Modifying an Intake Manifold to Improve Cylinder-to-Cylinder EGR Distribution in a DI Diesel Engine Using Combined CFD and Engine Experiments 2001-01-3685

Improved cylinder-to-cylinder distribution of EGR in a 2-L Direct-Injection (DI) Diesel engine has been identified as one enabler to help reach more stringent emission standards. Through a combined effort of modeling, design, and experiment, two manifolds were developed that improve EGR distribution over the original manifold while minimizing design changes to engine components or interfering with the many varied vehicle platform installations.

One of the modified manifolds, an elevated EGR entry (EEE) approach, provided a useful improvement over the original design that meet Euro-II emission standards, and has been put into production as it enabled meeting the Euro III emissions requirements a year early. The second revision, the distributed EGR entry (DEE) design, showed potential for further improvement in EGR distribution. This design has two EGR outlets rather than the one used in the original and EEE manifolds, and was first identified by modeling to be a promising concept. Using rapid prototype parts with variable geometry, over 40 variations of the DEE concept were studied experimentally in an attempt to identify an improved configuration. Parallel CFD modeling studies of just a few configurations pointed to a much-improved design, while the experimental methods used to determine EGR distribution sometimes gave quite misleading results. CFD modeling further identified why the experimental results were sometimes conflicting.