Electrohydrodynamic simulation of electrically controlled droplet generation

Ouédraogo, Yun; Gjonaj, Erion; Weiland, Thomas; Gersem, Herbert De; Steinhausen, Christoph; Lamanna, Grazia; Preusche, Andreas; Dreizler, Andreas; Schremb, Markus

doi:10.1016/j.ijheatfluidflow.2017.02.007

Cited by 33 publications

(8 citation statements)

References 19 publications

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“…Moreover, in several previous studies, this model was used to simulate the deformation of a drop within a specified electric field strength [11][12][13][14] and the well-known oblate and prolate deformations and conditions under which these deformations were reached were thoroughly discussed. Due to its ability to exert tangential force on the fluid interface, the leaky dielectric model has been utilized for cone-jet simulation [15][16][17][18] and electrically controlled droplet generation 19 .…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of jet mode in electrospraying of Newtonian and viscoelastic fluids

Panahi

Pishevar

Tavakoli

2020

International Journal of Multiphase Flow

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The purpose of this article is to explore the role of viscoelastic properties of polymeric solutions on the jet mode in the electrospray process. In this research, several numerical simulations were performed to model the behavior of electrified Newtonian and viscoelastic jets. First, used for validating viscoelastic constitutive equations and their implementation, the benchmark problem of the sedimenting sphere is stabilized beyond the previously suggested threshold. Then, an electrified DI water jet was simulated, and the obtained jet profile was compared with the experimental data from previous publications. Finally, the proposed algorithm was used to simulate viscoelastic electrified jets, where the effect of the Weissenberg number (Wi) on the jet profile was examined. In agreement with the previously obtained experimental results, by increasing the solution concentration, the asymptotic profile of the jet is reached at a smaller length from the nozzle, while the final thickness of the jet is slightly reduced.

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Section: Introductionmentioning

confidence: 99%

Numerical simulation of jet mode in electrospraying of Newtonian and viscoelastic fluids

Panahi

Pishevar

Tavakoli

2020

International Journal of Multiphase Flow

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“…For example, it can yield quasi-monodisperse droplets, control the droplet motion easily and avoid coalescence of droplets 1 . It has been applied in many areas such as fuel atomization in combustion systems 2,3 , controlled droplet generation 4,5 , electrospinning 6,7 , thin film deposition 8,9 and electrospray ionization-mass spectrometry applications 10,11 . Meanwhile more and more attention has been focused on the micro-power systems using micro-scale combustors due to the higher specific energy of liquid hydrocarbons than that of batteries 12,13 .…”

Section: Introductionmentioning

confidence: 99%

A comparative study on droplet characteristics and specific charge of ethanol in two small-scale electrospray systems

Gan

Jiang

et al. 2019

Sci Rep

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An investigation on the droplet characteristics of ethanol in small-scale combustors with two different systems was conducted experimentally and theoretically. The classical capillary-mesh electrode arrangement was applied in Type A electrospray system, and for Type B, an additional ring electrode is included. The droplet size and velocity were measured by a Phase Doppler Anemometer. The electric filed intensity was theoretically calculated in the two electrospray systems. Compared with Type A, Type B system has smaller droplet size and velocity in the same spraying mode. Meanwhile the electrospray process in Type B system is more stable than that in Type A with its smaller root mean square velocity. By measuring the spraying current, the average specific charge of the droplets for the two systems was obtained in different spraying modes. And it was found that the addition of the ring electrode can help to increase the droplet charge, which is the fundamental reason for Type B electrospray system to perform better. The corona charge of the droplets was theoretically calculated for the two electrospray systems. It was found that the calculated specific charge generated by corona charging was in good agreement with the experimental results.

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“…A detailed description of the droplet generator can be found in Weckenmann et al [6] and Oldenhof et al [7]. A analytical and numerical framework of the detachment process was done by Ouedraogo et al [8]. For further information about the experimental setup the reader is referred to Bork et al [9], Weckenmann et al [6] and Oldenhof et al [7].…”

Section: Methodsmentioning

confidence: 99%

Experimental Investigation of Droplet Injections in the Vicinity of the Critical Point: A comparison of different model approaches

Steinhausen

Lamanna

Stierle

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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The disintegration process of liquid fuel within combustion chambers is one of the most important parameters for efficient and stable combustion. Especially for high pressures exceeding the critical value of the injected fluids the mixing processes are not fully understood yet. Recently, different theoretical macroscopic models have been introduced to understand breakdown of the classical two phase regime and predict the transition from evaporation to a diffuse-mixing process. In order to gain deeper insight into the physical processes of this transition, a parametric study of free-falling n-pentane droplets in an inert nitrogen atmosphere is presented. Atmospheric conditions varied systematically from sub-to supercritical values with respect to the fluid properties. An overlay of a diffuse lighted image with a shadowgram directly in the optical setup (front lighted shadowgraphy) was applied to simultaneously detect the presence of a material surface of the droplet as well as changes in density gradients in the surrounding atmosphere. The experimental investigation illustrates, that the presence of a material surface cannot be shown by a direct shadowgram. However, reflections and refractions caused by diffuse ambient illumination are able to indicate the presence of a material surface. In case of the supercritical droplet injections in this study, front lighted shadowgraphy clearly revealed the presence of a material surface, even when the pre-heated droplets are released into a supercritical atmosphere. This detection of the droplet interface indicates, that the droplet remains subcritical in the region of interest, even though it is injected into a supercritical atmosphere. Based on the adiabatic mixing assumption recent Raman-scattering results in the wake of the droplet are re-evaluated to compute the temperature distribution. Presented experimental findings as well as the re-evaluation of recent Raman scattering results are compared to thermodynamic models to predict the onset of diffuse-mixing and supercritical disintegration of the droplet. Additionally, a one dimensional evaporation model is used to evaluate the validity of the adiabatic mixing assumption in the estimation of the droplet temperature. The presented findings contribute to the understanding of recent theoretical models for prediction of spray and droplet disintegration and the onset of diffuse-mixing processes. Keywords Front lighted Shadowgraphy, Raman-scattering, Supercritical fluid injection IntroductionThe disintegration process of liquid droplets in a high pressure and high temperature environment is one of the most important parameters for stable and efficient combustion. Therefore, the behaviour of droplets in such an environment has long been a matter of analytical, numerical and experimental investigation. Especially the transition process from a two phase behaviour of the droplet or jet to a diffusion dominated mixture is not yet well understood. Recently, three different models predicting the onset of this diffuse-mixing...

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Electrohydrodynamic simulation of electrically controlled droplet generation

Cited by 33 publications

References 19 publications

Numerical simulation of jet mode in electrospraying of Newtonian and viscoelastic fluids

Numerical simulation of jet mode in electrospraying of Newtonian and viscoelastic fluids

A comparative study on droplet characteristics and specific charge of ethanol in two small-scale electrospray systems

Experimental Investigation of Droplet Injections in the Vicinity of the Critical Point: A comparison of different model approaches

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