Development And Simplification Of Detailed Combustion Reaction Kinetic Model Of China Ⅵ Standard Diesel Fuel

The development of an accurate and efficient combustion reaction kinetics model of ChinaⅥstandard 0#diesel fuel is the basis for the coupling calculation of the diesel fuel combustion reaction kinetics model and Computational Fluid Dynamics(CFD)software,which is of great significance to the understanding of the fine flow field structure and pollutant generation mechanism of the diesel fuel combustion process.In this paper,based on the analysis of the component contents and fuel characteristics of ChinaⅥstandard 0#diesel fuel,the appropriate characterized substances were determined,and a detailed combustion reaction kinetic model(detailed model)of ChinaⅥstandard 0#diesel fuel including the generation model of PAH and NO_X was developed.The detailed model was simplified,and the simplified combustion reaction kinetic model(simplified model)and CFD software coupling calculation was carried out and the accuracy of the simplified model was verified.The main work is as follows:(1)The component contents and fuel characteristics of ChinaⅥstandard 0#diesel fuel were measured and analyzed.It was found that the main components were n-alkanes,branched alkanes,cycloalkanes,and aromatic hydrocarbons with mass fractions of 29.58%,21.49%,10.51%and 32.41%,respectively.The density,kinematic viscosity,sulfur content,low calorific value and cetane number were 828kg/m~3,4.5mm~2/s,3mg/kg,43.2MJ/kg,52,respectively.Based on the above measurement results,the characterized substances were determined consisting of n-decane,isooctane,methylcyclohexane and toluene(mole ratio of 0.5,0.05,0.05,0.4)by taking component type,the ratio of hydrogen and carbon atoms,density,low calorific value and cetane value as matching targets.The ChinaⅥstandard0#diesel fuel detailed model was developed by combining the combustion reactions kinetic models of characterized substances and screening and adding PAH and NO_Xgeneration model,including 1109 components and 5426 elemental reactions.(2)The detailed model of diesel fuel was simplified under different pressure and temperature conditions by using Directed Relation Graph(DRG),Directed Relation Graph with Error Propagation(DRGEP)and Sensitivity Analysis(SA)method.Three simplified models of RD5,RD10 and RD20 were obtained by setting three relative errors of 5%,10%and 20%.The coupling calculations of the detailed model,simplified models with Closed Homogeneous Batch Reactor model,Perfectly Stirred Reactor model and Premixed Laminar Flame-Speed model were carried out.The ignition delay period,CO concentration and flame propagation velocity were compared and analyzed.It was found that the RD10prediction performance was good,whose maximum relative errors of ignition delay period,CO concentration,flame propagation velocity were 7.5%,5.0%and 4.0%respectively,consisting 114 components and 991 elemental reactions.(3)The simplified model RD10 of ChinaⅥstandard 0#diesel fuel was coupled with Fluent and Fire software to simulate the combustion characteristics of micro-scale combustion and engine in-cylinder combustion,and the results were compared and analyzed with the test results to verify the accuracy of the simplified model RD10.The results show that the maximum errors of the simulated and test values of flame temperature,height,and width were 8.8%,8.6%,and 8.3%,respectively,under the condition of micro-scale combustion.Under the condition of engine in-cylinder combustion,the maximum errors of the simulated and test values of peak combustion pressure,NO_X and soot were 5.6%,7.9%and 9.2%,respectively.It was indicated that the simplified model of ChinaⅥstandard 0#diesel fuel developed in this paper had a good prediction performance,and had a certain application value in the research of micro-scale combustion and engine in-cylinder combustion simulation.