Combustion Behavior of Hydrocarbon/Boron Gel-Fueled Scramjet

Abstract

Using energetic boron particle as an additive to hydrocarbon gel fuels is an effective method to improve the performance of a scramjet/ramjet system. To evaluate the combustion characteristics and application performances of boron-containing gel fuel in an airbreathing scramjet, a comprehensive experimental study was carried out on the injection, atomization, combustion, solid deposition, and wall heat flux of JP-10 wt % B gel fuel and JP-10 gel fuel in a directly connected scramjet combustor. The simulated air entered the combustor at a Mach number of 2 and a total temperature of 1700 K, while the gel-fuel equivalence ratio varied between 0.6 and 1.0. The results demonstrated that the volume-controlled fuel supply system driven by electric motor and gas-assisted injector can realize the stable injection and efficient atomization of highly viscous non-Newtonian gel fuels. Two optical diagnostic methods proved that the boron-containing gel fuel is capable of achieving stable combustion in the scramjet combustor with single-cavity configuration. Based on the measurement of wall pressure along the flowpath, the combustion efficiency of the two gel fuels at different equivalence ratios was calculated using the one-dimensional impulse analysis method. The combustion efficiency of the JP-10 + B gel fuel is 3.51% higher than that of the JP-10 gel fuel, while the addition of boron particles increases the density specific impulse of gel fuel by 8.42%. These results indicated that the addition of boron particles indeed showed a positive effect on combustion characteristics and engine performance. Finally, the wall deposition phenomenon found in the combustion of boron-containing gel fuel was introduced, and the reason for about 22% increase in wall heat flux caused by the addition of boron particles was simply analyzed.