悬臂型多叶薄片气体轴颈轴承面接触承载机理研究

Multileaf gas foil journal bearings have the advantages of simple construction, reliable operation, easy processing and assembly. They have been applied in a wide range of high-speed rotating machineries such as air cycle machines for airplane.However, the existing theoretical models face the problem that the prediction about load carrying capacity is far less than the experimental results.. In this study, the cantilevered curved beam model is used, and a novel mechanical model of the supporting structure is proposed based on the assumption of area contact. Subsequently, the load capacity mechanism of the novel model is investigated. The research contents are as follows. 1. Aiming at the assembly and preload of the bearing, the foil-overlapping mechanical model and the journal-inserting preloaded mechanical model are built to obtain the initial conditions such as the initial film thickness distribution, the gaps between adjacent foils, the gaps between foils and bearing housing, which can be used for the analysis of area contact model. 2. The mechanical model considering the area contact between adjacent foils, foils and bearing housing is built up, and the corresponding algorithm flowchart is developed to obtain the elastohydrodynamic solution. 3. The evolution mechanism of area contact and its influence on load capacity are studied. 4. The theoretical model about dynamic performance based on the area contact model is established considering the perturbation of foils, and the effect of area contact on dynamic performance is analyzed. Finally, the test verification is performed.. The research results can improve the understanding about the load-bearing mechanism of multileaf gas foil bearing and enrich the theory system of gas lubrication.

悬臂型多叶薄片气体轴承具有结构简单、易于加工和装配、运行可靠等优点，广泛应用于飞机空气循环系统等高速旋转机械，但现有的承载建模理论存在预测结果远小于轴承试验结果的问题，造成了对该轴承的认识偏差，阻碍其应用。本研究采用悬臂弯曲梁模型，提出一种考虑面接触的全新支承结构力学模型并研究其承载机理。研究内容包括：1.针对轴承装配预紧过程，建立薄片装入的搭接力学模型和转子插入的预紧力学模型，得到气膜厚度、搭接薄片间以及薄片与轴套间的间隙分布等初始条件用于后续的面接触分析；2.建立同时考虑搭接薄片间、薄片与轴套间面接触的薄片变形计算模型，开发相应的算法流程进行求解；3.研究面接触的演化机理及其对轴承性能的影响规律；4.基于面接触模型，建立考虑薄片扰动的动特性计算模型并分析面接触对动特性的影响规律；最后进行试验验证。研究成果对于正确理解悬臂型薄片轴承承载机理、丰富和发展气体润滑理论具有重要的意义。

悬臂型多叶薄片气体轴承具有结构简单、易于加工和装配、运行可靠等优点，广泛应用于飞机空气循环系统等高速旋转机械，但现有的承载建模理论存在预测结果远小于轴承试验结果的问题，造成了对该轴承的认识偏差，阻碍其应用。本项目的主要研究内容和成果包括：1）基于接触力学建立了多叶悬臂薄片有预紧搭接装配力学模型。推导了圆弧形悬臂薄片主要组成单元“曲梁单元”的刚度矩阵。根据搭接精细几何形状构建悬臂薄片之间的接触间隙数学表达式，基于拉格朗日乘子法推导了悬臂薄片之间面接触状态下的接触势能表达式及其变分、微分表达式，为非线性变接触状态薄片变形求解奠定基础。2）引入转子预紧装配过程中与各叶悬臂薄片之间的“刚性-柔性”接触约束。推导了相应的接触势能、接触间隙向量与切向接触矩阵的表达式，完成了转子装配与静态转子加载过程的数值仿真。3）大载荷条件下，考虑了轴套对悬臂薄片的进一步支承约束。悬臂薄片在动压气膜力作用下，不仅会与相邻薄片之间发生面接触，也会在进一步变形过程中与轴套之间发生接触，导致结构刚度进一步增大。4）深入研究了悬臂型薄片轴承承载机理与承载特性。研究了悬臂薄片厚度、曲率半径、相邻薄片间的搭接比以及轴承径向间隙对轴承承载力、刚度的影响，也通过计算气膜压力、厚度分布、薄片变形与接触状态，分析了其相应的承载机理。5）搭建了悬臂薄片轴承静态特性实验台，进行了静态加载与运行实验研究。加工了悬臂薄片轴承试验件，进行了轴承的装配与加载实验。也通过高速相机拍摄到了轴承运行状态下悬臂薄片之间以及薄片与轴套之间的面接触效应，验证了理论计算的合理性与准确性。本项目的研究成果为多接触约束、复杂箔片结构力学性能理论分析提供理论基础；研究成果可以促进悬臂型箔片轴承与其他多接触约束、复杂箔片结构轴承的设计开发与产业应用。