Abstract: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 equation 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 angle.