Self-excited Oscillation of a Liquid Filled Rotor

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Recently many kinds of liquid filled rotor are used in a variety of industries, for example,superconducting generator filled with liquid herium, liquid cooled turbine shaft, ultra high speed liquid centrifuge and so on. In such rotors, it is well known that there exists an unstable rotating speed range over a critical speed caused by the coupling of rotor whirling motion and oscillation of an enclosed liquid.A large number of studies were done so far mainly on the mechanism of the self-excited oscillation of a rotor caused by free surface wave. But few studies are reported in connection with the oscillation caused by interfacial wave. So in this report, self-excited oscillation of a rotor filled with two kinds of immiscible liquid such as the combination of water and oil is investigated. The influence of density ratio between two kinds of immiscible liquid and the viscosity of the heavier liquid on the unstable rotating speed range is studied both theoretically and experimentally.This report is composed by 7 chapters. In chapter 1, the purpose of this research project is described. In chapter 2, related research are reviewed. In chapter 3, analysis on the motion of a enclosed liquid is described. Natural frequencies and modes are analyzed and compared with experimental results. In chapter 4, the procedure of deriving the fluid force acting on a rotor is described under the assumption of inviscid liquid. And at the end, the way of determining the unstable rotating speed range analytically is proposed. In chapter 5, the experimental apparatus and measurement technique are introduced. In chapter 6, theoretical results are compared with experimental results. In chapter 7, the results of this project are summarized briefly.