煤层水力割缝系统过渡过程能量特性与耗散

Energy characteristic and dissipation in transient process of hydraulic cutting seams system in coal seam

煤层水力割缝能有效促进瓦斯解析运移,提高瓦斯抽采率,但割缝系统运行中发生的过渡过程会形成瞬时强冲击波作用于煤层,若控制不当易诱发喷孔、抱钻,甚至产生煤与瓦斯突出。针对该问题,采用理论分析和实验测试方法对自主设计研发的不同结构水力割缝系统过渡过程压力-流量特性进行了讨论和测试,分析了过渡过程中系统能量特性与耗散规律。结果表明:系统过渡过程中流体携带能量发生快速激增,能量激增量与水力割缝结构参数相关,激增能量通过高速冲击传递给煤层,改变煤层原始应力,诱导煤层快速卸压,部分激增能量在管路中消耗;结构对系统过渡过程激增能量影响不同,对发生过渡过程,能量随结构面积的增加而增加,但单位能量不变,激增后能量随结构面积的增加而减小,单位面积能量减小,改变结构有效面积是控制过渡过程激增能量的有效方式,可有效降低作业过程中煤与瓦斯突出的危险。

Gas migration and extraction rate is progressively promoted in using hydraulic cutting seams in coal mine.Nevertheless,potentially hydraulic pulse impact wave,a kind of hidden risk by operating hydraulic cutting systems,formed in transient process when shifting from drilling to cutting maybe lead to blowout,holding drill,and more seriously cause coal and gas outburst accident while improperly controlled.Depending on this transition process problem,pressure-discharge characteristics of different structure designed independently were discussed and tested by theoretical analysis and experimental testing,energy characteristic and dissipation were analyzed.The results show that energy carried in fluid increases sharply during transition,the amount of increasing energy correlates with structure parameter of hydraulic cutting systems;Energy which induced ground pressure relief rapidly transforms to coal seam through high-speed waterjet impact,partially energy increasing in transient process consumes in pipeline;The amount of increasing energy in transient process is greatly affected by key device structure parameter.Prior transient energy increases with key deviceeffective area while per unit prior transient energy is almost steady.However,transient switching energy and per unit transient switching energy decreases at the same time with key device effective area.Controlling risk of coal and gas outburst induced by the transition process can be carried out by choosing proper effective parameter.