Thermodynamic analysis of boron powdered scramjet engine based on supercritical hydrocarbon fuel fluidization technology

To fully harness the high heat value of boron fuel and advance propulsion systems for aircraft requiring extended range and enhanced thrust, this study proposes a novel combustion organization scheme for boron-powdered scramjet engines based on supercritical hydrocarbon fuel fluidization technology. Addressing the challenges of difficult ignition and low combustion efficiency, the approach utilizes cracked gases generated from hydrocarbon fuel after regenerative cooling to fluidize boron powder and promote ignition and combustion. The analysis is based on thermodynamic cycle modeling for a scramjet operating at Mach 6. Accounting for the pressure increase caused by the shock trains and the actual fuel heat release. Furthermore, a one-dimensional evaluation model is developed to analyze heat release from the phase change of gaseous boron oxide in the nozzle following combustion. Results indicate that phase change significantly increases the exit gas temperature, while the velocity gain remains relatively small. Compared with the scenario neglecting the phase change process of boron oxide, the real phase change process leads to a maximum improvement of 6.6 % in both specific impulse and specific thrust. The study also evaluates the influence of hydrocarbon fuel equivalence ratio and finds that an optimal ratio of 0.15 balances fluidization stability and engine performance, achieving a density-specific impulse gain of more than 69 % compared to traditional hydrocarbon-fueled engines. This work provides new insights into the thermal effects of boron oxide phase change, informs nozzle design considerations, and offers a promising direction for the practical application of boron powdered fuels in air-breathing propulsion systems.