Investigation of the effect of ring-cavity on secondary-combustion and interior ballistic stabilization with low-temperature solid propellant in gas ejection

The potential for secondary-combustion with low-temperature solid propellant in gas generation is a potential risk to ejection application. This study performed a three-dimensional dynamic numerical simulation with Re-Normalization Group turbulence model and finite-rate/eddy-dissipation model of a two-step reaction mechanism to better understand the interaction between secondary-combustion and ring-cavity structures, and combustion effect on the loads and interior ballistic stabilization during ejection. The dynamic zone of rail cover was modelled as a rigid body, and its motion was coupled with the secondary-combustion flow in the initial chamber based on the dynamic layering method. A comparison between the numerical results and experimental data in published literature showed good agreement. Four different ring-cavity volume geometries were simulated, including no ring-cavity. Results showed that three-stage high-temperature zone can be divided in the initial chamber at the founding time in the four cases, which are a pair of spherical high-temperature zone, high-temperature zone with skirt touching walls and high-temperature zone reverse from rail cover. Additionally, increasing ring-cavity volume can accelerate the axial and radial hot gas velocity on the ring-cavity cross-section and postpone secondary-combustion process. It was also found that larger ring-cavity volume structure can smoothen the pressure and acceleration curves, reduce the out-tube-velocity and delay the out-tube-time.