基于混合遗传算法的径向滑动轴承表面织构优化

在内燃机曲轴系统的径向滑动轴承表面设计了球形凹坑织构, 以改善润滑性能; 为了获得最大的轴承承载力和最小的摩擦因数, 提出了基于序列二次规划算法和遗传算法的混合进化优化方法, 构建了径向滑动轴承球形凹坑织构的优化模型, 对凹坑织构的分布位置和结构参数进行了全局寻优, 得到了给定工况下最优的织构角度和最大深度; 为了求解径向滑动轴承的承载力和摩擦因数, 考虑曲轴和轴承表面粗糙度对油膜流动的影响, 采用质量守恒的JFO空穴算法处理油膜的破裂和再形成行为, 基于平均Reynolds方程和Greenwood-Tripp微凸体接触方程构建了球形凹坑织构径向滑动轴承的混合润滑模型, 分析了球形凹坑织构的分布位置和结构参数(数量、面积率和最大深度) 对径向滑动轴承承载力和摩擦因数的影响。分析结果表明: 径向滑动轴承的承载力和摩擦因数是凹坑面积率的单调函数; 存在最优的凹坑织构角度和最大深度使得径向滑动轴承的承载力最大与摩擦因数最小; 当偏心率由0.3增加到0.7时, 轴承承载力的提升量由13.38%下降到0.62%, 摩擦因数的降低量由0.73%逐渐下降至负数, 因此, 当偏心率较小时, 球形凹坑织构能够有效降低径向滑动轴承的摩擦因数, 增大承载力, 当偏心率较大时, 球形凹坑织构无益于轴承摩擦因数的降低。

Surface texture optimization of journal bearing based on hybrid genetic algorithm

The spherical dimple texture was designed on the surface of journal bearing to improve the lubrication performance of crankshaft system in diesel engine. In order to maximize the loadcarrying capacity and minimize the friction factor of the bearing, a hybrid evolutionary optimization method based on the sequential quadratic programming and the genetic algorithm was proposed, and an optimization model was developed for the journal bearing with spherical dimple texture. The distribution location and geometry parameters of dimple texture wereglobally optimized to obtain the optimal angle and maximum depth of texture under given working condition. In order to solve the load-carrying capacity and friction factor of journal bearing, the influence of surface roughness on oil flow was considered, a mass-conservation JFO (Jakobsson, Floberg, Olsson) cavitation algorithm was used to address the rupture and reformulation of oil film, and a mixed lubrication model was developed based on average Reynolds equation and Greenwood-Tripp asperity contact equation. The influence of spherical dimple textures with various distribution locations and geometry parameters (number, area density, and maximum depth) on the load-carrying capacity and friction factor of journal bearing was investigated. Analysis result shows that the load-carrying capacity and friction factor are the monotonic functions of dimple area density. There exists optimal angle and maximum depth of dimple that can maximize the load-carrying capacity and minimize the friction factor. When the eccentricity rises from 0.3 to 0.7, the increment of load-carrying capacity changes from 13.38% to 0.62%, and the decrement of friction factor changes from 0.73% to negative value. Therefore, when the eccentricity is smaller, the spherical dimple texture can increase the load-carrying capacity and decrease the friction factor effectively, and when the eccentricity is larger, the spherical dimple texture is unbeneficial to decrease the friction factor of the bearing.