Stator Of Multistage Turbomachine

Abstract

A stator comprises a housing accommodating a guiding device for each stage and a working ring for each stage. The guiding device comprises an external ring and fixed blades secured to the external ring. Working blades of the turbomachine rotate inside the working ring. The external ring is provided with a shoulder at each end face thereof, said shoulder being adapted to limit the radial displacement of the working ring relative to the external ring and extending along the circumference of the external ring. Each end face of the working ring is provided with a groove. This groove extends along the circumference of the working ring and encloses the shoulder. in order to limit the circumferential displacement of the working ring relative to the external ring, the working ring is provided with means comprising a stud. This stud is mounted in the working ring in such a manner that one end thereof is connected to the external ring of the guiding device of the same stage, while the other end is connected to the external ring of the guiding device of the adjacent stage.

Description

The present invention relates to the art of turbomachine building, and more particularly to stators of multistage turbomachines.

The invention may be most advantageously used in axial compressors and in the turbines of gas-turbine engines.

Widely known stators of multistage compressors comprise a compressor housing accommodating working rings of a plurality of stages, working blades rotating inside the rings, and guiding devices of the same stages having fixed blades connected to the external rings thereof. In this embodiment, guiding devices have a joint in the centerplane.

In the known stator, the working rings and the external rings of the guiding devices are interconnected in such a manner that the internal surfaces thereof form smooth outline without steps which defines an air duct, while the external surfaces of these rings are concentric. The external ring of the guiding device of each stage is provided with a shoulder at each face, said shoulder extending along the circumference of the ring. The shoulder at the end face of that external ring, which faces the working ring of the same stage, is formed by the prolongation of the external surface of the ring, whereas the shoulder at the other end face of the external ring, which faces the working ring of the adjacent stage, is formed by the prolongation of the internal surface thereof. The working ring of each stage is provided with a groove made at each end face, said groove extending along the circumference of the working ring and enclosing the shoulder.

The working rings accommodating the working blades rotating with a small gap relative thereto are subjected to a circumferential force due to the resistance offered by the internal surface of the ring to the air entrained by the blades. In addition, the blades may touch the surface of the working ring thereby producing an additional circumferential force which is added to the above-mentioned force and tends to rotate the ring. The rotation of the ring will result in additional heat release due to the friction between the ring and the stator housing, said heat release resulting in deformation of the ring itself and of the housing, whereby it is necessary to fix the working ring in the rotational direction.

The guiding devices of each stage having their fixed blades located in the zone of the moving air flow are subjected to a force which is resultant of a total of all aerodynamic forces applied to every blade. This force has the axial and the circumferential components. The axial component displaces the guiding device along its longitudinal axis, and the circumferential component rotates the guiding device about this axis. The axial component is directed opposite to the air flow in the compressor and in the known stator is sequentially transmitted through all the working rings and guiding devices from the ultimate stage to the first and further to the compressor housing. The circumferential component, in the example under construction, is sequentially transmitted through the joints of the working ring of the first stage to the external ring of the guiding device of the first stage, then to the working ring of the second stage, and so on up to the working ring of the ultimate stage and therefrom to the housing, the circumferential force being transmitted progressively growing from the first stage to the ultimate one. At the ultimate stage, this force represents a total of all the forces applied to the working rings and the guiding devices of every stage. The circumferential force of a respective value is transmitted at each joint by means of studs, each stud having one end press-fitted into one of the end faces of the external ring of the guiding device, while the other end being received in a hole made in the end face of the working ring.

The member of the studs in each joint is defined depending upon the amount of the circumferential force being transmitted.

This pattern of transmission of the circumferential force between the working rings and the external rings of the guiding devices of each stage has the following disadvantages.

The use of double alignment at the joint between the working ring and the external ring of the guiding device by means of the stud and the shoulder each ensuring the alignment in all directions results in additional stresses arising in the stud and in the point of its fastening in the external ring of the guiding device. Since the component parts in the joint exhibit high local rigidity, these stresses may attain substantial value. On the other hand, the utilization of a plurality of the studs in the joint requires accurate arrangement thereof both in radial and circumferential directions, as well as accurate arrangement of the holes in the working ring, the appearance of additional assembly stresses being otherwise possible in the studs and in the points of their embedding for the above-mentioned reasons. This considerably reduces reliability and durability of the stator. When the studs and the holes are arranged with different pitch deviations, each stud will be subjected to a different amount of the circumferential force. Therefore, the requirement as to accurate arrangement of the studs and holes makes this joint difficult in manufacture, whereby the production cost of this assembly is increased.

As far as the attachment of the studs to the external ring of the guiding device is concerned, it will be apparent that the depth of embedding thereof is in inverse proportion to the stresses arising in the embedded portion of the stud and in the adjoining material. In other words, a greater width of the attachment of the studs in the external ring of the guiding device is required in the example under consideration, which results in an increased weight of the stator.

Attempts were made to increase reliability and durability of the stator by lowering stresses in the members utilized to connect the working rings to the external rings of the guiding devices.

In this case, the stator of a multistage compressor comprises a compressor housing accommodating working rings of a plurality of stages, working blades rotating inside these rings, and guiding devices of the same stages having fixed blades connected to the external rings. In this known stator, the external rings of the guiding devices are interconnected in such a manner that their internal surfaces form smooth outline without steps which defines the air duct, while the external surfaces of these rings are concentric.

The external ring of the guiding device of each stage is provided with projections at each end face. The working ring of each stage is recessed at each end face. Upon coupling the working ring to the external ring of the guiding device, a conventional axial splined joint is formed. It is common knowledge that when the circumferential force is transmitted through such a joint, low stresses arise in the contact plane and at the tooth root due to a considerable contact area of the teeth and high rigidity thereof in the direction of the force transmission.

This stator is, however, difficult in manufacture, since the provision of a large number of projections on one part and recesses on the other part is labor-consuming and expensive. This fact appears to be more important if the requirement of accurate manufacturing of the above-mentioned members is taken into account.

Also known in the art is a stator of a multistage compressor comprising a compressor housing accommodating a working ring of each stage, working blades rotating inside this ring, and a guiding device of each stage having fixed blades. The guiding device has a joint in the centerplane. The external of the guiding device of each stage is provided with a groove extending along the circumference of the external ring. The working ring of each stage is provided with shoulder at each end face, said shoulder extending along the circumference and being enclosed by the groove of the external ring. This joint between the external ring of the guiding device and the working ring allows for limiting their relative radial displacement. The shoulder of the working ring is provided with radial projections, and the external ring of the guiding device is provided with radial slots which are adapted to receive the radial projections.

This method for connecting the external ring of the guiding device to the working ring allows for limiting the circumferential displacement of the working ring relative to the external ring.

At the same time, these radial projections are used for aligning the working rings in the housing.

In this case, the circumferential forces are sequentially transmitted through the joints of the working ring of the first stage to the external ring of the guiding device of the first stage, then to the working ring of the second stage and so on up to the working ring of the ultimate stage and further to the housing.

The above-described connection between the working ring and the external ring of the guiding device is substantially a splined joint. It is common knowledge that in transmitting the circumferential force through such a joint low stresses arise in the contact plane and at the tooth root due to a considerable contact area and high rigidity of the teeth in the direction of the force application.

This joint between the working rings and the external rings of the guiding devices is, however, difficult in manufacture, while the provision of the radial projections on the shoulders of the working rings is labor-consuming thereby resulting in high cost of the stator. On the other hand, discontinuous contact between the projections and the compressor housing in the presence of vibration results in local cold hardening of the hosing surface.

It is an object of the present invention to reduce stresses in the component parts of the stator and to improve its reliability in operation.

Another object of the invention is to make the stator more simple in manufacture and to reduce the production cost thereof.

A further object of the invention is to reduce the weight of the stator.

The above and other objects of the invention are accomplished by the provision of a stator of multistage turbomachine comprising a housing accommodating a guiding device of each stage having fixed blades, the external ring of the guiding device being provided with a shoulder at each end face, said shoulder extending along the circumference of said ring, and a working ring of each stage, said ring being provided with means for limiting the circumferential displacement of the working ring relative to the external ring and accommodating working blades rotating therein, the working blades having a groove at each end face, said groove extending along the circumference of the working ring and enclosing the shoulder of the external ring, wherein according to the invention, said means comprises a stud which is mounted in the working ring in such a manner that one end of the stud is connected to the external ring of the guiding device of the same stage while the other end thereof is connected to the external ring of the guiding device of the adjacent stage.

It is advantageous that each shoulder of the external ring of the guiding device have radial slots, the axis of each slot, which extends in parallel with the turbine axis, being aligned with the longitudinal axis of the stud.

It is desirable that the working ring be provided with holes adapted to receive the studs, the longitudinal axis of each hole extending inside each groove.

It is advisable that the diameter of the stud be slightly greater than the width of the groove.

This embodiment of the stator ensures a reduction in stresses in the component parts therof. This is achieved due to the fact that the stud mounted in the working ring being received with one end in the hole of the external ring of the guiding device of the same stage and with the other end in the hole of the external ring of the adjacent stage, is embedded along the entire length thereof or at least in the zones located directly adjacent to the ends thereof. That is, that part of the stud, which is subjected to the force applied from the adjacent external ring of the guiding device, is several times shorter than the length of the stud attachment or than the distance between the points of attachment. It is common knowledge that in this case minimum stresses will arise both in the stud and in the hole. On the other hand, if the stud axis extends inside the groove, and the diameter of the stud is greater than the width of the groove, those parts of the stud, which are subjected to the force applied from the guiding devices are also embedded in the same working ring with two segments along the generatrix lines in addition to the above-described attachment of the stud. This contributes to further reduction in stress in the stud proper and in the working ring. Since the stud is received in the slot which is radially arranged relative to the working ring, there are no stresses in the stud in this direction. Due to the reduction in stresses in the component parts of the stator, its reliability in operation is improved.

Due to such an embodiment of the stator, the manufacture thereof is facilitated, since the drilling of the holes for the studs and the installation of the studs are simple technological steps. Simplified technological procedure of the manufacture of the stator results in a reduced production cost thereof.

Furthermore, this embodiment of the stator allows for trimming its weight, since the above-described embedding of the studs makes it possible to minimize the thickness of the shoulders of the working rings wherein the holes for the studs are made.

Other features and advantages of the invention will become apparent from the following description of the embodiment thereof with reference to the accompanying drawings wherein:

FIG. 1 schematically shows a stator of a multistage turbomachine according to the invention in a longitudinal cross-sectional view;

FIG. 2 is a fragmentary longitudinal cross-sectional view of the stator according to the invention with the working ring and the guiding device on the enlarged scale;

FIG. 3 is an enlarged sectional view taken along the line III--III in FIG. 2.

A stator of a multistage turbo-machine, such as compressor comprises a housing 1 (FIG. 1) accommodating a guiding device 2 of each stage having fixed blades 3, and a working ring 4 of each stage accommodating working blades 5 rotating therein. The guiding device 2 has an external ring 6 provided with shoulders 7 at each end face thereof, the shoulders extending along the circumference of the ring 6. The working ring 4 is provided with radial shoulders 8 each having grooves 9 (FIG. 2) extending along the circumference of the ring 4. The grooves 9 of the working ring 4 enclose the shoulders 7 of the external ring 6 of the guiding device 2. The shoulders 8 are provided with mutually coaxial holes 10 which receive studs 11. The shoulders 7 are provided with radial slots 12 (FIG. 3), the axis of each slot extending in parallel with the axis of the turbo-machine and being in alignment with the axis of the stud 11. The studs 11 are received in these slots 12.

The housing 1 (FIG. 1) is provided with 13 for positioning the working rings 4.

This ensures mutual arrangement of the internal surfaces of the working rings 4 and the external rings 6 of the guiding devices 2 which define smooth boundary of the air duct.

Each guiding device 2 directly following the working ring 4 is included in the body of the same stage as said working ring 4. Each working ring 4 directly following the guiding device 2 is included in the body of the next stage.

During the operation of the multistage compressor, the circumferential forces are transmitted from the working ring 4 of the first stage to the external ring 6 of the guiding device 2 of the first stage, then to the working ring 4 of the second stage and so on up to the working ring 4 of the ultimate. The working ring 4 of the ultimate stage is provided with a flange 14 which is adapted to transmit a total circumferential force to the housing 1 of the compressor by means of bolts 15. The circumferential force is transmitted through the stud 11 (FIG. 3) and the surface 16 of the slot 12 in contact with the stud 11. The studs 11 are made with the diameter which is greater than the width of the groove 9, whereby the stud has greater rigidity and larger bearing surface in the working ring 4, which in combination with the fastening of the stud 11 in two points spaced apart of a substantial distance considerably reduces stresses in the stud 11 proper and in the adjoining material of the working ring 4. The radial slots 12 are made wider than the stud diameter, whereby during the assembly there are no assembly stresses in the stud 11 and in the working ring 4, as well as in the external ring 6 of the guiding device 2 in the circumferential direction, and since the slot 12 is arranged radially, there is no assembly stresses in the above-mentioned members in the radial direction as well.

Since the studs 11 and the slots 12 are non-uniformly distributed along the circumference of the rings within the range of the manufacturing tolerances, they are differently loaded during the transmission of the circumferential force, thereby resulting in different stresses arising in the studs 11 and in the fastening zones thereof.

In order to equalize stresses arising from the circumferential forces in the studs 11 differently located along the circumference, only one side of the slot 12, namely the working side thereof contacting the stud 11 during the operation, should extend precisely along the circumference. This embodiment of the slot 12 improves technological procedure of its manufacture, since it is easy to make the slot with only one side which is to be accurately located.

It will be apparent that all the above considerations are equally applicable for a stator, in which the studs and the grooves are included in the body of the external rings of the guiding devices, while the shoulders and the holes are included in the body of the working rings.

Claims

1. A stator of a multistage turbo-machine comprising:

a housing of a turbo-machine;

a guiding device of each stage of the turbo-machine accommodated in said housing and including an external ring and fixed blades secured to said external ring;

a working ring of each stage fixed in said housing;

annular shoulders for limiting radial displacement of said working ring relative to said external ring, one shoulder being made at each end face of said external ring;

an annular groove at each end face of said working ring, said groove enclosing said shoulder of said external ring; and

limiting means for limiting the circumferential displacement of said working ring relative to said external ring, said limiting means comprising:

a plurality of studs spaced along a circle, rigidly secured in each said working ring and extending substantially axially through said working ring, opposite ends of each stud being substantially located in correspondence annular grooves at opposite faces of said working ring;

a plurality of axial slots in said shoulders of said external ring, each of said slots receiving one end of one of said studs and the longitudinal

2. A stator according to claim 1, wherein said axial slots are

3. A stator according to claim 2, wherein each of said studs has a diameter greater than the width of said grooves at the end faces of said working

4. A stator according to claim 3, wherein said working ring has a flange at either end thereof, the end of each of said studs being rigidly embedded in the flange body.