Abstract: In order to solve the problems of fine particles agglomeration which caused the minimum limit size by grinding, taking advantages of the effect of ultrasonic dispersion and cavitation in the fluid phase, the influences of ultrasonic cavitation micro jet-flow near the rigid walls on crush fine particles were conducted. The effective breakage distance between the cavitation bubble and the rigid wall was calculated,when a fine particle was impacted by the micro jet-flow. The effect of frequency, ultrasonic pressure, and media ball size on micro jet-flow velocity were discussed and ten kinds of tests under different conditions were conducted herein. The SEM technique was used to characterize the powder morphology. The key parameters of the particle size distribution such as median particle diameter D50, 10% cumulative particle diameter D10 and specific surface area（SSA） were analyzed. The theoretical analysis is basically consistent with the experimental results. Results show that the breakage rate of fine particles below 800 mesh may reach 79.35% and production rate more than 10,000 mesh may reach 12.84% after parameter optimization. The media ball area has a greater effect on the breakage rate than that of the power, media ball size, and the mass concentration. The effect of crushing fine particles may be effectively improved by optimizing the parameters of the ultrasonic cavitation micro-jet flow and by increasing the surface area of the media ball.

Key words: ultrasonic cavitation, micro jet-flow, near rigid wall, fine particle breakage, scanning electron microscope(SEM) image

摘要： 针对微细粉体“团聚”导致粉磨极限的问题，在液相环境下利用超声的分散和空化冲击作用，开展了近壁面超声空化微射流对微细颗粒破碎作用的研究。通过理论计算空化微射流冲击微细颗粒破碎的有效作用范围，从空化泡溃灭速度的角度分析了超声频率、声压幅值、介质尺寸等主要参数对微射流强度的影响；结合物料质量浓度、介质尺寸、介质面积和功率等影响因素的微细颗粒超声空化破碎正交试验，并利用SEM观测粉体形貌，分析了颗粒中位粒径D50、10%体积累积粒径D10和比表面积（SSA）等分布特性。参数组合优化后获得了粒径小于800目的微细颗粒，破碎率高达79.35%；粒径大于10 000目的极细颗粒产率高达12.84%。从提高微细颗粒破碎率的角度，发现介质面积是主要影响因素，功率次之，其次为介质尺寸和物料质量浓度。试验结果与理论研究成果基本一致，表明优化超声空化微射流参数与增加介质壁面面积等方法可有效提高微细颗粒的破碎率。

关键词: 超声空化, 微射流, 近壁面, 微细颗粒破碎, 扫描电子显微图