Influence of trailing edge thickness and deflection on the performance of a ram air turbine for hypersonic vehicle power generation

Abstract

A ram air turbine power generation system can address the energy utilization challenges of hypersonic vehicles. However, as the maximal flight Mach number of hypersonic vehicles is constantly increased, the total temperature of the incoming airflow becomes extremely high, making it unsuitable for cooling purposes. Therefore, active cooling of the ram air turbine must be achieved using fuel as a heat sink. Applying active cooling by arranging internal cooling channels at the main hotspot like blade edge may lead to thickening and additional deflection of trailing edge. This study focuses on an impulse ram air turbine stage and introduces a continuous curvature profiling method for ram air turbines. The turbine performance is evaluated by numerical simulations under varying trailing edge thicknesses and deflection. Then, an efficiency correction model that accounts for trailing edge effects is developed based on a classical loss model. The results show that a continuous curvature blade achieves a 1.99 % improvement in stage efficiency compared to a typical blade. Particularly, trailing edge thickening enhances the secondary flows of turbine and significantly reduces the stage efficiency. Reducing the trailing edge deflection results in an initial increase in stage efficiency, which decreases afterward, implying the existence of optimal deflection that maximizes stage efficiency. Specifically, a linear correlation between the optimal deflection and trailing edge thickness is observed. The efficiency correction model is used to predict the efficiency of the GE E3 turbine, and the error is less than 1.5 % compared with experimental data.