Influence of Measurement Grid Resolution on Duct Loss Evaluation

Authors

Stefan Zerobin - Graz University of Technology
Michael Steiner - Graz University of Technology
Sabine Bauinger - Graz University of Technology
Andreas Marn - Graz University of Technology
Emil Göttlich - Graz University of Technology
Franz Heitmeir - Graz University of Technology

Abstract

For this study, measurements were carried out in a one-and-a-half stage test turbine. In order to characterize the flow field and to obtain steady flow quantities, five-hole probes are used in the rig in several measurement planes. Although a very high resolution in circumferential and radial direction is possible with five-hole probes, only certain sectors of the flow field can be measured due to quite long measurement times. For this reason, total pressure rakes, which can be traversed 360 degrees in a circumferential direction, were built for this test configuration. During foregoing measurements, differences between the total pressure measured with the rakes and the total pressure measured with a five-hole probes were observed, especially in the measurement plane downstream of the rotor where the flow is highly unsteady. It was found that the measured value for total pressure is particularly influenced by the stochastic pressure fluctuations and turbulence and can therefore deviate significantly from the "real" value.