臺灣博碩士論文加值系統

This research was conducted to investigate the effects of H2 addition, engine load, and diesel fuel flow rate on the brake thermal efficiency (BTE), in-cylinder pressure, heat release rate, exhaust temperature and exhaust emissions of Oxides of Nitrogen (NOx), Carbon Monoxide (CO), unburned Hydrocarbon (HC), Carbon Dioxide (CO2) and smoke. The engine load was varied from 25 to 100% with H2 concentration in the intake mixture (H2/(H2+Air), vol.) varied from 3 to 7% at engine speed 1650 RPM.
The combustion analysis illustrated that the effect of the addition of H2 on combustion process depended on the load and the amount of H2 added. The addition of H2 at 25% load substantially deteriorated the premixed combustion but slightly enhanced and elongated the diffusion combustion. Conversely, the addition of H2 at 70% and 100% loads substantially increased the peak cylinder pressure, rate of pressure rise and peak heat release rate with slightly advance of phasing. In addition, adding hydrogen has small effect on the cyclic variation of combustion of H2-diesel mixtures in a diesel engine.
For emissions, the addition of H2 shows that there was a slight reduction of the emissions of CO except for 100% engine load. Furthermore, the better combustion of hydrogen fuel and the absence of carbon atom in hydrogen molecule are the reasons leading to the decreases of CO2 emission and opacity. Especially, at 75% load, the change of CO2 emission was significant and the largest reduction of CO2 was obtained 32.3% with 7% H2 addition compared to neat diesel fuel. Although there was not different in HC emissions with and without H2 supplement they tended to decrease in H2-diesel dual fuel operation. In addition, the good effect H2 addition on PM was also found at 50% and 75% engine loads.
The improvement to the BTE has been one of the main objectives of this engine research. Unfortunately, the addition of a relatively large amount of H2 (3-7%) at different engine loads did not improve the BTE of the engine. At 25% load, the brake thermal efficiency reduced about 30% at 7% H2 enrichment while the values were 17.5%, 13.1% and 10.6% when engine loads were 50%, 75% and 100%, respectively, with the same amount of H2 addition. It is found that unburned H2 was main reason for reduction of BTE, obviously at low and medium loads.
The measured exhaust temperature increased gradually at all tested engine loads. In particular, the exhaust temperature at 7% H2 added rose 7.4%, 10.4%, 11% and 12.3% when engine run at 25%, 50%, 75% and 100% of load, respectively. Besides, the higher temperature combustion caused increase of the NOx emissions for all cases of H2 addition.

Acknowledgement i
Abstract ii
Table of contents iv
List of Tables x
Nomenclature xi
Chapter 1 INTRODUCTION 1
1.1 Preface 1
1.2 Objective 3
Chapter 2 LITERATURE REVIEW 4
2.1. Diesel engine operation 4
2.1.1 Ignition delay (ID) phase (ab) 5
2.1.2 Pre-mixed combustion phase (bc) 7
2.1.3 Mixing controlled combustion phase (cd) 7
2.1.4 Late combustion phase (de) 8
2.2 Indirect Injection Diesel Engines 8
2.3 Direct Injection Diesel Engines 9
2.4 Exhaust Gas Emissions 10
2.4.1 Carbon Dioxide (CO2) 10
2.4.2 Carbon Monoxide (CO) 11
2.4.3 Unburned Hydrocarbon (HC) Emissions 12
2.4.4 Nitrogen Oxides (NOx) 13
2.4.5 Particulate Matter (PM) 14
2.5 Hydrogen Application as Fuel 15
2.5.1 Features of Hydrogen for Engine Applications 16
2.5.2 Limitations Associated with Hydrogen Engine Applications 17
2.5.3 Application of H2 in Diesel Engines 18
Chapter 3 EXPERIMENTAL ENGINE AND INSTRUMENTATION 22
3.1 Test Engine 22
3.2 Dual Fuel System Setup 25
3.3 Dynamometer 27
3.4 Cylinder pressure measurement system 30
3.4.1 GH13P AVL pressure transducer 31
3.4.2 Advantech USB-4716 Data Acquisition 33
3.4.3 Charge amplifier 34
3.4.4 Optical rotary encoder 35
3.4.5 Calibration of Crank angle measurement 36
3.5 Fuel consumption measurement 38
3.6 Intake air measurement of engine 39
3.7 Exhaust gas measurement 41
3.8 Oxygen (O2) measurement 43
3.9 PM measurement 44
3.9.1 PM diluted tunnel sampling system 44
3.9.2 Filter paper conditioning process 45
3.9.3 PM mass concentration calculation: 45
3.10 H2 emission measurement 46
3.11 Brake Specific Calculation 47
3.12 Calculating cylinder volume change 47
3.13 Heat release rate 49
3.14 Indicated mean effective pressure (IMEP) 51
3.15 Cycle variation of the combustion process 52
3.16 Ignition delay 53
3.17 Brake thermal efficiency (BTE) 54
3.18 H2 combustion efficiency 55
Chapter 4 COMBUSTION CHARACTERISTICS 56
4.1 At 25% engine load 56
4.2 At 50% engine load 59
4.3 At 75% engine load 61
4.4 At 100% engine load 64
4.5 Ignition delay 66
4.6 Indicated Mean Effective Pressure (IMEP) 67
4.7 Coefficient of Variation (COV) 68
Chapter 5 PERFORMANCE AND EMISSIONS 70
5.1 Energy share in dual fuel operation 70
5.2 Brake Thermal Efficiency (BTE) 71
5.3 Combustion Efficiency of Hydrogen 73
5.4 Carbon Dioxide (CO2) emission 77
5.5 Carbon monoxide (CO) emission 78
5.6 Hydrocarbon (HC) emissions 80
5.7 Opacity 81
5.8 Emissions of Nitrogen oxides (NOx) 82
5.9 Particulate matter (PM) 84
5.10 Oxygen concentration in exhaust gas 85
5.11 Exhaust temperature 87
Chapter 6 CONCLUSIONS 88
References 91

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