Investigation of kerosene supersonic combustion performance with hydrogen addition and fuel additive at low Mach inflow conditions

Abstract

Stable and efficient combustion is critical for low Mach starting stage of Dual-Mode Scramjet. In this paper, basic experimental validation and three-dimensional simulation of hydrogen addition and fuel additive effects on kerosene supersonic combustion performance were conducted under flight Mach 3.8 inflow conditions. Hydrogen addition was injected independently and the additive effects were simulated by the method of reducing activation energy. The simulation results are well-agreed with the experimental measurements from hydrogen addition cases and 20%-vol additive cases, validating the numerical method and models employed. The relative activation energy needed for well simulating 20%-vol additive effects tends to be higher than the theoretical prediction and also different by equivalence ratios. The heat release is intensified by either hydrogen addition or fuel additive, resulting in higher temperature-rises and pressure-rises, and more OH radicals for combustion enhancements at low-temperature conditions. An appropriate small amount of hydrogen addition (ERH < 0.08) can promote kerosene pre-evaporation and combustion heat release to achieve higher combustion efficiency; a large amount of hydrogen addition exhibits a competitive mechanism with kerosene cracking and CO oxidation conversion, also reduces the degree of diffusive mixing. Either the same small amount of hydrogen addition or fuel additive, more significant enhancement effects can be observed at the lower equivalence ratio of kerosene, due to the increased heat release induced flame stabilization and combustion mode transition. Compared with hydrogen addition, combustion efficiencies with increasing additive effects are increased monotonously to a higher level when kerosene equivalence ratio of ERK = 0.53, whereas lower efficiencies when ERK = 0.43.