Formation of mono-dispersed droplets with electric periodic dripping regime in electrohydrodynamic (EHD) atomization

doi:10.1016/j.cjche.2020.03.008

摘要/Abstract

摘要： The formation of controllable size and dripping frequency in electrohydrodynamic (EHD) atomization with electric periodic dripping regime are of much interest and importance because of significant and wide applications, such as micro-encapsulation and ink-printing. In the present study, the experimental and theoretical works were carried out to explore droplet formation in periodic dripping regime in presence of an electric field. The dimensionless electric charge carried by each droplet produced is smaller than the 50% of critical value of the Rayleigh limit, where charge-to-mass ratio of droplets was obtained through the deflection distance in the presence of an electric field. The droplet in electric periodic dripping regime usually undergoes oscillating deformation, and finally forms a spherical droplet below the tip no more than ten times out diameter of tube. The droplet size tens of microns to one hundreds of microns decreases with an increase in applied potential. In the electric dripping mode, droplets size is independent of flow rate and affected by flow rate due to adsorption of surface active species in micro-dripping. The simplified model to predict droplets size was derived from the balance of electric, surface tension and gravity forces. The droplets size calculated in good agreement with the experiments. Meanwhile, the dripping frequency of droplets with rang of a few to several hundred hertz obtained from timeresolved images is highly dependent of liquid flow rate and electric potential. The largest dripping frequency was predicted and in reasonable agreement with the experimental results. In electric periodic dripping regime drop-on-demand droplets in size and dripping frequency further our understanding on the formation of identical droplets and are beneficial to many practical applications.

关键词: Electric field, Electric periodic dripping, Formation, Diameter, Dripping frequency

Abstract: The formation of controllable size and dripping frequency in electrohydrodynamic (EHD) atomization with electric periodic dripping regime are of much interest and importance because of significant and wide applications, such as micro-encapsulation and ink-printing. In the present study, the experimental and theoretical works were carried out to explore droplet formation in periodic dripping regime in presence of an electric field. The dimensionless electric charge carried by each droplet produced is smaller than the 50% of critical value of the Rayleigh limit, where charge-to-mass ratio of droplets was obtained through the deflection distance in the presence of an electric field. The droplet in electric periodic dripping regime usually undergoes oscillating deformation, and finally forms a spherical droplet below the tip no more than ten times out diameter of tube. The droplet size tens of microns to one hundreds of microns decreases with an increase in applied potential. In the electric dripping mode, droplets size is independent of flow rate and affected by flow rate due to adsorption of surface active species in micro-dripping. The simplified model to predict droplets size was derived from the balance of electric, surface tension and gravity forces. The droplets size calculated in good agreement with the experiments. Meanwhile, the dripping frequency of droplets with rang of a few to several hundred hertz obtained from timeresolved images is highly dependent of liquid flow rate and electric potential. The largest dripping frequency was predicted and in reasonable agreement with the experimental results. In electric periodic dripping regime drop-on-demand droplets in size and dripping frequency further our understanding on the formation of identical droplets and are beneficial to many practical applications.

Key words: Electric field, Electric periodic dripping, Formation, Diameter, Dripping frequency

Zhentao Wang, Qisi Wang, Yaosheng Zhang, Yimin Jiang, Lei Xia. Formation of mono-dispersed droplets with electric periodic dripping regime in electrohydrodynamic (EHD) atomization[J]. 中国化学工程学报, 2020, 28(5): 1241-1249.

参考文献

[1] A.M. Gañán-Calvo, J.M. López-Herrera, M.A. Herrada, A. Ramos, J.M. Montanero, Review on the physics of electrospray:from electrokinetics to the operating conditions of single and coaxial Taylor cone-jets, and AC electrospray, J. Aerosol Sci. 125(2018) 32-56.
[2] M. Cloupeau, B. Prunet-Foch, Electrohydrodynamic spraying functioning modes:a critical review, J. Aerosol Sci. 25(1994) 1021-1036.
[3] A. Jaworek, A. Krupa, Classification of the modes of EHD spraying, J. Aerosol Sci. 30(1999) 873-893.
[4] J.M. Grace, J.C.M. Marijnisse, A review of liquid atomization by electrical means, J. Aerosol Sci. 26(6) (1994) 1005-1019.
[5] W. Zhang, J. Wang, B. Li, H. Liu, C. Mulbah, D. Wang, P. Yongphet, EHD effects on periodic bubble formation and coalescence in ethanol under non-uniform electric field, Chem. Eng. Sci. 215(2019) 115451.
[6] Z. Wang, Q. Wang, B. Li, Y. Zhang, J. Wang, J. Tu, An experimental investigation on cone-jet mode in electrohydrodynamic (EHD) atomization, Exp. Thermal Fluid Sci. 114(2020) 11054.
[7] D. Wang, J. Wang, X. Wang, Y. Huo, P. Yongphet, Experimental investigation on the deformation and breakup of charged droplets in dielectric liquid medium, Int. J. Multiphase Flow 114(2019) 39-49.
[8] Z. Wang, K. Dong, L. Tian, S. Zhan, X. Wang, J. Wang, J. Tu, Numerical analyses of sulfur dioxide transport by an atmospheric circulating drop, Atmos. Pollut. Res. 10(3) (2019) 759-767.
[9] X. Leng, Y. Jin, Z. He, Q. Wang, M. Li, W. Long, Effects of V-type intersecting hole on the internal and near field flow dynamics of pressure atomizer nozzles, Int. J. Therm. Sci. 130(2018) 183-191.
[10] S. Appah, W. Jia, M. Ou, P. Wang, E.A. Asante, Analysis of potential impaction and phytotoxicity of surfactant-plant surface interaction in pesticide application, Crop Prot. 127(2020) 104961.
[11] J. Rosell-Llompart, J. Grifoll, I.G. Loscertales, Electrosprays in the cone-jet mode:from Taylor cone formation to spray development, J. Aerosol Sci. 125(2018) 2-31.
[12] Y. Huo, J. Wang, Z. Zuo, Y. Fan, Visualization of the evolution of charged droplet formation and jet transition in electrostatic atomization, Phys. Fluids 27(11) (2015) 114105.
[13] S. Appah, P. Wang, C. Gong, M. Qu, W. Jia, Review of electrostatic system parameters, charged droplets characteristics and substrate impact behavior from pesticides spraying, Int. J. Agr. Biol. Eng. 12(2) (2019) 1-9.
[14] M. Cloupeau, B. Prunet-Foch, Electrostatic spraying of liquids:Main functioning modes, J. Electrost. 25(1990) 165-184.
[15] Z. Wang, L. Tian, L. Xia, J. Dong, J. Wang, J. Tu, Experimental study on repetition frequency of drop/jet movement in electro-spraying of deionized water, Aerosol Air Qual. Res. 13(2018) 301-313.
[16] A.J. Hijano, I.G. Loscertales, S.E. Ibáñez, F.J. Higuera, Periodic emission of droplets from an oscillating electrified meniscus of a low-viscosity, highly conductive liquid, Phys. Rev. E 91(2015), 013011.
[17] Z. Wang, Y. Zhang, R. Li, Q. Wang, J. Wang, An experimental study on drop formation from a capillary tube, J. Braz. Soc. Mech. Sci. Eng. 42(2) (2020) 110.
[18] M. Scalf, M.S. Westphall, L.M. Smith, Charge reduction electrospray mass spectrometry, Anal. Chem. 72(1) (2000) 52-60.
[19] E. Sasaki, F. Kurayama, J. Ida, T. Matsuyama, H. Yamamoto, Preparation of microcapsules by electrostatic atomization, J. Electrost. 66(2008) 312-318.
[20] D. Poncelet, R.J. Neufeld, M.F.A. Goosen, B. Burgarski, V. Babak, Formation of microgel beads by electric dispersion of polymer solutions, AIChE J. 45(9) (1999) 2018-2023.
[21] M.W. Lee, N.Y. Kim, S.S. Yoon, On pinchoff behavior of electrified droplets, J. Aerosol Sci. 57(2013) 114-124.
[22] M.W. Lee, D.K. Kang, N.Y. Kim, H.Y. Kim, S.C. James, S.S. Yoon, A study of ejection modes for pulsed-DC electrohydrodynamic inkjet printing, J. Aerosol Sci. 46(2012) 1-6.
[23] B. Li, K. Yu, J. Xu, Z. Wang, J. Wang, W. Zhang, D. Wang, H. Xu, Z. Sun, Z. Wang, The secondary drop formation of nanoparticle/surfactant-stabilized water droplets under non-uniform electric fields, Int. J. Multiphase Flow 125(2020) 103211.
[24] T. Keshavarz, G. Ramsden, P. Phillips, P. Mussenden, C. Bucke, Application of electric field for production of immobilized biocatalysts, Biotechnol. Tech. 6(5) (1992) 445-450.
[25] B. Bugarski, Q. Li, M.F.A. Goosen, D. Poncelet, R.J. Neufeld, G. Vunjak, Electrostatic droplet generation:Mechanism of polymer droplet formation, AIChE J. 40(6) (1994) 1026-1031.
[26] D. Poncelet, V.G. Babak, R.J. Neufeld, M.F.A. Goosen, B. Burgarski, Theory of electrostatic dispersion of polymer solutions in the production of microgel beads containing biocatalyst, Adv. Colloid Interf. Sci. 79(1999) 213-228.
[27] Z.Wang,J.Z.Wen,J.Wang,Q.Dong,PDPAinvestigationonanelectrostatically-assisted twin-fluid atomization flow, Advances in Mechanical Engineering 6(2014) 402747.
[28] J. Choi, Y.J. Kim, S. Lee, S.U. Son, H.S. Ko, Drop-on-demand printing of conductive ink by electrostatic field induced inkjet head, Appl. Phys. Lett. 93(2008) 193508.
[29] M. Singh, H.M. Haverinen, P. Dhagat, G.E. Jabbour, Inkjet printing-process and its applications, Adv. Mat. 22(2010) 673-685.
[30] M. Kuang, L. Wang, Y. Song, Controllable printing droplets for high-resolution patterns, Adv. Mat. 26(2014) 6950-6958.
[31] D.K. Kang, M.W. Lee, H.Y. Kim, S.C. James, S.S. Yoon, Electrohydrodynamic pulsedinkjet characteristics of various inks containing aluminum particles, J. Aerosol Sci. 42(2011) 621-630.
[32] J. Kim, H. Oh, S.S. Kim, Electrohydrodynamic drop-on-demand patterning in pulsed cone-jetmode at various frequencies, J. Aerosol Sci. 39(2008) 819-825.
[33] E. Sutanto, Y. Tan, M.S. Onses, B.T. Cunningham, A. Alleyne, Electrohydrodynamic jet printing of micro-optical devices, Manufacturing Letters 2(2014) 4-7.
[34] Z.P. Liu, L.L. Zhang, Y.Y. Yang, D. Wu, G. Jiang, D.G. Yu, Preparing composite nanoparticles for immediate drug release by modifying electrohydrodynamic interfaces during electrospraying, Powder Technol. 327(2018) 179-187.
[35] B. Li, Z. Wang, V. Vivacqua, M. Ghadiri, J. Wang, W. Zhang, D. Wang, Z. Sun, Z. Wang, Drop-interface electrocoalescence mode transition under a direct current electric field, Chem. Eng. Sci. 213(2020)(115360).
[36] Z. Wang, T. Guo, L. Tian, Q. Xu, S. Zhan, J. Tu, Numerical simulation on circulation flow and mass transfer inside atmospheric water drops, Appl. Therm. Eng. 118(2017) 765-772.
[37] J.G. Lee, H.J. Cho, N. Huh, C. Ko, W.C. Lee, Y.H. Jang, B.S. Lee, I.S. Kang, J.W. Choi, Electrohydrodynamic (EHD) dispensing of nanoliter DNA droplets for microarrays, Biosens. Bioelectron. 12(2006) 2240-2247.
[38] J. Abu-Ali, S.A. Barringer, Method for electrostatic atomization of emulsions in an EHD system, J. Electrost. 63(5) (2005) 361-369.
[39] B. Vonnegut, R.L. Neubauer, Production of monodisperse aerosol particles by electrical atomization, J. Colloid Sci. 7(1952) 616-622.
[40] A. Speranza, M. Ghadiri, M. Newman, L.S. Osseo, G. Ferrari, Electro-spraying of a highly conductive and viscous liquid, J. Electrost. 51(2001) 494-501.
[41] A. Speranza, M. Ghadiri, Effect of electrostatic field on dripping of highly conductive and viscous liquids, Powder Technol. 135-136(2003) 361-366.
[42] Y.J. Kim, H.S. Ko, S. Lee, S.U. Son, D. Jung, D. Byun, Numerical and experimental analysis of electrostatic ejection of liquid droplet, J. Korean Phys. Soc. 51(2007) S42-S46.
[43] S.H. Lee, X.H. Nguyen, H.S. Ko, Study on droplet formation with surface tension for electrohydrodynamic inkjet nozzle, J. Mech. Sci. Technol. 26(5) (2012) 1403-1408.
[44] Z. Wang, K. Dong, L. Tian, J. Wang, J. Tu, Numerical study on coalescence behavior of suspended drop pair in viscous liquid under uniform electric field, AIP Adv. 8(2018) (08215).
[45] Z. Wang, L. Xia, L. Tian, J. Wang, S. Zhan, Y. Huo, J. Tu, Natural periodicity of electrohydrodynamic spraying in ethanol, J. Aerosol Sci. 117(2018) 127-138.
[46] Z. Wang, L. Xia, S. Zhan, Experimental study on electrohydrodynamics (EHD) spraying of ethanol with double-capillary, Appl. Therm. Eng. 120(2017) 474-483.
[47] Z. Wang, R. Li, L. Tian, L. Xia, S. Zhan, J. Wang, J. Tu, Visualization of periodic emission of drops with micro-dripping mode in electrohydrodynamic (EHD) atomization, Exp. Thermal Fluid Sci. 105(2019) 307-315.
[48] S. Appah, W. Jia, M. Qu, P. Wang, C. Gong, Investigation of optimum applied voltage, liquid flow pressure, and spraying height for pesticide application by induction charging, Appl. Eng. Agric. 35(5) (2019) 795-804.
[49] A.R. Jones, K.C. Thong, The production of charged monodisperse fueldroplets by electrical dispersion, J. Phys. D. Appl. Phys. 4(1971) 1159.
[50] Z. Wang, A.M. Mitrašinović, Z. Wen, Investigation on electrostatical breakup of biooil droplets, Energies 5(2012) 4323-4339.
[51] Y. Huo, J. Wang, W. Mao, Z. Wang, Z. Zuo, Measurement and investigation on the deformation and air-assisted breakup of charged droplet, Flow Meas. Instrum. 27(2012) S92-S98.
[52] C. Pantano, A.M. Gañán-Calvo, A. Barrero, Zeroth-order, electrohydrostatic solution for electrospraying in cone-jet mode, J. Aerosol Sci. 25(6) (1994) 1076-1077.
[53] A.M. Gañán-Calvo, J.C. Lasheras, J. Dávila, A. Barrero, The electrostatic spray emitted from an electrified conical meniscus, J. Aerosol Sci. 25(6) (1994) 1121-1142.
[54] J. Zhang, H. He, G. Huang, Dynamic characteristics of charged droplets in an electrostatic sprayingprocess with twin capillaries, Chin. J. Chem. Eng. 26(2018) 2403-2411.
[55] S. Appah, H. Zhou, P. Wang, M. Ou, W. Jia, Charged monosized droplet behaviour and wetting ability on hydrophobic leaf surfaces depending on surfactant-pesticide concentrate formulation, J. Electrost. 100(2019) 103356.
[56] A.M. Ganan-Calvo, J.M. Montanero, Revision of capillary cone-jet physics:Electrospray and flow focusing, Phys. Rev. E 79(2009), 066305.