Experimental and numerical simulated analysis on combustion and explosion flame characteristics of methane under inerting conditions
To analyze the characteristic change of explosion flame under limited conditions of methane inerted,high-speed schlieren was used to capture the flame images of CO2 inerting inhibiting CH4 explosion in the 20 L spherical device.Besides,a numerical simulation method was used to reproduce the explosion process of CH4 inerted.Through observing and analyzing the evolution process of the flame shape,extinguishment phenomenon,and velocity of flame,the characteristics of explosion flame dominated by buoyancy were mastered.It is found that the velocity of flame in all directions is almost the same,so the flame shape is"spherical".Then,in the cases of adding less CO2,the flame shape is always spherical since the spread velocity in all directions is almost the same.Under the cases of inerting limit,the density difference between the bumed zone and unburned zone of the flame increases significantly,which causes the buoyancy becomes significant.Thus,the"spherical"flame changes into a"ω"flame,and then the flame floats or extinguishes.During flame floating up,the velocity of the bottom is negative and significantly greater than that of the top and both sides.In addition,the numerical simulation can supplement the flame part outside the visualization window in the experiment.The simulation results show that the bottom velocity that directions upward gradually increases during the process of rising,which is significantly higher than that of both sides,resulting in a depression at the bottom center of the flame surface,and finally a"ω"-flame is formed.During the process of flame floating,the flame is extinguished due to the heat exchange with the surrounding unbumed gas or the vessel wall,but there is no overpressure.
NETL
NSTL
万方数据
维普
