超音速燃燒衝壓引擎為新一代的推進系統，其空氣進入燃燒室的滯留時間極短，故需控制液態燃料在極短的時間內與超音速流動空氣充分混合且穩定燃燒。本研究應用側向雙垂直噴注孔將燃料注入超音速空氣流場，期利用前方噴注所產生的弓型震波來擾動後方的噴注，期加速液態燃料的碎裂霧化。透過非侵入式的光學觀測實驗顯示，雙垂直噴注可產生震波交互作用，有效的增加噴霧之不穩定性及流場震盪，可將噴霧消散距離大幅縮短，加速空氣與燃料之混合，而影響噴霧穿透高度之關鍵因素為噴霧本身之動量通量，但藉由提高兩震波之交互作用點，亦可提升噴霧之穿透高度。

In scramjet engine combustor design, the outcome of liquid fuel injection is a vital issue for engine performance. In a very short residence time, a proper mixing between liquid fuel and supersonic air flow has to be achieved, following by stable combustion which also highly relies on the resulted of the mixing effects. The objective of this thesis research is to study the effects of utilizing doublet liquid injections laterally into supersonic airflow on mixing between liquid and air. The experimental study is conducted in a reflected shock tunnel at National Cheng Kung University. The injector is consisted by two orifices and JP-4 fuel is injected into the supersonic airflow. Schlieren photography and Mie scattering are used to observe the flow structure of doublet-jet spray. This injection setup produces interaction between upstream bow shock and downstream bow shock, which enhances the instability of the liquid sprays and the supersonic air flow as well. The results show that the dissipation length of the sprays can be effectively reduced by this double-jet arrangement. Moreover, raising the position of the intersection point of shocks can also increase the penetration height of sprays into the supersonic air flow.

[1] Lewis, M.J, “Significance of Fuel Selection for Hypersonic Vehicle Range ” , Journal of Propulsion and Power, Vol.17, No.6, pp.1214-1221, 2001.
[2] J. A. Schetz, E.A. Kush Jr. and P.B. Joshi, “Wave phenomena in liquid jet breakup in a supersonic crossflow” , AIAA pp.774-778 1980
[3] M. R. Gruber, A. S. Nejab, T. H. Chen, and J. C. Dutton, “Bow shock/jet interaction in compressible transverse injection flowfields” , AIAA journal, 34 (1996), pp. 2191–2193.
[4] Delery J, “Shock/shock and shock-wave/boundary-layer interactions
in hypersonic flows” , AGARD Report 761(part 9) 1989
[5] Reitz, R. D. (1987), “Modeling atomization processes in high-pressure vaporizing sprays” , Atomization and Spray Technology, 3, 309−337.
[6] D. D. Joseph, J. Belanger, and G. Beavers, “Breakup of a liquid drop suddenly exposed to a high-speed airstream” , International Journal of Multiphase Flow, 25 (1999), pp. 1263–1303.
[7] T. F. Fric and A. Roshko, “Vortical structure in the wake of a transverse jet ” , Journal of Fluid mechanics, Vol.279,pp1-47,1994
[8] M. A. Kolpin, K. P. Horn, and R. E. Reichenbach, “Study of Penetration of a Liquid Injectant into a Supersonic Flow ” , AIAA Journal, 6 (1968), pp. 853–858.
[9] K.C. Lin P.J. Kennedy T.A. Jackson, “Structures of Water Jets in a Mach 1.94 Supersonic Cross Flow ” , AIAA, 2004-971
[10] R. E. Reichenbach and K. P. Horn, “Investigation of Injectant Properties on Jet Penetration in a Supersonic Stream” , AIAA, 9 (1971), pp. 469–672.
[11] Dion R. Dixon, “Structures Of Angled Aerated Liquid Jets in a Mach 1.94 Supersonic Cross Flow” , Department of Systems and Engineering Management Air Force Institute of Technology
[12] S. I. Baranovsky and J. A. Schetz, “Effect of Injection Angle on Liquid in Supersonic Flow” , AIAA , pp. 625-629, 1980
[13] H. Ziegler and P. T. Wooler, “Multiple Jets Exhausting into a Crossflow” , Journal of Aircraft, 8 (1971), pp. 414–420.
[14]C. Gruenig, V. Avrashkov and F. Mayinger, “Self-Ignition and Supersonic Reaction of Pylon-Injected Hydrogen Fuel” , Journal of Propulsion and Power, Vol. 16, No. 1, 2000
[15]M. R. Gruber, J. M. Donbar, C. D. Carter and K. Y. Hsu, “Mixing and Combustion Studies Using Cavity-Based Flameholders in a Supersonic Flow” , Journal of Propulsion and Power, Vol. 20, No. 5, 2004
[16]K. Y. Hsu, C. D. Carter, M. R. Gruber and T. Barhorst, “Experimental Study of Cavity-Strut Combustion in Supersonic Flow” , 43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit 8 - 11 Jul 2007
[17] C. O. Asma, S. Tirtey, F. Schloegel, “Flow Topology Around Gas,Liquid,and Three-Dimensional Obstacles in Hypersonic Flow” , AIAA,Vol.50,No.1,pp100-108,2012
[18] 張雅筑“氫氣噴注於背階超音速流場之觀察”成功大學航空太空工程學系碩士論文，2013
[19] K. P. Leong, “Experimental Studies on Self-Ignition of a H2 Transverse Jet in a Supersonic Free-Stream” , Master thesis, National Cheng Kung University, Tainan, Taiwan, 2012
[20]呂冠緯“液態垂直噴注於超音速器流之碎裂現象探討” 功大學航空太空工程學系碩士論文，2014
[21] Francesco Grasso , Carlo Purpura , Bruno Chanetz , Jean Délery , “Type III and type IV shock/shock interferences：theoretical and experimental aspects” , Aerospace Science and Technology 7 (2003) 93–106