Combustion and flame propagation characteristics of toluene reference fuel in an optical GDI engine

Nan Wang, Saifei Zhang, Zhicheng Shi, Qianbo Sun and Han Wu

Energy, 2025, vol. 335, issue C

Abstract: The existing research on gasoline direct injection (GDI) engines mainly focuses on traditional macroscopic parameters, and limited visualization tests have not effectively elucidated the combustion characteristic, especially the matching of different parameters. Therefore, experiments are conducted in an optical GDI engine to explore the effects of spark timing, exhaust gas recirculation (EGR) and intake flow on combustion and flame propagation characteristics in a wide equivalence ratio range. The results show that for lean mixture, advance spark timing significantly improve combustion, but the opposite effect for rich mixture. At φ = 0.7, with the advance of spark timing from −5°CA ATDC to −15°CA ATDC, ignition starts earlier, and flame intensity, IMEP and combustion stability increase remarkedly. Furthermore, moderately increasing the equivalence ratio, such as φ = 1.0–1.4, can mitigate the weakening effect of EGR on combustion. At φ = 0.8 and φ = 1.6, with EGR increasing from 5 % to 15 %, the combustion duration is extended 2.9 and 1.1 times, respectively. However, this value is only 0.9 for φ = 1.2. In addition, for low intake flow, a lower equivalence ratio helps optimized combustion. At φ = 0.8, φ = 1.2 and φ = 1.6, with the intake flow decreasing from 88L/min to 66L/min, the combustion duration is shortened by 1.5°CA, lengthened by 4.6°CA and 31.8°CA.

Keywords: Combustion; Spark timing; EGR; Intake flow; Wide equivalence ratio range; GDI engine (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:335:y:2025:i:c:s036054422503779x

DOI: 10.1016/j.energy.2025.138137

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