Micromachines

Research

15 pages, 3838 KiB

Open AccessArticle

Simulation Research of Hydraulic Stepper Drive Technology Based on High Speed On/Off Valves and Miniature Plunger Cylinders

by Hanyu Qiu and Qi Su

Micromachines 2021, 12(4), 438; https://doi.org/10.3390/mi12040438 - 15 Apr 2021

Cited by 4 | Viewed by 2159

Abstract

The technology for stepper drive that can achieve accurate motion in the hydraulic field has always been urgently needed in the industry. This paper proposes a hydraulic stepper drive based on five high speed on/off valves and two miniature plunger cylinders. The stepper [...] Read more.

The technology for stepper drive that can achieve accurate motion in the hydraulic field has always been urgently needed in the industry. This paper proposes a hydraulic stepper drive based on five high speed on/off valves and two miniature plunger cylinders. The stepper drive discretizes the continuous flow medium into fixed small steps through the miniature plunger cylinder and realizes the state control of the drive through the logic action of the high speed on/off valve. This paper improves the current stepper drive and establishes a mathematical model to analyze the error of the drive and calculate the position of the actuator. In addition, through simulation research, the performance parameters such as the single-step step characteristic and pressure characteristic of the stepper drive are studied. The results show that, compared with the technology of current stepper drive, this stepper drive can effectively remove the “post step” phenomenon, greatly improve the stepper accuracy of the stepper drive, and have a more excellent performance. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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15 pages, 3146 KiB

Open AccessArticle

Design and Performance Study for Electrothermally Deep-Sea Drive Microunits Using a Paraffin Phase Change Material

by Dayong Ning, Zihao Li, Gangda Liang, Qibo Wang, Weifeng Zou, Yongjun Gong and Jiaoyi Hou

Micromachines 2021, 12(4), 415; https://doi.org/10.3390/mi12040415 - 09 Apr 2021

Cited by 3 | Viewed by 1733

Abstract

Considering the further exploration of the ocean, the requirements for deep-sea operation equipment have increased. Many problems existing in the widely used deep-sea hydraulic system have become increasingly prominent. Compared with the traditional deep-sea hydraulic system, actuators using a paraffin phase change material [...] Read more.

Considering the further exploration of the ocean, the requirements for deep-sea operation equipment have increased. Many problems existing in the widely used deep-sea hydraulic system have become increasingly prominent. Compared with the traditional deep-sea hydraulic system, actuators using a paraffin phase change material (PCM) have incomparable advantages, including lightweight structure, low energy consumption, high adaptability to the deep sea, and good biocompatibility. Thus, a deep-sea drive microunit (DDM) based on paraffin PCM is proposed in this paper. The device adopts a flexible shell, adapting to the high-pressure environment of the deep-sea based on the principle of pressure compensation. The device realizes the output of displacement and force through the electrothermal drive, which can be used as actuator or power source of other underwater operation equipment. The microunit successfully completes the functional verification experiments in air, shallow water, and hydrostatic pressure of 110 MPa. In accordance with experimental results, a reasonable control curve is fitted, highlighting its potential application in deep-sea micro electro mechanical systems, especially in underwater soft robot. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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15 pages, 5110 KiB

Open AccessArticle

An Empirical Model for the Churning Losses Prediction of Fluid Flow Analysis in Axial Piston Pumps

by Ying Li, Xing Chen, Hao Luo and Jin Zhang

Micromachines 2021, 12(4), 398; https://doi.org/10.3390/mi12040398 - 03 Apr 2021

Cited by 5 | Viewed by 2595

Abstract

The manufacturing development of axial piston pumps usually takes the trend of high speed and miniaturization, and increases power density. Axial piston pumps are usually characterized as high speed to improve the power density; thus, high-speed churning losses caused by the internal rotating [...] Read more.

The manufacturing development of axial piston pumps usually takes the trend of high speed and miniaturization, and increases power density. Axial piston pumps are usually characterized as high speed to improve the power density; thus, high-speed churning losses caused by the internal rotating components stirring the oil can increase significantly. In order to improve the efficiency, more attention should be given to the churning losses in axial piston pumps, especially in high-speed conditions. Using the method of least-squares curve fitting, this paper establishes a series of formulas based on the churning losses test rig over a wide range of speeds, which enable accurate predictions of churning losses on the cylinder block and pistons. The reduction coefficient of flow resistance of multi-pistons as calculated. The new churning losses formula devoted to the cylinder block and rotating pistons was validated by comparison with experimental evidence in different geometries of axial piston pumps. According to the prediction model of churning losses, some valuable guidance methods are proposed to reduce the energy losses of the axial piston pump, which are the theoretical support for the miniaturization of axial piston pump manufacturing. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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11 pages, 2885 KiB

Open AccessArticle

A Trilaminar-Catalytic Layered MEA Structure for a Passive Micro-Direct Methanol Fuel Cell

by Huichao Deng, Jiaxu Zhou and Yufeng Zhang

Micromachines 2021, 12(4), 381; https://doi.org/10.3390/mi12040381 - 01 Apr 2021

Cited by 5 | Viewed by 1898

Abstract

A membrane electrode assembly (MEA) with a novel trilaminar-catalytic layered structure was designed and fabricated for a micro-direct methanol fuel cell (μ-DMFC). The trilaminar-catalytic layer comprises three porous layers. The medial layer has a lower porosity than the inner and outer layers. The [...] Read more.

A membrane electrode assembly (MEA) with a novel trilaminar-catalytic layered structure was designed and fabricated for a micro-direct methanol fuel cell (μ-DMFC). The trilaminar-catalytic layer comprises three porous layers. The medial layer has a lower porosity than the inner and outer layers. The simulation results predicted a lower water content and a higher oxygen concentration in the trilaminar-catalytic layer. The novel trilaminar-catalytic layer enhanced the back diffusion of water from the cathode to the anode, which reduces methanol crossover and improves oxygen mass transportation. The electrochemical results of the half-cell test indicate that the novel MEA has a greatly increased cathode polarization and a slightly increased anode polarization. Thus, this novel μ-DMFC structure has a higher power density and a longer discharging time, and hence may be used in portable systems. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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18 pages, 9148 KiB

Open AccessArticle

Design and Simulation of Air-Breathing Micro Direct Methanol Fuel Cells with Different Anode Flow Fields

by Huichao Deng, Jiaxu Zhou and Yufeng Zhang

Micromachines 2021, 12(3), 253; https://doi.org/10.3390/mi12030253 - 02 Mar 2021

Cited by 3 | Viewed by 1793

Abstract

The design of the anode flow field is critical for yielding better performance of micro direct methanol fuel cells (µDMFCs). In this work, the effect of different flow fields on cell performance was investigated by the simulation method. Compared with grid, parallel and [...] Read more.

The design of the anode flow field is critical for yielding better performance of micro direct methanol fuel cells (µDMFCs). In this work, the effect of different flow fields on cell performance was investigated by the simulation method. Compared with grid, parallel and double-serpentine flow fields, a single-serpentine flow field can better improve the mass transfer efficiency of methanol and the emission efficiency of the carbon dioxide by-product. The opening ratio and channel length also have important effects on the cell performance. The cells were manufactured using silicon-based micro-electro-mechanical system (MEMS) technologies and tested to verify the simulation results. The experimental results show that the single-serpentine flow field represents a higher peak power density (16.83 mWcm⁻²) than other flow fields. Moreover, the results show that an open ratio of 47.3% and a channel length of 63.5 mm are the optimal parameters for the single-serpentine flow field. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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14 pages, 9106 KiB

Open AccessArticle

Hydraulic and Thermal Performance of Microchannel Heat Sink Inserted with Pin Fins

by Guo-Fu Xie, Lei Zhao, Yuan-Yuan Dong, Yu-Guang Li, Shang-Lin Zhang and Chen Yang

Micromachines 2021, 12(3), 245; https://doi.org/10.3390/mi12030245 - 28 Feb 2021

Cited by 12 | Viewed by 2036

Abstract

With the development of micromachining technologies, a wider use of microchannel heat sink (MCHS) is achieved in many fields, especially for cooling electronic chips. A microchannel with a width of 500 μm and a height of 500 μm is investigated through the numerical [...] Read more.

With the development of micromachining technologies, a wider use of microchannel heat sink (MCHS) is achieved in many fields, especially for cooling electronic chips. A microchannel with a width of 500 μm and a height of 500 μm is investigated through the numerical simulation method. Pin fins are arranged at an inclined angle of 0°, 30°, 45°, and 60°, when arrangement method includes in-lined pattern and staggered pattern. The effects of inclined angle and arrangement method on flow field and temperature field of MCHSs are studied when Reynolds number ranges from 10 to 300. In addition to this, quantitative analyses of hydraulic and thermal performance are also discussed in this work. With the increase of inclined angle, the variation of friction factor and Nusselt number do not follow certain rules. The best thermal performance is achieved in MCHS with in-lined fines at an inclined angle of 30° accompanied with the largest friction factor. Arrangement method of pin fins plays a less significant role compared with inclined angle from a general view, particularly in the Reynolds number range of 100~300. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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15 pages, 6392 KiB

Open AccessArticle

Experimental Study on the Coating Removing Characteristics of High-Pressure Water Jet by Micro Jet Flow

by Dayong Ning, Qibo Wang, Jinxin Tian, Yongjun Gong, Hongwei Du, Shengtao Chen and Jiaoyi Hou

Micromachines 2021, 12(2), 173; https://doi.org/10.3390/mi12020173 - 10 Feb 2021

Cited by 13 | Viewed by 3011

Abstract

In this paper, coating removal characteristics of water jet by micro jet flow affected by cleaning parameters is analyzed. Numerical simulation of fluid field calculates the velocity and pressure distribution of a water jet impinging on a rigid wall, which is used for [...] Read more.

In this paper, coating removal characteristics of water jet by micro jet flow affected by cleaning parameters is analyzed. Numerical simulation of fluid field calculates the velocity and pressure distribution of a water jet impinging on a rigid wall, which is used for design experiments of coating removal affected by jet pressure, traversal speed, and repeated impacting times. The removal width is used as a measure of water jet coating removal capability. Experiment results show that the coating removal width is constant, independent with traversal speed or repeated times when total exposure time of waterjet impingement is fixed. According to results of coating removal by a linear moving water jet, this study also analyzes characteristics of coating removal by rotating jet disc, especially residual coating affected by rotational and moving speed of the cleaning disc. The research is helpful to improve the coating removal efficiency of cleaning disc devices. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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13 pages, 3623 KiB

Open AccessArticle

Numerical Study of the Microflow Characteristics in a V-ball Valve

by Zhi-xin Gao, Yang Yue, Jia-ming Yang, Jun-ye Li, Hui Wu and Zhi-jiang Jin

Micromachines 2021, 12(2), 155; https://doi.org/10.3390/mi12020155 - 04 Feb 2021

Cited by 4 | Viewed by 2740

Abstract

V-ball valves are widely applied in many process industries to regulate fluid flow, and they have advantages of good approximately equal percentage flow characteristics and easy maintenance. However, in some applications, the V-ball valve needs to have good performance under both large and [...] Read more.

V-ball valves are widely applied in many process industries to regulate fluid flow, and they have advantages of good approximately equal percentage flow characteristics and easy maintenance. However, in some applications, the V-ball valve needs to have good performance under both large and extremely small flow coefficients. In this paper, the improvement of the original V-ball valve is made and the flow characteristics between the original and the improved V-ball valve are compared. Two types of small gaps are added to the original V-ball, namely the gap with an approximately rectangular port and the gap with an approximately triangular port. The effects of the structure and the dimension of the gap on flow characteristics are investigated. Results show that within the gap, the flow coefficient increases but the loss coefficient decreases as the valve opening increases, and the flow coefficient has an approximately linear relationship with the flow cross-area of the added gap. Results also show that under the same flow cross-area, the flow coefficient has a higher value if the distance between the gap and the ball center is greater or if the gap is an approximately rectangular port, while the loss coefficient has an opposite trend. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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14 pages, 5677 KiB

Open AccessArticle

Dynamic Analysis of an Underwater Cable-Driven Manipulator with a Fluid-Power Buoyancy Regulation System

by Tong Wang, Zihao You, Wei Song and Shiqiang Zhu

Micromachines 2020, 11(12), 1042; https://doi.org/10.3390/mi11121042 - 26 Nov 2020

Cited by 6 | Viewed by 2656

Abstract

This article presents an underwater cable-driven manipulator (UCDM) with a buoyancy regulation system (BRS), which is controlled by a fluid-power system. The manipulator consists of five sections, and each section is embedded with a buoyancy adjustment unit. By regulating buoyancy at each section, [...] Read more.

This article presents an underwater cable-driven manipulator (UCDM) with a buoyancy regulation system (BRS), which is controlled by a fluid-power system. The manipulator consists of five sections, and each section is embedded with a buoyancy adjustment unit. By regulating buoyancy at each section, the static and dynamic states of the manipulator will be changed, promising a new operating mode of an underwater manipulator driven by buoyancy. In this article, a dynamic model of the manipulator is established by the Newton-Euler equation, considering cable tension, inter-joint force, buoyancy, water resistance and other variables. With a numerical method, the dynamic model is solved and the values of cable tension are obtained, which are used to evaluate the buoyancy-driven operating mode of underwater manipulator. This research will be useful for manipulator operating in fluid environments, such as underwater manipulator in the ocean, micro-manipulator in a blood vessel, and so on. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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16 pages, 31014 KiB

Open AccessArticle

Development and Experiments of an Electrothermal Driven Deep-Sea Buoyancy Control Module

by Jiaoyi Hou, Weifeng Zou, Zihao Li, Yongjun Gong, Vitalii Burnashev and Dayong Ning

Micromachines 2020, 11(11), 1017; https://doi.org/10.3390/mi11111017 - 19 Nov 2020

Cited by 14 | Viewed by 2835

Abstract

Due to the extremely high pressures in the deep sea, heavy ballast tanks and pressure compensating hydraulic tanks are typically required to support the operation of classic buoyancy controls. Buoyancy control systems driven by phase-change materials (PCM) have unique advantages over conventional hydraulically [...] Read more.

Due to the extremely high pressures in the deep sea, heavy ballast tanks and pressure compensating hydraulic tanks are typically required to support the operation of classic buoyancy controls. Buoyancy control systems driven by phase-change materials (PCM) have unique advantages over conventional hydraulically actuated buoyancy control systems, including high adaptability for deep-sea exploration and simple, lightweight, and compact structures. Inspired by this, a buoyancy control module (BCM) was designed with flexible material as the shell. Instead of a conventional mechanical system, the device uses an electric heating drive to control buoyancy by heating and cooling the PCM. Based on the principle of pressure compensation, this device can adjust the buoyancy of a small underwater vehicle in a deep-sea high-pressure environment. The BCM successfully adjusts the buoyancy to lift itself up and down in the South China Sea at a depth of 3223 m. The performance of the phase-change BCM to control buoyancy under high pressure is validated by systematic experiments and theoretical analysis. Our work proposes a flexible scheme for the design of a deep-sea phase-change-driven BCM and highlights its potential application in deep-sea micro-mechanical systems, especially soft robots. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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21 pages, 1528 KiB

Open AccessArticle

Analytical Solution of Mixed Electroosmotic/Pressure Driven Flow of Viscoelastic Fluids between a Parallel Flat Plates Micro-Channel: The Maxwell Model Using the Oldroyd and Jaumann Time Derivatives

by Laura Casas, José A. Ortega, Aldo Gómez, Juan Escandón and René O. Vargas

Micromachines 2020, 11(11), 986; https://doi.org/10.3390/mi11110986 - 31 Oct 2020

Cited by 6 | Viewed by 1908

Abstract

In the present work, an analytical approximate solution of mixed electroosmotic/pressure driven flow of viscoelastic fluids between a parallel plates microchannel is reported. Inserting the Oldroyd, Jaumann, or both time derivatives into the Maxwell model, important differences in the velocity profiles were found. [...] Read more.

In the present work, an analytical approximate solution of mixed electroosmotic/pressure driven flow of viscoelastic fluids between a parallel plates microchannel is reported. Inserting the Oldroyd, Jaumann, or both time derivatives into the Maxwell model, important differences in the velocity profiles were found. The presence of the shear and normal stresses is only close to the wall. This model can be used as a tool to understand the flow behavior of low viscosity fluids, as most of them experiment on translation, deformation and rotation of the flow. For practical applications, the volumetric flow rate can be controlled with two parameters, namely the gradient pressure and the electrokinetic parameter, once the fluid has been rheologically characterized. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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18 pages, 7731 KiB

Open AccessArticle

Ring-Shaped Baffle Effect on Separation Performance of Lithium Carbonate Micro Particles in a Centrifugal Classifier

by Moonjeong Kim, Jemyung Cha and Jeung Sang Go

Micromachines 2020, 11(11), 980; https://doi.org/10.3390/mi11110980 - 30 Oct 2020

Cited by 1 | Viewed by 1851

Abstract

In this work, a centrifugal classifier for separating lithium carbonate particles, used as a cathode material for lithium-ion batteries, was investigated. This work numerically evaluates the internal flow and particle separation performance of the centrifugal classifier. The complex turbulent flow field in the [...] Read more.

In this work, a centrifugal classifier for separating lithium carbonate particles, used as a cathode material for lithium-ion batteries, was investigated. This work numerically evaluates the internal flow and particle separation performance of the centrifugal classifier. The complex turbulent flow field in the classifier is key to understanding particle motion. A Reynolds stress model, to describe air flow field, and a discrete phase model, to track particle motion, were applied to a numerical simulation. Design parameters such as mass flow rate and rotor speed were investigated, and a ring-shaped baffle, in particular, was designed to investigate the effects of flow and particle separation in the centrifugal classifier. The simple geometry of the baffle changes the movement direction of unseparated particles to the rotor cage region, and increases the local air velocity in the separation zone. The numerical analysis results were verified through a baffle experiment. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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11 pages, 5219 KiB

Open AccessArticle

Effect of Blade Outlet Angle on the Flow Field and Preventing Overload in a Centrifugal Pump

by Guangjie Peng, Qiang Chen, Ling Zhou, Bo Pan and Yong Zhu

Micromachines 2020, 11(9), 811; https://doi.org/10.3390/mi11090811 - 27 Aug 2020

Cited by 11 | Viewed by 2924

Abstract

The influence of the blade outlet angle on preventing overload in a submersible centrifugal pump and the pump performance characteristics were studied numerically for a low specific speed multi-stage submersible pump. The tested blade outlet angles were 16°, 20°, 24°, 28°, and 32°. [...] Read more.

The influence of the blade outlet angle on preventing overload in a submersible centrifugal pump and the pump performance characteristics were studied numerically for a low specific speed multi-stage submersible pump. The tested blade outlet angles were 16°, 20°, 24°, 28°, and 32°. The results show that the blade outlet angle significantly affects the external flow characteristics and the power curve can be controlled to prevent overload by properly reducing the blade outlet angle. Increasing the blade outlet angle significantly increases the low pressure area at the impeller inlet, which makes cavitation more likely. Therefore, β₂ = 16° provides the best anti-cavitation flow field. Increasing the blade outlet angle also increases the flow separation near the blade working face, which increases the size of the axial vortex along the blade working surface, which rotates in the direction opposite to the impeller rotation and then extends towards the impeller inlet. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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14 pages, 4680 KiB

Open AccessArticle

Influence of Non-Structural Parameters on Dual Parallel Jet Characteristics of Porous Nozzles

by Jin Zhang, Ruiqi Lv, Qifan Yang, Baolei Liu and Ying Li

Micromachines 2020, 11(8), 772; https://doi.org/10.3390/mi11080772 - 14 Aug 2020

Cited by 2 | Viewed by 2362

Abstract

As an important actuator of the dual parallel jet, the porous nozzle has some non-structural parameters (such as inlet pressure, nozzle spacing ratio, etc.) which have a significant influence on energy transport, chemical combustion and pollutant generation. The research on the microfluidic state [...] Read more.

As an important actuator of the dual parallel jet, the porous nozzle has some non-structural parameters (such as inlet pressure, nozzle spacing ratio, etc.) which have a significant influence on energy transport, chemical combustion and pollutant generation. The research on the microfluidic state of the porous nozzle dual parallel jet, however, remains insufficient because of its microjet pattern and complex intersection process. In this paper, the authors used numerical simulation and an experimental method to clarify the influence of porous nozzles’ non-structural parameters on dual parallel jet characteristics. The results show that the inlet pressure only changes the pressure peak value on the parallel jet axis; the starting point (SP) and peak point (PP) on the parallel jet axis, which are located at X_sp = 22 mm and X_pp = 75 mm, respectively, are not changed; and with the increase in the nozzle spacing ratio, the merging points (MPs) on the parallel jet axis are X_mp = 25 mm, 32 mm and 59 mm, respectively. The merging point and the combined point move to a farther distance and the inner deflection angle of the jet is weakened. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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13 pages, 3666 KiB

Open AccessArticle

Comparison of Swing and Tilting Check Valves Flowing Compressible Fluids

by Zhi-xin Gao, Ping Liu, Yang Yue, Jun-ye Li and Hui Wu

Micromachines 2020, 11(8), 758; https://doi.org/10.3390/mi11080758 - 06 Aug 2020

Cited by 8 | Viewed by 4834

Abstract

Although check valves have attracted a lot of attention, work has rarely been completed done when there is a compressible working fluid. In this paper, the swing check valve and the tilting check valve flowing high-temperature compressible water vapor are compared. The maximum [...] Read more.

Although check valves have attracted a lot of attention, work has rarely been completed done when there is a compressible working fluid. In this paper, the swing check valve and the tilting check valve flowing high-temperature compressible water vapor are compared. The maximum Mach number under small valve openings, the dynamic opening time, and the hydrodynamic moment acting on the valve disc are chosen to evaluate the difference between the two types of check valves. Results show that the maximum Mach number increases with the decrease in the valve opening and the increase in the mass flow rate, and the Mach number and the pressure difference in the tilting check valve are higher. In the swing check valve, the hydrodynamic moment is higher and the valve opening time is shorter. Furthermore, the valve disc is more stable for the swing check valve, and there is a periodical oscillation of the valve disc in the tilting check valve under a small mass flow rate. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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14 pages, 10161 KiB

Open AccessArticle

Numerical Calculation of Energy Performance and Transient Characteristics of Centrifugal Pump under Gas-Liquid Two-Phase Condition

by Ling Zhou, Yong Han, Wanning Lv, Yang Yang, Yong Zhu and Xiangyu Song

Micromachines 2020, 11(8), 728; https://doi.org/10.3390/mi11080728 - 28 Jul 2020

Cited by 7 | Viewed by 1900

Abstract

The unstable operation of a centrifugal pump under the gas-liquid two-phase condition seriously affects its performance and reliability. In order to study the gas phase distribution and the unsteady force in an impeller, based on the Euler-Euler heterogeneous flow model, the steady and [...] Read more.

The unstable operation of a centrifugal pump under the gas-liquid two-phase condition seriously affects its performance and reliability. In order to study the gas phase distribution and the unsteady force in an impeller, based on the Euler-Euler heterogeneous flow model, the steady and unsteady numerical calculations of the gas-liquid two-phase full flow field in a centrifugal pump was carried out, and the simulation results were compared with the test data. The results show that the test results are in good agreement with the simulation data, which proves the accuracy of the numerical calculation method. The energy performance curve of the model pump decreases with the increase of the gas content, which illustrates a serious impact on the performance under the part-load operating condition. The results reveal that the high-efficiency-operating range become narrow, as the gas content increases. The gas phase is mainly distributed on the suction surface of the impeller blades. When the gas content reaches a certain value, the gas phase separation occurs. As the inlet gas content increases, the radial force on the impeller blades decreases. The pattern of the pressure pulsation is similar to that under pure water and low gas content conditions, and the number of peaks during the pulsation is equal to the number of the impeller blades. After the gas content reaches a certain value, the pressure fluctuates disorderly and the magnitude and the direction of radial force change frequently, which are detrimental to the operation stability of the pump. The intensity of the pressure pulsations in the impeller flow channel continues to increase in the direction of the flow under pure water conditions. The pressure pulsation intensities at the blade inlet and the volute tongue become more severe with the increase of the gas content. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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