Theoretical study on the pumping mechanism of a dry scroll vacuum pump

The leak flow through clearances between the fixed and orbiting scrolls of a dry scroll vacuum pump is considered to be a dominant factor which determines the pumping performance. Since the leak flow sometimes ranges from viscous to slip to molecule flow along a clearance, the equation which can describe the flow through the three flow regimes was developed by the weighted linear combination of two equations of molecule and slip flow. The pressure distribution in gas pockets is considered to be another important factor for the pumping performance. The predicted ultimate pressures show a reasonable agreement with those of a practical machine. Copyright (C) 1996 Elsevier Science Ltd.