| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 90 === A particle image velocimeter (PIV) is employed to study the dynamic flow patterns in the cylinders of internal-combustion engines. The PIV system is developed and integrated in the laboratory. The PIV technologies are tuned in multiple phases in order to fit the applications. For instance, a test rig with very small vibration amplitudes, a seeding mechanism with large dispersion capability, a low electronic-noise image grabbling strategy, a high transparency/low light reflectivity engine cylinder, etc., are integrated in the system. The dynamic flow patterns during the intake stoke in the symmetry planes of three cylinder heads with different inlet port designs are measured. Velocity vector fields and streamline patterns related to the characteristics of the cycle variations and the influences of the engine speed are presented. The ensemble-averaged streamline patterns clearly show the dynamic behaviors of the flows under different arrangements of the inlet valves. Quantitative analysis regarding the local and global tumble ratios is conducted for the measured streamline patterns. The results show the possibility of applications of PIV on this complicated dynamic flow field. The premier factors affecting the in-cylinder tumble motions are discussed.
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