Numerical study of flame characteristics in a reduced-diameter vortex combustor

In this paper, the combustion process in a vortex combustor, which is composed of two volutes, a center nozzle, and a reduced-diameter cavity, is studied by CFD simulation. The combined effect of the center jet and cyclone vortex on the flame structure is revealed by analyzing the fuel transport mechanism and flow field characteristics. Results show that under different fuel and air supply conditions, two typical flame structures may form inside the combustor. When the equivalence ratio is 0.5 and the power is 40 kW and 50 kW, Flame A will be produced, which is mainly distributed near the center nozzle. Under other conditions, Flame B will be generated, which is a two-layer structure with an inner layer surrounding the center nozzle and an outer layer near the wall. The construction of Flame B inside the reduced diameter vortex combustor is mainly attributed to the strong cyclonic flow, which breaks the recirculation in the flow field, transporting the fuel to the near wall region and promoting secondary combustion. At this time, the methane burn rate can be as high as 99 %, which is 10 % higher than the methane burn rate of Flame A.