Flow fluctuation abatement of high-order elliptical gear pump by external noncircular gear drive

Large flow ripples restrict the development and application of high-order elliptical gear pumps badly. A new approach is proposed to reduce the flow fluctuations effectively by using a varying angular speed drive. Firstly the instantaneous flow rate model of the elliptical gear pump is established to analyze the effect of the eccentric ratio, number of order and module of the rotors on the flow rate. Then on the basis of the flow characteristics of the pump, an external noncircular gear drive is presented to cancel the low-frequency and large-amplitude flow ripples given by noncircular rotors completely, whose pitch curves are identified to be closed by the residue theorem. Finally, a pump prototype is made to prove that the flow pulsation of the elliptical gear pump can be reduced effectively by the external noncircular gear drive, which provides a favorable support for the design of high-performance pump with lager displacement and uniform flow.