The Reduction of Gear Pump Pressure Ripple

Abstract

Pressure fluctuations in a hydraulic system may be substantially reduced by cancelling the flow ripple produced by the pump. This paper describes a secondary flow ripple generating mechanism which introduces an equal and opposite flow fluctuation to that generated by the pump. Tests have shown that the mechanism can virtually cancel four harmonics of pressure ripple but success is dependent on an accurate knowledge of the pump flow fluctuation characteristic. This is best determined experimentally. Similar improvements can be achieved using a mechanism in a motor. This has the additional benefit of reducing torque fluctuations. The reduction in gear pump pressure ripple achieved with the mechanism has been shown to reduce overall airborne noise levels from a hydraulic system by as much as 10 dB, although the airborne noise radiated from the pump casing was not affected.