臺灣博碩士論文加值系統

由於計算機的速度不斷增快，利用計算流體力學(CFD)軟體來幫助引擎設計變得更方便快速，如何應用CFD軟體來成為引擎設計的工具之一，減少引擎開發的時間及實驗的花費成為目前首要的問題。
本文利用商業計算體力學CFD軟體FLUENT計算單缸機車引擎的排氣管及進氣道流場，進氣道計算是模擬引擎在Flow Bench的測試，研究方法是直接使用引擎設計時的CAD檔案進行分析，主要是針對檔案轉換與非結構性網格的建立進行研究，最後將計算出的流量與流量係數與實驗值作比較，結果發現非結構性網格在進氣閥開度小的時候預測相當準確，進氣閥開度大的時候則高估了8.9%。
排氣管計算部分是將實際的排氣管在電腦中重建檔案，將每個導管以及膨脹室之間的隔板獨立的建立圖形，經過CAD檔案處理，可以快速的改變排氣管設計以及建立網格，計算結果發現膨脹室內壓力分布均勻，內部流場結構複雜。
觸媒特性計算是以一直細管來模擬觸媒中的蜂巢孔洞，計算包含數學模式的建立與設計參數的改變，數學模式包含了觸媒的化學反應以及吸附反應，而設計參數則有管徑、管長，而環境的參數有管壁溫度、入口濃度與入口速度，結果發現管徑與管壁溫度對於CO與HC排放的影響最大。

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. A commercial software package FLUENT was used in this study.
In the inlet flow study, the CAD file of the engine was transformed to IGES and STL formulation, and IGES and STL file was imported into FLUENT to generate unstructured mesh. In order to build up unstructured mesh, the transformation of CAD file was the topic in this study. It was found results of unstructured mesh close to measured data at low valve lift. However, at high vale lift, the deviation was 8.9%.
A real exhaust system model was used in this study. The component of exhaust pipe was sat dividedly. It was convenient to change position or size of exhaust component. The computing result showed that the distribution of pressure in the exhaustion chamber was uniform.
A long tube was assumed to simulate the pipe in the platinum catalyst. The kinetics of carbon monoxide and propylene oxidation were discussed in this study. The five parameters were took into consideration. The computing result showed that wall temperature and pipe diameter was the most influential parameters.

目錄
第一章 緒論
1.1 前言 1
1.2 進氣流場計算 3
1.2.1文獻回顧 3
1.2.2 研究目的及方法 4
1.3 排氣管流場計算 5
1.3.1 文獻回顧 5
1.3.2 研究目的及方法 6
1.4 觸媒特性計算 7
1.4.1 文獻回顧 7
1.4.2 研究目的及方法 7
第二章 進氣系統模型與網格建立 9
2.1 FLUENT簡介 9
2.2 進氣系統固體邊界設定 10
2.2.1 模型建立 10
2.2.2 檔案轉換 12
2.2.3 計算區域固體邊界建立 14
2.3 計算區域網格劃分 17
2.3.1 網格種類 17
2.3.2 進氣道網格比較 18
第三章 進氣系統計算結果與討論 32
3.1 理論模式與邊界條件 32
3.1.1 理論假設 32
3.1.2 統馭方程式 34
3.1.3 邊界條件設定 35
3.2 進氣系統計算結果與討論 36
3.2.1 流場分布 36
3.2.2 壓力分布 39
3.2.3 紊流動能分布 40
3.2.4 流量與流量係數 40
第四章 排氣管模型建立與計算結果 51
4.1 理論模式與邊界條件 51
4.1.1 理論假設 51
4.1.2 統馭方程式 52
4.1.3 邊界條件設定 53
4.2 排氣管模型與網格建立 54
4.2.1 真實排氣管介紹 55
4.2.2 排氣管設計模型建立 55
4.2.3 計算網格建立 57
4.3 排氣管計算結果與討論 58
4.3.1 速度分布 58
4.3.2 壓力分布 58
4.3.3 流量與壓降 59
4.4 排氣管流場計算結論 60
第五章 觸媒特性計算 71
5.1 理論假設與方程式 71
5.1.1 理論假設 71
5.1.2 觸媒反應與數學模式 72
5.1.3 擴散與表面濃度方程式 75
5.2 設計參數與計算結果… 78
5.2.1 參數設定 78
5.2.2 計算數值方法 79
5.2.3 計算結果 81
5.3 討論 84
第六章 結論與未來研究方向 94
參考文獻 96

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