Investigations on Flow and Heat Transfer Characteristics of Supercritical Carbon Dioxide Inside Scramjet Cooling Channel Under Different Arrangements

To satisfy the electricity demands and further improve the cooling performance of scramjets, the supercritical CO2 Brayton cycle is adopted as a promising cooling and power supplying scheme. However, with the extremely high heat flux level of MW/m2, a cooling channel featuring a rectangular cross-section with non-uniform heat flow and different positions of the heated wall relative to the direction of gravity make the flow and heat transfer characteristics of supercritical CO2 within scramjet cooling channel extremely complex. In this study, the effects of different angles of the heated wall normal direction relative to the direction of gravity (θ) on the flow and heat transfer behavior of supercritical CO2 within a scramjet cooling channel are comprehensively investigated. The results show that the spanwise heat transfer coefficient on the heated wall decreases while on the opposite wall it increases as θ increases. Moreover, the overall heat transfer performance is insensitive to variations in θ, but the heat transfer characteristics on different walls are sensitive to variations in θ. Moreover, the cases with lower θ provide better heat transfer performance for the heated wall, which is more significant for scramjet cooling due to having the highest heat load. In detail, the averaged HTC on the HW of θ = 180 deg for G = 900 kg/(m2s) is reduced by 11.79% in comparison to that of θ = 0 deg, while it is enhanced by 18.70%, 6.39% and 6.39% for the OW, LW and RW, respectively.