Numerical And Preliminary Experimental Studv Of Liquid Nitrogen Cavitation

The researching method of water cavitation flow was extended to analyze the more complex cryogenic liquids cavitation phenomena in this thesis. However, because of the thermosensible properties of cryogenic liquids contrast to the non-thermosensible fluids such as water, the numerical methods for these two types of fluids show the difference. The thermal effects of cryogenic liquids has to be taken into account of, which makes the cavitation of cryogenic liquids show special characteristics, such as the significantly temperature depression, mushy interface and decreased intensity of cavitation under similar conditions for water cavitation. The researching significance is to benefit the improvement of the stability, mechanical properties and service life of machinery operating in cryogenic liquids.Firstly, this paper investigated the studies in the bubble growth, cavitation model, thermal effects considerations for cavitation model over the world. In the chapter two, we developed a bubble growth model of the complete process. The model based on Rayleigh’s bubble growth model in an extensive uniformly superheated liquid, which is controlled by inertial force. And then we quantitatively calculated the impact of liquid surface tension against the rate of bubble growth at thermal control stage. Finally, the P-Z model, F-Z model, together with multiple sets of experimental data was used to validate the results of our model. The comparison indicates that in order to prove the accuracy of model, the effects of surface tension cannot be ignored.In chapter three, we used Rayleigh-Plesset equation, thermodynamic chemical potential and the homogeneous nucleation theory to develop a new cavitation model, named dynamic cavitation model (DCM). The model modified the unreasonable assumption of full cavitation model that the bubble radius is constant in the cavitation process. An expression related the bubble radius with the pressure is proposed with the assumption that the gas and liquid phases always being in thermodynamic equilibrium. The DCM is validated by simulating quasi-steady cavitation in blunt body for water and in hydrofoil and ogive for Liquid nitrogen (LN2) and Liquid hydrogen (LH2). The computational results accord well with the experimental data reported by NASA as well as the numerical calculations with full cavitation model (FCM). And for the cases of complex pressure distribution, DCM has better results relative to the FCM.Finally, experimental studies on visualization of cavitation of LN2attempted to be conducted in this paper. We try our best to finish the design of experimental setup, including the selection of main components, design of the measurement and control system. The experimental studies are performed. However, the results were not so ideal, even unacceptable. The reasons were presented in detail, which primarily comes from the high-required insulation conditions.This project is funded by the National Science Foundation(No.50706042).