复杂空间由运动体诱导的润滑脂/基础油/空气多相流动规律研究

Grease lubrication has a very wide range of applications. Comparing with oil lubrication, grease lubrication has faults that are not suitable for high speed and poor lubricity, but it has the advantage to make bearings having simple periphery structure, smaller size, lighter lightweight and easy operation. Grease is composed of three parts, base oil, thickener and additives. Grease lubrication is partly due to the role of the thickener, other due to the lubrication characteristics of the special combination of base oil and thickener. They are different from the lubrication characteristics of base oil or the thickener along. Special lubrication mechanism is decided by special structure of grease. Understanding of the mechanism of lubrication is very helpful to improve the quality of grease, to reduce consuming of grease, to select lubrication reasonably, to decrease filling amount of grease and to design the most appropriate structure for rolling bearings. The flow of grease, oil and air in the working space determines the dynamic replenishment of the lubricant in rolling contacting, which is the lubrication mechanism of grease, until now it has not been reached a consensus, and that how the lubricants move to the contact area is still in a state of qualitative description. The typical characteristics of grease flow in the working space are the complex space and the multiphase flow induced by the moving elements. At the same time, the characteristics of the nonlinear rheology of the lubricating grease results in that the flow is very complicated in the working space. Under condition that the reported researches on the flow of grease in rolling bearing are very few, the project takes the theoretical analysis, numerical analysis and experiment method to carry out the investigations on four aspects: (1) induced flow characteristics and their descriptions of grease; (2)the phenomenon that base oil and thickener separate form grease; (3) the mass transfer phenomena and their descriptions of the base oil and the thickener in the grease flow induced by movement of elements; (4) the effect mechanism of moving element induced air flow on flows of base oil, thickener and grease. Project will capture the interfaces between base oil, greaseand air by CT imaging. The concentrations of oil and thickener are measured by infrared scopometer. The experimental results of multiphase interfaces are used to correct the numerical model, through repeatedly modifying numerical model and comparing the numerical results to the experimental results, the numerical model could be established finally. Through the studies of the above four aspects, the multiphase flow characteristics of grease/ base oil/air induced by the moving element in complex space are obtained. The key basis of lubrication mechanism of grease would be revealed. The basic data which can be used to study grease, optimize the design of the workspace of lubricating grease is obtained.

润滑脂润滑的场合非常广泛，约80％的滚动轴承使用润滑脂润滑。润滑脂、基础油及其空气在其工作空间的流动决定着滚动接触区润滑剂的动态补给。该补给过程就是润滑脂润滑的机理，直到现在还没有达成共识。润滑脂、基础油及其空气在其工作空间的流动属于运动体诱导的多相流流动。加之润滑脂的非线性流变学特性，该流动非常复杂。在鲜见系统研究报道的现状下，项目采用理论分析、数值分析和实验相结的方法拟开展四个方面的研究：（1）做诱导流动润滑脂的流动规律及其描述；（2）基础油、稠化剂脱离润滑脂现象；（3）诱导流动润滑脂内的基础油和稠化剂的传质现象及其描述；（4）运动体诱导空气流动对基础油、稠化剂、润滑脂流动的作用机理。渴望获得：复杂空间由运动体诱导的润滑脂/基础油/空气多相流动规律；能揭示润滑脂润滑机理的关键基础依据；能用于研究润滑脂、优化设计润滑脂工作空间的基础数据。从而，项目结果具有较大的学术意义和较高的实用价值。

滚动轴承内部流动环境非常复杂，获得滚动轴承润滑脂/稠化剂/空气的流动规律非常困难，针对传统方法难以获得轴承内部流动的实际情况，本项目采用CT方法和数值模拟相结合的办法去探索滚动轴承内部润滑脂/稠化剂/空气的流动规律。通过深入细致研究获得的主要进展是：明晰了跑合阶段滚动轴承脂润滑内部润滑脂，空气，油膜的作用过程：轴承内部随着跑合的进行润滑脂被挤出滚道，大量润滑脂堆积在保持架周围，同时随着润滑脂的减少，在轴承内部空气含量增加使滚动体油膜厚度也在减薄；明晰了正常运转滚动轴承脂润滑内部润滑脂，空气，油膜的作用过程：在正常运转阶段，滚动体表面油膜比跑合阶段较薄，同时，滚动体会始终有一侧和保持架上的润滑脂直接接触，能够补充基础油在润滑中的消耗，对滚动轴承持续润滑起到保障作用；探明了润滑脂传质分离特性和传质规律：当转速较低时，经过较长时间运行，基础油传质现象明显，当转速较高时，基础油传质经历了先高后低的变化；揭示了滚动轴承脂润滑的润滑机理：当轴承高速转动时，滚动体和内圈转速较大，而在滚动体间隙靠近内外圈，尤其是外圈附近，润滑脂并不会随转速的提高而速度相应提高，润滑脂出现分层现象。在离滚道边缘大约2/3的位置处，会出现润滑脂的分层现象，这就导致润滑脂在速度高的位置由于基础油的迁徙而贫油。.项目累计在国内外发表论文7篇，已被SCI收录1篇，EI收录1篇，发明专利4项；培养硕士研究生4名。