Experimental Study On The Effects Of Introduction Of Hydrous Ethanol On Performance Of A Diesel Engine

Bio-ethanol is the highlight substitute of fossil oil in current alternative fuel research.As the world’s most widely used biofuel,how to lower the standard of ethanol purity in the internal combustion engine to reduce its production costs is one of the important aspects of ethanol research.In this experimental research,the diesel and ethanol were introduced in two modes: the blended fuel combustion mode and the dual-fuel combustion mode.The result of combustion and emission characteristics of these two combustion modes has been obtained and discussed in detail.Firstly,to solve the solubility problem of ethanol/diesel blend,the influences of different temperatures,water contents and higher alcohol additives were quantitative researched.On this basis,a suitable higher alcohol was chosen as the co-solvent,and then the hydrous ethanol/diesel blend can be applied on diesel engine.At last,the results on the effects of ethanol purity and injection pressure on diesel engine performance and exhaust emission behaviors were obtained.The experimental results show that high water-containing and low temperature break the stable single-phase of ethanol/diesel,and via utilizing the different higher alcohols can resolve this phenomena.The engine tests demonstrate that a small reduced purity of ethanol corresponds to a prolonged ignition delay,higher combustion pressure and heat release rate.Meanwhile,NOx and THC emissions tend to reduce with a rise of the water content,while CO emissions are nearly the same but present higher CO emissions at low load.Considering the application on the blends of hydrous ethanol and diesel,the boundaries of ideal injection pressure will be narrowed.On one hand,lower injection pressure can worsen combustion easily.On the other hand,higher injection pressure will be easy to result in the combustion roughness,and higher emissions of NOx and CO.Further experiments were conducted to explore the performance of ethanol and diesel in dual-fuel combustion mode.The experimental results show that the increase of the ratio of port injected ethanol(Re)will lead to significant enlargement of the peak heat release rate and the maximum pressure rise rate(MPRR),and a decrease of the combustion efficiency,which all result in the decline of indicated thermal efficiency.But the combustion efficiency decreases with the decline of the ethanol purity,and the peak value of pressure rise rate shows a tendency of firstly goes down and then rises,and finally reaches the minimum value of MPRR when the concentration of ethanol reaches 80%.These results also indicated that the thermal efficiency will be relatively stable in the purity range of 80%-100%,while the range of 60%-80% shows a sharp fall.In addition,CO and THC emissions will increase with the decrease of ethanol purity,while CO emissions are lower and THC emissions are higher under a higher Re.However,it is noteworthy that the reduction of ethanol purity and the increase of Re can reduce NOx emissions,and soot emissions tend to be zero.And besides,the intake air temperature,EGR rate and fuel injection pressure will improve the engine thermal efficiency and emissions under the dual-fuel combustion mode,but the impact of injection pressure is relatively small.