水轮发电机组下导轴承油雾成因分析

Analysis on the Causes of Oil Mist in the Lower Guide Bearings of Hydrogenerator Units

为了研究水轮发电机组下导轴承油雾成因和机理,设计了抑制油雾逸出的新型轴承结构。运用VOF两相流模型和SST k-ω湍流模型,基于有限差分法,从流场特性、温度特性和相分布等方面分析了轴承油雾形成的原因和流动特性。结果表明:下导轴承的油雾形成主要与轴承结构相关;轴领内外两侧空腔的巨大压力差为油雾的逸出提供了驱动力,下导轴承挡油管缺乏密封结构,巨大空腔为油雾提供了逸出通道,最终导致油箱油雾大量逸出;轴瓦与轴领的摩擦生热导致部分润滑油气化形成气态油雾,油雾从轴领与挡油管之间的空腔散发出去。

In order to study the cause and mechanism of the oil mist of the lower guide bearing of the hydrogenerator unit,a new bearing structure was designed to restrain the oil mist from escaping.The VOF two-phase flow model and the SST k-ωturbulence model were used to analyze the causes and flow characteristics of bearing oil mist from the aspects of flow field characteristics,temperature characteristics and phase distribution based on the finite difference method.The results show that the oil mist formation of the lower guide bearing is mainly related to the bearing structure.The huge pressure difference between the inner and outer cavities of the shaft collar provides driving force for the escape of oil mist,and the lower guide bearing oil baffle tube lacks a sealing structure,the huge cavity provides an escape channel for the oil mist,which will eventually cause a large amount of oil mist to escape from the fuel tank.The frictional heat between the bearing bush and the shaft collar causes part of the lubricating oil to vaporize to form gaseous oil mist,which is emitted from the cavity between the shaft collar and the oil baffle tube.