Experimental Study of Pulsating Flow in a Close-Coupled Catalyst Manifold on a Charged Motored Engine using Oscillating Hot-Wire Anemometry

Pulsating flow is generated in a close-coupled catalyst exhaust manifold using a charged motored engine. Flow is very similar to fired engine conditions, featuring blow-down and displacement phases. Bidirectional time-resolved catalyst velocity distributions are measured using phase-locked oscillating hot-wire anemometry.

Temporal and spatial occurrence of flow reversal through the catalyst is examined, and catalyst areas most subjected to backflow are identified. Mean catalyst velocity fluctuations are observed, caused by Helmholtz resonances in the manifold. These resonances are strong enough to induce flow reversal during the displacement phase. Reverse flow is considered important with respect to local thermal deactivation of the catalyst.