粒子冲击钻井钻头喷嘴流场数值模拟研究

摘要

为了考察粒子冲击钻井过程中，粒子流经钻头喷嘴的加速过程和流场分布规律，应用Fluent对粒子进入喷嘴后的流动进行数值模拟研究。运用标准K-ε双方程模型，对双锥度喷嘴粒子射流流场进行仿真模拟，分析了射流压力、围压、粒子直径和粒子质量浓度等因素对粒子射流流场的影响。结果表明，粒子射流加速主要发生在喷嘴收缩段，在等速核前缘速度达到最大。粒子喷射速度和单位时间内通过喷嘴的粒子动能随射流压力增大而增加；粒子浓度越大，单位时间内通过喷嘴的粒子动能越大，破岩效率升高，但粒子浓度过大会导致其流动性差，反而不利于破岩。因此，粒子浓度对其冲击破岩效率的影响主要取决于破岩过程中哪种因素起主要作用。%To investigate the acceleration process of particle flowing through bit nozzle and the distribution law of flow field in the process of particle impact drilling, the CFD analysis software FLUENT was adopted to conduct a numerical simulation study of the flow of particles entering the nozzle. The standard κ-ε two-equation model was used to simulate the particle jet flow field of double cone angle nozzle, examining the flow law of particle jet inside and outside the nozzle and analyzing the law of the effect of jet flow pressure, con-fining pressure, particle diameter and particle mass concentration on the flow field of particle jet. The findings show that particle jet ac-celeration mainly takes place in the shrinkage section of nozzle and the frontal velocity of the potential core reaches the maximum.The particle jet speed and the kinetic energy of particle which goes through the nozzle in unit time increase with jet flow pressure. The higher the particle concentration, the greater the kinetic energy passing through the nozzle in unit time and the higher the rock-breaking effi- ciency. But if the particle concentration is too high, the particle fluidity will be undesirable. This is unfavorable to rock-breaking. Therefore, the effect of particle concentration on the efficiency of particle impact rock-breaking mainly depends on which factor plays the main role in the process of rock-breaking.