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This paper presents an experimental study on the effects of Exhaust Gas Recirculation (EGR) on soot emission and diesel knock by using a direct-injection diesel engine. The effect of EGR on soot emission depends on operating conditions. Under the condition that the mass fraction burned by pre-mixed combustion of the two combustion patterns is increased, soot emission is decreased by EGR. It is also revealed that the EGR has the effects of both increasing and decreasing the diesel knock intensity. The mechanisms of these effects of EGR on soot emission and diesel knock are discussed.

The purpose of this study is to reveal the effect of use of W/O emulsified fuel without additives on DI diesel combustion. The combustion pattern, which means the ratio of fuel mass burned in the premixed (or the diffusion) combustion period to the overall supplied fuel mass, is varied by changing the injection timing and the intake manifold pressure. The exhaust emissions, such as particulates, NOx and CO, are measured. By analyzing the indicator diagrams, ignition lags are also measured. Contrary to the results of the other studies, NOx is hardly reduced by using the emulsified fuel, although it does not increase. While the particulate emission is considerably affected, remarkable changes in S.F.C. and the exhaust gas temperature are not recognized. With decreasing the fuel mass fraction burned in the prernixed combustion (spontaneous ignition) or the intake manifold pressure, the effect of the emulsification on particulate emission turns from the promotion to the suppression.