煤中瓦斯运移的非达西渗流机理研究

Study on Non-darcy Seepage Mechanism of Gas Migration in Coal

通过煤体中瓦斯渗透性能测试,采用渗流理论分析瓦斯在煤体中的渗流机制,结果表明:在高压阶段,瓦斯渗透流量Q与压力项△~2p/L线性相关,在低压时,渗流曲线Q-△~2p/L表现为对Darcy定律线性关系的偏离;瓦斯在煤体中的渗流由非线性转变为线性,即瓦斯在煤体中的渗流由非达西渗流转变为达西渗流,存在转变的临界点。瓦斯在煤体中的渗流与雷诺数相关,雷诺数大时渗流属达西渗流,雷诺数小时渗流为非达西渗流。理论计算分析揭示了瓦斯分子自由程和煤体孔隙结构共同作用导致了非达西渗流现象。

Under different confining pressures,gas seepage tests are carried out,and these tests are used to discuss gas seepage mechanism in coal.The tested and theoretical results show that under different confining pressures,gas seepage laws are consistent in coal.In the higher gas pressure section,the percolation curve of Q and△~2 p/L meets the linear relationship,but the gas pressure is lower,the seepage curve of Q and△~2 p/L deviates linear relationship of Darcy’s law.The critical point lies from nonlinear to linear segment of gas flow in coal,and it is a gradual process from non-Darcy flow to Darcy flow.At high Reynolds number,gas percolation obeys Darcy’s law,but at low Reynolds number,the gas seepage in different metamorphic grade coals is non-Darcy flow.The collision of gas molecules and coal wall is the physical mechanism of gas non-Darcy flow phenomenon,which is determined by the mean free path of gas molecules and pore structure of coal,and the theoretical calculation well reveals the mechanism of gas non-Darcy seepage in coal.