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Research Papers

Unsteady Acoustic Forcing on an Impeller Due to Coupled Blade Row Interactions

[+] Author and Article Information
Simon K. Richards1

 General Electric Global Research, Niskayuna, NY, 12309

Kishore Ramakrishnan2

 General Electric Global Research, Niskayuna, NY, 12309ramakris@ge.com

Chingwei M. Shieh3

 General Electric Global Research, Niskayuna, NY, 12309

François Moyroud, Alain Picavet

General Electric Oil and Gas,  Thermodyn SAS, Le Creusot, France, 71203

Valeria Ballarini, Vittorio Michelassi

General Electric Oil and Gas,  Nuovo Pignone, Florence, Italy, 50127

1

Currently affiliated with CD-adapco.

2

Corresponding author.

3

Currently affiliated with General Electric Technology Infrastructure - Aviation.

J. Turbomach 134(6), 061014 (Sep 04, 2012) (9 pages) doi:10.1115/1.4006284 History: Received December 22, 2010; Revised March 02, 2011; Published September 04, 2012; Online September 04, 2012

This article contains an investigation of the unsteady acoustic forcing on a centrifugal impeller due to coupled blade row interactions. Selected results from an aeromechanical test campaign on a GE Oil and Gas centrifugal compressor stage with a vaneless diffuser are presented. The most commonly encountered sources of impeller excitation due to upstream wake interaction were identified and observed in the testing campaign. A 30/rev excitation corresponding to the sum of upstream and downstream vane counts caused significant trailing edge vibratory stress amplitudes. Due to the large spacing between the impeller and the return channel vanes, this 30/rev excitation was suspected to be caused by an aero-acoustic excitation rather than a potential disturbance. The origin of this aero-acoustic excitation was deduced from an acoustic analysis of the unsteady compressor flow derived from CFD. The analysis revealed a complex excitation mechanism caused by impeller interaction with the upstream vane row wakes and subsequent acoustic wave reflection from the downstream return channel vanes. The findings show it is important to account for aero-acoustic forcing in the aeromechanical design of low pressure ratio centrifugal compressor stages.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Cut-away of the experimental test rig with the installed impeller stage. The gas flow path is indicated.

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Figure 2

Stage interference diagram. F1: Shroud vibration modes, F2: Disk outer diameter modes and F3: Blade first bending modes. The vertical lines and circled excitation orders denote the relevant crossings.

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Figure 3

Impeller F2 mode shape with 9 nodal diameters

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Figure 4

Schematic of test rig unsteady pressure sensors, impeller strain gauges and CFD probe locations. Flow direction indicated by bold arrows.

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Figure 5

Experimental Campbell diagram for SG2

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Figure 6

Unsteady pressure spectra from the CFD probes on the impeller

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Figure 7

Pressure contours within impeller CFD domain associated with the 30/rev excitation on the impeller. Dark or blue color indicates negative unsteady pressure and light or red color indicates positive unsteady pressure. NB: Presented CFD domain extends upstream and downstream of actual impeller.

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Figure 8

2D pressure spectra derived from CFD probes at SG2 location (rotating reference frame)

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Figure 9

2D pressure spectra derived from CFD probes at station 10 (stationary reference frame)

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Figure 10

2D pressure spectra derived from CFD probes at station 30 (stationary reference frame)

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Figure 11

Directional decomposition of dominant acoustic modes in diffuser channel

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