Advanced aerodynamic analysis of the supersonic flow field of an aerospike engine

Abstract

In the last decade, the aerospike has been reconsidered as an alternative of the traditional bell-shaped nozzle because with the improving of additive manufacturing technique it has been possible to enable the fabrication of complex features while drastically reduce production time and manufacturing costs. Nevertheless, there are still some issue that should be solved to realize reliable engines. During the ascent phase of a launcher, the aerospike could deliver more thrust than a bell-shaped nozzle with the same expansion ratio and exit section area due to the capability to adapt the expansion reaching the ambient pressure in a wide range of altitudes. This research has been focused on the improvement of the aerospike performance simulating a small engine with different spike shapes in order to identify sources of losses and to determine which is the most efficient one. The considered shapes have been obtained using the Angelino's method and cutting the spike to achieve the target base radius. The exit section has been kept constant in different designs. The study compares the simulations results with the ones obtained applying the isentropic nozzle theory, highlighting the different behaviours of the flow at throat section and over the spike in terms of pressure and velocity distribution. In particular, the influence of both the round connection between the throat section and the external wall, and the connection between flow inclination at the throat section and the thrust loss at the base has been analyzed. Finally, a rough estimation of the thrust-to-mass ratio has been obtained.