| With the development of precision technology,micro fluidic dynamic systems have also risen.As the "engine" of the microfluidic system,the micropump has always been a hot topic of research by domestic and foreign scholars,the application fields involve biomedicine,chemical analysis,electronic cooling,etc.Valveless piezoelectric micropumps rely on the advantages of simple structure,excellent fatigue resistance,and strong resistance to electromagnetic interference,which are of great significance in this field.In this paper,the cone tube structure is combined with the wall jet structure,and the bilateral symmetrical dual-chamber parallel arrangement is adopted,and a double-chamber parallel wall jet valveless piezoelectric micropump with a cone tube is proposed.The effective combination of dual-chamber parallel connection,wall jet structure,and cone tube greatly increases the net flow rate of the micropump,.The following introduces the main research content and findings of this article:Firstly,based on the related theories of micro-scale flow,piezoelectric vibrator,cone tube and Coanda effect.The structure design and working process of the dualchamber parallel wall jet valveless piezoelectric micropump with cone tube are introduced,and the calculation formula for the net flow and volumetric efficiency of the micropump are derived.Experiments and numerical simulations were carried out on the single-chamber wall-attached valveless piezoelectric micropump and the singlechamber cone-tube valveless piezoelectric micropump respectively to verify the accuracy of the numerical simulation.The manufacturing process and test process of the single-chamer cone tube valveless piezoelectric micropump and the single-chamber wall jet valveless piezoelectric micropump are briefly described.The SST turbulence model and dynamic mesh boundary conditions are selected for the numerical simulation settings.The result shows that the error between the test and simulation results of the cone tube micropump and the wall jet micropump are 8.21%and 13.6%,respectively.Through boundary condition analysis,grid independence analysis,cycle and time step independence analysis,the simulation settings of the double-chamber parallel wall jet valveless piezoelectric micropump with cone tube are determined:the velocity boundary conditions are selected to calculate the 1.2 million mesh model For the four cycles of the grid,the time step is set to 1/100f.Using this set of numerical simulation methods,the micropump was preliminarily explored:When f=100Hz and the maximum displacement of the vibrator is greater than 3.07μm,the net flow rate of the dual-cavity parallel micropump is always higher than the other two types of micropumps.Secondly,the influence of driving and structural parameters on the net flow rate of a dual-chamber parallel wall jet valveless piezoelectric micropump is explored.For the driving parameters,the effects of driving phase difference,Reynolds number and driving frequency are considered.The results indicates that:micropump with high net flow at a drive phase difference of 180°;when the Reynolds number is constant,The net export flow of the pump decreases with the increase of the driving frequency;when the driving frequency is constant,the larger the Reynolds number,the higher the net export flow of the micropump.The structural parameters mainly discuss the wall jet angle θ,the cone tube angle α,the converging cone length l1,the shunt tube length l2,the cone tube length l3,and the shunt tube width ratio C1/C2.The variation range of each parameter is:θ=15°～75°,a=0°～45°,l1=0.6～1.6mm,l2=0.5～1.75mm,l3=0.5～6mm,C1/C2=0.3～1.The driving parameters are set to Reynolds number Re=500,driving frequency f=50Hz,phase difference φ=0°.The simulation results show that:as the exception of the manifold length and cone length,the net flow increases and then minishes with increasing values of the other four parameters;as the length of the manifold increases,the net outlet flow of the micropump generally tends to decrease;when the length of the cone tube continues to increase,the net export flow rate of the micropump continues to increase,but the growth rate continues to decrease.Comprehensively obtain the optimal interval of each parameter:θ=40°～60°,α=4°～12°,l1=0.8～1.1mm,l2=0.5～lmm,l3=4～6mm,c1/c2=0.4～0.6.Thirdly,the response surface is optimized according to the optimal interval of each parameter.Firstly,the distance correlation coefficient method is used to select five structural parameters that have obvious effects on the flow rate of the micropump:the wall jet angle θ,the cone tube angle α,the converging cone length l1,the shunt tube length l2 and the cone tube length l3.Use Design Expert software to select the BBD model to plan 46 sets of optimized experimental designs,and obtain the outlet flow value through CFX numerical simulation.Through F test and R2 test,multiple regression equation models are compared,and the quadratic equation regression model is finally selected.From the cross-term contour map and response surface analysis,it is found that the interaction between the wall jet angle θ and the length of the converging cone tube l1 has the greatest impact on the micropump discharge flow.The final determination of the optimal combination of structural parameters is:the wall jet angleθ=49.4°,the cone tube angle α=9.83°,the converging cone length l1=1.07mm,the shunt tube length l2=0.750mm,the cone tube length l3=5.08mm,the maximum net flow rate at the outlet of the micropump can reach 1.652ml/min.Comparing the model with the highest flow rate among the 46 experimental groups with the optimized model,the outlet flow rate was increased by 0.028 ml/min,and the streamline diagrams of the flow field in the initial model and the optimal model were compared,it is found that the optimized structure size is more conducive to the development of the vortex... |
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