基于PFC的微波辅助PDC齿破岩数值模拟

Numerical Simulation of Microwave-Assisted PDC Cutter Breaking Rock Based on PFC

微波辅助机械破岩是近年来提出的一种破岩新方法,为探索该方法辅助PDC钻头破碎难钻地层的可行性,本文基于离散元软件PFC的黏结颗粒模型(BPM),建立了微波加热下PDC齿与岩石互作用模型,研究了不同微波照射条件对PDC齿切削破岩的影响。结果表明:在相同微波照射时间下,照射功率较低时,切削破岩模式以PDC齿的挤压刮切作用为主,随着功率的提升,岩石内部热裂纹逐渐增多,破坏模式转变为微波诱导热裂纹所主导的脆性块状破坏为主;微波损耗功率达到3.51 kW、照射90 s后,平均切削力和破岩比功分别较常规切削时降低56.77%和73.9%,微波损耗功率越大,照射时间越长,破岩效率越高;微波照射可减小切削力的波动幅度,使切削力的变化更平缓,有助于提高PDC齿的工作寿命。

Microwave-assisted rock breaking is a new rock breaking method proposed in recent years.To explore the feasibility of this method in assisting PDC bits to break hard-to-drill formations,a PDC cutter-rock interaction model considering the effects of microwave heating has been developed based on the bond particle model(BPM)built in discrete element software PFC.The effects of different microwave irradiation conditions on the cutting and rock breaking of PDC cutter were studied.The results show that under the same microwave irradiation time and low power,the cutting rock breaking mode is dominated by the extrusion and scraping of PDC cutter.With the increase of microwave power,the thermal cracks in rock gradually increase,and the damage effect of microwave on rock dominates the failure mode of rock in the cutting process.When the microwave loss power reaches 3.51 kW and the irradiation time is 90 seconds,the average cutting force and specific work of rock breaking are 56.77%and 73.9%lower than those of conventional cutting,respectively.The larger the microwave loss power is,the longer the irradiation time is,and the higher the rock breaking efficiency is.Microwave irradiation can reduce the fluctuation of cutting force and make the change of cutting force more gentle,which is helpful to improve the working life of PDC cutter.