A review of regenerative cooling technologies for scramjets

Highlights: • The engineering application of regenerative cooling in scramjets are reviewed. • Characteristics of the regenerative cooling in scramjets have been discussed. • In-depth research on the mechanisms of heat transfer deterioration is needed. • The lattice structures and nanoparticles are promising but need further research. Regenerative cooling technologies are considered as an effective and realizable thermal protection method in scramjets. In this paper, a review of regenerative cooling on the engineering application for the combustion chambers of scramjets is carried out. The research status of regenerative cooling including supercritical heat transfer and hydrocarbon fuel coking is summarized. Furthermore, the optimized schemes of regenerative cooling channels based on unconventional structures and advanced manufacturing technologies are discussed in detail. At present, the cooling capacity of regenerative cooling is still insufficient for scramjets on account of the complicated working environment in the combustion chamber and the limited mass flow rate of coolant. The supercritical heat transfer in cooling channels is strongly influenced by the thermophysical properties of the coolant, probably resulting in heat transfer deterioration. In this case, further investigations are needed to reveal the mechanisms of heat transfer deterioration. Besides, coking of hydrocarbon fuel will resist the heat exchange between the coolant and cooling channels. To suppress the carbon deposition, deoxidizing fuel, fuel additives, surface treatment, and coating can be employed. The additive manufacturing lattice structure and the nanoparticles on the heat transfer surface extend the heat exchange area and increase the turbulence intensity in the cooling channel, which could be applied in the reused scramjets in the future.