Investigation on the spray development, the combustion characteristics and the emissions of Fischer-Tropsch fuel and diesel fuel from direct coal liquefaction

Diesel fuel is largely consumed by transportation services, and diesel fuel from direct coal liquefaction and Fischer-Tropsch fuel have been produced as alternatives in coal-rich areas. However, the physicochemical characteristics of the two fuels are not quite the same as those of diesel fuel derived from crude oil. Therefore, the spray development, the combustion characteristics and the emissions of diesel fuel from direct coal liquefaction, Fischer-Tropsch fuel and commercial diesel fuel were studied in this paper. The spray development was investigated by using planar laser-induced fluorescence, and the results showed that the spray characteristics of coal-liquefied fuel were similar to those of commercial diesel fuel. Diesel fuel from direct coal liquefaction has a longer ignition delay and a higher heat release rate from premixed combustion than commercial diesel fuel does because of its lower cetane number at low loads. However, the same combustion characteristics with commercial diesel fuel can be achieved by mixing diesel fuel from direct coal liquefaction and Fischer-Tropsch fuel in a ratio of 3 to 1. With increasing engine load, the in-cylinder temperature and the pressure increased which reduced the effect of the cetane number on the ignition delay and the combustion process. The regulated emissions from Fischer-Tropsch fuel were the lowest of these fuels; the unregulated emissions measured by Fourier transform infrared spectroscopy, however, were slightly higher than those of the other two fuels.