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Research Papers: Gas Turbines: Controls, Diagnostics, and Instrumentation

Experimental Analysis of a Waveguide Pressure Measuring System

[+] Author and Article Information
Matthew A. White

Compressor Research Laboratory, School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA 30332maw@gatech.edu

Manuj Dhingra

Compressor Research Laboratory, School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA 30332m.dhingra@gatech.edu

J. V. R. Prasad

Compressor Research Laboratory, School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA 30332jvr.prasad@aerospace.gatech.edu

J. Eng. Gas Turbines Power 132(4), 041603 (Jan 26, 2010) (7 pages) doi:10.1115/1.3159387 History: Received March 24, 2009; Revised April 07, 2009; Published January 26, 2010; Online January 26, 2010

An infinite-line probe is commonly used to measure unsteady pressure in high-temperature environments while protecting the pressure transducer. In this study, an existing theoretical model is used to derive the response of a waveguide pressure measuring system. An ambient temperature centrifugal compressor rig acts as an experimental source of fluctuating pressure. The compressor is operated at different discrete rotational speeds, and the blade-passing frequencies are used to obtain frequency response data. In the experiments, pressure waves attenuated at a rate faster than that predicted by the theoretical model for a 0.322 m (12 in.) sensor offset. Furthermore, the decay in the magnitude of the pressure oscillations accelerated at blade-passing frequencies above 9 kHz. A unique contribution of this study is to show that whereas the experimentally observed overall attenuation is broadly consistent with the theoretical predictions, pressure oscillations corresponding to individual blade passages may be disproportionally attenuated.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 2

A sketch of the waveguide experimental setup. The longer sensor offset (0.322 m) is shown here.

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Figure 3

Theoretical bandwidth predictions with varying transducer offset length. The nominal value of offset L is 0.322 m.

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Figure 7

Theoretical and experimental results comparison for 0.178 m (7 in.) transducer offset

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Figure 9

Theoretical and experimental results comparison for 0.178 m (7 in.) transducer offset while beginning measurement sequence at 4.26 kHz (twice the lowest rotational speed

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Figure 10

Raw pressure time trace for 1 kHz blade-passing frequency

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Figure 11

Pressure response for 2.8 kHz blade-passing frequency

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Figure 4

Theoretical bandwidth predictions with varying waveguide radius

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Figure 5

Pressure transducer volume comparisons

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Figure 6

Theoretical bandwidth predictions with varying temperature

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Figure 8

Theoretical and experimental results comparison for 0.322 m (12 in.) transducer offset

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Figure 12

Pressure response for 9.3 kHz blade-passing frequency

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Figure 13

Experimental pressure response for 2.8 kHz blade-passing frequency after Vv0 is shifted to account for time delay with 0.322 m between sensors

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Figure 14

Experimental pressure response for 9.3 kHz blade-passing frequency after Vv0 is shifted to account for time delay with 0.322 m between sensors

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Figure 1

Schematic of Georgia Tech centrifugal compressor setup

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