The Influence of Fuel Composition and Renewable Fuel Components on the Emissions of a GDI Engine 2020-37-0025

Investigations were performed, in which the emission behavior of renewable and conventional fuels of different composition and renewable fuel components was observed. The influence of the start of injection on the emissions at WOT was investigated. This shows how much wall and valve wetting as well as the available evaporation time affects the mixture formation of the different fuels. Further, the air fuel ratio in an operating point for catalytic converter heating, with medium engine temperatures, was varied. This shows the ability of evaporation of the fuels at engine warm-up conditions and sub-stochiometric λ-values. The studied fuels were four fuel mixtures of significantly different composition of which three were compliant with the European fuel standard EN 228. A RON 98 in-field fuel, a Euro 6 reference fuel, an Anti-Spark-Fouling (ASF) fuel (designed for minimum soot production) and a potentially completely renewable, thus CO₂-neural, fuel, which is designed by Dr. Ing. h.c. F. Porsche AG, named POSYN (POrsche SYNthetic fuel) were chosen. Additionally, the fuel components Ethanol as classic biofuel, Isopropanol, Isobutanol and Methyl Tert-Butyl Ether (MTBE), which were chosen by the possibility of renewable production, were investigated. The properties of MTBE as an ether differ from those of the three alcohols, which can be observed clearly in the emissions. Due to the huge difference in the composition of the fuels (e. g. oxygen or aromatic content) significant differences could be measured in the particulate matter, hydrocarbon and carbon monoxide emissions, especially when fuel hits the wall of the combustion chamber or the piston during the injection. Nitrogen oxides can also be influenced positively by the fuel composition.