Dynamics of flame initiation, propagation, and transition to detonation

Abstract

Understanding of flame initiation, propagation, and transition to detonation is vital for both fundamental combustion science and practical applications, including the development of high-performance engines and the enhancement of explosion safety. This paper reviews recent progress in the flame dynamics and critical physical conditions governing these interconnected processes, focusing on laminar, premixed, gaseous mixtures. First, recent advances in forced ignition of premixed flames are reviewed, with an emphasis on theoretical analysis of critical ignition radius and minimum ignition energy. The effects of low-temperature chemistry and imposed flow on forced ignition of premixed flames are also discussed. Subsequently, flame propagation into autoigniting mixtures is addressed. Under engine-relevant high-temperature and high-pressure conditions, the ignition delay of the end-gas can become comparable to the flame transit time, leading to end-gas autoignition, autoignition-assisted flames, and cool flame development and transition to hot flame. Finally, the dynamics of autoignition-induced transition to detonation are analyzed, with a focus on the mechanism for detonation development in autoigniting mixtures. Throughout the paper, the continuous physical chain—from ignition kernel initiation to flame propagation and ultimately to detonation transition—is emphasized.

Novelty and significance statement: This review uniquely connects forced ignition, flame propagation into autoigniting mixtures, and transition to detonation. It presents recent theoretical advances in premixed flame ignition, end-gas autoignition, and detonation development. The role of low-temperature chemistry in reducing ignition energy, enabling flame propagation, and promoting detonation development is highlighted. The paper also discusses flow-facilitated ignition, autoignition-assisted flame speed scaling, and practical implications for detonation development in engines, thereby offering a systematic foundation for controlling extreme combustion events.