Experimental Study of Coal Liquefaction Diesel Combustion and Emissions

Abstract

An experimental study was conducted on the combustion processes and emissions of direct coal liquefaction (DDCL) and Fischer-Tropsch (FT) fuels in a single-cylinder research diesel engine. Under low load conditions (5 bar IMEP), the results show that the ignition delay is shorter for the FT fuel compared with the reference fuel (Euro IV diesel), while it is longer for the DDCL fuel compared with the reference fuel. However, under high load conditions (10-15 bar IMEP), the Cetane number (CN) shows insignificant effects on the combustion process. The premixed heat release peaks of the fuels are correlated with the ignition delays, i.e. shorter ignition delay led to lower premixed heat release peak. For the emissions, both the FT fuel and the DDCL fuel show similar NOx level to the reference fuel under the conditions tested. The two liquefaction fuels show significantly lower soot emissions than the reference fuel, specifically for the higher load conditions (>=10bar IMEP), and the FT fuel produced the lowest level of soot emissions among the three fuels. For the FT and DDCL fuels, the HC emissions are generally lower than those of the reference fuel, except for the lowest load condition, which DDCL produces slightly higher HC emission. However, the CO emission of FT is lower than the reference fuel while the CO emission of DDCL is higher. In terms of unregulated emissions, the two liquefaction fuels show insignificant difference compared with the reference fuel at very low levels.