Cuttings carrying characteristics of back-reaming pneumatic impactor exhaust during drilling operation

摘要

The flow fields of chip removal from the impactor's exhaust hole to its rear head were established to study the cuttings carrying characteristics of back-reaming pneumatic impactor exhaust by utilizing the computational fluid dynamics theory and simulation software Fluent. Based on the structure and working principle of the impactor, the gas solid two phase flow was simulated, and the gas phase characteristics of the flow field and the moving trajectory and concentration distribution of particles were obtained. The research shows that: once the exhaust enters the field its speed will slow down and the field pressure will gradually decrease from the entrance to the exit; cuttings particles will gather around the bottom and there is minor variation in their average concentration as they are distributed along a contrary direction against the entrance while the maximum concentration descends along the same direction and finally becomes stable. Moreover, the effect of drilling speed and exhaust mass flow of the impactor on the solid carrying characteristics was analyzed. The result demonstrates that: as the drilling speed increases, the carrying ability of exhaust decreases and when the rated operation pressure is 0.8 MPa, the drilling speed should be less than 12.6 m/h; as the mass flow rate of exhaust increases, the carrying ability increases as well, and the mass flow rate should be moderately increased under the condition of ensuring the working performance of the impactor.