Three Dimensional Optimization for Subsonic Axial Turbines Operating at High Unsteady Inlet Mach Number

摘要

In this paper, a three dimensional optimization strategy is presented to improve the performance of a subsonic axial turbine exposed to high Mach number unsteady inflows encountered in pressure gain combustors. The optimization aims at altering the stator hub and shroud end wells. A multi-objective differential evolution optimizer was used to enhance specific work and efficiency. The optimization routine consisted of a multi-step approach where in a first step an optimization was carried out where the turbine was subjected to a steady high Mach inflow. The turbine stage was parametrized via an in-house turbine design tool based on Bezier curves. Seven design parameters were selected to contour the stator end walls and rotor hub end wall. The parametrized turbine stage was meshed and the steady Reynolds-Averaged Navier-Stokes equations were solved via the commercial solver CFD-H- and calculation time of each stage was around 10 hours. Results of the steady optimization identified three major design parameters of stator end walls, which were taken as inputs for the next phase unsteady optimization. For the unsteady simulations, a large inlet fluctuation was imposed and the turbine was modeled with the mixing plane approach. Total calculation time of each individual was 48 hours. An efficiency improvement of 10% from the steady optimization and 13% from the unsteady optimization was found compared to the baseline case. Finally, full unsteady simulations with two stator and three rotor passages were performed on selected steady and unsteady optimized configurations.