Effect of kerosene injection states on mixing and combustion characteristics in supersonic combustor at high equivalent ratio

Abstract

Previous studies have found that the difference in combustion characteristics of gaseous and liquid kerosene injection in supersonic combustor is sensitive to the equivalent ratio. In this paper, the previous work is extended to a high equivalent ratio to gain a deeper understanding of the effect of injection states on combustion performance via numerical computation. The simulation results match well with the experiments and demonstrate that due to the different jet structures, the cavity shear layer of liquid injection penetrates deeply into the cavity, forming two recirculation zones therein. As a result, the majority of droplets enter the cavity and exist at a low streamwise velocity, which is favorable to droplet vaporization and combustion. Therefore, when the liquid fuel is injected at a high equivalent ratio, the fuel residence time increases, the droplet evaporation distance decreases, and the fuel vapor accumulates in the cavity. Compared to the gaseous injection with the same equivalent ratio, the liquid injection exhibits similar mixing efficiency in the cavity but slightly higher mixing efficiency in downstream divergent sections. This unique fuel distribution causes the liquid injection to have a higher combustion efficiency than that of the gaseous injection. The weak advantage in mixing and combustion makes the liquid injection capable of compensating for the effects of the fuel atomization and evaporation on combustion performance. As a result, the combustion structure and static pressure distribution of liquid injection with the high equivalent ratio is similar to those of the gaseous injection.