Evaluation of GTL naphtha as a gasoline blend component for modern spark ignition engines

Research on the utilisation of gas-to-liquid (GTL) naphtha as a gasoline blend component is of high interest due to potential increased availability of GTL naphtha. With a high proportion of straight chain paraffins, GTL naphtha has a low octane rating, making it unsuitable to be directly blended into a conventional gasoline and be used in SI engines. One potential solution to overcome this drawback is to use ethanol as an octane booster to compensate for the reduced octane rating. The objective of this research work was to design not only an EN228 (gasoline specification in the European Union) compliant but also ‘fit-for-purpose’ gasoline fuel with GTL naphtha as a blend component. In this study, four gasoline fuels containing up to 23.5 vol.% GTL naphtha, three of which were almost EN228 compliant, were formulated and blended. Key fuel properties such as octane rating, calorific value, and distillation curve were measured and analysed. Part load emissions and fuel consumption, and full load performance were tested in an AVL state-of-art single cylinder gasoline research engine under two modern engine configurations, a boosted gasoline direct injection (GDI) and a port fuel injection (PFI). The preliminary study demonstrated that GTL naphtha can be used as a blend component, and the formulated gasoline fuels containing GTL naphtha had similar physiochemical properties to a conventional gasoline. Gasoline fuels containing GTL naphtha can be used in a SI engine without compromising the engine performance and emissions. Results also showed that, compared to the conventional compliant E228 gasoline fuel, lower particulate emissions were observed in gasoline fuels containing up to 15.4 vol.% GTL naphtha; however further studies are required to confirm this benefit.