JPH109196A - Diffuser for centrifugal compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of peel-off flow and simplify a structure by controlling a rate of gas flowed into a diffuser according to operation conditions, and improving matching of a centrifugal impeller and the diffuser. SOLUTION: A centrifugal compressor has a centrifugal impeller 1 and a diffuser 2 provided with partition walls for dividing its inner space and forming throat portions. With such a setup, among the partition walls of the diffuser 2, the operation walls to which heat is applied are bent due to temperature variation of gas at an inlet of the diffuser 2 while the operation condition of the centrifugal compressor is shifted between low speed rotation and high speed rated rotation. The inlet of a diffuser throat 21 is increased at a low temperature and decreased at a high temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a diffuser of a compressor, and more particularly to the improvement of the performance of a diffuser of a centrifugal compressor.

[0002]

2. Description of the Related Art As shown in FIGS. 7 and 8, a centrifugal compressor includes a rotating centrifugal impeller 1 (impeller), a non-rotating diffuser 2, and a scroll (volute or spiral casing) 3. A disc 5 for mounting the centrifugal impeller 1 is provided on the hub 4, a shroud 6 is provided at a position facing the disc 5, and a connection space and a connection space are provided between the centrifugal impeller 1 and the diffuser 2. Is provided.

[0003]

However, in the case of a centrifugal compressor, the compression effect of the centrifugal impeller on the gas at the time of starting or at a low speed is reduced, so that the flow rate flowing into the diffuser is limited to an appropriate amount. Exceeding this will result in poor matching between the impeller and the diffuser, making it difficult to secure a stable operating area.
This phenomenon tends to be more pronounced at higher pressure ratios.

[0004] The present invention has been made in view of the above circumstances, and aims to achieve the following objects. The ability to control the amount of gas flowing into the diffuser according to the state of rotation of the centrifugal impeller. Improve the matching between the centrifugal impeller and the diffuser and extend the stable operating range. The structure is simple and does not burden other structures. Costs should be kept low.

[0005]

A centrifugal compressor having a centrifugal impeller and a diffuser provided with a partition wall which divides an internal space to form a throat portion, wherein the partition wall of the diffuser is a centrifugal impeller. Side and a fixed wall in a fixed state. The thermal operation wall is provided with a function in which the downstream side is fixed to the diffuser side wall and the upstream side is curved based on a temperature change. As the thermal working wall, a bimetal in which a high thermal expansion material and a low thermal expansion material having different thermal expansion rates are bonded, or a shape memory alloy having a high temperature transformation phase and a low temperature transformation phase is adopted. In the operation state of the low-speed rotation and the high-speed rated rotation of the centrifugal compressor, the heat working wall is bent and deformed by the temperature change of the gas temperature at the diffuser inlet, and expands the inlet of the diffuser throat portion at a low temperature,
Reduce inlet at high temperature.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described.
A description will be given based on FIGS. 1 to 6. 1 to 6, reference numeral 1 denotes a centrifugal impeller, reference numeral 2 denotes a diffuser,
Reference numeral 3 denotes a scroll, 4 denotes a hub, and 5 denotes a disk.

As shown in FIGS. 1, 3 and 4, a throat portion 21 is formed in the diffuser 2 by a partition wall 20, and the partition wall 20 is thermally actuated by a small gap 22 with a fixed wall 23. The heat operating wall 24 is disposed on the upstream side near the entrance from the centrifugal impeller 1, and the fixed wall 23 is disposed on the downstream side.

The small gap 22 is inclined in a direction from the surface of the partition wall 20 toward the inside, in a direction opposite to the gas flow inside the diffuser 2 from the normal direction of the surface. The fixed wall 23 is fixed to the side wall 2 a of the diffuser 2, and the heat operation wall 24 has an end on the fixed wall 23 side fixed to the side wall 2 a of the diffuser 2. Further, at the upstream end of the heat operation wall 24, clearances 25, 25 are formed between the heat operation wall 24 and the side wall 2a of the diffuser 2 so as to be freely bendable.

As shown in FIG. 5, the thermal operation wall 24 is made of, for example, a bimetal in which two metal plates are laminated in the thickness direction.
Are arranged, and the plate material 27 having a high coefficient of thermal expansion is set on the abdominal surface side.

In the centrifugal compressor having the above configuration, the centrifugal impeller 1 is driven to rotate as indicated by an arrow A,
The gas introduced into the centrifugal impeller 1 is compressed mainly by centrifugal action during deceleration when passing between the blades, and is sent to the diffuser 2 via the vaneless portion 7.
Here, when the centrifugal impeller 1 is rotating at a low speed, such as at the time of startup, the gas flowing into the diffuser 2 is in a low temperature state. 6A, that is, a state where the throat interval SL is widened.

When the number of revolutions of the centrifugal impeller 1 increases, and when the centrifugal impeller 1 rotates at the rated high speed, the temperature of the gas flowing into the diffuser 2 increases, and the plate material 27 having a high thermal expansion coefficient becomes a low thermal expansion coefficient. As shown in FIG.
As shown in FIG. 6B and FIG. 6B, the throat interval SH of the throat portion 21 is reduced as a result.

As described above, since the heat operating wall 24 is deformed in response to the change in the rotation speed of the centrifugal impeller 1, the gas is supplied to the throat portion 21 with the throat interval SL expanded at the time of low speed rotation. It is possible to expand the stable operation range even at the time of low compression. In addition, the curvature of the heat working wall 24 becomes large at the time of low-speed rotation where the flow rate of the gas is low, and the heat working wall 24 becomes large at the time of high-speed rotation of the gas at a high speed.
, The occurrence of a separation flow inside the throat portion 21 can be suppressed.

[Other Embodiments] The above-mentioned thermal working wall 24 can be made of a shape memory alloy. In this case, it is sufficient to have a high-temperature transformation phase and a low-temperature transformation phase so that the throat intervals SL and SH can be set at high and low temperatures according to the bimetal.

[0014]

According to the diffuser for a centrifugal compressor of the present invention, the following excellent effects can be obtained. (1) Since the partition wall of the diffuser is deformed according to the rotation state of the centrifugal impeller, the amount of gas flowing into the diffuser can be controlled according to the rotation state. (2) Since the partition wall of the diffuser is deformed in response to the change in the flow velocity, the matching between the centrifugal impeller and the diffuser can be improved, and the stable operation range can be expanded. (3) Since the configuration is such that the partition wall of the diffuser is deformed in response to a change in temperature, the structure is simple and the above effects can be obtained without imposing a load on other structures. (4) The structure is simple and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a front view of a first embodiment of a diffuser structure of a centrifugal compressor according to the present invention, with a part of description omitted.

FIG. 2 is a perspective view showing the centrifugal impeller of FIG.

FIG. 3 is an enlarged view of the diffuser of FIG. 1;

FIG. 4 is a side view showing the partition wall of FIG. 1;

FIG. 5 is a front view showing a thermal operation state of the thermal operation wall in the partition wall of FIG. 1;

FIG. 6 is an operation diagram showing a change of a throat portion by the thermal operation wall of FIG. 5;

FIG. 7 is a plan cross-sectional view of a conventional example of a centrifugal compressor, in which some descriptions are omitted.

FIG. 8 is a front cross-sectional view of a conventional example of a centrifugal compressor, in which some descriptions are omitted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Centrifugal impeller 2 ... Diffuser 2a ... Side wall 7 ... Vaneless part 20 ... Partition wall 21 ... Throat part 22 ... Small gap 23 ... Fixed wall 24 ... Thermal working wall 25 ... Clearance 26 ... Low thermal expansion coefficient plate material 27 ... High thermal expansion Rate board material

Claims (5)

[Claims] 1. A centrifugal compressor having a centrifugal impeller (1) and a diffuser (2) provided with a partition wall (20) for dividing an internal space to form a throat portion (21). A diffuser for a centrifugal compressor, wherein a partition wall changes between an expanded low-temperature state and a reduced high-temperature state at an inlet portion of the throat section (21) according to a change in gas temperature at a diffuser inlet. 2. The partition wall (20) of the diffuser (2).
The centrifugal compressor according to claim 1, characterized in that the centrifugal compressor is divided into a part serving as a heat working wall (24) on the side of the centrifugal impeller (1) and another part serving as a fixed wall (23). Diffuser. 3. The heat-operating wall (24) has a downstream side fixed to the diffuser side wall (2a) and an upstream side provided with a function of curving based on a temperature change. 3. The diffuser of the centrifugal compressor according to 2. 4. A bimetal in which a plate (27) having a high coefficient of thermal expansion having a different coefficient of thermal expansion and a plate (26) having a coefficient of low thermal expansion are laminated in the thickness direction as the thermal working wall (24). The diffuser for a centrifugal compressor according to any one of claims 1 to 3, wherein: 5. The diffuser for a centrifugal compressor according to claim 1, wherein a shape-memory alloy having a high-temperature transformation phase and a low-temperature transformation phase is employed as the thermal working wall (24). .