and the hollow plugs 31 into the manifold spaces 31} in the inner platform structures, and then flows outwardly through the hollow nozzle guide vanes 14 into the manifold spaces 19 of the outer platform structures and from thence to atmosphere through ducts aflorded by the tubular plugs 21. v

Since the air is low-pressure air, the mass flow of air.

is less than when the air is high-pressure air, and consequently the engine operates more elhcicntly because less energy is absorbed in the engine in compressing the air specifically tapped for cooling or because the cooling air is leakage air.

It will be noted also that the vanes 14 and their platform structures are of simple construction yet are capable of withstanding heavy loads. Also, the vane structure assists through the

bosses

31, 35 in centralising the bearing'l'fv.

In another arrangement (Figures 3 and'4), instead or" outer wall part 118 thus definesa space 119 into which bounded by the diaphragms said annular structure and said stator casing, each of 7 said stator blades having a passage extending through it and opening/through each end of the blade, means connecting the stator' blades with the annular structure, said means comprising a series of part-annular inner hollow structures between the inner ends of the blades andfsaid annular structure, each of said part-annular inner hollow structures subtending at the axis of the machine an angle equal to the angle subtended at the axis by a plurality of'said stator blades, each of said part-annular'inner 'hollow structures having radially-spaced inner and outer walls,'the outer wall having in it a number of slots equal in number'to said plurality of the stator blades and each of said slots having the inner end of a cor'respondin'g one of the plurality of stator blades rigidly secured therein whereby the passages in said plurality of the stator bladesopen .to the space between said inner and outer walls, each of said inner hollow structures having a single duct connection extendingradially-inwardly from its inner wall to the outer annular part and connecting said. space between the inner and outer walls of the inner hollow structure and the annularchamber, and said series of inner hollow structures together defining a complete annulus, and means connecting the stator blades with the stator casing, said means comprising a second series of outer hollow structures which together form a complete annulus radially between the stator casing and the dially outer ends of thetstator blades being rigidly securediin said slots whereby the outer ends of the passages v in the;stat0r blades open into the spaces between the walls of the outer hollow structures, a plurality of angularly-spaced pressurefluid connections externally of said stator casing, the number of said pressure fluid connections being equal to the number of outer hollow structures, and a singlefduct connection extending radially outwards from the outer walltof each of said outer hollow structuresrto a corresponding one of said pressure fluid connnections. V

, 2, An axial-flow fluid machine according to claim 1, wherein the number of said outer hollow structures is equalj to the number of said inner hollow structures, the inner'wall of each outer hollow structure has therein a number of blade-receiving slots equal to the number of blades-in said'plurality of the stator blades, and the' blades which are secured in'the outer 'wall of each inner hollowstructure, have their outer ends secured in the slots in the inner wall of a corresponding one of the 5 comprises a number of radially-outwardly-extending sockets equal to the number of inner hollow structures, and the inner wall of each inner hollow structure having formed thereon a hollow radial boss engaging plugwise within a corresponding one of said sockets, the duct connection between the inner hollow structure and the chamber being aflorded by said hollow boss and said socket.

5. An axial-flow fluid machine according to claim 1, wherein said annular structure comprises a pair of axially-spaced annular diaphragms, said outer annular part being between said diaphragms adjacent their peripheries and holding them in spaced relation, axial flanges on said diaphragms adjacent their inner peripheries, the axial flanges abutting one another and affording a radiallyinner wall of said annular chamber and clamping means extending through said diaphragms and the outer annular part and holding them in axial abutment, said clamping means also engaging the inner hollow structure and locating them radially with respect to one another.

6. An axial-flow fluid machine according to claim 5, comprising also a rotor, a bearing for the rotor, said 6 bearing having an outer stationary race, said race being supported by one of said diaphragrns at its inner periphery.

7. An axial-flow fluid machine according to claim 1, wherein each of said duct connections extending outwardly from the outer wall of each of said outer hollow structures comprises a hollow boss extending radially outwards from said outer wall, a hollow boss extending outwards from said stator casing, and a tubular plug member having one end engaged in the hollow boss on said outer wall and its opposite end engaging the hollow boss on the stator casing, the tubular plug having its ends part-spherical.

References (Iited in the file of this patent UNITED STATES PATENTS Wislicensus June 2, 1953 Wilkinson Mar. 20, 1956 Hunter Apr. 10, 1956