Direct numerical simulation of droplet deformation in turbulent flows with different velocity profiles

Jiao, Daokuan; Jiao, Kui; Zhang, Fan; Du, Qing

doi:10.1016/j.fuel.2019.03.010

Cited by 33 publications

(19 citation statements)

References 24 publications

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“…It can be noticed that the condensation prefers to occur on the fiber surfaces, especially at the locations where fibers cross and overlap, as presented in Figure 4 ( t = 1 ms). This is also consistent with the experimental observation 38 . Since constant wall temperature boundary condition was applied on the fiber, of which the temperature was lower than the vapor intake.…”

Section: Resultssupporting

confidence: 91%

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Vapor condensation in reconstructed gas diffusion layers of proton exchange membrane fuel cell

Jiao

2020

Int J Energy Res

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Summary In the present study, water is considered to be in vapor state when intruding the gas diffusion layers (GDL) of proton exchange membrane fuel cell (PEMFC). A phase change solver was developed in OpenFOAM platform and validated to model the vapor condensation processes in reconstructed GDL. The stochastic method was adopted to reconstruct the 3D GDL while the vapor/condensate water two‐phase flow problem was solved by employing the volume of fluids (VOF) method. Vapor condensation processes in GDL with/without rib were compared under different current densities and ambient temperatures. The temporal varying condensate droplets’ distributions were displayed and the droplets evolution processes were summarized. Vapor condensation processes can be divided into several stages, including small water‐droplets generation, droplets growth, coalescence, accumulation, and condensate water removal. It was found that the condensate water distribution under the rib was entirely different from that under the channel. Water saturation in GDL without rib was lower at the same current density and same ambient temperature. In addition, the vapor condensation was highly sensitive to the local temperature. Growth of the temporal liquid water saturation presented remarkable difference when local temperature varied. The condensate water breakthrough paths were identified. The cyclic release of condensate water droplets into the channel activated the water saturation fluctuations. Water saturation fluctuated wildly in the GDL with rib along the thickness direction, due to the role of rib in impeding the removal of water. Besides, it was noticed that the rib was not beneficial for oxygen diffusion apart from hindering the condensate water transport. A phase change solver was developed in OpenFOAM platform and validated to model the vapor condensation in a realistic structural GDL. The temporal varying condensate droplets’ distributions were displayed and the droplets evolution processes were summarized. The rib was not beneficial for the oxygen diffusion apart from hindering the condensate water transport, which increases the risks of water flooding.

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Section: Resultssupporting

confidence: 91%

“…The results are depicted in Figure 2B and show good agreements with analytical solutions. In addition, the morphologies of the vapor condensation process, in this study, are compared with the environmental scanning electron microscope (ESEM) micrographs, 38 and it presents similar patterns.…”

Section: Resultsmentioning

confidence: 93%

Vapor condensation in reconstructed gas diffusion layers of proton exchange membrane fuel cell

Jiao

2020

Int J Energy Res

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“…The two-phase solver "interFoam" for immiscible and incompressible fluids is employed to solve the governing equations while tracking the water-gas interface. The robustness of the solver has been extensively validated in previous studies 4,6,25,[29][30][31] under various conditions, including water transport in GDL. In the present, the porosities of the reconstructed GDL vary through the plane.…”

Section: Numerical Validationmentioning

confidence: 99%

Water transport in the gas diffusion layer of proton exchange membrane fuel cell under vibration conditions

Jiao

Niu

et al. 2020

Int J Energy Res

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Summary Fuel cell vehicles face complicated road conditions, which may impact on the output performance of fuel cell stacks. In the present study, the water transport in the gas diffusion layer (GDL) of proton exchange membrane fuel cell (PEMFC) under vibration conditions are investigated. A stochastic method is employed to reconstruct the 3‐D GDL with experimentally validated varying porosities. The volume of fluid (VOF) method is adopted to investigate the two‐phase problems. Sinusoidal vibration source terms are superposed, which can vary with required amplitudes and directions. Over time, the water transport process takes three steps: water intrusion, water accumulation, and water removal. The water intrusion tends to start from the sides of the GDL, then spreads into the central area. Compared with the no‐vibration case, the water saturations are higher in both the vertical and horizontal vibration cases. The vibration will enhance the water transport through GDL layers. As such, the higher the vibration amplitude and frequency, the larger the water saturation. Accordingly, the water saturation of the GDL vary sinusoidally over time. The water breakthrough paths are identified and compared during the water removal processes. Vibration in the horizontal direction is much easier to promote the water transport inside a layer compared with vibration in the vertical direction. More substantial water saturation in the GDL layers will restrict the gas transfer paths. Consequently, less oxygen will participate in the reaction, which will further impact on the fuel cell performance.

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“…As can be seen, the viscosity and density of vegetable fuels have higher values than conventional fuel, therefore, according to the authors, the use of spiral-elliptical ducts on the non-working part of the needle will affect the physical parameters of the fuel and improve the atomization process in the combustion chamber of the compression ignition engine. One of the features of turbulent flows is the fluctuation of momentum and kinetic energy of turbulence Hinze [23], and the phenomenon of heat exchange during flow Elsner [24], Jiao [25]. The viscosity and density of liquids depending on the temperature.…”

Section: Presentation Of the Modifications Made To The Fuel Injector mentioning

confidence: 99%

Model Issues Regarding Modification of Fuel Injector Components to Improve the Injection Parameters of a Modern Compression Ignition Engine Powered by Biofuel

et al. 2019

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This article presents a theoretical analysis of the use of spiral-elliptical ducts in the atomizer of a modern fuel injector. The parameters of the injected fuel stream can be divided into quantitative and qualitative. The quantitative parameter is the injection dose amount, and the qualitative parameter is characterized by the stream of injected fuel (width, atomization, opening angle, and range). The purpose of atomizer modification is to cause additional flow turbulence, which may affect the stream parameters and improve the combustion process of the combustible mixture in a diesel engine. The spiral-elliptical ducts discussed here could be used in engines powered by vegetable fuels. The stream of such fuels has worse quality parameters than conventional fuels, due to their higher viscosity and density. The proposal to use spiral-elliptical ducts is an innovative idea for diesel engines.

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Direct numerical simulation of droplet deformation in turbulent flows with different velocity profiles

Cited by 33 publications

References 24 publications

Vapor condensation in reconstructed gas diffusion layers of proton exchange membrane fuel cell

Vapor condensation in reconstructed gas diffusion layers of proton exchange membrane fuel cell

Water transport in the gas diffusion layer of proton exchange membrane fuel cell under vibration conditions

Model Issues Regarding Modification of Fuel Injector Components to Improve the Injection Parameters of a Modern Compression Ignition Engine Powered by Biofuel

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