Comparison of the combustion and exhaust emissions of a compression ignition engine fuelled with diesel from direct coal liquefaction and diesel blends

The purpose of this study is to compare the combustion and exhaust emissions of a four-stroke diesel engine with supercharging and a high-pressure common-rail injection system fuelled with diesel from direct coal liquefaction, with diesel and with their blends. The operating conditions are set at an engine speed of 1450 r/min, an engine torque of 112 N m (low load; a brake mean effective pressure of 0.2964 MPa) and an engine torque of 224 N m (medium load; a brake mean effective pressure of 0.5928 MPa). The injection pressure is set at 1000 bar, and the injection timing is set at 2.5° crank angle after top dead centre and 3.5° crank angle after top dead centre for the low load and the medium load respectively. The experimental results show that, for the two loads, the phases of the peak pressure and the maximum heat release rate are retarded on increasing the proportion of diesel from direct coal liquefaction; meanwhile, the ignition delay increases significantly, and the combustion duration decreases obviously. The nitrogen oxide and soot emissions decrease simultaneously and the carbon monoxide and hydrocarbon emissions increase significantly on increasing amount of diesel from direct coal liquefaction. The trade-off relationship between nitrogen oxide emissions and soot emissions can be improved when the diesel engine is fuelled with diesel from direct coal liquefaction instead of with diesel. An artificial neural network is used to predict accurately the exhaust emissions (nitrogen oxide, soot, carbon monoxide and hydrocarbon) and the fuel consumption of the blend containing 50% diesel and 50% diesel from direct coal liquefaction over the European Stationary Cycle.