Analysis of Transient Flow Field and Rock Cuttings Trajectory in Large-Diameter Reaming Drilling

This paper investigates the transient flow field characteristics and rock cuttings trajectory during large-diameter reaming drilling, aiming to address the issue of low debris removal efficiency. By establishing a liquid-solid two-phase flow numerical model, the flow field of a bundled down-the-hole hammer for 830mm reaming drilling was simulated, and the flow velocity, pressure distribution, and rock cuttings movement trajectory within the hole bottom and return channel were analyzed. The study found that the bit rotation significantly influences the flow field, increasing the area of high-speed regions at the hole bottom, enhancing the average flow velocity of the flow field, and facilitating the removal of rock cuttings. Simultaneously, the pressure difference in the flow field at the hole bottom is crucial for transporting rock cuttings to the debris removal pipe, and there exists an optimal critical value of bit rotation speed to achieve the best reverse circulation effect of the flow field. The analysis of rock cuttings trajectory shows that the flow field at the hole bottom can be divided into three stages, with different characteristics of rock cuttings distribution at each stage. Increasing the diameter of the debris removal hole helps enlarge the area of high-speed regions for rock cuttings, improving debris removal efficiency. This study provides theoretical guidance for enhancing debris removal efficiency in large-diameter reaming drilling.