Ether Fumigation, a New Alternative for the Neat Ethanol Diesel Engine

The main purpose of this study has been to investigate the possibilities off using diethylether (DEE) as ignition improver in an ethanol (EtOH) fuelled Volvo AH10A245 diesel engine, previously optimized to run on ethanol with a polyethylene-glycol ignition improver of trade mark "Beraid". Comparisons between DEE and Beraid is included in the study and it is shown that DEE can be used as excellent cetane enhancer due to the low autoignition temperature. A special fuel system based on DEE-EtOH-H2O fumigation, i.e. a small amount of DEE,EtOH and water fed directly into the inlet air duct, has been designed in order to overcome the problems associated with longer ignition delay when running the engine on DEE-EtOH mixture. The optimum enhancer content during the fumigation tests has been determined according to the engine economy and emission levels. The heat release investigation has indicated earlier combustion, and very short ignition delay. The engine runs smoothely and the peak of the heat release is lower than that obtained when the EtOH-Beraid mixture is used. Extensive increase of the negative work during compression stroke, has been avoided by the fumigation technique. Since the NOx formation rate depends strongly on combustion temperature, the DEE-EtOH mixture has been optimized in respect to low NOx level. It has been observed that HC and CO increase with the fumigation flow and engine load due to overlapping time. It is shown that a reduction of the overlapping time by optimizing the camshaft configuration improve the emissions levels and fuel consumption considerably