Failure Analysis and Robust Optimization of an Exhaust Manifold Diffuser Plate

Diffuser plates in exhaust system manifolds are designed to provide uniform flow pattern within the manifold for maximum utilization of the catalytic converter substrate during high-temperature applications. In this paper, failure analysis of a diffuser which survived only 20% duration of a manifold crack test and various design optimization studies of the diffuser plate using computer-aided engineering (CAE) analyses are presented. During the manifold crack test, the failure occurred at the inner and outer periphery of the diffuser. Metallurgical failure analysis coupled with CAE thermal fatigue analysis of the component concluded that thermal fatigue was the root cause of the failure. The new recommended robust design showed considerable improvement in the thermal durability of the diffuser plate assembly.