Whirl Stability of Herringbone-Grooved Gas-Lubricated Journal Bearing

A herringbone-grooved gas-lubricated journal bearing can rotate silently at high speed with low friction, and moreover it can be small-sized. In this paper, the equation of motion of a herringbone-grooved gas-lubricated journal bearing is derived using the gas force which can be obtained by applying the Navier-Stokes equation to the grooved and the ridged parts of a journal. The stability analysis is performed by using the analysis method by Routh-Hurwitz, the root locus of complex eigenvalue analysis, and the transient time history response analysis. The physical meanings of the stability charts which have not been explained sufficiently in the conventional studies are clarified by considering the forward whirling motion and the backward whirling motion, and the more reasonable stability charts are proposed. In addition, it is reported that the present analysis results show a good agreement with the already reported experimental results. Furthermore, the parametric studies as for the specification of gas-lubricated bearing are performed, and it is shown that the stability charts are affected by the change of specifications intricately.