Numerical investigation on the effects of porous cone parameters on liquid transpiration cooling performance

Owing to the huge boiling heat transfer coefficient and phase change latent heat, which implies a high cooling capability and a small coolant consumption, transpiration cooling with liquid phase change has been widely recognized as a promising thermal protection approach for hypersonic vehicles. However, the processes of coolant flow, heat absorption and phase change within porous media are so complicate that accurate numerical simulations are difficult. To overcome this issue, in the present work, the mathematical model of liquid transpiration cooling is simplified through equivalent mathematical transformations without invoking any additional assumptions. Based on the modified model, liquid transpiration cooling processes within a wedge-shaped porous cone are simulated under a freestream condition of 12.0 Mach number and 30 km flight height and the effects of solid conductivity, particle diameter and thickness of the porous layer on cooling performance are lucubrated. The results indicate that there are remarkable differences between the effects of these parameters on liquid and gaseous transpiration cooling. This is mainly caused by the fact that fluid-solid heat exchange is conducted in entire porous region in gaseous transpiration cooling while it is mainly achieved in a very thin two-phase region in liquid transpiration cooling.