超音速燃燒衝壓引擎為新一代的推進系統，其燃燒流場的控制為設計關鍵之一。本論文之研究目的為探討熱焓值改變對液態燃料噴注在超音速流場中霧化特性的影響，以提供日後發展超音速燃燒衝壓引擎之建議與參考。本研究應用反射式震波風洞提供2馬赫空氣自由流，並在固定氣流與燃料噴霧動量通量比的情況下改變自由流或燃料之熱焓值，透過視流技術如紋影法及散射光觀測進行實驗研究。
實驗結果顯示當自由流靜溫上升，空氣的真實速度與黏滯係數會跟著隨之上升、雷諾數下降，其與燃料噴霧之間的剪切力變得更強烈，且噴注平板上自由流邊界層將會提前分離且不穩定性增強，導致因邊界層分離所產生的斜震波與噴霧前緣的弓形震波相互作用之角度與產生之震盪強度的改變，亦使下游自由流速度與壓力不穩定性增加，增強氣流與燃料間的混合效益。故當自由流靜溫上升後，燃料噴霧的穿透高度降低、消散距離減少。實驗亦顯示，當自由流壓力上升，自由流對燃料噴霧的作用力會提昇，燃料更容易碎裂成微小的液滴，故噴霧的滲透高度與消散長度皆有減少的趨勢。當提升燃料熱焓值時，除了使燃料更容易從液態蒸發為氣態外，液態燃料因壓力突然的下降，而出現部分燃料閃蒸霧化，故燃料噴霧的消散距離大幅下降；而整體液態燃料噴霧動量變化有限，故滲透高度亦不至明顯改變。

Combustion flow control is one of the key technologies in the development of supersonic combustion ramjet engine (Scramjet). The objective this thesis is to investigate the effects of temperature and pressure changes on liquid spray behavior in supersonic flow in order to facilitate the future requirements of scramjet. The research utilizes shock tunnel to provide a Mach 2 free stream of air and JP4 is injected laterally into the free stream. The spray behaviors are compared at constant momentum flus ratio of JP4 to air stream while varying the pressure of air stream and the temperature of both air and JP4
The results show that the increase of air temperature actually increases air flow velocity so as to increase the shear stress between the air flow and fuel. Temperature also raises the viscosity of air to cause early boundary layer separation before reaching the injected liquid fuel at wall. It is observed that the interactions between the oblique shock caused by boundary separation and the bow shock caused by liquid jet are more intense and unstable, thus to induce a more unstable downstream air flow which enhances the mixing between the flow and fuel, resulting to decrease the dissipation distance and penetration height of liquid spray. Increasing fuel temperature makes liquid fuel evaporates more readily and causes flash atomization when the high temperature fuel faces sudden pressure drop while injection, and both effects decrease the dissipation distance of spray. Although part of high temperature fuel is evaporated at injection, the spray keeps most of the momentum and thus the penetration height is hardly affected. It is also observed that both the dissipation distance and penetration height decreases with the increase of air pressure. Basically, this can be comprehended to be caused by stronger impact energy of air stream to the liquid jet.

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