Investigations On Performance Of A Cr Diesel Engine Operating On Decc

Ethanol presents a promising and clean alternative to substitute fossil fuels, at the same time, water can be added to diesel fuel to effectively reduce the NOx and PM emissions of diesel engine, so ethanol blended with varying water is used to partially substitute diesel with the diesel/ethanol compound combustion (DECC) in this paper. In the DECC mode, the ethanol and water blend was injected at the intake manifold and then ignited by pilot diesel fuel, and the proportion of ethanol and diesel varied at different operating conditions.Firstly, through the cylinder pressure gained 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 point 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. The pressure and temperature in cylinder in DECC engine is higher than those in baseline engine at heavy load and high speed, and lower at light load and low speed compared with the baseline engine.Secondly, the Fourier transform infrared spectrometer (FTIR), an advanced measure method is used on another 4-cylinder CR engine to investigate and compare the emission performance between the baseline engine and the DECC mode with the ethanol blended with 30%, 40% and 50% water including the regulated gas emissions and aldehydes emissions before and after DOC. The results show that before DOC the NOx and NO emissions present a reduction trend as the blending ratio of water and ethanol increases. Compared with the baseline engine, the DECC mode with different blending ratio of water and ethanol all increase NO2 emissions as well as NO2/NO ratio with the maximum of 64%. Furthermore, the addition of the ethanol blended water remarkably increases the CO, HC, formaldehyde and acetaldehyde emissions. After DOC, the NOx emission almost keeps the same level, while the ratio of NO2/NO increase to varying degrees compared with those before DOC. The results also showed that after DOC the emissions of HC, CO and formaldehyde are reduced to the same level or even lower than the baseline engine before DOC, while DOC have no influence on the acetaldehyde emissions at the load of 25% in middle and high speed.It shows that the DECC mode have a lower equivalent specific fuel consumption and low ethanol diesel substitution 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 6% higher than the baseline engine generally. Ethanol blended water can be used as a clean and efficient alternative fuel for diesel engines with the DECC mode combined with DOC. If adjust the rational ethanol diesel substitution ratio at appropriate operating condition in the DECC mode, it can effectively improve the engine efficiency and reduce the harmful gas pollutants.