Impact of gasoline composition on the effects of nitric oxide on autoignition and knock in a DISI engine

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame Pub Date : 2025-08-29 DOI:10.1016/j.combustflame.2025.114367

Namho Kim , Magnus Sjöberg , Dario Lopez-Pintor , Naoyoshi Matsubara , Koji Kitano , Ryota Yamada , Chiara Saggese

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引用次数: 0

Abstract

Modern spark-ignition engines use exhaust gas recirculation (EGR) to dilute the charge and suppress knock, enabling the use of higher compression ratios and/or more optimum combustion phasing for higher efficiency. The effectiveness of EGR is affected by the composition of the fuel and its chemical-kinetic interactions with combustion products. Among those, nitric oxide (NO) has been shown to strongly affect autoignition reactivity. However, the impact of fuel composition of the effect of NO on reactivity is not well-understood.

In this study, engine experiments were conducted to assess the impact of NO seeded to the intake on knock-limited operation of two gasoline fuels (high cycloalkane content, or HCA, and high olefin content, or HO). Results showed that compositionally-different fuels responded differently to NO. HCA, which was less knock-limited than HO for NO < 200 ppm, became more knock-limited for NO > 200 ppm. Moreover, it was found that differences in knock between fuels were caused by differences in autoignition chemistry and not in the sequential autoignition process of the end gas that occurs due to thermal stratification. Chemical kinetic simulations were performed to better understand the experimental results. For HCA, intermediate-temperature heat release had a greater impact on autoignition reactivity than low-temperature heat release, while the opposite was observed for HO. For both fuels, NO enhances the magnitude of low-temperature heat release via NO + HO₂ → NO₂ + OH. The effect of NO on reactivity was stronger for HCA because OH produced from NO helped to overcome the OH quenching effect of cyclopentane, a main species in HCA. In contrast, HO had relatively strong inherent low-temperature chemistry arising from iso-octane, which reduced the impact of NO on reactivity. For the range of NO mole fractions tested in this study, in-cylinder NO increased fuel’s knock propensity, especially for fuels with mild low-temperature chemistry.

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汽油成分对一氧化氮对DISI发动机自燃和爆震影响的影响

现代火花点火发动机使用废气再循环（EGR）来稀释装药和抑制爆震，从而能够使用更高的压缩比和/或更优化的燃烧相位来提高效率。EGR的有效性受燃料组成及其与燃烧产物的化学动力学相互作用的影响。其中，一氧化氮（NO）已被证明对自燃反应性有强烈影响。然而，燃料成分对NO的影响对反应性的影响尚不清楚。在本研究中，我们对发动机进行了实验，以评估在进气中添加NO对两种汽油燃料（高环烷烃含量（HCA）和高烯烃含量（HO））的冲击限制运行的影响。结果表明，不同成分的燃料对NO的反应不同。当NO <； 200ppm时，HCA的敲限比HO低，而当NO <； 200ppm时，HCA的敲限则更高。此外，还发现不同燃料之间爆震的差异是由自燃化学性质的差异引起的，而不是由热分层引起的末端气体的顺序自燃过程引起的。为了更好地理解实验结果，进行了化学动力学模拟。对于HCA，中温放热对自燃反应性的影响大于低温放热，而对于HO则相反。对于这两种燃料，NO通过NO + HO2→NO2 + OH来增强低温放热的强度。NO对HCA反应活性的影响更大，因为NO产生的OH有助于克服HCA中主要物质环戊烷的OH猝灭作用。相反，HO具有较强的由异辛烷产生的固有低温化学性质，这降低了NO对反应性的影响。在本研究测试的NO摩尔分数范围内，缸内NO增加了燃料的爆震倾向，特别是对于具有轻度低温化学性质的燃料。

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来源期刊

Combustion and Flame 工程技术-工程：化工

CiteScore

9.50

自引率

20.50%

发文量

631

审稿时长

3.8 months

期刊介绍： The mission of the journal is to publish high quality work from experimental, theoretical, and computational investigations on the fundamentals of combustion phenomena and closely allied matters. While submissions in all pertinent areas are welcomed, past and recent focus of the journal has been on: Development and validation of reaction kinetics, reduction of reaction mechanisms and modeling of combustion systems, including: Conventional, alternative and surrogate fuels; Pollutants; Particulate and aerosol formation and abatement; Heterogeneous processes. Experimental, theoretical, and computational studies of laminar and turbulent combustion phenomena, including: Premixed and non-premixed flames; Ignition and extinction phenomena; Flame propagation; Flame structure; Instabilities and swirl; Flame spread; Multi-phase reactants. Advances in diagnostic and computational methods in combustion, including: Measurement and simulation of scalar and vector properties; Novel techniques; State-of-the art applications. Fundamental investigations of combustion technologies and systems, including: Internal combustion engines; Gas turbines; Small- and large-scale stationary combustion and power generation; Catalytic combustion; Combustion synthesis; Combustion under extreme conditions; New concepts.