The shape and fluctuation of hydrogen-propane-butane-air lean premixed flames formed on a flat flame burner

Abstract

In this paper, the characteristics of hydrogen-propane-butane-air lean premixed flames on a flat flame burner were experimentally studied. To elucidate the shape and fluctuation of premixed flames, the cell width, RMS of fluctuation, peak frequency and reconstructed attractor were obtained from the direct photographic images and time series of light emission intensity. The cellular flames were observed at sufficiently low equivalence ratios; the flat flames were found under the other conditions. When the concentration of hydrogen was higher, the flat flames were formed at lower equivalence ratios. As the equivalence ratio became lower, the cell width and RMS increased in the range of cellular flames, which was due to high instability level. At low (high) equivalence ratios, moreover, the size of attractor was large (small) and the trajectory was unstable (quasi periodic). The experimental results revealed the instability characteristics of hydrogen-propane-butane-air lean premixed flames, and the obtained findings were applicable to the safe control of lean premixed flames.