臺灣博碩士論文加值系統

內燃機汽缸內的燃燒特性是決定引擎性能與污染排放的重要參數，為了增進其燃燒效果，降低污染物之排放，並進而提升整體性能輸出，因此利用增強缸內氣流滾轉運動的方式，以達成上述之目的。本研究利用商業套裝計算流體動力學(computational fluid dynamics, CFD)軟體CONVERGE，針對一部四閥單缸四行程158 c.c.引擎，對屋脊型燃燒室幾何進行最適化研究。在進氣與壓縮行程，在固定轉速5000 RPM時，改變燃燒室屋脊型穹頂幾何形狀，以改變缸內氣流滾轉運動。藉由穹頂幾何形狀修改前後的流場結構，定量分析體平均滾轉比、循環渦度滾轉比等量化指標。本研究發展出一套系統性的方法，可以簡便尋找達成最大體平均循環滾轉比的穹頂幾何參數最佳化程序，共進行46個屋脊形燃燒室幾何設計分析計算。計算結果顯示，進氣傾斜角為主要設計參數，當進氣傾斜角在22⁰時，循環渦度滾轉比會達到最高值。表示當進氣埠傾斜角在22⁰時，氣缸內的滾轉強度最強，有助於空氣與燃料均勻混合。計算結果亦顯示，排氣傾斜角、屋脊圓尾半徑與屋脊上緣之導圓角是與必須主要參數搭配設計的次要參數。最佳化的次要參數設計為排氣傾斜角20⁰、屋脊圓尾半徑7 mm與屋脊上緣之導圓10 mm。在以上的主要參數搭配次要參數設計時可以使得循環渦度滾轉比達到最高值。

The in-cylinder flows in the axial planes of a motored four-valve, single-cylinder, four-stroke engine during the intake and compression strokes at an engine speed 5000 RPM were diagnosed by using computational methods. The engine head had a pent roof configuration. The present research was aimed on probing the influences of the pent roof geometry on the in-cylinder tumble strength. The computations were carried out by the computational fluid dynamic (CFD) software CONVERGE. The in-cylinder cold flow CFD simulation model of the original combustion chamber and the optimized combustion chamber based on CONVERGE software were built and performed. Moderate and intense tumble motion were generated by changing the combustion chamber geometric design. Quantified strengths of the rotating motions in the axial planes were represented by a dimensionless variable tumble ratio, which was defined as the ratio of mean angular velocity of the vortices in the target plane at a certain crank angle to the average angular velocity of the crank. The quantitative results of cycle-averaged tumble ratio indicated the correlation between strengths of tumble motion and combustion chamber geometric design. The calculated results and analyses showed that the primary parameter influencing the tumble ratio was the inlet inclination angle of the pent roof (θ1). The secondary parameters were the pent roof exhaust inclination angel (θ2), radius of pent roof (R1), and radius of pent roof on the upper edge (R2). When optimizing the pent roof design, the primary parameter should be determined prior to the secondary parameters. According to the results, the maximum tumble ratio was observed as the inlet inclination angel, exhaust inclination angel, radius of pent roof, and radius of pent roof on the upper edge were 22⁰, 20⁰, 7 mm, and 10 mm, respectively.

摘要 i
Abstract ii
誌謝 iii
內容 iv
符號索引 ix
圖表索引 xiii
第一章 緒論 1
1.1 研究動機 1
1.2 文獻回顧 3
1.3 研究目的與方法 9
第二章 標的引擎規格 10
2.1 幾何構造 10
2.2 零組件簡介 10
2.3 設計理念 11
第三章 計算方法 12
3.1 計算流力軟體簡介 12
3.2 統御方程式 14
3.2.1 紊流模式 15
3.3 數值計算 18
3.3.1 離散化方程式 18
3.3.2 PISO解法理論 20
3.4 數值模擬 27
3.4.1 計算網格 27
3.4.2 邊界條件 29
3.4.3 初始條件 30
3.4.4 收斂標準 31
3.5 分析參數定義 32
3.5.1 物理參數 32
3.5.2 量化模式 37
第四章 修改屋脊型燃燒室穹頂幾何參數θ1與θ2滾轉之運動計算結果 39
4.1 基礎引擎模型冷流場計算 39
4.1.1 對稱面(y/D = 0, #8), CA = 0⁰ ~ 180⁰ ATDC 39
4.1.2 對稱面(y/D = 0, #8), CA = 210⁰ ~ 360⁰ ATDC 40
4.1.3 對稱偏移面(y/D = 0.203, #5), CA = 0⁰ ~ 180⁰ ATDC 41
4.1.4 對稱偏移面(y/D = 0.203, #5), CA = 210⁰ ~ 360⁰ ATDC 42
4.1.5 對稱偏移面(y/D = 0.339, #3), CA = 0⁰ ~ 180⁰ ATDC 42
4.1.6 對稱偏移面(y/D = 0.339, #3), CA = 210⁰ ~ 360⁰ ATDC 43
4.2 a1模型冷流場計算 44
4.2.1 對稱面(y/D = 0, #8), CA = 0⁰ ~ 180⁰ ATDC 44
4.2.2 對稱面(y/D = 0, #8), CA = 210⁰ ~ 360⁰ ATDC 44
4.2.3 對稱偏移面(y/D = 0.203, #5), CA = 0o ~ 180o ATDC 45
4.2.4 對稱偏移面(y/D = 0.203, #5), CA = 210o ~ 360o ATDC 46
4.2.5 對稱偏移面(y/D = 0.339, #3), CA = 0⁰ ~ 180⁰ ATDC 47
4.2.6 對稱偏移面(y/D = 0.339, #3), CA = 210⁰ ~ 360⁰ ATDC 47
4.3 a7模型冷流場計算 48
4.3.1 對稱面(y/D = 0, #8), CA = 0⁰ ~ 180⁰ ATDC 48
4.3.2 對稱面(y/D = 0, #8), CA = 210⁰ ~ 360⁰ ATDC 49
4.3.3 對稱偏移面(y/D = 0.203, #5), CA = 0⁰ ~ 180⁰ ATDC 49
4.3.4 對稱偏移面(y/D = 0.203, #5), CA = 210⁰ ~ 360⁰ ATDC 50
4.3.5 對稱偏移面(y/D = 0.339, #3), CA = 0⁰ ~ 180⁰ ATDC 51
4.3.6 對稱偏移面(y/D = 0.339, #3), CA = 210⁰ ~ 360⁰ ATDC 52
4.4 a15模型冷流場計算 52
4.4.1 對稱面(y/D = 0, #8), CA = 0⁰ ~ 180⁰ ATDC 52
4.4.2 對稱面(y/D = 0, #8), CA = 210⁰ ~ 360⁰ ATDC 53
4.4.3 對稱偏移面(y/D = 0.203, #5), CA = 0⁰ ~ 180⁰ ATDC 54
4.4.4 對稱偏移面(y/D = 0.203, #5), CA = 210⁰ ~ 360⁰ ATDC 55
4.4.5 對稱偏移面(y/D = 0.339, #3), CA = 0⁰ ~ 180⁰ ATDC 55
4.4.6 對稱偏移面(y/D = 0.339, #3), CA = 210⁰ ~ 360⁰ ATDC 56
4.5 缸內壓縮比 57
4.6 容積效率 57
4.7 缸內平均壓力與溫度 57
4.8 缸內平均溫度 57
4.9 缸內氣體淨質量 58
4.10 紊流動能 58
4.11 滾轉比量化分析 58
4.11.1 隨CA變化的截面平均渦度滾轉比 (TCA) 59
4.11.2 體平均循環渦度滾轉比 63
4.12 討論 64
第五章 修改屋脊型燃燒室穹頂幾何參數R1滾轉之運動計算結果 65
5.1 b7模型冷流場計算 65
5.1.1 對稱面(y/D = 0, #8), CA = 0⁰ ~ 180⁰ ATDC 65
5.1.2 對稱面(y/D = 0, #8), CA = 210⁰ ~ 360⁰ ATDC 66
5.1.3 對稱偏移面(y/D = 0.203, #5), CA = 0⁰ ~ 180⁰ ATDC 66
5.1.4 對稱偏移面(y/D = 0.203, #5), CA = 210⁰ ~ 360⁰ ATDC 67
5.1.5 對稱偏移面(y/D = 0.339, #3), CA = 0⁰ ~ 180⁰ ATDC 68
5.1.6 對稱偏移面(y/D = 0.339, #3), CA = 210⁰ ~ 360⁰ ATDC 68
5.2 b11模型冷流場計算 69
5.2.1 對稱面(y/D = 0, #8), CA = 0⁰ ~ 180⁰ ATDC 69
5.2.2 對稱面(y/D = 0, #8), CA = 210⁰ ~ 360⁰ ATDC 70
5.2.3 對稱偏移面(y/D = 0.203, #5), CA = 0⁰ ~ 180⁰ ATDC 70
5.2.4 對稱偏移面(y/D = 0.203, #5), CA = 210⁰ ~ 360⁰ ATDC 71
5.2.5 對稱偏移面(y/D = 0.339, #3), CA = 0⁰ ~ 180⁰ ATDC 72
5.2.6 對稱偏移面(y/D = 0.339, #3), CA = 210⁰ ~ 360⁰ ATDC 73
5.3 缸內壓縮比 73
5.4 容積效率 74
5.5 缸內平均壓力 74
5.6 缸內平均溫度 74
5.7 缸內氣體淨質量 74
5.8 紊流動能 75
5.9 滾轉比量化分析 75
5.9.1 隨CA變化的截面平均渦度滾轉比 (TCA) 75
5.9.2 體平均循環渦度滾轉比 80
5.10 討論 81
第六章 修改屋脊型燃燒室穹頂幾何參數R2滾轉之運動計算結果 82
6.1 缸內壓縮比 82
6.2 容積效率 82
6.3 缸內平均壓力 82
6.4 缸內平均溫度 83
6.5 缸內氣體淨質量 83
6.6 紊流動能 83
6.7 滾轉比量化分析 84
6.7.1 隨CA變化的截面平均渦度滾轉比 (TCA) 84
6.7.2 體平均循環渦度滾轉比 88
6.8 討論 89
第七章 結果與討論 90
7.1 結論 90
7.2 建議 91
參考文獻 92

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