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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.

This paper presents the characteristics of diesel spray with higher and unsteady injection pressure under an elevated pressure and temperature condition. For this purpose, a pneumatically actuated rapid-compression machine was developed, which has 120 mm bore combustion chamber. A Bosch type injection system was used and can realize the maximum injection pressure about 160 MPa. By using high-speed photography, the spray-tip penetration and the spray angle were measured. Under the non-evaporating condition, the penetrations of higher and normal injection pressure are almost the same, whereas, under the evaporating condition, those penetrations are not the same. Thus, the penetration of the normal injection pressure is affected by the ambient temperature, while that of the higher injection pressure is little affected by the evaporation. The same tendency was observed in the behavior of spray angle development.