Abstract
The fluid borne noise characteristics of hydraulic pumps and motors are commonly represented in the frequency domain using a source flow ripple spectrum in parallel with a source impedance spectrum. This is equivalent to Norton’s theorem for electrical sources in which the source is represented as a current source in parallel with a resistance or impedance. The validity of this representation is considered for two types of piston pump through simulation and for a third piston pump through experiment. It is shown that the Norton model of source flow ripple and source impedance is a reasonable approximation to the fluid-borne noise characteristics of positive displacement pumps. However for pumps in which fluid compression is a dominant feature in the source flow ripple, such as piston pumps, the source flow ripple varies somewhat with the system pressure ripple, and this causes significant problems with the Two Loads method, resulting in unrealistic source impedance measurements.
