Flow fluctuation abatement method and flow characteristics of lobe pump by external noncircular gear drive

A new flow fluctuation abatement method based on noncircular gear variable speed drive is proposed and the mechanism principle of variable speed lobe pump is expounded. Considering the instantaneous flow rate of lobe pump and the closed constraint condition of noncircular gear, the design method of noncircular gear for flow pulsation suppression based on Fourier series is established. Based on the transient numerical simulation, the effects of design parameter of the noncircular gear, angular deviation, rotor-rotor gap and input velocity on fluid pulsation were investigated. The result shows that the outlet flow rate fluctuation of lobe pump decreases by 84.1 % after installing a Fourier noncircular gear, while the increase of angular deviation deteriorates the flow characteristics. With the increase of the number of terms in the Fourier series, the intensity of the fluid pulsation decreases gradually. Decreasing of the rotor-rotor gap from 0.4 mm down to 0.2 mm produces about 54.1 % reduction of flow rate fluctuation. As the input velocity is increased from 200 (r/min) to 600 (r/min), the flow pulsation is reduced by more than 60.0 %. A pump prototype was made to verify that the flow pulsation of the lobe pump can be optimized effectively by the external Fourier noncircular gears drive, which provides a beneficial support for the design of lobe pump with low flow pulsation.