Hagstrom, Nathan2022-08-292022-08-292022-05https://hdl.handle.net/11299/241396University of Minnesota Ph.D. dissertation. 2022. Major: Mechanical Engineering. Advisor: Thomas Chase. 1 computer file (PDF); 170 pages.Fluid power is an essential technology that underpins modern societal and industrial infrastructure. The performance of the majority of fluid power systems hinges on proper control valve function. Despite the importance, the core actuator technology used in control valves has remained largely unchanged for decades with incremental improvements made where possible. Now, conventional actuator technology development has reached a point of diminishing returns and provides a barrier to developing higher performance pneumatic systems. Use of smart materials in small displacement actuators, such as piezoelectric stack actuators, in control valves has the potential to break down barriers existing for conventional actuation methods. Piezoelectric stack actuators are useful as they have very low power consumption, nanometer displacement control resolution and microsecond response time. However, piezoelectric stack actuators are often overlooked due to inherent limitations in flow capacity created by their microscale actuator stroke. To enable revolutionary improvement in control valve design, this research answers fundamental questions required to enable widespread implementation of small displacement actuators, such as piezoelectric stacks, in proportional control valves. This research addresses limitations posed by existing pneumatic valve architectures through investigation of the potential for small displacement actuators use in applications where typically a relatively large displacement actuator would be needed. In so doing, this research investigates two methods for increasing flow capacity in valves using actuators with microscale stroke lengths. The first of two methods investigated uses a microfabricated array of micro-orifices to increase peripheral area acting as the governing flow restriction. The investigation involved design and characterization of a normally open axial proportional flow control valve using a piezostack actuator to modulate seal position. Further experimental and numerical study on the limitations posed when using an orifice array to increase flow area was summarily completed to develop an empirical basis for micro-orifice array design. The second of the two methods for increasing flow capacity was studied using experimental, numerical, and analytical methods. This method varied valve seal geometry to increase projected flow area and reduce viscous related flow losses. Results from study of the second method for increasing flow capacity enabled development of an analytical flow rate model to allow for model based valve design. Control valves better able to implement small displacement actuators, such as piezostack actuators, have potential to catalyze advances in numerous industries and applications. Impacted industries include: mobile robotics, medical instrumentation, natural gas handling, industrial control systems, and process control instrumentation. This research establishes a fundamental understanding of flow rate behavior in valves operating at microscale displacements. The valve architectures, empirical relationships, and flow models described provide a platform for future advances in control valve design and performance.enCompressible FlowMicrofabricationOrificeValveThesis or Dissertation