Combustion characteristics of coaxial nonpremixed flames for low heating value gases

In this study, the combustion characteristics of low heating value gases (LHVGs) consisting of methane, propane, and nitrogen are investigated experimentally and numerically. For the experiment, a coaxial non-premixed jet-type burner is used to study the flame stability limit and flame length. In order to investigate the effects of the propane in the LHVG on the flame characteristics, a fuel consisting only of methane and nitrogen with the same heating value is also studied. For the numerical analysis, the 2D commercial software FLUENT with the reduced GRI 3.0 detailed reaction mechanism is used to study the flame structure. According to the results, the flame length of LHVGs declines with decreasing heating value for the same Reynolds number. Especially, the slope of the normalized flame according to Reynolds number decreases from 0.179 of methane to 0.111 of LHVG 6000. The flame stability limits decrease significantly when the heating value decreases, and no lifted flame is observed when the heating value of fuel is extremely low. Numerical results also show that flame length is shortened by up to 34% as the heating value decreases from methane to LHVG 6000. The flame thickness becomes narrower as the heating value decreases.