DESIGN AND FLOW SIMULATION OF TRUNCATED AEROSPIKE NOZZLE

Abstract

Aerospike nozzles are being considered in the development of the Single Stage to Orbit launching vehicles because of their prominent features and altitude compensating characteristics. This paper presents the design of aerospike nozzles using characteristic method in conjunction with streamline function, and performance study through numerical simulation using commercial Computational Fluid Dynamics (CFD) code ANSYS FLUENT. For this purpose nozzles with truncation lengths of 25%, 40%, 50% are choosen, because of the thermal and structural complications in the ideal aerospike nozzle. Simulation of the flow is carried out at three different altitude conditions representing Under-expansion, Ideal, and over-expansion conditions of the flow. FLUENT predictions were used to verify the isentropic flow assumption and that the working fluid reached the design exit Mach number. The flow-fields obtained through the numerical simulation are analysed to know the effect of truncation on the performance of aerospike nozzle. Optimum percentage of the truncation is selected by the comparison of nozzles with different lengths of truncation under various altitude parameters. The results show that the flow pattern of the nozzles under different altitude conditions are almost similar. The 40 % truncated nozzle is found to give optimum performance and it has achieved the desired exit Mach number in all the three altitude conditions.