Influence of taper, Reynolds number and Mach number on the secondary flow field of a highly loaded turbine cascade

Abstract

The meridional divergence of low-pressure turbines has a strong influence on their secondary flow field. This paper describes experimental and numerical investigations on two highly loaded linear turbine cascades with the same blade profile and stacking but with parallel end walls and divergently tapered end walls respectively. The effects of taper, Reynolds number (1.2 × 105, 5 × 105) and Mach number (0.30, 0.59, 0.80) are discussed. Data were obtained using pneumatic probes, pressure tappings and surface flow visualizations. Calculations were performed with the three-dimensional Navier—Stokes solver BTOB3D. The investigations show a strong influence of the taper on the pressure distribution and an unexpected high rise in secondary loss. In both cascades the secondary loss coefficient rises with reduced Reynolds number and Mach number respectively.