Particle characterization of soot aggregates emitted by gasohol fueled direct injection engine

In this study, two gasohols, namely, E15 [15% v/v ethanol blended with 85% v/v gasoline] and M15 [15% v/v methanol blended with 85% v/v gasoline] with respect to baseline gasoline were investigated for the characteristics of their soot particles. An in-depth comparative analysis for morphological characteristics of particulate matter emitted by a GDI engine using a high-resolution transmission electron microscope (HRTEM) was performed. Soot particles were collected using a partial flow dilution tunnel, and the effect of engine load and fuel oxygenated content on soot morphology was investigated. For soot samples from different test fuels, primary particle diameter (D _p ), length, and width of the soot agglomerate and high angle annular dark field were investigated. At the macroscale (ratio of length to width of agglomerate L/W), the HRTEM images of gasoline soot agglomerates were observed to be remarkably similar to the agglomerates from gasohols; however, a detailed analysis of these images on the microscale (ratio of skeleton length to width of agglomerate L _sk /W _sk ) showed them to be significantly different from each other. The mean primary particle (D _p ) was found to be in the range of 20−32 nm for both loads and test fuels.