Optimal design of solid rocket motor nozzle under two-phase flow

To enhance the performance of solid rocket motor nozzles, six design parameters were selected as variables: transition arc radius, exit half-angle, major axis, minor axis, convergence section arc radius, and initial expansion section radius. A multi-objective optimization study under two-phase flow conditions was conducted using Isight. First, parameter sensitivity analyses were performed using both single-phase and two-phase flow calculation methods. The results indicated that the minor axis b of the elliptical design had the most significant impact on the thrust coefficient and specific impulse. Next, surrogate models based on Kriging interpolation were constructed for the baseline nozzle flow field using both indirect and direct optimization methods, followed by a three-objective optimization process. The optimization targets included the thrust coefficient, specific impulse, and total pressure recovery coefficient. The second-generation Non-Dominated Sorting Genetic Algorithm (NSGA-II) was employed to analyze and solve the surrogate models. The computational results revealed that, compared to the baseline nozzle, both optimization methods significantly improved performance parameters by approximately 2%. While the direct optimization method yielded slightly better performance gains, the indirect optimization method required lower computational costs.