Transient simulation of operation process in a throttleable hybrid rocket motor

A throttleable hybrid rocket motor was developed at Beihang University to assess the throttling capability of hybrid rocket motor. The motor used hydroxyl terminated polybutadiene (HTPB) as the solid fuel and 90% hydrogen peroxide(HP) as the oxidizer. The oxidizer flow rate is from 0.1kg/s to 0.5kg/s, and the thrust is from 250N to 1250N with a 5:1 throttling ratio. Transient behaviour is a very important issue in the development of the throttleable hybrid rocket motor. An unsteady simulation model was developed in this paper to investigate the combustion process in the throttleable hybrid rocket when the oxidizer flow rate was throttled. The realizable κ - ε turbulence model combined with the Eddy-Dissipation combustion model were adopted in the present study, and gas-solid coupling model were used to simulate the regression process of the solid fuel surface. The distributions of temperature, velocity, species concentration was obtained, as well as solid fuel regression rate. The simulation results show that it need some time for chamber pressure and regression rate to react to the change of oxidizer mass flow rate.