This example shows a typical power unit consisting of a fixed-displacement pump driven by an angular velocity source, a pressure-relief valve, a pressure-reducing valve, and two variable orifices.
The variable orifices simulate fluid consumption in the main system and in the reduced pressure branch. The simulation starts with both variable orifices open, which results in a low output pressure and the maximum flow rate going to the system. The orifice for the main branch starts closing at 0.5 seconds and is closed completely at around 1.5 seconds.
The output pressure builds up until it reaches 75e5 Pa, and is maintained at this level by the pressure-relief valve. The pressure reducing valve in the reduced pressure branch is set to 20e5 Pa. It maintains this pressure at its output as long as the pressure upstream of the valve is higher than this setting.
The plots below show how flow rates vary in the system as the orifices open and close. The fluid exiting the pump is divided between the orifices at the start. As the Orifice 1 and 2 is close, flow gradually ends up being diverted through the pressure relief valve.