Numerical investigation on regression rate and thrust regulation behaviors of a combined solid rocket motor with aluminum-based fuel

Abstract

The aims of this study are to determine the behaviors of regression rate and thrust regulation of a combined solid rocket motor, which is capable of achieving energy management. A numerical model was developed to capture the regression rate and simulate the combustion process of combined solid rocket motor by combining the Navies-Stokes equations with turbulence and gas-solid coupling models. The numerical method employs a 24-step reaction mechanism to characterize the combustion of aluminum and oxidizing gases with an eddy-dissipation-concept model. The regression rates of both grain strand and solid-fuel burning in subsonic condition were obtained, which show good agreements with the experimental data, validating the proposed model. Thereafter, the flow field structure was firstly illustrated to understand the evolution of the combustion process. The recirculation zones are formed behind the back-facing steps and thus enhance the diffusing of oxidizer towards the burning surface, sustaining the burning of solid-fuel via heat feedback. Secondly, a parametric study presents that the regression rate and surface temperature of solid grain increase with increasing oxidizer mass flow rate and reduce with increasing inner diameter of grain hole; and formulas are obtained to predict the regression rates for combined solid rocket motor with different oxidizer mass flow fluxes. Finally, it is shown that the present combined solid rocket motor can obtain relatively high combustion efficiency for all cases studied, and the regulation ratio of thrust exceeds the corresponding variation ratio of oxidizer mass flow rate. The present study not only elaborates the regression rate and thrust behaviors of combined solid rocket motor but also provides a guideline for energy management of solid rocket motor.