Numerical investigation on the characteristics of coolant flow, heat absorption and phase change in transpiration cooling process

Abstract

Transpiration cooling using liquid water as coolant has been confirmed as a promising thermal protection method due to the huge phase change latent heat. A multi-region numerical strategy is developed and presented in this paper, to simulate directly the liquid transpiration cooling process within a wedge-shaped porous cone. An experiment was conducted to validate the numerical strategy. Using the validated strategy, five series of numerical simulations under different coolant mass fluxes were carried out. The numerical results revealed some interesting and valuable characteristics of fluid flow, heat absorption and phase change of liquid coolant in the porous cone and on the impermeable surface. When the liquid coolant is vaporized incompletely in the porous region, one can find two interesting phenomena: 1) A large amount of coolant flow towards the end of the porous cone, while only a small part of coolant can be transferred into the leading edge region; 2) An increase in inlet coolant mass flux causes a decrease of the coolant ejected from the leading edge. However, these phenomena are absent when the liquid coolant is vaporized completely in porous region. Another important phenomenon demonstrated in this work is an additional thermal protection effect on the downstream impermeable surface. This additional thermal protection effect increases with the inlet coolant mass flux, but at the price of a larger wastage of coolant phase change latent heat.