Numerical simulation of solid–liquid mixing characteristics in a tank stirred by an improved double-layer 4-pitched blades impeller

Jia Li; Shilong Wang; Bo Yang; Yan He

doi:10.1515/ijcre-2023-0097

Published by De Gruyter October 6, 2023

Numerical simulation of solid–liquid mixing characteristics in a tank stirred by an improved double-layer 4-pitched blades impeller

Jia Li , Shilong Wang , Bo Yang and Yan He

From the journal International Journal of Chemical Reactor Engineering

https://doi.org/10.1515/ijcre-2023-0097

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Abstract

Aiming at the problems of low mixing efficiency and poor uniformity of solid–liquid dispersion caused by double-layer 4-pitched blades turbine, a new impeller is obtained by optimizing the structure of the traditional blade. In order to efficiently apply the improved double-layer 4-pitched blades impeller to the mixing process of DNAN-based explosives, this paper takes the new impeller as the research object, investigating the solid–liquid suspension characteristics of the stirred tank through computational fluid dynamics (CFD). A stirring experiment is designed, and a conductivity probe is employed to measure the local solid particle concentration. After validating the CFD model by experimental results, numerical analysis is successfully used to examine the impacts of stirring speed, layer spacing, impeller height from the bottom and impeller inclination angle on the solid–liquid mixing quality. Results show that the increase of rotational speed can significantly enhance the solid–liquid dispersion efficiency. Meanwhile, the blade structure parameters have an important influence on the homogeneity of solid phase distribution, and the appropriate blade structure can make the particles have a better suspension effect. Moreover, the improved blade has obvious advantages in solid–liquid space homogenization in comparison to the traditional blade under the same stirring conditions.

Keywords: improved double-layer 4-pitched blades impeller; conductivity probe; solid–liquid mixing; stirred tank; computational fluid dynamics (CFD)

Corresponding author: Shilong Wang, State Key Laboratory of Mechanical Transmissions, Chongqing University, Chongqing, 400044, China, E-mail: wang.sl@cqu.edu.cn

Nomenclature

B: width of the blade, mm
C 1: layer spacing, mm
C 2: height from the bottom, mm
C 1,2 , μ: parameters in the standard k–ε model
C avg: average solid volume fraction
C D: drag coefficient
C s: solid volume fraction
D: impeller diameter, mm
D1: diameter of the tank, mm
d: aperture diameter, mm
d s: solid particle diameter, μ m
g: acceleration of gravity, m/s²
H: liquid height, mm
H1: height of the tank, mm
K l s: interphase momentum exchange coefficient
k: kinetic energy of turbulence, m² s⁻²
l: liquid phase
N: stirring speed, r/min
p: pressure, Pa
R: radial of the tank, mm
r: radial coordinate, mm
s: solid phase
t: time, s
u: velocity vector of the phase, m/s
z: axial coordinate, mm
α: impeller inclination angle, °
α i: phase volume fraction
δ: blade thickness, mm
Φ: conductivity, ms/cm
ρ: phase density, kg/m³
Re: Reynolds number
ε: energy dissipation rate of turbulence, m² s⁻³
μ: viscosity, Pa s
μ t , m: turbulent viscosity of the mixture, Pa s
σ k , ε: k and ε turbulent Prandtl number
τ l , s: stress–strain tensor

Research ethics: We can guarantee that our research is carried out in accordance with relevant laws and institutional guidelines. There is no violation of research ethics such as harming study participants and violating the principle of informed consent.
Author contributions: Jia Li: conceptualization, methodology, software, investigation, formal analysis, writing-original draft. Shilong Wang: supervision, writing-review and editing. Bo Yang: supervision, writing-review and editing. Yan He: supervision, writing – review and editing.
Competing interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Research funding: The study was supported by the National Natural Science Foundation of China (no. 51975074), the Natural Science Foundation of Chongqing (no. cstc2021jcyj-msxmX0732), the Innovation Group Science Fund of Chongqing Natural Science Foundation (No. cstc2019jcyj-cxttX0003) and the Self-Planned Task of State Key Laboratory of Mechanical Transmission (no. SKLMT-ZZKT-2022M03).
Data availability: The data associated with this article can be available.

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Received: 2023-05-19

Accepted: 2023-09-09

Published Online: 2023-10-06

Numerical simulation of solid–liquid mixing characteristics in a tank stirred by an improved double-layer 4-pitched blades impeller

Abstract

Nomenclature

References

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