Combustion characteristics of a reverse-cross-flow combustor

The effect of fuel-to-air jet momentum flux ratios (varied from 0.1 to 5.1) in a 6.25 kW Reverse-Cross-Flow (RCF) combustor is investigated at a maximum thermal intensity of 40 MW/m3-atm using methane fuel. Reaction zone is characterised by imaging OH radicals using planar laser-induced fluorescence (OH-PLIF) technique. Reynolds-averaged Navier-Stokes (RANS) simulations are performed at an equivalence ratio of 0.8 using Eddy Dissipation Concept (EDC) model for turbulence-chemistry interactions with detailed reaction mechanism (GRI-Mech 3.0). Numerical results show a qualitative match with the experimental results for averaged OH intensity distribution and NOx and CO emissions. Air jet is observed to deflect more with increase in fuel-to-air jet momentum flux ratio. Flame-front is observed to be located at the periphery of the air jet due to mixing of reactants and hot burned products in the shear layer. Instantaneous OH-PLIF data suggest that the flame-front location changes considerably with time. Both numerical and experimental results show increase in CO emissions and reduction in NOx emissions with increase in fuel-to-air jet momentum flux ratio. This may be linked to unfavorable residence time distribution, despite better mixing at high fuel injection momentum.