Abstract

Cool flames are a distinctive low-temperature combustion regime in which a fuel undergoes partial oxidation, leading to a moderate temperature rise and weak visible light emission. Although historically regarded as a curiosity, cool flames are now recognized as a key phenomenon for understanding auto-ignition processes in the oxidation of a variety of chemicals, with important implications for engine combustion and safety in reactive systems.

This presentation provides an introductory and mechanistic overview of cool flames, focusing on the chemical kinetics governing low-temperature oxidation. The main classes of reactions involved, such as the formation and evolution of peroxy (RO₂) radicals, will be presented in a step-by-step manner to clarify how heat release can occur without the development of a classical high-temperature flame. The concept of degenerate chain branching will also be introduced.

Experimental signatures of cool flames and their transition toward hot ignition will be illustrated using representative examples from laboratory reactors and numerical simulations. The presentation concludes with a discussion of why cool flames matter for modern combustion technologies and the challenges they pose for kinetic modeling and control.

Biography

Prof. Guillaume Dayma has been professor at the University of Orléans since 2012. He obtained his PhD from the Institut National Polytechnique de Lorraine (Nancy, France) in 2003. He was a post-doc fellow at the Institute for Aerospace Studies (University of Toronto, Canada). He started as assistant professor at Pierre and Marie Curie University (now Sorbonne University, Paris, France) from 2006 to 2009 before moving to Orléans. His research activities aim at understanding the chemical phenomena during combustion. He develops detailed chemical kinetic mechanisms for a variety of fuels. He is also teaching Physical Chemistry, Thermochemistry and Kinetic Mechanism Development at the University of Orléans. He is the author of more than 120 publications in peer-reviewed scientific journals.

He was elected Fellow of the Combustion Institute for significant contribution to the experimental and modeling study of the combustion chemistry of oxygenated fuels in 2023 and obtained the Research Excellence Award for high-impact scientific contributions in 2020.

He served as Colloquium co-Chair of the Gas Kinetic section of the 38^th International Symposium on Combustion and was chairman of the organizing committee of the 11^th International Conference on Chemical Kinetics in Orléans in 2019. 

Personal links: https://www.univ-orleans.fr/fr/groupe-combustion/hydrocarbons