【摘要】：攪拌設備因具有操作靈活、混合效果好、相接觸面積大和適用性強的優(yōu)點而廣泛用在機械、化工等過程工業(yè)中,是應用最廣泛的化工單元操作之一。其中,攪拌槽內部流場和固液懸浮特性的研究,對工業(yè)生產有重要意義,因此是國內外學者研究的熱點內容之一。近幾年來,攪拌反應器的規(guī)模逐漸變大,相與相之間混合不均勻的問題也越來越明顯,并且當前機械過程逐漸轉向“綠色”、節(jié)能方向,越來越看重產品回收率和產品質量,因此合理設計和選擇攪拌設備就顯得特別重要。但如今對攪拌設備的選擇和設計仍然是主要依賴于小規(guī)模實驗結果以及半理論和半經驗的方法,由于技術和條件的限制在設計中并不能清晰的了解攪拌槽內部流場的詳細分布情況,而且對攪拌反應器放大規(guī)律缺乏較深入的認識,實驗模擬周期長、偏差和花費大。新的交叉學科計算流體力學技術為解決上述問題提供了新思路和新方法,其技術優(yōu)勢使得攪拌槽內部流場及固液懸浮特性的數值模擬成為攪拌領域的研究熱點之一,但是攪拌槽內部流場及固液懸浮特性的數值模擬還沒有形成較為完善的理論。本文以計算流體力學技術為主要研究手段,采用多重參考系法和標準κ—ε湍流模型對攪拌槽內部流場及固液懸浮特性進行了數值模擬,研究分析了攪拌轉速、槳離底間隙、固體顆粒濃度等因素對流場分布、固體顆粒濃度分布、臨界懸浮轉速和功率消耗的影響。 研究結果表明,槳葉離底間隙對攪拌槽內流場及固液懸浮狀態(tài)影響很大,低離底間隙有利于槽內固體顆粒的懸浮,但是當離底間隙過低時,功率消耗比較大,且槳葉離底間隙越低越容易出現清液層；增加攪拌轉速能夠改善攪拌效果,但是考慮到攪拌功率、耐久度等因素的影響,并不是攪拌轉速越大越好,需要綜合考慮來確定合適的攪拌轉速；槳離底間隙、固體顆粒直徑和固體體積濃度對攪拌功率均有影響,在相同條件下,功率消耗隨槳離底間隙的不同而不同,在C=T／4、T／5和T／6三種工況下,C=T／4時功率消耗最��；在相同條件下,功率消耗隨固體顆粒直徑的增大而增加；在同一攪拌轉速下,功率消耗隨固體體積濃度的減小而增加。
[Abstract]:Because of its advantages of flexible operation, good mixing effect, large contact area and strong applicability, mixing equipment is widely used in mechanical, chemical and other process industries, and is one of the most widely used chemical unit operations. Among them, the study of flow field and solid-liquid suspension characteristics in stirred tank is of great significance to industrial production, so it is one of the hot topics of domestic and foreign scholars. In recent years, the scale of stirred reactor has gradually become larger and the problem of uneven mixing between phases has become more and more obvious, and the current mechanical process is gradually turning to "green", energy-saving direction, and more emphasis on product recovery and product quality. Therefore, reasonable design and selection of mixing equipment is particularly important. But today, the selection and design of mixing equipment is still mainly dependent on small-scale experimental results and semi-theoretical and semi-empirical methods. Due to the limitation of technology and conditions, the detailed distribution of the flow field in the stirred tank can not be clearly understood in the design, and the detailed distribution of the flow field in the stirred tank is not well understood, and the experimental simulation period is long, the deviation and the cost are large. The new cross-disciplinary computational fluid dynamics (CFD) technology provides a new way of thinking and a new method to solve the above problems. Its technical advantages make the numerical simulation of the flow field and solid-liquid suspension characteristics in the stirred tank become one of the hot spots in the agitation field. However, the numerical simulation of the flow field and solid-liquid suspension characteristics in the stirred tank has not yet formed a more perfect theory. Based on computational fluid dynamics (CFD) technique, the flow field and solid liquid suspension characteristics in stirred tank are numerically simulated by means of multiple reference system method and standard 魏-蔚 turbulence model. The stirring speed and the bottom clearance of the impeller are studied and analyzed. The influence of factors such as solid particle concentration on flow field distribution, concentration distribution of solid particles, critical suspension speed and power consumption. The results show that the clearance of blade bottom has a great influence on the flow field and the solid liquid suspension state in the stirred tank. The low bottom gap is favorable to the suspension of solid particles in the tank, but when the gap is too low, the power consumption is relatively large. The lower the clearance from the bottom of the blade is, the easier it is to appear the liquid-clearing layer. Increasing the stirring speed can improve the stirring effect, but considering the influence of the stirring power and durability, it is not better to increase the stirring speed, so it is necessary to determine the appropriate stirring speed synthetically. The impeller bottom clearance, solid particle diameter and solid volume concentration have effects on the stirring power. Under the same conditions, the power consumption varies with the bottom clearance of the propeller. Under the three conditions of C / T / 4 / T / 5 and T / 6, The power consumption is minimum at C=T/ 4; Under the same conditions, the power consumption increases with the increase of solid particle diameter, and increases with the decrease of solid volume concentration at the same stirring speed.
【學位授予單位】：安徽理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ051.72

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