Aiming to efficiently simulate the transient process of transpiration cooling with phase change and reveal the convection mechanism between fluid and porous media particles in a continuum scale,a new two-phase mixture...Aiming to efficiently simulate the transient process of transpiration cooling with phase change and reveal the convection mechanism between fluid and porous media particles in a continuum scale,a new two-phase mixture model is developed by incor-porating the local thermal non-equilibrium effect.Considering the low-pressure and high overload working conditions of hypersonic flying,the heat and mass transfer induced by capillary and inertial body forces are analyzed for sub-cooled,saturated and super-heated states of water coolant under varying saturation pressures.After the validation of the model,transient simulations for different external factors,includ-ing spatially-varied heat flux,coolant mass flux,time-dependent external pressure and aircraft acceleration are conducted.The results show that the vapor blockage patterns at the outlet are highly dependent on the injection mass flux value and the external pressure,and the reduced saturation temperature at low external pressure leads to early boiling off and vapor blockage.The motion of flying has a large influence on the cooling effect,as the inertial force could change the flow pattern of the fluid inside significantly.The comparison of the results from 2-D and 3-D simulations sug-gests that 3-D simulation shall be conducted for practical application of transpiration cooling,as the thermal protection efficiency may be overestimated by the 2-D results due to the assumption of an infinite width length of the porous plate.展开更多
基金This research is supported by the National Natural Science Foundation of China-Deutsche Forschungsgemeinschaft Mobility Programme(M-0368).
文摘Aiming to efficiently simulate the transient process of transpiration cooling with phase change and reveal the convection mechanism between fluid and porous media particles in a continuum scale,a new two-phase mixture model is developed by incor-porating the local thermal non-equilibrium effect.Considering the low-pressure and high overload working conditions of hypersonic flying,the heat and mass transfer induced by capillary and inertial body forces are analyzed for sub-cooled,saturated and super-heated states of water coolant under varying saturation pressures.After the validation of the model,transient simulations for different external factors,includ-ing spatially-varied heat flux,coolant mass flux,time-dependent external pressure and aircraft acceleration are conducted.The results show that the vapor blockage patterns at the outlet are highly dependent on the injection mass flux value and the external pressure,and the reduced saturation temperature at low external pressure leads to early boiling off and vapor blockage.The motion of flying has a large influence on the cooling effect,as the inertial force could change the flow pattern of the fluid inside significantly.The comparison of the results from 2-D and 3-D simulations sug-gests that 3-D simulation shall be conducted for practical application of transpiration cooling,as the thermal protection efficiency may be overestimated by the 2-D results due to the assumption of an infinite width length of the porous plate.
