推进式搅拌器固液混合的计算流体力学模拟

CFD simulation of solid-liquid mixing in stirred vessel by propeller agitator

为了研究推进式搅拌器的固液混合性能并为设计和优化提供依据,通过建立其计算流体力学模型,探讨了固体颗粒由沉积在搅拌罐底部的初态达到稳定混合的过程.搅拌器旋转、固液两相混合和罐内湍流分别采用多重参考系法、欧拉模型和标准k-ε离散模型进行模拟,初态颗粒沉积由补丁函数实现.根据流速场、固颗粒分布、力矩与功率数据研究了不同工况对力矩、功率和悬浮状态的影响,并改进底部结构以减少底部沉积.数值仿真结果表明:推进式搅拌器轴向循环显著,颗粒分布较为理想,转速和体积分数增加会提高总力矩和功率,颗粒增大则会减小压力力矩、增大切应力力矩,并且加重沉积;底挡板能够减少底部沉积并且促进颗粒悬浮.所建模型和模拟结果能够有助于加深对推进式搅拌器流场特性的了解,并有利于对其进行设计和优化.

In order to investigate the solid-liquid mixing performance of the propeller agitator and provide foundation for its design and optimization,the process from the initial condition for the granules accumulating on the bottom to the steady condition is simulated by establishing the computational fluid dynamics model. The rotation of the propeller agitator,solid-liquid mixing,and turbulence in the vessel are simulated by the multiple reference frame approach,the Eulerian model,and the standard k-εdispersed model,respectively. The initial accumulation is achieved with the patch function. According to the data of flowvelocity field,solid granule distribution,moments and power,the effects of different working conditions on torque,power and suspension are discussed,and the bottom structure is improved to reduce accumulation. Numerical simulation results indicate that the axial circle of the propeller agitator is obvious,and the granule distribution is ideal. Growth of rotational speed and concentration will increase the total torque and power,and larger granules will aggravate accumulation,reduce pressure moments and raise shear stress moments. Bottom baffles can reduce accumulation and promote granule suspension. The established model and simulation results help understand the flowfield characteristics of the propeller agitator,and are useful for its design and optimization.