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Exhaust Gas Recirculation (EGR) is employed widely in compression-ignited engines and currently under consideration for being implemented into spark-ignited engines. EGR cylinder-to-cylinder dispersion is one of the features of such engines that developers are challenged to abate, because low EGR rates increase NOx emissions and excessive EGR rates can produce a significant amount of particulate matter. Taking into account the complex geometries of some automotive manifolds, the treatment of this topic through 3D computational fluid-dynamics (CFD) simulations seems mandatory to study the transport phenomena in a proper way. The main objective of this work is the analysis of the influence of the numerical setup main parameters (mesh, time-step size, turbulence modeling) in a CFD URANS simulation of an automotive engine intake manifold in the EGR distribution.

The purpose of this paper is to describe a methodology based on experimental and theoretical studies for the modeling of typical exhaust systems used in two-stroke small engines. The steady and dynamic behaviors of these systems have been measured in a flow test rig and in an impulse test rig, respectively. Information obtained from these experiments is used in two ways: to find a suitable geometric model to be used in a finite-difference scheme code, and to provide a mean pressure and a frequency domain reflecting boundary, in the frame of a hybrid method. A complete 50cc engine was modeled and comparisons between predicted and measured instantaneous pressure at the exhaust port show a fair agreement, the results of the hybrid approach being more accurate.