An Experimental Study on the Lift-off Characteristics of the Triple Flame within a Diverging Channel

Abstract

The lift-off characteristics of the triple flame within a diverging channel have been studied experimentally using a multi-slot burner. This burner can produce a lifted triple flame by controlling strictly the concentration gradient and the mean velocity. In this experiment, the triple flame was stabilized in lift-off condition within a diverging channel and lift-off heights, axial velocity variation, and some other characteristics of the triple flame were examined. It was also investigated that the effects of low concentration gradient and mean velocity change on the triple flame. Methane/air and propane/air flames for various mean velocities had similar trend; they had minimum lift-off height at a certain concentration gradient. This means that the propagation velocity of the flame becomes maximum at a certain concentration gradient. Flammable limit of premixed flame and the diffusion flame behind the premixed flame makes propagation velocity of triple flame fast in very low concentration gradient condition.