Visible length of vertical free turbulent diffusion flames

An experimental study has been made, which together with literature results covers the practically accessible range of operation from forced convection to natural convection. General correlations are given for predicting flame length over this range. The lower Reynolds ratio limit of the correlations has been determined. Under natural convection conditions flames of large base diameter are found to be rather short, and in these an effect of length to diameter ratio is apparent. Explanations have thus been found for the behavior of the pan fires of Blinov and Khudiakov. It has also been shown that flames in the forced convection limit are around 50% longer than was previously suspected.