Experimental and Numerical Investigation of Damage in Diesel Particulate Filter: from material scale to filter scale
Résumé
Diesel Particulate Filter (DPF) permits filtration and soot trapping into a porous ceramic. Periodically, soot is burned to ensure the proper engine operating conditions. In bad controlled on-line regeneration, severe thermal stresses develop which may create micro cracks and macro cracks and loss of filtration efficiency.
The first part of this communication deals with a mechanical characterization of recrystallized SiC DPF samples. The tensile behavior of this cellular structure is characterized at room temperature by three-point bend tests performed on DPF samples. Tests are performed on new and aged samples, the aged material showing a notable different microstructure. The main results obtained during this experimental investigation are stated.
The second part focuses on the analysis of a series of DPF samples damaged during laboratory bench tests, the main objective being to establish a correlation between thermal gradients experienced by the DPF and the density of density of the sample. Observations made with SEM coupled with EDS as well as X-ray Computed Tomography (CT) permitted to exhibit several types of degradation (microcracks, cracks, holes due to phase changes, etc.).
In the last part, the experimental results are compared with first numerical simulation of thermomechanical stresses occurring in the cellular structure of part of the filter. The thermal field applied in the mechanical analysis is obtained using both measurements and computed data from a previously described DPF regeneration coupled model (heat transfer, mass transfer, chemical reactions). An attempt is made to correlate computed maximal stress location and cracking observations on samples.