Experimental investigation on the effect of dilution on the liftoff and blowout characteristics of jet diffusion flame

On the background of combustion utilization of low calorific value gas fuel, methane or propane diluted by N2 or CO2 and nozzles of 2mm or 3mm inner diameter are set as multiple experimental variables. The liftoff and blowout velocities of jet diffusion flame varying with the diluent concentration were experimentally investigated. With the increase of the diluent concentration, the liftoff velocities slowly decline almost linearly, while the blowout velocities quickly decrease nearly exponentially. The analysis shows that the tendencies may be attributed to the decreases in the stoichiometric laminar burning velocity, the original fuel mass fraction and heat release. Suggestions on the design of burner utilizing low calorific value gas fuel are proposed. In addition, exceeding the critical diluent concentration, the attached flame is directly quenched instead of being a stable lifted flame with the increase of the jet velocity. According to the Reynolds numbers of methane and propane at each critical diluent concentration, it can be inferred that the two critical diluent concentrations of methane and propane are controlled by different mechanisms.