Uncertainties in the measurement of simulated carbonaceous aerosols: (I) Characterization of emissions from a portable diesel generator and development of the extended idealized aggregate theory and (II) the effect of metal additives on the evolved gas analysis of carbon.

摘要

Several studies have characterized emissions from on-road diesel engines; however, non-road diesel engines, have received less attention. Although non-road diesel engines contribute a small fraction of the total number of diesel engines in operation, because they have minimal emissions control, they account for a disproportionate fraction of the PM emissions - in the US their contribution is estimated at 44% of the total diesel PM emissions. Emissions from a small 4.8 kW diesel generator running on ultra-low sulfur diesel and biodiesel fuels are characterized. Aerosol characteristics such as particle size distribution, carbon content, and morphology were similar to that published for larger on-road diesel sources. The use of biofuel (B 100) is important due to its increasing role as an alternative energy source. Results showed that the biodiesel particles were compact, irregular, and lack the clearly defined primary particles of diesel aggregates. At high loads they had similar elemental (EC) and organic (OC) ratios as diesel particles; however at lower loads this ratio was much smaller.;Mass measurements of aerosols are often conducted using gravimetric methods which offer poor time resolution. The idealized aggregate (IA) theory developed by Lall and Friedlander, 2006 was extended to the transition regime for diesel aggregates to determine aerosol mass from real-time measurements. Results showed that the calculated mass concentrations from the extended IA theory were in good agreement with the mass concentrations from gravimetric and total carbon measurements.;There has been limited amount of work understanding the effect of metals on the thermal stability of carbon during its measurement in evolved gas analysis (EGA) thus biasing the measurement of the EC/OC ratio. Metal chlorides and sulfates were externally mixed with a variety of primary and secondary carbonaceous aerosols. Measurements showed that metals in the presence of a carbonaceous aerosol decreased its oxidation temperature and enhanced OC charring. Not only do different metals have different effects on the thermal stability of carbon, but different types of carbonaceous aerosols reacted differently with the same metal during EGA. An attempt was made to correlate these findings to changes to the EC/OC ratio measurement and a discussion on recommendations is given.