Mass burning rate and merging behaviour of double liquid pool fires under cross winds

Abstract

This paper experimentally investigates the effects of cross wind on flame interaction and burning characteristics of double liquid pool fires. Two burners were used including a square burner and a line burner. The separation distance between the double fires and the speed of cross wind were varied, providing a total of 66 test conditions. The experimental results showed that the mass burning rate increases initially with increasing separation distance until a critical value, after which the mass burning rate decreases with a further increase of the separation distance. This non-monotonic behaviour was attributed to the competition between an increase of air entrainment and a decrease of the flame heat feedback from the adjacent fire, as the separation distance increases. A correlation was developed for the mass burning rate based on the stagnant layer solution of liquid fuel evaporation and combustion, incorporating the separation distance between two fires and cross wind, and is found to predict well the experimental data for all experiments. Image analysis indicated that, with increasing separation distance, the flame merging of double pool fires can be divided into three regimes: the continuous merging regime, the intermittent merging regime, and the non-merging regime. A physical model was proposed for the flame interaction and merging behaviour of the double pool fires, based on which a piecewise function is developed for predicting the flame merging probability and the criteria for the merging/non-merging flames are also determined. The proposed formulations were found to correlate well with the current measurements of liquid pool fires and published literature data of single pool fires.