Non-axisymmetric endwall profile optimization of a high-pressure transonic turbine using approximation model

Abstract

Secondary loss of low aspect ratio turbines takes as much as 50% of the total loss. Non-axisymmetric endwall profile optimization was conducted for the nozzle hub and shroud of a 1-stage high-pressure transonic turbine. The endwalls of the hub and the shroud were individually optimized using an approximation model. Kriging model was used for response surface generation and the optimum solution was searched using Genetic Algorithm with stage efficiency as the objective function. Optimized endwall profiles reduced nozzle losses and shocks, thereby improving stage efficiency. The shroud endwall profile showed higher performance, because it influenced the flow over the whole span, whereas the influence of the hub endwall profile was limited close to the hub. The stage efficiency was improved by 0.39%p when both the hub and the shroud endwall profiles were applied. However, the mass flow rate exceeded the design limit and the efficiency had no benefit to the single shroud endwall profile, showing the limitations of individually optimized endwall profiles.