本研究使用實驗與計算方法於一部四閥單缸四行程250 c.c.引擎作缸內未噴油和噴油流場的診測。實驗部分，主要分析噴油嘴之物理特性，並將所得到的開啟延遲、關閉延遲時間及噴油質量流率的數據套用在模擬計算中。計算模擬部份是使用商業套裝計算流體動力學(computational fluid dynamics, CFD)軟體STAR-CD探討在有、無燃油噴射的狀況下，於進氣和壓縮行程期間，分析缸內氣流繞著缸徑軸上的滾轉運動以及缸內燃油噴射之噴霧流場與氣流運動交互作用後的結構與衍化，並藉由循環渦度滾轉比以及SMD等量化指標，找出相異進氣延長段缸內流場的差異和較佳之噴油嘴安裝位置和噴油角度。所得到的實驗與模擬數據顯示Type A和Type B進氣延長段未噴油之缸內流場差異甚小。噴油嘴放置位置以Homogeneous charge的噴油時機作計算，由SMD和濃度空間變異值表現出噴油嘴安裝在位置7、噴油角度α =49o時，液滴尺寸最小且濃度也較平均。透過Stratified charge的噴油時機作計算，油氣濃度在靠近排氣閥處最集中，且靠近汽缸頂部，火星塞可以放置於該區域。

The fuel injection timing during intake stroke of a four-stroke motorcycle engine cylinder has been studied though experiment and computer simulation. The results of injection time delay and injector characteristics were obtained from experimental, were used as reference in the computer simulation. Computer simulation was aided by a CFD software STAR-CD to understand the mechanics during "no-spray" and "spray" situation inside the engine cylinder. Indentify the situation inside the engine cylinder difference between Type A and Type B intank extend, look for better injection locations and angles based tumble ratio, Sauter mean diameter (SMD) and oil concentration distribution. Results from experiments and computer simulations show that the situation inside the engine cylinder difference is small. In homogeneous charge, injector location and injector angle were varied to study droplet size and oil concentration distribution. When injector was placed at the location 7, better concentration distribution and smallest droplet size were found at 49 degrees injection angle. In stratified charge, similar results were obtained when spray injector was investigated. Result from computer simulation showed spark plug focus and provided concentrated droplet at near exhaust valve.

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