Numerical simulation of the change process of field variables distribution in goaf caused by air reversing in working faces

Based on No.1318 shooting case in Huaxing Coal Mine,the changing process of air leakage flow,components (oxygen,CO and methane),and temperature in the flow field of goaf during air reversing were solved and described,and the changing rule of gas emission volume of different components along the boundaries of the working face while air reversing was given.It is simulated that after air reversing the content distribution centers of different components are reversed,the upper high temperature area is cooled down while the lower area with low temperature becomes a new high temperature area,making the temperature rising process in goaf at a low start point,which is favorable for slowing down the rising velocity of temperature and thus preventing spontaneous combustion of coal from taking place.During air reversing,the emission volume of CO has a jumping process of sudden decrease→increase→slow attenuation→gradual increase.After this process,the increase range of gas emission volume becomes slowed.By burying pipes to extract gas,harmful gases within the working face could be prevented from exceeding limit during air reversing.At the same time,the condition to realize air reversing is given,namely there is no naked flame in goaf.