抽蓄机组水导轴承润滑油系统非定常流动特性

Analysis of Unsteady Flow Characteristics of Lubricating Oil System of Water Guide Bearing for Pumped Storage Unit

抽蓄机组水导轴承润滑油系统在机组启动过程中易发生甩油溢油现象,极大威胁了机组的安全稳定运行。为探究甩油溢油原因,以某抽蓄电站机组水导轴承润滑油系统为研究对象,基于VOF多相流模型与Realizableκ-ε模型,开展额定工况下水导轴承内润滑油系统的三维非定常数值模拟,分析了开机过程中旋转油盆和水泵式毕托管内部的非定常流动特性。结果表明,润滑油系统外特性变化分为润滑油流动的初期形成过程与润滑油流动稳定循环过程两个阶段。初期形成过程中,旋转油盆内部整体上压力沿圆周方向均匀分布,在水泵式毕托管入口附近产生高压区,驱动润滑油向上方静止油盆流动;稳定流动循环过程中,内部润滑油流速沿半径方向逐渐降低,并在水泵式毕托管后方与水泵式毕托管进口处出现较大旋涡区。该现象易导致此处润滑油压力低于润滑油饱和汽化压力,可能引发润滑油雾化,进而从密封环处溢出。研究结果为探究抽蓄机组水导轴承润滑油系统出现的甩油溢油现象原因提供了理论分析与工程参考。

The lubricating oil system of water guide bearing of pumped storage unit is prone to oil spill during the starting process of the unit, which greatly threatens the safety and stability of the unit. In order to explore the cause of oil spill, this paper took the lubricating oil system of water guide bearing of a pumped storage unit as the research object, carried out three-dimensional transient numerical simulation of lubricating oil system of water guide bearing at rated conditions based on VOF multiphase flow model and Realizable κ-ε model. The analysis of unsteady flow characteristics of the oil slinger and the pitot tube was shown. The results show that the characteristic change of lubricating oil system can be divided into two stages, the first stage is the initial formation process of lubricating oil flow and the second is the stable circulation process of lubricating oil flow. In the initial formation process, the pressure inside the oil slinger, as a whole, is evenly distributed along the circumferential direction, accompanied by an area near the inlet of pitot tube of high pressure which drives the lubricating oil to flow to the upper stationary oil basin;In the process of stable flow circulation, the flow rate of internal lubricating oil gradually decreases along the radius direction, and a large vortex area appeared at the rear and inlet of the pitot tube. This phenomenon is prone to make the pressure of lubrication oil behind the pitot tube lower than the saturated vaporization pressure, which may cause lubricating oil atomization and overflow from the sealing ring. The research provides theoretical analysis and engineering reference for exploring the causes of oil spill in the lubricating oil system of water guide bearing of pumped storage unit.