Characterization and Comparison of Flame Fluctuation Range of a Turbulent Buoyant Jet Diffusion Flame under Reduced- and Normal Pressure Atmosphere

Experiments have been conducted to investigate the magnitude of flame fluctuations of a turbulent buoyant jet diffusion flame in both reduced- (0.64 atm) and normal pressure (1 atm) atmosphere conditions. By image processing, the flame intermittency distribution contour is obtained. The magnitude of flame fluctuations is determined as the vertical flame extent from intermittency of 0.95 to that of 0.05. It is found that the fluctuation range is significantly larger in the reduced pressure than that in the normal pressure condition. The magnitude of the vertical flame fluctuations normalized by the nozzle diameter (D) and the air to fuel mass stoichiometric ratio (1+S) are correlated non-dimensionally with the flame Froude number (Frf) for both of these two pressures showing about a 2/5 power law function, although the normalized values are still a bit higher in the reduced pressure atmosphere.