Date of Award


Degree Type


Degree Name

Master of Science in Agricultural and Biological Engineering


Agricultural and Biological Engineering

Committee Chair

John Lumkes

Committee Member 1

Andrea Vacca

Committee Member 2

Robert Stwalley


State of the art variable displacement pumps experience a reduction in efficiency when operating at low displacements. Digital pumps using high speed on/off valves to control fluid entering and leaving the displacement chamber can increase efficiency by eliminating the leakage and friction associated with the port plate and swash plate. Because the displacement chamber is only pressurized during a portion of the piston stroke, leakages scale with displacement which increases efficiency of these units. The largest increase in efficiency comes at low displacements creating a more efficient pump across the entire operating range. Partial displacement can be achieved using four different operating strategies: partial flow-diverting, partial flow-limiting, sequential flow-diverting and sequential flow-limiting. This work investigates the modeling, simulation, and design of a digital radial piston unit that utilizes the partial flow-diverting operating strategy. In previous work, a digital inline piston pump prototype was created to prove the capability of the operating strategies and expected performance. This prototype was modeled and simulation and results were compared to experimental results in order to validate the modeling techniques. The same modeling techniques were applied to model a radial piston pump. Before creating the physics based model for a radial piston pump, a design concept was developed to utilize the most likely implementation. The parameters of this model that directly influence pump performance were investigated and the optimal parameter settings were determined to maximize possible efficiency. The simulation results show a potential maximum efficiency of 92.8% and an efficiency curve that remains above 80% efficient when operating as low as 30% displacement.