Research Of Diesel Engine Combustion Mechanism And Combustion Process In-cylinder Simulation

Simulating the combustion process of diesel engine and studying the fuelcombustion and pollutant formation mechanism is the fundamental approach toimprove the air environment and meet the emission regulations.This paper set n-heptane as an alternative fuel to diesel engine andcalculated the chemical kinetics combustion process of n-heptane inside cylinder.The results showed that HO₂· and OH· are the main radicals that participate thedehydrogenation reaction of n-heptane, HO₂· mainly comes from the two initialreactions of n-heptane, OH· mainly comes from the pyrolysis reaction of H2O2,C₇H_15-1· and C₇H₁₅· are the key dehydrogenation reaction products, CH₂O is thekey aldehyde product, CH₃· and C₂H₅· are the main products of high temperaturepyrolysis reaction, in the high temperature phase, the generation of CO is mainlyfrom the reaction of CH₂O, the generation of CO₂is the result of reactionbetween CO and OH·.Based on the calculation of chemical kinetics, by temperature sensitivityanalysis, composition and reaction rate analysis, a reduced combustion model of n-heptane was got, the reduced model contained43kinds of components and63elementary reactions, calculation results showed that it gave predictions similarto detailed model in the ignition timing, temperature and pressure in-cylinder,thedistribution of intermediate products and combustion products.Last, based on the reduced model, this paper built a new combustion andemission model of diesel engine, the combustion process of135diesel enginewas simulated and the variation of parameters such as turbulent kinetic energy,fuel concentration, temperature in-cylinder, the main intermediate products andNO was obtained.This paper built a combustion model of n-heptane which provided a modelbasis for the combustion process simulation inside cylinder, meanwhile, theresearch of emission reduction techniques provided some theoretical guidancefor the efficient combustion.