The Effect of Mixing Ratio and Fuel Purity on Smoke and Burning Characteristics of N-heptane/Toluene Test Fire

Experiments were conducted in a fire test room to investigate soot particle and burning behavior of n-heptane/toluene mixtures blended by liquids in different mixing ratio and different purity. Analytical reagent n-heptane (AR, purity ≥ 99.5 %), chemically pure n-heptane (CP, purity ≥ 97 %) and toluene (purity ≥ 99.5 %) were selected to prepare four kinds of mixtures, mixing by volume and by mass were two modes available. Extinction coefficient of smoke was obtained by extinction meter on the room ceiling. Size distribution of soot particles was measured by fast particulate spectrometer DMS500, then count median diameter (CMD) and geometric standard deviation of diameter (GSD) were calculated. Mass loss curve and temperature profile were measured by electronic balance and thermocouples, respectively. Experimental results revealed that even small difference in the incorporation of toluene, such as mixed by volume and mixed by mass, had significant influences on smoke extinction and CMD. When fuels were mixed in a same mass ratio, slight gap in purities could also affect smoke extinction. Thus fuels mixed by mass could not be employed as test fire, while CP n-heptane could be selected to prepare fuels of test fire based on our preliminary results. As for burning behavior, temperature profiles were almost identical for all mixtures, mass loss curves also had good consistencies.