Effects of vibration conditions, spatial confinement and friction on mixing and segregation characteristics of mixed pebble beds for CFETR WCCB blanket

• Published in: Particuology Vol. 85; pp. 268 - 279
• Main Authors: Liu, Yong, He, Chongyang, Wang, Cong, Chen, Lei, Liu, Songlin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2024
• Subjects: Binary pebble bed; Discrete element method; Segregation; Vibration; Vibration; Discrete element method; Segregation; Binary pebble bed
• ISSN: 1674-2001; 2210-4291
• DOI: 10.1016/j.partic.2023.06.018

This paper presents the study of the dynamic characteristics of confined mixed pebble beds with different friction under different vibration conditions using the discrete element method. The λ segregation index is used to quantify the degree of particle mixing or segregation. The percolation, convection and diffusion mechanisms are responsible for the segregation patterns of the mixed pebble. The results show the degree of segregation can be suppressed by decreasing the vibration acceleration or free space height below a threshold. Further simulation reveals the threshold of vibration acceleration or free space height both are related to the bed height increment which determines the strength of the percolation mechanism. In addition, the strength of percolation and convection becomes weaker by decreasing the friction of particles and walls, which makes the pebbled bed remains in a mixed state under vibration. These findings are significant to clarify the main factors behind the three segregation mechanisms and hence provide solutions to retaining the mixed state of the Li2TiO3&Be12Ti mixed pebble bed. [Display omitted] •Effects of vibration conditions, spatial confinement and friction on segregation are studied.•Percolation, convection and diffusion mechanism are responsible for segregation.•Percolation mechanism predominates when vibration acceleration is low.•Suppression effect of confinement is affected by threshold of free space height.•The mixed pebble beds are segregated as the friction coefficient increases.