Effect of Pre-Chamber Geometry on Methanol Cold-Start Combustion in an SI Engine

2026-01-0307

4/7/2026

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Abstract
Content
Vehicle pollutant emissions are a major challenge in the development of internal combustion engines. To meet increasingly strict regulations, the automotive sector is exploring alternative fuels and lean-burn strategies. Methanol is gaining importance as a carbon-neutral fuel due to advances in green production technologies. Methanol, despite its potential for renewable production, faces severe limitations due to its inherent poor cold-start performance with conventional ignition systems. In this context, the present study aims to investigate the influence of pre-chamber ignition on cold-start combustion by using high-speed optical diagnostics to visualize flame propagation while simultaneously measuring in-cylinder pressure and engine performance. A major result concerns the significant cyclic variability of conventional spark ignition (SI) under cold-start conditions, which exhibits significant cyclic variability. Instead, passive pre-chamber ignition significantly enhances cold-start combustion stability, lowering CoV IMEP to below 3% at λ = 1.0 and sustaining stability under 5% even in ultra-lean conditions (λ = 1.6), where conventional SI operation fails. Flame visualization quantitatively confirms that this stability stems from distributed, multi-point ignition, which accelerates initial flame propagation by 3-4x compared to SI. These findings demonstrate that pre-chamber ignition can effectively overcome the traditional "cold-start" problem for methanol, enabling stable combustion from the first cycles. This provides an invaluable dataset for CFD model validation, as it captures a highly stable combustion process largely independent of the adverse thermal boundary conditions typical of cold start, thereby simplifying the modeling challenge.
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DOI
https://doi.org/10.4271/2026-01-0307
Citation
Sementa, P., Altieri, N., and Tornatore, C., "Effect of Pre-Chamber Geometry on Methanol Cold-Start Combustion in an SI Engine," WCX SAE World Congress Experience, Detroit, Michigan, United States, April 14, 2026, https://doi.org/10.4271/2026-01-0307.
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Publisher
Published
Apr 07
Product Code
2026-01-0307
Content Type
Technical Paper
Language
English