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Nano-sized energetic particle as fuel additives is of great significance for liquid hydrocarbon fuels that will exhibit high-density and high-calorific value in high-speed propulsion systems. An experimental investigation has been conducted to determine the propulsive and combustion behavior of hydrocarbon fuels containing boron nanoparticles. In this study, nano-sized boron particles with average diameter of 20 nm are added into the basic fuel JP-10 and quadricyclane, respectively. They are then referred as slurry fuels and burned in the rocket combustor using pure oxygen as the oxidizer. With a wide range of excess oxidizer coefficients, three parameters characterizing the propulsion performance are employed to evaluate the effect of boron nanoparticles on hydrocarbon fuels. It is found that the boron-based slurry fuel showed superior density specific impulse. It is increased by 1.18% and 1.44% when the addition of boron particles with 10% mass fraction are added into the basic fuel JP-10 and quadricyclane, respectively. Combustion depositions of the boron-based slurry fuel located at different positions are then collected for deep analysis by means of the energy dispersive spectrometer, X-ray diffractometer, and scanning electron microscope. Comprehensive microanalysis results demonstrate that boron particles first combine with the C-element in the hydrocarbon fuel to form the boron carbide with a reticular structure, and then the boron carbide oxidizes to form block-shaped boron oxide. However, the surface boron oxide hindered the further reaction of the internal boron carbide, which limits the energy release of the boron particles and ultimately leads to the unsatisfactory combustion efficiency of the slurry fuel.

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The mixing process and distribution characteristics of a supercritical endothermic hydrocarbon fuel (EHF) jet injected into a supersonic crossflow were investigated by experimental and numerical methods, respectively. The schlieren system and acetone planar laser-induced fluorescence (PLIF) optical system were used to capture the flow-field structural characteristics and instantaneous plume. The mixture and real gas models were employed to calculate the interaction of a transverse jet and supersonic crossflow and reveal a good accuracy with the experimental results. The mixing efficiency and total pressure loss were analyzed based on the numerical results. The results indicate that the supercritical-state EHF directly changes to a gaseous state as it enters the supersonic crossflow from the injector. The EHF jet plume boundary increases with the increasing momentum flux ratio (q). As the streamwise and spanwise distance increases, the traverse heights and expand width increase, and the EHF jet plume presents a semicircle shape in the cross-sectional plane. With the increase in the traverse direction, the concentration distribution shows a fast and then slow power exponential decreasing law; the highest concentration point starts from the near-wall region and rises in the transverse direction with the flow distance increasing. For the same injection condition, the higher the inflow Mach number, the higher the mixing efficiency. For the same Ma, the mixing efficiency is better for the case with low injection pressure and high injection temperature. The total pressure loss is greater in the higher Ma, and high injection pressure conditions cause greater total pressure loss.