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In direct-injection (DI) gasoline engines, spray characteristics greatly affect engine combustion. For the rapid development of new gasoline direct-injectors, it is necessary to predict the spray characteristics accurately by numerical analysis based on the injector nozzle geometry. In this study, two-phase flow inside slit nozzle injectors is calculated using the volume of fluid method in a three-dimensional CFD. The calculation results are directly applied to the boundary conditions of spray calculations, of which the submodels are recently developed to predict spray formation process in direct injection gasoline engines. The calculation results are compared with the experiments. Good agreements are obtained for typical spray characteristics such as spray shape, penetration and Sauter mean diameter at both low and high ambient pressures. Two slit nozzle injectors of which the slit thickness is different are compared.

To achieve a clean atmospheric environment and a stable fuel supply, considerations are being given to the use of methanol fuel as one of the fuel used by alternative fuel vehicles. This report describes the development and studies of a brushless motor-driven fuel pump to be employed for a methanol electronic fuel injection system. Several problems remained to be solved for the fuel pumps used with methanol fuel, and hence considerations were given to the following items: (1) A control unit was developed that can be used in high-pressure fuel. This unit has been downsized substantially due to the adoption of a system in which it is subjected to forced cooling with the fuel.

The relation between the dynamic control range and the valve behavior has been studied. The results show that reduction of valve bounce and short valve closing time are important to the expansion of the dynamic control range. Non-linearity of fuel flow at short pulse widths is caused by the valve bounce and inertia force. Therefore, lessening valve weight is very effective to obtain good linearity. Our valve is composed of a steel ball, a pipe and an armature welded together by laser, and the weight is reduced to half of a conventional pintle needle. The valve is closed only by spring force. While satisfying minimum operating voltage; 6 V, dimensional factors were optimized to obtain higher spring preset load. This made it possible to reduce the valve closing time. Consequently this injector exhibits a greater dynamic control range.