Effects of hub endwall geometry and rotor leading edge shape on performance of supersonic axial impulse turbine. Part II: Method validation and final results

Abstract

The present paper continues the investigation started in Part I. The basic turbine stage remains the same as in Part I (an axial turbine stage with axisymmetric nozzles and mean diameter 103.5 mm). The numerical simulation method used in Part I was corrected by adding analytical correlation for disc friction losses. This approach was validated on the base of the experimental data for a geometrically close turbine. Variation of the radial velocity component at the rotor inlet was proposed as a new modification compared with Part I. The mathematical formulations of the rotor blade sweep and radial velocity component at the rotor inlet were proposed. The new modifications of the baseline were provided to establish the effects of the rotor blade sweep, velocity radial component at the rotor inlet and hub endwall contouring separately. The using of backward swept rotor blades together with the positive cinematic lean provided efficiency increasing up to 2.9% at the design conditions. It was also established that absence of a velocity radial component at the rotor inlet in the model with backward swept blades leads decreasing of the turbine performance. Axisymmetric hub contouring provided up to 1.9% efficiency growth at the part-load operation.