During high-speed flight, severe aerodynamic heating is encountered by the vehicle, and the accurate identification and prediction of surface heat flux are regarded as essential requirements for the design and optimization of thermal protection systems. Real time feedback on the spatiotemporal evolution of active thermal protection systems such as transpiration cooling is difficult to obtain by conventional approaches, and complex internal processes including microporous permeation and gas liquid phase change introduce significant thermal lag effects. These effects further increase the difficulty of real time estimation and prediction and reduce the responsiveness of coolant dynamics in active thermal protection systems. In this study, a heat flux identification and rapid prediction method for transpiration cooling systems is proposed based on a Channel Attention Temporal U-Net model, in which spatial features are extracted by convolutional networks, temporal dependencies are modeled by convolutional long-Short-Term-Memory units, and channel features are adaptively calibrated through squeeze and excitation modules. Through this integrated structure, the accuracy of spatiotemporal heat flux modeling is enhanced and both the current heat flux and its future evolution can be predicted with high fidelity. It is shown that under typical transpiration cooling conditions a root mean square error of 0.0189 MW/m² is achieved by the proposed model, corresponding to an 84.7% reduction relative to the baseline U-Net model, and the prediction error within a 10−30 s forecast window is maintained within 2.5%. The influence of thermal lag on system performance is thereby alleviated, and improvements in accuracy, robustness, and computational efficiency are demonstrated, providing theoretical support and technical foundations for real time dynamic thermal management in high-speed vehicle active thermal protection systems.

During high-speed flight, the aircraft can utilize its own propellant to cool through the micro-hole jet to achieve active thermal protection. However, under high-temperature non-equilibrium conditions, the interaction between the compressible external flow and micro-jets involves complex processes including jet extrusion, mixing, and reactions, making the dominant mechanisms and influencing factors of micro-jet cooling highly intricate. In this study, a viscous wall boundary model for micro-jets was established, and numerical simulations of high-temperature non-equilibrium flow fields under micro-jet effects were conducted. The influence of jet hole diameter, velocity, and spacing on cooling performance were investigated. The simulations reveal the impact mechanisms of micro-jets on chemical reaction boundary layers, wall heterogeneous catalysis, and aerodynamic heating characteristics. The findings indicate that propellant micro-jet cooling under high-temperature non-equilibrium flow conditions is dominated by two key processes: boundary layer crowding and heterogeneous catalytic weakening. Specifically, the low-temperature micro-jet ejection crowds the boundary layer, altering its profile and reducing the temperature gradient near the wall, thus decreasing wall-normal heat conduction and achieving cooling. Additionally, the crowding-out effect of the low-temperature micro-jet promotes the outward displacement of near-wall O atoms, weakening the oxygen catalytic effect and reducing catalytic heat. Further parametric study shows that when the mass flow rate is constant, the heat reduction rate and cooling range decrease with the increase of jet hole size. When the area of the jet hole is constant, the micro-jet velocity is increased, and the heat reduction rate and cooling range are increased. When the mass flow rate is constant and the hole spacing is reduced, the peak value of the spanwise average heat reduction rate decreases, but the cooling range downstream of the hole increases, showing a more uniform cooling effect. These findings provide crucial theoretical support and technical guidance for the design and optimization of active thermal protection systems utilizing micro-jet cooling in future high-speed vehicles.

Reactive molecular dynamics simulation provides an important approach to elucidate the microscale heating mechanisms involved in high-temperature wall effects and to deepen our understanding of non-equilibrium aerothermodynamics of high-speed aircraft. However, microscale simulations that enhance the computational efficiency by artificially increasing the gaseous pressure often lead to discrepancies in reaction pathways and rate coefficients, thereby affecting the aerothermodynamics and causing the misunderstanding of reaction mechanisms. Using a molecular dynamics approach based on the ReaxFF force field, this investigation addresses the catalytic recombination reaction system of dissociated oxygen atoms on the surface of silica-based thermal protective materials. The primary objectives involve the computation and analysis of elementary reaction rates, surface coverages, and recombination coefficients under various gaseous pressure conditions. The purpose is to establish a quantitative correlation between the rate constants of elementary reactions and pressure, thereby elucidating the upper bounds of computational efficiency enhancement through pressure augmentation. The results indicate that pressure augmentation leads to a transition in the dominant reaction pathway from adsorbate-adsorbate interactions to gas-adsorbate interactions. Furthermore, it causes a deviation in the relationship between the rate constants of elementary reactions and pressure from the patterns observed under experimental/flight conditions. At 1200 K, within the pressure range associated with single-atom collisions, a consistent decrease in the rate constants of individual elementary reaction steps is observed as the pressure decreases. Among them, the rate constants of ER1～ER3 recombination exhibit a linear relationship with pressure. Specifically, the rate constants can be expressed as a power law function of pressure, with exponents of 1.10179, 1.01686 and 0.91654 respectively. The rate constants of LH1～LH3 recombination reactions display a logarithmic dependence on pressure, with significantly smaller pre-logarithmic factors compared to those observed in the non-single collision region. The rate constant of thermal desorption is exponentially related to pressure. Based on the microscale mechanism of catalytic reaction influenced by gaseous pressure, and with the stable relationship between elementary reaction rate constants and pressure, a constraint upper limit for artificially increasing pressure is proposed. The Knudsen number with the system height as the characteristic length should be greater than the magnitude of ${10}^2$ to ensure the gas-solid single collision. This investigation provides support for molecular simulation methods of gas-solid interface reactions and the accumulation of microscale catalytic data for thermal protective materials.