Effect of exhaust manifold geometry and engine parameters on flow pulsations inside the exhaust system with CCC under firing conditions

The flow characteristics in the exhaust manifold and close-coupled catalytic converter (CCC) system of a spark-ignition engine have a major influence on its performance and emission characteristics. In particular, understanding the exhaust flow characteristics during engine operation is crucial in terms of shortening the catalyst light-off and enhancing its conversion efficiency. In this study, to understand the pulsating nature of the exhaust flow under engine firing conditions, transient velocity measurements using laser Doppler velocimetry were performed inside an exhaust system with CCC. First, the effects of engine parameters (speed and load) on the pulsating behavior of the exhaust flow were investigated. Moreover, the effects of the exhaust manifold geometric configuration on the pulsating flow characteristics are presented. It is expected that the data obtained from this study can be used to improve exhaust system design for robust emission control in terms of catalyst light-off and durability.