考虑界面滑移及局部紊流的船用艉轴承润滑特性研究

Lubrication characteristics of marine stern tube bearings considering wall slip and local turbulence

船用艉轴承常用高分子材料作为工作表面,润滑油在其与高分子材料的界面处具有极限剪应力,因此在高剪切工况下易发生界面滑移。同时,大型重载艉轴承偏心率较大,最大膜厚往往远大于最小膜厚,膜厚较大的区域可能发生局部紊流。为研究界面滑移和紊流对轴承性能的影响,本文提出一种考虑界面滑移和紊流的轴承分析模型,建立数值仿真流程,在此基础上分析界面滑移、局部紊流及两因素的耦合对轴承性能的影响。分析结果表明:界面滑移会降低轴承承载能力,减小最小膜厚,同时减小摩擦力;局部紊流则会提高液膜承载能力,增大其最小液膜厚度及摩擦系数;综合考虑两因素影响时,低速下界面滑移的影响占主导,随着转速升高,局部紊流对液膜厚度及摩擦系数的增大作用逐渐增强,逐步抵消界面滑移引起的液膜厚度及摩擦系数的减小。

Polymer materials are often used as the surface of marine stern tube bearings.Lubricating oil has limit shear stress on the polymer material surface,so wall slip may occur under a high shear condition.More-over,the eccentricity of a large heavy-duty stern tube bearing is large,so the liquid in the area around the minimum film thickness is laminar flow,and the local turbulence may occur in other areaa with a larger film thickness.In this paper,a lubrication model considering wall slip and turbulence was proposed,and the cor-responding numerical procedure was established.Based on the proposed model,the influence of wall slip and local turbulence on the performance of a marine stern tube bearing was analyzed.The results show that wall slip reduces the load-carrying capacity and decreases the minimum film thickness and the friction force,while local turbulence increases the load-carrying capacity,the minimum liquid film thickness and the fric-tion force.When the two factors are considered at low speed,the influence of wall slip on the bearing perfor-mance is dominant.With the increase of speed,the effect of local turbulence on the film thickness and fric-tion coefficient gradually increases,which gradually counteracts the decreasing of the film thickness and fric-tion coefficient due to wall slip.