Mathematical Simulation of Free Molecular Flow in a Three-Dimensional Turbomolecular Pump with Nonparallel Blades

摘要

Turbomolecular pumps are widely used in scientific and industrial applications. The three-dimensional simulation of free molecular flow within a row of blades of a turbomolecular pump is solved using test-particle Monte Carlo method. The solution performed in an inertial reference frame where molecular paths are straight line. The following of molecule paths in both rotor and stator is done in a similar system of coordinates. Good agreement between numerical results and quasi similar previous simulations confirm the validity of the presented algorithm. In this simulation, effects of the flow leakage due to existence of clearance between blade tip wall and casing is considered and the blade thickness is ignored. In addition the flow analysis shows effects of determination of sizes, significant effects of clearance and more importantly the effects of blade's angle on turbo molecular pump's fundamental characteristics. The simulation of turbo molecular pump with the nonparallel blades is done and compared with similar parallel blades.