Effects of groove width, spacing distance and ullage height on combustion and flame merging characteristics of two-line n-heptane pool fires

Abstract

This paper studied the combustion and flame merging characteristics of two n-heptane line pool fires. The effects of groove width (0.5, 1 and 1.5 cm), spacing (0, 5, 10, 15, 17.5, 20, 22.5, 25 and 30 cm) and ullage height (the dimensionless liquid fuel height H*=1/4,1/2,3/4 and 1) were revealed. It was found that, at the same spacing, the flame merging increases with the increase of dimensionless liquid fuel height H*.With the increase of groove width, the probability of flame merging also increases, and the values of S/hf,S=0 for the critical merging position will decrease, which is larger than that of gas fuel flame merging. With the spacing increase, the flame height will decrease and then increase, making the flame inclination angle increase and decrease. It is interestingly found that, at the intermittent merging and non-merging stages, ṁ″ is almost smaller than single case ṁs″. And the smallest of ṁ″ appears at the position of the largest inclination angle. Moreover, under the same spacing and H*, the smaller of the groove width is, the greater the mass loss rate per unit area ṁ″ is, which demonstrates that the smaller width of groove will promote the flame merging and burning. In addition, a heat transfer model is built, which can well address the burning behaviors with different W.