Experimental study on the performance and the exhaust emissions of a diesel engine fuelled with diesel from direct coal liquefaction and diesel blends under low-temperature combustion

In this study, the experiment is conducted on a four-cylinder direct-injection diesel engine equipped with a turbocharger and a high-pressure common rail injection system. The test fuels include diesel from direct coal liquefaction, diesel and their blends. The effects of exhaust gas recirculation and retarded injection on the combustion, the nitrogen oxide emissions and the soot emissions under low-temperature combustion are explored. The results indicate that exhaust gas recirculation and retarded injection can effectively lengthen the ignition delay of test fuels especially for diesel from direct coal liquefaction. The ignition delays of all the fuels become shorter with increasing engine load, but the variation rates for diesel from direct coal liquefaction and diesel are not the same. Retarded injection can lead to a soot hump for the four fuels, but it reflects this soot change for diesel from direct coal liquefaction more sensitively than for diesel. Diesel from direct coal liquefaction produces lower nitrogen oxide emissions and lower soot emissions than diesel does under low-temperature combustion. A control strategy that achieves reduction in both the nitrogen oxide emissions and the soot emissions will cause the fuel consumption to deteriorate.