Flame Behavior and Thermal Structure of Combusting Nonpulsating and Pulsating Plane Jets

Abstract

The flame behavior, thermal structure, and combustion product concentrations of the flames of nonpulsating and pulsating plane jets were examined and compared. A nonpulsating plane jet was modified into a pulsating plane jet by introducing the jet fluids through a jet-impingement fluidic oscillator. The flame behavior was analyzed by photographing the flame from the lateral direction and focusing on the near burner region. The flame length was taken from long-exposure photographs. The temperature and combustion product concentrations were measured by using a fine-wire thermocouple and a gas analyzer, respectively. The results showed that the pulsating jet flame is significantly shorter and wider than the nonpulsating jet flame. A difference in the flame length larger than 30% was typical. The central region temperature distributions of the pulsating jet flame presented wide plateaus of high temperatures. The maximum temperature that the pulsating jet flame may attain was higher than that of the nonpulsating jet flame by about 250°C. The pulsating jet flame presented significantly larger concentration, smaller CO concentration, and smaller unburned than those of the nonpulsating jet flame, which implied that the combustion happening in the pulsating jet is more complete than that happening in the nonpulsating jet.