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Research Papers: Flows in Complex Systems

Improvement of the Performance of a Centrifugal Compressor by Modifying the Volute Inlet

[+] Author and Article Information
Semi Kim

Department of Mechanical Engineering, POSTECH, San 31, Hyoja-dong, Nam-gu, Pohang 790-784, Koreassemlove@postech.ac.kr

Junyoung Park

 KIMM, Sinseongno, Yuseong-gu, Daejeon 305-343, Koreajypark@kimm.re.kr

Kukyoung Ahn

 KIMM, Sinseongno, Yuseong-gu, Daejeon 305-343, Koreakyahn@kimm.re.kr

Jehyun Baek1

Department of Mechanical Engineering, POSTECH, San 31, Hyoja-dong, Nam-gu, Pohang 790-784, Koreajhbaek@postech.ac.kr

1

Corresponding author.

J. Fluids Eng 132(9), 091101 (Sep 03, 2010) (7 pages) doi:10.1115/1.4001972 History: Received October 25, 2009; Revised June 09, 2010; Published September 03, 2010; Online September 03, 2010

In centrifugal compressors, the diffuser and the volute have strong influences on the flow discharged from the impeller and thus also on the performance. In particular, a key parameter is the radial velocity at the volute inlet; it determines the swirl velocity, which is dissipated as a loss, i.e., it results in performance degradation. With the aim of reducing the swirl loss, a new type of volute with a modified inlet height was tested in this study. The volute inlet height was modified to 6 mm and 7 mm from the original height of 5 mm. The reliability of our computations was tested by comparison of the results of a model with this original height with experimental data. Flow analyses were conducted not only at the design mass flow rate but also at lower and higher mass flow rates. A higher total-to-total efficiency was obtained as a result of the linear increases of the volute inlet height from the diffuser outlet to 6 mm and 7 mm. Our detailed investigation of the simulated flow fields shows that the flow characteristics for a volute inlet height of 6 mm are better than those for a volute inlet height of 5 mm. These results clearly show that a greater volute inlet height assists in pressure recovery and reduces swirl loss in the volute. However, the volute inlet height of 7 mm results in larger hub separation and more energy loss, and thus in inferior performance. Therefore, the hub separation and the radial velocity at the volute inlet strongly influence the performance.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Geometrical configuration and parameters of the compressor

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Figure 2

Full 2D view of the compressor

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Figure 3

Detailed surface grid of the impeller and cross-sectional grid of the volute

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Figure 5

The experimental setup

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Figure 6

Total pressure ratios for the original model at 35,000 rpm and 40,000 rpm

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Figure 7

Schematic diagrams of the modified volute configurations

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Figure 8

Velocity distributions in four cross sections of the volute

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Figure 9

Distributions of the pressure recovery coefficients for the four cross sections of the volute

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Figure 10

Distributions of the total pressure loss coefficients for the four cross sections of the volute

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Figure 11

Radial velocity distributions from hub to shroud at the volute inlet

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Figure 12

Circumferential velocity distributions from hub to shroud at the volute inlet

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Figure 13

Static pressure distributions from hub to shroud at the volute inlet

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Figure 14

Static pressure distributions from the diffuser outlet to the volute

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Figure 15

Circumferential distributions of the flow angle for various span locations: (a) near hub (0.1 span), (b) at midspan (0.5 span), and (c) near shroud (0.9 span)

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