Controlling Plane-Jet Flame by a Fluidic Oscillation Technique

A plane-jet flame was manipulated by passing the fuel jet through a jet-impingement fluidic oscillator. The plane fuel jet bifurcated into two streams of self-sustained pulsating jets in the cavity of the fluidic oscillator and issued out of two slits on the exit plane of the fluidic oscillator. The oscillation of the bifurcated plane fuel jets caused the flame behavior and combustion characteristics to change significantly compared with the corresponding behavior and characteristics of a nonoscillating plane-jet flame. The oscillation frequency, flame behavior, thermal structure, and combustion-product distributions of the fluidic-oscillator flame were experimentally examined and compared with the nonoscillating plane-jet flame. The flame behavior was studied with instantaneous and long-exposure photography. The temperature distributions were measured with a fine-wire thermocouple. The combustion-product concentrations were detected with a gas analyzer. The results showed that the length and width of the fluidic-oscillator flame were reduced by approximately 45% and enlarged by approximately 40%, respectively, compared with the length and width of the nonoscillating plane-jet flame. The transverse temperature profiles of the fluidic-oscillator flame presented a wider spread than did the plane-jet flame. The fluidic-oscillator flame’s maximum temperature was approximately 100 °C higher than that of the plane-jet flame. The fluidic-oscillator flame presented a larger CO₂ concentration and a smaller unburned C₃H₈ concentration than did the plane-jet flame. The experimental results indicated that the combustion in the fluidic-oscillator flame was more complete than that in the plane-jet flame.