Gas film vibration inside dry gas seal gap

Abstract

This paper provides a numerical technique to determine the dynamic characteristics of a gas film inside a dry gas seal gap based on steady-state and transient CFD calculations. Two dry gas seals with spiral grooves were studied. Steady-state calculation results were compared with the experimental data. The transient dry gas seal model was created to obtain the dynamic characteristics of a gas film. This model is able to take into account the mutual influence of stator and rotor rings on a gas film. This is made by adding the mesh deformation within very small range (from 2 to 10 microns) along with adding for the mesh the ability to move freely within a big range (up to 500 microns). FSI simulation was added to solve Reynolds- averaged Navier-Stokes equations and dynamic equations of rigid body motion together. Using steady-state and transient gas film models, dynamic and static opening forces were obtained for the different gap values. Gas film stiffness was calculated. In order to determine the oscillation frequency of a gas film, Fourier transform was applied.