Improving the Oil-Free Scroll Vacuum Pump Efficiency

Abstract

Improving the quality of manufactured products involves reducing any contaminants introduced into the vacuum chamber from the pumping means. Scroll vacuum pumps, which are constantly developing, are the most promising for oil-free pumping. Relying on the mathematical model developed, we examined the influence of the main parameters of the scroll on the scroll pump performance, in particular, the influence of the radius of the base circle on the pumping speed and the power consumption of the scroll pump at fixed and variable radii of the pump housing bore. Maintaining the overall dimensions of the pump with an increase in the radius of the base circle proves to lead to an exponential increase in the limiting residual pressure and a decrease in energy efficiency due to a decrease in the number of scroll wraps and, as a consequence, an increase in backflows. For the pump under consideration, when the base circle radius is more than 3.5 mm, the limiting residual pressure exceeds 10 Pa, and the vacuum scroll pump can no longer be a full-fledged oil-free alternative to oil-sealed vacuum pumps. With an increase in the radius of the base circle, while maintaining the number of scroll wraps, the radius of curvature of the outer wraps will increase; this results in the backflow decrease, leading to a decrease, albeit insignificant, in the limiting residual pressure. The energy efficiency of the scroll pump decreases with decreasing pump inlet pressure. The above dependencies make it possible to choose the optimal geometry of the scrolls, based on the specific conditions for which the vacuum scroll pump is designed