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Abstract

The characteristic flame behaviors and velocity fields of a plane-jet flame modulated by a fluidic oscillator were experimentally studied. The flame behaviors were observed by the traditional photographic technique. The time-averaged velocity fields of the jet flame were measured by a high-speed particle image velocimeter. The temperature distributions of the jet flame were measured by an R-type thermocouple. The pulsating reacting jets issued from the side slots of the fluidic-oscillator burner formed two diffusion flames. By observing the flame behavior at around burner exit, three characteristic flame modes: attached flame, transitional flame, and lifted flame, were identified in the domain of central jet Reynolds number and coflowing air jets Reynolds number. The time-averaged velocity field showed that a source point is formed in the wake of the target blockage. Above the source point, the flow goes downstream direction. Beneath the source point, the flow reverses toward upstream direction, and then forms a reverse flow region. Two adjacent vorticity-concentrated areas with opposite signs were formed around the region where the pulsating fuel jet interacts with the coflowing air jets. The increase of pulsating jet velocity asserted a large momentum impinging on the coflowing air jets, therefore caused the coflowing air jets to deflect toward transverse direction. The axial velocity, turbulence intensity, and temperature distributions of the lifted flame mode presented larger values than those of the attached flame and transitional flame modes

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