Influence of the air–fuel-ratio and fuel on the reactivity of diesel soot

This work deals with the influence of the variation of the air–fuel-ratio on the emissions as well as on the soot reactivity of a commercial vehicle diesel engine. The emissions and the associated soot reactivity are compared between conventional fossil diesel fuel and the regeneratively produced paraffinic diesel fuel HVO (hydrotreated vegetable oils). All investigations were carried out on a single-cylinder engine and the gaseous and particulate emissions were recorded. Additionally, the collected engine out soot samples were analyzed by thermogravimetric balance (thermogravimetric analysis = TGA) to determine the reactivity of the soot. Regardless of the set engine operating point, it was shown that the particulate mass is significantly reduced when operating with HVO compared to fossil diesel fuel. Other gaseous emissions are also minimally lower compared to fossil diesel. In contrast, however, the HVO fuel has an increased number of particles due to smaller particles. The variation of the engine operating parameters showed the same tendencies with regard to soot reactivity, regardless of the fuel used. However, the parameter variations were more or less pronounced depending on the respective fuel. It is particularly noticeable that the reactivity of soot, which is produced when using HVO, is reduced at every operating point despite the lower particulate mass compared to fossil diesel fuel.