JPH0599199A - Centrifugal compressor - Google Patents

Abstract

PURPOSE:To provide a wide operation range and high operating efficiency by arranging vane units with vanes different in chord length on the inner periphery side of resting vanes arranged in a diffuser so that each vane can be projected into a diffuser flow passage selectively for operating flow. CONSTITUTION:In a centrifugal compressor, a flow 2 compressed by an impeller 1 enters into a diffuser 4 encircled by a casing 3, where kinetic energy possessed by the flow 2 is converted into pressure. In this case, several vane units 5 movable toward the rotational axis of the impeller 1 and several resting vanes 6 are arranged. The vane units 5 with short-chord vanes 5a and long-chord vanes 5b integrated are arranged on an annular plate 8 so as to rise on and set in a diffuser passage through the operation of an actuator 7. The vanes 5a are projected into the diffuser passage in the state that the compressor has a large operating flow while the vanes 5b are projected in the state that it has a small operating flow, to provide high efficiency within a white operation range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal compressor, and more particularly to a high speed centrifugal compressor which requires a wide operating range and high efficiency.

[0002]

BACKGROUND OF THE INVENTION Industrial centrifugal compressors require high efficiency as well as a wide operating flow range. In order to obtain high efficiency, a diffuser with blades is used which can convert the kinetic energy of the flow flowing out of the impeller into pressure with high efficiency. On the other hand, the operating flow range of many centrifugal compressors with vaned diffusers is often limited by the diffuser. That is, the large flow rate side is limited by the occurrence of so-called chokes, and the small flow rate side is limited by the stall of the diffuser. The flow passage cross-sectional area between the blades affects the occurrence of chokes, and the flow passage cross-sectional area between the blades and the blade angle influence the stall. In the case of a diffuser with blades composed of stationary blades, it is difficult to obtain a wide operating flow rate range because the flow passage cross-sectional area between blades and the blade angle are unchanged. For this reason, it has been proposed to make the blades movable so that the flow passage cross-sectional area between the blades and the blade angle can be changed. Further, it is proposed to provide a guide to prevent the stall of the blades.

Japanese Patent Laid-Open No. 57-159998 discloses a diffuser with blades for changing the flow passage cross-sectional area between the blades.
A technique is disclosed in which a rotatable small blade is provided at the blade inlet of the blade and the angle of the small blade is changed according to the flow rate. Further, Japanese Patent Laid-Open No. 58-124099 discloses a diffuser in which a stationary blade and a movable blade having a chord length of the same length are arranged, and the protruding length of the movable blade is changed according to the flow rate. There is. Furthermore, in order to prevent stall, JP-A 1-2477
No. 98 discloses a technique in which a small blade is provided near the leading edge of the blade of a diffuser with blades.

[0004]

In the above-mentioned first prior art, the mechanism is complicated and requires a large number of parts in order to rotatably support and drive the small blades. Further, in the second prior art, since the movable blades are formed to have the same chord length, the operation flow rate is reduced (the inlet compressor of the centrifugal compressor is at the base position).
Although the serge limit low flow can be moved to the low flow rate side when the flow rate is narrowed), there was a problem that the serge limit flow rate could not be sufficiently reduced when the operating flow rate was not reduced. Furthermore, in the third conventional technique, stall can be suppressed by the action of the small blade even at a small flow rate, but there is a problem in that efficiency is reduced.

An object of the present invention is to provide a centrifugal compressor which can obtain high efficiency in a wide operating range from a large flow rate to a small flow rate.

[0006]

In order to solve the above problems, stationary blades are arranged on the outer periphery of an impeller, and a kinetic energy of fluid discharged from the impeller is converted into pressure by the action of the stationary blades. In a centrifugal compressor equipped with a blade, a blade device composed of a blade having a large chord length and a blade having a small chord length is arranged on the inner peripheral side of the stationary blade, and the blade device has a large operation flow rate of the compressor. In such a state, a blade having a small chord length is projected into the diffuser flow path, and at a state where the operation flow rate is small, at least a blade having a large chord length is projected into the diffuser flow path. ..

[0007]

The stationary vanes forming the diffuser with vanes convert the kinetic energy of the fluid discharged from the impeller into pressure with high efficiency, and a vane having a large chord length and a small vane on the inner peripheral side of the stationary vane. The blade of the blade device is forced to guide the fluid discharged from the impeller along the stationary blade, so that the separation of the internal flow is suppressed, and the stationary blade The value of the minimum limit flow rate is remarkably smaller than that of the case only. When the operating flow rate is low, the blade with the short chord length is projected into the diffuser flow path.
When the flow rate approaches the minimum limit flow rate, the cross-sectional area of the flow path of the stationary blade becomes too large, so the efficiency of converting the kinetic energy of the fluid into pressure decreases, but even the blade with a longer chord length has a diffuser flow path. When it is made to project inward, the fluid is sufficiently decelerated, and a decrease in conversion efficiency can be prevented.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment will be described below with reference to FIGS. 1 is a cross-sectional view of a centrifugal compressor, FIGS. 2 and 3 are operation explanatory views of a blade device, FIG. 4 is a layout diagram of a stationary blade and a blade device, and FIG. 5 is an external view of the blade device. In FIG. 1, the flow 2 compressed by the impeller 1 flows into a diffuser 4 surrounded by a casing 3. The diffuser 4 is provided with a plurality of vane devices 5 and stationary vanes 6 supported by an actuator 7 and movable in the rotational axis direction of the impeller 1 to convert the kinetic energy of the flow 2 into pressure with high efficiency. Convert.
The blade of the blade device 5 is composed of a blade 5a having a small chord length and a blade 5a having a large chord length. The flow meter 91 calculates the flow rate from the compressor operation flow rate signal detected by the flow rate detector 90 provided in the flow path of the compressor system. The actuator controller 92 receives the output signal of the flow meter 91 and operates the actuator 7. These flow rate detectors 9
0, a flow meter 91 and an actuator controller 92 constitute a control device 93. When the operating flow rate is large, as shown in FIG. 2, the blade 5a having a smaller chord length and height than that of the stationary blade 6 is arranged on the inner peripheral side of the stationary blade 6 and protrudes into the diffuser flow path. ing.

The blade 5a forcibly guides the fluid discharged from the impeller 1 along the stationary blade 6, so that the flow from the stationary blade 6 is separated even if the operation flow rate passing through the compressor is reduced. As compared with the case where the blades 5a are suppressed, the compressor can be operated at a much smaller flow rate without entering the surge. The front edge of the blade 5a (a part or all)
Is configured to incline to the downstream side, the interaction between the blades of the impeller 1 and the blades 5a is reduced, the generation of noise is suppressed, the strength margin is increased, and the reliability is increased. However, at a flow rate close to the surge, the flow passage cross-sectional area between the stationary blades 6 becomes relatively large, so that the efficiency of converting the kinetic energy of the fluid into pressure is significantly reduced. Therefore, as shown in FIG. 3, a blade 5b having a chord length and a thickness larger than that of the blade 5a is provided on the inner peripheral side of the stationary blade 6 as an actuator 7.
When further projecting into the diffuser flow path by the operation of, the flow path in this portion is pushed away to prevent the flow path cross-sectional area between the stationary blades 6 from becoming relatively large, and the kinetic energy of the fluid is reduced. It is possible to prevent a decrease in the efficiency of converting − into pressure.

Generally, during a low flow rate operation, the flow near the diffuser side wall 9 on the side plate side near the outlet of the impeller 1 is stagnant and lower in pressure than the flow near the diffuser side wall 10 on the core plate side, and The flow tends to flow in a direction close to the tangential direction of the impeller 1 and backflow is likely to occur. In the state shown in FIG. 3, the flow near the side wall 9 on the side plate side is blocked by the blades 5b, so that backflow is less likely to occur. Although the flow near the side wall 10 on the core plate side increases, the flow on the core plate side is guided by the blades 5a along the stationary blades 6, so that the kinetic energy is converted into pressure with high efficiency. If there is no movable blade 5a having a small chord length and height, a small flow rate operation can be performed by increasing the protrusion amount of the stationary blade 6 having a large chord length and thickness. In this case, however, the high stagnation pressure is high. A part of the flow near the side wall 10 on the side of the core plate having a is blocked. This reduces the efficiency with which kinetic energy is converted to pressure. The effect is further enhanced if the airfoil near the inlet of the blade 5b has a shape that approaches the tangential direction of the impeller 1. The blade 5b is housed in a groove 11 that is slightly wider than the contour of the blade 5b, and is configured to prevent the occurrence of loss due to a vortex in the space between the blade 5b and the groove 11.

FIG. 5 is an external view of the blade device 5. The blade 5a is formed integrally with the blade 5b and is supported by the annular plate 8.
Since it is sufficient to attach several actuators 7 to the annular plate 8, it becomes necessary to attach them to each blade device 5,
Therefore, the structure can be simplified. 6 to 8 are layout diagrams of the second, third and fourth embodiments of the stationary blade and the blade device, respectively. The feature of the embodiment of FIG. 6 is that the blades 5 inserted into the diffuser flow passage during the operation at a smaller flow rate than the first embodiment.
The point is that the chord length and thickness of b are further increased to improve the performance during small flow rate operation. The feature of the embodiment of FIGS. 7 and 8 is that the blades 5b are inserted into the diffuser flow passage during the small flow rate operation.
Has a wedge shape, and further improves performance during small flow rate operation. In the embodiment of FIGS. 6 to 8, it is possible to increase the thickness and chord length of the blade 5b to form a part of the side wall.

FIG. 9 is an external view of a fifth embodiment of the blade device, in which the blade profile of the blade 5a continuously and smoothly changes to the blade profile of the blade 5b. The feature of this embodiment is that the blade 5a
Is high in strength and high in reliability.

FIG. 10 is an external view of the sixth embodiment of the blade device, and shows the case where the blade shape of the blade 5a continuously and smoothly changes to the blade shape of the root of the blade 5b. The feature of this embodiment is that the change in the compressor characteristics due to the moving in and out of the movable blade 5 is extremely smooth.

11 and 12 are explanatory views of the operation of the seventh embodiment of the blade device. The second stationary blade 5d is fixed to the side wall 9 on the side plate side in the diffuser flow passage at the time of a large flow rate, and the blade 5b inserted into the diffuser flow passage at the time of a small flow rate operation is fixed to the side wall 10 on the core plate side. This is the case when it is installed in. In FIG. 11, the blade 5b is located outside the diffuser flow path and does not project into the diffuser flow path when the flow rate is large. In FIG. 12, the blade 5b projects into the diffuser flow path in a small flow rate operation state. The second stationary blade 5d and the blade 5b do not have to overlap in the circumferential direction. This embodiment has the advantage of facilitating the manufacture of the vanes 5b, but since a part of the flow near the side wall 10 on the side of the core plate having a high stagnation pressure is blocked, it is compared with the first embodiment. Performance is slightly reduced. 11 and 1
Also in the second embodiment, it is possible to increase the thickness and chord length of the blade 5b to form a part of the side wall 10 on the core plate side.

FIGS. 13 to 16 are explanatory views of the operation of the eighth embodiment of the blade device. Fig. 1 shows the operating conditions with the highest flow rate.
3, the blades 5a and 5b do not project at all in the diffuser flow path. In this state, only the stationary blade 6 exists in the diffuser flow path, so that the loss generated by the stationary blade 6 is small. Corresponding to the decrease in the flow rate, the blades 5a are made to project into the diffuser channel as shown in FIG. When the flow rate further decreases, the blades 5b are made to project into the diffuser passage as shown in FIG. FIG. 16 shows the case where the flow rate is reduced most, and the blade 5b fills the entire height in the diffuser flow path. In this embodiment, the highest performance can be expected although the mechanism is complicated. The blades 5a and 5b do not have to overlap in the circumferential direction. Also in the embodiment shown in FIGS. 13 to 16, the blade 5b can be made to be a part of the side wall 10 on the core plate side by increasing the thickness and chord length.

FIG. 17 is a layout view of a ninth embodiment of the stationary blade and the blade device, which includes a stationary blade 6a fixed on the side wall of the diffuser and blades 5a and 5b protruding into the diffuser flow path. It is an example configured. The feature of this embodiment is that the blades 5a and 5b are arranged not in the entire circumference but in only a part in the circumferential direction, and the movable part can be made small.

[0017]

According to the present invention, the compressor can be operated with high efficiency in a wide range from a large flow rate to a small flow rate.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of a centrifugal compressor of the present invention.

2 to 3 are explanatory views of the operation of the blade device.

FIG. 4 is a layout view of a stationary blade and a blade device.

FIG. 5 is an external view of a blade device.

FIG. 6 is a layout view of a second embodiment of the stationary blade and the blade device.

FIG. 7 is a layout view of a third embodiment of a stationary blade and a blade device.

FIG. 8 is a layout view of a fourth embodiment of a stationary blade and a blade device.

FIG. 9 is an external view of a fifth embodiment of the blade device.

FIG. 10 is an external view of a sixth embodiment of the blade device.

FIG. 11 is an operation explanatory view of the seventh embodiment of the blade device.

FIG. 12 is an operation explanatory view of the blade device.

13 to 16 are operation explanatory views of the blade device according to the eighth embodiment.

FIG. 17 is a layout view of a ninth embodiment of the stationary blade and the blade device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Impeller 2 ... Flow 3 ... Casing 4 ... Diffuser 5 ... Blade device 5a, 5b ... Blade 6,6a ... Stationary blade 7 ... Actuator 8 ... Annular plate 9 ... Side plate side diffuser side wall 10 ... Diffuser side wall on the core plate side 11 ... Groove 90 ... Flow rate detector 91 ... Flow meter 92 ... Actuator controller 93 ... Control device

Claims (17)

[Claims] 1. A centrifugal compressor provided with a diffuser in which stationary blades are arranged on the outer circumference of an impeller and a kinetic energy of fluid discharged from the impeller is converted into pressure by the action of the stationary blades. A blade device composed of a blade having a large chord length and a blade having a small chord length is arranged on the inner peripheral side of the blade, and this vane device defines a blade having a short chord length when the operation flow rate of the compressor is high. A centrifugal compressor characterized in that it is configured to project into the flow passage, and at least a blade having a large chord length is projected into the diffuser flow passage when the operating flow rate is small. 2. The centrifugal compressor according to claim 1, wherein the chord length of the blade of the blade device is changed stepwise. 3. The centrifugal compressor according to claim 1, wherein the chord length of the blades of the blade device is continuously changed. 4. The centrifugal compressor according to claim 2 or 3,
A centrifugal compressor characterized in that the blades of the blade device are movable in the same direction as the rotation axis of the impeller. 5. The centrifugal compressor according to claim 4, wherein the blade having a large chord length of the blade device is smaller than the chord length of the stationary blade. 6. The centrifugal compressor according to claim 4, characterized in that the chord length of the vanes of the vane device projecting into the diffuser flow passage is smaller than the chord length of the stationary vanes when the operating flow rate is low. Centrifugal compressor. 7. The centrifugal compressor according to claim 5, wherein
A centrifugal compressor in which a blade leading edge of a blade device is inclined downstream from a side plate side to a core plate side. 8. A first stationary blade is arranged on the outer periphery of the impeller,
In a compressor provided with a diffuser for converting kinetic energy of fluid discharged from an impeller into pressure by the action of a first stationary blade, a diffuser flow path on an inner peripheral side of the first stationary blade A second stationary blade having a height smaller than the height of the diffuser passage is disposed on one side wall, and a blade having a chord length larger than that of the second stationary blade is disposed on the other side wall. A vane device is arranged so that the vane device is outside the diffuser flow passage when the compressor operating flow rate is high, and the vane protrudes into the diffuser flow channel when the operating flow rate is low. A centrifugal compressor characterized by having a configuration. 9. The centrifugal compressor according to claim 8, wherein the front edge of the second stationary blade is inclined toward the downstream side from the side plate side to the core plate side. 10. A centrifugal compressor provided with a diffuser in which stationary blades are arranged on the outer circumference of an impeller and a kinetic energy of fluid discharged from the impeller is converted into pressure by the action of the stationary blades. A first vane device is arranged on one side wall of the diffuser flow path on the inner peripheral side of the vane, and a second vane having a chord length larger than that of the first vane device is arranged on the other side wall. A vane device is arranged, and the first vane device and the second vane device are arranged so that all the vanes are outside the diffuser flow path when the operating flow rate of the compressor is large, and the operating flow rate is reduced. The centrifugal blade characterized in that the blade of the first blade device is made to project into the diffuser flow path, and then the blade of the second blade device is made to project in the diffuser flow path. Compressor. 11. The centrifugal compressor according to claim 10, wherein the first
Centrifugal compressor characterized in that the blade leading edge of the blade device is inclined downstream from the side plate side to the core plate side. 12. A centrifugal compressor provided with a diffuser in which stationary blades are arranged on the outer circumference of an impeller, and the kinetic energy of fluid discharged from the impeller is converted into pressure by the action of the stationary blades. The diffuser flow passage between the blades and the diffuser flow passage on the inner peripheral side of the stationary blade are provided with a blade device composed of a blade having a large chord length and a blade having a small chord length. When the operating flow rate is high, a blade with a small chord length is projected into the diffuser flow path on the inner peripheral side of the stationary blade, and when the operating flow rate is low, at least a blade with a long chord length is placed between the stationary blades. A centrifugal compressor characterized in that it is configured to project into the diffuser flow path. 13. The centrifugal compressor according to claim 12, wherein
Centrifugal compressor characterized in that the blade leading edge of the blade device is inclined downstream from the side plate side to the core plate side. 14. The centrifugal compressor according to any one of claims 1 to 13, wherein any one of the stationary blade, the first stationary blade, and the blade device is arranged at different intervals. Machine. 15. The centrifugal compressor according to claim 1, wherein any one of the stationary blade, the first stationary blade, and the blade device has a different shape. 16. A centrifugal compressor provided with a diffuser in which stationary blades are arranged on the outer circumference of an impeller and a kinetic energy of fluid discharged from the impeller is converted into pressure by the action of the stationary blades. A vane device composed of vanes having different chord lengths in the height direction is arranged on the inner peripheral side of the vane, and this vane device diffuses a vane having a small chord length when the operation flow rate of the compressor is high. A centrifugal compressor having a structure in which a blade having at least a large chord length is projected into the diffuser channel when the blade is projected into the channel and the operation flow rate is small. 17. A centrifugal compressor provided with a diffuser in which stationary blades are arranged on the outer periphery of an impeller, and the kinetic energy of fluid discharged from the impeller is converted into pressure by the action of the stationary blades. A blade device composed of a blade having a large chord length and a blade having a small chord length is arranged on the inner peripheral side of the blade, and this vane device defines a blade having a short chord length when the operation flow rate of the compressor is high. A centrifugal compressor characterized in that it is provided with a control device for projecting into the diffuser flow path and projecting at least blades having a large chord length into the diffuser flow path when the operating flow rate is small.