This paper offers an extensive review of publications dealing with the modeling, the design, and the experimental investigation of grooved dynamic gas-lubricated bearings. Recent years have witnessed a rise in small-scale and high-speed turbomachinery applications. Besides the well-known gas foil bearings, grooved bearings offer attractive advantages, which unveil their potential in particular at small scale due to the structural simplicity as well as satisfying predictability. This paper starts with a general background of the application of gas-lubricated bearings and introduces and compares the different gas bearing topologies. Further, the state-of-the-art modeling of grooved gas-lubricated bearings is introduced, systematically assessing the advantages and inconveniences of two major approaches, i.e., the narrow groove theory (NGT) and direct discretization method. Since the NGT method is an elegant and efficient approach to model the complex effects of periodic grooves, a critical section is dedicated to the NGT. In a second phase, different models to include additional physical phenomena such as real gas lubrication, rarefaction, or turbulence effects are reviewed. The paper concludes with a critical assessment of the state-of-the-art and indicates potential fields of research that would allow to shed more light into the understanding of these bearings, as well as with some thoughts on the integrated design methodologies of gas bearing supported rotors.

This paper presents a study of the heat transfer influence on the centrifugal compressor performance. The compressor studied in this paper is based on the scale-up of a turbocharger compressor equipped with a shroudless impeller. To account for the heat transfer effect, a conjugate heat transfer analysis is performed with computational fluid dynamics techniques. The heat transfer phenomena not only externally but also internally are investigated at the design point. The grids adopted in the study are verified at the baseline, with an excellent agreement found between numerical simulations and measurements. The results provide an insight into the dependence of the heat transfer influences on the heat flux paths. The path of the external heat flux passing through the impeller shaft is found to have a great impact on the compressor performance. The study of internal heat transfer shows that the shroud surface dominates the internal heat transfer effect on the efficiency loss. Furthermore, the heat transfer influence is also investigated on the compressor performance at other operating points. The results imply a positive potential margin for the improvement of compressor efficiency by means of heat transfer control.

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