Premixed Flame Propagation of Methane/Carbon Monoxide/Air in a Closed Tube with an Obstacle

To investigate the actual gas explosion and propagation laws in the roadway of an underground mine, experiments were conducted in a standard 19-L tube of rectangular section to provide a comprehensive understanding of the effects of carbon monoxide (CO) addition and obstacles placed on the flame propagation of explosions from methane-air mixtures at different conditions. The flame structure, flame propagation speed, heat loss, and explosion pressure were used to reflect the explosion behaviors of the premixed flame. The experimental results indicate that the enhancement and attenuation of the explosion pressure wave are significantly influenced by an obstacle. The existence of obstacles changed the trend of classical pressure rise, thus forming a first pressure peak. In addition, the position close to the obstacle presented a higher explosion pressure. Under 7 vol.% and 9.5 vol.% CH4 conditions, the increase of CO (from 0 vol.% to 2 vol.%) promoted explosion flame propagation. However, the CO exhibited a clear negative effect on the rate of flame propagation due to exacerbated O-2 depletion of 11 vol.% CH4, and the negative effect enhances with CO increased. Besides, when the CO addition increased, the flame tended to more instability and more brightly. For heat loss, with the increase of CO content in mixed gases, there was a slight promoting, constant and inhibiting effect for 11 vol.%, 9.5 vol.%, and 7 vol.% CH4, respectively. These results are of fundamental importance for the prevention and mitigation of gas explosion in underground mines and other industrial scenarios.