Analysis and Design of Segmented Dampers for Rotor Dynamic Control

Abstract

Dampers have become of increasing importance in the control of shaft vibration of rotating equipment which must operate through one or more critical speeds. This paper presents the analytical results for the study of a new class of damper, the segmented film damper. A series of isolated segments of fluid are used rather than a continuous film as in the traditional squeeze film damper. This configuration provides energy dissipation through fluid viscosity within the film segments and through oriface flow in the supply and exit ports for each segment. The pressure distribution within an individual segment is developed on the basis of Reynolds equation with appropriate boundary conditions. The effects of various parameters are discussed in terms of this pressure distribution. The geometric effects of multiple segments are derived for both input, how shaft motion excites each segment, and output, how the segments’ pressure distributions combine to provide a net force. The damping force is shown to be linear for a wide range of operating conditions, speed and unbalance, and thus validly expressed in terms of a damping coefficient. Additionally, this class of damper is shown to have no radial stiffness. The limitations and implications for the designer are discussed in detail. A structured design procedure is given for the selection of parameter values, and a design example with numerical values is included.