Self-excited Oscillation of a Liquid Filled Rotor

近年来，各种充液转子被广泛应用于各种工业领域，如充液超导发电机、液冷涡轮轴、超高速液体离心机等。众所周知，在这类转子中，由于转子旋转运动和封闭液体的振荡耦合，在超过临界转速时存在一个不稳定的转速范围。迄今为止，大量的研究主要集中在自由表面波引起转子自激振荡的机理上。但有关界面波引起的振动的研究报道很少。因此，本文研究了充有油水两种不混相液体的转子的自激振荡问题。从理论上和实验上研究了两种不混相液体的密度比和较重液体的粘度对不稳定转速范围的影响。本报告共分七章。在第一章中，描述了本研究项目的目的。第二章对相关研究进行了综述。第三章对密闭液体的运动进行了分析。对固有频率和固有模态进行了分析，并与实验结果进行了比较。在第四章中，描述了在无粘性液体的假设下，推导作用在转子上的流体力的过程。最后，提出了解析确定不稳定转速范围的方法。第五章介绍了实验装置和测量技术。第六章对理论结果与实验结果进行了比较。第七章简要总结了本项目的研究成果。

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.