Abstract:

During the operation process, there are always bubbles arising in the lubricating oil due to its own dissolution or external entry of air, which will influence its lubricating performances, thus, it’s significant to study the liquid-gas two-phase flow in lubrication systems. To explore the pressure fluctuation characteristics in the flow of lubricating oil with air, an unsteady simulation is carried out with ANSYS_CFX for oil-air two-phase flow in a lubricating pipeline system, and the reliability of the simulation is verified by comparing pressure data of different conditions with the experiment data. It turns out that, at the beginning, the interface between oil and air is destroyed by the disturbance of the flow and air is sucked into the oil to form the oil-gas two-phase flow; the pressure fluctuation at different sections of the pipe and the effects of flux on it are analysed. The results demonstrate that the fluctuation amplitudes of the average pressures on the pipe sections firstly increase and then decrease, along the streamwise direction with the maximum located near the outlet of the pump; the bubbles are broken into continuous and uniform small bubbles by the stirring effect of the pump, which weakens the strike of the flow in the outlet pipe, as a result, the fluctuation amplitude here is relatively small; as the flow rate enlarges, the period of pressure fluctuation decreases and amplitude increases.

Key words: lubrication system, oil-gas two-phase flow, pressure fluctuation, air volume fraction, flux, viscosity

摘要：

润滑油在工作过程中经常会由于自身溶解或外部进入空气而产生气泡，影响其润滑特性。因此，研究润滑系统中的气液两相流动特性具有重要意义。为了解含气润滑油在流动过程中的压力脉动特性，本文采用 ANSYS_CFX对一润滑管道实验装置内油气两相流动进行数值模拟，将不同工况下的压力计算结果与实验数据作对比，验证了数值计算方法的合理性，然后分析了管道不同位置的压力脉动以及流量对压力脉动的影响。计算结果表明，流动开始，油与空气的分界面受到扰动使得空气逐渐进入油中，形成油气两相流；沿着流动方向，管道截面上的平均压力的脉动振幅先增大后减小，最大值位于紧邻泵出口的监测面；两相流动中气泡受泵的搅拌作用破碎形成连续且均匀的小气泡，使出口管道内流动所受冲击更小，压力脉动相对较小；随着流量增加，压力脉动的周期减小，振幅增大。

关键词: 润滑系统, 油气两相流, 压力脉动, 含气率, 流量, 黏度