ANALYSIS OF 3-DIMENSIONAL SINGLE-STAGE AND 2-DIMENSIONAL MULTISTAGE MODELS OF FLOWS IN TURBOMOLECULAR PUMPS

At high blade speeds, the traditional two-dimensional (2D) infinite bl ade row model of a single turbomolecular pump (TMP) stage becomes inap propriate and a three-dimensional (3D) model should be used. The reaso ns for the improved compression performance predicted in 3D are invest igated by comparing the velocity, angular and spatial probability dist ributions of particles obtained from Monte Carlo simulation. In additi on, that direct multiple stages are better than the extrapolation of s ingle stage results would suggest due to the modification of the angul ar probabilty distribution by adjacent stages. The flow is examined fo r a rotor-stator combination. (C) 1997 Elsevier Science Ltd.