Reduction of Exhaust Pollutants from a Direct-Injection Diesel Engine Using Oxygenated Fuels : Fumigation of Oxygenates and Addition of Oxygenated Additives to Fuel

Abstract

The effects on engine emissions resulting from the intake manifold fumigation of oxygenated fuel and the addition of oxygenates to the fuel have been investigated using a direct-injection diesel engine. The results show that carefully selected oxygenated fuels effectively work to increase the ignition delay because of their low ignition quality and to decrease the combustion temperature due to the low compression gas temperature produced from their large heat of vaporization, thereby reducing levels of Bosch smoke and nitrogen oxides simultaneously. However, supplementary injection of the oxygenates into the intake air causes a drastic increase in the levels of exhaust total hydrocarbons and CO ; thus, it can be said that the addition of oxygenates to the fuel is more practical and effective than fumigation if phase separation of the blended fuel may not be occurred. In the case of addition of the oxygenates to the fuel, it is clarified that smoke is directly related to the oxygen concentration in the fuel and the level of nitrogen oxides is decreased with an increase in the heat of vaporization of the additive.