4738 Numerical Analysis of the Effect of EGR Gas Heterogeneity on HCCI Combustion
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We analyzed the interrelationship between mixture heterogeneity and reaction in a homogeneous charge compression ignition (HCCI) combustion, using the Large Eddy Simulation (LES) in conjunction with a reaction kinetics model. The aim of this analysis is to find the statistical characteristics of the mixture heterogeneity in turbulent flow field for moderating the HCCI combustion and for increasing an output limit, which is restricted by an intense knock. Several different initial conditions of EGR gas heterogeneity were given at the intake valve closing time. The auto-ignition and combustion behaviors were analyzed for several different sets of the rms of the fluctuations in the EGR gas fraction and temperature. The analyses show that the heterogeneous distribution of an EGR gas gives a considerable effect to make the combustion slower, even when a fuel-air mixture is homogeneous in equivalence ratio.
