Interpretation on fire interaction mechanisms of multiple pool fires

This work intends to interpret the fire interaction mechanisms of multiple pool fires (MPF). A series of n-heptane and ethanol MPF tests with fuel pan diameters D of 0.2 m, 0.15 m, 0.05 m and different S/D (S: fire spacing) are performed. It is revealed that the air entrainment and convection of the center fire, and the leaning of the outer fire depend on the difference of the burning rates between the center and outer fires. Besides, it is indicated that the fire merging criterion depends on fuel type. For the typical fuels used in this work, compared to ethanol MPF, n-heptane MPF has a larger critical S/D attributed to its higher burning rate and flame height. The results also indicate that for MPF with no air entrainment restriction, the mass burning flux and heat feedbacks of the center fire monotonically increase with decreasing S/D. However, if air entrainment is restricted, the heat feedback rates and fractions non-monotonically depend on S/D. Furthermore, an under-ventilated burning phenomenon of MPF is found and illustrated as a result of air entrainment restriction. It is indicated that the under-ventilated burning induces the spill of excess unconsumed fuel vapors, influences the near-field radial velocity profile of MPF, and weakens the conduction heat feedback of the center fire. Finally, for the center fire of convection-dominated MPF, a modified mass burning flux correlation is derived based on the stagnant layer theory, which is verified to reasonably agree well with the experimental data. (C) 2018 by The Combustion Institute. Published by Elsevier Inc.