Inhibition effect and mechanism of CF3CHCl2 on methane flame in oxygen-enriched environment

In oxygen-enriched environment (oxygen concentration above 21%), flammable materials become even more flammable with higher net heat release rate, burning velocity and combustion intensity. Unfortunately, most investigations concentrated on the characteristics and mechanisms of oxygen-enriched combustion, the methods to control or weaken their perniciousness of oxygen-enriched fire have been rarely reported. CF3CHCl2 (HCFC-123, R123) has been demonstrated excellent inhibition performance for oxygen-normal combustion in the fire suppression experiment, was considered as the potential fire extinguishing agents of aircraft cargo. This study performed the comparison between the inhibition performance and kinetic mechanism of CF3CHCl2 for the CH4- N2-O2 (21% of O2) flame and the flames enriched up to 23.1%, 25.2%, 27.3% of oxygen with constant-volume combustion chamber and numerical prediction. Even for the oxygen-enriched flames, CF3CHCl2 showed substantial inhibition effect on the burning velocities and adiabatic flame temperature. The chain-radicals pro-duction/consumption rate and normalized sensitivity coefficients were investigated to analyze the in-depth inhibition mechanisms of CF3CHCl2 for oxygen-enriched flames. The mechanism analysis found that the inhibition effect of CF3CHCl2 and relevant halogenated species on oxygen-enriched flame are smaller than that in normal flame.