Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/2269
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
C.L.Chen
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: 
自從計算機發展以來,由於計算速度不斷增快,計算成本不斷降低,利用計算流體力學CFD軟體幫助引擎設計的例子越來越多,尤其在現代,產品週期縮短,如何應用CFD軟體來減少引擎開發的時間及實驗的花費成為各車輛製造業的重要課題。
本文利用商業計算體力學CFD軟體PHOENICS計算單缸機車引擎的排氣管及進氣道流場,為了與計算結果作驗證,本文同時利用熱線測速儀進行進氣道入口流速及排氣管膨脹室內流場的量測。為了方便排氣管膨脹室內的流場量測,本文利用壓克力仿造一軸對稱雙膨脹室排氣管,並量測及計算兩種不同轉速的流場。量測結果發現引擎排氣出口速度分佈是軸對稱,膨脹室內的流場在1750rpm轉速下量測結果對稱性較佳,3500rpm的對稱性則比較不好。計算與量測結果都顯示排氣管出口有逆流產生。
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.
URI: http://hdl.handle.net/11455/2269
Appears in Collections:機械工程學系所

Show full item record
 

Google ScholarTM

Check


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.