Fischer- Tropsch-Synthesis Fuels as Diesel Engine Fuel-Fuel of the Future

Rapport, 2000

The Fischer-Tropsch (F-T) catalytic conversion process can be used to synthesize diesel fuels from a variety of feed-stocks, including coal, natural gas and biomass. Synthetic diesel fuels can have very low sulfur and aromatic content, and excellent autoignition characteristics. Moreover, Fischer-Tropsch diesel fuels may also be economically competitive with regular diesel fuel if produced in large volumes. The aim of this investigation is to reveal and analyze the effects of F- T fuels on a research diesel engine performance. Previous engine laboratory tests indicate that F-T fuels are promising alternative fuels because they can be used in unmodified diesel engines, and substantial quantitative exhaust emission reductions can be reached. Also substantial qualitative reductions, e.g. reduction of the number of hazardous chemicals and reduction of the concentration of hazardous chemicals in the exhausts may be realized. Since the engine performance is close1y related to in-cylinder processes, a detailed thermodynamic analysis has been performed revealing the real thermo-chemistry history. The experimental results have shown that F-T fuels have a beneficial effect not only on the emissions levels, but also on other energetic parameters of the engine. Heat release analysis has shown that ignition delay, cylinder peak pressure, heat release gradient and indicated efficiency are affected as well. Two different mixtures of FT-fuels with variation in carbon chain branching and, to a certain extent variation in chain 1ength were tested and their results were compared with those obtained from conventional fuel (MK 1). The selected optimized F-T fuels mixture were further tested according to the 13 mode ECE R49 test cycle and were found as good competitive alternative diesel fuels.