本研究使用計算流體動力學(Computational Fluid Dynamics, CFD)商用軟體STAR-CD於一部雙火星塞的二閥單缸四行程150 c.c.引擎，進行單火星塞與雙火星塞的燃燒計算，探討在不同當量比以及不同點火時刻下對引擎性能的影響。進一步更改雙火星塞位置，以找出最佳的雙火星塞擺放位置。結果顯示，當兩個火星塞分別擺放於離氣缸壁約四分之一缸徑時，此雙火星塞引擎的性能最佳。依據此一最佳雙火星塞擺放位置，在不同的當量比(equivalence ratio)及點火角度時，以數值方法計算，分析燃氣在氣缸內的燃燒過程、缸內平均壓力、平均溫度、已燃質量分率(burned mass fraction of fuel)、扭力與馬力，探討單火星塞與雙火星塞引擎的性能。結果顯示，在固定的當量比及點火角時，單火星塞引擎與雙火星塞引擎的火焰傳播速度數值接近，在當量比Φ = 1.0，點火角提前20度時，大約17 m/s。但是雙火星塞引擎的火焰從兩邊同時向中間傳遞，所以有比單火星塞引擎較大的已燃質量分率。雙火星塞引擎的最大缸壓、平均有效壓力、輸出扭力、馬力比單火星塞引擎大，例如，在當量比Φ = 1.0，點火角度提前20度時，雙火星塞引擎的最大缸壓、扭力與平均有效壓力分別比單火星塞引擎的大31.54 %、6.90 %與6.90 %。

A two-valve, four-stroke, motorcycle engine installed with dual spark plugs was studied by using the commercial CFD code (STAR-CD). The performance of the single and dual spark plugs engines during combustion processes at various equivalence ratios and ignition times were calculated by the computational analysis. The locations of the dual spark plugs were varied to study the effects on the engine performance. The optimized spark plug locations were found based on the conditions that the mean effective pressure and torque of the engine attained maximum values. It was found that the optimized location for each spark plug was one-quarter bore diameter away from the rim of the cylinder head. The calculated results of engine performance based on the optimized locations of dual spark plugs showed that the dual spark plugs engine has larger burned mass fraction of fuel, maximum in-cylinder pressure, mean effective pressure, and output torque than the single spark plug engine at fixed equivalence ratio and ignition crank angle.

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