臺灣博碩士論文加值系統

內燃機是人類運輸的主要動力源，適用於車輛，船舶，飛機等各種運輸方式。然而，多年來內燃機一直依賴石油化工能源，造成許多環境污染和能源危機。因此，國內外學者正在研究減少發動機污染和替代燃料的技術，以解決這些危機。
考慮到二甲醚作為柴油發動機的清潔替代燃料，其優點包括高十六烷值，低自燃溫度和低氮氧化物排放，且柴油發動機僅需進行部份的改裝就能夠燃燒二甲醚。本文的目的是研究於進氣口引入二甲醚的柴油發動機燃燒特性和排放。同時利用田口法獲得柴油引擎最佳操作參數，如二甲醚噴射正時，二甲醚預混比和廢氣再循環(EGR)百分比，用於獲得高制動熱效率（ηb）低NOx、PM2.5、CO、HC和黑煙。同時也進行優化參數發動機和基準柴油發動機之間的ηb，NOX，HC，黑煙和燃燒性能比較。噴油正時與二甲醚流量由電控單元（ECU）控制。實驗結果表明，入口處添加二甲醚和EGR可以顯著降低NOx，PM2.5和黑煙排放，但略有增加CO和HC排放。此外，與基準引擎相比，優化參數的發動機條件有較高的制動熱效率。

The Internal combustion engine is the main power source of the human transportation, and it is applied on the vehicles, ships, aircrafts and other various modes of transport. However, the internal combustion engine has long been dependent on petrochemical energy, causing many environment pollution and energy crisis. Therefore, domestic and foreign scholars have been studying on technology of decreasing pollution and alternative fuels for engines in order to solve these crises.
Considering dimethyl ether as a clean alternative fuel for diesel engines gains its advantage including the high cetane number, low spontaneous combustion temperature and low nitrogen oxide emissions. Also, only moderate modifications are needed to convert a diesel engine to burn dimethyl ether. The purpose of this thesis is to investigate the combustion characteristics and emissions in a neat diesel engine inducting dimethyl ether at the intake port. Simultaneously, the optimal operating factors such as dimethyl ether injection timings, dimethyl ether premix ratios and EGR ratios are obtained for high brake thermal efficiency (ηb), low NOX, PM2.5, CO, HC, smoke, combustion performance and exhaust emissions between the optimal engine and conventional diesel engine are also compared. The injection timings and the quantity of dimethyl ether is controlled by electric control unit (ECU). The experimental results show that inducting dimethyl ether and EGR at the intake port can significantly reduce both NOx, PM2.5 and smoke emissions, but slightly increase in CO and HC emissions. Also, the optimal engine condition gains higher ηb compared with the conventional engine.

Abstract II
Acknowledgement IV
Content V
List of Tables VII
List of Figures VIII
Nomenclature XI
Chapter 1 Introduction 1
1-1. Background 1
1-2. Literature review 2
1-2-1. Dimethyl ether 2
1-2-2. Taguchi method with applications to optimization of engine performances 6
1-3. Motivations and objectives 7
Chapter 2 Theoretical Background 9
2-1. Combustion theory of a diesel engine 9
2-2. Formation of emissions 11
2-2-1. BSCO 11
2-2-2. BSHC 12
2-2-3. Smoke 12
2-2-4. BSNOX 13
2-2-5. Particulate Matter (PM) 13
2-3. EGR ratio 14
2-4. Coefficient of variation 15
Chapter 3 Methodology descriptions 16
3-1. Numerical methods 16
3-2. Detailed chemical kinetics mode 17
3-3. Research methods 18
3-4. Engine combustion mode 18
3-5. Computer program structure of KIVA-3V 19
3-6. Primary parameters setting of KIVA-3V 19
3-7. Taguchi method 20
3-7-1. Experiments design and quality characteristics description 20
3-7-2. Results analyzing and the optimum conditions determining 22
3-7-3. Confirmatory test using optimum conditions 24
3-7-4. Percentage reduction of quality loss 25
3-7-5. Multiple Quality Characteristics Model 26
Chapter4. Experimental facilities 28
4-1. Experimental description 28
4-2. Apparatus 28
4-2-1. Specification of apparatus 28
4-3. Measurement of experimental data 32
4-3-1. Crank angle 32
4-3-2. In-cylinder pressure 32
4-3-3. Speed, horsepower output and load 33
4-3-4. CO/CO2/HC measurement 33
4-3-5. Smoke measurement 33
4-3-6. NOx measurement 34
4-3-7. PM 2.5 (Particular Matter) 34
4-3-8. Brake thermal efficiency ηb 35
4-3-9. Heat release rate 36
4-4. Experimental procedures 37
4-5. Experimental considerations 38
Chapter 5 Results and discussion 39
5-1. Using Taguchi method on combustion performance of a diesel engine with port-inducting DME 39
5-1-1 Statistical Analysis 39
5-1-2 Percentage reduction of quality loss for the optimal engine condition 41
5-1-3 Confirmation experiments 41
5-1-4 Comparison between conventional diesel engine and optimal conditions 42
5-2. Comparison between experiment and simulation 45
5-3. In-cylinder combustion process simulation 46
Chapter 6 Conclusions and suggestion 48
6-1. Conclusions 48
6-2. Suggestion 50
References 51

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