液体连续相撞击流强化传递过程的波动特性
发布时间：2018-08-22 13:26
【摘要】：液体连续相撞击流反应器(LISR)是众多新型化工反应器中的一种新类型,其优良的混合性能来源于自身能够显著强化混合分散过程,而反应器具有特殊的流体流动结构,其身结构与操作特性的微小变化又影响整个流场中流体的混合效率、分散范围和强度等。从反应器自身反应效率来看,传质传热及相关反应过程都是在反应器中进行,而且反应器中流场和反应过程存在复杂多变性,需要通过对反应器内波动特性特研究与测定来解决。所以研究撞击流反应器在不同结构方式和操作参数下流体的波动特性对阐述其混合过程机理以及优化结构具有必要性和参考性。本文通过几何模型软件Gambit建立探究所需的各种LISR基本几何物理模型,再由常用计算流体力学所用数值模拟软件即Fluent对LISR内整个流场进行数值模拟,探讨了在不同结构方式如:不同桨叶类型、不同筒径比、不同撞击距离下与不同操作参数如:物料组分含量、转速条件下速度场、压力场在空间域和时间域上的波动分布规律,得到各种工况下撞击区域和循环区域压力场、速度场在轴向和径向方向上的一系列变化规律,并通过数值拟合得到各工况与压力波动分布之间的关联式,从而为撞击流技术基本理论的发展和在实际生产中的应用提供一定的数学模型。主要结论包括:操作参数一定时,结构方式的改变对撞击区域的压力和速度波动随时间的整体变化趋势没有影响,转速为1000r/min时,反应器内压力场和速度场稳定时间需要3s;在结构方式一定时,操作参数的改变会影响流场稳定时间,物料空气组分含量分体积比为0是所需时间为3s左右,增加到0.3时所需时间为4.5s左右,增加到0.6时,所需时间为6s左右,同时当桨叶转速由1000r/min降低到500r/min时,流场稳定时间由3s增加到4.5s,转速过低则增加了流场稳定所需时间。结构方式和操作参数的改变对撞击区域速度、压力和压力波动强度的空间分布整体趋势也没有影响,各撞击面上的速度、压力在空间域上关于轴向中心线成对称结构分布,压力波动强度在空间域上关于径向中心线呈现对称结构分布,沿撞击面径向方向呈现先递增后递减并伴有小幅波动的趋势,各撞击面最大速度和压力值的位置会随离中心撞击面距离的增大而靠近轴向中心轴,同时离中心撞击面距离越远压力波动强度值越大。桨叶面积的增大有利于撞击过程中轴向压力和速度沿着径向压力和速度的转换,同时各撞击面最大压力值与无量纲桨叶面积成线性关系,与离中心撞击面的距离成倍数关系,面积越大,距离越远流场的压力波动值越大。筒径比的增大即导流筒长度的增加使导流筒内入口处轴向压力和速度增大,导流筒长度适度增大,撞击面中心处压力减小,中心轴向方向压力增大,但过度增大反而呈相反趋势,同时就速度场而言,随着筒径比的增加,导流筒入口处附近轴向速度增大,撞击后径向速度减小,各撞击平面上最大压力值随筒径比的变化成二次曲线关系,呈现先增加后减小的趋势。随着桨叶对置距离的增加,导流筒入口附近区域压力波动值和速度会增大,同时也减弱了撞击区域内压力波动和速度值,桨叶对置距离增加一倍,相应的压力值和速度值会减小一倍。当桨叶对置距离由100mm增加到140mm时,各撞击面上的压力波动强度值保持一致,说明对置距离增加到一定值时,压力波动不增加而是保持在一定范围内,各撞击面上最大压力值随桨叶无量纲对置距离成递减幂函数关系。物料中空气组分含量的增加会减弱撞击区域内压力波动和速度波动,流场不稳定阶段,速度波动幅度和剧烈程度随空气体积分数的增加而增大,同时循环区域与导流筒入口区域水的速度和流动范围也减小,空气含量的增大不利于整个流场中水的流动性能。反应器中空气成分主要集中在撞击面两侧,水成分主要集中在反应器上下底部,整个流场的体积分数分布关于径向轴线成对称结构,各撞击面上最大压力值与与空气组分体积比成指数函数关系。桨叶转速的增加加强了撞击区域内压力波动和速度波动,转速为1500r/min时相邻两撞击面压力波动强度的最大增幅值为123.92Pa,而转速为1000r/min和500r/min时其最大增幅分别为47.01Pa与13.17Pa。同一转速下随着离中心撞击面距离的增加,撞击面整体速度增大且变的均匀,同时导流筒外的循环区域速度也在增加,速度梯度明显增大,各撞击面上的最大压力与桨叶的转速及直径成递增幂函数关系。
[Abstract]:Liquid Continuous Phase Impinging Stream Reactor (LISR) is a new type of many new chemical reactors. Its excellent mixing performance comes from its ability to significantly enhance the mixing and dispersion process. The reactor has a special fluid flow structure. The slight change of its body structure and operating characteristics affects the mixing efficiency of the fluid in the whole flow field. From the reactor's own reaction efficiency, mass transfer and heat transfer and related reaction processes are carried out in the reactor, and the flow field and reaction process in the reactor are complex and changeable, which need to be solved by special study and measurement of the wave characteristics in the reactor. It is necessary and referential for explaining the mechanism of mixing process and optimizing the structure of the fluid under the configuration and operating parameters. In this paper, various basic geometric and physical models of LISR are established by the geometric model software Gambit, and then the whole flow in LISR is simulated by the numerical simulation software Fluent, which is commonly used in computational fluid dynamics. The numerical simulation of the pressure field was carried out. The pressure field in the impact zone and the circulating zone was obtained under different structural modes such as different blade types, different cylinder diameter ratios, different impact distances and different operating parameters such as material component content, velocity field under rotational speed, and fluctuation distribution of pressure field in the space and time domains. A series of variation laws of velocity field in axial and radial directions are obtained by numerical fitting, and the correlations between various working conditions and pressure fluctuation distribution are obtained, thus providing a certain mathematical model for the development of basic theory of impinging stream technology and its application in practical production. When the rotational speed is 1000r/min, the stability time of pressure field and velocity field in the reactor needs 3 s; when the structure is fixed, the change of operation parameters will affect the stability time of flow field, and the ratio of air component to volume is 0, which is the required time is 3 s left. At the same time, when the blade speed decreases from 1000r/min to 500r/min, the flow field stabilization time increases from 3S to 4.5s. When the speed is too low, the flow field stabilization time increases. The velocity and pressure on each impact surface are symmetrically distributed in the spatial domain with respect to the axial central line, and the pressure fluctuation intensity is symmetrically distributed in the spatial domain with respect to the radial central line, and increases first and then decreases along the radial direction of the impact surface with a small fluctuation. The position of the maximum velocity and pressure of each impact surface will approach the axial central axis with the increase of distance from the central impact surface, and the pressure fluctuation intensity will increase with the distance from the central impact surface. The maximum pressure is linear with the dimensionless blade area and multiples with the distance from the central impinging surface. The larger the area is, the larger the pressure fluctuation value is. The increase of the tube diameter ratio, i.e. the length of the diversion tube, makes the axial pressure and velocity increase at the inlet of the diversion tube, the length of the diversion tube increases moderately, and the center of the impinging surface increases. At the same time, the axial velocity near the inlet of the diversion tube increases with the increase of the diameter ratio of the tube, and the radial velocity decreases after the impact. The maximum pressure on each impact plane is quadratic curve with the change of the diameter ratio of the tube. The pressure fluctuation and velocity near the inlet of the diversion tube will increase with the increase of the blade offset distance, and the pressure fluctuation and velocity in the impact region will be weakened. The blade offset distance will be doubled, and the corresponding pressure and velocity will be doubled. When the blade offset distance increases from 100 mm to 140 mm, each impact will occur. The results show that the maximum pressure on the impact surface decreases exponentially with the dimensionless opposing distance of the blade, and the pressure fluctuation in the impact area decreases with the increase of air component content. The amplitude and intensity of velocity fluctuation increase with the increase of air volume fraction, and the velocity and flow range of water in the circulation area and the inlet area of diversion tube decrease. The increase of air content is not conducive to the flow performance of water in the whole flow field. On both sides of the reactor, the water composition is mainly concentrated at the bottom and top of the reactor. The volume distribution of the whole flow field is symmetrical with respect to the radial axis. The maximum pressure on each impact surface is exponentially related to the volume ratio of the air component. The maximum amplitude of pressure fluctuation intensity of the two impinging surfaces is 123.92 Pa, and the maximum amplitude of pressure fluctuation intensity is 47.01 Pa and 13.17 Pa respectively when the rotational speed is 1000 r/min and 500 r/min. Obviously, the maximum pressure on each impact surface increases exponentiation with the rotational speed and diameter of the blade.
【学位授予单位】：武汉工程大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ052
本文编号：2197233
[Abstract]:Liquid Continuous Phase Impinging Stream Reactor (LISR) is a new type of many new chemical reactors. Its excellent mixing performance comes from its ability to significantly enhance the mixing and dispersion process. The reactor has a special fluid flow structure. The slight change of its body structure and operating characteristics affects the mixing efficiency of the fluid in the whole flow field. From the reactor's own reaction efficiency, mass transfer and heat transfer and related reaction processes are carried out in the reactor, and the flow field and reaction process in the reactor are complex and changeable, which need to be solved by special study and measurement of the wave characteristics in the reactor. It is necessary and referential for explaining the mechanism of mixing process and optimizing the structure of the fluid under the configuration and operating parameters. In this paper, various basic geometric and physical models of LISR are established by the geometric model software Gambit, and then the whole flow in LISR is simulated by the numerical simulation software Fluent, which is commonly used in computational fluid dynamics. The numerical simulation of the pressure field was carried out. The pressure field in the impact zone and the circulating zone was obtained under different structural modes such as different blade types, different cylinder diameter ratios, different impact distances and different operating parameters such as material component content, velocity field under rotational speed, and fluctuation distribution of pressure field in the space and time domains. A series of variation laws of velocity field in axial and radial directions are obtained by numerical fitting, and the correlations between various working conditions and pressure fluctuation distribution are obtained, thus providing a certain mathematical model for the development of basic theory of impinging stream technology and its application in practical production. When the rotational speed is 1000r/min, the stability time of pressure field and velocity field in the reactor needs 3 s; when the structure is fixed, the change of operation parameters will affect the stability time of flow field, and the ratio of air component to volume is 0, which is the required time is 3 s left. At the same time, when the blade speed decreases from 1000r/min to 500r/min, the flow field stabilization time increases from 3S to 4.5s. When the speed is too low, the flow field stabilization time increases. The velocity and pressure on each impact surface are symmetrically distributed in the spatial domain with respect to the axial central line, and the pressure fluctuation intensity is symmetrically distributed in the spatial domain with respect to the radial central line, and increases first and then decreases along the radial direction of the impact surface with a small fluctuation. The position of the maximum velocity and pressure of each impact surface will approach the axial central axis with the increase of distance from the central impact surface, and the pressure fluctuation intensity will increase with the distance from the central impact surface. The maximum pressure is linear with the dimensionless blade area and multiples with the distance from the central impinging surface. The larger the area is, the larger the pressure fluctuation value is. The increase of the tube diameter ratio, i.e. the length of the diversion tube, makes the axial pressure and velocity increase at the inlet of the diversion tube, the length of the diversion tube increases moderately, and the center of the impinging surface increases. At the same time, the axial velocity near the inlet of the diversion tube increases with the increase of the diameter ratio of the tube, and the radial velocity decreases after the impact. The maximum pressure on each impact plane is quadratic curve with the change of the diameter ratio of the tube. The pressure fluctuation and velocity near the inlet of the diversion tube will increase with the increase of the blade offset distance, and the pressure fluctuation and velocity in the impact region will be weakened. The blade offset distance will be doubled, and the corresponding pressure and velocity will be doubled. When the blade offset distance increases from 100 mm to 140 mm, each impact will occur. The results show that the maximum pressure on the impact surface decreases exponentially with the dimensionless opposing distance of the blade, and the pressure fluctuation in the impact area decreases with the increase of air component content. The amplitude and intensity of velocity fluctuation increase with the increase of air volume fraction, and the velocity and flow range of water in the circulation area and the inlet area of diversion tube decrease. The increase of air content is not conducive to the flow performance of water in the whole flow field. On both sides of the reactor, the water composition is mainly concentrated at the bottom and top of the reactor. The volume distribution of the whole flow field is symmetrical with respect to the radial axis. The maximum pressure on each impact surface is exponentially related to the volume ratio of the air component. The maximum amplitude of pressure fluctuation intensity of the two impinging surfaces is 123.92 Pa, and the maximum amplitude of pressure fluctuation intensity is 47.01 Pa and 13.17 Pa respectively when the rotational speed is 1000 r/min and 500 r/min. Obviously, the maximum pressure on each impact surface increases exponentiation with the rotational speed and diameter of the blade.
【学位授予单位】：武汉工程大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ052
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