JPH11257293A - Control device of centrifugal compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the performance by suppressing the increase of the impeller chip clearance as low as possible. SOLUTION: An impeller casing 10 formed of a casing part opposing to the vane end part of a centrifugal impeller and a vaned diffuser 15, to be a movable casing integrally made movable in the axial direction of a rotor rotary shaft 2; a holding means 11 to hold a diffuser vane 16 and a diffuser plate 17 movable integrally to the impeller casing 10; an actuator 12 installed to a compressor casing 5, and to move the impeller casing 10 in the axial direction of the rotor rotary shaft 2; and an impeller displacement detector 13 installed to the compressor casing 5, and to detect the displacement in the thrust direction of the impeller in the compression operating; are provided, and the movement amount responding to the displacement amount detected by the impeller displacement detector 13 is given to the actuator 12, so as to maintain the impeller chip clearance in an adequate value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for controlling a gap (impeller tip gap) between an impeller casing and a centrifugal impeller blade end of a turbine driven centrifugal compressor using high-temperature gas or steam, particularly a multistage centrifugal compressor. About.

[0002]

2. Description of the Related Art Generally, in a centrifugal compressor, a high pressure of gas compressed on a centrifugal impeller (hereinafter referred to as an impeller) of the centrifugal compressor causes a thrust force to be applied to a rotor rotating shaft in an axial direction. In order to work, a rider ring or thrust bearing which receives the force is mounted. Referring to FIG. 4, in which the rotor section of the multi-stage centrifugal compressor is schematically shown,
The thrust bearing 6, for example, between the rider ring and the thrust plate 7 of the rotor rotating shaft 2, is usually 0.1 mm. A gap δ of about several mm
c and Δc ′ are provided. On the other hand, the distance between the impellers 3 and 4 and the impeller casing 10 is also 0.1 mm. Impeller tip gaps Δa and Δb of about several mm are provided. This gap δa
, Δb are factors that greatly affect the performance of the centrifugal compressor, and ideally, 0 is desirable. However, in practice, both the gaps δa and δb require a predetermined amount in consideration of the deformation of the impeller and the casing due to thermal expansion and the like. Further, at least one of the impeller tip clearances requires an amount obtained by adding the maximum value of the clearances δc and δc ′ of the rider ring 6 to the above-mentioned predetermined amount, which is considerably larger than an ideal one. I have no choice.

In the centrifugal compressor having such a configuration, for example, one impeller tip gap δa further increases in the direction of the thrust force, and as a result, the impeller 3 on the increased side becomes larger.
Compression performance is reduced. In particular, the impeller exit blade height
In a compressor having a structure in which b2 (see FIG. 1) is small, the performance reduction rate due to the increase in the gap is considerably large.

A typical prior art for addressing such a problem is known as disclosed in Japanese Patent Publication No. 33800/1994, which has the following configuration. That is, the casing portion facing the centrifugal impeller blade tip (impeller blade tip) is a movable casing movable in the axial direction of the rotor rotation shaft and provided with an adjustment operating device, and the adjustment operating device is an end of the movable casing. Part is fitted in the groove of the sliding ring, the movable casing is divided at equal intervals in the circumferential direction, and these can be moved and tilted in the axial direction.
It is configured by connecting the tip of the piston connection rod of the working cylinder to each divided movable casing, providing a gap detector between the movable casing and the impeller blade tip, and comparing the detection value of the detector with the set reference value to optimize In this configuration, the movable casing is moved so as to form a gap.

According to the prior art having the above-described configuration, the gap leakage loss of the shroud (a band-shaped metal fitting attached to the impeller blade tip) can be suppressed, but since the movable movable casings move in the axial direction, they are strictly required. The movement displacements are slightly different from each other, and a step is generated due to a shift in the shroud portion at the impeller entrance and the exit, so that the gas flow is disturbed and loss due to the turbulence occurs. The turbulence of the flow in this portion has a great effect on the impeller performance itself. In addition, the turbulence of the flow at the impeller outlet greatly affects the performance of the diffuser vane that follows the downstream side.

[0006]

As a result of the above, the loss due to impeller gap leakage can be reduced, but the above-mentioned loss due to turbulence increases. It is.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a bearing which supports an axial thrust force. Therefore, it is possible to improve and stabilize the overall performance of the centrifugal compressor by minimizing the tendency of the impeller tip gap generated due to the change in thrust force to increase, and by eliminating the performance deterioration due to this. An object of the present invention is to provide a control device of a centrifugal compressor that can be operated.

[0008]

The present invention has the following configuration to achieve the above object. That is, the invention of claim 1 according to the present invention includes a rider ring,
In a centrifugal compressor provided with a bearing for supporting an axial thrust force such as a thrust bearing, a casing portion opposed to an impeller blade end portion and a vane diffuser portion of a compressor casing, and integrally formed in an axial direction of a rotor rotation shaft. An impeller casing formed in a movable casing that is movable, holding means for holding the diffuser vane and the diffuser plate of the vane diffuser portion so as to be integrally movable with respect to the impeller casing, and attached to the compressor casing; An actuator for moving the impeller casing in the axial direction of the rotor rotation shaft, an impeller displacement detector attached to the compressor casing, and detecting a displacement of the impeller in a thrust direction during the compression operation;
A control device for a centrifugal compressor, comprising: control means for providing a displacement output corresponding to the displacement detected by the impeller displacement detector to the actuator to maintain a gap between an impeller casing and an impeller blade tip at an appropriate value. It is what constituted.

According to a second aspect of the present invention, in accordance with the first aspect, the holding means is recessed in a portion of the compressor casing facing the diffuser plate and faces the impeller casing. The diffuser plate is formed by a concave portion that is housed so that the diffuser plate can be moved in and out, and a spring that is housed in the concave portion and presses the diffuser plate from the rear side. This is a control device for a centrifugal compressor, which is capable of being pressed against a compressor.

According to a third aspect of the present invention, in accordance with the first aspect of the present invention, the holding means is formed by fasteners such as bolts for integrally fixing the diffuser plate and the diffuser vane to the impeller casing. A control device for a centrifugal compressor.

According to a fourth aspect of the present invention, in accordance with the second aspect, the holding means is provided between the inner peripheral wall of the concave portion and the outer peripheral portion of the diffuser plate housed in the concave portion. A control device for a centrifugal compressor, comprising a seal ring interposed in a gap portion of the centrifugal compressor.

According to a fifth aspect of the present invention, in accordance with any one of the first to fourth aspects, a connection portion between the suction side end of the impeller casing and the suction pipe is provided with an impeller casing. Allow axial displacement, and
A control device for a centrifugal compressor, wherein a flexible joint formed on a member for maintaining airtightness of a connection portion is provided.

According to the present invention, even if the impeller tip rotor gap changes due to deformation of the impeller or rotor rotating shaft due to gas pressure or thermal expansion, the control means outputs a displacement output corresponding to the variation. By giving it to the actuator, the impeller casing is controlled to move in the axial direction of the rotor rotation shaft so as to maintain the impeller tip clearance at an appropriate value. As a result, the compression operation can be continued while maintaining the performance of the entire compressor with high efficiency.

In this case, since the impeller casing forms a single body over the entire periphery surrounding the impeller blade tip and moves integrally, the loss due to turbulent flow as in the case of the conventional divided movable casing divided into several parts. That is, the loss due to the occurrence of a step due to the displacement of the divided movable casing in the shroud portion at the impeller inlet portion and the outlet portion and causing the turbulence of the gas flow, and the automatic control of the impeller tip clearance The performance-retaining action is fully exhibited as expected.

Further, according to the present invention, the diffuser vane and the diffuser plate of the vane diffuser are held so as to be integrally movable with respect to the impeller casing, so that the gas flow in the vane diffuser is disturbed. Can also be prevented.

Further, according to the invention of claim 4 of the present invention, the holding means has a seal ring interposed in a gap between the inner peripheral wall of the concave portion and the outer peripheral portion of the diffuser plate housed in the concave portion. By providing the gas, there is no gas leakage from the diffuser outlet to the inlet, and performance degradation due to this leak can be prevented.

Further, according to the invention of claim 5 of the present invention, by providing the flexible joint at the connection portion between the impeller casing and the suction pipe, the impeller casing can be smoothly moved and the suction side can be moved. Airtightness can be maintained.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings.

FIG. 1 is a partial longitudinal sectional view of a main part of a control device according to a first embodiment of the present invention. The centrifugal compressor 1 shown in FIG. 1 is, for example, a two-stage compressor driven by a turbine. The structure of the rotor portion is basically the same as that of the centrifugal compressor shown in FIG. First
The impellers 3 and 4 of the stage compressor 1A and the second stage compressor 1B are fixed, and each of the compressors 1A and 1B has a compressor casing 5. The rotor rotating shaft 2 is connected to the casing 5
Inside is supported by a radial bearing (not shown),
An intermediate portion of the rotor rotating shaft 2 is also supported by a thrust bearing 6 formed of a rider ring. Therefore,
The rotor rotating shaft 2 and the impellers 3 and 4 are usually set to a pressure of 0. It moves in the axis 2 direction according to the gaps Δc and Δc ′ of several mm.

The compressor casing 5 includes a main body casing 8 in which the rotor rotating shaft 2 is housed, a compression chamber casing 9 surrounding the compression chamber, and an impeller casing 10 opposed to the impeller blade end and the vane diffuser section 15. The compression chamber casing 9 is directly fixed to the axial end face of the main body casing 8 by screwing with a bolt to form a fixed portion. On the other hand, the impeller casing 10
Is fitted in a circular hole in the center of the compression chamber casing 9 by fitting, and is movable alone in the axial direction of the rotor rotation shaft 2, and is formed in a movable casing.

As for the fitting portion between the compression chamber casing 9 and the impeller casing 10, in the illustrated example, the peripheral wall of the circular hole of the compression chamber casing 9 is formed as a short cylindrical surface centered on the rotor rotation shaft 2. On the other hand, the outer peripheral portion forming the maximum diameter portion of the impeller casing 10 corresponds to the short cylindrical surface of the circular hole and is formed on the short cylindrical surface centered on the rotor rotation shaft 2. In the assembled state by fitting, the impeller casing 10 can move in the direction of the rotor rotation shaft 2 while slidingly contacting the compression chamber casing 9 on the fixed side between the two short cylindrical surfaces. A ring groove is formed in the middle of the peripheral wall of the circular hole, and a seal ring 23 is interposed in the groove to maintain airtightness in the fitting portion.

In the centrifugal compressor 1 having such a configuration, the control device according to the first embodiment includes the impeller casing 10 formed in a movable casing, the diffuser vanes 16 of the vane diffuser section 15 and the diffuser plate. Holding means 11 for integrally holding impeller 17 with impeller casing 10, impeller casing 1
Actuator 12 as drive mechanism for moving 0
And an impeller displacement detector 13 for detecting the displacement of the impeller 3 in the thrust direction, and control means 14 for controlling the drive of the actuator 12.

As the actuator 12, for example, a hydraulic cylinder is used, and a cylinder main body is arranged so that an operation axis thereof is parallel to the rotor rotation axis 2, and is on a fixed side of the main body casing 8 or the compression chamber casing 9. The piston rod is attached to the casing and the distal end of the piston rod is connected to the impeller casing 10. Although only one hydraulic cylinder may be attached to the impeller casing 10, two or more hydraulic cylinders having the same structure are arranged at equal divisions around the impeller casing 10 and connected to the impeller casing 10. , A control means 1 to be described later.
4 may be operated synchronously.

In the first embodiment, the holding means 11 comprises a recess 18 provided on the back side of the diffuser plate 17 and a spring 1 housed in the recess 18.
9 is formed. The concave portion 18 is recessed in a portion of the main body casing 8 facing the diffuser plate 17 with a depression having a shape corresponding to the plate 19, and the diffuser plate 17 facing the impeller casing 10 moves in and out of the concave portion 18. It can be accommodated as much as possible. On the other hand, the spring 19 is composed of a plurality of coil springs, and these coil springs are distributed and accommodated in the recess 18 so as to be interposed between the back surface of the diffuser plate 17 and the bottom of the recess 18.

The holding means 11 is such that the spring 19 in the concave portion 18 is moved by the elastic force of the diffuser plate 1.
7 is constantly pressed from the back side to the impeller casing 10 side, so that the diffuser plate 17 is pressed against the impeller casing 10 with the diffuser vane 16 interposed therebetween.
When the impeller casing 10 moves in the direction of the rotor rotation axis 2, the diffuser plate 6 and the diffuser plate 17 move integrally with the casing 10, and are always kept in pressure contact with the impeller casing 10. .

As the impeller displacement detector 13, for example, an inductance type non-contact sensor is used.
Is accommodated in a mounting groove provided in an end face portion or the like facing the impeller disk. This impeller displacement detector 13
Can detect the distance between the opposed impeller 3 to be detected and the back surface of the disk as a change in the electric signal without contact, whereby the impeller 3 can be detected.
Can be detected by converting the displacement in the thrust direction into an electric signal level. The detector 13 is provided with one non-contact sensor at an appropriate position to detect the amount of displacement of the impeller 3 in the thrust direction, and also divides several non-contact sensors equally around the rotor rotation shaft 2. It is housed in several mounting grooves provided on the circumference, and an average value is obtained from the detection values of the sensors, and this is set as a detection value corresponding to the displacement amount of the impeller 3 in the thrust direction. May be done.

The control means 14 comprises, for example, an electronic control circuit and a control output unit.
A converter, an arithmetic unit and a D / A converter are provided as elements, and the control output unit is provided with a hydraulic servo valve as an element. The control means 14 includes the impeller displacement detector 13
Is given as an input signal, that is, an electric signal corresponding to the separation distance of the impeller 3 from the back of the disk, the displacement of the impeller 3 in the thrust direction is first calculated by an arithmetic unit. The amount of axial displacement of the impeller casing 10 required to maintain the gap δa at an appropriate value is obtained by calculation, and the output of the amount of displacement corresponding to this amount of axial displacement is output to the hydraulic cylinder as the actuator 12 via the hydraulic servo valve. Output.

In the first embodiment having such a control device, when the impeller 3 and the rotor rotating shaft 2 are displaced in the axial direction during the compression operation and the impeller tip gap changes, the impeller displacement detector 13 The amount of change in the impeller tip gap is detected by the control unit 14, and the control means 14 immediately obtains a displacement output corresponding to the axial displacement of the impeller casing 10 required to maintain the impeller tip gap at an appropriate value. This movement amount output is given to the actuator 12 via the servo valve for use. As a result, the impeller casing 10 is controlled to move in the axial direction of the rotor rotating shaft 2 so as to maintain the impeller tip clearance at an appropriate value, and is automatically positioned. Therefore, it is possible to always keep the impeller tip gap at an appropriate value and prevent impeller performance from deteriorating.

In the first embodiment, the suction side end of the impeller casing 10 and the suction pipe 2
A flexible joint 22 is provided at a connection portion with the first joint 1. The flexible joint 22 has a well-known structure which is provided at the connecting portion when connecting the pipe end portions to each other, so that airtightness can be maintained while allowing some degree of expansion and contraction and displacement in the eccentric direction. A pipe joint is used. In the first embodiment, by providing such a flexible joint 22, the movement control in the axial direction with respect to the impeller casing 10 can be reliably and smoothly performed, and the airtightness on the suction side of the compressor is improved. It is possible to secure enough.

FIG. 2 is a partial longitudinal sectional view of a main part of a control device according to a second embodiment of the present invention. This second
This embodiment is similar to the control device according to the first embodiment, and corresponding members are denoted by the same reference numerals. A feature of the configuration in the second embodiment shown in the drawing is that a sealing structure for preventing gas leakage is further added to the holding means 11 in the case of the first embodiment. That is. That is, the seal ring 24 is interposed in a gap formed between the inner peripheral wall of the concave portion 18 and the outer peripheral portion of the diffuser plate 17 housed in the concave portion 18. As a specific example of the structure in this case, an annular groove having a semicircular cross-sectional shape is provided in a portion near the center of the outer peripheral edge of the diffuser plate 17, and a seal ring 24 is attached to the annular groove. , And a seal structure.

In the second embodiment, the gap between the concave portion 18 of the main body casing 8 and the diffuser plate 17 is sealed by the seal ring 24, so that gas leakage from the diffuser plate outlet to the inlet can be prevented. And the performance degradation due to this leakage can be prevented. In addition, by interposing the seal ring 24,
Lateral vibration, which is likely to occur when the diffuser plate 17 moves in and out of the concave portion 18 with the movement of the impeller casing 10, can be suppressed, and the original holding performance is stably exhibited.

FIG. 3 is an enlarged sectional view showing a part of a control device according to a third embodiment of the present invention. The third embodiment is similar to the control device according to the first embodiment, and corresponding members are denoted by the same reference numerals. A feature of the third embodiment is that the holding means 11 of the first embodiment is a spring pressing and holding structure using the elastic force of the spring 19. Then, the diffuser vane 16 and the diffuser plate 17 are directly fixed to the impeller casing 10 by fasteners such as bolts, so that the impeller casing 10
Diffuser vane 16 and diffuser plate 17
Is an integral structure.

The holding means 1 according to the third embodiment
As a specific example of the structure of the diffuser plate 1, as shown in the drawing, the diffuser plate 17 and the diffuser
6, while a screw hole for a bolt is screwed in a corresponding portion of the impeller casing 10, and a bolt 20 is inserted through each of the bolt through holes, and then screwed into the screw hole for the bolt. Bolt structure.

According to the third embodiment, the diffuser vane 16 and the diffuser plate 17 of the vane diffuser 15 are integrally fixed to the impeller casing 10 so that the vane diffuser 15 can be used. This is the same as in the first and second embodiments in that the turbulence of the gas flow can be prevented, and furthermore, there is an advantage that the structure is simplified by eliminating the need for a spring.

[0035]

The present invention is embodied in the form described above and has the following effects.

According to the present invention, the movable casing in which the impeller casing, which is the casing portion facing the centrifugal impeller blade end portion and the vane diffuser portion of the compressor casing, can be integrally moved in the axial direction of the rotor rotation shaft. In addition, the diffuser vane and the diffuser plate of the vane diffuser portion are held so as to be integrally movable with respect to the impeller casing, and the movable casing, the diffuser vane and the diffuser plate are integrally integrated by a displacement amount of the rotor in the thrust direction. Because the rotor is moved in the axial direction of the rotating shaft, the gap between the impeller casing and the centrifugal impeller blade end can be always maintained at an appropriate value.Also, at the time of the movement, a step is formed at the impeller outlet or the shroud. And the entire compressor While stably maintaining the performance at a high efficiency state, it is possible to prevent the disturbance of the gas flow at a reduced and vane de diffuser portion of the impeller performance due gap increase of the impeller casing and the centrifugal impeller blade tip.

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional view showing a main part of a control device according to a first embodiment of the present invention.

FIG. 2 is a partial longitudinal sectional view showing a main part of a control device according to a second embodiment of the present invention.

FIG. 3 is an enlarged partial sectional view of a control device according to a third embodiment of the present invention.

FIG. 4 is a schematic structural view of a rotor section of the multi-stage centrifugal compressor.

[Explanation of symbols]

1. Centrifugal compressor 2. Rotor shaft
3 impeller 4 impeller 5 compressor casing
6 thrust bearing 7 thrust plate 8 body casing
9 ... compression chamber casing 10 ... impeller casing 11 ... holding means
DESCRIPTION OF SYMBOLS 12 ... Actuator 13 ... Impeller displacement detector 14 ... Control means 15 ...
Vane diffuser part 16 ... diffuser vane 17 ... diffuser plate 18 ... concave part 19 ... spring 20 ... bolt
21 ... suction pipe 22 ... flexible joint 23 ... seal ring
24 ... Seal ring

Claims (5)

[Claims] 1. A centrifugal compressor provided with a bearing for supporting an axial thrust force such as a rider ring and a thrust bearing, wherein the casing portion opposes a centrifugal impeller blade end and a vane diffuser portion of a compressor casing. ,
An impeller casing formed in a movable casing capable of moving integrally in the axial direction of the rotor rotation shaft, and holding means for holding the diffuser vane and the diffuser plate of the vane diffuser portion so as to be integrally movable with respect to the impeller casing. An actuator attached to the compressor casing for moving the impeller casing in the axial direction of the rotor rotation shaft; and an impeller displacement attached to the compressor casing for detecting displacement of the impeller in the thrust direction during the compression operation. A detector, and control means for providing a displacement output corresponding to the displacement detected by the impeller displacement detector to the actuator to maintain a gap between the impeller casing and the centrifugal impeller blade end at an appropriate value. A control device for a centrifugal compressor. 2. The holding means is recessed in a portion of the compressor casing facing the diffuser plate, and the recess is configured to receive the diffuser plate facing the impeller casing so that the diffuser plate can enter and exit, and is held in the recess. 2. The control device for a centrifugal compressor according to claim 1, wherein the spring is formed by a spring pressing the diffuser plate from the rear side, and the diffuser vane and the diffuser plate can be elastically pressed against the impeller casing by the spring. 3. 3. The control device for a centrifugal compressor according to claim 1, wherein said holding means is formed by fasteners such as bolts for integrally fixing said diffuser plate and said diffuser vane to said impeller casing. 4. The centrifugal compressor according to claim 2, wherein said holding means includes a seal ring interposed in a gap between an inner peripheral wall portion of said concave portion and an outer peripheral portion of a diffuser plate housed in said concave portion. Control device. 5. A connecting portion between the suction side end of the impeller casing and the suction pipe is provided with a flexible joint formed on a member that allows axial displacement of the impeller casing and maintains the airtightness of the connecting portion. The control device for a centrifugal compressor according to claim 1, 2, 3, or 4.