Experimental and Numerical Study of Autoignition/Deflagration Transition Limit in a Flat Piston Optical Rapid Compression Machine

ABSTRACT

This work investigates the transition limit between autoignition front and deflagration in hot and premixed conditions. In particular, the objective is to analyze the sensitivity of the combustion regime to the temperature gradient, mixture composition and thermodynamical conditions, which is first analyzed numerically. The results are then compared to experimental data obtained in an optical RCM, fitted with a flat piston and a multi-zone heating system. Temperature gradient after compression is measured in the hot core region using two thin wire thermocouples of about 7.6 µm diameter. The chemiluminescence records confirm that the dynamics of autoignition fronts is strongly dependent on (i) the gaseous mixture composition and the thermodynamical conditions, and (ii) on thermal gradients in the unburned mixture. In particular, the authors evidence experimental conditions for which a steeper gradient or a change in mixture composition leads to a transition from autoignition to deflagration.

KEYWORDS:

• Autoignition
• deflagration
• RCM
• temperature gradient

Acknowledgements

This work was supported by the CPER FEDER Project of Région Nouvelle Aquitaine and by the French Ministry for Higher education and Research. It pertains to the French government program “Investissements d’Avenir” (EUR INTREE, reference ANR-18-EURE-0010).

The authors thank Herve Arlaud and Gildas Lalizel for providing the thin-wire thermocouples to measure the temperature and thank Alain Claverie for providing assistance during experiments.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00102202.2023.2182200

Additional information

Funding

The work was supported by the French Ministry for Higher education and Research (PhD Grant).