Experimental study on mass burning rate and heat feedback mechanism of pair of unequal circular pool fires of heptane

Author: Wan, H. X., Yu, L. X., Ji, J.

Journal: Proceedings of the Combustion Institute

DOI: 10.1016/j.proci.2020.07.079

Keywords: Multiple pool fires, Flame merging, Mass burning rate, Heat feedback, Air entrainment, Thermodynamics, Energy & Fuels, Engineering

Abstract: 

This paper aims to study the burning behaviors and heat feedback mechanisms of pair of unequal circular pool fires. A series of experiments on heptane pool fires with four diameters of 10, 15, 20 and 30 cm comprising 6 groups of unequal two pans was carried out. The pan edge spacing (S) was varied as a multiple of half of the diameter of the small pan in fire group and increased from 0 to the case of no flames merging. The fuel mass, flame shape and heat feedback components were measured. The results showed that the mass burning rate per unit area ((over dot (m))'') of the small pan (D-s) in fire group increases monotonously with reducing S. While (over dot (m))'' of the large pan (D-l) in fire group increases first and then decreases with reducing S, and the peak (over dot (m))'' presents at S/D-l = 0.167-0.75. It is also found that for a given fire group, (over dot (m))'' from D-s and D-l are very close. From the determined heat feedback components and their fractions, it is indicated that for a given target pan, the three types of heat feedback fractions including conduction, convection and radiation are weakly affected by the adjacent pan scale. For the target pan D-t = 10 cm, the radiative heat feedback fraction (chi(rad)) nearly maintains constant for the present limited S, the conductive heat feedback fraction (chi(cond)) is comparable to chi(rad) with small S and then it begins to decay as S increases. For D-t = 15-30 cm, the burning rate of each pan in fire group is radiation dominated. Based on the imposed heat feedback mechanism of MPF, a useful correlation is developed to estimate the mass burning rate of radiation-dominated MPF. (C) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.