The Stability Limits of a Flexible Rotor Supported by Journal Bearings with Pressure Difference between Both Ends : 1st Report, Theoretical Analysis-Part 1

Abstract

The stability limits for a linearized model of a symmetric horizontal flexible rotor rotating in cylindrical journal bearings with axial flow in the clearance induced by a pressure difference between both ends are studied theoretically. In this report, the effect of pressure difference between both ends of journal bearings on the stability threshold speed (onset speed of half speed whirl) is investigated. In the present analysis, the dynamic Reynolds equation is applied to the system, and numerically solved with the pressure drop mainly due to the axial acceleration of the oil at the inlet end of the journal bearing being taken into account. The stability threshold speed is obtained by linearizing the equation of motion about the equilibrium and applying the Bairstow-Hitchcock method to solve the characteristic equation. It is found that pressure difference influences the stability threshold speed, which increases with pressure difference except in the range of low pressure difference.