Effect of Fuel Composition on Exhaust Gas Emissions from DI and DI Impingement Diffusion Combustion Diesel Engines

The effect of the fuel properties on diesel exhaust emissions was investigated using a commercial DI diesel and a prototype diesel engine with fuel jet impingement(OSKA--DH). The new type of diesel engine has a unique concept for the mixture formation process and is regarded as a clean diesel engine. Four types of fuels were prepared to investigated the effect of fuel properties such as cetane number, composition, oxygen content in fuel and oxygenate type on exhaust emissions for both of the engines.

The decrease in cetane number caused an increase in NO_x and a decrease in PM for the DI diesel engine because of the long ignition delay. However, in case of the OSKA-DH engine, a decrease in cetane number seldom caused an increase in PM emission. Although NO_x and PM from aromatic fuel were higher than those from paraffinic fuel, the fuel effect for the OSKA-DH engine was smaller than that for the DI diesel engine. From the evaluation of oxygenates, it became clear that the oxygen in fuel can reduce emission for both engines with and without EGR. So the combination of the new type of diesel engine, that is the engine with fuel impingement and a strong squish flow, and fuel with oxygenate is one of the possible fuels to obtain a low exhaust emission.