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The purpose of this study is to reveal the ignition assistance mechanism in an alcohol fueled diesel engine. A motored two stroke cycle engine with a ceramic hot plug is motored, and one shot of spray is injected into the combustion chamber. Ignition lags are measured and splitted into physical and chemical lags by means of a statistical technique presented by S. Kumagai. High speed direct photographs are also taken. From the experimental results, it has been found that there are three kinds of hot surface temperature regions. In the low temperature region the mean value of ignition lags, the physical and chemical lags decrease exponentially with increasing the hot surface temperature. These decreasing behaviours are expressed by Arrhenius type equation. The activation energies of these three kinds of lags have the same value. In the higher temperature region the ignition lags are not affected by the hot surface temperature. Between these two regions a transient region is recognized.

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.