Extinction and Flame Front Behavior of Ultra Lean Premixed Flame Formed in Opposite Flow.

Abstract

Extinction and flame front behavior of ultra lean premixed flames of propane/air and methane/air mixtures formed in opposite turbulent flow have been studied experimentally. Extinction limits, velocity profiles and time series flame front movement in the near extinction limits have been measured and the extinction mechanism has been discussed. The distance of hot and cold boundaries between the upper flow and the lower flow are increased due to turbulent burning velocity. Furthermore, the flame stretch duo to flame wrinkling as well as the turbulent flame motion also affect to the flame extinction. Therefore, the extinction limit increases with increase in the turbulence. Extinction limits of the propane-air flame depend on the more concentrated burner condition regardless of the less concentrated burner condition. The methane-air ultra lean mixture could be react impinging to the high temperature burnt gas and the stable region extends to the lower fuel concentration zone. The characteristics of hot and cold boundary movement remarkably change with the concentration of the premixed gas even when the turbulence conditions of the approach flows are equal.