本文選題：高速分散器 + VOF模型�。� 參考：《北京化工大學》2015年碩士論文

【摘要】：高速分散器作為一種氣液傳質(zhì)設(shè)備,通過轉(zhuǎn)子的高速旋轉(zhuǎn),使液體在強大的離心力、剪切力作用下被分散成液滴、液絲,大大增加氣液相接觸面積,且其轉(zhuǎn)子結(jié)構(gòu)簡單,便于清洗維護,因而具有廣闊的應(yīng)用前景。本文采用Ansys Fluent軟件對高速分散器內(nèi)低粘及高粘體系的流體力學特性進行數(shù)值模擬研究,對后續(xù)傳質(zhì)研究及分散器結(jié)構(gòu)設(shè)計提供理論及數(shù)據(jù)支持。本文所研究的高速分散器的轉(zhuǎn)子(內(nèi)徑211 mm,外徑219 mm)沿周向均勻分布180個格柵。分別采用流體體積分數(shù)模型(Volume of Fluid, VOF)及歐拉多相流模型對低粘體系(空氣-水)(轉(zhuǎn)速300～1000 rpm,液相進料量1.164～3.443 m3.h-1,距離轉(zhuǎn)子外緣徑向距離0-208mm)及高粘體系(空氣-糖漿)(轉(zhuǎn)速300～1500 rpm,液相進料量0.381 m3·h-1,徑向位置0～300 mm)的流體力學特性進行二維數(shù)值模擬,重點研究空腔區(qū)域液相形態(tài)、液滴直徑及直徑分布、液相速度、液相平均停留時間隨操作條件的變化趨勢及原因。結(jié)果表明,高轉(zhuǎn)速下液滴直徑變小但分布趨向于不均勻,且平均停留時間變短,即轉(zhuǎn)速對氣液相傳質(zhì)的影響較為復雜；液相進料量變大時,液滴直徑略微變大且分布變得不均勻,液相平均停留時間減小,在一定程度上減弱傳質(zhì)效果；距離轉(zhuǎn)子較遠時,液滴由于飛行過程中的碰撞聚并導致直徑增大,在設(shè)計分散器直徑時應(yīng)考慮這一影響。同時,粘度是影響空腔區(qū)域液相形態(tài)及流場特性的關(guān)鍵因素,低粘物料被分散器轉(zhuǎn)子分散成大量液滴而高粘物料則形成連續(xù)的液絲。本文還針對低粘體系速度場進行三維數(shù)值模擬,得到液相軸向速度隨轉(zhuǎn)速及液相進料量的增加而增大,隨徑向位置遠離轉(zhuǎn)子而減��；軸向位移隨轉(zhuǎn)速及液相進料量的增加而增大。將二維及三維模擬結(jié)果同實驗結(jié)果對比,發(fā)現(xiàn)兩種方法的相對誤差均在15%以下。三維模擬的計算精度總體優(yōu)于二維模擬,但其模型網(wǎng)格數(shù)比二維模型高1-2個數(shù)量級。應(yīng)綜合考慮計算精度及計算時間選擇合適的模擬方法。
[Abstract]:As a kind of gas-liquid mass transfer equipment, the high-speed disperser makes the liquid dispersed into droplets and wires under the strong centrifugal force and shear force through the high-speed rotation of the rotor, which greatly increases the gas-liquid contact area, and its rotor structure is simple. It is convenient for cleaning and maintenance, so it has broad application prospect. In this paper, Ansys Fluent software is used to simulate the hydrodynamic characteristics of low viscosity and high viscosity systems in a high speed dispersion, which provides theoretical and data support for the subsequent mass transfer study and the structure design of the dispersion. In this paper, the rotor (211mm inside diameter and 219mm outer diameter) of the high speed disperser is uniformly distributed along the circumference of 180 gratings. The fluid volume of Fluid, VOF) and Euler multiphase flow models were used for the study of low viscosity systems (air-water (rotational speed 300 脳 1000rpm), liquid phase feed rate 1.164 ~ 3.443 m ~ (3.h-1), radial distance 0-208 mm to the outer edge of rotor) and high viscosity (air-syrup) system. The two dimensional numerical simulation is carried out on the hydrodynamic characteristics of the velocity 300,500rpm, the liquid feed rate of 0.381 m3 h-1, and the radial position of 300mm. The variation trend and reason of liquid morphology, droplet diameter and diameter distribution, liquid velocity and average residence time of liquid phase with operating conditions were studied. The results show that the droplet diameter becomes smaller but the distribution tends to be uneven at high rotational speed, and the average residence time becomes shorter. The droplet diameter is slightly larger and the distribution becomes uneven, the average residence time of liquid phase decreases, the mass transfer effect is weakened to a certain extent, and when the droplet is far from the rotor, the droplet diameter increases due to the collision and accumulation during the flight. This effect should be taken into account in the design of the diameter of the disperser. At the same time, viscosity is the key factor affecting the liquid morphology and flow field characteristics in the cavity region. The low viscosity material is dispersed into a large number of droplets by the rotor of the disperser, while the high viscosity material forms a continuous liquid wire. In this paper, the 3-D numerical simulation of the velocity field of low viscosity system shows that the axial velocity of liquid increases with the increase of rotational speed and the amount of liquid feed, and decreases with the radial position away from the rotor. The axial displacement increases with the increase of rotational speed and liquid phase feed. Compared with the experimental results, the relative errors of the two methods are below 15%. The accuracy of 3D simulation is better than that of 2D simulation, but the grid number of 3D model is 1-2 orders of magnitude higher than that of 2D model. The calculation accuracy and calculation time should be considered synthetically and the appropriate simulation method should be chosen.
【學位授予單位】：北京化工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ051.1

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本文編號：1934276