Measurement of ultrafast combustion process of premixed ethylene/oxygen flames in a narrow channel by using digital holographic interferometry

The premixed ethylene and oxygen flame burning in a narrow channel is investigated by using digital holographic interferometry (DHI). Combustion in a narrow tube or channel is quite different owing to the significant effect of the boundary layer and the flame acceleration rate will be enhanced as the tube diameter decreases. Usually, the propagation of flame and shock wave 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 at once. In this paper, by introducing high speed camera to DHI, the propagation of weak compression wave, flame and shock wave generated in the narrow channel are successfully measured with a temporal resolution of 10 µs. The ultrafast processes of the flame front changing and shock wave coupling and separating are clearly shown from the reconstructed phase distributions of the recorded holograms, and corresponding density variations are simultaneously calculated. The results could provide references for the micro-scale propulsion and power devices designing and utilizing, and this proposed configuration can also adapt to other kinds of ultrafast process in fluids easily.