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The Measurement and Analysis of the Instant Air Flow in the Exhaust Pipe and Intake Port for Single Cylinder engine
|關鍵字:||exhaust pipe;排氣管;intake port;phoenics;進氣道||出版社:||機械工程學系||摘要:||
The computational fluid dynamics (CFD) was used in this study to investigate the flow characteristics in the engine inlet and exhaust system. The inlet flow was a steady flow simulating the flow bench test measuring the flow coefficient of inlet valve. The exhaust flow was a pulsating flow simulating engine running at constant speeds. A commercial software package PHOENICS was used in this study.
In the inlet flow study, the CAD file of the engine was input to PHOENICS to generate the necessary geometric configuration of the intake system. It was found that grid size and the boundary condition at the inlet were the primary factors to affect the results of calculation. The flow rates at high valve lift were 5% lower than the measured data. However, at low vale lift, the deviations were as high as 25%. The discrepancy can be attributed to that the structured type grid system did not quite fit to the complex geometry of inlet system.
A simplified exhaust pipe with two expansion chambers was used in the exhaust flow study. The velocity distributions obtained from numerical calculation were close to measured data, which were obtained with a hot wire anemometer. It was found that circulating zones emerged at the corner of the first expansion chamber, and transported down streams, and then decayed. The computing result also showed that the distribution of pressure in the exhaustion tube was one-dimensional.
The turbulence intensities as well as the cyclic variations of the flow in the expansion chamber were also measured with hot wire anemometer. It was found that high turbulence flow concentrated in the second expand chamber.
|Appears in Collections:||機械工程學系所|
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