Nonlinear Analysis of Squeeze Film Damper with Entrained Air in Rotordynamic Systems

Squeeze film dampers are widely used in aircraft engines, land-based gas turbines, and other rotating machines to improve system damping. They often have entrained air within the oil film, which is usually not taken into account in rotordynamics analysis due to lack of good formulations of the effec...

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Bibliographic Details
Published in:Tribology transactions 2011-01, Vol.54 (1), p.132-144
Main Authors: YOUNAN, AMIR A., CAO, JIANMING, DIMOND, TIMOTHY W., ALLAIRE, PAUL E.
Format: Article
Language:English
Subjects:
Air Bubbles
Air flow
Applied sciences
Dampers
Damping
Density
Drives
Entrainment
Exact sciences and technology
Friction, wear, lubrication
Lubricants
Lubricants & lubrication
Machine components
Mechanical engineering. Machine design
Nonlinear Analysis
Nonlinearity
Oil films
Pressure
Reynolds equation
Rotordynamics
Shafts, couplings, clutches, brakes
Squeeze Film Damper
Squeeze films
Transient Response
Tribology
Viscosity
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Summary:Squeeze film dampers are widely used in aircraft engines, land-based gas turbines, and other rotating machines to improve system damping. They often have entrained air within the oil film, which is usually not taken into account in rotordynamics analysis due to lack of good formulations of the effects involved. The effects on the damping force calculation can be significant. This work presents a new formulation of the nonlinear Reynolds equation pressure evaluation within the squeeze film damper, including the effects of entrained air, with resulting changes in effective lubricant density and viscosity. Viscosity and density expressions are developed as a function of the air/oil volume fraction. The density of the bubbly oil is a function of the air bubble diameter, which changes due to surface tension effects during lubricant motion in the bubbly oil film. The lubricant viscosity decreases due to the entrained volume of air but increases due to the surface tension effects taken from experimental tests. Pressure supply and bubbly oil film cavitation effects are included in the analysis and end seal effects are evaluated. The nonlinear time-transient forces in the squeeze film damper are evaluated as functions of (1) lubricant and air properties; (2) damper geometry including diameter, length, clearance; (3) end seal properties; and (4) shaft position and velocity. Example cases of pressure calculations and radial and tangential forces are shown. Example nonlinear transient motions are presented for a rigid, symmetrical rotor and for a nonsymmetrical rotor representing a gas turbine-type fan rotor.
ISSN:1040-2004
1547-397X
DOI:10.1080/10402004.2010.529543