Measurement of fuel concentration profile at leading edge of lifted flame with acetone laser-induced fluorescence

This research proposes a study of the leading edge of the methane-air triple flame characteristics. Few experiment results are available for physical examination, so an experimental investigation must be conducted to understand the stability mechanisms in a mixture with a steep concentration gradient. To this end, applying acetone-laser-induced fluorescence (acetone-LIF) is studied for measuring concentration profiles at the leading edge of the flame. The results demonstrate that the lifted height is changed when acetone is added to the mixture. It correlates closely with increasing C₂ radical behind the flame edge. Meanwhile, the OH radical luminous intensity measured with a spectroscope is not changed. Moreover, the burning velocity of methane-acetone-air mixture obtained by the Bunsen burner method remains constant. Therefore, the influence of acetone on burning intensity is small. Acetone LIF can thus be advantageous for measuring the local concentration gradient at the leading edge. The acetone LIF signals can be revised considering the thermal effect using the silicone oil vanishing plane. After temperature correction, the transition of the flammability limit width upstream of the flame at a steep concentration gradient can be observed as clearly as in the recent numerical result.