Non-axisymmetric endwall contour optimization and performance assessment as affected by simulated swirl purge flow and backward hole injection

Abstract

A shape optimization system was constructed using the kriging model, NSGA-II algorithm and CFD simulation, and the endwall contour was optimized targeting on balancing the endwall cooling and blade phantom cooling performances. Off-design conditions of simulated swirl purge flow and backward hole injection were introduced to evaluate the aero-thermal performances of the optimal non-axisymmetric endwall. The results show that two optimal contours are able to increase the endwall adiabatic effectiveness separately by 3.518% and 2.177%, but the flat endwall achieves the best phantom cooling performance. Under both design and off-design condition, the slot coolant coverage on pressure side endwall is enlarge by contours. The swirled slot leakage is able to weaken the tendency for the hole coolant to cover the suction side hot ring on both contoured and flat endwall. With the increase of SR, the averaged phantom cooling effectiveness is decreased when slot MFR = 1.0% but increased when MFR = 1.5%. When MFR = 1.0%, the averaged endwall Nu between 0.4 < z/Cax < 0.8 is decreased by 15% in optimal_2. When MFR = 1.5%, the averaged Nu for the upstream part endwall is increased by approximately 20% when SR = 0.6 compared with SR = 1.0. The net heat flux reduction of the pressure side endwall is increased by contouring, but the swirled purge flow dramatically decreases this protection effect. This research provides insights into the designing of non-axisymmetric endwall in off-design film cooling condition.