運用CFD數值方法於引擎進氣渦流設計

Engine Intake Port Design for Swirling Flow by Using CFD Numerical Method

廖俊性(Jun-Xing Liao)

指導教授 ： 吳浴沂

國立臺北科技大學/機電學院/車輛工程系所/碩士(2008年)

https://doi.org/10.6841/NTUT.2008.00372

摘要

本研究在於藉由引擎進氣道幾何的設計，以產生強烈的進氣渦流。運用計算流體力學之商用軟體－FLUENT，採用 紊流模型計算穩態單缸四汽門機車引擎進氣道流場，模擬引擎在流量測試平台的真實情況，研究方法是直接使用引擎設計時的3D CAD檔案進行分析，最後並將計算出的流量係數(Flow coefficient, )及渦旋比(Swirl ratio, )與實驗值作一比較；結果發現原廠氣道雙閥開啟案例中，在進氣閥開度小的時候預測相當準確，誤差百分比為1.14%；而原廠氣道單閥開啟案例是由關閉右側進氣門的方式，使氣流導引至汽缸的切線方向產生渦流以計算渦旋比，其結果顯示在氣門開度大時運用高階離散法可獲得良好之準確度，其整體平均渦旋比為2.041，相對誤差百分比僅為0.443%；然後利用氣道形狀的幾何修改，設計一弧線角度改變氣流的運動方向，使以達到引擎進氣渦流設計的目的，其結果顯示相較於原廠氣道單閥開啟得到更強烈的進氣渦流，其整體平均渦旋比為3.784。

關鍵字

計算流體力學 ； 紊流模型 ； 流量係數 ； 渦旋比

並列摘要

This paper focuses on the design of engine intake port geometry, in order to generate strong charge swirling flow. Using computational fluid dynamics commercial software-FLUENT, adopt turbulence model to calculate intake flow field of a single cylinder four-valve motorcycle engine in steady state. To simulate the real condition that engine intake flow test by flow bench. The method is to analyze 3D CAD file directly while engine design. Finally, compare the flow coefficient and the swirl ratio value with experiment data. The result of twin-valve opening of original intake port case displays an accurate prediction while low valve lift and the error is 1.14%. The other one original case by closing right-hand intake valve makes air flow to cylinder tangentially. It will generate swirl then calculate the swirl ratio. The result displays a good accuracy by using high order discrete scheme while wide valve lifts, and the average swirl ratio is 2.041. The error is only 0.443%. Then modify the intake port geometry, design a curve angle to change air flow direction. To achieve the target of engine intake swirling flow design. The result gets stronger swirling flow than second one. The average swirl ratio is 3.784.

並列關鍵字

Computational fluid dynamics ； Turbulence model ； Flow coefficient ； Swirl ratio

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