Experimental study of the thermal and burning characteristics of 15 cm pool fires fueled by heptane-toluene mixtures

Abstract

This article presents an experimental investigation of the effects of the fuel sooting propensity on the thermal and burning characteristics of 15 cm diameter pool fires burning in air. Heptane is used as reference fuel and two other heptane/toluene blends with toluene volume concentration of 5% and 10% are considered to vary the fuel sooting propensity. An exhaustive characterization of the pool fires is performed with measurements of the flame geometry, puffing frequency, mass burning rate, combustion efficiency, local temperature statistics from a dual thermocouple technique, local mean soot volume fraction from laser light extinction, radiative loss to the surroundings and total heat flux to the center of the pool surface. This comprehensive dataset can be used to develop and validate models for soot formation and radiative heat transfer. The experimental results show that the increase in fuel sooting propensity, characterized by a smoke point height decreasing from 12.5 cm to 4.9 cm, results in a significant enhancement in soot production, with the peak of mean soot volume fraction increasing from 0.62 ppm to 1.11 ppm. Radiative loss to the surroundings is also affected, as radiant fraction and total heat flux to the center of the fuel surface increase from 0.37 to 0.45 and 18.5 to 22.2 kW/m2 respectively. This is accompanied by a significant reduction in combustion efficiency from 0.95 to 0.83. In an opposite way, the impact on the temperature statistics is minor.