INFLUENCE OF TAPER, REYNOLDS-NUMBER AND MACH NUMBER ON THE SECONDARY FLOW-FIELD OF A HIGHLY LOADED TURBINE CASCADE

The meridional divergence of low-pressure turbines has a strong influe nce on their secondary flow field. This paper describes experimental a nd numerical investigations on two highly loaded linear turbine cascad es with the same blade profile and stacking but with parallel end wall s and divergently tapered end walls respectively. The effects of taper , Reynolds number (1.2 x 10(5), 5 x 10(5)) and Mach number (0.30, 0.59 , 0.80) are discussed. Data were obtained using pneumatic probes, pres sure tappings and surface flow visualizations. Calculations were perfo rmed with the three-dimensional Navier-Stokes solver BTOB3D. The inves tigations show a strong influence of the taper on the pressure distrib ution and an unexpected high rise in secondary loss. In both cascades the secondary loss coefficient rises with reduced Reynolds number and Mach number respectively.