【作者】 聂文平；

【导师】 黎国华；

【作者基本信息】 武汉理工大学 ， 机械电子工程， 2004， 硕士

【摘要】 涡轮式气流分级机是精密分级设备中非常重要的类型之一。涡轮式气流分级机内腔流场是超细粉体同空气的混合两相流，其运动情况相当复杂。然而，流场是否稳定，是否有利于粗细粒子的有效分散等等问题是决定超细分级设备设计成败的关键；掌握分级机流场的流动特性以及粒子的运动规律对于设计合理的分级腔结构，调整最佳的系统操作参数等具有十分重大的意义。 首先，本文应用流体力学及数值计算方法，借用成熟的商用CFD分析软件PHOENICS，对一种新型的涡轮式气流分级机，即FW—φ150型卧式涡轮分级机的内腔两相流流场运用气-固两相流的双流体理论模型和颗粒随机轨道模型进行数值模拟。数值模拟结果表明，(1)在涡轮达到工作转速时，在分级区域形成了一个与涡轮旋转方向相反的局部回流涡，它使得分离出来的细粒重又被带回分级轮外边缘，从而严重影响分级机的分级效率；(2)粉尘粒子在涡轮低速运动情况下，基本上能跟随气体运动，但随着转速加大，两相之间出现了明显的速度滑移现象；(3)分级机工作时的风量也是一个比较重要的操作参数，它可以直接影响到分级机内腔流场的稳定性，风量越大，流场越稳定；(4)同直叶片形状相比较，带后弯导板的叶片，有利于改善流场的稳定性，流场容易形成整体流，对提高分级效率和分级精度都非常有利；(5)粒子轨迹线在涡轮转速较高时十分复杂，有的出现了反复的弹跳现象，大颗粒不能通过分级区域而从进口返流了，只有细小的颗粒才从出口处流出；(6)涡轮转速加大时，粒子的径向、轴向和切向速率出现了明显的类似于正弦波的脉动现象，颗粒越小，脉动程度越为剧烈。 其次，通过对叶片流道内的流体运动进行理论分析得知，旋转机械的轴向环流效应是分级流场局部涡流形成的主要动因，但改变叶片形状，特别是采用后弯形状叶片，在一定程度上能使流场稳定性得到改善。 最后，将部分数值模拟结果与前人的理论计算结果及实验数据进行比较，他们在一定程度上是吻合的。这些模拟结果，从不同侧面描绘出了粉体与空气在涡轮内腔的真实流动状态，为在今后的设计工作中优化分级涡轮的结构形状，合理调整各种操作参数，提供了一定的理论依据。更多还原

【Abstract】 Turbo air classifier is a important style of accurate classifying facilities. The flow field of inner cavity in turbo air classifier is a gas-solid two phase flow of air and ultrafine particles, and the state of its movement is quite complicated. However, whether the flow field is steady and is in favor of the effectual disperse between the coarse and fine powder and so on, are some problems which can determine whether the design for the ultrafine classifying equipments is successful or not; and besides, in order to design reasonable classifying chamber structure and adjust optimal operation parameters, a good grip on the flowing characteristics of classifying flow field and motion rules of the particles is very essential and significant.First, in this paper, as for a new type of turbo air classifier, FW- 4> 150 horizontal turbine superfine classifier, the theories of hydrodynamics and numerical calculation is applied to numerically simulate the gas-solid two phase flow field of the inner cavity between two blades in classifier by virtue of a mature commercial CFD code PHOENICS .In the course of the simulation , the theoretical model of two fluid and the stochastic trajectory model of particles in two-phase flows are used respectively. The calculation results shows that , (1) when the rotor rotates at the working speed, a local regurgitant whirlpool that is rightabout to the rotor’s rotating direction appears in the classifying region, which makes the separated granules come back to the outside of the classification district and influences the classification efficiency of the turbine classifier;(2) in the condition of a low rotating speed of turbo rotor, ultrafine particles can follow the gas phase by and large, but when the rotating speed increases, a phenomenon of velocity slippage between two phases appears evidently;(3) A operating parameter, air flow rate is so important that can directly influence the stability of flow field in classifying chamber, the bigger the air flowrate is , the steadier the flow field is;(4) Compared with straight blades, the new shape of blades with backward crooked elbow are helpful to improve the stability of flow field and form whole stream easily, also beneficial to advance the classification accuracy and classification efficiency;(5) The motion trace of particles are very complicated when the turbo rotor rotates at a high speed, the constant bounce of the particles appear between the blades and the coarse particles are even bounce back from the inlet, only the finer can pass through the classification area from the oulet;(6) Along with the increase of the rotor’s rotating speed, radiah axial and tangential velocity all begain to fluctuate repetitively like sine-wave, the smaller the particles are, the more violently they fluctuates.Second, a theoretic analysis of the flow movement in the flow chunnel between two blades is made, and the result reveals that the axial circumfluence phenomenon often exsists in revolving machines is the main reason that result in the local circumfluence votex in the classifying flow field, however, when the shape of blade is designed in reason, especially the backward crooked blades are used, which can improve the stability of flow field to some extend.Finally, some simulation results are compared with the theoretic calculation and the experimental data, and they shows a good consistency. These simulation results described the actual flowing state of the air and the ultrafine particles in classifying chamber from different sides, which can provide some theoretic evidence for optimizing the structure of the turbo rotor and adjusting correlative operation parameters appropriately in the future.更多还原