摘要
液態雙基火箭噴注器之燃料霧化和混合對推進器效能具重大影響，大型液態雙基推進器需使用高推進劑流率以產生足夠的推力，因增加噴注器孔口直徑可降低噴注器設計之複雜度，故本研究針對噴注器孔口直徑變化(0.25mm~0.50mm)對雙基噴流衝擊霧化與混合現象的影響進行實驗分析。本實驗固定單一噴流流速(30m/s)而改變另一股噴流流速(30m/s~50m/s)，在固定衝擊角(60°)下，應用PLIF技術觀察衝擊點下10mm處截面噴流質量機率分布，並使用非均勻度( )與混合效率( )等參數，量化分析不同口徑之噴流霧化與混合狀態；亦使用10%丙酮水溶液為工作流體探討流體表面張力對霧化與混合的影響。實驗結果顯示大孔徑噴流之空氣與流體動力不穩定性較低，故較不易霧化，其分布較小孔徑(0.25mm、0.30mm)噴流霧化分布之 值為高。結果亦顯示小孔徑之噴流在流速比1.16~1.33之間具較低的 值。且當流速比高於1.33時，高流速噴流集中穿透低流速噴流的現象漸趨明顯，使 值逐漸上升。 值分析顯示流速比為1時具最佳之 值，在不同流速下， 值均隨噴流孔徑增加而增高，分析流速比為1時噴流霧化後相互穿透量，顯示小孔徑衝擊霧化具過度穿透現象，增加孔徑會降低不穩定性，使噴流霧化效能減弱、相互穿透率降低，故具較高的(流速比1時) 值。丙酮水溶液衝擊霧化現象趨勢與純水衝擊霧化現象相似，但因丙酮具較低之表面張力，故其 值均較低（霧化較均勻）；且因丙酮水溶液已霧化相當完全，雖亦顯示具過度穿透現象，其 值對噴流孔徑變化之敏感度較純水為低。本論文結果顯示改變噴流孔徑對霧化及混合效應具強烈影響，應為設計大流率火箭噴注器之重要參數。

Abstract
Atomization and mixing of the propellants plays an important role in the thruster design. Injector plate design of multi-pair orifices is required for high propellant flow rate in high-thrust bipropellant engines. Since the increase of injector’s orifice diameter reduces the complexity of the design of injector plate, this thesis researched the atomization and mixing of impinging spray with the changes of injector’s orifice diameter (0.25mm~0.50mm). In the experiments, the sizes of the two impinging jets as well as the impinging angle were kept constants, while the jet velocity ratios were varied from 1.00 to 1.67. PLIF technique was adopted to observe the 2-dimensional probability distributions of mass for either and both liquids. The parameter of (Patternation Index) and mixing efficiency ( ) were used to quantify the degrees of atomization and mixing, respectively. Solution of 10% acetone in water as working fluid was utilized to discuss the surface tension effect on atomization and mixing. The experimental results revealed that the larger jets (0.5mm and 0.4mm) were comparatively more difficult to uniformly atomized (higher ) than that of the smaller jets (0.25mm and 0.3mm) since the hydrodynamic and aerodynamic instabilities were lower. Smaller were presented in the vicinity of velocity ratio 1.16~1.33 for all orifice sizes. In the velocity ratios of 1.36~1.67, the jet with higher velocity were shown concentrated and penetrated into the jet with lower velocity, which made the of the total spray to increase. In the analysis of , the largest is shown at the velocity ratio of 1 for the pair jets with different sizes and increased with the increasing pair orifice size at different velocity ratios. From the analysis of the quantity of penetration, the smaller sizes impingements showed over penetration at velocity ratio of 1. Since increasing of orifice diameter will degrade the instability of jet, the atomization and penetration of larger jets had less over penetration and showed higher . The 10% acetone solution jets atomized more uniform for its lower surface tension and brought down the total It also showed stronger over penetration, however, of the impingements of acetone solution is less sensitive to the changes of orifice diameters than that of pure water. This research revealed that the changes of orifice diameter possessed a strong effect on atomization and mixing of impinging jets and should be a crucial parameter in designing of rockets with large mass flow rate.

參考文獻
1. Schweitzer, P.H., Mechanism of Disintegration of Liquid Jets, J. Appl. Phys., Vol. 8, pp.513-521, 1937.
2. Nasser Ashgriz, William Brocklehurst, and Douglas Talley, ”Mixing Mechanisms in a pair of Impinging Jets”, Journal of Propulsion and Power, Vol.17, No.3 May-June 2001.
3. M. C. Kline and R. D. Woodward, “Imaging of Impinging Jet Breakup and Atomization Process Using Copper-Vapor-Laser-Sheet-Illuminated Photography”, Non-Intrusive Combustion Diagnostics, Kuo and Parr Eds., Begell House, INC., pp. 552-568, 1994.
4. 黃柏霖、袁曉峰， 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，九十四學年度。
5. Tony Yuan, Cetera Chen, Zhung Yi Quan, Berlin Huang, “Observation of the Spray Phenomena of Unlike-Doublet Impinging Jets”,11th International Symposium of Flow Visualization, University of Notre Dame, Indiana, USA., August9-12, 2004.
6. Rupe, J. H., “The Liquid Phase Mixing of a Pair of Impinging Streams”, Jet Propulsion Lab. Progress Report.20-195, California Inst. of Technology, Pasadena, CA,6 Aug 1953.
7. Tate, R. W., “Spray Patternation,” Industrial and Engineering Chemistry, Vol. 52, pp. 49A-53A, 1960.
8. Lefebvre, A. H., Fuel Effects on Gas Turbine Combustion -Ignition, Stability and Combustion Efficiency, ASME J. Eng. Gas Turbine Power, Vol. 107,pp. 24-37, 1985.
9. Reeves, C.M., and Lefebvre, A. H., Fuel Effect on Aircraft Combustor Emissions, ASME Paper 86-GT-212, 1986.
10. Rink, K. K., and Lefebvre, A. H., Influence of Fuel Drop Size and Combustor Operating Conditions on Pollutant Emissions, SAE Technical Paper861541, 1986.
11. Lefebvre, A. H., Atomization and Sprays, Hemisphere Publishing Corporation, pp. 11-45, 1989.
12. McCarthy, M. J., and Molloy, N. A., Review of Stability of Liquid Jets and the Influence of Nozzle Design, Chem. Eng. J., Vol.7, pp.1-20,1974.
13. N. Dombrowski and P. C. Hooper, “A Study Of Sprays Formed by Two Impinging Jets”, Journal of Fluid Mechanics, Vol. 18,part 3, pp.291-305, 1962.
14. D. Grapper, N. Dombrowski, W. P. Jepson and G. A. D. Pyott,”A Note on the Growth of Kelvin-Helmholtz Waves on Thin liquid Sheets”, Journal of Liquid Mechanics, Vol.57, part4, pp.671-672, 1973.
15. N. Dombrowski and P. G. Hooper, “The Effect of Ambient Density on Drop Formation in Sprays”, Chemical Engineering Science,Vol.17, pp.291-305, 1962.
16. N. Dombrowski and W. R. Johns, “The Aerodynamics Instability and Disintegration of Viscous Liquid Sheets”, Chemical Engineering Science, Vol. 18, pp.203-214, 1963.
17. W. H. Nurick, ”Orifice Cavitation and Its Effects on Spray Mixing”, Journal of Fluid Engineering, pp. 681-687, December 1976.
18. Kihoon, J., Byoungjik, L. and Youngbin, Y., Comparison of Mixing Characteristics of Unlike Triplet Injectors Using Optical Patternator, Journal of Propulsion and Power,Vol.21, No.3,May-June, 2005.
19. Y. D. Won, Y.H. Cho, S.W. Lee, and W.S. Yoon, Effect of Momentum Ratio on the Mixing Performance of Unlike Split Triplet Injectors, Journal of Propulsion and Power, vol. 18, No.4, July-August 2002.
20. Eckbreth, A. C., Laser Diagnostics for Combustion Temperature and Species, Gordon and Breach Publisher, 1996.
21. Tony Yuan , Cetera Chen , and Berlin Huang, “A PLIF Observation of the Impingements of NTO/MMH Simulants for a 5-lbf Rocket”, Institute of Aeronautics and Astronatics, National Cheng Kung University, Tainan, Taiwan, R.O.C, AIAA Journal accepted, 2006.
22. W.H. Lai, W. Huang and T. L. Jiang, Effect of Orifice Size and Impinging Angle on the Characteristics of a Like-Doublet Impinging-Jet, International Journal of Turbo and Jet Engines, 15, 155-164, 1998.