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The purpose of this study is to investigate the turbulent mixing in a diesel spray by large eddy simulation (LES). As the first step for the numerical simulation of diesel spray by LES, the LES of transient circular gas jets and particle laden jets were conducted. The simulation of transient circular jets in cylindrical coordinates has numerical instability near the central axis. To reduce the instability of calculation, azimuthal velocity around the central axis is calculated by the linear interpolation and filter width around the axis is modified to the radial or axial grid scale level. A transient circular gas jet was calculated by the modified code and the computational results were compared with experimental results with a Reynolds number of about 13000. The computational results of mean velocity and turbulent intensity agreed with experimental results for z/D>10. Predicted tip penetration of the jet also agreed to experimental data.

A new technique is developed for the in-situ measurement of Sauter mean diameter of droplets in non-evaporating transient dense sprays. This method analyzes the image of a shadowpicture of a spray based on the incident light extinction principle, and allows the sizing of Sauter mean diameter of whole droplets in a transient spray with any shape. In addition, this method allows the measurement of the local droplet size in a quasi-steady region of an axisymmetric spray if the conservation equations regarding mass and momentum are included in the calculation and data analysis. A calibration was carried out using glass beads as test particles: this was proved to have an accuracy of Sauter mean diameter measurement within 10%, on average. Applications of the new technique to both diesel and gasoline (EFI) sprays have been made.

Nowadays, most manufacturers are looking for the improvement of lightweight parts and other components in the automobile field. Carbon fiber and glass fiber are the most effective materials for their requirement to reduce the weight in vehicles due to their light weight and high tensile strength. The diameter of carbon fiber is 6 μm while glass fiber diameter is 17 μm. The mechanical tensile force of carbon fiber and glass fiber are 430 N and 290 N respectively on fiber alone without matrix. Carbon fibers are gradually smaller in each filament due to tensile force. Approximately 5 mm are elongated for both carbon fiber and glass fiber in tensile test report. In current research, characteristic and tensile force of carbon fiber and glass fiber were investigated by using electron microscopy, Raman spectroscopy and XRD.