水轮发电机组轴承结构对油雾外逸现象的抑制作用

为探究水轮发电机组在运行过程中出现的轴承油雾外逸现象,在不改变机组油系统工作原理、轴承整体结构和轴瓦数量的条件下,通过对挡油环增设4级迷宫密封结构,并在轴领顶端增设4个直径为8 mm的均匀分布通气平压孔来改进下导轴承设计结构.运用VOF两相流模型和SST k-ω湍流模型对下导轴承结构油气混合物流动特性进行数值模拟.根据结果分析发现,改进结构在相同运行条件下油雾外逸量减少了78.21%,提高了油箱内流场的稳定性,减小了润滑油中气泡数和体积;同时表明水轮发电机组轴承油雾外逸现象与油箱内外压力差和油箱与外界开放通道密封性能有密切关系.研究结果能够为水电站抑制轴承油雾外逸现象提供指导.

Study on restraining effect of bearing structure on oil mist escaping of hydro generator unit

To perform a deep investigation into the oil mist escaping from the bearing during the operation of the hydrogenerator,without changing the working principle of the oil system, the overall structure of the bearing and the number of bearing bushings, the improved structure of lower guide bearing was designed by adding 4-stage labyrinth seal structure to the oil retaining ring and 4 evenly distributed vent pressure holes with diameter of 8 mm to the top of shaft collar. The VOF two-phase flow model and the SST k-ω turbulence model are the important bases for the numerical simulation of the flow characteristics of the oil-gas mixture in the lower guide bearing structure.According to the analysis of the results, it is found that under the same operation conditions, the oil mist escape amount of the improved structure is reduced by 78.21%, the stability of the flow field in the oil tank is improved, and the number and volume of bubbles in the lubricating oil are reduced. At the same time, it is shown that the pressure difference between the oil tank and the atmoshphere and the sealing performance of the open channel between the oil tank and the outside are the important influencing parameters of the oil mist escaping from the bearing of the hydroturbine generator.The research results can provide gui-dance for hydropower stations to suppress the phenomenon of bearing oil mist escaping.