Flame geometrical characteristics of downward sloping buoyant turbulent jet fires

The downward sloping buoyant turbulent jet fires occur occasionally and practically as the gaseous fuel leaks, while their morphologic characteristic parameters have not been quantified yet. In this work, a sequence of experiments with three nozzle diameters are performed at five downward sloping angles, 0 degrees, 15 degrees 30 degrees, 45 degrees, 60 degrees relative to the horizontal, aiming to examine the flame geometrical characteristics of downward sloping buoyant turbulent jet fires. It is found that the flame dimension, termed as flame horizontal projection and flame downward distance, increases with the increasing heat release rate, and the increasing downward sloping angle diminishes the flame horizontal projection, but enlarges the flame downward distance. Both the flame horizontal projection and flame downward distance normalized by nozzle diameter can be correlated with dimensionless heat release rate Q* by 1/2 and 3/5 power, respectively, and the correlated coefficients exhibit a linear relationship with cos theta and sin theta for cases at different downward sloping angles. Additionally, two remodified flame Froude numbers concerning the horizontal and vertical components of initial momentum, i.e. Fr*(f,h) and Fr*(f,d), are proposed to correlate the non-dimensionally flame horizontal projection L-p*(,h) and flame downward distance L-d*, respectively, and the correlated results can well unify the current experimental results. A better understanding of jet flame geometry will increase accuracy in the prediction of fire hazards of such fires.