A Study of Pressure Fluctuations in the Suction Lines of Positive Displacement Pumps

Abstract

This paper is a contribution to the understanding of the generation and transmission of pressure ripples in hydraulic systems. Previous research on fluid-borne pressure fluctuations in hydraulic systems has been largely directed towards high pressure lines. This paper examines the behaviour of the pressure fluctuations in axial piston and gear pump suction lines. It has been found that the unsteady flow taken in by a pump creates a standing wave in the inlet line in much the same way as a delivery line. The magnitudes of the pressure fluctuations are very sensitive to mean inlet pressure, due to changes in inlet flow ripple with mean pressure. No evidence of air release in the inlet line was found and it is concluded that at low inlet pressures air release occurs in the pump inlet passageway, although in microscopic proportions since no reduction in volumetric efficiency was observed. System air-borne noise was found to be very dependent on mean inlet pressure.