Effect of exhaust gas recirculation on physiochemical characteristics of diesel soot

Abstract

The physiochemical characteristics of soot particles such as oxidative reactivity and volatile organic fraction (VOF) are of importance with regard to performance of diesel after-treatment systems and the health hazards. Such characteristics depend on the engine operating conditions, as mixture formation and temperature-pressure history of the soot vary under different operating conditions. In this research, a single cylinder heavy duty diesel engine is used to investigate the effects of various multiple injection strategies and EGR application on diesel soot under conventional diesel regime. Characterization methods such as X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Thermo-gravimetric analysis (TGA) are applied to study the soot characteristics and establish their correlation with engine operating conditions. It is shown that when no EGR is applied, the amount of VOF in the soot strongly depends on injection strategy. Higher amount of pilot injection and longer dwell time results in higher level of VOF. However, once the EGR is applied such dependence between VOF level and injection strategy is no longer present. The EGR is found to reduce both the VOF level and reactivity of diesel soot.