本研究使用自行設計的雙層氣衝預成液膜噴注器，應用高速攝影和粒徑量測分析液膜破碎霧化機制。實驗之液體(水)質量流率約為1 g/s和空氣速度10.8 m/s至36.4 m/s，分別針對雙層等速氣流和雙層速度差兩種條件進行實驗觀察。結果顯示在雙層等速空氣流速條件下，隨著空氣流速的提升，液體韌帶擺動逐漸劇烈，在空氣流速為10.8 m/s~18.3 m/s時會以非軸對稱瑞利破碎(Nonaxisymmetric Rayleigh-Type Breakup)的方式破碎；在空氣流速24.2 m/s~36.4 m/s時則會以膜式破碎(Membrane-Type Breakup)的方式進行破碎；前者所破碎出的液滴相較於後者相對大；粒徑分佈多以高斯分布呈現；隨流速增加，平均粒徑隨之降低，破碎長度及霧化角亦隨著空氣流速增加而增加。在雙層空氣速度差的條件下，以固定上層空氣流速及固定下層空氣流速的方式進行實驗。實驗結果顯示，速度差對液體表面產生影響，使得不穩定性增加，降低單層空氣流速會使得液膜破碎距離縮短。實驗亦顯示噴霧現象會朝速度較低的一側進行偏折，且改變粒徑分布狀態；在高速區量測到的粒徑較小、低流速區域量測到的平均粒徑較大，全噴霧平均粒徑變大。綜上所述，本研究利用自行設計的雙層氣衝預成液膜噴注器，透過實驗觀察，深入探討了不同實驗參數對於液體霧化特性的影響。這些研究結果對於理解和改進噴霧系統的性能具有重要的意義。
關鍵字：預成膜氣衝式噴注器、破碎長度、霧化角、粒徑量測

This study employs a self-designed dual-layer gas flow channel pre-film air assisted atomizer to investigate the liquid atomization characteristics using precision instruments. Solidworks Flow Simulation is utilized to simulate flow patterns and velocity distribution, and particle size measurement instruments along with high speed imaging are employed to observe spray phenomena under various experimental parameters. In experiments conducted under uniform air velocity conditions, an increase in air velocity leads to a change in the droplet breakup mechanism, affecting breakup length and angle. Under velocity differential conditions, the liquid surface instability is affected, and velocity differentials improve energy efficiency while also influencing droplet distribution and breakup direction. In summary, this research comprehensively explores the impact of different parameters of the dual-layer gas flow channel pre-film air-assisted atomizer on liquid atomization. The findings hold crucial significance for enhancing the understanding and performance of spray systems.
Keywords：prefilming airblast injector, breakup length, atomization angle,
spray measurement

[1]A. Lefebvre, V. McDonell, “Atomization and Sprays,”Taylor and Francis, London, 1989.
[2]A. Lefebvre, “Properties of Sprays,” Part. Part. Syst. Charact. 6, 1989, 176-186.
[3]X. Zhou, M. Liu, B. Dong, W. Li, K. Liang, “Effects of prefilmer edge configuration on primary liquid film breakup: A lattice Boltzmann study,” Computers and Mathematics with Applications, 146, 2023, 33-44.
[4]S. Gepperth, D. Guildenbecher, R. Koch, and H.-J. Bauer,“Prefilming primary atomization: Experiments and modeling,” 23rd Annual Conference on Liquid Atomization and Spray Systems, Brno, Czech Republic, 2010, 76131.
[5] X. Zhou, B. Dong, W. Li, K. Liang, “Lattice Boltzmann modeling of primary liquid film breakup at the prefilmer edge: Effects of surface wettability,” Computers and Mathematics with Applications, 109, 2022, 146-157.
[6] X. Zhou, B. Dong, W. Li, “Phase-field-based LBM analysis of KHI and RTI in wide ranges of density ratio,” viscosity ratio, and Reynolds number, Int. J. Aerosp. Eng. 2020, 2020, 8885226.
[7]S. Gepperth, A. Müller, R. Koch1 and H.-J. Bauer,“Ligament and Droplet Characteristics in Prefilming Airblast Atomization,”12th Triennial International Conference on Liquid Atomization and Spray Systems, Heidelberg, Germany, 2012, 2-6.
[8]T. Inamura, N. Katagata, H. Nishikawa, T. Okabe, K. Fumoto, “Effects
of prefilmer edge thickness on spray characteristics in prefilming airblast atomization,” International Journal of Multiphase Flow, 121, 2019, 103117.
[9]T. Sattelmayer, S. Wittig, “Internal flow effects in prefilming airblast atomizers: mechanisms of atomization and droplet spectra,”J. Eng. GasTurbines Power 108, 1986, 465–472.
[10] András Urbán, Matouš Zaremba, Milan Malý, Viktor Józsaa,Jan Jedelský “Droplet dynamics and size characterization of high-velocity airblast atomization,” International Journal of Multiphase Flow, 95, 2017, 1-11.
[11]M. Aigner, S. Wittig,“Swirl and counterswirl effects in prefilming airblast atomizers,”J. Eng. Gas Turbines Power 110, 1988, 105–110.
[12]M. El-Shanawany, A. Lefebvre, “Airblast atomization: effect of linear scale on mean drop size,” J. Energy 4, 1980, 184–189.
[13]N. Rizk, A. Lefebvre, “Influence of atomizer design features on mean drop size,” AIAA J. 21, 1983, 1139–1142.
[14]S. Gepperth, R. Koch, H. Bauer, “Analysis and comparison of primary droplet characteristics in the near field of a prefilming airblast atomizer,” in: ASME Turbo Expo: Turbine Technical Conference and Exposition, San Antonio, Texas, USA, June 2013.
[15] E. Bärow, S. Gepperth, R. Koch, H. Bauer, “Effect of the precessing vortex core on primary atomization,” Z. Phys. Chem. 229, 2015, 909–929.
[16]G. Chaussonnet, S. Gepperth, S. Holz, R. Koch, H.J. Bauer,“Influence
of the ambient pressure on the liquid accumulation and on the primary spray in prefilming airblast atomization,” International Journal of Multiphase Flow,125,2020, 103229.
[17]R. Koch, S. Braun, L. Wieth, G. Chaussonnet, T. Dauch, H.-J. Bauer, “Prediction of primary atomization using Smoothed Particle Hydrodynamics,” European Journal of Mechanics - B/Fluids, 61, 2017, 271-278.
[18]B. Déjean, P. Berthoumieu, P. Gajan, “Experimental study on the influence of liquid and air boundary conditions on a planar air-blasted liquid sheet,part I: liquid and air thicknesses,” Int. J. Multiph. Flow 79,2016, 202–213.
[19]B. Déjean, P. Berthoumieu, P. Gajan, “Experimental study on the influence of liquid and air boundary conditions on a planar air-blasted liquid sheet, part II: prefilming zone length,” Int. J. Multiph. Flow 79, 2016, 214–224.
[20]Norman Chigier, Rolf D. Reitz, “Regimes of Jet Breakup and Breakup Mechanisms,” AIAA, 1995.
[21]S. Braun, L. Wieth, S. Holz, T.F. Dauch, M.C. Keller, G. Chaussonnet, S. Gepperth, R. Koch, H.-J. Bauer, “Numerical prediction of air-assisted primary atomization using Smoothed Particle Hydrodynamics,” International Journal of Multiphase Flow, 114, 2019, 303-315.