Conjugate Heat Transfer and Thermo-Mechanical Heat Cycle Analysis of an Automotive Exhaust Muffler System 2015-01-0327

Recent progress in computer-aided engineering (CAE) has made it possible to model complex interdisciplinary multiphysics analyses. This paper investigated the sequential coupled thermal-structural analysis by examining the associated thermal stresses under simulated operational conditions close to the real situation. An evaluation of exhaust muffler strain due to thermal stresses was made by coupling Star-CCM+ CFD software and ABAQUS FEM structural analysis software. The study was made to evaluate discovered muffler durability test failure and to develop a countermeasure design. Failure of the muffler internal pipe was discovered after heat cycle durability testing. The internal pipe had broken into two pieces.

In the first step, CFD analysis was done by thermo-flow simulation to determine the resulting heat distribution on the muffler assembly when subjected to the prescribed peak duty cycle temperature. The temperature distribution in fluid region in the vicinity of the solid part was subsequently mapped onto the parts' surface and the corresponding FEM nodes using CFD software. In the next step, the nodal temperature values were input as additional boundary conditions using the PREDEFINED FIELDS card. Additional material mechanical properties with temperature dependent characteristics, including the thermal expansion coefficient, were also input into the model. Correlation of the CAE analysis results were then made with the physical test data. In the final step, the FEM modified model was used to develop countermeasures, which satisfied the heat cycle durability test specifications, with alternative internal muffler parts design.