瓦斯抽采钻孔反循环气力排屑数值模拟

反循环气力排屑是顺层钻孔的新技术，可以提高瓦斯抽采钻孔的成孔深度与成孔率，采用CFD-DEM耦合方法对瓦斯抽采钻孔反循环气力排屑过程进行数值模拟，研究了排屑气速、煤屑生成量对气力排屑性能和气力排屑系统压降的影响。研究结果表明:排屑气速较低时，煤屑在重力的作用下在钻杆内堆积，易导致钻杆堵塞，为保证顺利排屑，需要较大的排屑气速；随着煤屑生成量的增大，对气力排屑性能影响不大，但钻杆内煤屑的体积分数增大，煤屑-煤屑，煤屑-钻杆之间的碰撞加剧；气力排屑系统的压降与排屑气速、煤屑生成量均呈正相关，综合考虑能耗因素，在保证顺利排屑的前提下，应选择合适的排屑气速。

Numerical simulation on reverse circulation pneumatic chip removal in gas drainage borehole

The reverse circulation pneumatic chip removal is a new technology of borehole along coal seam, which can improve the hole forming depth and hole forming ratio of gas drainage borehole. The numerical simulation on the process of reverse circulation pneumatic chip removal in the gas drainage borehole was carried out by using the CFD-DEM coupling method, and the influence of gas velocity of chip removal and generation amount of coal chip on the performance of pneumatic chip removal and the pressure drop of pneumatic chip removal system was studied. The results showed that the coal chip accumulated in the drill pipe under the effect of gravity when the gas velocity of chip removal was lower, which caused the blocking of drill pipe, and a higher gas velocity of chip removal was needed to ensure the smooth chip removal. The increase of the generation amount of coal chip had little effect on the performance of pneumatic chip removal, but the volume fraction of coal chip in the drill pipe increased, and the collision between coal chip and coal chip and between coal chip and drill pipe intensified. The pressure drop of pneumatic chip removal system was positively correlated with the gas velocity of chip removal and generation amount of coal chip, and considering the energy consumption factor comprehensively, the appropriate gas velocity of chip removal should be selected under the premise of ensuring the smooth chip removal.