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Research Papers

Experimental and Numerical Investigation of the Flow Inside the Return Channel of a Centrifugal Process Compressor

[+] Author and Article Information
C. Rube

Institute of Jet Propulsion and Turbomachinery,
RWTH Aachen University,
Templergraben 55,
Aachen 52062, Germany
e-mail: rube@ist.rwth-aachen.de

T. Rossbach, M. Wedeking, D. R. Grates, P. Jeschke

Institute of Jet Propulsion and Turbomachinery,
RWTH Aachen University,
Templergraben 55,
Aachen 52062, Germany

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received January 29, 2016; final manuscript received February 25, 2016; published online April 26, 2016. Editor: Kenneth C. Hall.

J. Turbomach 138(10), 101006 (Apr 26, 2016) (10 pages) Paper No: TURBO-16-1025; doi: 10.1115/1.4032905 History: Received January 29, 2016; Revised February 25, 2016

This paper presents the first detailed experimental performance data for a new centrifugal process compressor test rig. Additional numerical simulations supported by extensive pressure measurements at various positions allow an analysis of the operational and loss behavior of the entire stage and its components. The stage investigated is a high flow rate stage of a single-shaft, multistage compressor for industrial applications and consists of a shrouded impeller, a vaneless diffuser, a U-bend, and an adjoining vaned return channel. Large channel heights due to high flow rates induce the formation of highly three-dimensional flow phenomena and thus enlarge the losses due to secondary flows. An accurate prediction of this loss behavior by means of numerical investigations is challenging. The published experimental data offer the opportunity to validate the used numerical methods at discrete measurement planes, which strengthens confidence in the numerical predictions. CFD simulations of the stage are initially validated with global performance data and extensive static pressure measurements in the vaneless diffuser. The comparison of the pressure rise and an estimation of the loss behavior inside the vaneless diffuser provide the basis for a numerical investigation of the flow phenomena in the U-bend and the vaned return channel. The flow acceleration in the U-bend is further assessed via the measured two-dimensional pressure field on the hub wall. The upstream potential field of the return channel vanes allows an evaluation of the resulting flow angle. Measurements within the return channel provide information about the deceleration and turning of the flow. In combination with the numerical simulations, loss mechanisms can be identified and are presented in detail in this paper.

Copyright © 2016 by ASME
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References

Figures

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Fig. 3

Normalized stage performance at design speed

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Fig. 2

CFD model and detailed view on the mesh resolution at the LE of impeller and return vane

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Fig. 8

Normalized static pressure distribution along the hub of the diffuser and the U-bend at design point (DP)

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Fig. 1

Cross-sectional view of the compressor stage

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Fig. 4

Normalized polytropic total-to-total efficiency and efficiency drop caused by the return system

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Fig. 5

Normalized static pressure rise at the diffuser hub at design conditions

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Fig. 6

Normalized static pressure rise at the diffuser shroud at design conditions

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Fig. 7

Position of static pressure taps on the hub of the U-bend

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Fig. 9

Circumferential pressure distribution in plane 425 on the hub of the U-bend at DP

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Fig. 10

Circumferential pressure distribution in plane 450 on the hub of the U-bend at DP

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Fig. 11

Circumferential pressure distribution in plane 475 on the hub of the U-bend at DP

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Fig. 15

Hub-side stream traces in the return channel passage (near stall) and the location of measurement plane 510 and plane 590

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Fig. 16

Normalized static pressure distribution in plane 510 (see Fig. 15) at DP

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Fig. 17

Normalized static pressure distribution in plane 590 (blue line in Fig. 15) at DP

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Fig. 18

Normalized Mach number contour in plane 510 (red line in Fig. 15) at DP

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Fig. 19

Normalized Mach number contour in plane 590 (see Fig. 15) at DP

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Fig. 20

Normalized Mach number contour in plane 590 (see Fig. 15) at near stall

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Fig. 21

Normalized static pressure distribution in plane 590 (see Fig. 15) near stall

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Fig. 22

Normalized circumferential secondary velocities in plane 590 (see Fig. 15) near stall

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Fig. 23

Normalized spanwise flow angle in plane 590 (see Fig. 15) near stall

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Fig. 12

Spanwise profiles of normalized Mach number for planes 425, 450, and 475 at DP

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Fig. 13

Spanwise profiles of normalized total pressure for planes 425, 450, and 475 at DP

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Fig. 14

Spanwise profiles of the flow angle for planes 425, 450, and 475 at DP

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