Theile, Andre Manuel (2024)
Model Validation for Air Foil Thrust Bearings.
Technische Universität Darmstadt
doi: 10.26083/tuprints-00027584
Dissertation, Erstveröffentlichung, Verlagsversion

Kurzbeschreibung (Abstract)

This work validates and extends a simulation model for an air foil thrust bearing, which belong to the class of hydrodynamic bearings with elastic bearing surfaces. The model can determine integral quantities such as load-carrying capacity and power loss of the bearing. Additionally, it can calculate pressure and temperature distributions as well as deformations of individual components. A validated simulation model is crucial for the design and understanding of the cause effect mechanisms in thrust bearings. To assess the validity of the simulation, the range of its applicability and the significance of the results are analyzed. Initially, the key influencing parameters are identified and consolidated into four key characteristics aimed at providing the most comprehensive description of the bearing. These metrics encompass the performance of the bearing in terms of load-carrying capacity and power loss, the thermal interaction of individual components, bearing stiffness, and the lubricant film distribution. Building on this foundation, various measurement devices are put into operation. Integral quantities such as load-carrying capacity and power loss are measured in the newly designed high-speed test rig. To validate the thermal behavior, thermal resistances are determined, and temperature distributions are measured in a separate experimental setup. Mechanical properties such as wear, mechanical friction coefficients, and bearing stiffness are investigated through a variety of test setups and suitable measurements. Furthermore, the simulation model is analyzed and extended in relevant areas. For this purpose, CFD simulations of the rotor environment are conducted, in order to implement heat transfer coefficients at the rotor. Furthermore, a simple wear model is incorporated into the simulation based on the analysis of the bearing’s running-in behavior. Additionally, the formulation of the thermal resistance of the bearing is enhanced. Simulation uncertainties can be represented based on the measured input parameters of the simulation model. These uncertainties are crucial in cooperation with experimental uncertainties for the successful validation of the simulation model. The validation process demonstrates good agreement between the simulation model and experimental results regarding the key characteristics of the axial bearing, including power loss, wear patterns, and thermal behavior. However, challenges arise in accurately representing the stiffness of the bearing due to the alignment process of the bump foils. This research significantly contributes to the understanding of the behavior and complexity of air foil thrust bearings. The introduction of a novel wear algorithm enhances the accuracy and realism of the model. The results emphasize the importance of refining and incorporating precisely determined input parameter into the model to ensure an accurate representation of real-world behavior.

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