Abstract
This paper investigates the transient flow rate performance of small piezoelectric-hydraulic pumps. In a previous study, a small piezoelectric hydraulic pump was designed and developed to be applicable to the braking systems of small- and medium-sized UAVs (unmanned aerial vehicles). To this end, a thin plate spring check valve was designed in order to effectively discharge the flow in a single direction. The flow rate of the piezoelectric-hydraulic pump is an important criterion for evaluating pump efficiency. Therefore, a study on the parameters affecting such a flow rate is necessary to enhance the efficiency of piezoelectric hydraulic pumps used in brake systems. This study on small piezoelectric-hydraulic pumps is performed to accurately predict the flow rate using a CFD (Computational Fluid Dynamics) tool. In other words, an unsteady CFD method is applied to model the transient flow rate characteristics and the internal flow field of the fluid. The visualization of the internal flow field is evaluated for a better understanding of the flow fields inside the pump. Moreover, this work also illustrates the detailed motion of both the inlet and outlet check valves during the pump operation that fully reflects the phase shift between the check valves and the piston motion, all of which affect the flow rate performance of the pump. An experiment of flow rate characteristics was conducted on a designed piezoelectric-hydraulic pump, which verifies the validity of the CFD results.
Highlights
With advantages such as low costs, supply safety, reliability, and structural simplicity, hydraulic systems with power oil pressure have a lot of potential upsides when being applied to aircraft as a mechanical power transmission
With a complex structure that includes many parts such as a pressure accumulator, solenoid valves, a hydraulic reservoir, check valves, and electronic control devices, the hydraulic pump used in aircraft brake systems commonly possesses great size and weight
Because the flow through valve can flow in two directions: entering and exiting the chamber, the outlet and inlet the check valve can flow in two directions: entering and exiting the chamber, the outlet boundary type are assigned as pressure outlet and pressure inlet, which are set up to be at and inlet boundary type are assigned as pressure outlet and pressure inlet, which are set atmospheric pressure, since the concern of this research is the pressure difference
Summary
With advantages such as low costs, supply safety, reliability, and structural simplicity, hydraulic systems with power oil pressure have a lot of potential upsides when being applied to aircraft as a mechanical power transmission. With a complex structure that includes many parts such as a pressure accumulator, solenoid valves, a hydraulic reservoir, check valves, and electronic control devices, the hydraulic pump used in aircraft brake systems commonly possesses great size and weight. This is one of the disadvantages of the conventional hydraulic system used in unmanned aircraft, which have stricter weight and space constraints. The design and fabrication of a small piezo-electric hydraulic pump with a PZT actuator applied to UAV brake systems have been proposed to demonstrate superior performances, i.e., low power consumption, high reliability, and precise pressure control in comparison with its conventional counterparts
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