Characteristic Analysis of a HDR Percussive Drilling Tool with Sinusoidal Impact Load

Due to the high strength of hot dry rock (HDR), the rate of penetration (ROP) improvement is one of the issues in deep HDR drilling; it is believed that percussive drilling is one of the methods to improve the ROP of HDR. Study shows that the specific shape of impact load can use a certain proportion of its impact energy to break rock, which indicate the impact load shape of percussive drilling tool has remarkable influence on the ROP of HDR. Therefore, a novel HDR drilling tool with sinusoidal impact load is proposed in this paper, and the theoretical analyze of the HDR drilling tool reveals that the impact load of the HDR drilling tool is sinusoidal shape. Thereafter, the energy utilization efficiency of sinusoidal impact load is discussed, show that the best energy utilization efficiency of sinusoidal impact load is 80%. Lastly, the influence laws of load characteristics from impeller vane number, impeller position, flow rate and outlet size are investigated, aiming to analyze the impact load shape and frequency of the HDR drilling tool. The results demonstrate that the impact load of the HDR drilling tool aligns with the theoretical sinusoidal shape, and the load amplitude and magnitude of the tool is increased with the increasing of flow rate. The impact load magnitude and amplitude of the tool is higher when the impeller is installed at the top right position, and the impact frequency is much higher than other positions as well. Meanwhile, the relationship between flow rate and impact load and frequency is linear, and the outlet size has remarkably influence on impact load, with larger outlet sizes resulting in a substantial decrease in impact load. Ground testing validates the simulated results under same conditions, the impact load of the HDR drilling tool shows sinusoidal wave-like fluctuations, achieving the expected design goals. The research could provide theoretical guidance to the percussive drilling tool design of HDR.