Cooling capacity optimization of hydrocarbon fuels for regenerative cooling

•A multi-physical model by coupling the catalytic reactions has been established.•The results of parametric simulation reveal the optimization route.•The chemical route with ethylene and hydrogen gives heat sink value of 5.3 MJ/kg.•Coking can be limited by reducing the temperature and concentration of propene. As an effective method for heat management of hypersonic vehicles, regenerative cooling faces a severe problem of insufficient cooling capacity under high-speed conditions. Aiming to increase the cooling capacity of a given fuel, we conducted an optimization study by considering the influence of working conditions, chemical kinetics, and chemical routes. Via establishing a framework of multi-physical simulation by coupling the catalytic reactions with complex heat transfer process from subcritical to supercritical status, we conducted a parametric study of the effects of working conditions (i.e., inlet temperature and inlet velocity) to reveal the influence of physical heat sink, and different chemical kinetics and chemical routes to optimize the chemical heat sink. As a limiting case study, the surface coking process was also investigated. With the consideration of both physical and chemical heat sinks, the regenerative cooling capacity of a hydrocarbon fuel can be effectively increased via proper optimization. Using n-Decane as an example, a total heat sink of 2.5 MJ/kg is obtained under typical working conditions. A maximum heat sink of 5.3 MJ/kg could be obtained by engineering chemical routes with ethylene and hydrogen as the final cracking products, under inlet conditions of 473 K and 0.042 m/s. Results also reveal that it is essential to reduce the temperature of the wall to minimize carbon deposition. For practical applications, careful consideration of the synergies among the inlet conditions, reaction kinetics and routes, and coking should be performed to maximize the cooling capacity of a hydrocarbon fuel.