Endwall contour design targeting on optimum aerodynamic efficiency of turbine stage and sealing effectiveness of rim seal

Abstract

Endwall contour optimization design utilized to improve the aerodynamic performance has impact on the flow field near rim seal, and it consequently affects the sealing performance. Combined with Kriging agent model, NSGA-II genetic algorithm and CFD which solves the three-dimensional unsteady Reynolds-averaged Navier–Stokes equations coupled with a fully developed shear stress transport turbulent model, this paper constructs an optimization design system for turbine non-axisymmetric endwall contour design in order to improve aerodynamic efficiency and sealing effectiveness simultaneously. The numerical method for predicting the flow in wheel-space and sealing performance of turbine rim seal is validated on the basis of published experimental data. The base flat endwall design, and two optimal endwall contour designs are selected to investigate the aerodynamic and sealing performance. The results show that the aerodynamic and sealing performance can be improved at the same time. Compared with the base flat endwall design, the total-to-total efficiency is increased by 0.23% and the sealing effectiveness is increased by 11.49% for optimal design 1 at optimal design point. Optimal design 1 can significantly reduce the aerodynamic loss and for different sealing flow rates, the total-to-total efficiency is greater than that of base flat endwall design. Compared with the base flat endwall design, the total-to-total efficiency is increased by 0.15% and the sealing effectiveness is increased by 15.43% for optimal design 2 at optimal design point. The influence of endwall contour on sealing effectiveness is obvious when the cooling flow rate is small. The work of this paper provides a reference for the design of non-axisymmetric endwall with comprehensive optimization of turbine aerodynamic and rim sealing performance.