Abstract
Temperature distribution of the methane flame was measured by using the high-speed laser speckle method. The burner used a treble circular tube. The flow rate of methane is 0.5 l/min in the first nozzle, and the flow rate of air is 5.0 l/min in the second nozzle, the flame was oscillating. There is an oscillatory phenomenon in the flame that is called a flickering. But it did not oscillating when the flow of nitrogen is 7 l/min in the 3rd nozzle. Furthermore, from Fermat's principle and Gladstone-Dale's equation, the temperature distribution of the unsteady and oscillatory diffusion flame has been predicted.
