【作者】 王明波；

【导师】 王瑞和；

【作者基本信息】 中国石油大学 ， 油气井工程， 2007， 博士

【摘要】 磨料水射流切割破碎技术在国民经济建设的诸多领域中都获得了广泛应用,但由于磨料水射流切割破碎物料的影响因素众多,目前磨料水射流的结构特性和破岩机理的物理机制尚不清晰,这在相当程度上限制了磨料水射流切割破碎技术的发展。本文运用多相流体动力学和颗粒动理学等理论,推导得出了磨料水射流的双流体模型,形成了分析磨料水射流结构特性和两相作用机理的数值方法,采用数值模拟和实验研究相结合的技术路线,较系统地研究了磨料水射流中两相速度分布和湍流参量分布,并运用连续介质力学、损伤力学和非线性冲击动力学等理论,建立了磨料水射流冲击破碎岩石的有限元模型,采用数值模拟的方法结合前人研究成果,较为系统地研究了磨料水射流破岩过程中的细观机理和不同宏观参量对冲蚀体积的影响,进一步发展和完善了磨料水射流冲击破岩理论。综合分析表明,磨料颗粒所受的惯性力、重力、压差力和Stokes阻力对其运动具有重要影响。喷嘴内液固两相间存在速度滑移,磨料颗粒在相间力的作用下速度趋向液相速度。非旋转和弱旋转磨料水射流中,液相轴向速度分布类似于高斯型,液相轴向速度仍然满足一定的自相似性。液相径向速度分量很小,沿半径分布规律十分复杂。射流轴对称面上液相湍流强度分布表现出一定的对称性,靠近射流边界处湍流强度较高,射流断面上沿径向方向湍流强度呈“M”形分布。弱旋转磨料水射流中,液相切向速度沿半径方向表现为Rankine复合涡形式。本文条件下,液相切向速度在喷距大于2d后,具有自相似性。磨料颗粒速度沿半径的变化趋势与流体微团的基本一致,沿半径方向呈高斯分布。随着喷距的增加,磨料颗粒速度逐渐降低,速度剖面逐渐平缓。磨料水射流破岩过程中,岩石在冲击波压力、环向拉应力以及应力波反射拉应力等作用下经历了产生破碎、产生初始裂隙、裂隙贯穿等几个过程并最终形成冲蚀漏斗。在其他条件相同时,冲蚀体积随磨料颗粒速度的增大而非线性增加,随冲击角度的增大呈现非线性增加的趋势,随磨料颗粒粒径的增大也呈非线性增加。本文采用数值模拟的方法对磨料水射流结构特性和破岩机理进行了较为系统的研究,模拟分析得到了实验结果和前人研究结果的验证和支持,表明本文所建立的磨料水射流结构特性和冲击破岩的理论体系合理可行,从而为研究磨料水射流流场结构和破岩机理提供了一条新途径。更多还原

【Abstract】 Abrasive water jet technology has found its applications in many fields, for example, the petroleum engineering, the mining and the construction industry. The influencing factors and the complex mechanisms in the abrasive water jet have hindered its development. With the application of fluid dynamics, multiphase flow theory and particle kinematics theory, a two-fluid model was provided and the numerical method was formed. Systematic analysis was performed on the flow properties and the turbulence parameters distributions. Furthermore, a finite element model describing the rock-breaking process of abrasive water jet was provided with the help of finite element method, continuum mechanics and non-linear shock dynamics. The influences of different working parameters on the volume loss were also studied in this dissertation.It is found that the inertia force, the gravity force, the pressure difference force and the Stokes force have vital influence on the movement of abrasive particles. It’s unsuitable to neglect the force exerted on the fluid phase by the abrasive particles. Velocity difference was observed when the abrasive water jet moves along in the nozzle. The particle’s velocity tends to approximate to the fluid velocity with the drag force acting on it, but the accelerating process is slower than the fluid phase. Fluid velocity distributions in fluid-particle flow on the axis line and nozzle exit are found similar to the single phase.The axial velocity distributions of fluid phase in abrasive water jet (non-swirling and swirling) take on a Gaussian distribution. With the increase of standoff distance, the axial velocity decreases. The self-similarity characteristic of axial velocity is observed in the simulation. The radial velocity of the fluid phase is small in amplitude and shows complex distributions in the flow domain. Symmetrical characteristics of turbulence intensity are observed, high amplitude of turbulence intensity is found near the flow periphery and the turbulence intensity distributions in the radial direction take on an “M”shape. The tangential velocities of the fluid phase in the swirling abrasive water jet take on the Rankine vortex form. Under current condition, the self-similarity characteristic of the fluid tangential velocities is observed when the standoff distance is larger than 2d, where d is the diameter of the nozzle. The velocity distributions of particle phase are similar to the fluid phase and take on a Gaussian distribution in the radial direction. With the increase of standoff distance, the particle velocity decreases and the velocity profiles tend to be flat.In the process of rock-breaking with abrasive water jet, fail, initial crack generation and crack propagation are obversed when the rock is hit by the shock wave pressure, the tensial stress in the radial direction and the reflecting tensile stress. Non-linear relations are found between the volume loss and the particle velocity, angle of attack and particle size.It is the first time that the numerical simulation is applied to the systematic research on the flow property and rock-breaking mechanism of abrasive water jet. Numerical results are validated by the experimental data and former researchers’conclusions, which prove that the theoretical architecture built in this thesis is both reasonable and feasible.更多还原