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TECHNICAL PAPERS: Gas Turbines: Controls, Diagnostics & Instrumentation

Enhancing Flow Field Measurements Through Adaptive Multidimensional Data Sampling

[+] Author and Article Information
Arnoud R. Franken, Paul C. Ivey

School of Engineering, Cranfield University, Cranfield, Bedfordshire MK43 0AL, UK

Yaw angle is a flow angle measured in the horizontal plane. See, e.g., Franken and Ivey (1) for a more detailed discussion on the measurement of this flow angle and other flow variables using a multihole pressure probe.

In following iterations, only one thin-plate spline model will be developed as the “previous” model is available from the previous iteration.

The acceptable minimum difference is an application-dependent quantity. Factors that should be taken into consideration when setting this difference are, e.g., the measurement inaccuracy of the sensor used and the stability of process variables during measurements.

The exact reduction in duration and running cost of rig tests that can be realized is dependent on the design of the test rig, the complexity of the flow field features encountered at the operating conditions of interest, the layout and density of the conventional grid utilized as a benchmark, and the capabilities of the probe positioning system used. These factors are test and/or facility dependent, and therefore, outcomes achieved at one facility are not necessarily comparable to those achieved at another. Because of these reasons, no figures are presented here for indicative purposes.

J. Eng. Gas Turbines Power 128(3), 518-524 (Sep 06, 2005) (7 pages) doi:10.1115/1.2135822 History: Received August 30, 2005; Revised September 06, 2005

A way to gain insight into the flow field conditions in turbomachinery is by carrying out a series of point measurements in a cross section of the flow, for example, with a miniature multihole pressure probe. A problem commonly encountered in situations like these is the selection of a suitable measurement grid layout and density for obtaining all essential information in a cost-effective and timely manner. In order to achieve the latter, a novel adaptive multidimensional data sampling technique has been developed at Cranfield University. This paper describes the underlying principles of this technique, the algorithms utilized, and the results obtained during its successful application to data sets of two different flow fields in a high-speed research compressor.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 3

Yaw-angle distribution obtained with the measurement grid shown in Fig. 1 during a different HSRC rig test

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Figure 4

Cranfield University’s high-speed axial research compressor (HSRC) test rig

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Figure 7

Adapting the local measurement grid density

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Figure 11

Fourth and final measurement grid containing 900 grid points. The locations, shapes, and sizes of areas of high and low sample point density clearly correspond with the areas of rapid and smooth change visible in Fig. 3.

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Figure 12

Thin-plate spline approximation/interpolation of the yaw-angle distribution shown in Fig. 3

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Figure 13

Differences between the approximated and measured yaw-angle values

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Figure 1

Measurement grid used to investigate flow field effects in Cranfield University’s High-Speed Research Compressor. This measurement grid contains 1464 sample points and is 1 1∕2 blade-pitch wide.

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Figure 2

Yaw-angle distribution obtained with the measurement grid shown in Fig. 1 during a HSRC rig test

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Figure 5

Schematic of the traversing of a pressure probe through a measurement grid in a compressor cross section

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Figure 6

Improvement of the thin-plate spline approximation (solid line) by adding more sample points (∙) to the data set

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Figure 8

Initial measurement grid utilizing a priori knowledge of the flow field conditions

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Figure 9

Second measurement grid

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Figure 10

Third measurement grid. The higher sample point densities near the hub (H<0.2), casing (H>0.9), and compressor blades (A=0.2 and A=0.7) clearly indicate the locations, shapes, and sizes of the areas of rapid change.

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