偏心双轴搅拌用于污泥搅拌混合的数值模拟

Numerical simulation of mixing on sludge with eccentricity double-impeller

在大型污泥搅拌机中探索采用偏心双轴搅拌,使用Fluent软件对偏心双轴搅拌槽内污泥流体的流场变化进行数值模拟,并与中心双层搅拌进行比较,分析2种结构搅拌槽内宏观流场结构、速度分布及功耗特性,通过实验测量不同转速下偏心双轴的功耗,仿真计算结果和实验值吻合较好。结果表明:偏心双轴搅拌形成的流场结构打破了中心搅拌的流场对称性,有效的消除了隔离区。偏心双轴搅拌槽内流场各方向的速度分量均比中心双层搅拌有明显的提高,速度梯度较大,能够增大搅拌混合区,有利于污泥固液两相的混合。在N=5 r·s^(-1)时偏心双轴搅拌的功耗约为中心双层搅拌的90.4%,具有明显的节能效果。

The effects of the application of an eccentric double-impeller within a large stirred tank system were explored in this study. Specifically, numerical simulations of the granular sludge flow field in a stirred tank e- quipped with an eccentric double-impeller and one equipped with a centered double-impeller were conducted by using Fluent software. Then, numerical analyses of the flow pattern, velocity distribution, and power consump- tion in the above two systems were carried out based on the simulation results. Moreover, power consumption lev- els for the eccentric double-impeller system under different rotational speeds were also measured in experiments. The results showed that the simulated results corresponded well with the experimental ones. The flow pattern caused by the eccentric double-impeller was asymmetrical, and this destroyed the isolated region and improved the mixing efficiency. The flow velocity and velocity gradient induced by the eccentric double-impeller were both higher than those induced by the centered double-impeller, which expanded the stirring region and made the mixing of the solid-liquid two-phase material more efficient. The power consumption for the eccentric double-im- peller under 5 r · s^-1 rotational speed was just 90.4% of that of the centered double-impeller.