涡轮增压器浮环轴承贫油失稳模型及边界条件研究

Floating ring bearings in the turbocharger generally work under extreme conditions such as high temperature and high velocity. The floating ring separates the hydrodynamic oil film into inner and outer films. Thus not only the degree of freedom of rotor vibration is increased, but also a rather complicated failure mechanism is resulted. Aimed at the new findings of oil starvation in the inner film of the floating ring bearing, a theoretical investigation will be conducted in this study on the internal structural parameters and external working conditions that would cause oil starvation based on the knowledges of fluid, rotordynamics, tribology and thermodynamics. A coupled mathematical model of fluid-solid-thermal will be developed to reveal the boundary condition of the oil starvation and instability in the inner oil film. In order to verify this phenomenon, a approach to measure the pressure distribution in the inner oil film will be originally investigated and the test rig simulation will also be originally achieved. The validated functions of oil film pressure distribution will then be introduced into the multi-fields coupled rotordynamics model to develop a multi-fields coupled mathematical model for the oil starvation and instability of the floating ring bearing. The functional relationship between the internal characteristics and external performances could then be clarified. This study will reveal the affects of such parameters as bearing clearances, velocities of the shaft and the floating ring, lubricant feed pressure, lubricant viscosity, contamination, temperature, et al on the disciplines of the oil starvation and instability of floating ring bearing so as to provide a theoretical support for the improvement of the reliability of floating ring bearings.

涡轮增压器中的浮环轴承工作在高温高速的极端环境下，浮环将动压油膜分为内外两层，增加了转子振动自由度，也使其失稳机理分析变的异常复杂。本研究针对最新发现的浮环轴承内油膜贫油失稳现象，综合利用流体力学、转子动力学、摩擦学和热力学知识，从理论上研究浮环轴承产生贫油失稳的内部结构参数和外部运行参数条件，建立浮环轴承与转子振动的流固热耦合数学模型，探索内油膜贫油失稳产生的边界条件；为验证贫油失稳现象，本研究还将首次探索内油膜压力分布检测方法，并首次实现浮环轴承贫油失稳台架模拟；然后将经过验证的内外油膜分布函数引入到多场耦合的转子振动模型中，建立起一个多场耦合的浮环轴承贫油失稳数学模型，进而阐明失稳过程中内部特征和外部表现之间的函数关系。该研究将揭示轴承间隙、轴与浮环转速、润滑系统压力、油液粘度、污染程度、工作环境温度等参数对浮环轴承贫油失稳的影响规律，从而为提高其可靠性提供理论依据。

高温高速的工作环境使浮环轴承成为涡轮增压器转子系统的薄弱环节和故障高发部件。大量的试验证实，有时在油质良好的润滑情况下，浮环轴承仍然会出现内油膜供油不足、轴承磨损甚至烧蚀的现象。这种贫油现象对涡轮增压器运行的稳定性和可靠性造成了严重的影响。.本项目对浮环轴承在充分润滑和贫油润滑条件下的润滑机理进行了理论分析，利用数值方法联立求解了表征内外油膜压力分布的Reynolds方程、膜厚方程和浮环弹性变形方程，推导了内外油膜承载力、流量和注入内油膜的压差注油量的表达式，建立了贫油润滑状态下的内油膜压力分布模型。研究结果表明：在贫油润滑状态下，随着供油流量的减小，轴颈偏心率增加，油膜起始角度增加，油膜终止角度减小，完整油膜覆盖区域缩小，油膜厚度变薄。当供油流量不变时，增加负载会加剧贫油润滑现象。.建立了浮环轴承-基础-转子系统的多自由度动力学模型，推导出浮环轴承轴承支承反力的非线性表达式。采用近似解析和数值积分相结合的方法对转子系统在贫油润滑、碰摩以及磨损状态下的振动进行计算。归纳出浮环轴承的摩擦润滑状态对转子在时域、频域的振动信号以及运行稳定性规律的影响。.对传统的转子-滑动轴承试验台进行了改造，利用MEMS传感技术，研制出可置于转子上的专用传感元件来完成压力和温度信息的感应与记忆，通过在轴心设置传递单元完成信息的传递，结合外接的高速信号采集系统进行信号采集，实现了从转子上对浮环轴承内圈油膜压力分布和温度分布的测量。同时开发了用于油膜压力场、温度场以及油膜动静特性等参数可视化的信号处理软件。.本项目的研究通过理论分析与试验研究相结合的方法揭示了涡轮增压器浮环轴承与转子系统的结构参数与运行参数对浮环轴承贫油失稳的影响规律，为提高涡轮增压器运行的可靠性提供了理论依据，具有重要的科学意义和工程实用价值。