Spatial-temporal variation features and law of gas concentration in the fully mechanized working face under the condition of intermittent ventilation

Based on the fluid mechanics and mass transfer theory, a mathematical model of the spatial-temporal variation of gas was derived to avoid the gas accident caused by the main fan stopping ventilation under the condition of intermittent ventilation in the tunnel. According to the actual parameters of the tunnel, a numerical calculation model was established. The spatial-temporal variation of gas concentration in the fully mechanized working face under the condition of intermittent ventilation was calculated by using the commercial package Fluent, and the correctness of the calculated results was verified by the actual monitoring data of the mine. Firstly, the gas concentration was calculated under different wind velocities at driving face in coal tunnel, and the result showed that the gas can be carried effectively by the wind when the wind velocity is about 1.8 m/s. Secondly, the distributions of wind velocity and gas concentration at driving face were studied at 1.8 m/s, and the result showed the gas concentration increased gradually with the distance close to the outlet, but the gas concentration almost kept constant at the height of driving face. Thirdly, the distribution of gas concentration was investigated with time after the ventilation was stopped and restarted, respectively. The gas concentration of test point gradually increased with the increment of downtime, when the downtime was 40 min, the gas concentration of test point 3 reached the maximum value. The gas concentration increased gradually and reached the maximum after 10 min of restart, then sharply decreased and kept constant.