Experimental Investigation of Whirl in Self-Acting Air-Lubricated Journal Bearings

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Abstract
Bearing characteristics influencing the threshold speed at which large-amplitude self-excited whirl occurs in complete, air-lubricated journal bearings were experimentally investigated. Various combinations of rotors having clearance ratios, Ψ = c/r, ranging from 0.268 × 10−3 to 2.350 × 10−3 and symmetrical bearing assemblies having slenderness ratios, L ′ = L/D, ranging from ¼ to 1 were tested. By varying slenderness and clearance ratios and unit load, by opening or closing supply orifices, or by adding imbalance, the whirl threshold speed could be varied between zero and the limit set by the available power. Experimental methods of identifying the cylindrical and conical modes of synchronous and self-excited whirl are described. The whirl hysteresis region and the nature of whirl at speeds above the threshold are examined. Three methods of avoiding large-amplitude self-excited whirl are discussed.