| As the car ownership of our country become more and more,motor vehicle exhaust to the environment is becoming more and more serious.There are many solutions to vehicle emissions pollution,such as alternative fuels,the vehicle exhaust purifier and the new combustion mode.Biodiesel,as a result of low manufacturing cost,rich resource,less emissions,high flash point that is convenient for stock transportation,is a kind of ideal alternative fuel for diesel.Because the biodiesel is made up of different types of fatty acid methyl esters,the study of methyl esters has important guiding significance for the combustion characteristics and chemical kinetics mechanism study of biodiesel.But long chain methyl ester has long carbon chain,which is not easy for gasification,not easy to mix and reaction is more complex.It is difficult to study for long chain methyl ester in the actual test.Different methyl esters were studied in a rapid compression machine and the influence of various factors on the fatty acid methyl ester were summarized.The ignition characteristics difference between methyl hexanoate and methyl trans-3-hexenoate were compared and the influence of carbon-carbon double bonds on the fatty acid methyl ester were studied.Through the software CHEMKIN-PRO,simulation model of fatty acid methyl ester were built and sensitivity analysis,path analysis and concentration analysis were studied.The conclusions can be summarized as follows:1.Through the experimental study of methyl octanoate,it is found that the burning of methyl octanoate has negative temperature coefficient phenomenon in different equivalent ratio,top dead center pressure and temperature.Outside the area of negative temperature coefficient,the higher top dead center temperature is,the shorter ignition delay time of methyl ester is.The more equivalent ratio is,the shorter ignition delay time of methyl ester is.In addition,the ignition delay that the equivalent ratio is 1.5 and the equivalent ratio is 1.0 is similar.Furthermore,the higher top dead center pressure is and the shorter the ignition delay time of methyl ester is.2.With the simulation study of methyl ester using software CHEMKIN-PRO,it was concluded that the combustion of methyl octanoate has a single-phase phenomenon,and H2O2 group has a process of first-accumulation and second-consumption.The rise of top dead center temperature will make ignition in advance.First-Level dehydrogenation reaction of methyl octanoate was interacting with HO2,OH and CH3 groups,generating eight kinds of isomers.MO2 j has the largest percentage.OMmj and MO8 j accounted the smallest.The higher top dead center temperature would promote the secondary cracking reaction and suppress the secondary dehydrogenation reaction.The reduction of top dead center pressure reducing will promote the proportion of secondary isomerization reaction and reduce the proportion of the second dehydrogenation reaction.3.With the experimental research and simulation study of methyl hexanoate and methyl trans-3-hexenoate,it is found that the burning of methyl hexanoate has negative temperature coefficient phenomenon.But the existence of carbon-carbon double bond would eliminate the negative temperature coefficient phenomenon.The existence of carbon-carbon double bond would increase the instability of methyl trans-3-hexenoate and react to small groups for generating all kinds of small molecules.And the secondary reaction was more complicated,which had ? cracking,isomerization reaction,dehydrogenation reaction,etc.4.With the experimental research and simulation study of methyl decanoate and ethanol blend fuel,it is found that the combustion of methyl decanoate and ethanol blend fuel has negative temperature coefficient phenomenon.The increase of equivalent ratio will reduce ignition delay time of methyl decanoate and ethanol blend fuel,having influence on the area of negative temperature coefficient.The higher top dead center pressure is,the shorter ignition delay time of blend fuel is. |
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