Influence of geometrical design on the efficiency of a simple down-the-hole percussive drill

The utilization of pneumatic DTH hammer drilling is the most efficient approach to rescue miners. The previous DTH hammer's impact model was simplified and the analysis of impact parameters was incomplete, hindering further drilling research. To enhance the rate of penetration (ROP) in downhole rescue drilling, this paper establishes a dynamics model for single impact drilling using a pneumatic DTH hammer. The model considers stress wave transmission between flexible components and derives response functions for the piston and drill bit. Through numerical simulation combined with engineering, the velocity-displacement response of the drill bit's bottom in the time and frequency domains is obtained. The effect of impact parameters on the displacement, velocity responses, and stress distribution of the piston and bit during impact is analysed. The results show that weight on bit has a large effect on the quasi-static response, and only focusing on vibration can ignore the static effect. The maximum value of the ROP occurs at the instant of impact, and its corresponding frequency represents the optimal impact frequency. These provide a theoretical reference for achieving higher construction speeds, greatly shortening the duration of mine accident rescue operations, and ensuring the safety of personnel trapped underground.