Thermal analysis of RBCC engine at ejector, ramjet and scramjet modes

Heat transfer characteristics near the walls of the Rocket Based Combined Cycle (RBCC) whole flow path engine at typical operation conditions (rocket-ejector mode at Ma1.5, ramjet mode at Ma4.0, scramjet mode at Ma6.0) were numerically studied. The numerical model employed the SST k-ω turbulent model in the flow field and a threestep quasi-global chemical kinetics model for combustion simulation of C₁₂H₂₃which was selected as kerosene surrogate. It is found that the distribution surface heat flux in RBCC engine which serves a vital role in the process of TPS design has its unique characteristic at rocket-ejector mode, ramjet mode and scramjet mode, especially on the combustor wall, the reasons for the non-uniform thermal environment are that the mass flow rate of primary rocket and positions of combustion organization vary with operating modes. Among the three typical operation conditions, Ma6.0 has the highest surface heat flux, the averaged heat flux is 2MW/m². The heat flux distribution on the side wall is lower than on the top and bottom wall because the influence area of the primary rocket is limited which mainly effect the non-uniform distribution on the top and bottom wall. Another notable characteristic is that the cavity’s thermal environment is quite different with the combustor wall, and the maximum heat flux is often located at the trailing edge of the cavity which approximate to 5MW/m2, therefore, the TPS design of the cavity must consider this unique phenomenon. As concluding remarks, RBCC engine has a more complex surface thermal environment than ordinary scramjet engine, the TPS design must depend on a comprehensive and detailed analysis to obtain a high efficient of closed-loop cooling cycle.