Study Of Ablation Model In Oxygen-Riched Condition

During the study of Solid Rocket Ramjet (SRR), ablation of afterburner thermal insulation is a serious problem, which cannot be ignored. It is important to establish ablation model and predict ablation rate of thermal insulation in oxygen-riched condition. This paper investigated ablation mechanism from experimental and theoretical aspects.An experiment system simulated afterburner oxygen-riched condition was established. The system was composed of ablation test motor, gas supply pipeline and measurement and control system. Ablation experiments were carried out using this system to study main factors that influenced ablation. The experiment results showed that such parameters as oxygen percentage and pressure would affect ablation greatly.The ablation process in oxygen-riched condition was explored and a physical model was established. Electron Microscope scanning showed that thermal insulation would form three layers during ablation, namely, primitive material layer, pyrolytic layer and charred layer. Because thermal insulation was in oxygen-riched condition of afterburner and charred layer was porous, oxygenous gas in mixture would penetrate into charred layer and chemical reaction would take place in whole charred layer, which intensified the ablation process.According to the physical model, a mathematical model and computational method were proposed. An axially symmetric transient thermal conduction equation was put forward, which included material pyrolysis, pyrolysis gas flow and chemical reaction in charred layer. Chemical reaction was controlled by chemical dynamics, and the reaction rate was computed using Arrhenious Equation. Boundary conditions were obtained by energy, mass balance relationship on insulation surface. The discrete equation was deduced by control volume integral method, and realized by numerical method. The calculation results were consistent with test data. This indicated that the mechanism analysis was practical, physical model and mathematical model were reasonable. Finally, the numerical technique was used to investigate influence that different parameters on ablation rate. The relationship between oxygen percentage, pressure, depth of charred layer and ablation rate were obtained.