Two axially-staged moderate or intense low-oxygen dilution(MILD) configurations

based on cross-flow jet mixing and swirl mixing

were numerically and experimentally studied to compare their mixing performance from flow field pattern and species distribution

and to compare their combustion property from flame behavior and NO and CO emissions. The experiment fuel was methane and the heat load was regulated in the range of 16.2 to 25.9kW. The mixing between fuel and air stream is delayed in the cross-flow jet mixing configuration compared to the swirl mixing configuration

and thereby the recirculated hot flue gas preheats and diluts the fuel and air stream before spontaneous reaction in the former configuration. Compared to the swirl mixing configuration

higher flame lift-off height and more spatially distributed flame are observed in the cross-flow jet mixing configuration

of which flame behavior is also closer to MILD combustion. Furthermore

lower NO and CO emissions are observed for the cross-flow jet mixing staged combustor; at gas recirculation ratio of 0.5 and equivalence ratio of 0.6

the volume fractions of NO and CO in the flue gas are both 4×10-6.