Local chemiluminescence measurements of OH*, CH* and C2* at turbulent premixed flame-fronts

Local chemiluminescence measurements of OH*, CH* and C-2* were carried out at the flame-front of a premixed turbulent methane flame to understand the details of the reaction zone and flame-front structures. Cassegrain optics were used to detect these chemiluminescences simultaneously. The developed system allows us to measure each chemiluminescence at high temporal resolution of 4 mus and high spatial resolution of 0.1 mm in diameter and 0.8 mm long. The relationship between the turbulent scale and the flame-front thickness was investigated by simultaneous measurements of these three chemiluminescences as well as those derived from LDV. It was found that the time series chemiluminescences could describe the flame-front duration and inter-arrival time, and that the variations in OH*, CH* and C-2* chemiluminescences occurred simultaneously, which indicates the strong relationship between OH* to CH* and OH* to C-2* reactions at the flame-front. Furthermore, the flame-front structure could be characterised by the time scales of chemiluminescence intensities, which was found to correspond to the flame-front thickness and the local Damkohler number. A new measurement technique to measure the local flame-front structure by means of local chemiluminescence measurements was proposed and its performance was proven.