- 學位論文
氣心式同軸旋流噴注器之動態霧化表現之研究
The Investigation on Dynamic Spray Characteristics of Gas-Centered Swirl Coaxial Injector
摘要
鑒於現今太空載具發展蓬勃，液態燃料火箭引擎為其關鍵技術之一。氣心式同軸旋流噴注器更是被大量應用於燃氣產生循環火箭引擎當中，因此而被現今學界廣泛研究。因此本研究旨在建立一套設計液態燃料火箭引擎與氣心式同軸旋流噴注器之方法，並利用自行開發之流量激擾球閥產生週期性變化的流量進行噴注器之動態霧化表現之分析，進而達成對氣心式噴注器於大範圍流量變化下之理解。 本研究首先藉由理論計算與NASA CEA進行液態燃料火箭以及氣心式同軸旋流噴注器之理論設計，並藉由得到之關鍵幾何參數搭配安全係數之配合進行細部設計以供冷流實驗與後續地面測試之用。接著，本研究利用全橋閘極驅動器搭配微處理器自行研發一有刷直流馬達驅動器做為流量激擾球閥之制動器，並使用LabView搭配增量式編碼器進行角度控制器之開發。最後，透過自行架設之背光影像觀測系統、流量供應系統，以及前述之氣心式同軸旋流噴注器進行穩態以及動態冷流實驗。 本研究經過自行開發之霧化特徵分析程式分析冷流實驗結果得出以下結論。1. 透過改變氣體噴嘴長改變退縮比之設計會影響到液體旋流之強度。2. 經分析結果發現，液體輸送壓力震盪會對液膜產生大幅度擾動。相較穩態之表現，會縮短液膜之破碎長度。3. 經分析結果發現，大片成膜之液膜對於氣體動量之變化較為敏感。4. 經分析結果發現，既使在動量比震盪的情形下，不同震盪相位差對於液體之巨觀破碎行為並未產生影響，因而得出動量比在液膜破碎行為佔有主導地位之結論。
並列摘要
Due to the popularity in space exploration, the importance of liquid propellant rocket engines (LPRE) has increased. Gas-centered swirl coaxial (GCSC) injectors are widely implemented in gas-generation cycled LPREs. Thus, GCSC injectors has been a popular subject these years. The aims of this thesis were to establish a design process of LPRE and GCSC injector, and gain deeper understanding of the behavior of GCSC injector under large amplitude flowrate variation by conducting dynamic cold flow experiment using self-developed flowrate excitation ball valve. The LPRE and GCSC injector were firstly designed by theoretical formulae, and the detailed design were done with key geometric parameters acquired for future ground static test and cold flow experiments. After that, full-bridge gate driver and microcontroller chips were used to developed a DC motor controller. Angular position controller was realized by LabView, incremental encoder, DC motor and DC motor controller mentioned above. Finally, both steady and dynamic cold flow experiments were conducted with self-constructed backlight illumination observation system, fluid supply system, flowrate excitation ball valve, and GCSC injectors. After analyzing the results of cold flow experiment with self-developed computer program, four major conclusions were made: 1. The design of changing gas nozzle length to change recess ratio was found to be weakening the swirl strength. 2. The pressure oscillation in liquid manifold would create addition perturbation to liquid film, leading to the shortening of breakup length. 3. Large intact liquid films were more sensitive to change in gas momentum. 4. Momentum ratio was found to be a dominant factor determining the general breakup of liquid film based on the fact that spray cone structure was independent of phase difference in pressure oscillation.