Study on combined thermal protection scheme integrating supercritical CO2 regenerative cooling and fuel film cooling used for scramjet engines.

Supercritical CO 2 closed-Brayton-cycle demonstrates considerable application potential on hypersonic vehicles, effectively addressing power supply issues during prolonged flights. However, the CO 2 flow rate is strictly limited by the cycle's cooling source (aviation kerosene), rendering traditional regenerative cooling inadequate for sufficiently cooling the scramjet engine. To address this challenge, this study proposes an integrated cooling scheme that combines regenerative cooling, ceramic thermal-protective layer, and fuel film cooling. A two-dimensional coupled numerical model was developed, simultaneously considering the convective heat transfer of supercritical CO 2 and the shear mixing of supersonic fuel film. The results indicate that the high-enthalpy gas imposes an extreme aerodynamic heat load on the regenerative cooling channel wall, resulting in a notable deterioration in heat transfer for supercritical CO 2. Implementing kerosene film cooling within the combustor can effectively mitigate the abnormal heat transfer behavior of supercritical CO 2 and significantly reduce viscous dissipation heat within the gas boundary layer. By optimizing the fuel film injection layout, this combined cooling scheme reduced wall heat flux by 43 % and temperature by over 400 K compared to traditional regenerative cooling, thus providing effective thermal protection for the scramjet engine. • Coupled numerical simulation between S-CO 2 cooling channel and scramjet is achieved. • Heat transfer deterioration occurred in the S-CO 2 cooling channel under aero-heating. • Even with a ceramic insulation layer, S-CO 2 cooling channel can't cool the scramjet. • Supersonic fuel film mitigates the heat transfer deterioration in the S-CO 2 channel. • Double fuel film spraying combined with S-CO 2 channel is an effective cooling scheme. [ABSTRACT FROM AUTHOR]