Analysis And Experimental Study On Incipient Cavitation Within Jet Pumps

Three parts are mainly involved. First one, manifold factors which affect cavitations inception are summed up from macroscopically view. Second one, the causation of cavitation inception is analyzed from the microcosmic view, furthermore, the formula, which is used to judge cavitation inception, is deduced on the base of control equation of jet pump. Third one, the corresponding comparisons and conclusion are give out after the experimental study. Finally, the problem of cavitation parameters is discussed specially.The dissertation consists of six chapters, and the primary contents are as follow:In chapter 1, the background of the task and the contents needed research are reviewed.In chapter 2, some classical problems are generally discussed in the research of cavitations, such as the tensile strength of a fluid, the bubble size infection of cavitation inception, scale phenomena, and so on.In chapter 3, the equation team between the pressure and velocity in jet pump flow field are educed, which are based of the hydro mechanical dynamic theory and the various characteristic in jet turbulent boundary layer.In chapter 4, the experimentation of incipient cavitation in a transparent jet pump has been done and the data is computed. The data of the experiment indicates that there are many factors influencing the incipient cavitation in jet pump, including the work pressure, the jet flow velocity, suction port pressure, the ratio of area and so on. Tow types of incipient cavitation in jet pump have been discovered by the observation. One is pressure incipient cavitation which is induced by the pressure reducing, and the other is velocity incipient cavitation which is induced as a result of the increased difference between the primary jet and the second flow.In chapter 5, the problem of cavitation parameters is discussed specially. Firstly, many cavitation parameters which were presented to describe the cavitation flow within a jet pump are introduced in the chapter. Secondly, the two representative parameters, which are cavitation parameters σ and cavitation flow rate ratio q_k are compared, and the correlation between the two parameters was studied theoretically. It is found that σ is more steady but indirect, while q_k predict limitation status directly and easy to bedetected. q_k is better than σ in the prediction of occurrence of limitation status. Finally, the chapter poses a cavitation parameter to connect the flow ratio and the pressure ratio.In Chapter 6, all works done in this paper are summarized and the suggestion of further researches is given.