On the use of autocorrelation functions, permeability tensors, and computed tomography to characterise the anisotropy of diesel particulate filter materials

ABSTRACT

We show how the combination of the spatial autocorrelation function and permeability calculations, applied to 3D X-ray computed tomography data, can yield quantitative information on the anisotropy of both meso-structure and fluid flow in Diesel Particulate Filter (DPF) materials, such as Cordierite and SiC. It was found that both the degree of anisotropy, and the orientation of the permeability and meso-structure are similar, but not identical. We confirm that the morphological anisotropy of cordierite materials is weak, and clearly influenced by the extrusion process that determines the main direction of anisotropy. Properties of the autocorrelation function are discussed and it is shown why estimating the characteristic length of real meso-structures (grain or ‘pore’ size) is not possible. Finally, we show that the autocorrelation function applied on grey-level images can give a good estimate of the degree of anisotropy even with limited resolution.

KEYWORDS:

• Anisotropy
• autocorrelation function
• computed tomography
• permeability tensor
• Diesel particulates filter
• ceramics

Acknowledgments

DB acknowledges financial support from BAM, in the frame of the ‘Guest Scientists’ programme. The authors acknowledge the anonymous reviewer for his/her valuable work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data used in this work are available from the corresponding author upon reasonable request and with the permissions of BAM and CNRS.