利用電弧汽化法製作氧化鋁粉末及利用鋁線氧化熱推進引擎可行性之探討

Production of Alumina Powder by Arc-evaporation Method and the Study on Feasibility of Al-oxidation-heat Powered Engine

陳宗奇(Tsung Chi, Chen)

指導教授 ： 葉均蔚 ； 謝光前

國立清華大學/工學院/材料科學工程學系/碩士(2015年)

摘要

本研究的目標為利用電弧汽化法製備奈米級氧化鋁粉末，為取代目前工業上所使用的化學法與物理法以降低生產成本；並且開發不以傳統汽柴油而以固態鋁線作為燃料的引擎，因為每毫升鋁的氧化熱約為汽柴油的2.17倍，且在過程中不產生二氧化碳，所以此引擎的開發甚具未來性。
本實驗以自行設計的粉末製備機利用電弧汽化法，將送入的鋁線經局部高溫氣化後與周圍氣體反應生成粉末，收集反應後生成之粉末去分析，了解到本實驗製備出的粉末為奈米級球形氧化鋁粉末，粉末粒徑約在10-150 nm之間，而大部分的粉末為γ- Al2O3。
此外，本實驗以二行程引擎作為試驗，利用接觸式起弧的方法將鋁線汽化後氧化爆炸。點火過程中，鋁線從噴火嘴石墨杯中垂直向上送，而活塞上下往復式運動，當活塞到達上死點位置時，活塞上的突起電極與鋁線接觸產生電弧並汽化產生爆炸推力。噴火嘴石墨杯的設計主要是侷限電弧的能量，增加鋁線的汽化與爆炸力。經過不同設計的噴火嘴測試後，顯示此結構可以使鋁線在上死點瞬間確實汽化與氧化爆炸，但觀察到仍存在著幾點明顯的缺點：1.點火處附近的鋁線受熱膨脹後堵塞送線通道，導致送線停止無法連續運轉；2.鋁熔化後形成的鋁湯在在石墨杯中因為氧化爆炸的力量而被往回推，倒灌回送線通道中後因為冷卻凝固堵住送線通道。因此，這兩項缺點為未來主要需要克服的問題。

關鍵字

電弧汽化法 ； 鋁線引擎 ； 氧化鋁粉末

並列摘要

Aluminum-oxidation-energy powered engine has attracted our interest in replacing conventional engine powered by liquid fuel. This attraction is due to the high energy density and the reduction of carbon dioxide emission in the combustion of aluminum wires. During this process, we find that the arc-evaporation method can produce alumina nanopowder. Besides, the arc-evaporation method can reduce the production cost in comparison with traditional process.
We design a new equipment to produce alumina nanopowder by the arc-evaporation method. First, it uses the heat which is produced by the arc-evaporation method to evaporate aluminum wire. And the aluminum gas reacts with oxygen to form alumina powder. Then, we analyze the collected powder, finding that the spherical particles produced from the combustion of aluminum wires are several hundreds of nanometers in diameters. Most of the powder is gamma-alumina.
We use a two-stroke-cycle engine and an argon arc welder with the arc welding mode to stimulate the arc operation by touching and separating. Aluminum wires are feed through the spitfire nozzle and the graphite funnel which is designed to increase the vaporization rate of aluminum wires by reducing the heat loss of arcing. The arc is generated between negative electrode and aluminum wire by touching and separating when the piston is away from the top dead center.
The results show that the efficiencies of the vaporization and the oxidation of aluminum wires are enhanced with the appropriate design of the spitfire nozzle. However, there are still some problems which require further works to be solved. First, the wires near the arc root might be thermally-expanded to seize the transport channel, resulting in no feed of Al wire. Second, the melting aluminum would be flowed back to the transport channel by the force of aluminum-oxidation and solidified due to cooling, resulting in seizing the transport channel.

參考文獻

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