本研究利用MALVERN粒徑量測儀配合由PLIF (Planar Laser Induced Fluorescence)量測技術獲得之質量分布資料，分析完全發展模式下雙衝擊式噴霧之液滴粒徑分布。改變衝擊角(60~90)、噴流流速(28.6m/s57.3m/s)、表面張力(44.0 mN/m71.8 mN/m)、黏滯係數(0.89×10-3 Ns/m2~1.89×10-3 Ns/m2)、孔口直徑(0.3mm and 0.4mm)以配合液滴破碎之研究探討雙衝擊式噴霧之霧化機制，並透過改變環境壓力以了解對噴流之空氣動力不穩定性的影響。本研究分析離噴霧軸較近區域之一固定比例之液滴粒徑，並於不同截面進行量測。實驗結果顯示：液滴粒徑皆由衝擊點沿噴霧軸開始減小，然而，液滴越往下遊移動因其We越接近〖We〗_crit，至一特定位置後其粒徑減小趨勢減緩達到一近平衡狀態。除此之外，當噴流流速增加時，所觀察到之液滴粒徑皆變小。使用表面張力較小之溶液進行衝擊，在近衝擊點區域產生較小之液滴顆粒，然而，使用較高黏滯係數之溶液，在近衝擊點區域產生略大之液滴顆粒。實驗結果同時也顯示在近衝擊點區域液滴因二次碰撞而產生的融合現象會導致液滴變小的趨勢減緩。在噴霧的下游區域，噴流流速與表面張力對於液滴粒徑大小有顯著影響。然而，黏滯係數對於液滴粒徑分布之影響較不明顯。除此之外，本研究亦對於噴流之垂直與水平動量通量之改變進行分析，實驗結果顯示噴流之水平動量通量的增加使近衝擊點區域之液滴粒徑減小，而對於下游區域之粒徑分布影響較小，然而，噴流之垂直動量通量對於液滴沿噴霧軸之分布變化有完全相反之影響。

In this research, the droplet size distributions in fully-developed like-doublet impinging sprays were analyzed by Malvern in conjunction with the mass distribution information from planar laser induced fluorescence (PLIF) observations. The orifice size (0.3mm and 0.4mm), impinging angle(60 and 90), jet velocity (28.6m/s57.3m/s), surface tension (44.0 mN/m71.8 mN/m), viscosity(0.89 10-3 Ns/m2~1.89 10-3 Ns/m2), and ambient pressure were varied to investigate their effects on droplet size. The droplet sizes of fixed fractions of the liquid mass near the center region of the sprays were adopted for comparison. In each observation condition, the droplet sizes decreased with increasing downstream distance to a semi-stable value, and the observed droplet sizes decreased with increasing jet velocities and decreasing surface tension of the liquid. A higher viscosity liquid produced slightly larger droplets in the near-impinging point region for jet’s lower hydrodynamic instability, however, is insignificant to the observed droplet size variations at the semi-stable conditions. The experiment results also showed that the coalescence of droplets by secondary collision slowed down the decrease of the droplet sizes in the near-impinging point region. In addition, increasing the horizontal momentum flux of the impinging jets decreased the droplet sizes in near-impinging point region but showed no effect on that in the downstream region, however, increasing the vertical momentum flux of the jets showed no effect on droplet sizes in near-impinging point region but significantly decreased the downstream droplet sizes.
 

1. Lefebvre, A. H., “Fuel Effects on Gas Turbine Combustion－Ignition, Stability, and Combustion Efficiency”, ASME J. Eng. Gas Turbines Power, Vol. 107, pp. 24-37, 1985.
2. Reeves, C. M., and Lefebvre, A. H., “Fuel Effects on Aircraft Combustor Emissions”, ASME Paper 86-GT-212, 1986.
3. Rink, K. K., and Lefebvre, A. H., “Influence of Fuel Drop Size and Combustor Operating Conditions on Pollutant Emissions”, SAE Technical Paper 861541, 1986.
4. Heidmann, M. F., and R.J.Priem, ”A Study of Sprays Formed by Two Impinging Jets”, NACA-TN-3835, March 1957
5. Heidmann, M. F., and Humphrey, J. C., “Fluctuations in a Spray Formed by Two Impining Jets”, NACA-TN-2349, March, 1951
6. Dombrowski, N. and Hopper,P.G., “The Effect of Ambient Density on Drop Formation in Sprays”, Chemical Engineering Science, Vol. 17, pp. 291-305, 1962.
7. Dombrowski, N. and Johns, W. R. “The Aerodynamics Instability and Disintegration of Viscous Liquid Sheets”, Chemical Engineering Science, Vol. 18, pp. 203-214, 1963.
8. Dombrowski, N. and Hopper, P. G. “A Study if the Sprays Formed by Impinging Jets in Laminar and Turbulent Flow”, Journal of Fluid Mechanics, Vol. 18, part 3, pp.392-400, 1964.
9. 江滄柳、賴維祥、黃文榮，同質衝擊噴流特性之研究，成功大學航太所博士論文，八十六學年度
10. Kang, B. S. and Poulikakos, D. ”Holography Experiments in a Dense High-Speed Impinging Jet Spray”, Journal of Propulsion And Power,1996.
11. Vassallo, P., Ashgriz, N., and Boorady, F. A., “Effect of Flow Rate on the Spray Characteristics of Impinging Water Jets”, Journal of Propulsion and Power, Vol. 8, No. 5, Sep-Oct, pp. 980-986, 1992.
12. O’Rourke, P., and Bracco, F., “Modeling of Drop Interactions in Thick Sprays and a Comparison with experiments”, Proceedings of the Institution of Mechanical Engineers, Vol. 9, pp. 101-106, 1980.
13. Ashgriz, N., and Poo, J. Y., “Coalescence and Separation in Binary Collisions of Liquid Drops”, J. Fluid Mech., Vol. 221, pp. 183-204, 1990.
14. Jiang, Y. J., Umemura, A. and Law, C.K., “An Experimental Investigation on the Collision Behaviour of Hydrocarbon Droplet”, Journal of Fluid Mechanics, Vol. 234, pp. 171-190, 1992.
15. Qian, J., Law, C.K., “Regimes of Coalescence and Separation in Droplet Collision”, Journal of Fluid Mechanics, Vol. 331, pp. 59-80, 1997.
16. Hochschwender, E., Ph.D. thesis, University of Heidelberg, 1949.
17. Hinze, J. O., “Fundamentals of the Hydrodynamic Mechanism of Splitting in Dispersion Process”, AIChE J. 1, No. 3,1955 pp. 289-295, 1955.
18. Hanson, A. R., Domich, E. G., and Adams, H. S., “Shock Tube Investigation of the breakup of Drops by Air Blasts”, Phys. Fluids, Vol. 6, pp. 1070-1080,1963.
19. Eckbreth, A. C., Laser Diagnostics for Combustion Temperature and Species, Gordon and Breach Publisher, 1996.
20. Russ, J. C. ,The Image Processing Handbook, CRC Press, 1992.
21. Chen, W.C., “The Analysis on the Breakup and Mixing of the Impinging Jets”, Ph, D Dissertation, National Cheng Kung University, Taiwan, 2007.
22. 黃柏霖,”5-lbf NTO/MMH 火箭推進劑衝擊霧化模擬之PLIF實驗觀察”,成功大學航太所碩士論文，中華民國九十四年
23. 鍾易全、袁曉峰，衝擊噴流之混合現象觀察，成功大學航太所碩士論文，九十二學年度。
24. Lefebvre, A. H., Atomization and Sprays, Hemisphere Publishing Corporation, pp. 30-37, 1989.