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 characte...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.展开更多
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 ...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.展开更多
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 compli...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.展开更多
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 dri...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.展开更多
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 simpl...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.展开更多
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 ...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.展开更多
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...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.展开更多
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 s...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.展开更多
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 an...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.展开更多
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 (polydime...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.展开更多
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(PJ...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.展开更多
基金the National Natural Science Foundation of China(Grant Nos.61376115,11672065).
文摘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.
基金Supported by National Natural Science Foundation of China(Grant Nos.51375227,51605200)Jiangsu Provincial Natural Science Foundation of China(Grant No.BK20150518)
文摘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.
基金supported by National Natural Science Foundation of China (Grant Nos. 50775109, 50735002, 51075201)Open Fund of State Key Lab of Digital Manufacturing Equipment and Technology of Huazhong University of Science and Technology of China (Grant No.DMETKF2009002)
文摘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.
基金Supported by National Natural Science Foundation of China(Grant Nos.51275235,51375227)Major Research Plan of National Natural Science Foundation of China(Grant No.91223201)Independent Projects Fund of State Key Lab of Mechanics and Control of Mechanical Structures of China(Grant No.0313G01)
文摘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.
基金Supported by National Natural Science Foundation of China(Grant Nos.51075201,51205193,51375227)
文摘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.
基金supported by National Natural Science Foundation of China (Grant No. 50735002, Grant No. 50775109, and Grant No. 51075201)
文摘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.
基金Supported by National Natural Science Foundation of China(Grant No.51375227)Jiangsu Provincial Natural Science Foundation of China(Grant No.BK20150518)+1 种基金Postdoctoral Science Foundation of Jiangsu Province(Grant No.1501108B)Senior Talent Start-up Foundation of Jiangsu University(Grant No.14JDG145)
文摘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.
文摘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.
文摘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.
文摘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.
基金supported by the Open Fund of Science and Technology on Thermal Energy and Power Laboratory(Grant No. TPL 2019B03)。
文摘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.