单进口后混式射流粉碎中多相流混合机理及加速特性

摘要

In order to deeply understand the super fine crushing technology of rear-mixed high-speed water jet flow,the mixing and jetting behavior of gas-liquid-solid three phases in acceleration tube with various diameter were investigated by using numerical simulation and crushing experiment methods.Mixing mechanism and acceleration performance of multiphase mixture jet flow were explored,and particles distributions in acceleration space were obtained.The result showed that aeration and entrainment effects of jet flow turbulent motion were the inherent mechanism of mixed attached phase.There existed many partition zones in the rear-mixed jet flow for particle acceleration.Whereby the nearer to the potential flow zone,the stronger the impact energy.Accordingly,optimizing configuration of the optional nozzle diameter with the acceleration tube diameter could force the particles near or enter the potential flow zone,whereby effectively improving grinding yield efficiency.The particles in space distribution within the acceleration tube were in the highest contents in high-efficiency acceleration zones of the outer and inner layers.As a result,the nearer to the potential flow zone,the fewer the particles.The particle contents in the air flow zone increased with increasing acceleration tube diameter.It was difficult for the particles to enter the ideal acceleration zone so that most of the particles were accelerated by relying on the highefficiency acceleration zone of the inner and outer layers.In the case of maintaining the flowing morphological state of free jet flow,the grinding yield efficiency decreased with increasing acceleration tube diameter.Accordingly small tube diameter was of better constraint and concentration functions for water jet flow energy and particle motion space.%为了深入了解后混式高速水射流超细粉碎技术,以4种加速管管径条件下的液、气、固三相混合射流为对象,利用数值计算和粉碎实验相结合的方法,研究了多相混合射流相间的混合机理和加速特性,探讨了颗粒在加速空间中的分布规律.结果表明:水射流紊动掺气和卷吸作用是混合附加相的内在机理；混合射流对颗粒的加速存在分区,越靠近势流区冲击能量越大,优化喷嘴直径与加速管管径配置,迫使颗粒靠近或进入该区域可有效提高粉碎产率.颗粒在加速管内的空间分布为外层、内层高效加速区内含量最高,越靠近势流区颗粒含量越少,气流区内颗粒含量随加速管管径增大而增大.颗粒很难进入理想加速区,大部分仍依靠内、外层高效加速区加速.在保持自由射流流动形态的情况下,粉碎产率随加速管管径增大而下降,小管径对水射流能量和颗粒运动空间均具有更好的约束集中作用.