流体机械

2016, v.44;No.526(04) 29-35

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卧式螺旋卸料沉降离心机内部流场与分离性能的研究
Study on the Flow Field and Separation Performance in a Decanter Centrifuge

姜毓圣;袁惠新;付双成;
JIANG Yu-sheng;YUAN Hui-xin;FU Shuang-cheng;Changzhou University;

摘要(Abstract):

卧式螺旋卸料沉降离心机在固液分离领域应用广泛,但由于内部流动复杂、结构封闭且高速旋转,传统的理论与试验方法均无法对其内部流动进行准确描述。本文在合理的简化和假设基础上,应用计算流体动力学软件Fluent,采用SRF转动模型与RSM模型、Mixture多相流模型相结合的方式,对卧螺离心机内的两相流动进行了三维稳态计算,得到了转鼓内的流场和固相体积分数分布。结果显示,轴向速度方向在靠近转鼓壁面处指向转鼓小端,在靠近螺旋内筒处指向转鼓大端,分布受锥段结构影响较大;径向速度复杂多变;颗粒的沉降过程主要发生在转鼓沉降区;转鼓柱段的固相含量少,溢流澄清、固相回收率高;转鼓锥段固相含量集中,且越靠近出渣口的固相体积分数越高。经验证,模拟得到的固相回收率与出渣含固率均接近实际运行情况,说明采用数值模拟方法预测离心机的分离性能具有可行性。
Although decanter centrifuges have been widely used for the separation of liquid-solid mixtures,little attention has been paid to the solid-liquid two phase flow field and the solid concentration distribution inside. Due to the high-speed revolution and closed structure,there is still no method to establish an effective theory to describe the complex internal flow. Base on the reasonable simplification and hypothesis,a computational fluid dynamics( CFD) software Fluent was used to calculate this 3D steady flow field. The research shows that the SRF method combined with RSM turbulence model and Mixture multiphase model is an effective technique to investigate the flow field and the solids distribution in the decanter centrifuge. The CFD results,including the solids recovery and the solid concentration of the sediment outlet,were in good agreement with the industrial experiments. Conclusion can be made that using numerical simulation methods to predict the separation performance of decanter centrifuges is accurate. In the separating zone,axial velocity distribution is determined by the drum structure,which solids travel toward the drum's small end and liquids travel toward the big end. Furthermore,the radial velocity is complicated and varied. Since the particles settle quickly,the settlement process mainly occurs in the middle area of the drum. Sediments are mainly concentrated in the rear of the drum. The closer sediments near the discharge outlet,the higher volume fraction of solid phase.

关键词(KeyWords): 卧式螺旋卸料离心机;离心分离;数值模拟;两相流;分离性能
decanter centrifuge;centrifugation;numerical simulation;two-phase flow;separation performance

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基金项目(Foundation): 科技部科技型中小企业创业基金项目(08C26213200648)

作者(Author): 姜毓圣;袁惠新;付双成;
JIANG Yu-sheng;YUAN Hui-xin;FU Shuang-cheng;Changzhou University;

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