Novel Concepts in Piezohydraulic Pump Design
Keller, Charles Anderson
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Over the past several years, there has been significant development in the field of applications for piezoelectric materials. This thesis focuses on using these materials in a piezohydraulic pump system. Piezopump systems typically operate by pushing fluid through check valves to produce positive fluid flow. The accompanying hydraulic system utilizes a control valve, hydraulic accumulator, and hydraulic actuator. The function of the piezopump is to convert the very small displacements of the piezoelectric stack actuators into useful work. This paper details the design, construction, and testing of four such possible pumping systems. The first system was a thin diaphragm piezo pump which utilized conventional check valves to rectify the flow. This pump was the next generation system in a series of piezopumps designed at Georgia Tech. Its peak performance with a driving voltage of 150V was a flowrate of 140 cc/min with a blocked pressure of 1.38 MPa (200 psi.). The key features of this system were its aluminum construction and ease of assembly. A new technology was developed which used a resonant fluid cavity to build usable pressure for a pumping system. Two half wave resonators were build to operate at frequencies of 20 kHz and 1 kHz. These systems produced good pressure during resonance, but attempts to rectify these high frequency pulses were unsuccessful. Rectification methods such as reed valves, vortex fluid diodes, and nozzle/ diffuser arrangements were discussed. A reed valve system was developed and tested. A fourth piezoelectric system was developed which used the driving elements and the reed valves originally designed for the resonant systems. This non resonant reed valve pump produced good results. This pump systems produced 338cc/min at a frequency of 400 Hz. It also produced a blocked pressure of 250 psi. There are many applications for these miniature high flow pumping systems. The technology in the reed valve pump is scalable, and the size of this particular system may be reduced dramatically to offer even more space saving potential.