雙噴流衝擊霧化乃是利用液態噴流之相互衝擊而產生霧化及混合之效果，此種機構主要應用於液態火箭推進劑之霧化混合上。而噴流衝擊後之碎裂情形主要受了空氣動力及流體動力之不穩定因素所造成，故噴注器之操作與設計參數及流體之物理性質(密度、黏滯力及表面張力)皆為影響噴流衝擊霧化混合之重要因素。
本研究應用PLIF技術配合影像分析方法，進行同質噴流衝擊霧化混合現象之觀察研究，探討噴流動量通量及表面張力對噴流衝擊霧化與混合現象之影響。實驗之噴注器孔口直徑為0.3㎜，而衝擊角則固定為60°。實驗結果顯示，同質噴流之衝擊霧化存在一特徵動量通量，當噴流動量通量達其特徵值時，衝擊噴流即會產生較佳的霧化，而霧化液滴亦明顯均勻的分布於霧化區內。而較低表面張力之流體，因其噴流較易因空氣
與流體動力不穩定性而碎裂霧化，故相較於水之衝擊噴流，其噴流易於於較低之動量通量便碎裂霧化為微小液滴，且更均勻的分布於霧化區內。
由噴流混合效率觀察顯示，噴流之混合效率主要受到噴流之相互穿透程度影響。噴流之混合現象因此而可區分為兩種形式，當衝擊噴流之霧化未達完全發展模式時，噴流之混合現象為液態噴流相互融合之混合;當衝擊噴流之霧化達完全發展模式時，噴流之混合現象則為霧化液滴相互穿透之混合。當噴流動量通量達其特徵值時，即衝擊噴流為有效的霧化，其霧化液滴之穿透率為最均衡的狀況，故衝擊噴流有最佳的混合效率。低表面張力噴流因其較易於碎裂霧化，造成其霧化液滴之穿透率均較高表面張力噴流(水)為高，使得其混合效率較為不佳。
本研究亦進一步以韋伯數分析噴流霧化混合現象，顯示不同表面張力噴流可於相同特徵韋伯數(90,000)時，達到有效之霧化混合效率。故韋伯數為可用以定義噴流霧化混合現象之重要參數。
本研究亦完成以NTO與MMH模擬液為工作流體之雙/三噴流衝擊霧化混合之冷流場觀察研究。實驗結果顯示，噴流的動量通量比與物理性質(表面張力或黏滯係數)可明顯影響噴流之質量與混合比分布；表面張力低者較易被衝擊霧化，噴流相對動量通量較高者，其噴流機率分布較為集中。當噴流O/F=1.18時，因兩噴流具相當之動量通量，整體與個別噴流的霧化液滴分布皆具最佳的對稱性與均勻度，且其亦有最佳之混合效率及平均特徵速度，顯示其有最佳的NTO/MMH反應燃燒效率。
對於三噴流衝擊霧化而言，外側NTO噴流的衝擊動量增加將造成其霧化液滴分布更均勻，但MMH霧化液滴則並未隨著NTO噴流的衝擊動量增加而明顯改變。於同樣實驗條件下，三噴流衝擊霧化液滴均較雙噴流衝擊霧化對稱及均勻的分布於較小的霧化區域內，且當O/F=1.19-1.59時，NTO/MMH三噴流衝擊霧化有最佳的燃燒效率。
本研究亦進行NTO/MMH開放空間自發性衝擊燃燒之實驗觀察。實驗結果顯示，當NTO/MMH噴流互相衝擊後，霧化之NTO/MMH液滴皆需一段距離的混合及氣化，方能產生劇烈的燃燒，而此一誘發劇烈燃燒的距離則與MMH液滴粒徑及粒徑分布有關。分析NTO/MMH燃燒現象顯示，隨著O/F之增加，燃燒反應則越趨劇烈，而火焰則會延續更長的長度，而最佳的霧化混合及燃燒反應則發生於O/F=1.2時。當O/F大於1.2，燃燒現象則逐漸以擴散火焰方式反應於未完全霧化之NTO區域外緣，其劇烈燃燒之火焰長度可延續達約80 mm。

以所量測之NTO/MMH火焰溫度分布，與冷流場模擬NTO/MMH反應溫度分布比較顯示，冷流場模擬NTO/MMH反應溫度分布可用以預測真實NTO/MMH反應火焰溫度分布之高溫區的形狀與位置。但由於開放空間的NTO/MMH燃燒反應，存在強烈熱對流及熱輻射效應，使得所觀察的火焰溫度均低於冷流場模擬之反應溫度。

The impingement of liquid jets is generally used for the breakup and mixing of the liquid propellants in the rocket injector design. While impinging, the jets become aerodynamic and hydrodynamic unstable thus disintegrating. The factors, such as momentum flux of the jets and the surface tension of the liquids, have a significant effect on the impinging spray. In this study, the effect of the momentum flux and surface tension on the impinging spray was experimentally investigated and a conceptual mixing mechanism has been established. For the design of a 5-lbf rocket, the cold-flow and hot-fire observations of the impingements of NTO/MMH system were also conducted.
The spray phenomena of impinging jets were studied by a simple image technique as well as PLIF technique coupled with statistical analysis. From the PLIF observation, the mass probability distributions of the impinging spray were constructed. Thus, the uniformity and mixing efficiency of the impinging spray can be determined. For NTO/MMH impingements, the distributions of local mixture ratios and flame temperatures were deduced, and the characteristic exhaust velocities were estimated.
The results demonstrated that the momentum flux as well as the fluid’s surface tensions crucially affected the spray pattern and mixing of the impinging jets. A characteristic momentum flux was observed which can be used to justify an effective breakup and mixing condition. Above the characteristic momentum flux, the spray uniformities were almost invariant while the droplets distributed in a progressively smaller area. Smaller surface tension of liquids leads to more uniform distribution with smaller characteristic momentum flux for their easier to be disintegrated.
The mixing of the like-doublet impinging jets was mainly depended on the mutual penetration of the jets. However, the mixing phenomena can be differentiated into two types: merged liquid mixing at momentum flux lower than the fully developed condition, and droplet penetration mixing at momentum flux higher than fully developed condition. It also showed that, at the characteristic momentum flux, the optimum mixing efficiency occurred as the penetration was improved. Above the characteristic value, the penetration slightly increased and decreased the mixing of the jets. For lower surface tension liquid, higher penetration was shown, and it resulted in the poor mixing comparing with the higher surface tension liquid. Normalization of the characteristic momentum flux to eliminate the surface tension difference, the above described characteristic conditions appeared at Weber number at ~90,000.
In the cold-flow study of the NTO/MMH system, triplet impingement showed its superior properties in symmetry and uniformity of the spray than that of the doublet impingement. Triplet impinging mixing was less sensitive to momentum flux ratio’s varying, however, for the operation of a 5-lbf NTO/MMH rocket, the optimum mixing efficiency and average characteristic exhaust velocity occurred at O/F1.2, corresponding to the unity momentum flux ratio, with doublet impingement.
Comparison of the hot-fire and the prediction from the cold-flow observation of NTO/MMH impinging combustion, the results demonstrated that the predicted planar temperature distributions adequately described the shape and location of flame zones in the hot-fire observations. In view of the flame images, an induction distance after jets’ impingement always exists before reaching the intensive reaction zone, while the length of the induction distance was controlled by the MMH local evaporation rate. The analysis also verified that the impinging combustion of MMH and NTO followed the conventional spray combustion pattern. A maximum length of 80 mm of the intensive reaction zone was shown, while diffusion-type combustion occurred at high O/F conditions.

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