Some features of molecular flow in a rotor-stator row with real topology

Free molecular flow within rotor and stator rows of a turbomolecular pump is simulated using test-particle Monte Carlo method. The solution is performed in an inertial reference frame where molecular paths are straight lines. The molecules are followed both in rotor and stator in a similar system of coordinates. The real three-dimensional topology of the blade rows including blade thickness, clearance between blade tip wall and casing, and the gap between rotor and stator are considered. Good agreement between numerical results of several rotor-stator combinations and known experimental data confirms the validity of the presented algorithm. The flow analysis shows that although the molecules tend to collect in high radius region, however the concentration of molecules attenuates in the clearance region of rotor, and accentuates in the clearance region of stator. Parametric study of a rotor-stator row shows that the effect of the gap between rotor and stator is significant for the first stages of TMPs with large blade angles and wide spacings, while it is negligible for the last blade rows with small angles and small spacings. (C) 2003 Elsevier Ltd. All rights reserved.