實際航空燃油引擎的噴射系統十分複雜，為實現良好的油氣混合及增加燃油停留時間，航空引擎將燃油噴嘴及空氣旋流器結合在一起，但由於噴嘴結構複雜內部流場觀察不易及添加旋流空氣後燃油液體與周圍空氣之間相互作用改變，本研究以數值方法針對是否添加旋流空氣對冷噴霧噴霧內部流動機制與外部噴霧行為的改變，分析加裝空氣旋流器後壓力噴嘴內外流場之影響，並使用自適應網格(Adaptive mesh refinement, AMR)及尤拉-尤拉描述法(Eulerian–Eulerian method)轉換尤拉-拉格朗日描述法(Eulerian–Lagrangian method)節省網格數量，以VOF場先行觀察噴霧初級破裂情形，後續符合轉換條件之液滴轉換拉格朗日粒子以進行液滴統計及分析，以模擬了解流動細節增強旋流空氣對噴霧交互作用的理解。
從模擬中發現噴嘴內液體旋轉室流體並非單純向下排出噴嘴，頂壁流流至徑向中心後為填補空氣錐周圍液體而快速下降，空氣錐表面波動使液體不穩定進而產生非單純向下流出的小渦流。噴霧外流場的部分，當空氣旋流器旋流數大於 0.6 時，出口場形成再循環區造成噴霧角擴大，對噴霧破裂的狀態及粒徑分布亦有影響，與無添加旋流空氣相比，有旋流空氣的噴霧液滴分布平均且粒徑更為細小。

The injection system of actual aviation fuel engines is highly complex. To achieve good fuel-air mixing and increase fuel residence time, aviation engines combine fuel injectior with air swirlers. However, due to the complex structure of the injectiors, it is difficult to observe the internal flow field, and the interaction between the fuel liquid and the surrounding air changes when swirl air is added. This study uses numerical methods to analyze the impact of adding swirl air on the internal flow mechanisms and external spray behavior of cold spray. It examines the effects on the pressure injectior's internal and external flow fields when an air swirler is added. Adaptive mesh refinement (AMR) and the Eulerian-Eulerian method transitioning to the Eulerian-Lagrangian method are used to save the number of grids. The Volume of Fluid (VOF) field is first used to observe the primary breakup of the spray, and subsequent droplets meeting transition conditions are converted to Lagrangian particles for statistical analysis. This simulation helps understand the detailed flow interactions enhanced by swirl air in the spray.

The simulation reveals that the liquid in the rotating chamber of injectior does not simply flow downward. After the top wall flow reaches the radial center, it rapidly descends to fill the liquid around the air cone. The surface fluctuations of the air cone cause liquid instability, resulting in small vortices that do not simply flow downward. In the external flow field of the spray, when the swirl number of the air swirler exceeds 0.6, a recirculation zone forms at the outlet, causing the spray angle to widen, affecting the spray breakup and droplet size distribution. Compared to no swirl air, the spray with swirl air has a more uniform droplet distribution and smaller droplet size.

[1] P. W. Dong, Q. Chen, G. Q. Liu, B. W. Zhang, G. Yan, and R. X. Wang, "Effects of geometric parameters on flow and atomization characteristics of swirl nozzles for artificial snowmaking," International Journal of Refrigeration, vol. 154, pp. 56-65, Oct 2023, doi: 10.1016/j.ijrefrig.2023.07.015.
[2] Z. T. Kang, Z. G. Wang, Q. L. Li, and P. Cheng, "Review on pressure swirl injector in liquid rocket engine," Acta Astronautica, vol. 145, pp. 174-198, Apr 2018, doi: 10.1016/j.actaastro.2017.12.038.
[3] A. Tabeei, A. Samimi, and D. Mohebbi-Kalhori, "CFD modeling of an industrial scale two-fluid nozzle fluidized bed granulator," Chemical Engineering Research & Design, vol. 159, pp. 605-614, Jul 2020, doi: 10.1016/j.cherd.2020.05.020.
[4] S. Patil and S. Sahu, "Air swirl effect on spray characteristics and droplet dispersion in a twin-jet crossflow airblast injector," Physics of Fluids, vol. 33, no. 7, Jul 2021, Art no. 073314, doi: 10.1063/5.0054430.
[5] X. Y. Li, M. C. Soteriou, W. Kim, and J. M. Cohen, "High Fidelity Simulation of the Spray Generated by a Realistic Swirling Flow Injector," Journal of Engineering for Gas Turbines and Power-Transactions of the Asme, vol. 136, no. 7, Jul 2014, Art no. 071503, doi: 10.1115/1.4026531.
[6] C. Cao et al., "Numerical Investigation on Mechanism of Swirling Flow of the Prefilming Air-Blast Fuel Injector," Energies, vol. 16, no. 2, Jan 2023, Art no. 650, doi: 10.3390/en16020650.
[7] Q. P. Zhao et al., "Experimental investigation of flow field features and spark ignition process in a multi-swirl airblast injector," Fuel, vol. 306, Dec 2021, Art no. 121732, doi: 10.1016/j.fuel.2021.121732.
[8] S. Sharma, K. Ghate, T. Sundararajan, and S. Sahu, "Effects of air swirler geometry on air and spray droplet interactions in a spray chamber," Advances in Mechanical Engineering, vol. 11, no. 5, May 2019, Art no. 1687814019850978, doi: 10.1177/1687814019850978.
[9] B. Khandelwal, D. Lili, and V. Sethi, "Design and study on performance of axial swirler for annular combustor by changing different design parameters," Journal of the Energy Institute, vol. 87, no. 4, pp. 372-382, Nov 2014, doi: 10.1016/j.joei.2014.03.022.
[10] S. K. Soni, M. Bharti, Y. Biswal, and P. S. Kolhe, "Effect of Co- and Counterswirl Air on Swirl Airblast Atomization," Journal of Propulsion and Power, vol. 39, no. 3, pp. 426-437, May-Jun 2023, doi: 10.2514/1.B38806.
[11] G. Amini, "Liquid flow in a simplex swirl nozzle," International Journal of Multiphase Flow, vol. 79, pp. 225-235, Mar 2016, doi: 10.1016/j.ijmultiphaseflow.2015.09.004.
[12] A. Datta and S. K. Som, "Numerical prediction of air core diameter, coefficient of discharge and spray cone angle of a swirl spray pressure nozzle," International Journal of Heat and Fluid Flow, vol. 21, no. 4, pp. 412-419, Aug 2000, doi: 10.1016/s0142-727x(00)00003-5.
[13] S. Moon, E. Abo-Serie, and C. Bae, "Air flow and pressure inside a pressure-swirl spray and their effects on spray development," Experimental Thermal and Fluid Science, vol. 33, no. 2, pp. 222-231, Jan 2009, doi: 10.1016/j.expthermflusci.2008.08.005.
[14] M. A. B. Martinez and V. Gaukel, "Using Computation Fluid Dynamics to Determine Oil Droplet Breakup Parameters during Emulsion Atomization with Pressure Swirl Nozzles," Fluids, vol. 8, no. 10, Oct 2023, Art no. 277, doi: 10.3390/fluids8100277.
[15] P. Marmottant and E. Villermaux, "On spray formation," Journal of fluid mechanics, vol. 498, pp. 73-111, 2004.
[16] P. W. Wang, J. J. Zhou, B. J. Xu, C. Lu, Q. A. Meng, and H. Liu, "Bioinspired Anti-Plateau-Rayleigh-Instability on Dual Parallel Fibers," Advanced Materials, vol. 32, no. 45, Nov 2020, Art no. 2003453, doi: 10.1002/adma.202003453.
[17] J. Jedelsky, M. Maly, N. Pinto del Corral, G. Wigley, L. Janackova, and M. Jicha, "Air–liquid interactions in a pressure-swirl spray," Int. J. Heat Mass Transfer, vol. 121, pp. 788-804, 2018, doi: 10.1016/j.ijheatmasstransfer.2018.01.003.
[18] C. Dumouchel, "On the experimental investigation on primary atomization of liquid streams," Exp. Fluids, vol. 45, no. 3, pp. 371-422, 2008, doi: 10.1007/s00348-008-0526-0.
[19] A. H. Lefebvre and V. G. McDonell, Atomization and sprays. CRC press, 2017.
[20] W. V. Ohnesorge, "Die bildung von tropfen an düsen und die auflösung flüssiger strahlen," ZAMM‐Journal of Applied Mathematics and Mechanics/Zeitschrift für Angewandte Mathematik und Mechanik, vol. 16, no. 6, pp. 355-358, 1936.
[21] R. D. Reitz, Atomization and other breakup regimes of a liquid jet. Princeton University, 1978.
[22] L. P. Bayvel, Liquid atomization. Routledge, 2019.
[23] L.-P. Hsiang and G. M. Faeth, "Drop deformation and breakup due to shock wave and steady disturbances," International Journal of Multiphase Flow, vol. 21, no. 4, pp. 545-560, 1995.
[24] M. Pilch and C. Erdman, "Use of breakup time data and velocity history data to predict the maximum size of stable fragments for acceleration-induced breakup of a liquid drop," International journal of multiphase flow, vol. 13, no. 6, pp. 741-757, 1987.
[25] J. U. Brackbill, D. B. Kothe, and C. Zemach, "A continuum method for modeling surface tension," J. Comput. Phys., vol. 100, no. 2, pp. 335-354, 1992.
[26] C. W. Hirt and B. D. Nichols, "VOLUME OF FLUID (VOF) METHOD FOR THE DYNAMICS OF FREE BOUNDARIES," Journal of Computational Physics, vol. 39, no. 1, pp. 201-225, 1981, doi: 10.1016/0021-9991(81)90145-5.
[27] H. G. Weller, G. Tabor, H. Jasak, and C. Fureby, "A tensorial approach to computational continuum mechanics using object-oriented techniques," Computers in Physics, vol. 12, no. 6, pp. 620-631, Nov-Dec 1998, doi: 10.1063/1.168744.
[28] J. Roenby, H. Bredmose, and H. Jasak, "A computational method for sharp interface advection," Royal Society Open Science, vol. 3, no. 11, Nov 2016, Art no. 160405, doi: 10.1098/rsos.160405.
[29] K. Inagaki and H. Kobayashi, "Transport and modeling of subgrid-scale turbulent kinetic energy in channel flows," AIP Advances, vol. 12, no. 4, 2022.
[30] Z. Wang, L. Li, H. Cheng, and B. Ji, "Numerical investigation of unsteady cloud cavitating flow around the Clark-Y hydrofoil with adaptive mesh refinement using OpenFOAM," Ocean Engineering, vol. 206, p. 107349, 2020.
[31] M. Heinrich and R. Schwarze, "3D-coupling of Volume-of-Fluid and Lagrangian particle tracking for spray atomization simulation in OpenFOAM," Softwarex, vol. 11, Jan-Jun 2020, Art no. 100483, doi: 10.1016/j.softx.2020.100483.
[32] A. Omidvar, "Development and assessment of an improved droplet breakup model for numerical simulation of spray in a turbulent flow field," Applied Thermal Engineering, vol. 156, pp. 432-443, Jun 2019, doi: 10.1016/j.applthermaleng.2019.04.090.
[33] 陳昱嘉, "硝酸羥胺基凝膠推進劑製備、線燃速及噴霧特性解析," 碩士, 機械工程學系, 國立成功大學, 台南市, 2024. [Online]. Available: https://hdl.handle.net/11296/ngvc29
[34] A. K. Gupta, D. G. Lilley, and N. Syred, "Swirl flows," Tunbridge Wells, 1984.
[35] V. Anisiuba, H. B. Ma, A. Silaen, and C. Zhou, "Computational Studies of Air-Mist Spray Cooling in Continuous Casting," Energies, vol. 14, no. 21, Nov 2021, Art no. 7339, doi: 10.3390/en14217339.