Flow investigation of Siegbahn vacuum pump by CFD methodology

Abstract

The computational fluid dynamics (CFD) methodology is successfully applied to investigate the flow field of the Siegbahn vacuum pump. The rotor is equipped with 18 helical grooves that are separated by thin blades on both the upper and lower planes. To simplify the computational model and shorten the calculation time, only one single-flow channel including one groove of upper plane and one groove of lower plane is calculated. The full computational domain is linked by five subregions. From the results of simulation, the relative errors of inlet pressure between the measured and predicted are (A) beyond 60%, (B) between 10–15% and (C) below 2% when the flow field contains (A) coupled continuum, slip and transition flows, (B) coupled continuum and slip flows and (C) only continuum flow, respectively. The detailed pressure and velocity fields in the rotor grooves are quite different for various working pressures. The compression ratio of lower groove is less than 1 when the working pressure is larger than 13.3 mbar. That will harm the compression performance of Siegbahn vacuum pump.