Abrasive Water Jet Flow Property And Rock-breaking Mechanism

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.