| The fuel combustion chemical reaction mechanism is one of the most effective tools for researching and optimizing the combustion process of internal combustion engines.However,it is impossible to develop a mechanism that includes all components of diesel.It is currently feasible to design a multi-component fuel as an substitute fuel for diesel fuel based on the important components of actual dieselThis study developed a new simplified mechanism for the replacement of n-heptane-n-butylbenzene-methylcyclohexane-PAH multicomponent diesel fuel.Among them,n-butylbenzene and methylcyclohexane(MCH)are regarded as representative substances of aromatic hydrocarbons and cycloalkanes,respectively.Firstly,the detailed mechanism of MCH was reduced by using DRQ DRGEP,sensitivity analysis and ROP.A simplified chemical kinetics model of n-heptane-n-butylbenzene-methylcyclohexane-PAH multi-component diesel substitute fuels containing 183 components and 777 reactions was established by coupling the reduce MCH sub-mechanism into the simplified mechanism of n-heptane-n-butylbenzene-PAH.Then the sensitivity analysis method was used to optimize the key dynamic parameters of the MCH model.Finally,the optimized multi-component diesel reduced mechanism was verified by experimental data such as laminar flame velocity,ignition delay and premixed flame component concentration.The results show that the mechanism can simulate the combustion characteristics of diesel.The reaction pathways of n-butylbenzene and MCH were analyzed.It was found that n-butylbenzene formed a indene,A1-,A1CH3-group and A1C2H3 substance after a series of reactions such as dehydrogenation;while MCH formed AlCH3 and C6H6 substances after dehydrogenation.These groups and substances produced by n-butylbenzene and MCH promote the formation of sootIn order to investigate the effect of n-butylbenzene and MCH on soot formation,this study used the above-mentioned mechanism coupled with CFD software CONVERGE to simulate the combustion process of n-butylbenzene and MCH in a constant volume combustion bomb device.By analyzing the reaction pathway of soot,it is proved that adding n-butylbenzene and MCH in n-heptane has synergistic effect on soot formation.Finally,the mechanism was coupled with CFD software CONVERGE to simulate the combustion and emission process of the actual diesel engine at different EGR rates.The results show that the calculation results of cylinder pressure,heat release rate,CO,NOx and soot obtained by this mechanism are in good agreement with the experimental data,indicating that the newly developed multi-component diesel redLuced mechanism can simulate the combustion and emission of actual diesel engines.The simplified model of multi-component diesel substitute fuel developed in this study provides a model basis for simulating the combustion and emission process of diesel engine in-cylinder.Therefore,the simplified mechanism of multi-component diesel with four or more components can be developed based on this mechanism,which has practical significance for further improving the diesel combustion mechanism,especially the formation mechanism of soot. |
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