Three-dimensional flow field simulation of steady flow in the serrated diffusers and nozzles of valveless micro-pumps

This paper presents a three-dimensional flow field simulation of the steady flows through diffusers and nozzles with straight or serrated-sided walls to analyze the effect of the channel structure on the flow characteristics.The pressure and velocity profiles in the diffusers and the nozzles as well as the net volumetric flow rate are determined.Our simulation demonstrates that the pressure and velocity profiles in the serrated diffuser/nozzles are more complicated than those with the straight-sided wall,while the net steady flow rate with the straight-sided wall increases monotonically with the increase of the pressure difference,the steady flow rate with serrated sided walls increases gradually to reach a maximum and then decreases with the increase of the pressure difference.The results suggest that the number of the sawteeth plays a significant role in optimizing the design of serrated diffusers and nozzles for improving the transport efficiency of valveless micro-pumps.

无阀纳米泵中水流的反常堵塞

对于颗粒物质,在锥形通道的窄口处容易发生堵塞现象,实验中通常利用机械振动进行疏通.而对于无孔不入的水却不同,即使在纳米尺度的碳纳米管中仍然可以快速通透.本文利用分子动力学模拟研究了由锥形碳纳米管与石墨烯平面构成的无阀纳米泵,发现水输运在一定条件下也会出现反常堵塞.与颗粒物质截然不同的是振动方法无法恢复水流,相反,它促使水在纳米水泵的通道窄口处发生堵塞.通过分析堵塞区水的密度分布、氢键寿命、水分子的结构特征,揭示了反常堵塞是由腔体中振动膜的高频振动引发水的结构相变造成的.

箭头型阻流体无阀压电泵的设计与试验

针对三棱柱阻流体无阀压电泵输出流量小的问题,基于箭头结构流阻小的特点设计了一种箭头型阻流体无阀压电泵,介绍了该泵的结构及工作原理。利用有限元软件模拟仿真了箭头型阻流体无阀压电泵的泵腔速度流线图,并将该泵与三棱柱阻流体无阀压电泵的阻力特性进行了对比分析。结果表明,箭头型阻流体无阀压电泵能单向运输流体,且其效率较三棱柱阻流体无阀压电泵提升了19.51%。利用3D打印机制作了2种泵的样机,进行了流量和压差试验。试验结果表明,在300 V的驱动电压下,箭头型阻流体无阀压电泵的最大流量和压差分别为17.40 g/min和470 Pa,较三棱柱阻流体无阀压电泵分别提升了22.71%和37.03%。

锥形阶梯流管无阀压电泵仿真及实验

针对锥形流管无阀压电泵输出流量小、回流流量多等问题,结合锥形流管和溢流坝阶梯式结构的阻流作用,研制了一种锥形阶梯流管无阀压电泵。对锥形阶梯流管的流阻特性进行了理论分析,利用有限元软件对锥形阶梯流管无阀压电泵和锥形无阶梯无阀压电泵进行了流场仿真对比,制作了锥形阶梯流管无阀压电泵实验样机,测量不同频率和驱动电压下两种泵的流量。实验结果表明:当驱动电压峰峰值为180 V、驱动频率为18 Hz时,锥形无阶梯流管无阀压电泵流量最大为6.20 ml/min,锥形阶梯流管无阀压电泵输出流量最大为8.04 ml/min,与锥形无阶梯流管无阀压电泵相比泵最大输出流量提升了29%,验证了锥形阶梯流管无阀压电泵能有效抑制锥形流管中的回流现象,且相比于无阶梯流管无阀压电泵具有更好的输出流量。

Advances in Valveless Piezoelectric Pump with Cone-shaped Tubes

This paper reviews the development of valve- less piezoelectric pump with cone-shaped tube chrono- logically, which have widely potential application in biomedicine and micro-electro-mechanical systems because of its novel principles and deduces the research direction in the future. Firstly, the history of valveless piezoelectric pumps with cone-shaped tubes is reviewed and these pumps are classified into the following types： single pump with solid structure or plane structure, and combined pump with parallel structure or series structure. Furthermore, the function of each type of cone-shaped tubes and pump structures are analyzed, and new direc- tions of potential expansion of valveless piezoelectric pumps with cone-shaped tubes are summarized and deduced. The historical argument, which is provided by the literatures, that for a valveless piezoelectric pump with cone-shaped tubes, cone angle determines the flow resistance and the flow resistance determines the flow direction. The argument is discussed in the reviewed pumps one by one, and proved to be convincing. Finally, it is deduced that bionics is pivotal in the development of valveless piezoelectric pump with cone-shaped tubes fromthe perspective of evolution of biological structure. This paper summarizes the current valveless piezoelectric pumps with cone-shaped tubes and points out the future development, which may provide guidance for the research of piezoelectric actuators.

Theory and Experimental Verification on Valveless Piezoelectric Pump with Multistage Y-shape Treelike Bifurcate Tubes

Among most traditional piezo water cooling systems, piezoelectric valve pumps are adopted as their driving sources. The valves in these pumps induce problems of shock and vibration and also make their structure complicated, which is uneasy to minimize and reduce their reliability and applicability of the whole system. In order to avoid these problems caused by valve structure, a novel valveless piezoelectric pump is developed, which integrates both functions of transforming and cooling. The pump’s Y-shape tree-like construction not only increases the efficiency of cooling but also the system reliability and applicability. Firstly, a multistage Y-shape treelike bifurcate tube is proposed, then a valveless piezoelectric pump with multistage Y-shape treelike bifurcate tubes is designed and its working principle is analyzed. Then, the theoretical analysis of flow resistance characteristics and the flow rate of the valveless piezoelectric pump are performed. Meanwhile, commercial software CFX is employed to perform the numerical simulation for the pump. Finally, this valveless piezoelectric pump is fabricated, the relationship between the flow rates and driving frequency, as well as the relationship between the back pressure and the driving frequency are experimentally investigated. The experimental results show that the maximum flow rate is 35.6 mL/min under 100 V peak-to-peak voltage (10.3 Hz) power supply, and the maximum back pressure is 55 mm H2O under 100 V (9 Hz) power supply, which validates the feasibility of the valveless piezoelectric pump with multistage Y-shape treelike bifurcate tubes. The proposed research provides certain references for the design of valveless piezoelectric pump and improves the reliability of piezo water cooling systems.

Analysis of the Flow Rate Characteristics of Valveless Piezoelectric Pump with Fractal-like Y-shape Branching Tubes

Microchannel heat sink with high heat transfer coefficients has been extensively investigated due to its wide application prospective in electronic cooling. However, this cooling system requires a separate pump to drive the fluid transfer, which is uneasy to minimize and reduces their reliability and applicability of the whole system. In order to avoid these problems, valveless piezoelectric pump with fractal-like Y-shape branching tubes is proposed. Fractal-like Y-shape branching tube used in microchannel heat sinks is exploited as no-moving-part valve of the valveless piezoelectric pump. In order to obtain flow characteristics of the pump, the relationship between tube structure and flow rate of the pump is studied. Specifically, the flow resistances of fractal-like Y-shape branching tubes and flow rate of the pump are analyzed by using fractal theory. Then, finite element software is employed to simulate the flow field of the tube, and the relationships between pressure drop and flow rate along merging and dividing flows are obtained. Finally, valveless piezoelectric pumps with fractal-like Y-shape branching tubes with different fractal dimensions of diameter distribution are fabricated, and flow rate experiment is conducted. The experimental results show that the flow rate of the pump increases with the rise of fractal dimension of the tube diameter. When fractal dimension is 3, the maximum flow rate of the valveless pump is 29.16 mL/min under 100 V peak to peak （13 Hz） power supply, which reveals the relationship between flow rate and fractal dimensions of tube diameter distribution. This paper investigates the flow characteristics of valveless piezoelectric pump with fractal-like Y-shape branching tubes, which provides certain references for valveless piezoelectric pump with fractal-like Y-shape branching tubes in application on electronic chip cooling.

Simulation Analysis and Experimental Verification of Spiral-tube-type Valveless Piezoelectric Pump with Gyroscopic Effect

The current research of the valveless piezoelectric pump focuses on increasing the flow rate and pressure differential. Compared with the valve piezoelectric pump, the valveless one has excellent performances in simple structure, low cost, and easy miniaturization. So, their important development trend is the mitigation of their weakness, and the multi-function integration. The flow in a spiral tube element is sensitive to the element attitude caused by the Coriolis force, and that a valveless piezoelectric pump is designed by applying this phenomenon. The pump has gyroscopic effect, and has both the actuator function of fluid transfer and the sensor function, which can obtain the angular velocity when its attitude changes. First, the present paper analyzes the flow characteristics in the tube, obtains the calculation formula for the pump flow, and identifies the relationship between pump attitude and flow, which clarifies the impact of flow and driving voltage, frequency, spiral line type and element attitude, and verifies the gyroscopic effect of the pump. Then, the finite element simulation is used to verify the theory. Finally, a pump is fabricated for experimental testing of the relationship between pump attitude and pressure differential. Experimental results show that when Archimedes spiral θ=4π is selected for the tube design, and the rotation speed of the plate is 70 r/min, the pressure differential is 88.2 Pa, which is 1.5 times that of 0 r/min rotation speed. The spiral-tube-type valveless piezoelectric pump proposed can turn the element attitude into a form of pressure output, which is important for the multi-function integration of the valveless piezoelectric pump and for the development of civil gyroscope in the future.

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.

3D FEM Analyses on Flow Field Characteristics of the Valveless Piezoelectric Pump

Due to the special transportation and heat transfer characteristics,the fractal-like Y-shape branching tube is used in valveless piezoelectric pumps as a no-moving-part valve.However,there have been little analyses on the flow resistance of the valveless piezoelectric pump,which is critical to the performance of the valveless piezoelectric pump with fractal-like Y-shape branching tubes.Flow field of the piezoelectric pump is analyzed by the finite element method,and the pattern of the velocity streamlines is revealed,which can well explain the difference of total flow resistances of the piezoelectric pump.Besides,simplified numerical method is employed to calculate the export flow rate of piezoelectric pump,and the flow field of the piezoelectric pump is presented.The FEM computation shows that the maximum flow rate is 16.4 m L/min.Compared with experimental result,the difference between them is just 55.5%,which verifies the FEM method.The reasons of the difference between dividing and merging flow resistance of the valveless piezoelectric pump with fractal-like Y-shape branching tubes are also investigated in this method.The proposed research provides the instruction to design of novel piezoelectric pump and a rapid method to analyse the pump flow rate.

NUMERICAL STUDY OF PERIODICAL FLOWS OF PIEZOELECTRIC VALVELESS MICROPUMP FOR BIOCHIPS

Shallow water model was employed to approximate the three-dimensional flows of a thin micropump to a two-dimensional thickness-averaged flows. The finite element method and pressure correction algorithm were used to solve the two- dimensional flows of the pump and calculate the pump flow rate. The numerical results indicate that： 1 ） Phase differences in time of flow velocities and backflows occur across section of diffuser connecting to pump chamber; 2 ） A pair of symmetric vortexes appear inside the pump chamber at the end of suction flow phase; 3 ） The directional flow rate of the pump is dominated by nonlinearity of Navier-Stokes equations. Quantitative relations of the pump flow rate versus the ratio of diffuser length to width, the ratio of diffuser thickness to width, fluid viscosity and backpressure were also given. Possibly maximal flow rate can be achieved by optimizing the pump parameters.

Effects of structural parameters and rigidity of driving diaphragm on flow characteristics of micro valveless pump

The structure and operating principle of micro valveless pump were investigated theoretically and experimentally. The mathematical model of pressure and flow rate within the micro nozzle/diffuser was established to analyze the effects of nozzle/diffuser parameters on the output flow rate of the micro valveless pump.The experiments were carried out with different structural parameters, driving frequencies, vibration amplitudes and stiffness of the driving diaphragms. Effects of the structural parameters and driving conditions on the operation performance of the pump are discussed in detail. The work provides useful reference for structure optimization selection of the driving diaphragm of micro valveless pump.

Design and fabrication process of electromagnetically actuated valveless micropump with two parallel flexible diaphragms

A parallel dynamic passive valveless micropump was designed, which consists of three layers-valve, diaphragm and electromagnetic coil. The valve was wetly etched in a silicon wafer, the diaphragm was a PDMS （polydimethyl siloxane） film spun on a silicon wafer with embedded permanent magnet posts, and the coil was electroplated on a silicon substrate. Under the actuation of the magnetic field generated by coils, the flexible diaphragm could be displaced upwards and downwards. After analyzing magnetic and mechanical characteristic of the flexible membrane and direction-dependence of the nozzle, a micropump was designed. And the relative length （L/d） of the micropump nozzle was taken 4. A 7 × 7 array of permanent magnetic posts was embedded in the PDMS film. Two diaphragms worked in an anti-step mode, which could relieve the liquid shock and increase the discharge of the micropump. The ANSYS and Matlab were adopted to analyze the actuation effect of the coil and the flow characteristic of the micropump. Results show that when actuated under a 0.3 A, 100 Hz current, the displacement of the diaphragm is more than 30 μm, and the discharge of the micropump is about 6 μL/s.

半圆柱阻流体锥形腔无阀压电泵

为了提高半圆柱阻流体无阀压电泵的流量,结合锥形腔的流阻不等特性,该文设计了一种半圆柱阻流体锥形腔无阀压电泵,并建立了其流量的理论公式。数值模拟了该泵的泵腔流速分布,对比分析了其与半圆柱阻流体无阀压电泵的阻力特性。模拟结果表明,半圆柱阻流体锥形腔无阀压电泵能实现流体的单向输送,且其输送能力优于半圆柱阻流体无阀压电泵。制作了两种泵的样机并进行了流量和压力差试验。试验结果表明,在驱动电压220 V下,半圆柱阻流体锥形腔无阀压电泵的最高流量和压力差分别为30.96 g/min和394 Pa,与半圆柱阻流体无阀压电泵相比,其流量和压力差均得到提高。

Increasing operational stability of journal bearing in hydraulic suspension micro-pump by herringbone grooved structure

The operational stability of radial journal bearings is the bottleneck that limits the reliability of hydraulic suspension micropump. Due to self-excited vibrations, the whirl amplitude of the plain journal bearing(PJB) is large at high rotational speeds,which will accelerate wear failure. It has been proven that employing herringbone grooved journal bearing(HGJB) is an effective method to reduce the whirl amplitude and improve operational stability. However, enhancing the stability of journal bearings in micro-pumps by herringbone grooved structures has rarely been studied, and its effect needs to be verified. We validated the mechanism of the stability improvement with the CFD method and compared the dynamic characteristics of HGJB and PJB by rotor dynamics evaluation and experiment. The experimental results show that under the same conditions the whirl amplitude of the HGJB decreases by 29.61% in the x direction and by 24.09% in the y direction compared with that of the PJB. This study reveals the effect of the herringbone grooved structure on the operational stability of bearings and may provide guidance for the reliability improvement of hydraulic suspension micro-pump.

地下水厂除铁、锰工艺应用实例研究

简述了大通湖新建水厂(一期)取水情况及原水水质,并针对地下水铁、锰超标的情况进行处理工艺比选,最终选定穿孔管结合板条式曝气塔+重力无阀滤池的工艺进行处理,取得水质达标。本文还提供了穿孔管结合板条式曝气塔及重力无阀滤池详细的工艺设计参数,对同类型的水厂设计具有一定的参考意义。

微型无阀泵流动特征仿真与试验研究

介绍了微型无阀泵的结构及基本原理,应用 CFD（Computational fluid dynamics）技术对典型驱动频率下的流场流态进行了动态仿真。在不同结构参数、控制频率、振动幅值及驱动膜刚度等多种条件下,对无阀泵性能进行了试验研究。讨论了结构参数、驱动条件等因素对无阀泵流动特性的影响,分析了无阀泵管道周期、振动频率、驱动膜刚度等因素与流动参数之间的关系,在此基础上提出了微型无阀泵设计与控制的改进方案。

多级“Y”型流管无阀压电泵的原理与试验验证

针对目前微流体混合器多需要外接动力源,且多数微混合器只能进行液体混合而不能输送液体的问题,提出将无阀压电泵引入微混合器领域,并研制了一种集混合与输送于一体的多级"Y"型流管无阀压电泵。首先,提出了多级"Y"型流管,进而设计了多级"Y"型流管无阀压电泵,并分析其工作原理;然后,对该无阀压电泵的流管流阻特性及泵流量进行理论分析;同时,利用有限元软件对多级"Y"型流管无阀压电泵进行了流场模拟,结果表明该压电泵具有单向传输作用。最后,制作了多级"Y"型流管无阀压电泵样机,并进行了泵流量与背压试验。试验结果显示:驱动电压峰峰值为100V,频率为16Hz时,流量达到最大,为16.2ml/min;驱动电压峰峰值为100V,频率为14Hz时,输出背压最大,约为64mm水柱。得到的试验数据证明了多级"Y"型流管无阀压电泵的有效性。

用于微量化学分析芯片的微型无阀泵流动特性分析与测试

从理论计算、流场仿真和试验三方面研究了用于微流控化学分析芯片的微型无阀泵流动特性 ,初步建立了微型无阀泵流道结构的数学模型 ,重点讨论了结构参数的选取原则及相应的流动阻尼系数的计算方法 ,采用 Matlab针对该数学模型进行了数值计算 ,并进行了 CFD仿真对计算结果进行对比及修正 ,最后通过试验验证了数值计算与仿真的可靠性 ,为微型无阀泵参数化设计及优化提供了理论依据及经验曲线。

微型无阀泵的数值仿真与参数设计

介绍了无阀型微泵的特点及其工作原理 ;针对无阀微型泵收缩 /扩散口的流动特征进行了数值分析 ,得出了流量、压力的分布特征和关系曲线 ,分析了收缩 /扩散口的几何参数对泵的输出性能的影响。采用CFD(ComputationalFluidDynamics)技术对泵内流体进行了有限元仿真 ,并将仿真与计算结果进行了分析比较。