Designing an axisymmetric aerospike nozzle based on modied MOC

Abstract

This study provides a direct method based on the method of characteristics with assumptions of non-viscous ow and thermally perfect gas to design an axisymmetric plug nozzle. Inputs for numeric code include output Mach number, specic heat ratio, global gas constant, and a number of discrete steps of Prandtl-Meyer expansion fan. In the design process, no simplication was made and only unique spike geometry was created. Based on the criterion that locates the tip of the spike on the axis of symmetry, for each output Mach number, a correction factor was extracted which is the sole source of theoretical errors. The studied parameters include spike geometry, parallelism of exhaust nozzle ows and uniformity. Based on the numerical analysis, obtained results are consistent with desired output Mach number, and output ow is parallel to the axis of symmetry. A simple and direct formulation was used which performed very fast. Due to the error detected, which resulted in the surface slope reduction factor, some movement in spike geometry relative to ideal conditions was raised. Thus, the eect of a reduction factor may tend to zero by increasing the design Mach number.