Numerical investigation on transpiration cooling with coolant phase change under hypersonic conditions

Owing to the huge phase-change latent heat, transpiration cooling using liquid coolant has been widely recognized as an effective thermal protection approach for hypersonic vehicles. This paper presents a modified local thermal non-equilibrium two-phase mixture model (LTNE-TPMM), and develops a multi-region numerical strategy to solve the coupled problems of internal heat and mass transfer in a porous cone with the external aerodynamic heat/force. The modified LTNE-TPMM and numerical strategy are validated by the experimental data obtained under a supersonic condition. Using the validated model and numerical strategy, numerical simulations are carried out under the condition of flight Mach number 7.0 and altitude 26.5 km, to study the mechanisms and analyze the performances of the transpiration cooling with liquid phase-change in a porous wedge-shaped nose cone. The numerical results revealed some interesting, valuable phenomena generated in liquid phase-change process, including the coolant movement and the distributions of temperature, pressure, saturation within the porous cone. The coolant mass flux along the radial direction of the cone decreases gradually in the vapor region, and then decreases rapidly at the beginning of two-phase region, but increases in the liquid region. Another important discovery is that the relation between coolant injection pressure and mass flow rate is not one-to-one. One injection pressure may correspond to multiple mass flow rates. (C) 2018 Elsevier Ltd. All rights reserved.