SPIRAL GROOVED VACUUM PUMP WORKING IN HIGH-PRESSURE RANGES

The pumping performance of spiral grooved vacuum pumps which work in the pressure ranges above 1000 Pa is studied experimentally and theoretically. Experiments are conducted for several rotors with various geometries, and theoretical predictions are made using a Reynolds stress model for turbulent comer flows. The pressure difference between the upstream and downstream sides of a rotor begins rising at a Reynolds number Re based on the hydraulic mean depth m, Re = 4rhoUm/mu(U is the peripheral speed, rho is the density and mu is the viscosity) in the neighborhood of 2000, where the flow in the grooves is considered to become turbulent. The theoretical predictions show relatively good agreement with the experimental results for moderate Reynolds number ranges, but the theoretical curves begin separating from the experimental results as the Reynolds number increases.