本文關鍵詞：攪拌槽內(nèi)固體顆�；旌系臄�(shù)值模擬　出處：《北京化工大學》2016年碩士論文　論文類型：學位論文

  更多相關文章： 顆粒混合 DEM 功率 混合度

【摘要】：顆粒作為生產(chǎn)原料或產(chǎn)品在化工、醫(yī)藥、冶金、礦石和材料等過程工業(yè)領域有著廣泛的應用。顆粒的混合通常是相關生產(chǎn)工藝中的重要單元操作。在顆粒的混合過程中,混合效果以及過程中的動力消耗則是關注的焦點。離散元(Discrete Element Method, DEM)作為一種可用于分析顆粒受力的數(shù)值方法,以顆粒的相互接觸為起點,通過契合顆粒接觸和碰撞等行為時的受力模型,計算顆粒隨時間變化的運動信息,成為研究顆粒在過程工業(yè)中的有效方法。本研究在直徑為0.284 m的標準橢圓封底的攪拌槽內(nèi),對球形顆粒的混合行為進行了數(shù)值模擬。通過使用Hertz-Mindlin and Linear Spring模型對固體顆粒間作用力進行計算,計算得到粒徑范圍為4-5mm的顆粒和粒徑范圍為2-3mm的顆粒在不同的槳型組合、轉速和加料量下的顆�；旌线^程。在數(shù)值模擬的同時,采用相同物性及尺度分布的玻璃珠顆粒作為實驗原料,通過改變攪拌槳組合方式、物料裝填系數(shù)、轉速等條件探究固體顆粒攪拌功率的變化規(guī)律和混合度的變化規(guī)律。攪拌轉速在30rpm和60rpm時,各槳型組合的功率的模擬結果和實驗計算結果基本吻合。在對不同槳型的混合度進行模擬時,雙螺帶和內(nèi)外單螺帶的宏觀混合作用較強。同時,針對同一顆粒物系和同一槳型,從初始狀態(tài)到混合穩(wěn)定狀態(tài)的轉數(shù)一定。即10%的2-3mm顆粒含量下四種槳型從開始到穩(wěn)態(tài)經(jīng)歷的槳葉轉數(shù)分別是100轉(雙螺帶),170轉(Paravisc),60轉(內(nèi)外單螺帶),190轉(Paravisc加三葉后掠)。改變轉速對雙螺帶的宏觀混合影響較大,對其他三種槳型影響較小。在不同轉速下,2-3mm顆粒在徑向上的位置變化不大,其在r/R=0.25,0.45,0.65,0.85處的顆粒集合徑向位置維持在0-20mm,軸向位置主要與槳葉對顆粒的帶動作用有關,但大部分操作條件下,上述四個位置處的顆粒集合的軸向位置也會趨于200-250mm區(qū)域。模擬結果顯示各個槳型在混合的各個階段時的混合程度與實驗結果基本吻合。同時,數(shù)值模擬不僅提供了功率、扭矩和混合度等宏觀參數(shù)的變化規(guī)律,也給出了觀察顆�；旌蟽�(nèi)部結構變化和其他實驗所不能測定的數(shù)據(jù)信息。
[Abstract]:Particles are used as raw materials or products in chemical, pharmaceutical, and metallurgical industries. Ore and materials are widely used in process industry. Particle mixing is usually an important unit operation in related production process. The mixing effect and the power consumption in the process are the focus of attention. Discrete Element Method. Demm) as a numerical method which can be used to analyze the force of particles, based on the interaction of particles, the force model is adopted to fit the behavior of particle contact and collision. Calculating the movement information of particles with time is an effective method to study particles in the process industry. This study is in the stirring tank with a standard elliptical bottom of 0.284 m in diameter. The mixing behavior of spherical particles was numerically simulated and the interaction forces between solid particles were calculated by using Hertz-Mindlin and Linear Spring model. The mixing process of particles with 4-5mm particle size and 2-3mm particle size under different propeller combinations, rotational speed and feed volume was obtained. The numerical simulation was also carried out at the same time. The glass beads with the same physical properties and size distribution were used as experimental materials, and the material loading coefficient was changed by changing the impeller combination mode. The changing law of mixing power and mixing degree of solid particles was studied under the conditions of rotating speed and so on. The stirring speed was 30rpm and 60rpm. The simulation results of the power of each propeller combination are in good agreement with the experimental results. When the mixing degree of different propellers is simulated, the macroscopic mixing between the double screw belt and the inner and outer single screw belt is stronger. At the same time. For the same particle system and the same paddle type. The rotation number from the initial state to the mixed stable state is constant, that is, the rotor rotation number of the four propeller types from the beginning to the steady state under the 2-3mm particle content of 10% is 100rpm (double screw belt) respectively. (170) Paravis cor 60 rpm (internal and external single snail belt 190 rpm + trefoil swept back). The change of rotational speed has a great influence on the macroscopic mixing of double snails. It has little effect on the other three types of propeller. The position of 2-3mm particles in the radial direction has little change at different rotational speeds, and it is 0.65 at r / r ~ (0.25) ~ 0.45 ~ 0. 5%. The radial position of the particle set at 0.85 is maintained at 0-20 mm, and the axial position is mainly related to the impelling effect of the blade on the particle, but under most operating conditions. The axial position of the particle set at the above four positions will also tend to be 200-250 mm. The simulation results show that the mixing degree of each propeller at each stage of mixing is basically consistent with the experimental results. At the same time. The numerical simulation not only provides the variation law of macroscopic parameters such as power torque and mixing degree but also gives the data information which can not be measured by observing the internal structure change of particle mixing and other experiments.
【學位授予單位】：北京化工大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TQ027.1

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