CFD and Measurements of a VNT-CCC Configuration: Is It Feasible to Replace Exhaust Pulsations with Constant Flow?

Velocity and temperature distributions in a Close Coupled Catalyst (CCC) were analyzed using two identical Computational Fluid Dynamics (CFD) setups, differing only in inflow boundary conditions: one pulsating and the other constant. The objective was to assess the validity of the common simplification of assuming constant inflow. While several studies have addressed this question, they have focused exclusively on naturally aspirated engines. This study examines a CFD domain featuring a turbine - resulting in fundamentally different flow conditions reaching the CCC substrate. The results demonstrate that exhaust pulsations lead to a more uniform flow within the CCC at a lower temperature. These findings, supported by existing literature, suggest that the assumption of constant inflow should be critically evaluated rather than assumed by default.