同軸噴注為液態火箭之噴注器設計之重要型態之一，其作用為使液體氧化劑與氣體燃料進行霧化混合並燃燒。傳統噴注盤將同軸噴注單元均勻放射性環狀排列，而本研究為了簡化其設計，將所有氣體流道整合成一個環狀結構，而為了分析其霧化特性，本研究設計多組非對稱式同軸噴注器以模擬其環狀結構。本研究所使用的噴注器氣體流道形狀為矩形，並改變矩形外管之長寬比；氣體流道內含單管及三管狀液體噴注器，設計固定液體與氣體的出口面積比，並改變三內管間距離。
本研究應用三種實驗方法觀察霧化現象；使用高速攝影系統拍攝液柱碎裂分解過程及變化，使用平面雷射激發螢光（Planar Laser Induced Fluorescence, PLIF）觀測噴霧二維質量機率分布並計算霧化角、面積分布與非均勻度，以及使用粒徑分析儀觀測粒徑分布變化，並計算核心粒徑。
實驗結果顯示長寬比為1之單管噴注器霧化效果最差；傳統同軸噴注器的霧化效果比所有非對稱矩形單管噴注器要好，但是矩形三管噴霧間的交互作用會使其霧化效果提升，且噴霧間距離越近交互作用越大，使其霧化效果越好，甚至較傳統同軸噴注為佳。

Coaxial injector is mainly used in liquid rocket propulsion system design. This injector atomizes the liquid oxidizer by the gasified fuel and lets the propellant mix with each other. In this research, to simplify the structure of injector plate, all gas channels are integrated into rings with liquid injector within. In order to study the spray phenomena of this ring channel injector, asymmetric coaxial injector models are used to simulate its behavior. The models are designed to be single and triplet liquid injections within a rectangular gas flow channel. All injector models have the same gas-to-liquid-flow area ratio but different aspect ratios of the rectangular channels.
Three means were adopted in this research to study the phenomena of spray. First, the high speed shadowgraph is utilized to observe the breakup of liquid column. Second, planar laser induced fluorescence (PLIF) technique is used to determine the 2-D mass probability distributions of the spray and the spray angle, mass distribution area, and patternaton index (P.I) are evaluated by it. Third, Malvern droplet analyzer is used to measure the droplet size distribution as well as the core SMD (SMD0.15) of the spray.
The results show that the spray behavior of the conventional axisymmetric coaxial injector is better than the asymmetric ones. However, the interaction between sprays in the triplet design shows improved liquid atomization and closer distance between liquid sprays causes stronger interaction thus to a better spray behavior, even better than the axisymmetric one.

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