Experimental Investigations on the Influence of Assumptions in Soot Volume Fraction Measurement by TPD Method

This paper investigated the influence of assumptions in soot volume fraction measurement by ther- moeouple particle densitometry （TPD） method in laminar nonpremixed ethylene/air diffusion flame. TPD method is based on an extension of the theoretical treatment of Eisner and Rosner, who assumed that the par- tide deposition to a cold surface immersed in a flame is dominated by thermophoresis. They developed a formulation for the soot particle mass flux to thermocouple bead to infer soot volume fraction by inserting the thermocouple to flame rapidly. However, in their formulations, some important parameters were neglected, such as the radiation from soot to thermocouple bead. We added the parameter into the formulation and analyzed its impact. The results show that the ignored parameter had significant influence for the calculation of thermocoupie bead emissivity and thermophoresis is not the dominant mechanism during the initial stage of soot particles deposition to bead, whose real causes should be studied further.

An assessment of the concentrations of particulate polycyclic aromatic hydrocarbons (PAHs) in the aftermath of a chemical store fire incident

PM 10 airborne particles and soot deposit collected after a fire incident at a chemical store were analyzed in order to determine the concentrations of polycyclic aromatic hydrocarbons(PAHs). The samples were extracted with 1∶1 hexane-dichloromethane by ultrasonic agitation. The extracts were then subjected to gas chromatography-mass spectrometric(GC-MS) analysis. The total PAHs concentrations in airborne particles and soot deposit were found to be 3.27±1.55 ng/m 3 and 12.81±24.37 μg/g, respectively. Based on the molecular distributions of PAHs and the interpretation of their diagnostic ratios such as PHEN/(PHEN + ANTH), FLT/(FLT + PYR) and BeP/(BeP + BaP), PAHs in both airborne particles and soot deposit may be inferred to be from the same source. The difference in the value of IP/(IP + BgP) for these samples indicated that benzo[g,h,i]perylene and coronene tend to be attached to finer particles and reside in the air for longer periods. Comparison between the molecular distributions of PAHs and their diagnostic ratios observed in the current study with those reported for urban atmospheric and roadside soil particles revealed that they are of different sources.