掺气减蚀机理的研究进展及讨论  

Overview and discussions on the advances in the mechanism studies of air entrainment against cavitation erosion

作　　者：张法星[1] 徐建强[1] 徐建军[1] 汪振[1] 

机构地区：[1]中国水电顾问集团华东勘测设计研究院,杭州310014

出　　处：《水力发电学报》2010年第2期7-10,30,共5页Journal of Hydroelectric Engineering

基　　金："十一五"国家科技支撑计划项目(2008BAB29B04)

摘　　要：本文对空蚀机理及其影响因素进行了总结,综述了掺气量对空化初生和空蚀的影响,在估算空化泡的溃灭时间、冲击波的传播速度及衰减规律、微射流的直径及其速度、微射流对固壁的冲击压强和持续时间的基础上,分析了掺气减蚀机理的研究进展及一些不足之处,水流掺气会导致初生空化数和空化数都增加,引起水中声速变化,但这些不能合理地解释掺气减蚀的原因。边壁附近的空化泡溃灭时,与周围空气泡的偶合作用,会改变微射流的方向,降低微射流的速度,增加空泡溃灭时间,减小冲击压强,消减传递到固壁的高强冲击荷载而减免空蚀破坏。掺气减蚀的原因是固壁附近空化泡与气泡的相互作用和含气型空化的增加更为合理。This paper summarizes the mechanism and influencing factors of cavitation erosion and the effects of air content on incipient cavitation number and cavitation damage. The advances in aeration mechanism studies against cavitation erosion are analyzed by using the concepts of collapse time of a cavity bubble, propagation speed and attenuation law of shock waves,diameters and velocities of micro-jets or re-entrant jets, and impact pressure and its duration of a micro-jet acting on solid wall. These studies revealed that aeration causes an increase in incipient cavitation number and flow cavitation number,and also a significant change in sound speed. Despite all the findings and efforts of previous investigators,there exist yet many unknowns of the mechanism. There is no explanation that satisfactorily tells us why aeration can reduce cavitation damage. In fact the interaction of a collapsing cavity bubble near solid wall with the air bubbles nearby could be crucial. This interaction may change the direction of re-entrant jet,reduce the micro-jet velocity,increase the collapse time, and decrease the shock wave pressure and the peak load on the small surface area impacted. This explanation of why air entrainment can migrate cavitation erosion seems more reliable.

关 键 词：水力学 掺气减蚀 综述 空化泡 气泡 

分 类 号：TV131.3[水利工程—水力学及河流动力学]