RU2330994C2 - Centrifugal compressor - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention relates to production of compressors and can be used in engines of flying vehicles, marine and ground transport means, as well as in power plants to increase reliability of centrifugal compressor by eliminating destructive processes in its impeller. The centrifugal compressor incorporates a closed-type impeller, the impeller casing, and diffuser. The impeller casing is arranged above its covering plate with a gap communicating with the compressor flow-through section via the slot between the covering plate outer edge and the impeller casing. The impeller covering plate is furnished with a labyrinth seal arranged along the inner edge at the rear side relative to the flow-through section. Novelty of the compressor consists in that it is furnished with a cooling air circular chamber formed on the impeller casing and communicating with the high-pressure cooling air feed line. Also, the impeller casing has holes communicating the circular chamber space with the gap formed between the impeller casing and the covering plate.

EFFECT: higher reliability centrifugal compressor.

1 dwg

Description

The invention relates to compressor engineering and can be used in aircraft engines, marine and land vehicles, as well as in power plants.

A known centrifugal compressor comprising an impeller, an impeller housing, a diffuser, a cooling air chamber. The chamber is located behind the impeller and is in communication with the flow part of the compressor directly at the outlet of the impeller. It is also connected to the cooling air supply pipe (US Pat. No. 6,035,627, class F02C 7/18, publ. 14.03.2000). During the operation of a centrifugal compressor, two air flows enter the cooling air inlet: hot directly from the impeller and cold from the cooling air pipe. Mixing the flows at the inlet allows the chamber to obtain a temperature of air blowing around the impeller lower than the temperature of the air at the outlet of the impeller. Thus, cooling and temperature equalization in the metal of the impeller hub are ensured. A disadvantage of a centrifugal compressor is its low efficiency, since it uses a half-open impeller. Semi-open impellers are characterized by end losses associated with air flow. In addition, a compressor with a half-impeller type is difficult to use due to the need to maintain small gaps between the impeller and its casing.

These disadvantages are eliminated in centrifugal compressors by using closed impellers. Such impellers consist of two structural elements passing one into another: the main disk with rotor blades and a cover disk (Kholshchevnikov K.V. et al. Theory and design of aircraft blade machines. - M.: Mechanical Engineering, 1986, p.184-185 ; USSR AS No. 1168748, class F04D 29/58, publ. 07/23/1985; USSR AS No. 1633161, class F04D 29/28, publ. 03/07/1991; US patent No. 2305226, class. 230-130, publ. 15.12.1942). Closed impeller provides minimal end losses and highest efficiency values.

Known centrifugal compressor, selected as a prototype. The design of the centrifugal compressor includes a closed impeller, an impeller housing and a diffuser. The impeller cover disk is made with a labyrinth seal along the inner edge from the back side relative to the flow part of the wheel. The impeller housing, which also serves as the seal housing, is mounted above the cover disk to form a gap. The gap communicates with the compressor running part through a slot located between the outer edge of the cover disk and the impeller casing (AS USSR No. 591619, class F04D 29/28, published 05.02.1978). The disadvantage of a centrifugal compressor is its lack of reliability. Under operating conditions, the impeller quickly fails: cracks form at the points of transition of the blades to the cover disk, leading to the destruction of the wheel.

The objective of the invention is to increase the reliability of a centrifugal compressor by eliminating destructive processes in its impeller.

The exclusion of destructive processes in the impeller is achieved by the fact that in a centrifugal compressor including a closed impeller, the cover disk of which is made with a labyrinth seal along the inner edge from the back side relative to the flow part, the diffuser and the impeller housing mounted above the cover disk with a gap communicated with the compressor running part through a slot located between the outer edge of the cover disk and the impeller housing according to the invention on the impeller housing It shapes the annular chamber cooling air, having a connection with a high-pressure cooling air feed conduit, wherein the impeller housing is formed with holes connecting the cavity of the cooling air of the annular chamber with a gap formed between the impeller casing and the cover plate.

The study of destructive processes that occur in the impeller during operation of a centrifugal compressor - a prototype, made it possible to establish their cause. It consists in the difference in the heating of the cover disk and the blades of the main disk. For example, this difference when using a compressor in a gas turbine aircraft engine is about 100 ° C: the blades along the working stream have a temperature from 300 ° C to 350 ° C, and the cover disc is heated in the range from 400 ° C to 450 ° C. The temperature difference at the “blade – cover disk” boundary causes significant temperature stresses in the metal of this region. The reason is that the cover disk heats up additionally due to friction on its surface of the air flow. In this case, the air flow flows into the gap from the compressor flow path through the gap between the outer edge of the cover disk and the impeller housing, and then seeps through the labyrinth to the entrance to the impeller.

The presence in the new centrifugal compressor of an annular chamber of cooling air formed on the impeller housing and in communication with the high-pressure cooling air supply pipe, as well as an impeller housing with openings connecting the cavity of the annular chamber of cooling air with a gap formed between the impeller housing and cover disk, allows blowing the cover disk with cold air. This eliminates the ingress of hot air from the flow of the compressor. As a result, the temperature difference at the “blade – cover disk” boundary and, consequently, the temperature stresses in the metal are significantly reduced.

The invention is illustrated in the drawing, which shows a centrifugal compressor of a gas turbine engine, its longitudinal section.

The centrifugal compressor comprises an outer casing 1, an impeller 2 of a closed type, an impeller casing 3, a diffuser 4, a straightening device 5. The cover disk 6 of the impeller 2 has a labyrinth seal 7 on the inner edge from the rear side relative to the flow part of the impeller 7. the wheel, which also functions as a seal housing, is mounted above the cover disk 6 with the formation of a gap 8. Between the outer edge of the cover disk 6 and the impeller housing 3 there is a slot 9 through which the gap 8 is communicated with the proto the main part of the centrifugal compressor directly behind the exit of the impeller 2. An annular chamber 10 of cooling air is formed on the housing 3 of the impeller: the housing 3 performs the function of one of the walls of the annular chamber 10, the function of the other wall of the annular chamber 10 is carried out by a part of the diffuser housing 4. In the housing 3 the impeller has openings 11 that connect the cavity of the annular chamber 10 of cooling air with a gap 8. Holes 11 are located opposite the middle zone of the cover disk 6 relative to its outer and inner th edge. This arrangement of holes is the most rational.

The annular chamber 10 of cooling air is in communication with the pipe 12 for supplying cooling air of high pressure.

During operation of the centrifugal compressor, the cooling air enters through the pipe 12 for supplying high pressure cooling air to the annular chamber 10 of cooling air. Through holes 11 it enters into the gap 8 and, blowing the cover disk 6, under the influence of the pressure drop and centrifugal forces is partially diverted through the slot 9 into the flowing part behind the impeller 2, and partially under the influence of the pressure difference through the labyrinth seal seeps to the entrance to the impeller 2.

Thus, the temperature of the cover disk approaches the temperature of the blades of the main disk of the impeller. As a result of this, the temperature stresses in the metal at the “blade – cover disk” boundary are reduced. With large heatings in the impeller, the new centrifugal compressor design gives the best results. Reducing the risk of impeller failure, increasing its resource contribute to increasing the reliability of a centrifugal compressor.

Claims (1)

A centrifugal compressor, including a closed impeller, the cover disk of which is made with a labyrinth seal along the inner edge from the back side relative to the flow part, a diffuser and the impeller housing mounted above the cover disk with a gap communicated with the compressor flow part through a slot located between the outer the edge of the cover disk and the impeller housing, characterized in that an annular cooling air chamber is formed on the impeller housing, which has a message from the pipes wire supplying high-pressure cooling air, wherein the impeller housing is formed with holes connecting the cavity of the cooling air of the annular chamber with a gap formed between the impeller casing and the cover plate.