| Ethanol as a renewable fuel is a promising and clean alternative fuel, so ethanol blended with water is used to partially substitute diesel by the mode of diesel/ethanol compound combustion (DECC) in this thesis. This thesis presents that the results about the combustion characteristics of diesel/ethanol dual fuel and how to upgrade emission level based on different CI engine with DECC.A constant volume bomb was used to investigate into the diesel combustion characteristics at the pure air atmosphere and the ethanol atmosphere respectively under the pressure of 3MPa. The results show that, the ignition delay was delayed, the heat release period of high temperature reaction was cut down, and thus the high temperature reaction is promoted by ethanol involved.Through the cylinder pressure obtained on a single cylinder engine modified from a 6-cylinder turbocharged intercooled CR diesel engine, the pressure and temperature in cylinder, the heat release rate, and the indicated diagram can be calculated and analyzed in comparison between the baseline engine and the DECC engine with pure ethanol and the ethanol blended with 30% water by volume. In the DECC mode with pure ethanol, the ignition point is delayed and the heat release rate is sharply increased. While with ethanol blended with 30% water, the ignition time is further delayed and the initial heat release takes up more in the whole combustion process compared with that with pure ethanol in DECC mode.Experimental research on emission characteristics of diesel/ethanol containing water compound combustion (DECC) engine with inline pump, turbocharged and inter-cooled while a diesel oxidation catalyst (DOC) is fixed on exhaust pipe was performed to reduce its NOx and PM emission simultaneously. According to the national phaseⅢspecified test requirement,the NOx from the DECC engine is reduced from 6.49 g/kW·h of the baseline engine to 3.46 g/kW·h,PM from 0.142 g/kW·h to 0.089 g/kW·h , HC from 0.237 g/kW·h to 0.34 g/kW·h , CO from0.081g/kW·h to 0.10g/kW·h. The results are even lower than the national phaseⅢemission standard. The result of ELR (Europe load response test) show the exhaust smoke is 0.687m-1 which is lower than the national phaseⅢemission standard too. It is feasible that the approach to improve exhaust emission quality remarkably by applying DECC mode on turbocharged inter-cooled diesel engine. The exhaust pollutants except PM are satisfactory to the national phaseⅣwhile the fuel economy do not go down. The Fourier transform infrared spectrometer (FTIR), an advanced measure method is used on another 4-cylinder electronic common rail engine with turbocharged inter-cooled to investigate and compare the emission performance between the baseline engine and the DECC mode with the ethanol blended with 30% water including the regulated gas emissions and aldehydes emission before and after DOC. The results show that with DOC the NOx emissions were reduced 4.104 g/kW·h of the baseline engine to 3.034 g/kW·h,PM from 0.079 g/kW·h to 0.068 g/kW·h,HC from 0.209 g/kW·h to 0.094 g/kW·h,CO from 0.59g/kW·h to 0.02g/kW·h. The results also showed that after DOC the emissions of formaldehyde and acetaldehyde are reduced to the same level of baseline engine. Analyzing of economy shows that the DECC mode have a lower equivalent specific fuel consumption and low ethanol substitution diesel fuel ratio, and a high engine efficiency at middle to high speed and middle to heavy load. And the thermal efficiency of DECC engine can be improved 4% higher than the baseline engine generally during whole 13 working conditions.The results from thesis shows that diesel engine with DECC mode possess the potential of reducing NOx emission to limits of the national phaseⅤ. DECC mode provide a new non-SCR technology route while most companies adopt technique of SCR to reducing NOx emission.
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