Abstract: Velocity field in the grading zone of vertical mill classifier is the main factor affecting the classification performance. Gas-solid two-phase flow in vertical mill classifier is non-ideal fluid. By applying the theory of viscosity and velocity gradient in fluid mechanics，the reason why a big velocity gradient would make a decline on the classification precision and the classification efficiency of a classifier is analyzed. The model of vertical mill classifier with individual rotor blade structure was built，and in which variations in velocity field，including velocity direction，velocity size and velocity gradient in grading zone，are simulated numerically and analyzed through the Fluent software. A test of structural transformation on rotor blade of vertical mill classifier was made. And the test showed that the production of the vertical mill classifier with the Z-blade rotor structure was improved by 15 t/h，and the residue on sieve of 0.08mm particles reduced by 10%，compared to the one with straight blade.

Key words: vertical mill classifier, blade structure, grading zone, velocity field, velocity gradient

摘要： 立磨选粉机分级区速度场是影响其分级性能的主要因素之一，其机内气固两相流为非理想流体。本文应用流体力学流体黏滞性与速度梯度原理，分析了速度梯度过大造成选粉机选粉精度和选粉效率下降的机理。通过构建不同叶片结构转笼的立磨选粉机模型，采用Fluent软件模拟分析了立磨选粉机不同叶片结构转笼的分级区速度场中速度流向、速度大小与速度梯度的变化规律。进行了立磨选粉机转笼叶片结构改造试验，试验表明：改造后的Z形叶片结构转笼的立磨选粉机产量在直叶片转笼结构的基础上提高了15 t/h，且0.08 mm颗粒的筛余降低了10%。

关键词: 立磨选粉机, 叶片结构, 分级区, 速度场, 速度梯度