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arXiv · 2210.06953

Mechanism of Cold-spot Autoignition in a Hydrogen/Air Mixture

Dimitris M. Manias·Aliou Sow·Efstathios-Al. Tingas·Francisco E. Hernandez Perez·Hong G. Im·Dimitris A. Goussis
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Abstract

When designing high-efficiency spark-ignition (SI) engines to operate at high compression ratios, one of the main issues that have to be addressed is detonation development from a pre-ignition front. In order to control this phenomenon, it is necessary to understand the mechanism by which the detonation is initiated. The development of a detonation from a pre-ignition front was analyzed by considering a one-dimensional constant-volume stoichiometric hydrogen/air reactor with detailed chemistry. A spatially linear initial temperature profile near the end-wall was employed, in order to account for the thermal stratification of the bulk mixture. A flame was initiated near the left wall and the effects of its propagation towards the cold end-wall were analyzed. Attention was given on the autoignition that is manifested within the cold-spot ahead of the flame and far from the end-wall, which is followed by detonation. Using CSP tools, the mechanism by which the generated pressure waves influence the autoignition within the cold-spot was investigated. It is found that the pressure oscillations induced by the reflected pressure waves and the pressure waves generated by the pre-ignition front tend to synchronize in the chamber, increasing the reactivity of the system in a periodic manner. The average of the oscillating temperature is greater in the cold-spot, compared to all other points ahead of the flame. As a result, the rate constants of the most important reactions are larger there, leading to a more reactive state that accelerates the dynamics of the cold-spot and to its autoignition.

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Dimitris M. Manias, Aliou Sow, Efstathios-Al. Tingas, Francisco E. Hernandez Perez, Hong G. Im, Dimitris A. Goussis. 2022-10-13. Mechanism of Cold-spot Autoignition in a Hydrogen/Air Mixture. https://arxiv.org/abs/2210.06953

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