Analysis on Flow Field of the Valveless Piezoelectric Pump with Two Inlets and One Outlet and a Rotating Unsymmetrical Slopes Element

Typically,liquid pump and liquids mixer are two separate devices.The invention of piezoelectric pump makes it possible to integrate the two devices.Hower,the existing piezoelectric mixing-pumps are larger because the need the space outside the chamber,and another shortcome of them is that they cannot adjust the mixing ratio of two liquids.In this paper,a new piezoelectric pump being capable of integrating mixer and pump is presented,based on the theory of the piezoelectric pump with the unsymmetrical slopes element（USE）.Besides the features of two inlets and one outlet,the piezoelectric pump has a rotatable unsymmetrical slopes element（RUSE）.When the pump works,two fluids flow into the inlet channels respectively.Then the RUSE controls the ratio of the two flows by adjusting the flow resistances of the two inlet channels.The fluids form a net flow due to the USE principle,while they are mixed into a homogeneous solution due to strong turbulence flow field and complex vortices generated by RUSE in the chamber.And then the solution flows through the outlet.Firstly,the theoretical analysis on this pump is performed.Meanwhile,the flow field in the chamber is calculated and simulated.And then,the relationship between the flows of the two channels and the rotating angle of the RUSE is set up and analyzed.Finally,experiment with the proposed pump is carried out to verify the numerical results.A RUSE with 20° slope angle is used in the experiment.Four sets of data are tested with the RUSE at the rotating angles of 0°,6°,11°,and 16°,respectively,corresponding to the numerical models.The experimental results show that the empirical data and the theoretical data share the same trend.The maximum error between the theoretical flow and the experimental flow is 11.14%,and the maximum error between the theoretical flow ratio of the two inlets and the experimental one is 2.5%.The experiment verified the theoretical analysis.The proposed research provides a new idea for integration of micro liquids mixer and micro liquids pump.

Theoretical Analysis and Experimental Verification on Flow Field of Piezoelectric Pump with Unsymmetrical Slopes Element

Regular valveless piezoelectric pumps have rectifying elements outside their chambers to produce net flow. These rectifying elements outside the chamber will increase the overall volume of the pump and prevent its minimization. Valveless piezoelectric pump with unsymmetrical slopes elements（USE）, proposed in this paper, differs from other valveless pumps in that it is easy to be minimized by developing the chamber bottom as such a rectifying element. In this research, the working principle of the proposed pump was analyzed first. Numerical models were thereby established and numerical simulation was conducted to the chamber flow field with the method of time-dependent velocity. The effects of the USEs on the flow field in the chamber were shown clearly in simulation. And the particular feature of flow field in the chamber was discovered. It behaves a complex flow field, in which strong turbulent occurs companying a lot of vortexes in different directions and different sizes. This feature is just opposite to what regular piezoelectric pumps expect： a moderate flow field. The turbulent flow could be used to have different liquids stirred and well mixed in the chamber to produce homogeneous solution, emulsion or turbid liquid. Meanwhile, numerical simulation also presents the effect of the angles difference of the two slopes upon the flow field, and upon the flow rate of the pump, which fits to the theoretical analysis. Experiments with the proposed pump were also conducted to verify the numerical results. In these experiments, six USEs with different slope angles were used for efficiency tests, which proved the validity and reliability of the numerical analysis. The data obtained from numerical analysis agree well with that from the experiments. The errors ranged from 4.4% to 14.8% with their weighted average error being 9.7%.

Theory and experimental verification of valveless piezoelectric pump with rotatable unsymmetrical slopes

A valveless piezoelectric pump with rotatable unsymmetrical slopes is developed in this research.It has the following features:The pump integrates driving and transporting,and it can mix different fluids while transporting them.In this paper,firstly,the design of the valveless piezoelectric pump with rotatable unsymmetrical slopes was proposed,and the single-direction flow principle was explained.Then,the fluid mechanics model of the valveless piezoelectric pump with rotatable unsymmetrical slopes was established.Meanwhile,the numerical simulation of the pump was performed.Finally,the experiments on relationship between the rotation angles of the slope and the flow rates were conducted.The experimental results showed that the maximum flow was 32.32 mL min 1.The maximum relative error between the theoretical results and the experimental ones was 14.59%.For the relationship between rotation angles and flow ratio of two inlets,the relative error between the experimental and theoretical maxima was 3.75%.Thus,the experiments proved the feasibility of the pump design and verified the theory.

非对称坡面腔底无阀压电泵流场分析

无阀压电泵需要外接用于产生单向流动流管,阻碍了压电泵的微小型化,针对这一缺点提出了非对称坡面腔底无阀压电泵,该压电泵将用于产生单向流动的部件——非对称坡面集成于泵腔的底部。对非对称坡面腔底无阀压电泵进行了计算机建模,基于商用Fluent12软件运用自定义函数(user defined functions,简称UDF)对压电振子运动形式进行了模拟;采用RNGκ-ε湍流模型对瞬态N-S方程进行了求解,分析了泵腔内流场;得出了从20°到70°不同坡面角度下的平均流量,在坡面角为20°时,可以得到最大平均流量为0.864 ml/min,并通过流量测量试验测得该泵的最大流量达到了8.6 ml/min。从仿真和试验的角度验证了该泵的可行性。

3D打印的锥管坡面腔底无阀压电泵

为提高无阀压电泵的流量特性和解决泵加工工艺性差的问题,研制出了锥形流管坡面腔底无阀泵。首先,提出并设计了锥形流管坡面腔底无阀泵,分析了该泵的工作原理;然后,利用ansys软件对泵腔内流场做了模拟分析,分析结果表明该泵具有传输流体的能力;最后,利用3D打印技术制作了锥形流管坡面腔底无阀泵,并对泵的频率-流量特性进行了试验,驱动频率为8Hz时,锥形流管坡面腔底无阀泵的流量达到最大值26.8ml/min,比相同尺寸坡面腔底无阀压电泵在相同驱动电压条件下输出的最大流量增加了18.6%。试验结果表明,锥形流管坡面腔底无阀泵的流量特性优于坡面腔底无阀压电泵,且采用3D打印技术制作压电泵,提高了泵加工的工艺性,缩短了加工周期,降低了加工成本。

锥管坡面腔底无阀压电泵流场分析

针对坡面腔底无阀压电泵流量小的问题,提出并研制了一种锥管坡面腔底无阀压电泵,即将锥管与坡面腔底组合式新结构作为其无移动部件阀。首先,提出了锥管坡面腔底无阀压电泵结构并分析其工作原理,对泵流量进行理论分析;同时,运用Fluent软件的动网格功能对其内部流场模拟分析。仿真结果表明,该泵具有单向流动特性,在泵腔内部产生漩涡利于液体的混合搅拌。最后,加工制作了锥管坡面腔底无阀压电泵样机,并对该泵进行了流量试验。试验结果表明,驱动电压峰值为250V,频率为5 Hz时,最大流量为25.9mL/min,证明了锥管坡面腔底无阀压电泵的有效性。