Theoretical and experimental flow analysis of exhaust manifolds for PZEV

As the current and future emission regulations become stringent, the research on exhaust manifold with CCC (Close Coupled Catalyst) has been the interesting and remarkable subject. To design of exhaust manifold with CCC is a difficult task due to the complexity of the flow distribution caused by the pulsating flows that are emitted at the exhaust ports. This study is concerned with the theoretical and experimental approach to improve catalyst flow uniformity through the basic understanding of exhaust flow characteristics. Computational and experimental approach to the flow for exhaust manifold of conventional cast type, stainless steel bending type with 900 cell CCC system in a 4-cylinder gasoline engine was performed to investigate the flow distribution of exhaust gases. In this study, through calculation, the effects of geometric configuration of exhaust manifold on flow structure and its mal-distribution in monolith were mainly investigated to understand the exhaust flow patterns in terms of flow uniformity. In order to simulate the actual exhaust flow from engine, the simulated dynamic flow bench was designed which was composed of blower, the cylinder head including exhaust system of gasoline engine. Pressure distribution of exhaust manifolds was measured with 5-hole pitot probe. The pressure distribution at the catalyst outlet was tested with simulated dynamic flow bench. Based on the design guidance resulting from this fundamental study, the flow uniformity of stainless steel bending type was compared with that of the cast type one.