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標題: 單缸機車引擎進氣道與排氣系統瞬時流場數值模擬與量測
The Measurement and Analysis of the Instant Air Flow in the Exhaust Pipe and Intake Port for Single Cylinder engine
作者: 陳佳良
關鍵字: exhaust pipe;排氣管;intake port;phoenics;進氣道
出版社: 機械工程學系
而進氣道的計算則是將實際引擎的CAD檔案輸入PHOENICS作計算區域與網格劃分並且執行流場計算,實驗則是在Flow Bench上作測試,在進氣道出入口壓力差相同的情況下,量測不同閥升程的空氣流量,實驗中同時利用熱線測速儀量測入口速度。計算結果發現雖然選用不同的設定,但算結果差異性不大。而改變兩種不同的邊界壓力設定方式,其結果有明顯差異。

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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