AVS 45th International Symposium
    Vacuum Technology Division Tuesday Sessions
       Session VT-TuM

Paper VT-TuM10
Power Dissipation in Turbomoleculars Pumps at High Pressure

Tuesday, November 3, 1998, 11:20 am, Room 329

Session: Molecular Drag Pumping
Presenter: R. Cerruti, Varian VPT, Italy
Authors: R. Cerruti, Varian VPT, Italy
M. Spagnol, Varian VPT, Italy
J.C. Helmer, Varian VPT, Italy
Correspondent: Click to Email
The operating range of Turbopumps is being extended to higher pressures as a consequence of many demanding applications. Varian VPT has specialized in the design of Gaede stages for extending the operating pressure of the pump. In this paper, another important design aspect of a Gaede stage is identified and analyzed: the power consumption in viscous flow conditions Starting form the analysis of the pressure distribution into a single Gaede stage, already presented in a previous paper, a transitional power consumption model is derived. The model allows to predict the power consumption of a single Gaede stage as a function of the pumping channel dimensions and clearances, the rotational speed, the nature of the gas pumped and the operating pressure. The model is based on three main assumptions: 1. the pressure distribution along the channel satisfy a diffusion viscous model at zero net gas flow 2. the gas flow boundary layer across channel is derived from a simple viscous model 3. the gas viscosity obeys a transition expression valid for the pumping channel geometry Results are compared with the experimental data provided by different single Gaede stages, with different dimensions, at different speed and operating pressure. The behavior of the model with different pump stage clearances is analysed and results are compared with the experimental evidence. A useful use of the model is in the optimization of the design of multistage Gaede pumps.