Design And Structure Optimization Of Valveless Piezoelectric Pump With Double Closed Loop Flow Tube

Piezoelectric actuated pumps,utilizing the inverse piezoelectric effect of piezoelectric materials and transferring the electrical energy into mechanical energy to transport fluid,has become a precise fluid transport tool in the field of microfluids with simple structure,no electromagnetic interference,timely response and high displacement resolution.They can be classified into two categories: valveless piezoelectric pumps with designed asymmetric pump chamber(VPPDAPC)and valveless piezoelectric pumps with designed resistance-difference tube(VPPDRET).The former mainly focus on the shape design of bluff body,which has a certain bottleneck in output performance and is reported to be only applied to fluid mixing.The latter can satisfy the demand of microfluid to achieve specific functions,such as separation and screening of material molecules,fluid circulation and so on,through designing different structures of tubes.However,the traditional resistance-difference tubes have a common characteristic that the fluid in different directions flows in the same channel,which results in low energy conversion efficiency for the generally unobvious resistance difference.In addition,the change of resistance in one direction of the fluid diode will bring the changing resistance in another direction,which greatly the freedom of application and hinders the process of modern micro pumps towards multi-function and integration.In this paper,referring to the rectifier diode in electrotechnics,a fluid component with the function of half-wave rectification is put forwards to realize the forward and reserve fluid flow through different flow path without extra loss of kinetic energy caused by backflow collisions,thus improving pumping efficiency.Due to the rectification effect,the proposed fluid component can achieve a single change in flow resistance in one direction without affecting flow resistance in the other direction.The research is carried out from four aspects: structural design,theoretical analysis and simulation,experimental verification and structural optimization design:1.Based on the inertia of fluid and energy dissipation of vortex,a double-loop tube structure with rectification effect was designed to realize the fluid in different directions to flow along different channels;Then,according to the fluid dynamics theories,such as theories of fluid jet and fluid internal friction,the flow resistance of double-loop tube was analyzed.In addition,the rectification effect was verified by finite element simulation.2.Working mechanism of valveless piezoelectric pump was analyzed,including material selection and structural design of piezoelectric vibrator based on the principle and mechanism of piezoelectric material and vibration model analysis,as well as the action mechanism of pumping unidirectionally.By taking double-loop tubes as valve bodies,structure of valveless piezoelectric pump with double-loop tubes was designed and working principle of its rectification effect was also explained.Finally,surface kinetic energy of piezoelectric vibrator and energy conversion process of pump system were analyzed.And the formulas of output performance of pump system were derived,combining with the flow resistance of double-loop tube.3.Sample pumps were fabricated through 3D printing technology and series of experiments such as amplitudes flow rate and pressure were carried out.Then fluid tracer particles and high speed camera were used to observe the flow characteristics in double-loop tube as well as dynamic flow field of tube in pumping cycle.Both pump effect and rectification effect were demonstrated and performances were obtained.4.Influence of cross-section shape,size parameters of tubes and structure of double-loop tube on rectification effect and pump effect of valveless piezoelectric pump with double-loop tubes were explored.Variation of pump output performance with different variable parameters is obtained and the corresponding influence mechanism between causal variables were discussed,which achieved further optimization design.