JPS6050999B2 - Axial flow compressor stator structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to gas turbine engines, and more particularly to compressor stators for gas turbine engines.

Gas turbine engines must be designed and constructed to ensure adequate structural safety of the individual components while maintaining the desired aerodynamic performance.

In the compressor section, a stator surrounds the rotor assembly. The compressor blades extend radially outwardly from the rotor across the working medium flow path, with their tips proximate opposing surfaces of the surrounding compressor stator to form a gas seal between the rotor and the stator. are doing. On the other hand, the compressor vanes extend radially inward from the compressor case across the flow path of the working medium, and their tips are close to the opposing surface of the rotor to form a gas seal between the rotor and the stator. ing.
The aerodynamic performance of a compressor is highly dependent on the size of the tip gap between the rotor and stator at the tip of the blades and vanes, and even a slight reduction in the tip gap will improve the compression. The aerodynamic performance of the aircraft can be significantly improved. All faces of the rotor are concentric with their opposing vane tips.

Ideally, all sealing surfaces of the stator would also be concentric with their opposing blade tips. If so, the gaps at the tips of the blades and vanes can be minimized. However, if there is a risk of eccentricity between the fixed part, the compressor case, and the rotating part, the rotor, in order to prevent destructive contact between the rotor and the stator during engine operation, The gap between the two must be larger than that. One structure of the compressor case of an axial gas turbine consists of a series of annular rings bolted together and axially connected, with every other ring in the series being a stator vane. Two adjacent rings supporting the rows of stator vanes are joined to each other through an intermediate ring interposed therebetween, and a seal facing the tip of the intermediate ring capillary blade. There are some structures that are given to the surface.

In such a structure, when assembling the rings, the concentric error between adjacent rings that are joined to each other is kept within a limited value, but when the adjacent rings are joined together in sequence, Errors related to concentricity accumulate as
Misalignment between the first and last stages of the stator assembly can be significant. Therefore, in a compressor having such a case structure, the gaps at the tips of the blades and vanes are irregular as described above. The design shall be large enough to allow for the possibility of accumulation of Another structure of the compressor case, especially in gas turbines used in industrial applications, is that the compressor case is divided in the axial direction and faces each other! In some cases, the two halves are joined by an axial flange to form a single compressor case.

In a compressor with such a structure, during a temperature transition state where the temperature of the engine gradually changes, such as when the engine is started, the mass distribution along the circumferential direction of the case is uneven and uniform, and the mass distribution in the flange area is uneven. There is a problem in that the concentration of mass in this area is higher than the concentration of mass in other parts, and a delay in temperature rise occurs in the part where the concentration of mass is high, resulting in distortion of the case. In this case, components such as inner rings and vanes that are supported by areas of the case with high mass concentration are supported by areas with low mass concentration during transient conditions where the case temperature is increasing. It is located radially inward compared to similar components, and conversely located radially outward during temperature transitions when the case temperature is decreasing. Therefore, in this case, there is a
Sufficient clearance must be provided to prevent destructive contact between the compressor case and the compressor case in areas where it has greater mass, and the overall clearance must be set to a larger limit. No. When the compressor case is constructed as a single case that is integrally formed seamlessly over its entire circumference and has a uniform mass distribution over its entire circumference, such rings may be assembled axially. air gaps at the tips of the blades and vanes compared to the case of a compressor case with structural area or axially divided structure.
may be further reduced to obtain higher aerodynamic performance.

In this case, the grooves that hold the vanes are placed around the inner circumference of the compressor case, so that the concentricity between rotor and stator guaranteed by the integrity of the compressor case over its entire circumference can be better utilized. It is conceivable to form it directly on the surface.

Immediately forming grooves for holding vanes on the inner peripheral surface of the compressor case does not apply to compressor cases that are integrally formed over the entire circumference, but for example, Japanese Patent Publication No. 46-1732
This is proposed in Publication No. 7. However, when forming grooves for holding vanes directly on the inner peripheral surface of the compressor case for a compressor case that is integrally formed around the entire circumference, it is necessary to form grooves in the grooves. In order to fit the vane, a notch must be formed in at least a portion of the annular peripheral edge defining the groove along its circumferential direction.
However, due to the formation of such a notch, a large stress concentration occurs around the notch in the compressor case, which is constructed as a single continuous structure over the entire circumference. This causes distortion in the compressor case, and furthermore, there is a problem that there is a risk that the compressor case may be destroyed. In a compressor case with a single structure that is continuous over the entire circumference, the inner wall surface of the compressor case is not substantially processed in any way, and a ring member is fitted along the inner circumferential surface of the compressor case. A structure in which the vane is supported by the ring member is proposed in US Pat. No. 3,024,968.

It is believed that such a stator structure not only avoids the problem of stress concentration as described above, but also has the advantage that the vanes can be mounted within the compressor case while keeping the overall stress acting on the compressor case low. However, in the structure shown in this U.S. patent, two rings located on both sides of each blade are each provided with grooves extending along the two rings, and two grooves in each of these two rings are provided with grooves at the base of the blade. Since a pair of claws protruding from both sides of the compressor case engage with each other, a fairly thick layer along the inner circumferential surface of the compressor case is used only for attaching the ring member. The disadvantage is that the diameter of the compressor case becomes considerably larger for a stator of the same effective inner diameter. A stator structure that can avoid both of the disadvantages of the above-mentioned two known technologies regarding the stator and vane mounting structure is disclosed in Japanese Patent Publication No. 46-1 mentioned above.
The same circumferentially integral compressor case as in the '7327 publication is disclosed in US Pat. No. 2,857,093.

In this structure, a groove-like track extending in the circumferential direction is formed along the inner circumferential surface of the compressor case, and a band-like member that fits and engages with the track is installed within the track. The base of each vane, which has a corresponding wedge-shaped cross-section, is fitted into the wedge-shaped hole formed in the cross-section of the strip material at predetermined intervals along the strip, whereby each vane is It is starting to be retained. This vane mounting structure can also be applied to a compressor case that has a continuous integral structure over the entire circumference. However, in the structure of this U.S. patent, the strip is perforated with a large number of wide holes along its length, so that it has to have sufficient strength and stiffness throughout. Otherwise, the strip must be secured to the compressor case by screws or the like at all midpoints of adjacent vanes, as in the illustrated embodiment of this U.S. patent. In addition, there is a problem in that the number of steps required for attaching the vane to the compressor case or removing the vane during maintenance or replacement is significantly increased. In addition, when holes are formed in the compressor case itself to allow the vanes to pass through, as shown in another embodiment in this U.S. patent specification, the strength of the compressor case is significantly impaired and at the same time air leakage occurs. New problems are bound to arise. The present invention relates to the installation of vanes to a compressor case when the compressor case is designed to have a seamlessly integrated structure over its entire circumference in order to improve the aerodynamic performance of the compressor case. To provide a stator structure for an axial flow compressor having a new and improved vane mounting structure that can address the problems that arise when applying the above-mentioned conventional techniques and avoid these problems. The purpose is to According to the present invention, the present invention provides a compressor case which is integrally formed seamlessly over the entire circumference and provides at least one vane stage, and a circumferential track provided on the inner surface of the circumferential wall of the compressor case. a plurality of vane assemblies removably mounted to the compressor stator, each of the vane assemblies being disposed to extend along a circumferential surface of the circumferential track; an arcuate retention device attached to a compressor case; a base having a base formed with a retention slot slidably receiving the arcuate retention device and retained by the arcuate retention device engaged within the retention slot; at least one vane extending radially inwardly from the base to the other free end toward the center of curvature of the arcuate retainer; This is accomplished by a compressor stator characterized in that it includes an end plate that prevents the compressor from moving.

According to the configuration of the present invention as described above, a slot is formed at the base of each vane on the vane side, and the vane is compressed by receiving the slot into the arcuate holding device attached to the compressor case. Since it is retained from the compressor case, the arch-shaped retaining device may be formed with a uniform cross-section over its entire length, and its width is naturally narrower than the base of the vane; It is only necessary to provide a circumferential track wide enough to receive the base of the vane, and the annular space along the inner circumference of the compressor case can be used to accommodate the arcuate retainer and the vane, without wasting space solely on the arcuate retainer. The space for accommodating both the base can be used more effectively.

In addition, such an arch-shaped retaining device has a uniform cross section with no notch in the middle, and its cross-sectional dimension can be made sufficiently large in relation to the dimension of the base of the vane. By simply attaching it to the compressor case at a very small number of points, such as one or two points at either end or in addition, all the parts that engage with it due to its own strength and rigidity are attached to the compressor case. The vane can be stably supported. Additionally, in this case, by sequentially connecting a plurality of arcuate holding devices along the circumferential track, vanes can be later installed all around the inner peripheral surface of the compressor case. There is no need for the compressor case to be provided with a notch that serves as a starting point for attaching or removing the vane. The base of the vane also engages the arcuate retention device in a manner that envelops the arcuate retention device within a slot formed therein, the arcuate retention device engaging the interior surface of the compressor case in an area corresponding to the opening of the slot. Since the base of the vane is not only positioned by the arcuate retainer, but also directly by the compressor case, the vane is positioned more directly relative to the compressor case. clearly and accurately defined,
The concentricity of the inner ends of all vanes with respect to the rotor center is further improved. By the way, if the inner end of the vane, which is held at the base by the inner circumferential surface of the compressor case and extends inwardly toward the rotor, is a free end, and the vane is supported in a so-called cantilever type, A certain amount of slack or clearance is provided in the retention of the vane base to the compressor case so that the vibration energy of the vane is dissipated by frictional sliding between the vane base and its retainer. A technique for preventing problems such as damage caused by such a problem has already been disclosed in the aforementioned Japanese Patent Publication No. 46-17327.

In order to effectively dissipate the vibration energy of the vane using this technology and to maintain a stable gap between the vane tip and the rotor to a minimum, it is necessary to It is necessary to secure a gap of a predetermined size with high precision. In this regard, according to the vane holding structure according to the present invention as described above, the shape of the slot formed at the base of each vane and the cross-sectional ring of the arcuate holding device are accurately secured with a predetermined gap therebetween, In addition, when the vane is attached to the inner surface of the compressor case by the bow-shaped holding device, the quality of the actual product must be controlled so that a predetermined gap is accurately secured between the base of the vane and the inner surface of the case. This is significantly easier than the case where the vane retaining grooves are directly formed on the inner surface of the compressor case as in Japanese Patent No. 17327. Therefore, as one embodiment of the present invention, in a compressor stator having the basic configuration as described above,
Between the mutually engaging surfaces between the base of the vane and the circumferential surface of the circumferential track and between the base of the vane and the arcuate retention device, the vane is tilted slightly in the direction of its axis relative to the compressor case. It is suitable for implementation in a manner that leaves a gap that allows for These and other objects, features, and advantages will become apparent from the following detailed description of embodiments of the invention, which is given with reference to the accompanying drawings.

The gas turbine 10 shown in FIG. 1 is an axial flow engine of the type in which a multi-stage compressor 12 is connected to a multi-stage turbine 14 via a combustor 16.

Air is compressed in a compressor and mixed with fuel in a combustion section to produce a hot gas that is expanded through a series of nozzles in a turbine section. The more air an engine compresses and uses, the more power or thrust is generated in the engine. Portions of the multi-stage compressor are shown in cross section in FIG. Rotor assembly 16 includes a plurality of compressor wheels 20 axially separated by spacers 22 . Each compressor wheel includes a disk 24 and a plurality of blades attached thereto, the blades on each wheel being indicated at 26. Each blade has a pedestal 28 at the base of the wing 30. The axial gap between the blade pedestals of adjacent wheels is filled by an annular sealing member. The rotor assembly is radially surrounded by a compressor stator 34 having a plurality of vane stages 36, each of which is located in a circumferential rack 38 in the compressor case 40. installed inside. As shown in FIG. 3, each page has a plurality of vane assemblies 42 including one or more vane 4-spheroid retainers 46 and a pair of end plates 48. As shown in FIG.

Each vane assembly is retained in the circumferential track by one or more bolts 50 that pass through the case and engage an arcuate retainer. Each compressor vane includes a wing section 52, a base section 54 having a retention slot 56, and a tip section 58, as shown in FIG.

An axial clearance 60 is provided between the base and the compressor case, and a radial clearance 6 is provided between the base and the arcuate retainer.
2 is provided. As shown in FIG. 5, each vane has a case support surface that opposes the case vane support surface 66 and a retainer support surface 68 that opposes the arcuate retainer vane support surface 70. During assembly of the compressor, one or more vanes 44 are slidably attached to each arcuate retainer 46;
A T-shaped arcuate retainer engages a correspondingly shaped slot in the base of each vane.

An end plate 48 is secured to each end of the arcuate retainer for retaining the vanes mounted thereon. A plurality of vane assemblies are bolted to each circumferential track to form a respective compressor vane stage 36, with each assembled vane extending radially inwardly across the working medium flow path. Each end plate also serves to prevent circumferential movement of the vanes along the track during engine operation. The number of vanes installed within each vane assembly varies according to the size and weight of each component.

The greater number of vanes included in each vane assembly reduces the number of steps used to assemble one complete vane stage to the compressor case. The smaller number of vanes included in each vane assembly reduces the weight of a single vane assembly, making it easier to install within the compressor case. In one embodiment, one vane stage has individual vane assemblies, each vane assembly having approximately three
It has a weight of 0 Bond (13.6k9) and contains 14 vanes. Typically up to w vane assemblies are used. The number of vanes in the final vane assembly is limited by the length of the arch retainer chord.
The chord length of the last arch retainer must be less than the distance between the vane tips 58 that the vane assembly passes when it is installed into the circumferential track from the radial inside. In the above embodiment, the fifth vane assembly is split and includes a vane assembly with B vanes and a vane assembly with one vane, as shown in FIG. The vane assemblies pass through the compressor case and are bolted into the circumferential track by bolts that engage the arch retainer of each vane assembly. Vane assemblies having only one vane are mounted within the circumferential track in the same manner as vane assemblies having multiple vanes. The illustrated embodiment of the invention is adapted to dampen vibrational energy in the compressor vanes during engine operation.

Axial clearance 60 between the base of each vane and the compressor case
and an axial clearance 62 between the base of each vane and the corresponding arch retainer to allow limited movement of the vanes after each vane assembly's arch retainer is installed in the compressor case. In a typical embodiment, both the radial and axial clearances are between 0.025 and 0.330 TIn. During operation of the compressor, the vanes are subjected to pressure loads and assume an inclined position as shown in FIG.

The vane is oriented toward the front or low pressure side of the compressor until its retainer abutment surface 68 abuts the retainer vane abutment surface 70 and simultaneously the case abutment surface 64 abuts the vane abutment surface 66. tilt. In the normal operating range of the engine, the engine's natural vibrational loads periodically exceed the static pressure loads on the vanes, causing the vanes to tilt from their forward positions to their rearward positions as shown in FIG. Rearward movement of the vanes is countered by a pressure load that cushions the wing surface and dissipates vibrational energy from the vane. Furthermore, frictional damping also occurs between the lateral abutment surfaces of adjacent vanes and between the abutment surfaces of each vane in contact with the arch retainer or the case. Removal of vibrational energy from gas turbine compressor vanes is generally done by
It is removed via a rigid mounting structure that connects the vane to the case.

In such a structure, the life of the vane is shortened because vibration stress is concentrated at the joint between the vane wing and the vane base. The accumulation of vibrational stress at this joint will eventually cause the vane to crack or break. The vanes mounted with gaps as described above are not rigidly attached to the case, and therefore do not generate excessive vibration stress. The compressor case has a substantially U-shaped track machined into the inner circumferential wall.

The absence of vane mounting slots allows case stresses to be evenly distributed over the entire circumference of the case, thereby maximizing case life. Stress concentration occurs at the inside corners of the bow-shaped retainer and the vane base, but
The arch retainer and vanes can be easily replaced at low cost if structural cracks develop. Movement of the vanes relative to the case and arch retainer causes wear along the contact surfaces.

To prevent excessive wear, the contact surfaces are treated with a material that presents a hard surface. In the preferred embodiment shown, the structure is:
It has a simple geometry that allows for the application of hardfacing materials to the abutment surface. Significant aerodynamic improvements are obtained with a compressor constructed in accordance with the present invention.

In one embodiment, 10 inches of 100 powder is applied over the entire length of the compressor at the tips of the blades and vanes.
．． Compressor efficiency decreases by 1% when a clearance increase of 2,547 wt) occurs.A common design goal is to control the tip clearance to within 1% of the wing width, which is For example, for a diameter of approximately 50 inches (1270TI0n), there should be 100 blade inches (0.965 mI) between the vane or blade tip and its corresponding sealing surface.
n) to provide a nominal clearance of Controlling the tip clearance requires controlling the distortion of the compressor case and the concentricity of the engagement surfaces with respect to the common axis. Essential.

Control of compressor case strain is achieved by using a non-split compressor having a uniform cross section along its periphery at any axial location. By using a non-split compressor, a uniform cross section can be obtained, and the joints in the split compressor case! Mass concentration due to flanges can be avoided. The portion of the split case that has a large mass, ie, the flange, exhibits a delay due to thermal response. The non-uniform thermal response distorts the case sealing surface at the blade tips from a circular shape, changing the radially inward position of the compressor vanes. In the segmented case, the tip clearance must be adjusted to ensure a range of thermal responses rather than a single thermal response, as in the preferred embodiment described above. Must be. The second major problem with maintaining minimum tip clearance is establishing concentricity errors between opposing compressor members.

Many gas turbines in use today use a dual case stator construction, where the inner case supports the compressor vanes and the outer wall provides structural support for the rotor bearings. The vane-supporting inner case includes a plurality of cylindrical vane support devices arranged in axial proximity and connected by bolts. Each cylindrical support is machined to provide concentricity tolerances about its own axis. When these cylindrical supports are bolted together, the concentricity deviation may increase from the first to the last cylindrical support. In the compressor case of the present invention, each circumferential track is machined relative to the same axis, which is the axis of the compressor case. There is therefore a single uniform concentricity error in all axial stages of the compressor. The compressor rotor produces the same type of error formation as that experienced in a dual compressor case, but the concentricity of the rotor appears to maintain rotor balance and is already precisely controlled, reducing error formation. The degree of this is not very large. Furthermore, by removing the inner case of the compressor, the cost of the stator can be reduced significantly, and in the embodiment described above, the reduction is approximately 113 times.

A single case construction consists of fewer pieces, thus reducing the complexity of its assembly. Single case constructions are lighter than double case constructions and are mass balanced to provide improved blade tip clearance. In mass balancing, the mass of the compressor case at any axial location is increased to match the predicted thermal response at that axial location.

The thermal response of a compressor with double case construction is similarly controlled, but its geometrical handling is more complex and the exact strain is more difficult to predict. Although the invention has been described in terms of a preferred embodiment having a pair of end plates, one at each end of each arch retainer, a single end plate attached to one end of each arch retainer is provided. Even when the vane is moved in the circumferential direction along the track on the inner wall of the case, it is possible to effectively prevent the vane from moving in the circumferential direction.

Although this invention has been described in terms of preferred embodiments, it will be apparent to those skilled in the art that various modifications may be made within the scope of this invention.

[Brief explanation of the drawing]

FIG. 1 is a simplified front view of an axial flow gas turbine engine. 2 is a longitudinal sectional view of the compressor section of the gas turbine engine shown in FIG. 1. FIG. FIG. 3 is also a cross-sectional view of the compressor section. FIG. 4 is a cross-sectional view taken along line 4--4 in FIG. FIG. 5 is a sectional view of the compressor vane mounting portion under frictional load. FIG. 6 is a sectional view of the compressor vane mounting portion in a vibrating state when a vibrating load acts in a direction opposite to and exceeding the gas pressure load. 10... Gas turbine, 12... Compressor, 14... Turbine, 16
...Combustor, 18...Rotor assembly, 20...Compressor wheel, 22...Spacer, 24...Disc, 26...Blade, 28...Base, 30...・
Wing section, 32... Air seal, 34... Stator, 3
6... Vane stage, 38... Circumferential track,
40... Compressor case, 42... Vane assembly, 44
... Vane, 46 ... Arcuate holding device, 48 ... End plate, 50 ... Bolt, 52 ... Wing part, 5
4... Base, 56... Holding slot, 58... Tip, 60... Axial gap, 62... Radial gap, 64... Case contact surface, 66... Vane Contact surface, 68... Holding device contact surface, 70... Vane contact surface.

Claims (1)

[Claims] 1. A compressor case that is integrally formed seamlessly over the entire circumference and provides at least one vane stage, and a plurality of vane stages that are removably mounted within circumferential tracks provided on the inner surface of the peripheral wall of the compressor case. vane assemblies, each vane assembly being disposed within the circumferential track and extending along a circumferential surface of the vane assembly and mounted to the compressor case. an arcuate retention device and a base portion formed with a retention slot for slidably receiving the arcuate retention device, and retained by the arcuate retention device engaged within the retention slot from the base to the other free end; at least one vane extending radially inwardly toward the center of curvature of the arcuate retention device and attached to one end of the arcuate retention device to prevent circumferential movement of the vane along the arcuate retention device; A compressor stator comprising an end plate.