Effective splitting of serpentine flow field for applications in large-scale flow batteries

In the present work, we studied the three-dimensional (3D) mean flow field in a micro electrokinetic (μEK) turbulence based micromixer by micro particle imaging velocimetry (μPIV) with stereoscopic method. A large-scale solenoid-type 3D mean flow field has been observed. The extraordinarily fast mixing process of the μEK turbulent mixer can be primarily attributed to two steps. First, under the strong velocity fluctuations generated by μEK mechanism, the two fluids with different conductivity are highly mixed near the entrance, primarily at the low electric conductivity sides and bias to the bottom wall. Then, the well-mixed fluid in the local region convects to the rest regions of the micromixer by the large-scale solenoid-type 3D mean flow. The mechanism of the large-scale 3D mean flow could be attributed to the unbalanced electroosmotic flows (EOFs) due to the high and low electric conductivity on both the bottom and top surface.

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A Numerical Simulations and Optimizations of the Flow Field in TengZhou Quanshang Constructed Wetland

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.212-213.201 ◽

2012 ◽

Vol 212-213 ◽

pp. 201-204

Author(s):

Wei Gang Xu ◽

Hua Yong Zhang ◽

Zhong Yu Wang ◽

Wen Pei Huang

Keyword(s):

Flow Field ◽

Constructed Wetland ◽

Large Scale ◽

Flow Analysis ◽

Initial State ◽

Measured Velocity ◽

Efficient Operation ◽

Water Quality Simulation ◽

Vof Model ◽

Large Scale Flow

The flow field of constructed wetland plays an important role in wetland stabilization and efficient operation. TengZhou Quanshang constructed wetland was taken as the research object. The RNG k-ε two-equation turbulence model equations coupling with the volume of fluid (VOF) model are introduced to simulation the vegetation cover flow. And the flow velocities of 37 measured points in wetland were measured by using the ADV instrument. Then the simulation velocity was compared with the field measured velocity. The results are shown to be satisfactory, and basically meet the large-scale flow analysis requirements. The problems of flow field distribution on the initial state was analyzed and optimized. The uniformity of velocity in wetland increased, and water mobility improved after optimization. Our results provide guidance for the 2D water quality simulation, pollutants migration and combination of plant purification effect in natural and constructed wetland.

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Analysis of large-scale flow characteristics in a four-valve spark ignition engine

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/095440620221600906 ◽

2002 ◽

Vol 216 (9) ◽

pp. 923-938 ◽

Cited By ~ 12

Author(s):

Y Li ◽

H Zhao ◽

N Ladommatos

Keyword(s):

Flow Field ◽

Velocity Fluctuation ◽

Large Scale ◽

Engine Speed ◽

Flow Characteristics ◽

Low Frequency ◽

Length Scale ◽

Intake Port ◽

Compression Stroke ◽

Large Scale Flow

A digital particle image velocimetry (PIV) measurement has been carried out to study the large-scale flow characteristics in a single-cylinder engine with a production-type four-valve cylinder head under one intake port deactivation. The measurement plane was located 12 mm below the cylinder head parallel to the flat piston top. Two-dimensional velocity fields from 100 consecutive cycles were acquired at every 30 crank angle interval in the compression stroke to analyse ensemble-averaged mean velocity, cyclic variation of the swirl motion, low-frequency and total velocity fluctuations and their integral length scales. The analysis shows that as one intake port is deactivated, strong swirl forms at the end of the intake stroke and sustains its flow pattern up to the late stage of the compression stroke with the precessing of the swirl centre. Both swirl ratio and swirl centre show significant cyclic variations in the compression process. A low-frequency component with spatial frequency below 0.05 mm-1 (corresponding to a large-scale structure with a spatial scale over 20 mm) is absolutely predominant in the flow field and therefore the low-frequency large-scale flow behaviour determines the basic characteristics of the total in-cylinder flow. The flow field is considerably anisotopic because the integral length scale of any velocity fluctuation components along any direction is different. However, the velocity fluctuation field in the horizontal plane will gradually become homogeneous as the piston moves up in the compression stroke. The integral length scale is in the range of 4-10 mm at an engine speed of 600 r/min. When the engine speed is doubled, flow velocity in the cylinder nearly doubles and velocity fluctuation kinetic energy more than triples though the flow pattern hardly changes.

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(Industrial Electrochemistry and Electrochemical Engineering Division Student Achievement Award Address) Fundamental Understanding on Cell Performance Enhancement of Flow Batteries with Serpentine Flow Field Structures

ECS Meeting Abstracts ◽

10.1149/ma2019-01/19/1077 ◽

2019 ◽

Keyword(s):

Student Achievement ◽

Flow Field ◽

Performance Enhancement ◽

Cell Performance ◽

Electrochemical Engineering ◽

Achievement Award ◽

Serpentine Flow Field ◽

Fundamental Understanding ◽

Flow Batteries

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High-Rayleigh-number convection of pressurized gases in a horizontal enclosure

Journal of Fluid Mechanics ◽

10.1017/s002211200200174x ◽

2002 ◽

Vol 469 ◽

pp. 1-12 ◽

Cited By ~ 27

Author(s):

A. S. FLEISCHER ◽

R. J. GOLDSTEIN

Keyword(s):

Heat Transfer ◽

High Pressure ◽

Rayleigh Number ◽

Flow Field ◽

Large Scale ◽

Data Set ◽

Video Images ◽

Large Scale Flow ◽

Rayleigh Benard Convection ◽

Rayleigh Benard

High-pressure gases are used to study high-Rayleigh-number Rayleigh–Bénard convection in cylindrical horizontal enclosures. The Nusselt–Rayleigh heat transfer relationship is investigated for 1×109 < Ra < 1.7×1012. Schlieren video images of the flow field are recorded through optical viewports in the pressure vessel. The data set is well correlated by Nu = 0.071Ra0.328. The schlieren results confirm the existence of a large-scale flow that periodically interrupts the ascending and descending plumes. The intensity of both the plumes and the large-scale flow increases with Rayleigh number.

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Proper Orthogonal Decomposition Analysis of Non-Swirling Turbulent Stratified and Premixed Methane/Air Flames

Volume 4B: Combustion, Fuels and Emissions ◽

10.1115/gt2014-26222 ◽

2014 ◽

Author(s):

M. Mustafa Kamal ◽

Christophe Duwig ◽

Saravanan Balusamy ◽

Ruigang Zhou ◽

Simone Hochgreb

Keyword(s):

Flow Field ◽

Proper Orthogonal Decomposition ◽

High Speed ◽

Large Scale ◽

Bluff Body ◽

Decomposition Analysis ◽

Orthogonal Decomposition ◽

Stereoscopic Particle Image Velocimetry ◽

Large Scale Flow ◽

Proper Orthogonal

This paper reports proper orthogonal decomposition (POD) analyses for the velocity fields measured in a test burner. The Cambridge/Sandia Stratified Swirl Burner has been used in various studies as a benchmark for high resolution scalar and velocity measurements, for comparison with numerical model prediction. Flow field data was collected for a series of bluff-body stabilized premixed and stratified methane/air flames at turbulent, globally lean conditions (ϕ = 0.75) using high speed stereoscopic particle image velocimetry (HS-SPIV). In this paper, a modal analysis was performed to identify the large scale flow structures and their impact on the flame dynamics. The high speed PIV system was operated at 3 kHz to acquire a series of 4096 sequential flow field images both for reactive and non-reactive cases, sufficient to follow the large-scale spatial and temporal evolution of flame and flow dynamics. The POD analysis allows identification of vortical structures, created by the bluff body, and in the shear layers surrounding the stabilization point. In addition, the analysis reveals that dominant structures are a strong function of the mixture stratification in the flow field. The dominant energetic modes of reactive and non-reactive flows are very different, as the expansion of gases and the high temperatures alter the unstable modes and their survival in the flow.

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Development of Flow Fields for Zinc Slurry Air Flow Batteries

Batteries ◽

10.3390/batteries6010015 ◽

2020 ◽

Vol 6 (1) ◽

pp. 15

Author(s):

Nak Choi ◽

Diego del Olmo ◽

Peter Fischer ◽

Karsten Pinkwart ◽

Jens Tübke

Keyword(s):

Flow Field ◽

Power Density ◽

Air Flow ◽

Bipolar Plate ◽

Flow Fields ◽

Discharge Power ◽

Plate Material ◽

Viscous Liquids ◽

Serpentine Flow Field ◽

Flow Batteries

The flow field design and material composition of the electrode plays an important role in the performance of redox flow batteries, especially when using highly viscous liquids. To enhance the discharge power density of zinc slurry air flow batteries, an optimum slurry distribution in the cell is key. Hence, several types of flow fields (serpentine, parallel, plastic flow frames) were tested in this study to improve the discharge power density of the battery. The serpentine flow field delivered a power density of 55 mW∙cm−2, while parallel and flow frame resulted in 30 mW∙cm−2 and 10 mW∙cm−2, respectively. Moreover, when the anode bipolar plate material was changed from graphite to copper, the power density of the flow frame increased to 65 mW∙cm−2, and further improvement was attained when the bipolar plate material was further changed to copper–nickel. These results show the potential to increase the power density of slurry-based flow batteries by flow field optimization and design of bipolar plate materials.

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