SINOPSIS

The stability of a non-premixed turbulent flame formed in a backward-facing step flow and the turbulence characteristics of the velocity and thermal fields were investigated experimentally. The results showed a close relation between flame stability and instantaneous behaviors of the thermal field. Combustion was stabilized by high-temperature gas moving into the recirculation zone from the downstream region along a step-side wall, and this behavior was synchronized with the motion of fresh air supplied from the main stream to the recirculation zone. As the fuel flow rate is lowered, a flow with the characteristics of an isothermal flow is to interrupt the combusting field frequently. If the appearance frequency of such events exceeds a given criterion, an essential mechanism for maintaining combustion begins to collapse.