Abstract A baseline gasoline engine was retrofitted into a natural gas (NG)/gasoline duel-fuel engine through increasing a NG injection system at its intake manifold. The combustion behaviours and emission characteristics of the engine with different proportions of NG-gasoline blends were investigated. Numerical simulation and experiments verification were performed on a 4-cylinder SI engine. The results show that the combustion behaviours and emission characteristics of natural gas/gasoline dual fuel engine are between gasoline and natural gas. The maximum in-cylinder pressure (MCP), the maximum heat release rate (MHRR) and maximum pressure rise rate (MPRR) decrease with the increase of NG ratio and combustion phases (CA10 and CA50) are retarded, this implies that the adding natural gas to the gasoline can effectively improve the knocking resistance of the engine, which allows to improve the thermal efficiency by increasing compression ratio. The maximum combustion temperature (MCT) and the total overall equivalence ratio increases with the increase of NG ratio, leading to an increase in NO and soot emissions but their increasing proportion of NO and soot emissions at 50% of NG ratio (by energy) is respectively less than 8.7% and 17.3 with respect to the pure gasoline mode, but at the same time, there is an increase in indicated thermal efficiency (ITE) and a decrease in CO, CO2 and HC, this implies that trading off thermal efficiency and NOX emissions by operating the engine with 50% of NG and 50% of gasoline (by energy) without causing further cost and complexity.

中文翻译：

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不同比例的天然气-汽油混合物改装后的天然气/汽油双燃料 SI 发动机的燃烧行为和排放特性

摘要 通过在进气歧管处增加NG喷射系统，将基准汽油机改装为天然气（NG）/汽油双燃料发动机。研究了具有不同比例的天然气-汽油混合物的发动机的燃烧行为和排放特性。在一台4缸SI发动机上进行了数值模拟和实验验证。结果表明，天然气/汽油双燃料发动机的燃烧行为和排放特性介于汽油和天然气之间。最大缸内压力（MCP）、最大放热率（MHRR）和最大压力上升率（MPRR）随着NG比的增加而降低，燃烧阶段（CA10和CA50）延迟，这意味着在汽油中加入天然气可以有效提高发动机的抗爆震性，从而可以通过提高压缩比来提高热效率。最高燃烧温度（MCT）和总的总当量比随着 NG 比的增加而增加，导致 NO 和烟尘排放增加，但在 50% NG 比（按能量）时，NO 和烟尘排放的增加比例为分别低于纯汽油模式的 8.7% 和 17.3，但同时指示热效率 (ITE) 增加，CO、CO2 和 HC 减少，这意味着热效率和通过使用 50% 的 NG 和 50% 的汽油（按能量）运行发动机而排放 NOX，而不会导致进一步的成本和复杂性。这允许通过增加压缩比来提高热效率。最高燃烧温度（MCT）和总的总当量比随着 NG 比的增加而增加，导致 NO 和烟尘排放增加，但在 50% NG 比（按能量）时，NO 和烟尘排放的增加比例为分别低于纯汽油模式的 8.7% 和 17.3，但同时指示热效率 (ITE) 增加，CO、CO2 和 HC 减少，这意味着热效率和通过使用 50% 的 NG 和 50% 的汽油（按能量）运行发动机而排放 NOX，而不会导致进一步的成本和复杂性。这允许通过增加压缩比来提高热效率。最高燃烧温度（MCT）和总的总当量比随着 NG 比的增加而增加，导致 NO 和烟尘排放增加，但在 50% NG 比（按能量）时，NO 和烟尘排放的增加比例为分别低于纯汽油模式的 8.7% 和 17.3，但同时指示热效率 (ITE) 增加，CO、CO2 和 HC 减少，这意味着热效率和通过使用 50% 的 NG 和 50% 的汽油（按能量）运行发动机而排放 NOX，而不会导致进一步的成本和复杂性。