Numerical analysis of heat transfer and flow characteristics of a precooler with a methanol cracking reaction

For hydrocarbon-fueled turbojet engines with a precooling technology, the precooling technology with a low-temperature endothermic fuel is a great potential way to solve the problem of sharp reduction of the specific impulse caused by the insufficient heat sink of the hydrocarbon fuel. To study the heat transfer and flow characteristics of a precooler with a fuel endothermic reaction, methanol is chosen as the low-temperature endothermic fuel, and the numerical model of a precooler of tube bank arranged in-line is built, which considers the methanol with a cracking reaction. The results indicate that the methanol cracking reaction can enhance the cooling effect to the air by increasing the heat transfer temperature difference. When the cracking rate is not more than 20%, the cooling effect to the air increases and the cracking rate decreases with the methanol mass flow rate. When the longitudinal pitch-to-diameter ratio varies between 1.25 and 2.50, the cooling effect and the cracking rate increase with its increase, which is not conducive to the compactness of the precooler. When the transverse pitch-to-diameter ratio varies between 1.25 and 2.00, the cooling effect and cracking rate increase with its decrease but bring significant pressure loss.