Study of Conical Aerospike Nozzles with Base-Bleed and Freestream Effects

Conical aerospike nozzles are advanced rocket nozzles suitable for altitude compensation. A spike nozzle has geometry that resembles a conventional bell nozzle turned inside out. Lack of a solid outer surface ensures the variation of gas expansion to match the prevailing atmospheric pressure at different altitudes. This study focuses on flow characteristics within conical aerospike nozzles with different levels of truncation and flow conditions. Full spike and truncated aerospike nozzles are numerically simulated using two-dimensional axisymmetric and full three-dimensional models. Reynolds-averaged Navier-Stokes equations are solved with the shear stress transport k-omega turbulence model. Computational results of 20, 40, and 60% truncated nozzles are studied in comparison. Base bleed is implemented at two different locations of the base in 20% aerospike nozzle. Base bleed is taken as 2% of the inlet mass flow. The freestream effect is applied to 40% aerospike nozzle for validation purpose and 20% aerospike nozzle with different base-bleed cases for evaluation. Comparison of results establishes that the introduction of base bleed assists in compensating performance loss due to truncation, with the location of bleeding playing a major role in performance improvement. Effects of freestream on the base pressure characteristics of the nozzle are also demonstrated in comparison to nozzles without freestream.