Numerical and Experimental Analysis of the Effects of Non-Axisymmetric Contoured Stator Endwalls in an Axial Turbine

Abstract

Numerical and experimental investigations have been performed to determine the effects of non-axisymmetric stator endwall contouring on the efficiency of an axial turbine stage. The influences of the contoured endwalls on the secondary flows in the stator and the rotor have been analyzed by conducting steady and unsteady RANS simulations as well as measurements in the 1.5-stage axial cold air turbine test rig of the Institute of Jet Propulsion and Turbomachinery. Both numerical and experimental results show an aerodynamic improvement of efficiency and secondary kinetic energy through non-axisymmetric endwall contouring. The non-axisymmetric endwall contour induces a vortex, which separates the pressure side leg of the horseshoe vortex from the passage vortex resulting in redistributed and reduced secondary flows. The modified secondary flow pattern increases the torque of the rotor blade in the hub region as a consequence of improved inlet conditions for the rotor as well as a reduction of the time interval the secondary flows are convected through the rotor passage within. Concerning the shroud region the endwall contour had no significant impact on the efficiency as a consequence of a dominating tip clearance vortex system.