Local Quenching Recovery Processes of Premixed and Diffusion Interacting Flames in a Turbulent Opposite Flow

A lean premixed CH₄ air flame (LPF) impinges with a CH₄ diluted with N₂ diffusion flame (DF) having different turbulence conditions to create a lean heterogeneous combustion model such as a stratified combustion. The local quenching recovery processes of LPF and DF interacting with the turbulence in an opposed flow have been investigated experimentally using a Particle Image Velocimetry movie. The local quenching phenomena can be observed frequently with approaching the global extinction condition. The local quenching may trigger to global extinction. However, in many cases, the flame can recover from the local quenching phenomena and create the stable flame. There are three distinct local quenching recovery mechanisms namely a passive mode, an active mode, and an eddy transportation mode. These three modes depend on the local flame propagation mechanism, the bulk flow motion, and the eddy motion by turbulence. In the passive mode, the bulk flow plays an important role on the recovery process. The local quenching area is drifting outward from the stabilization point by the bulk flow and then, it is displaced by the stable flamelets. In the active mode, the local quenching area is recovered by the self-propagating wrinkled LPF from somewhere in the active zone. The active mode is observed only when the turbulence is added to the premixed flame side. In the eddy motion mode, the local quenching area is recovered by the eddy transportation. That is, the flamelet is transport by the eddy motion and the local quenching area is replaced. The wrinkled flamelet having self-propagation plays a very important role for the local quenching recovery mechanism. The turbulence on the premixed flame not only induces high possibility for the local quenching but also helps to recover from the local quenching.