穿流型搅拌器结构参数优化

Optimizing structural parameters of punched impeller

在特定搅拌槽条件下,针对穿流式斜叶桨式搅拌器,在常用的最高转速300 r/min以内,就开孔位置、开孔率、开孔直径等结构参数进行了数值模拟.将搅拌器以及附近区域都设为动区域进行模型简化处理,基于四面体网格对模型进行网格划分,采用多重参考系稳态处理法,选用标准k-ε湍流模型求解搅拌流场.引入搅拌系数K,从混合效果和功率消耗两方面综合评价搅拌器的优劣.搅拌功率实验和分布时间实验较好地验证了数值模拟的结论.研究表明,相较于传统搅拌桨,穿流式搅拌桨因能强化涡流扩散、减小桨叶投影面,可获得更好的混合效果和更低的功耗,且随着搅拌转速的增大,功耗降低的越明显;搅拌功率和混合时间随开孔率和开孔直径而变化,当开孔率为12%左右、开孔直径为8 mm左右时,搅拌功率和混合时间最小,最为优化.

Aimed at punched agitator with pitched blade, the structural parameters of hole position, hole diameter and opening rate were numerically simulated in specific stirring tank. The agitator and its surrounding area were set as moving area for simplified treatment of model. Based on tetrahedral mesh of the model grid,the standard k-ε turbulence model and moving reference frame were used to solve steady-state mixing flow field. Mixing coefficient was introduced to evaluate the combination property of stirrer from the mixing effect and power consumption. Numerical results are well verified by the experiments of mixing time and mixing power. It is found that the punched impeller can get a better mixing effect and lower power consumption compared with traditional agitator blade. The punched impeller can intensify the eddy diffusion and reduce blade projection plane. The reduction of power consumption is more obvious as the speed increases. The changes of mixing power and mixing time depending on the hole diameter and the opening rate. The mixing power and mixing time are minimum and optimal when the opening rate is about 12% and the diameter is about 8 mm.