Research on the influence of nano-metal additives on the combustion performance of kerosene in a wide-range ramjet combined engine

Metals and metal hydrides are considered promising energetic additives for conventional liquid hydrocarbon fuels because they can significantly increase the energy density of the base fuel while reducing its ignition delay. This study reports a thermodynamic cycle analysis model of a rocket-based combined-cycle (RBCC) engine based on the stream thrust analysis method and parameters from a designed inlet with a wide range of working capacities. The model was used to study the influence of four different metal-based additives, namely, Al, B, aluminum hydride (AlH 3 ), and ammonia borane (BH 3 NH 3 ), on the theoretical performance of an engine under Mach 2 to 8 conditions. A freejet test under Ma2 flight conditions was used to evaluate the practical combustion characteristics of the JP-10+nano-boron (n-B) gel fuel in an RBCC engine. Theoretical results indicated that the specific impulse of JP-10 decreased after adding different additives, whereas the combustion temperature, density-specific impulse, and specific thrust increased. Moreover, BH 3 NH 3 , B, and Al were identified as the best additives in terms of the specific impulse, density-specific impulse, and specific thrust, respectively. The Ma2 freejet test adequately considered the ignition and stable combustion of the JP-10+20 wt% n-B gel fuel in the RBCC. The results indicated that when the fuel mass flow rate was consistent with that of the RP-3 control group, the density-specific impulse of the gel fuel was 18.3% higher, whereas the internal pressure and thrust of the engine were slightly lower. The results derived from the theoretical model were generally consistent with those of the freejet experiment, verifying the rationality of the theoretical model for estimating the influence of metal-based additives on engine performance. This study is expected to open new frontiers in fuel research, paving the way for new and interesting applications in various fields.