磨料射流喷嘴外流场磨料速度模型及分析

Analysis and modeling of particle in the outer flow field of the nozzle of AWJ

喷嘴外流场磨料速度是建立磨料射流冲蚀深度模型的重要前提,以磨料射流喷嘴外流场磨料为研究对象,以固液两相流理论为基础,建立了磨料射流喷嘴外流场磨料速度模型,基于位移等分法和迭代算法求解了该速度模型,利用PIV实验进行验证,实测值与理论值的平均百分比误差在5%之内。并利用该速度模型得到了磨料射流喷嘴外流场磨料运动规律:(1)磨料颗粒流在喷嘴外流场的流动具有扩散性;(2)磨料颗粒沿射流轴向运动时,大多经历了一个先加速后减速的过程,只是加速距离有所差异;(3)初始段内相同轴向距离的射流横截面上,位于等速核区域内的磨料速度相同,随后磨料速度从等速核边界朝射流边界方向逐渐减小;初始段末端及基本段内相同轴向距离的射流横截面上,磨料速度沿射流径向的分布完全呈现出钟形速度分布。

A key requisite for establishing the erosion depth model of the AWJ is to determine the velocities of particles in the outer flow field of the nozzle.In this paper,based on the theory of solid-liquid two-phase flow,a theoretical analysis for particle velocities within an AWJ is presented and the associated particle velocity models are developed. The velocity model is solved by the displacement division method and iterative algorithm.The developed models are finally verified by that the average percentage error between the model value and the corresponding experimental results of PIV is less than 5%.Using the velocity model,the law of movement of particles in the external field of nozzle of AWJ is obtained:(1) There exists a flow expansion in the structure of the particle flow.(2) When the particles move along the axial direction of the jet,most of them have experienced a process of acceleration and deceleration. The difference is that they have different acceleration distances.(3) On the cross section of the same axial distance in the initial segment,the particle velocity is the same in the potential core. And then the particle velocity decreases gradually along the boundary of the potential core to the jet edge.On the cross section of the same axial distance at the end of the initial segment and the basic segment,the distribution of particle velocity along the radial jet direction fully exhibits a bell shaped distribution.