ABSTRACT
From the microscopic view the microstructure of flame in methane/air explosion was studied by using high speed schlieren photographs. The experiment shows that inner flow field of flame has distinct fractal characteristics. Under different propagation conditions the fractal dimensions are different. The fractal dimensions of flame inner flow field are normal distribution. The more the fractal dimension number is, the faster the flame propagates, and the stronger the explosion is. Inside the flame, where the number of fractal dimension is the biggest is the main reaction area. And in this area there are dense gradient lines and strong bright contrast. 9.5% methane/air flame has the biggest number of fractal dimension and its velocity is also the fastest. The biggest number of fractal dimension is 1.5437, the fractal dimension number of flame inner flow field of rich fuel and lean fuel is 1.4812 and 1.3678, respectively. The fractal dimension number in closed tube is bigger than the number near the vent of the tube. The trend of flame velocities is the same as the trend of fractal dimensions.
