Abstract

The aim of this work is to exploit the influence of using ozonized air to achieve stable and efficient combustion of lean mixtures in a gasoline-fuelled Spark-Ignition (SI) engine. The influence of ozone on the combustion of near-stoichiometric mixtures, which are typical of SI engines, has also been assessed. A Computational Fluid Dynamics (CFD) model has been employed to simulate compression, combustion, and expansion of a spark ignition, axisymmetric engine fuelled with iso-octane/air/ozone mixtures. The aim is to assess how ozone improves the engine performance under different engine speeds, ignition timings and equivalence ratios. The model has been validated against experimental data available in the literature. Parametric analyses have been carried out by considering three values of engine speeds (800, 1000 and 1200 rpm), three different ozone concentrations at Intake Valve Closure (IVC) (0, 100 and 200 ppm) and two equivalence ratios (0.9 and 0.7). The results show that ozone enables reactions in the Low Temperature Combustion (LTC) regime, modifies the mixture chemical composition and the auto-ignition tendency. Specifically, for all the cases under examination, the addition of ozone to the air/fuel mixture reduces the combustion duration, leading to an increase in terms of work output and a reduction of the specific fuel consumption. Moreover, the advantage of using ozone is greater for lean mixtures than for near-stoichiometric mixtures. Finally, for the near-stoichiometric cases, when the residence time of the mixture is high enough, auto-ignition occurs in the end gases.

中文翻译：

---

臭氧对燃烧影响的数值研究，以提高火花点火发动机的性能

摘要

这项工作的目的是利用臭氧化空气的影响来实现汽油燃料火花点火（SI）发动机中稀薄混合物的稳定和高效燃烧。还评估了臭氧对近化学计量混合物（SI 发动机的典型特征）燃烧的影响。计算流体动力学 (CFD) 模型已用于模拟以异辛烷/空气/臭氧混合物为燃料的火花点火轴对称发动机的压缩、燃烧和膨胀。目的是评估臭氧在不同发动机转速、点火正时和当量比下如何改善发动机性能。该模型已根据文献中提供的实验数据进行了验证。通过考虑发动机转速的三个值（800、1000 和 1200 rpm）、进气阀关闭 (IVC) 时的三个不同臭氧浓度（0、100 和 200 ppm）以及两个当量比（0.9 和 0.7）进行参数分析。 。结果表明，臭氧能够在低温燃烧 (LTC) 状态下进行反应，改变混合物的化学成分和自燃倾向。具体来说，对于所有正在检查的情况，在空气/燃料混合物中添加臭氧会减少燃烧持续时间，从而导致功输出增加并降低燃料消耗率。此外，使用臭氧对于贫混合物的优势比对于接近化学计量的混合物的优势更大。最后，对于接近化学计量的情况，当混合物的停留时间足够长时，尾气中会发生自燃。