近年來，衛星朝向小型化、輕量化發展，連帶其衛星推進器之輕量化與小型化，而由於雙基推進系統具有高比衝值、高效率、可重複點火以及推力可調之潛力，因此，小推力之雙推系統常作為高空飛行器及衛星之姿態調整與軌道轉換的動力來源。因此本研究之目的為建立一20牛頓推力之氣態甲烷/N2O雙基推進系統，透過基本參數計算、噴注器設計、燃燒室設計、噴嘴設計以及決定其點火位置設計出一可行之雙基推進系統，並達到預期之性能。
經由CEA之輔助可得艙壓10bar、推力20牛頓之所需質流率及噴嘴喉部與出口直徑。燃燒室體積由特徵長度及燃氣停留時間計算得到一可行區間，並透過文獻之參考決定其燃燒室直徑為10毫米以及決定一長度區間來進行測試。噴嘴採用設計簡易且容易加工的錐形噴嘴，漸縮段角度為45度，漸擴段角度為15度。噴注器的部分採用蓮蓬頭式噴注器，透過單股噴流實驗及噴流擴張計算得到擴張曲線，計算出噴流平均擴張角度。並由choking condition得到各孔徑所對應之質流率。而本研究期望以一單元噴注器即可完成一發動機設計，成功產生推力，因此以燃燒室直徑為限制，由此質流率與擴張角度即可進行噴注器的配置。完成上述之設計後即透過數值模擬進行噴注器之篩選、決定其點火位置設計以及測試發動機之可行性，透過Ansys Fluent進行冷流及熱流的模擬，篩選出三個噴注器並決定其點火位置位於燃燒室後方，且確認此發動機之可行性。
最後即進行發動機實際點火測試，並將實驗與模擬結果交互驗證。測試結果成功點燃、建壓並產生推力，其推力為15.5牛頓、艙壓8bar、比衝值約171s。本研究成功建立出甲烷/N2O氣態雙基推進系統，並透過各燃燒室長度測試得到此推進劑與噴注器組合之特徵長度可行區間為0.3至0.5公尺，燃氣停留時間區間為0.6毫秒至1.1毫秒。最後驗證模擬與實驗結果相符，證實模擬所使用之化學反應機制可用於甲烷/N2O之擴散火焰。

Recently, the satellite technology has been widely studied. With the advantage of high performance and the flexibility of throttling and multi-ignition, bi-propellant rocket system has been an extraordinary choice for satellite propulsion system. In this research, the target thrust of the system is 20 newton referred to the propulsion system of Hayabusa II. As for the fuel and the oxidizer, it chose N2O as the oxidizer and CH4 as the fuel. Also, using gaseous propellant can shorten the combustion chamber and simplified the injector design. Therefore, the main purpose of this study is to develop a 20-newton N2O/CH4 gaseous bipropellant thruster.
This research expects to complete a thruster design with a single injector to reach the target thrust with the simplest configuration. By the theory calculation, the flow visualization experiment of the jet flow and the results of the numerical simulation, the design of the injector, combustion chamber and nozzle can therefore be determined. Finally, the hot fire tests would be performed to verify whether the thruster achieve the design point.
The experimental results show that the gaseous bipropellant system is successfully built and it yields 15.5 newton thrust. The chamber pressure is 8 bar, and the specific impulse is 171s. The practicable interval of the characteristic length and the stay time of this system are 0.3-0.5m, and 0.6-1.1ms by the calculation of the experimental data. By comparisons with the experimental measurements and numerical simulation, it has been proved that the model predictions with the chemical mechanism of N2O are in good agreement with the experimental data.

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