Flame Initiation and Detonation Development in a Gaseous Premixture
Understanding the initiation of premixed flame and detonation is important not only for fundamental combustion research but also for developing advanced combustion engines and controlling of fire and accidental explosions. A premixed flame can be initiated when sufficient amount of external energy is locally deposited into a combustible mixture. Under engine-relevant conditions with high temperature and pressure, the ignition delay time of the unburned gas might be comparable to the characteristic flame time; and thereby strong flame/autoignition interaction occurs which might induce detonation development. In this talk, I will discuss the recent progress on flame initiation and detonation development in a gaseous flammable mixture. First, I will present the recent investigations on ignition kernel development, critical ignition radius and minimum ignition energy. I will discuss the effects of different factors including dilution, fuel stratification and turbulent transport on ignition of premixed flames. In the second part, I will present results on end-gas autoignition, flame/autoignition interaction, and detonation development under engine-relevant conditions. The end-gas autoignition and detonation development are respectively related to normal knock and super-knock in downsized and boosted spark ignition engines. Finally, I will briefly introduce the recent progress on detonation initiation and propagation in non-uniform mixtures, which might occur in rotating detonation engines.