Optimal Design Parameter of Percussive Drilling System for Efficiency Improvement

Abstract

The aim of this paper is to find the optimal design parameters of the percussive drilling systems considering the bit-rock interaction. First, the motion dynamics of the bit impacted by the dropped piston is modeled by the impact stress propagation and the rock breaking mechanism representing penetration resistance coefficient and unloading constant. Next, the damping vibration behaviors of the bit are investigated considering the impact time duration and the rock loading/unloading condition. Also, the proposed dynamics is simplified by adopting two dimensionless parameters; the bit-piston mass ratio and the rock-piston stiffness ratio. Finally, the drilling efficiency defined by the energy transmitted from the piston to the rock is presented in terms of the proposed parameters. As a result, the optimal design parameters of the percussive drilling systems is found for improving the drilling efficiency. This result is effectively applicable to the design of DTH hammer and Top hammer and their performance estimation.