Cronk, Paul2024-03-292024-03-292023https://hdl.handle.net/11299/262005University of Minnesota Ph.D. dissertation.--- 2023. Major: Mechanical Engineering. Advisor: James Van de Ven. 1 computer file (PDF); xiii, 187 pages.Hydraulic power transmission is preferred in many industries where power density, ruggedness, and reliability in challenging environments are important characteristics. Two major deficiencies of hydraulic power are energy efficiency and energy storage density. Several avenues for rectifying the low energy storage density of hydraulic systems have attracted research interest.One such avenue is the application of kinetic energy storage, or flywheels, to hydraulic systems, and another is a specific and unique instance of the flywheel known as the Hydraulic Flywheel Accumulator (HFA).This study reviews the current research into the application of kinetic energy storage to hydraulic systems. It then explores various mobile hydraulic flywheel topologies and their control strategies when applied to a hydraulic hybrid truck. To understand and model the HFA this study presents an experimental analysis of power loss in the viscous spin-up of hydraulic fluid in a HFA, in a form useful for HFA design optimization. Then this loss is included in a much broader HFA model to optimize the design of the HFA for vehicle-scale and laboratory applications. Finally, this study presents the results of the construction of the optimized laboratory-scale HFA design and its use in a hydraulic circuit simulating a mobile hydraulic drivetrain. The contributions of this work include the direct comparison of two different hydraulic system topologies previously proposed in the literature, analysis revealing the positive effect on efficiency of allowing increased hydraulic system pressure ranges, an empirical approximation of viscous spin-up loss appropriate for optimization, the development of a detailed model of the HFA, and the first construction and testing of an HFA prototype. This study confirms the presented HFA model through the construction and implementation of this prototype and demonstrates the feasibility of the HFA concept, taking it from a concept on paper to a device, operating at industry standard pressures and application-realistic flywheel speeds, and increasing the boundary of knowledge not only of the HFA, but of the implications of flywheel energy storage for hydraulic systems in general.enAccumulatorFlywheelHybrid Energy StorageHydraulicHydraulic Energy StorageHydraulic Flywheel AccumulatorThesis or Dissertation