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  本文關鍵詞： 輕浮顆粒 粘稠體系 推進式軸流槳 臨界下拉轉速與功率 計算流體力學(CFD)　出處：《浙江大學》2015年碩士論文　論文類型：學位論文

【摘要】：攪拌操作在石油、化工、食品、醫(yī)藥、肥料、染料、冶金、造紙以及污水處理等過程工業(yè)中應用廣泛,在勻化、乳化、聚合和發(fā)酵等場合中發(fā)揮著重要作用。輕浮顆粒固-液攪拌混合不同于沉積顆粒的混合,它是將漂浮在液面的顆粒下拉并分散至攪拌釜中。目前有關固-液兩相流攪拌的研究大都針對沉積顆粒懸浮展開,而對于輕浮顆粒下拉分散的研究相對較少,輕浮顆粒固-液混合攪拌釜設計等往往缺少理論指導,而實踐證明簡單地照搬沉積顆粒固-液攪拌混合的設計經驗是不合適的。本文采用實驗研究和數(shù)值模擬的方法研究攪拌釜結構和物性參數(shù)對輕浮顆粒下拉分散的影響,得到了顆粒下拉分散的臨界下拉轉速、功率、流場和濃度場等相關參數(shù),為工業(yè)的實際應用打下了基礎。本文首先在體系液相粘度為75.3mPa-s的攪拌釜中研究六斜葉開啟渦輪槳、六直葉圓盤渦輪槳和推進式軸流槳在不同的浸入深度、槳徑比和擋板布置方式下輕浮顆粒的下拉分散情況。實驗結果表明：上推式攪拌槳的臨界下拉轉速和功率要大于下壓式攪拌槳。最適合于輕浮顆粒下拉分散的攪拌釜結構為：攪拌槳采用下壓式軸流槳,浸入深度為S=0.25T,采用一個偏心布置的全深度擋板�；趦�(yōu)選的攪拌釜結構,研究了液相粘度、固含量和顆粒大小等條件對輕浮顆粒下拉分散影響。研究表明：隨著體系液相粘度的增大,臨界下拉轉速和功率不斷增大；隨著固含量和顆粒的增大,臨界下拉轉速和功率也隨之增大。本文最后用數(shù)值模擬的方法研究了三種攪拌槳的流場、濃度場和湍流強度分布。研究表明：當曳力模型采用Gidaspow模型時,模擬結果與實驗結果吻合良好,Gidaspow曳力模型適合于輕浮顆粒固-液兩相流的模擬；三種攪拌槳作用下液面湍流強度最大區(qū)域位置基本相同,位于流體運動方向距擋板位置約90°靠近攪拌軸處,該位置與表面偏心渦的形成位置相近；最優(yōu)的下壓式軸流槳的槳徑比為D/T=0.5；固-液混合非穩(wěn)態(tài)模擬結果表明不同監(jiān)測點位置的混合時間不同,其時間的長短與監(jiān)測點位置的流體速度有關。
[Abstract]:Mixing operations are widely used in petroleum, chemical, food, medicine, fertilizer, dyes, metallurgy, papermaking and sewage treatment, etc. They are widely used in levelling, emulsifying, and so on. It plays an important role in polymerization and fermentation. Solid liquid mixing of frivolous particles is different from the mixing of deposited particles. At present, most of the researches on solid-liquid two-phase flow agitation are focused on sediment particle suspension, but there is relatively little research on the dispersion of frigid particles. The design of frivolous particle solid-liquid mixing agitator often lacks theoretical guidance. It has been proved that it is not appropriate to simply copy the design experience of solid-liquid mixing of sedimentary particles. In this paper, the effects of the structure and physical properties of agitator on the pull-down dispersion of frivolous particles are studied by means of experimental study and numerical simulation. The critical pull-down speed, power, flow field and concentration field of particle pull-down and dispersion were obtained, which laid the foundation for industrial application. In this paper, the six oblique blade turbomachinery was first studied in a agitator with liquid viscosity of 75.3 mPa-s. The six straight blade disk turbine propeller and the propelling axial flow propeller are immersed at different depths, The experimental results show that the critical pull-down speed and power of the upward impeller are higher than those of the down-pressure impeller, which is the most suitable for the pull-down dispersion of the frivolous particles. The structure of the mixing kettle is as follows: the agitator adopts the downward pressure axial flow propeller, The immersion depth is 0.25T, and an eccentrically arranged full-depth baffle is used. The liquid viscosity is studied based on the structure of the optimized agitator. The results show that the critical pull-down speed and power increase with the increase of liquid viscosity, and increase with the increase of solid content and particle size. The critical pull-down speed and power also increase. Finally, the flow field, concentration field and turbulence intensity distribution of three kinds of impellers are studied by numerical simulation. The results show that when the drag model is Gidaspow model, The simulation results are in good agreement with the experimental results. The Gidaspow drag model is suitable for the simulation of frigid particle solid-liquid two-phase flow, and the maximum turbulent intensity of liquid surface under the action of three kinds of impellers is basically the same. The direction of fluid motion is about 90 擄from the baffle near the stirring axis, which is close to the formation position of the surface eccentricity vortex. The optimal downpressure axial propeller is D / T 0.5. The unsteady simulation results of solid-liquid mixing show that the mixing time of different monitoring points is different, and the length of the time is related to the fluid velocity at the monitoring point.
【學位授予單位】：浙江大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ027

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本文編號：1516640