Investigation of ignition delay times of oxygen-enriched methane mixtures using a rapid compression machine
(2026) Proceedings of the Combustion Institute — Vol. 42, p. 106758 (2026)
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- Authors
Parente, Alessandro 
Murakami, Yuki
- Abstract
- This work investigates the effects of oxygen (O 2) enrichment on ignition delay times of methane (CH 4) using a rapid compression machine (RCM) at low-to-intermediate temperatures and high-pressure conditions, aiming at internal combustion engine applications. O 2 percentages in the oxidiser range from 21% to 100% at a fixed fuel volume. Experimental measurements indicate that the ignition delay times of CH 4 monotonically decrease as the O 2 concentration increases at a fixed temperature. To accurately simulate the ignition phenomena of O 2-enriched mixtures in a RCM, a ''pseudo'' non-reactive pressure-time history, created based on reactive test data, is used to consider the facility effects. By using the simulation input based on a pseudo non-reactive pressure profile, the ignition delay times are accurately simulated with a recent detailed chemical kinetic mechanism. Chemical kinetic analyses reveal that the observed enhancement in mixture reactivity is due to strengthened pathways involving methylperoxy radicals (CH 3Ȯ2). The findings obtained in the present study advance the application of O 2-enriched CH 4 combustion and the ignition control for practical internal combustion engines. Novelty and significance statement: The present work makes three main contributions: (1) a new set of ignition delay time (IDT) measurements for CH 4 mixtures at O 2-enriched conditions; (2) the demonstration of the RCM simulations using a ''pseudo'' non-reactive pressure-time history; and (3) a detailed chemical kinetic analysis of O 2-enriched CH 4 combustion without dilution at engine-relevant conditions. First, this study presents experimental and numerical investigations of IDTs for O 2-enriched CH 4 mixtures for the conditions which have scarcely been examined using RCMs. The new experimental datasets extend the benchmarks for validation and further development of chemical kinetic mechanisms. Second, the introduction of a pseudo non-reactive pressure profile in RCM simulation is key to accurately consider the facility effects, especially when the O 2 concentration in the oxidizer is varied. The proposed approach is broadly applicable to RCM studies involving variations in oxidizer composition. Third, the chemical kinetic analysis clarifies the mechanisms responsible for the enhanced reactivity of CH 4 mixtures for oxy-fuel conditions across a wide range of O 2 concentrations, providing insights relevant to high-compression-ratio, low-temperature combustion engine applications.
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Citations
Spano, S., Hurault, F., Foucher, F., Parente, A., Coussement, A., Contino, F., Jeanmart, H., & Murakami, Y. (2026). Investigation of ignition delay times of oxygen-enriched methane mixtures using a rapid compression machine. Proceedings of the Combustion Institute, 42, 106758. https://doi.org/10.1016/j.proci.2026.106758 (Original work published 2026)