JPS62118100A - Variable diffuser for centrifugal compressor - Google Patents

Abstract

PURPOSE:To improve performance by forming a pressure chamber on the back part of a diaphragm provided on the contact part of the wall surface of a diffuser passage with a diffuser vane and making said diaphragm swell out toward said vane, to remove a gap toward said vane. CONSTITUTION:A diaphragm 11 made of an elastic material having a small friction coefficient such as a metal film, is provided on the contact part of the wall face back plate 5 of a diffuser passage 3 with a diffuser vane 6. A pressure chamber 12 is formed on the back side of the diaphragm 11, and pressure in a scroll part 4 is introduced into this pressure chamber 12 via a pressure introducing passage 13 provided through the back plate 5. Thereby, the diaphragm 11 is swelled out elastically pressing the diffuser vane 6 and, therefore, a gap 14a between the vane 6 and the diaphragm 11, i.e., the back plate 5, is rendered zero, while also rendering a gap 14b between the diffuser vane 6 and a casing 1 close to zero. As a result, the leakage of gaseous body from a gap can be prevented, improving performance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a variable diffuser used for capacity control of a centrifugal compressor.

[Prior art]

A variable diffuser for a centrifugal compressor is, for example, disclosed in Japanese Patent Application Laid-open No. 1983-
As disclosed in Japanese Patent No. 10799 and the like, the diffuser vane is disposed in the diffuser passage so as to be rotatable and is operated by a movable mechanism.

By the way, from a performance standpoint, ideally there should be no gap between the diffuser vane and the wall of the diffuser passage, but in reality, if you try to eliminate the gap, the diffuser vane may dig into the wall or come into strong pressure contact when rotating. Friction may increase, and so on.

There is a problem in that it becomes difficult to drive the fuser vane.

To explain a specific example with reference to FIG. 2, an impeller 22 is disposed in the center of the casing 21, and a scroll portion 24 is provided on the outer periphery of the impeller 22 via an annular diffuser passage 23. These diffuser passages 2
3 and the scroll portion 24 are formed by the casing 21 and a back plate 25 provided opposite to the casing 21. Further, a diffuser vane 26 is disposed in the diffuser passage 23 so as to be rotatable, thereby forming a variable diffuser 27. The diffuser vane 26
is fixed to one end of a support shaft 29 that is rotatably supported by the casing 21 via a pair of bearing bushes 28, and a rotating lever 30 is fixed to the other end of the support shaft 29, and is connected to an operating mechanism (not shown). has been done. By rotating the diffuser vane 26 via the rotation lever 3.0 and the support shaft 29 using the operating mechanism, the throat width is changed, thereby controlling the capacity.

In such a variable diffuser 27, between the diffuser vane 26 and the casing 21, in order to reduce the frictional resistance when operating the diffuser vane 26,
Another problem is that gaps 31a and 31b must be provided between the diffuser vane 26 and the back plate 25, respectively.

[Purpose of the invention]

The present invention has been made to solve the above conventional problems, and improves performance by eliminating the gap between the diffuser vane and the wall surface of the diffuser passage without interfering with the drive of the diffuser vane. It is an object of the present invention to provide a variable diffuser for a centrifugal compressor.

[Structure of the invention]

A variable diffuser for a centrifugal compressor according to the present invention is a variable diffuser for a centrifugal compressor in which a diffuser vane is rotatably disposed in a diffuser passage extending from an impeller to a scroll part, in which a contact portion of a wall surface of the diffuser passage with the diffuser vane is provided. A diaphragm is disposed on the diaphragm, and a pressure chamber is formed on the back side of the diaphragm. A pressure introduction section is provided to introduce the pressure of the scroll section into this pressure chamber, and the velocity energy at the outer periphery of the impeller is converted into pressure energy, resulting in high pressure. Using the pressure of the scroll part,
This is characterized in that the diaphragm bulges toward the diffuser vane to eliminate the gap between the diaphragm and the diffuser vane.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

An impeller 2 is disposed in the center of the casing 1, and a scroll portion 4 is provided around the outer periphery of the impeller 2 via an annular diffuser passage 3. One side of the diffuser passage 3 and the scroll portion 4 is partitioned by the casing 1, and the other side is partitioned by a back plate 5 which is disposed opposite to the casing 1 and integrally connected at the outer periphery. A diffuser vane 6 is rotatably disposed in the diffuser passage 3, thereby forming a variable diffuser IO.

The diffuser vane 6 is attached to one end of a support shaft 8 rotatably supported by the casing 1 via a pair of bearing bushes 7, so that the diffuser vane 6 can swing slightly in a direction perpendicular to its axis, but cannot rotate relative to it. is combined with A rotating lever 9 is fixed to the other end of the support shaft 8, and is connected to an operating mechanism (not shown).

Further, a diaphragm 11 made of a material with high elasticity and a small coefficient of friction, such as a metal film, is provided at the contact portion of the bank plate 5 with the diffuser vane 6, and a pressure chamber 12 is formed on the back side of the diaphragm 11. There is. This pressure chamber 1
The pressure of the scroll portion 4 is introduced into the scroll portion 2 through a pressure introduction path 13 formed in the back plate 5.

In the above configuration, the gas sucked in from the center of the casing 1 by the rotation of the impeller 2 is accelerated toward the outer periphery of the impeller 2, flows into the scroll portion 4 through the diffuser passage 3, and flows into the scroll portion 4 (7) 19. The gas that has been accelerated and given velocity energy is converted into pressure energy in the scroll section 4. Further, when the rotation lever 9 is rotated by an operation mechanism (not shown), the diffuser vane 6 is rotated via the support shaft 8, and the throat width is changed, thereby controlling the capacity.

Since the pressure of the scroll portion 4 is introduced into the pressure chamber 12 via the pressure introduction path 13, the diaphragm 11 bulges toward the diffuser passage 3 side, and the diffuser vane 6
To elastically press the gap 14a between the diffuser vane 6 and the diaphragm 11, that is, the back plate 5
When becomes zero, the gap 14b between the diffuser vane 6 and the casing 1 also becomes close to zero, which eliminates gas leakage from these gaps and improves performance. Furthermore, since the joint between the diffuser vane 6 and the support shaft 8 is made swingable, the diffuser vane 6 moves following the movement of the surface of the diaphragm 11, thereby improving the tightness between the diaphragm 11 and the diffuser vane 6. This makes it possible to further eliminate the gap 14a.

〔Effect of the invention〕

According to the variable diffuser for a centrifugal compressor of the present invention, as described above, the diaphragm is disposed at the contact portion of the wall surface of the diffuser passage with the diffuser vane, and a pressure chamber is formed on the back side of the diaphragm. Since the structure is such that the pressure of the scroll section is introduced through the introduction path,
The pressure of the scroll portion can be used to bulge the diaphragm toward the diffuser vane. This makes it possible to eliminate the gap between the diffuser vane and the diffuser vane, resulting in a significant improvement in performance.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of one embodiment of the present invention, and FIG. 2 is a vertical cross-sectional view of a conventional example. 1 is a casing, 2 is an impeller, 3 is a diffuser passage, 4 is a scroll portion, 5 is a bank plate, 6 is a diffuser vane, 11 is a diaphragm, 12 is a pressure chamber, 1
3 is a pressure introduction path. Figure 31 Figure 2

Claims (1)

[Claims] 1. In a variable diffuser for a centrifugal compressor in which a diffuser vane is disposed rotatably in the diffuser passage from the impeller to the scroll part, a diaphragm is disposed at the contact part with the diffuser vane on the wall surface of the diffuser passage, and a diaphragm is disposed on the back side of the diffuser vane. A variable diffuser for a centrifugal compressor, characterized in that a pressure chamber is formed in the pressure chamber, and a pressure introduction path is provided for introducing the pressure of a scroll portion into the pressure chamber.