基于数值模拟的高压磨料射流喷嘴流场分析及结构优化

Flow field analysis and structural optimization of high-pressure abrasive jet nozzle based on numerical simulation

为得到高压磨料射流喷嘴内部水流和磨料颗粒运动分布的最佳特性,本文基于二相流理论,利用数值模拟方法研究了高压喷嘴内部混合水相的速度及湍流强度分布,重点分析了磨料入口位置对喷嘴出口处磨料颗粒收束性及喷嘴内壁面磨损状况的影响,并提出了减轻壁面磨损的改进措施。结果表明,距喷嘴中心轴线距离越远,喷嘴内部混合水相的湍流强度越低,但由于磨料入口处存在旋涡,混合水相速度则随之先降低后升高。随着磨料入口位置越靠近高压水入口,出口处磨料的收束性呈现先变好后变差的趋势,磨料颗粒则会大量聚集于磨料入口与上壁面交界处,造成喷嘴内壁磨损,此时可通过在后壁面和上下壁面使用圆角过渡来改善射流流向,进而减少聚集处磨料颗粒的体积分数。

For the best water flow and abrasive particle distribution in the high-pressure abrasive jet nozzle,numerical simulation based on the two-phase flow theory was used to study the velocity and turbulence intensity distribution of mixed-water phase in the high-pressure nozzle.The effects of abrasive inlet position on the collection property of abrasive particles at the nozzle outlet and the abrasion of nozzle inner wall surface were analyzed,and improvement measures to reduce the wall abrasion were proposed.The results show that with the increase of the distance from nozzle central axis,the turbulence intensity of the mixed-water phase in nozzle decreases;however,due to the vortex at abrasive inlet,the velocity of mixed-water phase first decreases and then increases with the increase of this distance.When the abrasive inlet position is closer to the high-pressure water inlet,the convergence of abrasive particles at the nozzle outlet tends to first improve and then deteriorate,and a large number of abrasive particles accumulate at the junction of abrasive inlet and upper wall surface,causing the abrasion of nozzle inner wall.By employing a round-corner transition at the rear wall and upper and lower wall surface to improve the jet flow direction,the volume fraction of abrasive particles at the collection point is therefore reduced.