摘要
对工质为浑水时水泵与水轮机的空化与空蚀进行了试验,结果表明,泥沙表面缝隙中寄存有许多气核,当压力降低时气核膨胀形成气泡,进而脱离沙粒表面发生空化;当沙质、水温一定时,浑水的空化压力特性完全由站址所在地的海拔高度、泥沙质量浓度、泥沙粒径等3个要素决定;在前两个因素一定的情况下,泥沙颗粒越小,即泥沙越细时,初生空化压力与临界空化压力越高.浑水时气核数量远多于清水;浑水发生空化时,气泡溃灭引发的夹沙射流强度大于清水射流,由于这两个因素致使在含沙水流工作的水泵与水轮机,在相同的装置条件下,空蚀破坏较清水时强烈.目前,空化流场计算和空化数计算都存在着把空化压力取做海拔高度为零时清水的汽化压力的错误,使计算结果严重失实.
The experiment on cavitation and cavitation erosion of pump and turbine with silt-laden water as working medium was carried out.The experimental results show that lots of gas nuclei hiding in the gaps of sand surfaces grow up and form into the bubbles when pressure decreases,and then separate from the sand surface,cavitation happens finally.When sandiness and water temperature are constant,the cavitation pressure characteristics of silt-laden water depend on three important factors,the local altitude,sand mass concentration and sand radius.When the former two factors are constant,the inci-pient cavitation and critical cavitation pressure both increase with the decrease of sand radius.The gas nuclei number of silt-laden water is far greater than that of the clean water.When cavitation occurs in the silt-laden water,the jet-flow strength in sand water caused by the bubbles collapse is greater than that in the clean water.The two reasons above cause the cavitation damage of sediment-laden flow in water pump and turbine stronger than that of the clean water in the same device conditions.At present,the mistake that the vapor pressure of clean water at zero altitude is used to be of the cavitation pressure in the computation of the cavitating flow field and cavitation coefficient leads to serious inaccuracies of real results.
出处
《排灌机械工程学报》
EI
2010年第2期93-97,共5页
Journal of Drainage and Irrigation Machinery Engineering
基金
国家自然科学基金资助项目(50976124)
关键词
水力机械
水泵
水轮机
空化压力
空化
空蚀
hydraulic machinery
pump
turbine
cavitaition pressure
cavitation
cavitation erosion
