Development of a Spark-Ignited Direct Injection Flexible Fuel Engine for Gasoline and Alcohol Fuels

By optimizing the main parameters of an engine with a new type of spark-ignited direct injection circularly stratified-charge (DICSC) combustion system when it operates on methanol, ethanol or gasoline, the optimum parameters of the combustion system for the three fuels are obtained respectively. Then, by compromising the different system parameters for the three fuels in terms of their effect on engine performances, the combustion system parameters of the flexible fuel engine (FFE) are obtained. It can be realized for the FFE to operate on methanol, ethanol or gasoline without changing the engine. Performances of the FFE are studied. The results show that the FFE has the advantages of high thermal efficiency equivalent to that of direct injection diesel engine due to adopting the mixture stratification. NO_X emissions for alcohol and gasoline operations are only 10%～40% and 21%～78% of those of diesel engine respectively at load characteristics. In the FFE, CO emission is lower than 1%, and HC emission is slightly higher than that of diesel engine. Smokeless combustion can be realized for alcohol operation at any operating conditions, and there exists little smoke emission for gasoline operation only at high load.