Mitigating climate change involves the greater adoption of carbon–neutral and renewable energy sources within the transportation sector. Ammonia (NH), as a carbon-free and sustainable fuel, has garnered growing interest in recent years. The present study aims to investigate the impact of NH blending on combustion and emission characteristics of a stoichiometric spark-ignition gasoline engine, with a particular emphasis on nitrogen-based emissions. The experimental investigation was complemented by chemical kinetic calculations. The results showed that NH blending could effectively suppress engine knock, optimize combustion phase and improve thermal efficiency. For pure gasoline, advancing the spark timing resulted in increased NO emissions. However, when NH was blended, NO emissions decreased with advancing spark timing, indicating a negative correlation with pressure. The NH emission was attributed to the ‘crevice mechanism’ as well as the absorption/desorption in the lubricant oil film on the cylinder wall. Chemical kinetic analysis revealed that the NO emission from NH blended combustion is closely related to reactive radicals such as OH, H and O. The reduction in NO emissions under high-pressure conditions was primarily attributed to the consumption of these reactive radicals via three-body reactions. Interestingly, NO emissions initially increased with increasing NH blending ratio but eventually followed a decreasing trend. This can be attributed to the lower combustion temperature, lower concentration of reactive radicals, and enhanced de-NO reactions.

中文翻译：

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汽油/氨燃料 SI 发动机的燃烧和排放特性以及 NOx 排放的化学动力学分析

缓解气候变化需要在交通运输领域更多地采用碳中和和可再生能源。氨（NH）作为一种无碳且可持续的燃料，近年来引起了越来越多的关注。本研究旨在研究 NH 混合对化学计量火花点火汽油发动机的燃烧和排放特性的影响，特别是氮基排放。化学动力学计算补充了实验研究。结果表明，NH混合能够有效抑制发动机爆震，优化燃烧相，提高热效率。对于纯汽油，提前火花正时会导致氮氧化物排放量增加。然而，当混合 NH 时，NO 排放量随着火花正时的提前而减少，这表明与压力呈负相关。 NH 排放归因于“缝隙机制”以及气缸壁润滑油膜的吸收/解吸。化学动力学分析表明，NH混合燃烧的NO排放与OH、H和O等活性自由基密切相关。高压条件下NO排放的减少主要归因于这些活性自由基通过三体消耗反应。有趣的是，NO 排放量最初随着 NH 混合比例的增加而增加，但最终呈下降趋势。这可归因于较低的燃烧温度、较低的活性自由基浓度以及增强的脱NO反应。