本研究探討二閥單缸四行程中置型預燃室引擎的燃燒情形、汙染物生成量與引擎性能，並與原廠單火星塞引擎、雙火星塞引擎、側置型預燃室引擎做比較。使用計算流體力學軟體CONVERGE分析二閥單缸四行程預燃室引擎，在引擎轉速固定5500 RPM、進氣效率37 % 時，改變預燃室噴孔數目n、噴孔等總截面積無因次參數β、噴孔傾斜角δ、預燃室傾斜角φ、噴孔圓周角γ、預燃室軸向噴孔孔徑dc、預燃室空燃比 (A/F)PC、主燃室空燃比 (A/F)MC、預燃室噴油時機to,PC、點火時機ti，分析七個性能量化指標：(1)汽缸內平均壓力峰值、(2)平均溫度峰值、(3)輸出指示功、(4)指示熱效率、(5)燃燒持續角度、(6)循環變異係數、(7)單位燃料消耗量以及四個燃燒產物汙染量化指標：(1)碳氫化合物質量、(2)氮氧化合物質量、(3)一氧化碳質量、(4)二氧化碳質量，並探討缸內流場、溫度分布、油氣濃度分布、殘留油氣分布與火焰傳播行為，藉此判斷中置型預燃室最佳幾何設計以及物理參數，並與其餘種類引擎比較。與原廠單火星塞引擎相比，可減少油耗25.46 %，碳氫化合物排放減少84 %；雖然氮氧化合物排放增加117%，但此一氮氧化合物可使用三元觸媒降低。這些結果表示中置型預燃室引擎不但可以提升缸內燃燒效率，還有助於解決側置型預燃室引擎之火焰傳播缺陷，改善污染排放，同時增進燃油經濟性。

The characteristics of flow, fuel distribution, combustion, power performance, and pollutant generation of a prechambered, two-valve, four-stroke reciprocating engine were analyzed using the commercial CFD code of CONVERGE. The engine speed and the intake efficiency were set at 5500 RPM and 37%, respectively. The typical parameters such as the peak mean pressure, peak mean temperature, indicated work, thermal efficiency, crank angle elapsed at 10%  50% MFB (mass fraction burning), specific fuel consumption, flame remaining before opening of exhaust valve, and the masses of exhaust pollutants (hydrocarbon, nitrogen oxides, carbon monoxide, and carbon dioxide) were calculated. The results were compared with those of a single-spark-plug engine and four types of dual-spark-plugs engines. Analyses were focused on the prechamber orifice geometric parameters (i.e., orifice numbers n, equivalent and dimensionless total cross-sectional area β, tilt angle δ, tilt angle δ, tilt angle δ, and circumferential angle γ) as well as the physical parameters (i.e., air-fuel ratio of prechamber (A/F)PC, oil injection timing of prechamber to,PC, spark timing of prechamber ti, air-fuel ratio of main chamber (A/F)MC). The results showed that by optimizing the prechamber orifices diameter and arrangement, the prechambered engine presented significant improvement in engine performances over other engines. The optimized one could lead to increase of engine power output by 26% and reduction of hydrocarbon emission by 84% at (A/F)PC = 14.5 when compared with single-spark-plug engine. At lean-burn combustion, the engine performances of the optimized prechambered engine were supreme when compared with those of the single-spark-plug engine. The specific fuel consumption of the prechambered engine operated at (A/F)MC = 15.5 could be drastically lowered by 25.46% when compared with single-spark-plug engine.

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