Measurement of ultrafast combustion process of premixed ethylene/oxygen flames in narrow channel with digital holographic interferometry.

The premixed ethylene and oxygen flame that is burning in a narrow channel is investigated with digital holographic interferometry (DHI). Combustion in either a narrow tube or channel is quite different. This is caused by the significant effects of the boundary layer. The flame's acceleration rate will be enhanced as the tube diameter decreases. Usually, flame and shock wave propagation, which occurs during the premixed ethylene/oxygen flame combustion in the measurement area, is less than few milliseconds, so that general camera can rarely capture this fast event. This paper demonstrates that, by introducing the high-speed camera to DHI, the propagation of weak compression wave, flame, and shock wave generated in the narrow channel is successfully measured with a temporal resolution of 10 μs. The ultrafast processes of the flame front changing, as well as the shock wave coupling and separating, are clearly shown from the reconstructed phase distributions of the recorded holograms; corresponding density variations are simultaneously calculated. The results could provide references for the micro-scale propulsion and power devices design and use, and this proposed configuration can also easily adapt to other kinds of ultrafast processes in fluids.