低固相含量液流中磨蚀翼型空化特性研究

针对水力机械内部空蚀及泥沙磨损联合作用破坏问题，探索空化促进磨损破坏的方式。在闭式循环装置的收缩－扩散实验段中，采用激光-CCD系统获取低固相含量下空化场中翼型表面多个断面的空穴结构分布，分析了空穴结构空间分布规律及其初生、发展、脱落、溃灭的周期性行为特征。针对空穴结构分布，采用了一种基于统计原理的图像处理方法，获得了空泡云平均值及标准差值的灰度分布，前者为流场中各位置的空化程度，后者为各位置空泡云体积变化率的分布。结合已有的空蚀磨损研究成果认为，水力机械内部空化促进颗粒磨损的方式取决于空穴结构及其体积变化率在流场中的分布规律。

STUDY ON THE CAVITATION CHARACTERISTICS OF HYDROFOIL FOR CAVITAION AND SILT ABRASION IN FLOW OF LOW SOLID CONTENT

Aiming at the cavitation and silt abrasion of hydraulic machinery,the study explores the mode of cavitation enhancing silt abrasion.The images of the distribution of cavity in flow of low silt content on the surface of hydrofoil are recorded by a system of laser-CCD at different cross-sections in the converging-diverging test section of the close-circulated apparatus.The law of the variation with time and the periodic behavior of birth,development,falling off and collapse of the cavity is acquired by analyzing the images.The grey distribution of the average value and the standard variation of the vapor cloud volume at different sections are obtained by using a statistical image processing method,and the latter represents the distribution of the velocity of the change of the vapor cloud volume.Referring to the published results of cavitation and silt abrasion,the study indicates that the mode of cavitation enhancing silt abrasion is depended on the distribution law of the cavity and the velocity of the change of the vapor cloud volume in the flow field of hydraulic machinery.