Experimental Study of the Flame Structural Characteristics and Self-Similar Propagation of Syngas and Air Turbulent Expanding Premixed Flame

In order to study the structural characteristics and self-similar propagation of a syngas/air mixture turbulent expanding premixed flame, experimental studies under various equivalent ratios (0.6, 0.8, and 1.0) and hydrogen fractions (20%, 40%, and 60%) were carried out. The effects of the hydrogen fractions and equivalence ratios on the local radius and pulsation radius of the flame front were studied, and perturbations at different flame positions were quantitatively analyzed. The correlation between flame structure and initial flame structure during flame propagation was analyzed, and the self-similarity of syngas/air mixture turbulent premixed flames at different hydrogen fractions and equivalence ratios was also analyzed. The results showed that the fluctuation of the ratio of the pulsation radius to the area equivalence radius at the flame front notably increased with increasing hydrogen fraction, and the correlation coefficient of the flame front decreased at the same radius. Although the equivalence ratio increased, the standard deviation of the pulsation radius decreased at the same radius, and the degree of uniformity of the flame front decreased as well. The accelerated propagation process of the flame had self-similar characteristics. The Reynolds number of the fit index of the dimensionless propagation speed decreased from 0.45 to 0.30 with increasing hydrogen fraction. When the equivalence ratio increased, the fit index decreased from 0.41 to 0.31.