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Amidst the growing concerns for the global environment and the escalating demands for low exhaust emissions and high fuel economy small motorcycles, the electronically controlled fuel injection system (hereafter referred to as FI system) is making its appearance as an effective device to reduce emissions while improving fuel economy by precisely controlling the air-to-fuel ratio. Fuel injectors and fuel pumps currently used in small motorcycle FI systems were originally derived from multi-cylinder engine automobile and large motorcycle FI system components, and therefore have not been necessarily suitable for small motorcycle application.

The atomization of molten aluminum when injected during high-pressure die casting is analyzed to determine its effect in enhancing the strength of the product being cast. In the previously reported first step of this study, molten aluminum was injected into open space and its atomization was observed photographically. Now in the second step of the study, a simulation is conducted to determine how the molten aluminum becomes atomized at the injection nozzle (gate) and how this atomized material flows and fills the cavity. A new simulation method is developed based on large-eddy simulation coupled with the volume-of-fluid method. The simulation system is verified by comparing its output with photographs taken in the first step of the study. Simulations are then conducted using an approximation of a real cavity to visualize how it is filled by the atomized molten aluminum.

In recent years, studies have been conducted on the relationship between the J factor, which indicates flow of molten aluminum at the time of injection, and the quality of HPDC products. The flow of molten metal at a high J factor is referred to as “Atomized Flow.” The authors and others conducted studies on the relationship between the J factor and the strength of HPDC products. An area exceeding 300MPa was found in the product produced at a high J factor corresponding to the “Atomized Flow.” The defect was less in the above-mentioned position because the gas porosity was finely dispersed. Considering that the fine dispersion of gas porosity is related to the “Atomized Flow”, pictures were taken to analyze “Atomized Flow.” The molten aluminum was ejected into an open space at a high speed and the splashed conditions were photographed. From the images taken by the pulse laser permeation, the conditions of microscopic atomized flow were observed precisely.

With the increasing requirements of environmental conservation in recent years, reduced exhaust emissions and increased fuel-efficiency are in high demand for smaller size motorcycles popular in the Asian region. In order to meet such demand, the optimum design of the fuel supply system is the most effective method. In the carburetor, the core component of the fuel supply system used on a majority of current models, a 25% improvement in the accuracy of air-fuel ratio fluctuation, as well as a 15% reduction in size, have been achieved in comparison with past models. On the other hand, in fuel injection systems, the use of which is gradually expanding, it is essential that the components be highly functional with high performance, while at the same time being of a compact size. In regards to the injector, optimum spray form and a 30% reduction in size have been realized by utilizing injection simulation techniques.