Local Chemiluminescence Measurement of Turbulent Premixed Flame.

Abstract

A new technique for observing a local flame-front structure using local chemiluminescence measurements is proposed, and its performance is demonstrated. Local chemiluminescence measurements of OH*, CH* and C2* were carried out at the flame front of premixed turbulent propane/air flames (Re=14000, u'/SL<1.0, φ=1.1) to study details of the reaction zone and characteristics of turbulent flame-front structure. Cassegrain optics were developed to detect of these chemiluminescent emission intensities to obtain flame spectroscopic data for a local point. PIV was also applied to measure combustion flow characteristics. In this study, time-series signals of OH*, CH* and C2* were measured to understand those profile at the flame front with/without Cassegrain optics. These time-series data was analysed to understand turbulent characteristics in comparison with velocity data. The structure of the flame front can be characterized by the duration of the chemiluminescence intensity peak and by the patterns of its occurrence, which were found to correspond to the flame thickness and the Damkohler number. The relationship between turbulence scale and flame thickness at the flame front was investigated by simultaneous measurement of the three chemiluminescences and LDV. It was found that local chemiluminescence can provide useful information on the flame-front structure and its characteristics.