本文選題：渦流空氣分級機 + 轉(zhuǎn)籠內(nèi)外半徑�。� 參考：《北京化工大學(xué)》2015年碩士論文

【摘要】：粉體物料的分級是粉體材料生產(chǎn)過程中重要的單元操作之一,渦流空氣分級機則是該單元操作中經(jīng)常使用的一種分級設(shè)備。隨著粉體技術(shù)的發(fā)展,對粉體分級設(shè)備的要求越來越高,因此對分級機的改進研究一直在進行。分級機的內(nèi)部結(jié)構(gòu)是影響分級性能的重要因素,近年來對其結(jié)構(gòu)的優(yōu)化研究取得了顯著的成果,為分級機的結(jié)構(gòu)改進提供了理論基礎(chǔ)。本文主要從轉(zhuǎn)籠內(nèi)外半徑的尺寸以及轉(zhuǎn)籠葉片間距的大小兩方面對渦流空氣分級機的結(jié)構(gòu)進行改進,采用FLUENT對改進前后的渦流空氣分級機內(nèi)部流場進行了數(shù)值模擬,得到了使環(huán)形區(qū)以及轉(zhuǎn)籠葉片間流場穩(wěn)定的轉(zhuǎn)籠內(nèi)外半徑尺寸以及轉(zhuǎn)籠葉片間距,并對轉(zhuǎn)籠內(nèi)外半徑改進前后的渦流空氣分級機進行了物料實驗以驗證模擬結(jié)果。為研究轉(zhuǎn)籠葉片寬度不變時,轉(zhuǎn)籠內(nèi)外半徑對渦流空氣分級機分級性能的影響,采用FLUENT對具有不同內(nèi)外半徑轉(zhuǎn)籠的渦流空氣分級機內(nèi)部流場進行模擬,模擬結(jié)果表明：轉(zhuǎn)籠內(nèi)外半徑同時減小18 mm,環(huán)形區(qū)寬度增加18 mm時,環(huán)形區(qū)氣流切向速度增大,有利于物料的分散,切向速度在單位寬度內(nèi)的變化率由0.208 m·s-1·mm-1減小到0.149m·s-1·mm-1,說明環(huán)形區(qū)流場分布的均勻性有所提高；同時轉(zhuǎn)籠入口附近切向速度波動從2.7 m·s-1減小到O.8 m·s-1,進入轉(zhuǎn)籠的細粉產(chǎn)品的粒徑分布變窄；此時,由于轉(zhuǎn)籠葉片間距減小,使得葉片間慣性反旋渦強度明顯減弱,徑向速度分布均勻,細粉能夠迅速進入轉(zhuǎn)籠內(nèi)部實現(xiàn)分級,降低了細粉顆粒返混到粗粉的可能性,使分級精度提高。碳酸鈣物料實驗表明：轉(zhuǎn)籠內(nèi)外半徑同時減小18mm時,分級精度提高3.3%-25.4%,同時細粉產(chǎn)率增加27.8%-76.2%,物料實驗結(jié)果與模擬結(jié)果相符。轉(zhuǎn)籠葉片數(shù)的改變使葉片間距發(fā)生變化,在轉(zhuǎn)籠內(nèi)外半徑一定的情況下,存在一個使葉片間流場最穩(wěn)定的轉(zhuǎn)籠葉片間距。對不同轉(zhuǎn)籠在不同葉片間距下的流場進行研究表明：當(dāng)葉片間距與葉片寬度之比為0.23時,葉片通道內(nèi)的徑向速度分布最均勻；對顆粒在不同間距的葉片通道中的運動軌跡進行模擬后發(fā)現(xiàn),當(dāng)葉片間距與葉片寬度之比為0.23時,顆粒在葉片通道內(nèi)的運動軌跡簡單,且不易與葉片壁面發(fā)生碰撞,細顆粒能夠快速地進入轉(zhuǎn)籠內(nèi)部實現(xiàn)分級,避免了細粉顆粒的返混,能夠明顯提高分級精度。
[Abstract]:The classification of powder materials is one of the important unit operations in the production of powder materials, and the eddy current air classifier is a kind of classifying equipment which is often used in the unit operation. With the development of powder technology, the requirement of powder classifier is more and more high, so the improvement of classifier has been carried out all the time. The internal structure of the classifier is an important factor affecting the performance of the classifier. In recent years, remarkable achievements have been made in the optimization of the classifier's structure, which provides a theoretical basis for the structural improvement of the classifier. In this paper, the structure of swirl air classifier is improved from the dimensions of the inner and outer radius of the cage and the distance between the blades of the rotary cage. The internal flow field of the swirl air classifier before and after the improvement is numerically simulated by FLUENT. The size of the inner and outer radius of the rotating cage and the distance between the rotor blades are obtained to stabilize the flow field in the annular region and between the blades of the cage. The material experiments of the swirl air classifier before and after the improvement of the inner and outer radius of the cage are carried out to verify the simulation results. In order to study the influence of the inner and outer radius of the cage on the classification performance of the swirl air classifier, the flow field of the swirl air classifier with different inner and outer radii was simulated by FLUENT. The simulation results show that when the inner and outer radius of the rotating cage decreases 18 mm and the width of the annular region increases 18 mm, the tangential velocity increases in the annular region, which is beneficial to the dispersion of materials. The change rate of tangential velocity in the unit width is reduced from 0.208 m s -1 mm-1 to 0 149 m s -1 m m -1, which indicates that the uniformity of the flow field distribution in the annular region has been improved. At the same time, the tangential velocity fluctuation near the inlet of the cage decreases from 2.7 m s ~ (-1) to O. 8 m ~ (-1), and the particle size distribution of the fine powder product entering the cage becomes narrower. At this time, due to the decrease of the rotor blade spacing, the strength of the inertia counter-vortex between the blades is obviously weakened. The radial velocity distribution is uniform, the fine powder can quickly enter the inner of the cage to realize the classification, which reduces the possibility of the fine powder particles mixing back to the coarse powder, and improves the classification accuracy. The experiment of calcium carbonate material shows that when the inner and outer radius of the cage is reduced simultaneously, the classification accuracy is increased by 3.3- 25.4and the yield of fine powder is increased by 27.8-76.2.The results of the material experiment are in agreement with the simulation results. The change of the number of rotor blades makes the blade spacing change. In the case of a certain radius inside and outside of the cage there exists a rotor blade spacing which makes the flow field between the blades the most stable. The flow field of different cages with different blade spacing is studied. The results show that when the ratio of blade spacing to blade width is 0.23, the radial velocity distribution in the blade passage is the most uniform. After simulating the movement trajectory of particles in the blade passage with different spacing, it is found that when the ratio of blade spacing to blade width is 0.23, the particle movement path in the blade passage is simple, and it is not easy to collide with the blade wall. The fine particles can quickly enter the inner of the cage to realize the classification, avoid the backmixing of the fine particles, and can obviously improve the classification accuracy.
【學(xué)位授予單位】：北京化工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TQ051.8

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