Ignition delay and heat release analysis of an ethanol fumigated turbocharged diesel engine

A turbocharged, open chamber diesel engine was fumigated with prevaporized ethanol and run over its speed and load range. The mass percentage of ethanol was varied from zero to 80% at light load and zero to 50% at full load. Digitized cylinder pressure data were cycle averaged and used to examine ignition delay and to calculate heat release patterns and NO production. It is shown that the ignition delay is increased by the thermodynamic effects of fumigation, but it can be decreased by chemical effects of alcohol reactions if the cylinder gas temperature is above approximately 900 K (1600/sup 0/R). The heat release model uses three zones; a diesel fuel-ethanol zone, an air-ethanol zone and a products zone. The mode predicts that fumigation causes a large increase in the initial burning spike even when the fumigation decreases the ignition delay. Fumigation decreases combustion duration slightly at heavy load but greatly increases the duration at light loads. Values of NO concentration computed from the product zone properties and Zeldovich kinetics predict the observed exhaust NO trends, but are about twice too high in value.