Thermal Characterization of a Gas Foil Bearing—A Novel Method of Experimental Identification of the Temperature Field Based on Integrated Thermocouples Measurements

Abstract

Maintenance of adequate thermal properties is critical for correct operation of a gas foil bearing. In this work, the authors present the results of the experimentally conducted thermal characterization of a prototype installation of the bearing. A novel method of temperature identification, based on integrated thermocouples readings, has been employed to determine the thermal properties of the specialized sensing top foil mounted in the tested bearing. Two measurement campaigns have been subsequently completed, applying freely-suspended and two-node support configurations, to gather complementary knowledge regarding the bearing’s operation. Apart from the rotational speed and temperature field measurements, the authors have also studied the friction torque and the shaft’s journal trajectories based on its radial displacements. The temporal courses for the above-mentioned quantities have enabled inference on the effects present during run-up, run-out and stable state operation at a constant speed. As confirmed, the applied distribution of the integrated sensors allows for temperature readings on the entire outer surface of the foil, and therefore, provides useful data for the bearing characterization. The work is concluded with presentation of the recommended directions regarding future improvements of the proposed measurement technique and more comprehensive study of the bearing’s characteristics.

A Novel Measurement Approach to Experimentally Determine the Thermomechanical Properties of a Gas Foil Bearing Using a Specialized Sensing Foil Made of Inconel Alloy

“…Adequately, several case studies were selected for more comprehensive analysis based on the temporal plots drawn for the experimental readings of the temperature, as discussed in detail in Section 4. As previously experienced by the authors, the temperature may be considered a reliable indicator of the current operational state of the bearing [43].…”

“…To conduct the current research on the thermomechanical characterization of GFBs, the authors have extended the measurement capabilities of the previously investigated bearing's prototype installation, which is described in the work [43]. In the present work, the strain bridge modules were considered for the deformation measurements.…”

“…First, the temperature and strain readings were acquired and analyzed only for the central crosssection of the tested bearing. Moreover, the floating configuration without the external load was investigated, which stood for the first step of the analysis-prior to the planned use of a two-node support configuration of a GFB [43]. Next, significant geometric modifications of the foils' geometry, with the intentionally introduced gaps (incisions) in the bump foils, as well as the measurement method used to identify temperature and strain, made the proposed technical solution not yet ready to be implemented in commercial cases.…”

Application of piezoelectric composites to control operation of a gas foil bearing – prototype design and testing

“…• investigation of the two-support configuration of a GFB making use of the developed multifunctional top foil [5],…”

“…One of the adequate choice regarding the type of the suspension nodes are gas foil bearings (GFB) [1,2]. These bearings can be used at very high rotational speed, i.e., up to several hundreds of thousands rpm, also for a wide temperature range [3,4,5]. Figure 1 shows the cross-sectional view of a typical radial GFB.…”