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
A new type of high-frequency micro-pump was designed, in which GMA (Giant Magnetostrictive Actuator) was employed to replace the traditional motor drive, owing to its significant characteristics of fast response, high...A new type of high-frequency micro-pump was designed, in which GMA (Giant Magnetostrictive Actuator) was employed to replace the traditional motor drive, owing to its significant characteristics of fast response, high accuracy, easily miniaturized and so on. Both the mathematic and simulation models of the micro-pump were built.A set of raw data was used for simulation studies.The results show that the micro-pump based on GMA has achieved the features of high-frequency response and high accuracy, theoretically displaying the performance merits of a giant magnetostrictive material (GMM) high-frequency micro-pump.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 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 the National Natural Science Foundation of China(59835160)the National Natural Science Foundation of Anhui Province(070414268x)
文摘A new type of high-frequency micro-pump was designed, in which GMA (Giant Magnetostrictive Actuator) was employed to replace the traditional motor drive, owing to its significant characteristics of fast response, high accuracy, easily miniaturized and so on. Both the mathematic and simulation models of the micro-pump were built.A set of raw data was used for simulation studies.The results show that the micro-pump based on GMA has achieved the features of high-frequency response and high accuracy, theoretically displaying the performance merits of a giant magnetostrictive material (GMM) high-frequency micro-pump.
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.
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.
