@article{Łukasz Breńkacz20261,
author = "Łukasz Breńkacz and Paweł Bagiński and Artur Andrearczyk and Małgorzata Bogulicz and Grzegorz Żywica",
abstract = "The tested active gas-foil bearing is representative of high-speed, high-precision rotor supports used in compact turbomachinery and precision spindles. We report diameter-resolved experiments on an active gas-foil bearing, in which the sleeve is set before each run to adjust the radial clearance. Fifteen set points (35.1554–35.5110 mm; 25.4 µm steps) were tested under repeatable transients: 30 s start-up to 24,000 rpm, a short steady segment, and 30 s coast-down. The friction torque (converted to power and energy loss) and journal temperature were measured using calibrated sensors. The results show a clear asymmetry: at comparable speeds, the coast-down torque exceeds the start-up torque. Increasing the sleeve diameter reduces transient losses, with friction-induced power dropping from 310 W (start- up) and 400 W (coast-down) at the smallest setting to 200–250 W at the largest. The maximum friction torque changes little beyond Ds ≈ 35.25–35.30 mm, indicating a practical window for start/stop mitigation. Temper- atures remain moderate (62 to 70 ◦C), while coast-down heating rates are typically two to four times higher than during start-up. By scheduling the clearance through sleeve-diameter adjustment, the bearing systematically reduces start/stop energy dissipation and the associated thermal loads—key factors affecting efficiency, durability, and mainte- nance in oil-free machines. The quantified start-up and coast-down losses, together with the measured tem- perature fields, provide benchmark data for precision rotor design and control.",
doi = "https://doi.org/10.1016/j.measurement.2026.122020",
issn = "0263-2241",
journal = "Measurement",
keywords = "Gas foil bearing;Active bearing;Start-up losses;Coast-down;Friction torque;Precision rotor;Oil-free support",
pages = "122020",
title = "{S}tart-up and coast-down friction and temperature in an active gas foil journal bearing with adjustable sleeve diameter",
url = "http://brenkacz.com/images/publications/Bre%C5%84kacz%20et%20al.%20-%202026%20-%20Measurement%20-%20Start-up%20and%20cast-down%20friction%20and%20temperature%20in%20an%20active%20gas%20foil%20journal%20bearing.pdf",
volume = "282",
year = "2026",
}