Assessment of burner structure for methane-oxygen inverse diffusion flame based on laser detection: Reaction characteristics and soot analysis

The structure of a burner is a key issue of boilers and gasifiers in several industries. It significantly influences the flame formation and combustion reaction determining the mixing degree of fuel and oxidant. This study aims to explore the characteristics of flames at different angles and evaluate their advantages in specific applications. The present work explores the correlation between laser-induced breakdown threshold energy and flame temperature based on laser-induced breakdown spectroscopy (LIBS). Subsequently, the local structure and reaction characteristics of the flame at different burner angles (45, 60 and 90°) were investigated with simulation. The local equivalence ratio of the laminar flame was used to determine the distribution of reactants and components in the flame. The results indicated that the breakdown threshold energy was positively correlated with the temperature of the flame, and it was dependent on the gas concentration. With increased laser energy, the O/H ratio could be used as a function of the local equivalence ratio of the flame. In addition, the study of flame images and the spontaneous radiation of soot revealed that the C/H ratio in the flame reached the maximum value when the burner incident angle was 45°. Through simulation and experimental research, we found that the flame at 60° angle is the most stable, produces the least soot, has the highest combustion efficiency, and has better thermal radiation intensity.