超高压双流道PDC钻头破岩机制研究

基于岩石弹塑性力学、水动力学及运动学,采用动力接触法模拟射流或机械齿与岩石的交互作用,利用Hoffman失效准则控制岩石破碎的动态边界,采用单步Houbolt算法求解动力方程,建立整体超高压双流道PDC钻头破岩的三维动态数值模型。全面、系统地研究岩石内部应力、岩石的破碎体积、岩石破碎所需能量以及钻压和扭矩等在岩石破碎过程中的变化规律,并对不同刀翼数及超高压喷嘴在不同位置时钻头的破岩效率进行分析,得出最佳双流道PDC钻头的结构。

STUDY ON ROCK-BREAKING MECHANISM OF HIGH-PRESSURE PDC BIT WITH DUAL-FLOW CHANNEL

The three-dimensional dynamic numerical model of PDC bit to break rock has been set up,in which the finite element models of rock,jet and mechanical tooth are created respectively based on elastoplastic mechanics,hydrodynamics and kinematics of rigid body.The interaction between jet or mechanical tooth and rock is simulated by dynamic contact method.The dynamic boundary is controlled by Hoffman failure rule.The single-step Houbolt algorithm is adopted to solve the dynamic equation.The rock-breaking mechanism has been analyzed comprehensively by various ways such as the interior stress distribution of rock,the weight on bit and torque of bit impacting rock,the volume of rock breaking,the energy of rock breaking,etc..The influences of the number of blade and the position of high-pressure nozzle on bit breaking rock have been studied;and the structure of the dual-flow channel PDC bit has been optimized.