| Summary: | 碩士 === 中原大學 === 機械工程研究所 === 90 === Internal combustion engines are the primary power source for cars and motorcycles. It is the production of mechanical power from the chemical energy contained in the fuel. Because the importance of the phenomena of the flow field in internal combustion engines, this study uses the KIVA-3V code to analyze the flow field. The KIVA-3V code, which was developed at the US Los Alamos National Laboratory, is a powerful tool to analyze the transient, two- and three-dimensional, chemically reactive fluid flows with sprays and turbulence.
In general, the study of the flow field in internal combustion engines uses two methods: the experimental technique and the numerical simulation. Because the experimental technique cannot measure the overall flow field in the cylinder, this study uses the KIVA-3V code to simulate it. Besides, due to the tremendous computing capability available, people usually use numerical simulation for the study. The KIVA-3V code is a computational fluid dynamic program that uses the finite volume method with Arbitrary Lagrangian-Eulerian (ALE) algorithm. The Monte Carlo-based discrete-particle technique used in the fuel sprays model was implemented to describe the behavior of the droplets. The KIVA-3V code is capable of calculating the effects of droplet oscillation, distortion, breakup, collision and coalescence.
The study uses the RNG (Renormalization Group) turbulence model to study the phenomena of the flow field in an internal combustion engine. The engine performance parameters investigated are tumble ratio, swirl ratio, turbulence intensity, and turbulence kinetic energy. In addition, volumetric efficiency and the in-cylinder pressure behavior during the intake and compression stroke were obtained and compared with the experimental data. Their differences are within 5%, using the experimental values as the reference. Furthermore, the volumetric efficiencies for the three sets of intake valve lifts under study appear to be reasonable.
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