Measurement and Prediction of Tip Leakage Losses in an Axial-Flow Transonic Turbine
- Wehner, M. HBI Haerter AG, Zurich, Switzerland
- Bütikofer, J. ABB Power Generation Ltd., Baden, Switzerland
- Hustad, C-W. Swiss Federal Institute of Technology, Lausanne, Switzerland
- Bölcs, A. Swiss Federal Institute of Technology, Lausanne, Switzerland
- 2014-12-24
Published in:
- Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery. - American Society of Mechanical Engineers. - 1997
English
This paper presents a simple method for predicting tip leakage losses in transonic axial-flow turbines. The method is based upon experimental work conducted on a flat plate at 5° incidence and with isentropic exit Mach number of 1.26. The tip gap height was varied from zero up to 15% of chord. Measurements were made (using Laser-2-Focus) of velocity vectors around the tip gap region. These revealed a strong shear layer emerging from the gap onto the suction side of the plate. The relative angle between the leakage flow and the freestream was identified as a key parameter determining the subsequent mixing and overall loss generation. The proposed model applies two-dimensional potential flow analysis to estimate the flow angle as a function of tip gap height and the angle of incidence.
Subsequently, comparisons were made with experimental results obtained in an annular cascade on the outer profile of the last-stage blade of a steam turbine. The predicted tip leakage losses compare favourably with the measured values.
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- https://sonar.ch/global/documents/37842
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