| To solve the energy shortage and environmental protection,there is a wave of searching for new energy in the world.Biodiesel and alcohols,which have the advantage of low pollution,reproducible and high energy,are got more and more attention of scientists.Biodiesel is mainly made up of saturated and unsaturated fatty acid methyl esters and ethyl esters.Because biodiesel is a complex mixture,it can not be directly performed combustion experiment.Usually,domestic and foreign scientists use biodiesel alternative or alternative mixture,which has simple structure but can reproduce combustion characteristic of biodiesel,to conduct experiment.In this paper,the methyl crotonate(MC)and ethyl acrylate(EA)are chosen as the biodiesel alternative and the four butanol isomers and 1-hexanol are selected as the long chain biological alcohols.The details of the work are as follow:Firstly,in order to analyze the combustion characteristics and detailed chemical reaction path ways of four butanol isomers in blend fuels,we computationally research the combustion characteristics of H2 addition on lean flames of four butanol isomers and distinguish H2 chemical effects and dilution/thermal effects on the four butanol isomers flames.The results show that,the influence of H2 effects on the four butanol isomers combustion is not obvious,H2 chemical effects can increase mole fraction of the major species,intermediate stable species and radicals,but H2 dilution/thermal effects decrease that;isomerization has an important influence on the butanol combustion,acetylene mole fraction is the highest under n-butanol and the lowest under t-butanol,propargyl concentration is the highest under n-butanol and the lowest under s-butanol,acetaldehyde mole fraction is the highest under s-butanol.Secondly,the effects of four butanol isomers on the C5 unsaturated esters combustion are researched by opposed-flow diffusion flames and the reasons for variation of combustion characteristics are analyzed.The results show that,because of the different chemical reactivity between fuels,the EA combustion is delayed and the MC combustion is promoted by n-butanol,the EA oxidation is promoted and the MC oxidation is delayed by i-butanol,s-butanol and t-butanol;the C mole fraction of butnaol is a little higher than unsaturated esters on the same volume,so the concentration of carbon monoxide and carbon dioxide is increased by butanol;on the basis of the chemical reaction path way of fuels,the ethylene and acetaldehyde concentration in EA flames and the propylene mole fraction in MC flames are higher,the strength of effects of t-butanol on promoting the propane and n-butene concentration in EA and MC flames is strongest,as well as the effects of s-butanol on increasing the acetaldehyde mole fraction in EA and MC flames.Lastly,the 1-hexanol effects on the EA and MC combustion characteristics are studied by opposed-flow diffusion flames and the differences between the effects of n-butanol and 1-hexanol on C5 unsaturated esters combustion characteristics are distinguished.The results show that,because of the different chemical reactivity between 1-hexanol and unsaturated esters,the EA combustion is almost invariant and the MC oxidation is delayed by 1-hexanol;the blend fuels can produce more carbon monoxide and carbon dioxide for the C mole fraction of 1-hexanol is higher than unsaturated esters on the same volume;comparing with unsaturated esters,the chemical reaction path way of relevant species of 1-hexanol is more direct and efficient,so the majority species concentration in EA and MC flames is obviously increased by 1-hexanol;the C mole fraction and the active radicals concentration via chain reaction of 1-hexanol are higher,the strength of the effects of 1-hexanol on promoting the mole fraction of carbon monoxide,methane,ethylene,acetylene and acetaldehyde in EA flames and the concentration of methane,ethylene and acetaldehyde in MC flames is stronger than that of n-butanol. |
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