Fluidic throat technology for hybrid rocket motor based on liquid oxidizer cooling

Hybrid rocket motor have great application prospects in the field of cruise aircraft due to its relatively simple structure, easy thrust adjustment, and relatively high specific impulse performance. However, during deep thrust adjustment, there is a significant loss of specific impulse at low thrust conditions. Therefore, this paper proposes a fluid throat design for hybrid rocket motor based on liquid oxidizer cooling. A small amount of secondary oxidizer flow is diverted from the tank, flows through the cooling channels in the converge section of the nozzle, cools the nozzle wall, and passes through the liquid collection chamber and a small catalytic device where the secondary flow is decomposed into hot gases, and then injects into the internal flow field, which can improve the overall motor specific impulse. This paper conducts numerical simulations of the heat transfer of liquid oxidizer cooling and the flow process in the motor combustion chamber. The results show that under the condition of equal total mass flow rate, the addition of secondary flow increases the overall specific impulse of the motor. With the increase of the ratio of secondary flow to main flow rate, the overall specific impulse of the motor increases first and then decreases. Typically, the maximum value is obtained at a flow rate ratio of 0.2. In addition, as the secondary flow rate increases, the wall temperature of the converging section of the motor decreases, When the flow rate ratio is below 0.14, the coolant temperature in all conditions has already exceeded the permissible range.