AVS 50th International Symposium
    Vacuum Technology Thursday Sessions
       Session VT-ThA

Paper VT-ThA7
CFD Analysis of a 2D Model of a Gaede Drag Pump in Viscous and Slip Flow Regime

Thursday, November 6, 2003, 4:00 pm, Room 323

Session: Industrial Vacuum Applications
Presenter: S. Giors, Varian Vacuum Technology, Italy
Authors: S. Giors, Varian Vacuum Technology, Italy
F. Subba, Politecnico di Torino, Italy
Correspondent: Click to Email
Experimental analysis on a uniform and a tapered Gaede pumps were already performed in Varian in 2002 and the results presented at AVS 49th Intl. Symposium.@footnote 1@ The experimental results assessed both compression and pumping speed performances of those pumps and showed some weaknesses of the Couette-Poiseuille 1D model, developed a few years ago by Helmer and Levi to describe the Gaede stage behaviour and to be used as a design tool.@footnote 2@ A 2D model of the Gaede pump, based on Navier Stokes equations, is now developed and validated against experimental results. A commercial CFD code is used to simulate the pumping performance of a single stage Gaede pump (the uniform one in the experiment) in the viscous regime, for different operating conditions, with and without throughput, in order to assess both compression and pumping speed performances, as well as to improve the general understanding of the physics of Gaede pumps within the limitations of a 2D model. The possibility of extending the Navier Stokes model at low pressure, through slip flow boundary conditions is also explored, and the lower pressure limit found for the resulting model by comparison of the numerical results with the experiment. Validation against experimental results has shown some weakness of the pure 2D model, and ideas to include some 3D effects (e.g. the radial leak path) into the 2D model are proposed for future developments. @FootnoteText@@footnote 1@ S. Giors, R. Gotta, J.C. Helmer, "Experimental analysis of Tapered Gaede pumps", AVS 49th Intl. Symposium oral presentation, Denver CO, November 2002.@footnote 2@ J. C. Helmer, G. Levi, "Transition gas flow in drag pumps and capillary leaks", J. Vac. Sci. Technol. A 13(5), 2592-2599, Sep/Oct 1995.