THE DYNAMIC NATURE OF ROTOR THERMAL BENDING DUE TO UNSTEADY LUBRICANTSHEARING WITHIN A BEARING

The influence upon the temperature distribution within a hydrodynamica lly lubricated journal bearing of a time varying journal orbit is cons idered and the oscillatory source distribution arising as a result of unsteady shearing of the lubricant is examined with respect to axes wh ich rotate with the journal, The time dependent thermal bend induced i n a rotor by such a process has been evaluated and incorporated into a rotor dynamic model for the assessment of system stability. Technique s have been developed enabling calculations to be carried out on an id ealized rotor-bearing configuration and the speed range over which ins tability occurred was established. The rate of growth of the unstable vibrations together with the rate and direction of 'spiralling' of the thermal bend vector were also determined. Features of rotor and beari ng design having an influence on such thermally induced instability ar e assessed.