State characterization of hydrodynamic plain bearings based on capacitive effects

• Applicants: Professor Dr. Alexander Hasse; Professor Dr.-Ing. Eckhard A. Kirchner
• Subject Area: Engineering Design, Machine Elements, Product Development
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 547186942

The aim of the application is to design and verify a measurement principle for identifying and classifying changes in the local gap geometry in technically relevant gap flows by measuring electrical capacities on the hydrodynamic plain bearing. Changes in the gap geometry in the form of misalignment and eccentricity can be caused by changes in load and speed. The measurement concept is based on the principle of an electrical capacitor, which is formed by an electrode surface on the bearing shell and the shaft, as well as the insulating lubricant. In the plain bearing of this application, the electrodes are arranged in segments in the bearing shell and protected against wear by a bonded coating. The particular challenge in using the capacitive electrical behavior of the plain bearing with segmented electrodes (GSE) is the consideration of the physical dependencies between pressure, temperature, lubricant viscosity and permittivity as well as their effects on the electrical capacitance. The project aims to develop a fundamental methodological understanding of how a corresponding capacitor network must be designed in order to determine the shaft position in the GSE and how a change in capacitance and temperature can be assigned to a changed gap geometry. For this purpose, there are 24 individual electrode segments on the GSE, which can be interconnected as required. This means that different capacitor configurations can be investigated in the GSE without having to manufacture a separate GSE for each. The influence of wear is not considered in this project. The following research questions are answered: 1. must the dependence of permittivity on fluid pressure and temperature be taken into account for the practically relevant operating range of a GSE? 2. can the behavior of real capacitors be approximated by simplified models so that the functional relationship between shaft displacement and capacitance of the GSE can be described compactly? 3. how must the capacitor network be designed in order to clearly identify the movement of the bearing? Which additional functions are opened up by additional capacitor segments? In order to investigate these research questions, the following sub-lines are defined: 1. implementation of the GSE, which can map different capacitor network configurations through appropriate circuitry. 2. generation of a validation data set through practical capacitance measurements on the sensor sleeve bearing. 3. modeling of the plain bearing system based on the Reynolds equations to determine the pressure and temperature field and to determine the permittivity distribution in the lubrication gap. 4. inversion of the developed modeling method in order to identify the lubrication gap geometry on the basis of measured capacities. 5. optimization of the segment shape of the capacitor network.

• DFG Programme: Research Grants