Abstract
This paper presents a novel pneumatic Down-The-Hole (DTH) hammer with self-rotation bit used for rock drilling, and the mechanical structure and working principle are mainly covered. A unique mechanism with ratchet and pawl incorporated in pneumatic DTH hammer is proposed for percussion-rotation drilling to break rock. The drill bit can rotate while the drill pipe stays still because of the structure design and reduces the friction between the drill pipe and borehole. Firstly, the rationality of mechanical invention is verified via the finite-element software ANSYS and the numerical simulation of impact dynamics. Moreover, the energy transfer regulation is revealed in the impact process under differential final impact velocity, which can help practical experience in mechanical design. Finally, based on the experimental study on the novel hammer, we found that its function can satisfy the requirement, as well as overall performance, was improved.
Highlights
Pneumatic DTH drilling is a rotary percussive drilling method widely used in many fields such as infrastructure construction [1], geological exploration [2], oil and gas production [3], etc
Conventional pneumatic DTH hammer driven by compressed air provides a specific impact frequency and energy to drill bit in stress waves for rock breaking
Chiang et al developed a non-linear dynamic model consisting of six differential equations to compute the performance of valveless DTH pneumatic hammers [8]
Summary
Pneumatic DTH drilling is a rotary percussive drilling method widely used in many fields such as infrastructure construction [1], geological exploration [2], oil and gas production [3], etc. It has many advantages: less power loss, higher penetration rate, and greater hole accuracy, especially in hard rock formations [4,5,6,7]. The core of its mechanism is to use the gas generated by the air compressor to drive the piston to strike the drill bit and convert the linear motion of the piston into the rotary motion of the drill bit in a limited space
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