The paper discusses the research on foil bearings with antifriction coating manufactured from synthetic materials. The tests were carried out on a special test stand of our own construction, designed with the use of numerical analysis. In the course of the experimental studies, the test stand was set up in two configurations: with one or two foil bearings. The measurements were done, which focused on temperature distributions with the aid of thermocouples and thermovision camera. The measurements were being performed under varying conditions of bearing operation. The conducted experiments permitted to verify the durability, thermal characteristics, and dynamic performance of foil bearings in different configurations. An original method to measure temperature of a top foil has been worked out.

The foil bearing consists of parts made of very thin, properly shaped foils. Usually, it is very difficult or even impossible to measure the vibrations of these elements during the bearing operation using traditional sensors. Therefore, the authors of this article have proposed an entirely new approach to this issue. This article discusses the analysis of vibrations of the structural supporting layer of a gas foil bearing at high rotational speeds. Instead of using a traditional method to measure the bearing journal movement, the measurement was performed using an ultra-high-speed digital camera. This type of measurement was used for the first time to analyse foil bearing displacement. It turned out that doing so can give a far more vibrant picture of what is happening in gas foil bearings during their operation. The article includes an analysis of foil vibrations. This phenomenon has already been analysed numerically, and this is the first time it has been analysed experimentally. The registered motion of the foils can be compared with the results obtained from numerical models, thus allowing their further development. One such comparison is shown in this article.

The paper discusses a perspective of the usage of various types of smart materials to enhance the operational properties of Gas Foil Bearings. The authors, referring to the current investigation on thermomechanical characteristics of the above-mentioned bearing type, have focused on the concept of using Shape Memory Alloys, Piezoelectric Transducers, Thermoelectric Modules and Thermocouples to improve both mechanical and thermal behavior of the bearings. Based on the available literature and the authors’ experience, the present work provides an overview of the known and perspective applications of smart materials to Gas Foil Bearings. In particular, a discussion on their capabilities, limitations and effectiveness is conducted, taking into account the unique characteristics and requirements of the studied type of bearings.

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.

In order to protect rotors and foil bearings operating at high temperatures from being overheated and damaged, these components are often cooled by air. In addition, such a cooling method is accompanied by an axial temperature gradient that changes the shape of the lubrication gap in a way likely to affect the operation of a foil bearing. This article presents the research on various methods for cooling a foil bearing and discusses the impact of these methods on dynamic parameters of the rotor-bearings system. To be able to assess the temperature inside such a bearing, there is a need for a reliable measurement method. The authors of the article measured the temperature of the top foil using thermocouples and showed that their measurement method does not exert any significant impact on the operation of the rotor-bearings system. The article also describes a novel method for compensating the axial temperature gradient occurring in the bearing bush using Peltier modules.