风筒出口位置对掘进工作面瓦斯分布的影响

Influence of outlet position of ventilation duct on the gas distribution in the heading face

根据计算流体动力学(CFD)理论,运用Fluent软件对掘进工作面的风流流场及瓦斯分布进行数值模拟,研究了在断面形状为梯形的掘进巷道中,瓦斯从掘进迎头和巷道两帮均匀涌出时,风筒出口离掘进迎头的距离对掘进巷道中风流流场和瓦斯分布的影响。结果表明:压入式局部通风掘进巷道工作面风流从风筒出口流出后,沿风流方向瓦斯浓度逐渐增大,在靠近迎头处巷道两帮底部和顶部瓦斯浓度较高;随着瓦斯涌出量的增加,由于高浓度瓦斯密度降低而产生的上浮力的作用,在靠近迎头的上部区域发生瓦斯沿顶板逆风流方向流动的现象;上浮力的作用会改变流场的分布状况,在靠近迎头处产生涡流;风筒出口离掘进迎头越近,风流到达迎头时携带的瓦斯量越少,且迎头处的风速越大,靠近迎头区域中的瓦斯浓度越低。

Based on the Computational Fluid Dynamics （CFD） theory, this article is aimed at simulating the distribution of air current and gas at the working face with the enforced auxiliary ventilation by using the fluent software. The distribution of air current and gas at the working face with the enforced auxiliary Ventilation has been studied when the gas is emitted from the head and the sidewalls of a trapezoid across the air current section. The results of our simulation show that the methane concentration on the heading face with the enforced auxiliary ventilation helps to increase steadily along the air current route after the air is released from the duct outlet as the methane concentration keeps higher near the heading face and the bottom of the two sides of the developing roadway with the gas being easy to build up. With the increase of the gas emission rate, high concentration methane would rise up under the effect of the body buoyant force, and the airflow drawing-back against the airflow along the roof around the heading face. The body-buoyant force of the high concentration methane can thus change the air rate distribution, leading to the eddy in the airflow near the end of the working face. Since the duct position has a great effect on the distribution of the methane, the methane concentration is likely to rise if the duct is located at the one end of the airway for the concentration easy to be built up. Therefore, it can be concluded that the nearer the duct outlet is to the working face, the greater the velocity at the heading face tends to be. In the same way, the lower the methane concentration is, the easier the gas is expected to be built up.