漆膜影响下滑动轴承性能分析

Analysis of Journal Bearing Characteristics under the Influence of Varnish

漆膜是润滑油中一种化学反应的产物。为了分析漆膜对滑动轴承性能的影响,将漆膜简化为轴承承载区内的突起状矩形积垢物,在Reynolds方程基础上,通过修改轴承间隙函数及其对角度的偏导数来考虑不规则间隙影响,应用有限差分法建立含漆膜滑动轴承性能计算模型,分析含漆膜轴承和无漆膜轴承内压力分布、油膜厚度、轴颈中心位置、温升等特性。结果表明,含漆膜轴承承载区内同时存在漆膜引起的台阶流动和轴承收敛间隙引起的挤压流动效应,台阶流效应改变了滑动轴承油膜压力分布特性和轴承承载特性,导致轴颈平衡位置发生改变;漆膜越厚,偏心率和偏位角越小;出现漆膜后,轴承最小油膜厚度减小,最大油膜压力增大,承载能力减小,润滑油温升增大,对轴承安全运行将产生不利影响;漆膜张角较小时,最小间隙附近台阶流动形成的动压效应明显,容易形成局部高压和高温,漆膜张角增大到一定程度后,漆膜对轴承性能的影响趋于平缓。

Varnish is the product of a chemical reaction within oil.In order to study the influence of varnish on bearing characteristics, babbitt varnish was simplified to be a rectangle protuberance in journal bearing load zone, Reynolds equa- tion was modified to consider the influence of irregular bearing gap by changing the gap function and its partial derivative to the angle, and simulation model to analyze journal bearing dynamics was set up using the finite difference method. Oil pressure distribution, film thickness ,journal position and oil temperature increase were calculated and compared between the bearings with and without the influence of varnish. It is found that the step flow effect caused by varnish and the squeeze flow effect exist in bearing load zone simultaneously. The step flow effect changes oil pressure distribution and therefore bearing load characteristic ,which leads to the change of journal position.Journal eccentricity and deflection angle turn to small with the increased varnish thickness. The smallest film thickness and load capacity are decreased while the maximum film pressure and oil temperature are increased under the effect of varnish.There is bad influence of varnish on the safe and reliable operation of bearing.The dynamic pressure effect nearby the smallest gap zone is clear if varnish angle is small ,which causes local high pressure and temperature.Influence of varnish on bearing characteristics tends to be slow with the increase of varnish antic.