本研究利用商業套裝計算流體動力學(Computational Fluid Dynamics, CFD)軟體STAR-CD，針對一四閥單缸四行程500 c.c.引擎，在考慮不同的空氣與燃料混合型態(stratified charge、two-stage charge和homogeneous charge)下，設計噴油嘴安裝位置與傾角，並根據燃油濃度分佈與缸內平均SMD，判斷出較佳的噴油嘴安裝位置與傾角設計，之後針對較佳的噴油嘴安裝位置與傾角設計，探討在有無燃油噴射的狀況下，於進氣和壓縮行程期間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之交互作用，並藉由速度向量場與體平均渦度滾轉比的關係進一步了解燃油噴射對流場的影響。而缸內燃油噴射隨時間衍化的軌跡與氣流的交互作用將可作為設計缸內直噴引擎的重要參考。因此往後在設計缸內直喷引擎時，可藉由先行計算缸內氣流之運動與液滴霧化之衍化，並以此結果做為一重要之參考指標後，再進行引擎性能參數測試，找出最佳的噴油時間及點火參數，以減少初期設計缸內直噴引擎時所需之成本及時間。

The location of injector & spark plug and injector inclination angle for a single cylinder, four-valve, 500 c.c. displacement motorcycle engine is designed in considering different kind of fuel injection mode (stratified charge, two-stage charge and homogeneous charge) by using a commercial software package of CFD (Computational Fluid Dynamics) code — STAR-CD. Confer tumble motion of in-cylinder flow circles cylinder radius and the interaction of spray flow field and flow motion in GDI, and understand the influence for fuel injection on flow field by the relation of velocity flow field and average volume tumble ratio. The trajectory of in-cylinder fuel injection derivatives with time can be an important reference for designing GDI engine. Therefore when designing GDI engine, first calculate the motion of in-cylinder flow and the derivation of droplot spray, and using the result can be an important target, and then proceed the test of engine performance parameter to find the optimum parameter of injection timing and spark timing, then reduce time and money for the first stage to design the GDI engine.

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