Experimental study of the dynamic behavior of gas foil bearings and its constructive controllability

气体轴承可以用作小型和轻型涡轮机械的替代转子轴承类型，例如涡轮增压器或小型燃气轮机。特别是在非常高的速度和高工艺温度下，这种特殊形式的流体膜轴承使用气体代替油作为润滑剂。省去了传统的润滑系统，减轻了重量、维护和成本，并避免了过程介质受到润滑剂的污染。气体箔轴承（GFB）代表一种特殊类型的气体轴承。gfb采用弹性结构，最大限度地减少了传统气体轴承的一些主要缺点。这种弹性结构产生了额外的摩擦和阻尼，从而提高了稳定性。同时可以提高承载能力。优化GFBs动态性能的主要任务之一是尽量减少运行过程中发生的大的次谐波振动。当次谐波旋涡频率与系统固有频率重合时，会引起次谐波幅值的突然增加，这通常会导致损坏。减少GFBs振动的设计措施，导致阻尼和刚度的增加，已经存在。这些措施包括所谓的“垫片”。各种初步研究表明，次谐波振动的发生及其振幅受到垫片的影响。结果表明，在数值模拟的基础上，可以对旋涡振动的起始点进行保守的预测，这对利用GFBs设计转子是非常重要的。然而，缺乏数值模拟的实验验证。在提出的项目中，计划对不同GFB类型所需的线性化轴承参数进行系统的实验确定，以评估旋转频率。这一结果验证了用于参数确定的数值模型。该模型将用于旋翼动力学、稳定性和优化的进一步研究。在该项目中，建立了一个转子动力学试验台，可以系统地研究GFBs中转子的非线性振动行为。该实验将提供有关次谐波振动起始速度的信息，并对垫片等结构措施的有效性提供提示。总体结果将为各种类型的gfb的设计和研究提供高质量的数据，并为未来整个发动机模型（结构-壳体-轴承-转子）的仿真提供验证和验证。

Gas-bearings can be used as an alternative rotor bearing type for small and light turbomachinery such as turbochargers or small gas turbines. Particularly at very high speeds and high process temperatures, this special form of fluid film bearings that uses gas instead of oil as a lubricant. The omission of a conventional lubrication system reduces weight, maintenance and cost and avoids contamination of process media from lubricants.The Gas Foil bearing (GFB) stands for a special type of gas bearings. GFBs minimize some of the major drawbacks of conventional gas bearing using an elastic structure within. That elastic structure creates additional friction and damping and thus improves stability properties. At the same time the load capacity can be increased.One of the main tasks in the optimization of dynamic properties of GFBs is to minimize the occurring large, subharmonic vibrations during operation. A coincidence of the subharmonic whirl frequencies with a system natural frequency can cause a sudden increase in the sub-harmonic amplitudes, which often leads to damage. Design measures for a vibration reduction of GFBs, leading to an increase in the damping and stiffness, already exist. These measures include, among others, so-called shims. Various preliminary studies have shown that the onset of subharmonic vibrations and their amplitudes are affected by shims. Furthermore, it was shown that conservative predictions of the onset of whirl vibration, which is very important for a design of rotors using GFBs, can be made on the basis of numerical simulations.However, an experimental validation of numerical simulations is missing. Within the proposed project a systematic experimental determination of the required linearized bearing parameters of different GFB types in order to assess the whirl frequency is planned. This results in a validation of a numerical model for parameter determination. That valid model will be used for further investigations on rotordynamics, stability and optimization. During the project a rotordynamic test bed is built that allows a systematical investigation of particularly nonlinear vibration behavior of a rotor in GFBs. The experiments will provide information about the onset speed of the subharmonic vibration as well as give hints on the effectiveness of structural measures such as shims. The overall results will provide a high quality of data for the design and research of various types of GFBs and serve future simulations of whole engine models (structure-housing-bearing-rotor) for verification and validation.