5. Stabilizing diffusion flames

Up to now, we've mainly analyzed the structure of established laminar diffusion flames, without looking at their initiation or the stabilization mechanisms that allow them to persist. In practice, flame initiation requires an external energy input from, for example, a small auxiliary flame (match) or the spark from a spark plug. But this energy is usually only supplied for a limited time. After that, the flame must remain stable without any external source of energy, otherwise it will go out. Analysis of flame stabilization mechanisms is therefore extremely important in practice: a flame that goes out unexpectedly not only no longer fulfills its mission (what about an aircraft engine that goes out in flight?), but can also lead to serious subsequent problems (explosion) if the flow of reagents is not stopped... The main stabilizing mechanisms of diffusion flames will now be briefly described....