Effect of hydrogen addition on turbulent burning characteristics of lean premixed V-shaped CH4-air flames
Résumé
The effect of hydrogen addition on turbulent combustion characteristics of premixed CH4-air flames was investigated by laser tomography visualization method using a V-shaped flame configuration. Turbulent burning velocities were measured and the variation of flame surface characteristics due to hydrogen addition was analyzed. The results show that hydrogen addition causes an increase in turbulent burning velocity for lean CH4-air mixture at a constant equivalence ratio and similar turbulent level. The increase rate of turbulent burning velocity is higher than that of the corresponding laminar burning velocity, which suggests that the increase in turbulent velocity due to hydrogen addition is caused by not only chemical kinetics effect, but also turbulence itself. The further analysis of flame surface characteristics and brush thickness indicate that hydrogen addition slightly decreases local flame surface density, but increases total flame surface area because of the increased flame brush thickness. As a result, turbulent burning velocity is intensified by the increase in total flame surface area and the increased laminar burning velocity, when hydrogen is added.