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研究生： 王聖丰
Wang, Sheng-Feng
論文名稱： 車輛排氣管之流場量測與數值模擬
Experimental Measurements and Numerical Simulation of Pulsating Flow in a Vehicle's Exhaust Pipe
指導教授： 梁勝明
Liang, Shen-Min
學位類別： 碩士
Master
系所名稱： 工學院 - 航空太空工程學系
Department of Aeronautics & Astronautics
論文出版年： 2006
畢業學年度： 94
語文別： 中文
論文頁數： 99
中文關鍵詞： 四行程引擎 、二種無因次化時間尺度方法 、脈衝波
外文關鍵詞： four-stroke engine, pulsating waves, two dimensionless time scaling
相關次數： 點閱：60  下載：2 
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    • 車輛引擎經動力行程產生的廢氣，經由排氣管排放至大氣中，而排氣管內高溫高壓的廢氣帶有脈衝波，脈衝波會引發壓力振盪，廢氣流速亦會有振盪現象發生。本研究採用實驗以及數值模擬兩種方法來探討簡化之排氣管內基本流場的性質及爆炸波壓力傳遞的情況，在壓力量測實驗部份，使用PCB之壓力探針，在不同引擎轉速下，量測排氣管內各量測點之壓力瞬時變化，並使用U形管量測管入口處之平均壓力；在溫度量測實驗部份，使用K型熱電偶同時量測六個量測點的溫度；在管出口處平均流速量測實驗部份，使用皮托管與U形管量測排氣管出口處的平均流速。
    在數值模擬方面，採用空間五階基本加權不振盪法(WENO scheme)及四階Runge-Kutta時間積分法建立ㄧ維尤拉方程解子，並考慮摩擦與熱傳效應，並利用不同的無因次化時間來模擬基本流場與加入爆炸波後之流場性質，經由比較數值結果及實驗數據發現，可以準確地預測排氣管各實驗量測點在不同引擎轉數下的壓力峰值、平均溫度以及管出口處之平均流速。

    The process of power stroke of a vehicle’s engine produces exhaust gas which flows through the exhaust pipe into the atmosphere. The exhaust gas of high temperature and high pressure has pulsating waves. These pulsating waves induce oscillation of pressure and oscillation of flow velocity. We use a simplified exhaust pipe for numerical simulation and experiments to study the flow field properties of a basic flow and the propagation of the pulsating blast waves. For the pressure measurement, a PCB pressure sensor is used to measure pressure variations at these check points for different engine speeds. We use a U-shape tube to measure the time-mean pressure at pipe’s entrance. For the temperature measurement, K-type thermocouples are used for measuring six check-point temperatures simultaneously. For the flow speed measurement, a pitot tube and a U-shape tube are used to measure the flow speed at the outlet for the exhaust pipe.
    A time-dependent one-dimensional Euler system with source terms of friction force and heat transfer is solved by using a high-resolution method of a fifth-order weighted essential non-oscillation scheme for spatial derivatives and a forth-order Runge-Kutta method for time integration. We adopt two different dimensionless time-scaling strategies to simulate the basic flow and the propagation of pulsating blast waves. Computed results are compared with the experimental data, it is found that the present numerical simulation well predicts the aforementioned flow properties of the exhaust pipe at these check points under different engine speeds.

    中文摘要......................................................................I 英文摘要.....................................................................II 誌謝.........................................................................IV 目錄..........................................................................V 表目錄.....................................................................VIII 圖目錄.......................................................................IX 符號說明...................................................................XIII 第一章 緒 論..................................................................1 §1.1 簡介.....................................................................1 §1.2 文獻回顧.................................................................3 §1.3 研究動機與方法...........................................................5 第二章 物理問題與數學模式.....................................................6 §2.1 物理問題.................................................................6 §2.1.1 四行程引擎循環之作動..................................................7 §2.1.2 排氣管與消音器........................................................9 §2.2 數學模式................................................................11 §2.2.1流體統御方程式之積分式和微分式........................................12 第三章 數值方法..............................................................17 §3.1 加權基本不震盪法........................................................17 §3.2 加權基本不震盪法應用於尤拉系統(Euler system)............................21 §3.3 時間積分................................................................22 §3.4 時間間隔................................................................22 §3.5 初始條件................................................................23 §3.6 邊界條件................................................................23 §3.7 收斂方法................................................................24 第四章 時驗設備與方法........................................................26 §4.1 實驗車輛................................................................26 §4.2 壓力量測設備與方法......................................................29 §4.2.1 壓力探針..............................................................29 §4.2.2 示波器................................................................31 §4.2.3 動態壓力量測方法.....................................................32 §4.2.4 排氣管入口處平均壓力量測設備與方法...................................37 §4.2.5 壓力探針、U型管與排氣管銜接方式......................................40 §4.3 溫度量測設備與方法......................................................42 §4.3.1 資料擷取器...........................................................42 §4.3.2 熱電偶...............................................................43 §4.3.3 溫度量測方法.........................................................44 §4.4 排氣管出口處之平均流速量測設備與方法....................................47 §4.5 噪音量測設備與方法......................................................49 §4.5.1 B&K麥克風............................................................49 §4.5.2 噪音量測方法.........................................................50 第五章 結果與討論............................................................54 §5.1 實驗結果................................................................54 §5.1.1 壓力量測實驗數據.....................................................54 §5.1.2 溫度量測實驗數據.....................................................55 §5.1.3 排氣管出口處之平均流速量測實驗數據...................................56 §5.1.4 排氣管出口下游處之噪音值量測實驗數據.................................57 §5.2 數值結果................................................................58 §5.2 .1 格點的選擇..........................................................58 §5.2.2 平均熱對流係數與摩擦係數之估算.......................................58 §5.2.3 基本流場計算結果.....................................................59 §5.3 加入爆炸波之流場計算結果................................................61 §5.4 排氣管流場分析..........................................................63 §5.4.1流場質量流率分析......................................................63 §5.4.2 Choking分析..........................................................63 第六章 結論..................................................................65 參考文獻.....................................................................67 自述........................................................................100 著作權聲明..................................................................101

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