Numerical Simulation Of Insulation Layer Ablation In Solid Rocket Motor

The solid rocket motor is the propulsion system for rocket and missile. It possesses considerable advantages, such as high specific impulse, high reliability, simple structure, high maneuver and low cost etc. The solid rocket motor has been widely used in various fields. Since the motor has to work under the severe environment of high temperature and high pressure for long time, thermal protection is very important in solid rocket motor, and the research on the ablation of the insulation layer is of great significance. In this paper, computational fluid dynamics(CFD) software FLUENT was used to study the ablation of carbon phenolic insulation layer in the solid rocket motor. The insulation layer ablation in combustor and nozzle during burning was analyzed by using a two-dimensional axisymmetric model and dynamic mesh method. The results can be used as reference for the design of insulation layer of solid rocket motor.Firstly, the influences of wall function method, external flow field and turbulence intensity on the calculation results were analyzed in this paper. The results show that the enhanced wall treatment has higher accuracy than standard wall function. There is no apparent difference made to the calculation results when external flow field is considered in the model. The erosion rate of insulation layer increases with the increasing of turbulent intensity. Based on former analyses, the enhanced wall treatment model without of external flow field was used to analyze the characteristics of insulation layer ablation in solid rocket motor, and factors which may affect the ablation of insulation layer were also investigated. The results show that, due to the high thermal conductivity of throat insert and low thermal conductivity of insulation layer, the nozzle temperature and ablation rate is very low and the ablation rate of insulation layer in the combustor is high at the initial time. The wall temperature difference between the combustor and nozzle slowly decrease as time increase. The maximum erosion rate occurs at the upstream of the nozzle throat. The erosion rate increases as burning time increase, the increase rate becomes lower and lower. The most serious ablation occurs at the insulation layer of the combustor closing to the nozzle and the upstream of the nozzle throat, and the ablation phenomenon is not obvious at the nozzle divergent section. The chemical reaction caused by H2 O is the main factor for wall ablation, while the ablation caused by CO2 is very less.Lastly, the influences of temperature, pressure, burning surface velocity and discrete phase particles(dpm) on the erosion rate of insulation layer were analyzed. Results show that the dpm erosion rate increases with the increasing of inlet pressure and temperature. Near the inlet, the dpm erosion rate decreases with the increasing of burning surface velocity. Discrete phase particles deposited on the inner surface of the combustor closing to the nozzle. The dpm erosion rate increases with the increasing of mass flow rate of discrete phase particles, the erosion area increases with the increasing of particle diameters, and inlet velocity of dpm has less impact on the dpm erosion rate. Comparing with the erosion rate of chemical reactions, the dpm erosion rate is very low and can be neglected.