Multiobjective Aerodynamic Design Optimization of the Contour of Annular Aerospike Nozzles

For truncated annular aerospike nozzles, shape optimization is conducted using CFD and an evolutionary algorithm. The objective function is the thrust coefficient at a pressure ratio of 6 and 35. The contour line of the spike wall is defined by design variables which determine the coordinates of the control points of the cubic spline. Regardless of the position of truncation, the nozzle with a smaller base area can produce higher thrust when the pressure ratio is low, and the nozzle with a larger base area can produce higher thrust when the pressure ratio is high. All optimal contours are almost linear at the upper part of the ramp region, and the slope near the position of truncation makes a difference. Considering the flow field around the spike wall, the shorter truncated nozzle is preferable among two cases in this study, because flow separation caused by the shock wave can be avoided during the flight, which makes the vehicle more stable.