The Mechanism Of Flame Propagation Of The Gas Fire Spreading

As a new discipline, fire science has attracted great attention in recent years. Turbulence is a difficult problem of fire science research. The turbulent flame structure and spread has been the focus of the research of scholars from various countries.In this paper, with the turbulent flame front structure analysis, we found the preheat zone and reaction zone thickness increases, and the flame spread rate increases as the diameter decreases. The optimal time step is equal to grid size divided by characteristic velocity. The flame folds strengthen and thickness of the flame front reduced with the reduction in size of the grid. The effect of reducing the time step and grid size almost the same when the numerical calculation has not reached the optimum time step.The application of adaptive grid could save computing resources. And the results of adaptive grid are much better than large-size grid. The local gas velocity increases with the reduction in the size of the grid. Thus it making the flame displacement velocity increased by flame speed. With the reduction in size of the grid, the thickness of the flame surface reduced, the temperature gradient increases. And that lead to increase of flame speed.According to the combustion experiments analysis, we found that the initial combustion eddy and the position of optimum concentration are closer to the top of box when the window opening is smaller, and the duration of combustion increase. The flame experienced six stages, ignition, flame development, intense burning, burning weakened, flame back draft and flameout. As gas leakage rate increases, the airflow disturbance and the flame intensity increases. The phenomenon of flame back draft is more obvious when the gas leak speed increase.According to the numerical calculation, we found the most appropriate time step size is lms. The window opening, combustion chamber size and leak rate have no effect on the shape of flame. The thickness of left side of the flame front is greater than the right side of the flame front. The smaller of the window opening, the greater spread of flame speed. And the flame spread faster when the fuel mixture more uniform.