Construction Of Chemical Kinetic Model Of Ethanol/biodiesel Blended Fuel And Numerical Simulation Study

With the increasingly energy shortage and environment pollution in our country,research the chemical reaction mechanism of fuel deeply and grasp the characteristic and influence factors of engine combustion process can contribute to effective control to combustion process,and provide theoretical foundation to optimize the engine performance.This paper build the simplified chemical kinetic mechanism of ethyl alcohol and the chemical kinetic model of Ethyl Alcohol/biodiesel blended fuel respectively,and coupling with 3D-CFD software.Then research the effect of variated EGR ratio and altitude on biodiesel engine combustion and emission characteristics under the condition of different ethanol blending ratio.This paper firstly based on the detailed mechanism of ethyl alcohol(C2 Small molecule reaction mechanism-Aramco Mech 1.3)and use the directed relation graph method(DGR),the temperature sensitivity analysis method and the reaction rate analysis method to simplify the detailed mechanism of ethyl ethanol.The simplified reaction mechanism including 66 kinds of components,and 66 reactions.Then verify the accuracy of ethyl alcohol simplified mechanism about ignition delay and the variation law of main components,and present a C2H5OH simplified chemical kinetic mechanism with wide range of application by comparing ethanol ignition delay period and premixed combustion experimental data.This paper coupling with the simplified mechanism of three group biodiesel fuel substitutes(NC7H16/MD/MD9D)based on the ethyl alcohol simplified mechanism,and building the ethyl alcohol/biodiesel blended fuel simplified mechanism which include 107 components and 579 reactions with the idea of decoupling.Then verify the based combustion data of dual fuel simplified mechanism such ignition delay period,the mole fraction of species of Jet stirring reactor and laminar flame speed.The result show that the dual fuel mechanism which build in this paper could express the change law of the ignition delay and components under different pressure or equivalence ratio sufficiently,and the combined mechanism could also predict the ethanol laminar flame propagation velocity of blended fuel preferable.This paper uses CONVERGE build numerical simulation model which based on the D19 high pressure common rail diesel engine major parameter and simulate the effect of difference of EGR ratio or altitude on biological diesel engines combustion and emission characteristic by coupling ethyl alcohol/biodiesel altitude chemical kinetics model build in this paper.The research show that:With the EGR ratio increase,the rise phase of combustion pressure in cylinder lag behind,the pressure rise rate increase while the maximum explosion pressure in cylinder showed a trend of decrease,the initial heat release rate rise gradually,the emissions of smoke increase gradually while NOx decrease and the decreasing trend of NOx is more obvious.Under equal EGR ratio condition,increase the ethyl alcohol blending ratio could contribute to the decrease of the peak production of carbon smoke and further oxidation.The dual fuel engine with high blending ratio of ethyl alcohol had low carbon smoke emission.Considering the study about combustion and emission characteristics of ethyl alcohol/biodiesel engine coupling EGR ratio,when the EGR ratio is 20%and the ethyl alcohol blending ratio is 20%(E20 EGR20),the engine could achieve better performance of combustion and emissions.In the research about combustion and emission characteristic of blended fuel engine under different blending ratio and altitude condition,we can draw the conclusion that with the altitude increase,the rise phase of combustion pressure in cylinder lag behind,the pressure rise rate increase,the maximum explosion pressure in cylinder decrease obviously,the initial heat release rate rise gradually,the peak of heat releasing show a trend of decrease,the emissions of smoke increase gradually and the emissions of smoke under 4000m is larger.Under equal altitude condition,with the increase of ethyl alcohol blending ratio,the emission of smoke decrease and the increase of ethyl alcohol could contribute to the reduce of smoke emission under higher altitude.The emission of NOx under low altitude is decrease with blending ratio increase while above 1000m altitude the increase of blending ratio could lead to the emission of NOx increase,especially under higher altitude condition,the trend of increase is more obviously.But the higher the altitude,the final emissions of NOx lower relatively.