Effects of Local Flame Displacement Velocity on Turbulent Burning Velocity for Stoichiometric H₂-O₂-Ar Mixtures

Abstract

This study was made to establish a prediction method of turbulent burning velocity for stoichiometric hydrogen-oxygen-argon mixtures, with paying special attention to the importance of local burning velocity to turbulent burning velocity. In this study, stoichiometric mixtures with different dilutions, whose laminar burning velocity S_L0 was varied from 25 to 90 cm/s, were used under almost the same weak turbulence condition, so that the ratio of turbulence intensity u' to S_L0 becomes 0.4 to 2.0. Nitrogen was also used as a conventional dilution gas for comparison with argon. A two-dimensional sequential laser tomography technique was applied to obtain the relationship between the flame shape and the flame displacement in a constant-volume vessel. The local flame displacement velocity S_F of turbulent flames was quantitatively measured as the key parameter of local burning velocity. It was found that the trends of the mean values of S_F, S_F,m, against u'/S_L0 corresponded well to its turbulent burning velocities, but S_F,m did not increase infinitely with increasing u'/S_L0. The turbulent burning velocity also attempted to be predicted by some empirical equations. As a result, the predicted turbulent burning velocities, where the obtained S_F,m was employed instead of S_L0 as the local burning velocity, were in good agreement with experimental ones.