本文選題：同心雙軸攪拌器　切入點：粘性體系　出處：《浙江大學》2017年碩士論文

【摘要】：同心雙軸攪拌器是一種新型寬適應性攪拌器,具有靈活可調和高效低耗的優(yōu)點,在工業(yè)界得到了廣泛的認可。目前國內外對同心雙軸攪拌器的研究較少,且主要集中在對單相體系的研究上。本文對同心雙軸攪拌器在固液粘性體系中的臨界離底懸浮轉速、功耗特性進行了實驗研究。首先提出了一種新的基于壓力測量的臨界離底懸浮狀態(tài)判定方法,實驗證明該方法能較好的應用于固液、氣液固體系臨界離底懸浮狀態(tài)的判定�；谛绿岢龅呐R界離底懸浮狀態(tài)判定方法,實驗對比了三組同心雙軸攪拌器(錨式外槳+六直葉圓盤渦輪/上揚式六斜葉開式渦輪/上揚式推進槳)以及三種單軸槳(六直葉圓盤渦輪/上揚式六斜葉開式渦輪/上揚式推進槳;D=0.35T/D=0.53T)在粘性固液體系中的臨界離底懸浮轉速和功耗。結果表明,同心雙軸攪拌器較單軸攪拌器具有更高的功率效率,特別是當外槳轉速較大時,同心雙軸攪拌器的優(yōu)勢更加突出,而三種槳型組合中,錨式外槳加推進式槳組合的功耗效率最高。實驗研究還對比了同心雙軸攪拌器在不同的轉動模式(內外槳同向轉動、外槳靜止不動、內外槳反向轉動)條件下的固相懸浮能力,結果表明固相懸浮性能同向模式好于單軸模式好于反向模式。此外,考慮了液相粘度、固相粒徑、固含率、固液相密度差等因柰對臨界離底懸浮轉速和功耗的影響,提出了一個適用于同心雙軸攪拌器的臨界離底懸浮轉速預測公式。為了更加直觀地描述同心雙軸攪拌器固相懸浮特性,采用CFD方法研究了同心雙軸攪拌器的固相懸浮特性。為了建立合理的數(shù)學模型,首先將常用的Gidaspow曳力模型和修正Brucato曳力模型的模擬結果與前人的實驗結果進行了對比,發(fā)現(xiàn)修正的Brucato曳力模型對固液兩相攪拌體系流動參數(shù)的預測更加準確。監(jiān)測距釜底1mm平面上平均固含率隨轉速的變化發(fā)現(xiàn),平均固含率隨轉速增加先緩慢降低,后急劇下降,最后趨于平穩(wěn)。根據距釜底1mm平面上平均固含率-轉速曲線對臨界離底懸浮轉速進行了模擬預測,和實驗結果吻合良好。模擬還直觀地展示了三種槳型組合條件下的固相流型,展示了不同轉動模式和外槳轉速條件下的固含率分布和流型分布,以及研究了液相粘度、固含率對固相分布的影響。
[Abstract]:Concentric biaxial stirrer is a new type of wide adaptive agitator, which has the advantages of flexible, adjustable, high efficiency and low consumption, and has been widely recognized in industry. At present, there are few researches on concentric biaxial stirrer at home and abroad. In this paper, the critical off-bottom suspension speed of concentric biaxial agitator in solid-liquid viscous system is studied. Firstly, a new critical off-bottom suspension state determination method based on pressure measurement is proposed, and the experimental results show that this method can be applied to solid-liquid system. Determination of critical off-bottom suspension state of gas-liquid solid system. Three sets of concentric biaxial agitators (anchor outer propeller six-straight disk turbine / upturned six-blade open turbine / hoist propeller) and three kinds of single-axis propellers (six-straight blade disk turbine / hoisting hexagonal blade open impeller) were experimentally compared with that of three groups of concentric biaxial agitators. The critical off-bottom suspension speed and power consumption of turbine / propeller D _ (0.35) T / D _ (0.53T) in viscous solid-liquid system are obtained. The concentric biaxial stirrer has higher power efficiency than the single-axis agitator, especially when the rotating speed of the outer propeller is larger, the advantages of the concentric biaxial stirrer are more prominent, and among the three kinds of propeller combinations, The power efficiency of the combination of anchor propeller and propulsive propeller is the highest. The solid suspension capability of concentric biaxial stirrer under different rotating modes (internal and external propeller stationary, external propeller stationary, internal and external propeller reverse rotation) is also compared. The results show that the performance of solid phase suspension is better in the same direction mode than in the reverse mode. In addition, the effects of liquid viscosity, solid particle size, solid holdup and solid liquid density difference on the critical bottom suspension speed and power consumption are considered. A prediction formula of critical off-bottom suspension speed for concentric biaxial stirrer is presented. In order to describe the solid suspension characteristics of concentric biaxial agitator more intuitively, The solid suspension characteristics of a concentric biaxial stirrer are studied by CFD method. In order to establish a reasonable mathematical model, the simulation results of the commonly used Gidaspow drag model and the modified Brucato drag model are compared with the previous experimental results. It is found that the modified Brucato drag model is more accurate in predicting the flow parameters of solid-liquid two-phase stirring system, and the average solid holdup of the 1mm plane from the bottom of the kettle changes with the rotational speed. It is found that the average solid holdup decreases slowly at first and then decreases sharply with the increase of the rotational speed. Finally, it tends to be stable. According to the curve of average solid holdup and rotational speed on the plane of 1mm from the bottom of the kettle, the critical off-bottom suspension speed is simulated and predicted, which is in good agreement with the experimental results. The simulation also shows the solid state flow patterns directly under three kinds of propeller combination conditions. The distribution of solid holdup and flow pattern under different rotation modes and rotational speeds of the outer propeller are shown, and the effects of liquid viscosity and solid holdup on the distribution of solid phase are also studied.
【學位授予單位】：浙江大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ051.72

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