Size distribution and spectral response of diesel soot measured by SMPS and multi-wavelength photoacoustic spectrometer

We demonstrate the real-time characterization of size distribution and spectral responses of the diesel soot emission using commercially available diesel fuel (B7) including 7% biofuel content (FAME) and pure petroleum-based fuel (B0) using an instrument combination of multi-wavelength photoacoustic spectrometer (4λ-PAS) and a scanning mobility particle sizer (SMPS). Based on the measurement results, the soot emission using commercially available diesel fuel was characterized, and its physiochemical properties were compared with those generated from bio-free fuel. The thermal evolution of the soot from exhaust emissions was also examined through post-treatment temperature analysis. We experimentally demonstrated that commercially available B7 fuel exhaust is lower in total number concentration than bio-free fuel at every defined temperature at the engine's idle speed. The spectral response of soot, quantified by the Aerosol Ängström Exponent (AAE), was used for qualitative analysis of diesel exhaust carbonaceous particulate matter (CPM) at different temperatures. This analysis revealed decreased AAE values at higher temperatures, with a more pronounced decrease observed in commercially available biodiesel blended fuel than in pure petroleum-based fuel. The proposed measurement setup enables real-time, precise, and accurate measurement of light absorption of soot from exhaust emission, paving the way for novel investigations into the volatility and thermal evolution of soot emissions under different fuel compositions.