Oscillating Jet Diffusion Flames in Triple Port Burner

Labscale jet diffusion flame stabilized in a triple port (TP) burner with central Oxidizer (air) jet, annular Fuel jet and outer annular Oxidizer (air) jet is investigated in the present work. This jet diffusion flame is referred here as the TP-OFO flame. Particularly, the effect of central air jet velocity on the visible flame morphology evolution, natural oscillation characteristics and oscillation suppression mechanism in buoyant TP-OFO flame established with fixed annular fuel jet and outer annular air jet velocities is analyzed through experiments and numerical simulations. The variation in central air jet velocity resulted in the realization of three distinct types of periodically oscillating buoyant TP-OFO flames (referred to as Type-1, Type-2 and Type-3 flames in this work). The Type-1 flame features a distinguishable double reaction zone with an oscillating inner and outer flames both of which remain anchored to the burner rim. The Type-2 flame is a unique variant comprising an oscillating inner lifted flame enveloped by a burner rim-anchored oscillating outer flame, whereas in the Type-3 flame, the inner and outer oscillating reaction zones appear merged. Experiments further revealed a critical central air jet velocity beyond which the periodic oscillations in buoyant TP-OFO flame get suppressed for a fixed power level and outer annular air jet velocity. Numerical simulations performed using the LaminarSMOKE reacting flow solver revealed that central air jet velocity assists in the oscillation suppression of buoyant TP-OFO flame by reducing the radial density gradients surrounding the flame zone and minimizing the flame-toroidal vortex interaction. Finally, a new velocity parameter that predicts the critical central air jet velocity for oscillation suppression in buoyant methane TP-OFO flames is proposed.