Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/1586
標題: 單缸二行程引擎二次空氣系統特性分析
The Characteristics Analysis of Secondary Air Induct System for Single Cylinder Two Stroke Engine
作者: 王又弘
關鍵字: Secondary Air Inject System (SAIS);二次空氣;Two Stroke Engine;二行程引擎
出版社: 機械工程學系
摘要: 
觸媒轉化器對排氣污染改善有十分顯著的效果,其中影響機車氧化觸媒轉化器效率的重要因素之一就是反應時的氧氣濃度:O2濃度越高則效率越高。而一般機車引擎都是在濃油的情況下運轉,排放廢氣中的O2含量太少,無法為氧化反應提供充足的氧氣。為提供把CO與HC氧化所需的氧氣,故需將外界新鮮空氣引入排氣系統中。這種裝置稱為二次空氣系統。
本文主要是在進行引擎穩定運轉時,二次空氣系統中簧片閥的動態量測,其中包括簧片閥振動、二次空氣吸入側壓力與流量的量測與模擬。文中並探討各種操作條件對機車引擎排放物與二次空氣之間的影響。
本研究發現簧片閥均以mode1的振動模式運動。並且在比較準穩態模式、懸臂樑模式、和二次系統模式等三種模擬方法後,認為雖然使用二次系統的誤差很大,但還是三種之中最適合的,此外,本研究也發現二次空氣流量與將隨著管徑增加而增加,而隨管長增長而減小。而二次空氣注入排氣管的位置若選在原廠二次空氣注入位置之前,則流量沒什麼明顯的變化。
二次空氣系統可提升低轉速全油門時的觸媒轉化效率,但在中轉速與高轉速時的影響就較小。而半油門時二次空氣系統幾乎都沒有發揮什麼作用。全油門時使用二次空氣會使空燃比增加,其改變範圍約在A/F1~2之間。半油門時使用二次空氣會使空燃比都偏稀(空燃比在15以上)。使用二次空氣會使空燃比增加,其改變範圍約A/F 1~5之間,也是在低轉速有明顯變化,高轉速則變化較少,但都比全油門時明顯。

Catalysts have tremendous advantages in improving the motorcycle engine emissions, and one of the important parameters of managing the catalyst effect is the O2 density when the oxidizing reaction begins. The higher the O2 density is, the more effective the catalyst converter acts. Usually motorcycle engine operators in the rich condition, and the exhausted emissions contains less O2. In this situation, it cannot afford enough O2 that the oxidizing reaction need. In order to support the enough O2 which could eliminate CO and HC in the emissions, it must duct ambient fresh air into the exhaust system. This kind of systems was named "secondary air induct systems" (SAIS).
This study focus on the dynamic simulation and displacement measurement of the reed paddle when the engine operates in the motoring mode, including the motion of the reed, the driving pressure difference and the measurement and simulation of the flow quantity. And it explores some influences between engine conditions (like torque, exhaust temperature, … etc.) and the SAIS.
Results of experiment show that the reed vibrates in the mode1 condition. After compare with the 3 conditions, "quasi-steady" mode, "cantilever beam" mode, and the Ŗnd order system" mode, we think that the Ŗnd order system" mode is the most suitable method to simulate the reed paddle, which has many problems, though. Besides, this study shows that the secondary air quantity grows with the intake duct diameter, and diminishes with the duct length. The intake flow quantity of the SAIS shows little changes if the intake position move forward to the original position.
In full load conditions, SAIS can improve the effect of the catalyst converter when the engine runs in lower rpm and do little effect when engine runs in higher rpm. If the engine equipped with the SAIS, the A/F ratio would increase 1~2. In half load conditions, it displays almost the same data no matter the system equipped with the SAIS or not. If the engine equipped the SAIS, the A/F ratio goes lean (almost above 15) and increase A/F ratio about 1~5.
URI: http://hdl.handle.net/11455/1586
Appears in Collections:機械工程學系所

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