Effects of volumetric fraction and included angle of composite particles on the discharge of binary mixtures in hoppers--颗粒学报PARTICUOLOGY

Ge, L., Gui, N., Yang, X., Tu, J., & Jiang, S. (2020). Effects of volumetric fraction and included angle of composite particles on the discharge of binary mixtures in hoppers. Particuology, 51, 80-90. https://doi.org/10.1016/j.partic.2019.10.003

Effects of volumetric fraction and included angle of composite particles on the discharge of binary mixtures in hoppers

Liang Ge ^a, Nan Gui ^{a *}, Xingtuan Yang ^a, Jiyuan Tu^{a b}, Shengyao Jiang ^{a *}

a Institute of Nuclear and New Energy Technology, Collaborative Innovation Center of Advanced Nuclear Energy Technology, Key Laboratory of Advanced Reactor Engineering and Safety, Ministry of Education, Tsinghua University, Beijing 100084, China
b School of Engineering, RMIT University, Melbourne, VIC 3083, Australia

10.1016/j.partic.2019.10.003

Volume 51, August 2020, Pages 80-90

Received 7 March 2019, Accepted 7 October 2019, Available online 3 December 2019, Version of Record 11 April 2020.

E-mail: guinan@mail.tsinghua.edu.cn; zjuguinan@zju.edu.cn; shengyaojiang@sina.com

Highlights

• Discharge of composite particles of differing angle α & fraction χ is studied by DEM.

• Discharge rate declines as angle α and fraction χ of multi-sphere particles increase.

• Steady (mass flow) & free (funnel flow) stages of discharge are identified.

• α & χ affect radial velocity which distinguishes central region from annular region.

• Mean force increases with χ, thereby explaining effect of α & χ on discharge.

Abstract

The discharge behavior of particles is important in many industrial applications, such as in the core of a pebble bed reactor, which uses a hopper bed filled with many large particles. In this work, a mixture composed of two particle types, freely discharged from a pebble bed, is simulated using the discrete-element method. One is a spherical pebble of diameter equal to that of the fuel pebble of the reactor. The other is a composite particle comprising three spherical pebbles bonded together. The included angle α of the three pebbles characterized the particle conformation, which may affect the discharge behavior of the mixture. The effects of volume fraction of the multi-sphere χ (equivalent to the number fraction) on the discharge are also analyzed. Flow patterns, number flow rate, discharge velocity, and mean force of the mixture are computed to help in revealing discharge features. The results show that increasing either α or χ reduces the discharge flow rate. Fittings and correlations give a quantitative evaluation of the independent effects of α and χ. The analysis of velocity and force explains the mechanism relevant to the main influencing factors α and χ. The results are helpful in gaining a better understanding of the discharge feature of binary mixtures and in providing a quantitative evaluation of the discharge behavior of the reactor core, especially adverse failure conditions.

Graphical abstract

Keywords

Pebble flow; Particle flow; Discharge flow; Hopper bed; Binary mixture; Discrete element method

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