Pneumatic Chip Removal Mechanism Through The Drill Rod Bore During The Gas Drainage Drilling In Soft Outburst Coal Seam

In view of the problems about high cinder migration resistance, sedimentary accumulation plugging holes and lower depth of holing the reverse circulation technology which is commonly used in drilling engineering is applied to gas drainage drilling during the horizontal gas drainage drilling in soft outburst coal seam. This article studies pneumatic chip removal mechanism through the reverse circulation chip removal through the drill rod bore.Firstly, with the application of continuum theory and mathematical method this article establish two-phase flow model of gas and pulverized coal cloud in the process of pneumatic chip removal including the continuity equation, momentum equation and energy equation. And set up mathematical model between pulverized coal cloud velocity and air velocity. With the formulas for pneumatic conveying design calculation and experimental research the main process parameters is obtained which include the solid-air conveying ratio, air velocity, particle size, etc.Secondly, based on eulerian two-fluid model pneumatic chip removal mechanism through the drill rod bore during the gas drainage drilling is established for simulation. Grid partition and numerical solution are used by FLUENT. It is concluded the motion of the gas phase-air, solid phase-coal in the tube. Pulverized coal particle is analyzed under different inlet pressure and flow rate, particle size and concentration of conveying pressure loss and the mechanism of the solid phase velocity. Results show that with the drilling process, the coal particle under the action of reverse circulation strength, air velocity in the upper pipe inner hole is stable, and at the bottom of the drill pipe inner hole near the inner wall of air velocity decreased obviously and is less than the center area. In the same location the greater the transport concentration, the greater the air velocity is. Under the condition of invariable in conveying concentration, pressure loss increases with the increase of air velocity.Finally, pneumatic conveying experiment device is designed to test the data of pressure loss in different inlet velocity, conveying capacity,solid-air conveying ratio and particle size. Moreover, the motion of pulverized coal is filmed by high-speed camera. Theoretical analysis and analog simulation for pneumatic chip removal in gas drainage drilling is verified.