WO2009157604A1

WO2009157604A1 - Two-stage centrifugal compressor

Info

Publication number: WO2009157604A1
Application number: PCT/KR2008/003739
Authority: WO
Inventors: Heonseok Lee
Original assignee: Kturbo, Inc.
Priority date: 2008-06-27
Filing date: 2008-06-27
Publication date: 2009-12-30

Abstract

The present invention relates to a two-stage centrifugal compressor that is improved in a conventional structure, without employing any variable structure, thereby ensuring a high efficiency and an enlarged operating range. The two-stage centrifugal compressor comprising: a one-stage compression part that adopts a diffuser adapted to provide an enlarged operating range; and a two-stage compression part that adopts a channel diffuser adapted to provide a high efficiency.

Description

Description TWO-STAGE CENTRIFUGAL COMPRESSOR

Technical Field

[1] The present invention relates to a two-stage centrifugal compressor that is improved in a conventional structure, without employing any variable structure, thereby ensuring a high efficiency and an enlarged operating range. Background Art

[2] Typically, industrial turbo air compressors employ two-stage or three-stage centrifugal compressors. A turbo compressor of 400 HP or more performs three-stage compression, and a turbo compressor of 1200 HP performs four-stage compression, so as to enhance their efficiency.

[3] However, the turbo compressors of 400 HP or less generally perform two-stage compression, because it is considered that their price is more important than their efficiency.

[4] When the two- stage compression is conducted, the air flowing speed is high such that the operating range is disadvantageously decreased, and thus, many efforts have been recently made to develop a centrifugal compressor having a high efficiency and a substantially enlarged operating range.

[5] The most important factor in determining the efficiency and operating range of the centrifugal compressor is an impeller. The impeller has been improved in the efficiency and operating range up to a substantially theoretical desirable limit value owing to the remarkable development of computational fluid dynamics. Therefore, the efficiency and operating range of the centrifugal compressor is determined depending upon a diffuser disposed at the rear end of the impeller.

[6] The diffusers of commercial centrifugal compressors is largely classified into the following three types: vaneless diffusers, airfoil diffusers and channel diffusers

[7] A variety of diffuser types are known in the art as shown in FIGS.l to 4.

[8] Since the vaneless diffuser has no wing, it has the largest operating range, but it obtains a lowest efficiency. Meanwhile, since the channel diffuser has a wedge-shaped wing to conduct rapid deceleration, the efficiency is highest, but it obtains a very small operating range.

[9] On the other hand, since the airfoil diffuser is a mixing type of the vaneless diffuser and the channel diffuser, it obtains an intermediate level of efficiency and operating range.

[10] Therefore, it is most desirable that the channel diffuser having a variable structure is adopted in the centrifugal compressor so as to enlarge the operating range. In this case, however, the two-stage centrifugal compressor of 400 HP or less becomes complicated in structure, which results in an increase in the production cost, thereby missing the competitiveness in the market. Disclosure of Invention

Technical Problem

[11] Accordingly, the present invention has been made in view of the above-mentioned problems occurring in the prior art, and it is an object of the present invention to provide a two- stage centrifugal compressor that is improved in a conventional structure, without employing any variable structure, thereby ensuring a high efficiency and an enlarged operating range. Technical Solution

[12] To achieve the above object, according to the present invention, there is provided a two-stage centrifugal compressor comprising: a one-stage compression part that adopts a diffuser adapted to provide an enlarged operating range; and a two-stage compression part that adopts a channel diffuser adapted to provide a high efficiency.

Advantageous Effects

[13] As described above, the two-stage centrifugal compressor according to the present invention adopts the channel diffuser in the two-stage compression part, thereby obtaining a high efficiency, without any decreasing in the operating range.

[14] For instance, in case of the two-stage centrifugal compressor of 200 HP and 5.0barG where the airfoil diffuser is adopted in the one-stage compression part and the channel diffuser is adopted in the two-stage compression part, the two-stage compression part has a higher efficiency by 5% than the one-stage compression part, and the operating range of about 40% is enlarged in the two-stage centrifugal compressor. Brief Description of the Drawings

[15] FIGS.1 to 4 show various types of diffusers as used in conventional practices.

[16] FIG.5 shows a model of a two-stage centrifugal compressor according to the present invention. Mode for the Invention

[17] As shown in FIG.5, a two-stage centrifugal compressor according to the present invention adopts an airfoil diffuser 11 in a one-stage compression part 1 (including an impeller and a diffuser) so as to obtain an intermediate level of operating range and efficiency value and adopts a channel diffuser 12 in a two-stage compression part 2 so as to obtain a high efficiency value.

[18] Generally, the reason why the airfoil diffuser 11 is adopted in the one-stage compression part 1 is that since a one-stage impeller is limited in the operating range due to a high entrance speed, the adoption of the vaneless diffuser causing an excessive operating range is not desirable, and the adoption of the airfoil diffuser 11 providing the high efficiency value is desirable.

[19] On the other hand, when the channel diffuser 12 is adopted in the two-stage compression part 2, the operating range of the two-stage compression part 2 is reduced thereby failing to accomplish their object, and so as to avoid the problem, thus, all kinds of multi-stage turbo air compressors make use of the airfoil diffuser in all of the one-stage and two-stage compression parts.

[20] However, the operating conditions (such as entrance correction flow rate and correction revolution) of the two-stage compression part stay at any one value, without being almost varied in the entire area, which is checked out through one-dimensional calculation and performance tests.

[21] That is, when the diffuser is operated in a predetermined final exit pressure, the flow rate is decreased such that the revolution is reduced.

[22] If the flow rate is greatly reduced, the revolution is also decreased in the same manner, and in this case, the pressure of the one-stage compression part becomes low.

[23] Therefore, the volume flow rate at the entrance of the two-stage compression part is maintained without any decrement, such that according to the two- stage compression part having the channel diffuser providing high pressure variations even in the small decrement of the volume flow rate, the two-stage compression part generates higher pressure than the one-stage compression part, thereby permitting a final discharge pressure to be maintained.

[24] In order to realize the conditions, of course, a precise design should be needed.

[25] As a result, it is appreciated that the two-stage compression part does not need an enlarged operating range.

[26] That is, the channel diffuser causing a small operating range is used in the two-stage compression part, which has no effect on the entire operating range.

[27] Therefore, in the two-stage centrifugal compressor according to the present invention, the diffuser providing the enlarged operating range is adopted in the one- stage compression part, and the channel diffuser providing the high operating efficiency is adopted in the two-stage compression part, even though the operating range of the channel diffuser is small.

Claims

[1] A two-stage centrifugal compressor comprising: a one-stage compression part 1 that adopts a diffuser adapted to provide an enlarged operating range; and a two-stage compression part 2 that adopts a channel diffuser 12 adapted to provide a high efficiency. [2] The two-stage centrifugal compressor as defined in claim 1, wherein the diffuser of the one-stage compression part is an airfoil diffuser 11.