Flame structure and fuel reaction on a non-premixed shuttlecock-like conical burner

To promote the efficiency of non-premixed combustion, we designed slot structures with a simple geometry on the side of a conical burner named a shuttlecock-like conical burner. The slot structure which can introduce the air co-flow naturally into the cone instead of using other and complicated geometry is inspired from the particular shape of a shuttlecock serving as a missile in badminton sport. Therefore, the air co-flow not only produces a recirculation zone on the edge of the burner but also moves directly into the burner. The combustion condition transforms from non-premixed to partially premixed combustion; the mixing and reaction of fuel and oxidant are hence greatly enhanced. We observed the structures of the flame and the flow of a shuttlecock-like conical burner, and examined its reaction characteristics with measurements of the chemiluminescence of OH* and the flame temperature. The observation of an isothermal flow field demonstrates that the air co-flow moves directly into the burner via the slots. Double pairs of vortex structures are observed above the exit of the burner because the introduced air co-flow decreases the strength of the outer vortex, allowing the central jet to form an inner vortex. The reaction zone of a shuttlecock-like conical burner hence approaches not only the central region of the flame but also the burner exit. The reaction intensity of the fuel of a shuttlecock-like conical burner is also stronger than that of an ordinary conical burner (without the slots). The designed shuttlecock-like conical burner is significantly useful to serve as a reference to improve the combustion efficiency of non-premixed combustion.