Experimental Analysis of the Morphology and Nanostructure of Soot Particles for Butanol/Diesel Blends at Different Engine Operating Modes

Abstract

In order to comply with strict emission standards, a reduction in diesel particle matter emissions can be addressed by minimizing particle formation and by optimizing particle oxidation in the combustion chamber and in the exhaust and diesel particulate filter systems. The characterization of soot morphology and nanostructure is necessary to understand the soot formation and oxidation processes. Furthermore, understanding these characteristics is important because they affect the aerodynamic behavior of diesel particulate matter in the exhaust system, diesel particulate filter systems, and the environment. This study aims to investigate the influence of fuel oxygen content and engine operating modes on the morphology and nanostructure of soot particles. The oxygen content in the fuel was varied from 0% to 4.32% and 6.48% by using diesel and 20 and 30% butanol blends (by volume) with diesel. As the oxygen content increased, corresponding nanostructure characteristics fringe length and separation distance increased and fringe tortuosity decreased. Changes to the nanostructure properties will have an influence on the operation of diesel particle filters, particularly during the regeneration processes. However, other characteristics such as the influence of these fuels on particle mass and number emissions, performance parameters, and gaseous emissions will also have a significant influence on implementing these fuels in modern diesel vehicles.

Impact of n-Hexanol Blending on Morphology, Nanostructure, Graphitization, and Oxidation Characteristics of Diesel Particles

“…n-Hexanol addition decreased the aromatic component, while it increased the oxygen content in the blends, which could inhibit particle surface growth but enhances soot oxidation, leading to small primary particles in size. Similar results have been reported in previous studies. ,, Li et al investigated the soot morphology in a laminar diffusion flame fueled with n -heptane, n-butanol, and H50B50 (50% n -heptane and 50% n-butanol, v/v), respectively. Their results showed that as the n-butanol content in blended fuels increased, smaller aggregates and primary particles were produced.…”

“…Similar results have been reported in previous studies. 29,30,71 Li et al 71 investigated the soot morphology in a laminar diffusion flame fueled with n-heptane, n-butanol, and H50B50 (50% n-heptane and 50% n-butanol, v/v), respectively. Their results showed that as the n-butanol content in blended fuels increased, smaller aggregates and primary particles were produced.…”

“…In a further study, results showed that methanol/diesel soot samples had higher oxidation reactivity than diesel soot, which was linked to their smaller primary particle diameter, lower degree of graphitization (smaller fringe length and larger separation distance), and more active aliphatic C–H groups. Conversely, Verma et al reported that as the butanol content increased, the fractal dimension of exhaust particles increased, while the fringe separation distance decreased. Lapuerta et al observed by transmission electron microcopy (TEM) that as the proportion of butanol increased from 0 to 20%, the mean primary particle diameter and interplanar distance decreased, while the fringe length and tortuosity increased.…”

“…Hence, a comprehensive analysis for understanding physicochemical characteristics of exhaust particulates is of great implication. Many publications reported that diesel fuel blending with alcohols also affects the soot oxidation reactivity. − Recently, Wei et al claimed that methanol/diesel blends had smaller primary particle size and lower fractal dimension. In a further study, results showed that methanol/diesel soot samples had higher oxidation reactivity than diesel soot, which was linked to their smaller primary particle diameter, lower degree of graphitization (smaller fringe length and larger separation distance), and more active aliphatic C–H groups.…”

Nanostructural Disorder and Reactivity Comparison of Flame Soot and Engine Soot Using Diesel and Jatropha Biodiesel/Diesel Blend as Fuels

“…23 High-resolution transmission electron microscopy (HRTEM) analysis has been crucial in providing evidence of soot nanostructural disorder. For instance, Verma et al 24 found that, by increasing the oxygen content in the butanol− diesel blends, soot fringe length and fringe separation increased, while the tortuosity decreased. On the contrary, in the study on waste cooking oil methyl ester−diesel blends by Man et al, 25 it was observed that the reduction in soot emission in a DI engine is a result of greater oxidative reactivity due to shorter fringe length and greater tortuosity of diesel engine soot.…”