Numerical analysis of convection/transpiration cooling

An innovative concept utilizing the natural porosity of refractory-composite materials and hydrogen coolant to provide convective and transpiration cooling and oxidation protection has been numerically studied for surfaces exposed to a high-heat-flux, high-temperature environment such as hypersonic vehicle engine combustor walls. A boundary-layer code and a porous media finite difference code were utilized to analyze the effect of convection and transpiration cooling on surface heat flux and temperature. The boundary-layer code determined that transpiration flow is able to provide blocking of the surface heat flux only if it is above a minimum level due to heat addition from combustion of the hydrogen transpirant. The porous media analysis indicated that cooling of the surface is attained with coolant flow rates that are in the same range as those required for blocking.