Regenerative-Cooling Heat-Transfer Performance of Mg/CO2 Powder Rocket Engines for Mars Missions

Aimed at the problem of thermal protection due to the long-time operation of Mg/CO2 rocket engines under high pressure and heat flux, a regenerative-cooling heat-transfer model is established that considers liquid-CO2 phase change under engine heat flow. How the height-to-width ratio of the cooling channel and the coolant mass flow rate influence the heat-transfer performance is studied, and the results show that the CO2 experiences liquid-phase, two-phase boiling, and gas-phase heat transfer. It is necessary to carry out division-of-region design to avoid membrane-boiling or gas-phase heat transfer in the cooling channel for a long time. When the coolant enters the nuclear boiling stage of two-phase heat transfer near the throat, the heat-transfer coefficient reaches its maximum value, as does the temperature of the corresponding combustor wall, which is 918.1-1012.3 K. When the CO2 flow rate exceeds 5 g/s, the continuous increase of coolant flow has a limited increase in the heat-transfer coefficient of liquid and two-phase heat transfer, but continuing to increase the CO2 flow rate can expand significantly the occurrence region of phase-change heat transfer, so as to bring better heat transfer.