衝擊式霧化主要應用於液態火箭引擎燃燒室，可分為同質式霧化及異質式霧化，小型液態火箭多採用自燃性推進劑，以異質式霧化為主。本研究以濃度95%之酒精及純水作為工作流體，衝擊角度為60°、90°及120°，噴注孔口直徑為0.3、0.5及0.7 mm，模擬自燃性推進劑MMH及NTO之衝擊霧化，進行無毒性之冷流實驗，延續過去之研究而對影響霧化液滴大小之參數加以探討，包括噴流流速、液膜型態、液膜幾何形狀、噴注器孔徑、衝擊角及環境壓力，並與先前之研究結果及理論分析做比較，期望能增進對衝擊霧化現象的了解，並有助於液態火箭噴注器的設計。

　　在液膜型態方面，同質酒精衝擊可形成六種液膜型態，並且無穿孔破裂液膜的出現。當衝擊角為120°時，液膜在階梯式液緣模式時即破裂，使之無法形成封閉液緣模式，而衝擊角度愈大其液膜型態會在較低流速時轉換模式。

　　在液膜幾何形狀方面，衝擊角度愈大，液膜長寬比愈小。由實驗結果可得一經驗公式以方便求取液膜平面徑向與液緣切線之夾角，且液膜長度可由Ibrahim等人[8] 所推導之公式乘上一常數值求得，此常數值與黏滯係數有關係。在低流速時，重力效應會使液膜向下偏移，但對液膜型態及大小影響不大。

　　在霧化液滴平均大小方面，衝擊角60°時，同質酒精衝擊霧化液滴在流速增加時出現不減反升之現象。當液膜型態為完全發展模式前，孔口直徑愈大，其霧化液滴愈小；流速再增加時，則趨勢相反，但霧化液滴大小差距不大。純水-酒精之異質式衝擊霧化，其霧化液滴與酒精之同質衝擊霧化液滴較為接近，酒精之低表面張力特性為重要因素。

　　在環境壓力之影響方面，其對衝擊液膜之幾何形狀並無影響，但環境壓力愈大，液膜型態在較低流速時轉換模式。當液膜為完全發展模式前，環境壓力愈高其霧化液滴平均粒徑愈小，當流速增至20 m/s時，環境壓力對霧化液滴大小影響不大，同質純水衝擊霧化液滴大小接近100 μm。

　Impinging jet atomization is mainly used in liquid rocked proportion systems, including like-doublet and unlike-doublet injectors. The latter is usually applied to bipropellant small-scaled liquid rocket, which uses storable and hypergolic propellants. In this research, 95% ethanol was used as the working fluid to simulate the impinging jets. The orifices of the injector element are 0.3, 0.5, and 0.7 mm in diameter, impinging angle is set to be 60°, 90°, and 120° respectively. Main parameters of atomizing performance are discussed, such as jet velocity, impinging angle, jet diameter and ambient pressure. The results are also compared with previous research.

　In liquid shape mode, six distinct flow patterns can be observed, and the perforated film doesn’t appear. The larger impinging angle, the lower threshold jet velocity of mode transition is observed.

　Regarding the liquid film size, the aspect ratio decreases with increasing impinging angle. One empirical equation can be used to calculate the tangential angle, and the equation induced by Ibrahim et al.[8] can figure out the film length by multiply a constant.

　When the impinging angle reaches 60°, there is a sudden increase of mean drop size during the increment of jet velocity. The SMD appears to be inversely proportional to the jet diameter until film shape transit to open mode. The SMD of unlike-doublet impinging is highly influenced by the surface tension of liquid.

　High ambient pressure has no effect on film size, but it causes the liquid shape change mode in lower jet velocity. In higher ambient pressure, smaller SMD value is measured before the liquid film transit into open mode. When the jet velocity approaches 20 m/s, the SMD of water-like impinging jets reach 100 μm, which is independent of ambient pressure from 2 to 9 bar.

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