Parametric analysis on combustion characteristics of hydrocarbon fueled parallel wall-jet inside a supersonic combustor

Using hydrocarbon fuel as cooling film is one of the most promising ways to thermally protect supersonic combustors and it can also be considered as a special combustion process. Parametric analysis is very important for increasing combustion efficiency of this special combustion process which is a parallel fuel wall-jet, and it is numerically investigated in this paper. It is found that, for parallel wall-jet combustion lacking near-field mixing enhancement because of the thermal protection purpose, decreasing equivalence ratio can lead to a significant increase in combustion efficiency since the wall-jet combustion efficiency is only determined by the shear mixing process. Moreover, under the constant equivalence ratio, increasing injection height from 0.67 mm to 2 mm can only slightly increase the combustion efficiency by 1.5% although it can reach a much better cooling performance. It is worth mentioning that, the effects of mainstream parameters on combustion efficiency present a step trend, self-ignition will occur as the mainstream temperature or Mach number reaches a certain value. And afterward, keep increasing mainstream temperature has little effect on the combustion efficiency since the mixing process keeps almost unchanged. Whereas, continuous reduction of mainstream Mach number will improve combustion efficiency by significantly enhancing mixing.