By analyzing the characteristics of charring layers obtained in ablation motor and simulating erosion motor

the forming and consumption mechanisms of charring layer were analyzed

and ablation model considering the porosity of charring layer was developed.With the model

the charring layer was described as gas-saturated porous media with dense layer and porous layer

thermo-chemical reaction and gas diffusion existed in the pores of charring layer

and the compact structure of charring layer was formed by sediment of decomposition gas.Based on numerical investigation on flow and convection in porous media

a numerical model was presented to simulate the ablation process

and the calculated ablative rates

mass loss rates and the structures of charring layer agree with experimental results.The ablation model has been proved to simulate the process of the thermo-chemical ablation reasonably

and to provide the numerical method for all ablation models considering the thermo-chemical ablation and mechanical erosion.