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

One-Dimensional Flow-Adaptive Measurement Grid Algorithm for Pneumatic Probe Measurements

[+] Author and Article Information
Christian Bartsch

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

Magnus Hölle

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

Peter Jeschke

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

Timo Metzler

MTU Aero Engines AG,
Dachauer Straße 665,
Munich 80995, Germany
e-mail: timo.metzler@mtu.de

1Corresponding author.

Contributed by the Controls, Diagnostics and Instrumentation Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 14, 2015; final manuscript received August 4, 2015; published online September 22, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(3), 031601 (Sep 22, 2015) (8 pages) Paper No: GTP-15-1287; doi: 10.1115/1.4031319 History: Received July 14, 2015; Revised August 04, 2015

The subject of this paper is an algorithm for a flow-adaptive measurement grid developed for pneumatic probe measurements in steady flow fields. The performance of the algorithm is demonstrated by a circumferential traverse at a constant radial position with a pneumatic five-hole probe in an annular cascade wind tunnel. Compared to a conventional equidistant measurement grid, the algorithm automatically computes the amount of measurement points needed for a high resolution of the pressure distribution in turbomachinery flows. The algorithm is fully automated and approximates the pressure distribution of a preliminary transient measurement very accurately. Even though the spacing of the computed measurement points differs significantly from an equidistant grid, postprocessing corrections related to the probe head geometry can still be applied. Accompanying a redistribution of the measurement points is a reduction in the overall points needed for the measurement. The commonly encountered problem of data oversampling is therefore avoided. Compared to a conventional equidistant measurement grid, the adaptive grid showed a significant reduction in the overall measurement points and a reduction in the duration of the measurement—while maintaining the accuracy in the computation of flow parameters. The purpose of this paper is to demonstrate the performance of an automatic detection of measurement points so that valuable measurement time can be saved without a loss in quality of the obtained data.

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References

Figures

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Fig. 1

IST five-hole probe. (a) Probe head and (b) pressure holes and angle convection.

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Fig. 2

Sequential steps for knot computation. (a) Transient measurement points and (b) compensation of time lag and superposition.

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Fig. 3

Normalized expanded standard deviation depending on the number of knots distributed over four blade pitches

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Fig. 4

Linear reconstruction of pressure distribution for all pressure holes

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Fig. 5

Geometric illustration of projection distance d for pressure holes 1 and 3

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Fig. 6

Flow chart of adaptive measurement grid algorithm

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Fig. 7

Cross section of wind tunnel facility

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Fig. 8

Comparison of highest possible resolution to reference grid

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Fig. 9

Influence of traversing speed on superposition of transient pressure signals

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Fig. 10

Influence of traversing speed on accuracy of flow parameter computation

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Fig. 11

Five-hole probe raw pressures of reference and knots of adaptive grid no. 4

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Fig. 12

Yaw angle differences of adaptive grids to reference measurement depending on the amount of knots

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Fig. 13

Normalized standard deviation of measurement grids as a function of traversing time

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Fig. 14

Normalized maximum difference of measurement grids as a function of knots

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