An experimental study on the cracking heat sink behavior of n-decane and RP-3 under supercritical pressures

The intensifying heat load on hypersonic aircraft has promoted the advancement of active cooling technologies utilizing endothermic hydrocarbon fuels. The wide range heat release characteristics of fuel are the key factors for further expanding the application scenarios and Mach numbers of regenerative cooling technology. This study performed experimental measurements of the heat sink characteristics of supercritical n-decane and RP-3 in a 1000 mm long GH3128 microtube with an outer diameter of 3 mm and an inner diameter of 2 mm, covering a range from room temperature to beyond a 50 % conversion rate at 3 to 6 MPa. The initial temperature of the cracking reaction for n-decane and RP-3 is respectively about 850 and 900 K, and the heat sink augment rate in the cracking reaction region is significantly greater than that in the uncracking region. The fuel undergoes a secondary deep cracking reaction when the conversion rate exceeding about 30 %, accompanying with the reduction of the product alkene/alkane ratio and fuel heat sink increase rate. The importance of residence time and reaction path to the heat sink release accounts for various proportions in different temperature ranges. The definition method of physical and chemical heat sink is established, and the differences in heat sink characteristics of the two fuels are compared. The results of this work will deepen the understanding of the wide-range heat sink characteristics of fuel and provide strong data support for the design of regenerative cooling channels for hypersonic aircraft.