Abstract: The effect of twice air-entering on the combustion efficiency of afterburner and the ablation environment of inner wall was studied for the design of air-inlet of solid rocket ramjet afterburner. The standard k-ε model, the eddy dissipation model and the King boron particle ignition model were adopted to simulate the multiphase combustion in the single and twice air-entering afterburners. Through comparative analysis，the following conclusions were drawn as follow. The twice air-entering can coat the mixed gas and squeeze it inward to compress the high temperature area and changeg the oxygen distribution，which reduces the area of the high temperature inner wall，decrease the temperature of the low temperature wall，and cut down the number of condensed phase particles close to the wall，thereby weakening the thermal ablation，oxidation and erosion of condensed particles in the inner wall.Because of the greater kinetic energy loss which reduces the airflow velocity close to the inner wall，it also weakens the airflow scouring effect.Thus the ablation environment in the inner wall of afterburner is improved. However，twice air-entering has little effect on the combustion efficiency，and the total combustion efficiencies of afterburners with single air-entering and twice air-entering reach 80.68% and 80.18%, respectively. Considering the two aspects of combustion efficiency and ablation environment of the inner wall, it can be considered that twice air-entering is better than once air-entering.

Key words: solidrocketramjet, afterburner, twiceair-entering, combustionefficiency, ablationenvironmentofinnerwall