Measurement of oil film journal bearing damping coefficients - An extension of the selected orbit technique

This paper describes a novel experimental procedure for measuring the four velocity or damping coefficients of an Oil Film Journal Bearing from imposed dynamic orbits. All four damping coefficients are derived from one imposed journal center dynamic orbit and, therefore, may be regarded as being obtained at the same time. The method requires the production of a ''figure of eight'' shaped orbit and utilizes the ''cross-over'' point therein. Coefficients are initially evaluated in a coordinate system which is chosen to align with the designated parts of the measured orbit. Each coefficient is then separately evaluated from single values of instantaneous imposed force and resulting journal center velocity. Coefficients are then converted into any other desired axes system. All the benefits of the original selected orbit technique are retained. The presented method places much less severe demands on experimental procedure. An available example illustrates the technique. A realistic uncertainty analysis for this example is included. Indications are provided which show how the orbit features may be adjusted to substantially reduce uncertainty.