: Rocket-based combined cycle (RBCC) engines operating across a wide Mach-number range (Ma 4-8) face dual challenges of severe aerodynamic heating and high onboard power demand. Conventional hydrocarbon-fuel cooling is limited by the coking-temperature threshold, while near-critical supercritical CO2 cycles may encounter strong property variation and control difficulty near the pseudo-critical region. This paper numerically assesses an integrated third-fluid cooling and power-generation concept using a binary helium-xenon (He-Xe) mixture. A coupled system-level model, linking RBCC internal ballistics, temperature-dependent mixture properties, an Eckert reference-enthalpy heat-transfer model, and closed Brayton-cycle thermodynamics, is established to evaluate cooling and shaft-power trends. Submodel-level verification checks are added for mixture properties, cooling-channel heat transfer and pressure loss, and the Brayton-cycle power boundary. The results quantify the tradeoff among mixture molar mass, turbomachinery compactness, and micro-channel heat-transfer performance. The 31.5 g/mol He-Xe mixture provides the best compromise among the investigated mixtures under the modeled constraints. The quasi-steady operating-point simulations indicate a passive quasi-steady load-following trend: as the flight Mach number increases from 6 to 8, the higher thermal load is accompanied by increased coolant-flow demand and larger Brayton-cycle shaft-power output. Compared with near-critical sCO 2 -based third-fluid concepts, the He-Xe gas mixture exhibits smoother gas-phase property variation over the investigated temperature range, which may reduce the risk of severe local pinch-point constraints under the modeled conditions. This study provides a system-level reference for integrated thermal management and waste-heat recovery in hypersonic RBCC engines.
Zhao et al. (Mon,) studied this question.
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