Abstract
Based on the CFD software Fluent, the multi-reference system method, the RNG κ-ε turbulence model and the pressure-velocity coupled SIMPLEC algorithm are applied to simulate the flow field of a single side-entering agitator in a large biogas digester. And the impact of different installation angle, agitator-to-bottom height, agitating speed and agitator diameter on the agitating power, the effective area percentage and the effective power ratio are analyzed. The results show that: 1) when the agitating speed is more than 450r/min and the agitating diameter is more than 750 mm, the effective area percentage reaches the maximum value; 2) when the horizontal angle is 30 °, the agitating effect is the best; 3) when the vertical angle is inclined to the bottom and the agitator-to-bottom height is less than 8 m, it is helpful to prevent the sediment from appearing. The results of numerical simulation provide a theoretical basis for the design to optimize the agitator.
Highlights
With the rapid development of computational fluid dynamics (CFD) in recent years, some scholars at home and abroad have applied computational fluid dynamics technology to the optimization design of mixing tank through numerical simulation
Asghar[5] studied the effect of the different factors on mixing time of two kinds of crude oil with one side-entering agitator through RNG turbulence model
Zhang Linjin[8] used computational fluid dynamics (CFD) technology to simulate the side-entering agitator flow filed in the bottom of the flue gas desulfurization absorption tower, the influence of the agitating speed and agitating paddle installation angle and other factors on the three-dimensional flow field were studied
Summary
With the rapid development of computational fluid dynamics (CFD) in recent years, some scholars at home and abroad have applied computational fluid dynamics technology to the optimization design of mixing tank through numerical simulation. Wesselingh[4] studied the mixing time of different size single-side agitator, and analysed flow field with multiple factors such as paddle type, propeller angle, Reynolds coefficiency, and so on. Asghar[5] studied the effect of the different factors on mixing time of two kinds of crude oil with one side-entering agitator through RNG turbulence model. Fang Jian[6,7] carried out the numerical simulation of the fluid flow and mixing process in the tank with 4 side-entering agitators, and the power curve was obtained. Zhang Linjin[8] used computational fluid dynamics (CFD) technology to simulate the side-entering agitator flow filed in the bottom of the flue gas desulfurization absorption tower, the influence of the agitating speed and agitating paddle installation angle and other factors on the three-dimensional flow field were studied. Zheng Xiaodong[9] studied the effect of the installation position, the ventilation rate, the solid particle concentration and the liquid level on the particle suspension performance in the side-entering mixing tank
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