Effects of the mining-face ventilation mode on the air-current field as well as the gas movement in the gob

The present paper intends to introduce our research results of the effect of the mining-face ventilation mode on the air-current field as well as the gas migration in the gob. For our research purpose , we have first of all worked out a numerical simulation of the airflow field and the gas distribution situation in it. The results of our investigation demonstrate that there is a dominant difference in the air leakage, air-current flow and its movement because the seam obliquity and ventilation mode of the working face are quite different. The gob gas buoyancy pressure caused by the natural ventilation pressure and the total pressure of the ventilator across the face decide the amount of the gob and its air leakage distribution. In case of the ascending ventilation, the total pressure of the ventilator across the face and the spontaneous air pressure are in the same direction, hence, the greater the pressure difference across the face, the greater the amount of air leakage. Air linkage went into the gob from the lower corner of the face and the lower face, while air leakage of gas carried went into the face from the upper corner upper face. However, when the pressure of the face comes from the descending ventilation, the pressure of the face would be weaker than the natural pressure in the gob, for the natural air pressure, the ventilation pressure and the total pressure of the ventilator across the face are going on in the opposite directions. In that case, there would occur the gas reflux and the air leakage in the gob from the corner or the lower part of the working face, and, naturally, the gas produced would flow into the working face from the upper corner and the upper part. On the contrary, when the descending ventilation comes to turn, the natural ventilation pressure and the face pressure would come in the opposite directions. And, now, even at the same condition, the air-leaking rate in the ascending ventilation of die gob would be greater than that in the descending ventilation, and vice versa. In such a case, with the coal seam angle increased, the gas volume would be falling whether in ascending ventilation or in the descending ventilation.