| Scramjet encounters serious thermal environment problems because of the high stagnation temperature of the incoming air and high load coming from supersonic combustion.In order to ensure the safety and durability of scramjet engines,active regenerative cooling technology,which uses the chemical absorption capacity of steam reforming reaction of supercritical hydrocarbon fuel to cool the engine,has attracted wide attention.Mastering the heat transfer characteristics of the steam reforming process of hydrocarbon fuel is the core to improve the cooling capacity of hydrocarbon fuel further.It is also the theoretical basis for the design and optimization of engine cooling system.Therefore,researches on the heat transfer characteristics of the steam reforming process of supercritical hydrocarbon fuel are carried out.A numerical model for heat transfer in the regenerative cooling flow of scramjet hydrocarbon fuel is established.The thermal properties calculation method and the selected numerical calculation method are validated respectively.Results show that the chemical reaction rate affects the heat transfer coefficient distribution.The heat transfer coefficient distribution in the whole steam reforming process is more complicated than that in the case of heat cracking al one.In order to maintain a better heat transfer effect,the distribution of water should be reasonably regulated.The influences of the critical parameters of the cooling system,such as water content,heat flux and working pressure,on the flow and heat transfer characteristics in the whole steam reforming process are analyzed.Results show that The results show that the amount of water should be regulated reasonably,and more water is not conducive to heat exchange in the later stage of thermal cracking reaction,so water should be allocated reasonably.The heat flux will affect the heat transfer coefficient distribution.In order to regulate the convective heat transfer in the cooling channel,the amount of water added should be different under different heat flux conditions.When the working pressure is different,the residence time of the fuel in the tube is different.Although the chemical reaction rate distribution is similar,the reaction rate is different,so the heat transfer coefficient is different.The flow and heat transfer characteristics in the whole steam reforming process in the three-dimensional rectangular channel are analyzed.Results show that in the three-dimensional rectangular channel,the heating wall has a noticeable influence on the development of the thermal boundary layer at the inlet under the condition of high heat flux.In contrast,the sidewall has no apparent impact on the development of the thermal boundary layer. |
