Numerical investigation on the transient transport and heat transfer characteristics of transpiration cooling with liquid phase change during coolant adjustment

Aimed at learning the variation law of injection pressure with coolant mass flux and promoting the active control of phase-change transpiration cooling, this study proposes a new transient mathematical model by simplifying the two-phase mixture model (TPMM) with the introduction of modified mixture enthalpy and enthalpy ratio. The smooth change with time of mixture enthalpy and enthalpy ratio improves the convergence and stability of TPMM. Experiment is first carried out to verify the accuracy of the new model. Then the two-phase flow and corresponding fluid-structure coupling heat transfer processes of transpiration cooling are studied with the new model under both steady and transient conditions. Besides, the relationship link from coolant adjustment, corresponding pressure and mass flux to the cooled wall temperature is discussed. The steady results show that injection pressure is closely related with phase change location, and the huge change of fluid kinematic viscosity and pumping effect of capillary force induces the non-linear variation of injection pressure with coolant mass flux. The transient results reveal that injection pressure changes with different laws when the mass flux increases and decreases. The changing speed of mass flux and scale of external heat flux also have a vital influence on the fluctuation of injection pressure, the faster the mass flow rate changes and the greater the heat flux is, more tempestuously the injection pressure varies.