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Flow Pulsations in Fluid Power Machines
a Measurement and Simulation Study
Liselott Ericson
Stricter requirements for better working environment involve noise and vibration control of
hydraulic machines. The operational conditions for hydraulic machines, such as pressure and
rotational speed, are also increasing and this makes it even more difficult to develop a quiet,
vibration-free machine due to the interdependence between noise and escalating operational
conditions.
The thesis investigates machines working in different driving modes and under different
operational conditions. A so-called cross-angle is proposed for motor as well as pump/motor
applications with variable displacement angles. The cross-angle is intended to reduce the
overall noise level in the machine's working area. Other noise reduction features are also
considered for machines working in different modes.
To facilitate the system integrator's ability to design quiet systems, methods to determine the
source flow and source impedance of the machine are essential. The source flow is assumed
to be created at the valve plate and the internal impedance related to the high pressure port are
completely independent of the rest of the system. Knowledge of these properties makes it
possible to foresee the noise properties of a system already on the design phase. A novel
source flow measurement method, the source admittance method, is investigated here. The
method is considered to be robust and easy to use to suit industry requirements.