This work presents the modelling and testing of a Virtually Variable Displacement Pump (VVDP). The system used a high speed on/off valve to modulate flow from a fixed displacement pump, directing the flow either to the tank or high pressure supply line of the hydraulic system. A lumped parameter model of the system was developed using sub-models to describe the dynamics of each component in the system. A test setup using currently available components was built to validate the overall system model and study the effects of switching frequency on system efficiency. Once verified, the model was used to simulate and further study the effects of changing the compressible fluid volume and line lengths. Simulation results show that reducing the line lengths and compressible volume improves the average VVDP system efficiency by 14 % over a range of switching frequencies and duty cycles while holding other system parameters constant.

Keywords: virtualvariabledisplacementpump,lumpedparametermodel,verification,optimization