Mitigation of Axial Flow Turbine Losses by An Optimised Bump Hub Wall Treatment

The change in turbine stator 1 and rotor hub surface shapes has a significant effect on the reduction of the turbine secondary flow losses. This reduction was implemented by boosting the aeroderivative optimised bump hub wall treatment in both stator 1 and rotor hub surfaces that reduced results from the reduction of the turbine flow separation losses. This technique was compared with axisymmetric hub surface in Aachen Turbine that used in industry and the highest increased in turbine stage isentropic efficiency was used. This prevented the suction side branch and the pressure side horseshoe vortex from combining. The mixing plane between the turbine stator 1 and rotor experienced a drop in turbulent kinetic energy as a result. By using a hub shaped by the optimised bump, a 6.19% reduction in the total pressure loss coefficient predicted by openFOAM is expected as compared with axisymmetric hub in both stator 1 and rotor. A Kriging surrogate model is used to predict the best surface parameters for the optimised stator 1 and rotor hub surfaces. It is anticipated that the greater turbine stage isentropic efficiency will improve the profitability by 0.23%.