基于Selfrag高压电脉冲放电破岩试验的仿真模拟

Simulation of rock breaking test by high voltage electric pulse discharge based on Selfrag

摘要:

高压电脉冲破岩在高温等离子弧的作用下，产生的热应力超过岩石的强度极限时就会使岩石破碎，其破碎坚硬岩石有显著效果。为研究电压、岩石矿物成分、孔隙率3个参数对岩石内电场强度分布的影响，本文基于Selfrag高压电脉冲破岩的试验数据，利用COMSOL Multiphysics仿真软件建立了一种针针电极结构仿真模型。结果表明，施加的电压不同，岩石内部电场强度分布不同；电场在不同矿物成分边界发生畸变，不同矿物成分相对介电常数变化越大，产生畸变越明显，高压电脉冲破碎优先发生在不同矿物成分的接触面；岩石内孔隙的存在，使其周围的电场发生了畸变，其他参数一定，孔隙率越大，岩石越容易被电击穿。研究结论可为高压电脉冲钻井破岩参数的选取提供参考。

Abstract:

Under the action of high temperature plasma arc， high voltage electric pulse will produce thermal stress which can exceed the strength limit of rock， and break rocks， in particular hard rocks with obvious performance. This paper introduces the rock breaking mechanism of electric pulse. Based on the experimental data of Selfrag high-voltage electric pulse rock breaking， a simulation model of the needle electrode structure is established by using COMSOL Multiphysics simulation software. The influence of voltage， mineral composition and porosity on the distribution of electric field intensity in rock is studied. The results show that the distribution of electric field intensity is different with different applied voltage； the electric field distorts at the boundary of different mineral components， and the greater the change of relative permittivity of different mineral components， the more obvious the distortion is. Rock breaking with high voltage pulse occurs preferentially at the interface of different mineral components， and rock can be decomposed into various minerals depending on its composition. The presence of pores in the rock distorts the electric field around it； and the larger the porosity is， the easier electric breakdown the rock is.The research conclusion can provide reference for the selection of rock breaking parameters of drilling by high voltage electric pulse.