Dynamics Analysis And Experimental Study On Non-rotating And Non-volumetric Type Valveless Piezoelectric-stack Pump

With the development of biologic, medical science, health care, chemical industry, chemical safetymonitoring and aerospace technology, higher requirements are proposed on the micro fluidic deviceintegration and fluid delivery precision. Traditional electromagnetic pumps are increasingly unable tomeet the needs of scientific research and engineering practice due to their structure and workingprinciple. Valveless piezoelectric pump with the characteristic of simple structure, small volume, lightweight, low energy consumption, low noise, no electromagnetic interference emerges as required bythe time. Because of its broad application prospect, since Sweden's E Steme proposed the concept ofvalveless piezoelectric pump in1993, a variety of valveless piezoelectric pumps with new principle,new structure have came into being in large numbers and have become the hot issue of researchworldwide. However, there is still a long way to go before it can meet the actual demands due to theirshortness of reflow phenomenon by nature, the large flow fluctuation, low flow rate, low efficiency,ect.. Supported by the National Natural Science Foundation of China, this paper carried out theexploratory study on valveless piezoelectric pump with original innovation and completelyindependent intellectual property rights based on the current research,. The main research contents areas follows:1. Inspired by the fish-tail swing, caudal-fin imitation type valveless piezoelectric pump withlaminated piezoelectric vibrator are presented, which belongs to neither volume type norrotary type taxonomically. A prototype is fabricated, and researches on flow testing, vibrationexperiment, flow simulation have been conducted. The experimental results show that, withconstruction of flexible caudal-fin in the end of the vibrator and appropriate optimization, theflow rate of the pump was increased by43times in per unit volume of piezoelectric ceramicsheet than that of non flexible caudal-fin; the flow rate was266mL/min under the60V voltage.Compared to the traditional volumetric type of valveless piezoelectric pump, valvelesspiezoelectric pump with laminated piezoelectric vibrator in flexible caudal-fin structure hasadvantages of large flow rate, small flow pulsation, non backflow phenomenon, etc..2. Some researches about influencing factors of pump performance are conducted, such aspiezoelectric vibrator's dielectric in water, piezoelectric vibrator's working space, flexiblecaudal-fin's structure, piezoelectric laminated beam's pattern, thickness ratio between matrixand ceramic sheet and the vibrator 's distance from solid wall. Vibration equation of the vibrator was derived under the external electric field and modal force factors were analyzed.Based on the principle of least action, modal approximation for the mutant cross-sectionlaminated piezoelectric beam was gained by using Rayleigh-Liz law. Through the reasonableselection of permissible function sequence, the approximate solution of modal frequency andthe experimental results are well consistent and the relative error of the second orderresonance frequency is2.1%.3. As result of the PZT electrode layer damage which is easy to happen when the laminatedpiezoelectric vibrator (single chip and double wafer) is immersed in the pump chamber, andthe phenomenon of fluid ionization and fluid heat, a novel piezoelectric stack pump which hasa variable cross-section swinging vibrator imitating caudal fin capable of separation thevibrator from the water has been put forward and designed. Pumping capacity is tested as thevibrator working in pump cavity and in approximate infinite waters (sink), respectively.Under80V voltage, if vibrator works in sink, the first and second order bending modalfrequencies are680Hz and1370Hz respectively. With the backpressure of30mm watercolumn, the maximum flow rate is560mL/min. If vibrator works in pump chamber, the firstand second order bending modal frequencies are617Hz and1356Hz respectively and themaximum flow rate reaches400mL/min. The key structure parameters—flexible tail lengthand arm length, which have important influence on the pump performance, have been studiedin the experiment. The result shows that the resonant frequency changes with flexiblecaudal-fin, whose evolution is consistent with the linear vibration theory. But the amplitude ofthe end part changes with the flexible tail length and arm length tending to increase at first andthen decrease. Pseudo rigid body dynamics model of the swinging vibrator is established,which describes theoretically the weak coupling between vibrator arm and flexible caudal-fin.4. The author explained the working principle of this type of bionic pump, and proposed that theunidirectional flow is mainly originated from centrifugal force from the fluid around thevibrator which does arc swing movement accompanying with the vibrator. From the aspect ofmomentum, interactions between swinging vibrator and fluid particles is analyzed, and theformula of flow rate is deduced.