Study of the Pumping Performance of a Dry Scroll Vacuum Pump

Abstract

The leak flow through clearances between the fixed and orbiting scrolls of a dry scroll vacuum pump is a dominant factor that determines the pumping performance. Because the leak flow sometimes ranges from viscous to slip to free molecule flow along a clearance, the equation that describes the flow through the three flow regimes is developed by a weighted linear combination of the two equations for free molecule and slip flows. The pressure distribution in gas pockets is another important factor in pumping performance. The validity of this theory is examined by experiments.