Radial turbine preliminary aerodynamic design optimization for expander cycle liquid rocket engine

A response surface-based dual-objective design optimization was conducted in the preliminary design of a compact radial turbine for an expander cycle rocket engine. The optimization objective was to increase the efficiency of the turbine while maintaining low turbine weight. Polynomial response surface approximations were used as surrogates, and the accuracies of such approximations improve by limiting the size of the domain and the number of variables for each response of interest. The optimization was accomplished in three stages using an approximate, one-dimensional model. In the first stage, a relatively small number of points were used to identify approximate constraint boundaries of the feasible domain and to reduce the number of variables used to approximate each one of the constraints. In the second stage, a moderate number of points in this approximate feasible domain were used to identify the region where both objectives had reasonable values. The last stage focused on obtaining high accuracy approximation in the region of interest with large number of points. The approximations were used to identify the Pareto front and to perform a global sensitivity analysis. Significant improvement was achieved compared to a baseline design.