get a moderate atomization.In this study,it aims to improve an atomization of ship fuel by blending liquefied dimethyl ether(DME).A rapid evaporation of DME inside the blend fuel,so called a flashing phenomenon,is expected to enhance the atomization process.In-cylinder pressure is usually very high,so a rapid DME evaporation by pressure droppings could not be expected in real engines.However,in-cylinder temperature is also very high,especially for CI engine case,so the rapid evaporation by temperature risings could be realized.In present experiment,marine diesel oil(JIS A heavy oil)was used as a base fuel,and liquefied DME was blended inside a pressurized fuel tank.Kinematic viscosity measurement system was established to apply for the blend fuels.A transparent cylinder made of polycarbonate and two set of stainless steel flat plates were used to construct a pressure resistant cell where a capillary viscometer was inserted.The viscosity of blend fuel was measured under a pressurized ambient inside the cell while keeping DME at the liquid state.A fuel injection system which can realize a single fuel injection through a single hole nozzle(φ0.26mm,L/D=3)was made with combination of a fuel pump driven by a motor and a solenoid valve.The injected fuel sprays were observed and their characteristics,such as the Sauter's mean diameter,spray angle,spray penetration,and spray volume,were measured at an atmospheric ambient condition.The droplet size was measured by an immersion liquid method.And spray was observed by a high-speed digital camera(10000 frames/sec.)with a direct photography.From experiments,it is obtained that the droplets of the DME blend fuels become smaller compared to the base fuel,and the spray angle of the DME blend fuels become larger while the penetration become shorter.And the spray volume of the DME blend fuels become larger during the fuel injection period.It is concluded that the blending of liquefied DME enhances the atomization of ship fuel.