Spray, flowfield, and combustion characteristics of an external mixing atomizer in a novel cavity-swirler-based combustor

This paper presents an investigation into the performance of two external mixing atomizers designed for a novel cavity-swirler-based combustor, with the aim of achieving high combustion efficiency and uniform outlet temperature distribution. Experimental and numerical analyses were conducted to study the spray characteristics of the atomizers, including the Sauter mean diameter (SMD) and spray angle. The flow field, combustion efficiency, outlet temperature distribution, and pattern factor of the two atomizers were examined under atmospheric pressure and a temperature of 473 K. The results show that the external mixing prefilming atomizer (case-1) exhibits larger SMD and spray angle compared to the external mixing pressure-swirl atomizer (case-2). Furthermore, case-1 demonstrates higher combustion efficiency than case-2 under pilot-only fueling conditions, which is attributed to the larger wake regions achieved by case-1. Interestingly, under pilot-main fueling conditions, case-2 achieves higher combustion efficiency than case-1. This is due to the smaller SMD and longer residence time achieved by case-2. Moreover, case-1 demonstrates more uniform outlet temperature distribution and smaller pattern factor than case-2. This is mainly attributed to the large-scale axial vortex generated by case-2, which significantly improves the mixing intensity between cavity and mainstream.