Theoretical Study on Oil Reduction in Porous Oil Bearings With Running Time

多孔油轴承随运行时间减油的理论研究

• 批准号: 15560114
• 负责人: KANEKO Satoru
• 金额: $ 2.37万
• 依托单位: Nagaoka University of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15560114/
• 关键词: Porous oil bearings; Oil saturation; Liquid-gas interface; Two-face flow; Capillary pressure; Relative permeability; Leakage flow rate; 表面張力; 移動境界面; 飽和度; ガラス焼結体; 不飽和流れ

The purpose of the present study is to suppose a theoretical model predicting the time variation of oil content within the porous journal bearings, which operates with only the oil initially impregnated within its structure. In the bearing clearance, the liquid-gas (oil-air) interface is moved due to the hydrodynamic pressure in the oil film, which is governed by the modified Reynolds equation including a so-called filter term, and its velocity is solved as a problem of "moving boundary". In the porous matrix, the two-phase flow consisting of oil and air is assumed. The filter velocities of oil and air are governed by Darcy's law with relative permeability, which is a function of local oil saturation, and they are significantly influenced by the capillary pressure in the unsaturated region. The distributions of the oil saturation both in the bearing clearance and in the porous matrix are calculated by solving the unsteady-state continuity equations for the two regions, and the equations governing the velocities both of the liquid -gas interface in the bearing clearance and of the oil and air flows in the porous matrix.The results are summarized as follows :(1)Oil content within the porous bearings is reduced steeply just after the start of operation. After that, it decreases gradually with the running time and tends to approach a constant value. This time variation of oil saturation in the porous matrix qualitatively agrees with that shown in the conventional experimental studies.(2)Oil reduction within the porous matrix is mainly induced by the oil-film pressure in the bearing clearance, whereas it is suppressed by the capillary pressure, which contnbutes to keeping the oil in the porous matrix.(3)The surface tension at liquid gas interface in the bearing clearance would also influence the oil saturation in the porous matrix and it will contribute to seepage of oil from the porous matrix into the bearing clearance.

本研究的目的是假设一个理论模型，预测多孔轴颈轴承内的含油量的时间变化，它的运作，只有最初浸渍在其结构内的油。在轴承间隙中，由于油膜中的流体动压，液-气（油-气）界面发生移动，其速度由包含所谓过滤项的修正Reynolds方程控制，并作为“移动边界”问题求解。在多孔介质中，假设油、气两相流动。油和空气的过滤速度受达西定律控制，相对渗透率是局部含油饱和度的函数，并且它们受到非饱和区毛细管压力的显著影响。通过求解轴承间隙和多孔质基体的非稳态连续性方程，以及轴承间隙中液-气界面的速度方程和多孔质基体中油、气的流动方程，计算了轴承间隙和多孔质基体中含油饱和度的分布，结果表明：（1）多孔质轴承在刚开始工作时含油量急剧下降;之后，它随着运行时间逐渐减小，并趋于一个恒定值。这种多孔基质中含油饱和度随时间的变化与常规实验研究结果定性一致。（2）多孔基体中的减油主要是由轴承间隙中的油膜压力引起的，而毛细压力的存在则抑制了减油的作用，从而使油保持在多孔基体中。（3）轴承间隙中液-气界面的表面张力也会影响多孔基质中的含油饱和度，并有助于油从多孔基质向轴承间隙中的渗流。