Effect of Piston Ring Grooves on the Radial and Tangential Forces of a Squeeze Film Damper

Abstract

Squeeze film dampers (SFDs) are components of rotating machinery used to reduce vibration amplitudes and improve the rotor dynamic stability. Piston rings (PRs) are often employed as end seals for SFDs. They enhance the damping forces while remaining limited to a small axial length. Piston rings are installed in grooves whose dimensions (width and depth) are generally one order of magnitude larger than the radial clearance of the SFD. The radial and axial clearances after the PR are mounted may impact the forces generated by the SFD to the point that they have to be considered as design parameters. Computational fluid dynamics (CFD) and bulk flow (BF) approaches were used to determine the impact of the axial and radial clearances introduced by the presence of the PRs. CFD is an accurate, direct approach to the problem but it requires intensive computational resources. Therefore, BF-based methods are considered as an appropriate option for a wide range of SFD operating conditions. The BF approach developed previously is now extended to include the PR clearances. The results are validated using CFD simulations for a simplified SFD geometry. This comparison underlines the strengths and limits of the BF approach. The impact of the PR clearances on the radial and tangential forces is then evaluated on a realistic SFD by using the BF model. A parametric study is conducted to explore the impact of varying the axial and radial PR clearances. Overall, a procedure for correctly considering PR clearances in a BF framework is proposed and validated, while complementary elements for understanding the role of PR clearances are described.