Abstract
Keywords:
Uniformity index, Unsteady flow, Exhaust manifold, CCC(Close-Coupled Catalyst), PZEV(Partial Zero Emission Vehicle)
Abstract
In recent year, as the current and future emission regulations go stringent, the research of exhaust manifold and CCC (Close-Coupled Catalyst) has become the subject of increasing interest and attention. This study is concerned with the systematic approach to improve catalyst flow uniformity and light-off behavior through the basic understanding of exhaust flow characteristics. Computational approaches to the unsteady compressible flow for exhaust manifold of 4-1, 4-2-1 and buffalo type including CCC system attached to a 4-cylinder DOHC gasoline engine were performed to investigate the distribution of exhaust flow. In this study, through calculation, the effects of geometric configuration of exhaust manifold on flow structure and its maldistribution in front of catalytic converter were mainly investigated to understand the exhaust flow patterns in terms of flow uniformity. Based on the design guidance resulting from this fundamental study, the flow uniformity of 4-2-1 type exhaust manifold demonstrated the more improved exhaust characteristics than those of the 4-1 type and Buffalo type.