Design And Experimental Study On A Valveless Piezoelectric Pump With Double-channel Composite Tubes

As a representative of endogenous driving devices,the piezoelectric pump has significant advantages,such as simple structure,small size,no electromagnetic interference,low mechanical losses,and low operating noise,compared to traditional pumps with an exogenous drive.Therefore,it can be used in micro and nano applications,such as micro-cooling systems,chip labs,and medical micro injections,where the boundary and initial conditions are small in volume and area.Piezoelectric pumps can be divided into valve-based piezoelectric pumps and valveless piezoelectric pumps,according to whether there are moving parts to vary the flow resistance in the flow channel.Valve-based piezoelectric pumps have a complex structure and are often difficult to assemble due to the presence of moving parts during the process of miniaturization.On the contrary,the valveless piezoelectric pumps do not have moving parts,so their structure is simple and compact.They have more advantages of miniaturization and have thus received extensive research attention.Once the structures and the sizes of the components of the valveless piezoelectric pump,the resonance frequencies of the pump can be determined.Because of the poor cutoff and low efficiency of the valveless piezoelectric pumps,they often operate at the first-order resonance frequency where the volume change is greatest and only one first-order resonance flow rate peak exists.However,in many recent studies on new structural valveless piezoelectric pumps,their experimental data all reflect the phenomenon that a flow peak exists in the non-resonance frequency range near the first-order resonance flow rate peak.In this paper,we define this phenomenon as the pseudo-resonance phenomenon.By applying the pseudo-resonance phenomenon,another flow rate peak can be obtained in the non-resonance frequency range without changing the mechanical structure.This is significant for promoting the application of valveless piezoelectric pumps on micro-electro-mechanical systems,where mechanical structures and size parameters are difficult to adjust.Although the pseudo-resonance phenomenon can be clearly observed in the experimental data of the above studies,the pseudoresonance phenomenon has not attracted the attention of these researchers,and its mechanism has not been systematically studied.Therefore,a valveless piezoelectric pump with double-channel composite tubes(VPDCT)was designed in this paper.When the output performance of this pump was studied,it was found that the VPDCT reproduced the pseudo-resonance phenomenon.Then,based on the VPDCT,the pseudo-resonance phenomenon was studied.The causes of the pseudo-resonance phenomenon were analyzed theoretically,and experiments were designed to verify its correctness.The specific research contents are as follows:(1)According to the operating principle of the valveless piezoelectric pump,the structural design of the VPDCT was carried out from the two parts(the piezoelectric vibrator and the pump body),and the structural dimensional parameters of each part were determined.(2)The forward and reverse energy loss coefficients of the double-channel composite pipe were analyzed,and the flow rate equation,the pumping direction of the VPDCT was derived.A flow rate experimental platform was built and a prototype was made to verify the correctness of the theoretical derivation.Meanwhile,the relationship between the operating frequency of the VPDCT and the output flow rate was studied,and the relationship curve between the two was obtained.It was found that there were two flow rate peaks in the frequency range of 0-140 Hz on the frequency-flow rate curve.(3)In order to study the causes of the two flow peaks,experiments were designed to test the vibration modes of the piezoelectric vibrator.The experimental results showed that the vibration modes of the piezoelectric vibrator are both B00 modes in the frequency ranges of the two flow rate peaks.Combining the analysis with vibration theory,it was found that the first flow rate peak was in the first-order resonance frequency range and the second flow rate peak was in the non-resonance frequency range.Therefore,VPDCT reproduced the pseudoresonance phenomenon in the literature.(4)The causes of the pseudo-resonance phenomenon were analyzed theoretically.First,based on the flow of fluid in the tube,it was inferred that water hammer occurred during the merging process.Then,by analyzing the energy conversion during water hammer,the reason for further displacement of the piezoelectric vibrator and for the pump effect of the VPDCT in the pseudo-resonance frequency range were obtained.Finally,flow field observation experiments and frequency sweeping experiments were designed to verify the correctness of the theoretical analysis.