A Theoretical Study of Combustion Stability in Vortex Injection Hybrid Rocket Engine

Abstract

In this paper, we extend the exiting method to conduct combustion stability analysis in axial injection hybrid rocket engines to apply for vortex injection systems by introducing the swirl strength as a new input of the linear model, extending the quasi one dimensional flows to axisymmetric three dimensional flows and estimating axial skin-friction coefficient in swirl flows and skin-friction shear stress with blowing by contrasting one with no blowing. Next, to validate the accuracy of the quasi-steady boundary layer combustion model we compare regression rates derived from this model with ones derived from experiments. Then, linearizing the quasi-steady model, we construct unsteady models. Finally, we couple the unsteady boundary combustion model with the thermal time lags model in solid fuels and conduct stability analysis. It is estimated that swirl systems also have a set of unstable poles of natural oscillations and swirl and can be more unstable than axial ones.