Reducing rotor secondary losses in a turbine stage through endwall airfoil profiling

Abstract

The rotor blade of an experiment turbine for low Reynolds number flow conditions is recontoured on the hub endwall to reduce the hub’s secondary flow losses. The baseline rotor blade is radially stacked with airfoils of free vortex twisting. The hub section airfoil of the rotor blade is reprofiled for three considerations. The first is to reduce the inlet metal angle to fit with the vane’s exit flow angle near the hub endwall. The second is to reduce the airfoil’s stagger angle to reduce the pitchwise pressure gradient on the hub endwall. The third is to extend the airfoil’s axial chord to a limited distance before the baseline one to build a leading edge fillet. A steady RANS flow computation is carried out to compare the flow fields inside the baseline and the new contoured rotor passages. Flow comparison reveals that the passage vortex intensity is reduced and that the total pressure loss is reduced by 8.9 % in the hub region. The new contoured rotor shows potential application in reducing rotor secondary losses through the stacking of two-dimensional sectional airfoils.