Numerical Research On The Optimal Torsion Angle And Installation Angle Of Rotor Blades Of Pulverized-coal Classifier

In recent years, rotating pulverized-coal classifier of the MPS medium-speed coalmil is widely used for mill system in power plant. As an important device of mill system,the export pulverized coal fineness, integrated separation efficiency and internalventilation resistance are crucial to the safety, economy and stability of thermal powerplant. The solid-gas two phase flow numerical simulation method is a very effectivetechnology in analyzing complex fluid flow. A better understanding of the operationcharacteristic can be obtained when applying the technology in studying internalpulverized coal particles trajectory separation characteristic and the ventilation resistance,which is also very important for the structure optimization.For the past few years, some scholars have made some optimization and renovationto the pulverized-coal classifier of the MPS medium-speed coal mill. From anotherperspective, this article introduces the modification of the pulverized-coal classifier rotorblade and the twisting and bending design on the variable cross-section of the movingblades. This kind of design can lower the friction loss when the air flows in and decreasethe eddy current loss when the air flows out, thus, the power consumption of mill systemwill be reduced. The twisting and bending design can produce stronger blasting action inthe process of work, meanwhile, the improvement of the leaf shape structure can magnifythe collision probability between pulverized coal particle and rotating blades.Simultaneously, the working properties of the classifier will be enhanced. Differences ofthe twist-bend blades angel and the installation angel have different effects on theworking properties of the classifier.Considering of those difference, the article carries the numerical studies by usingthe Fluent software on two units:350MW and600MW in a power plant. With differenttwist-bend blade structures are used on the pulverized-coal classifier rotor, the regularitycognition of the pulverized coal fineness，the integrated separation efficiency，the internalair resistance and some other performance indexes are changing. Then, the optimaltwist-bend angel and installation angel of the rotor blades in each of the two units are got.By comparing the optimal rotor blades structure in classifiers of the two units, the maindifference index is the installation angel: the former is10°, the latter is15°.The optimal bend angel and twist angel are the same,15°and25°respectively. The change of theoptimal rotor blades provide theoretical guidance for optimizing the rotor blades of otherunits.