Research status of active cooling of endothermic hydrocarbon fueled scramjet engine

The active cooling with endothermic hydrocarbon fuel is proved to be a very effective approach for scramjet thermal protection. This article has summarized the research status of active cooling of endothermic hydrocarbon fueled scramjet engine from the following five aspects, cooling capacity and heat sink measurement, thermal and catalytic cracking, coking suppression, heat transfer characteristics, and injection, mixing, ignition, and combustion performance, and suggestions on the further study of active cooling of endothermic hydrocarbon fueled scramjets are put forward. The total heat sink of endothermic hydrocarbon fuel is found to be sufficient for scramjet cooling as the additional chemical heat sink is generated from cracking reactions, and catalytic cracking is proved to be better, because of its low cracking starting temperature, high conversion percentage, and good selectivity. As for coking mitigation, approaches are usually made from eliminating the oxygen dissolved in the fuel, reducing the amount of coking-foregoing substances, and doing some special treatments on the metal surface. The heat transfer of endothermic hydrocarbon fuels presents two enhancements. The first one is related to the variation of parameters near the critical point while the second one is a result of cracking reactions. The cracked products are proved to have better performance of injection, mixing, ignition, and combustion, and this is especially attractive for scramjets as effective mixing and stable ignition and combustion has always been difficult.