液體連續(xù)相撞擊流強化傳遞過程的波動特性
發(fā)布時間：2018-08-22 13:26
【摘要】：液體連續(xù)相撞擊流反應器(LISR)是眾多新型化工反應器中的一種新類型,其優(yōu)良的混合性能來源于自身能夠顯著強化混合分散過程,而反應器具有特殊的流體流動結構,其身結構與操作特性的微小變化又影響整個流場中流體的混合效率、分散范圍和強度等。從反應器自身反應效率來看,傳質傳熱及相關反應過程都是在反應器中進行,而且反應器中流場和反應過程存在復雜多變性,需要通過對反應器內波動特性特研究與測定來解決。所以研究撞擊流反應器在不同結構方式和操作參數(shù)下流體的波動特性對闡述其混合過程機理以及優(yōu)化結構具有必要性和參考性。本文通過幾何模型軟件Gambit建立探究所需的各種LISR基本幾何物理模型,再由常用計算流體力學所用數(shù)值模擬軟件即Fluent對LISR內整個流場進行數(shù)值模擬,探討了在不同結構方式如:不同槳葉類型、不同筒徑比、不同撞擊距離下與不同操作參數(shù)如:物料組分含量、轉速條件下速度場、壓力場在空間域和時間域上的波動分布規(guī)律,得到各種工況下撞擊區(qū)域和循環(huán)區(qū)域壓力場、速度場在軸向和徑向方向上的一系列變化規(guī)律,并通過數(shù)值擬合得到各工況與壓力波動分布之間的關聯(lián)式,從而為撞擊流技術基本理論的發(fā)展和在實際生產中的應用提供一定的數(shù)學模型。主要結論包括:操作參數(shù)一定時,結構方式的改變對撞擊區(qū)域的壓力和速度波動隨時間的整體變化趨勢沒有影響,轉速為1000r/min時,反應器內壓力場和速度場穩(wěn)定時間需要3s;在結構方式一定時,操作參數(shù)的改變會影響流場穩(wěn)定時間,物料空氣組分含量分體積比為0是所需時間為3s左右,增加到0.3時所需時間為4.5s左右,增加到0.6時,所需時間為6s左右,同時當槳葉轉速由1000r/min降低到500r/min時,流場穩(wěn)定時間由3s增加到4.5s,轉速過低則增加了流場穩(wěn)定所需時間。結構方式和操作參數(shù)的改變對撞擊區(qū)域速度、壓力和壓力波動強度的空間分布整體趨勢也沒有影響,各撞擊面上的速度、壓力在空間域上關于軸向中心線成對稱結構分布,壓力波動強度在空間域上關于徑向中心線呈現(xiàn)對稱結構分布,沿撞擊面徑向方向呈現(xiàn)先遞增后遞減并伴有小幅波動的趨勢,各撞擊面最大速度和壓力值的位置會隨離中心撞擊面距離的增大而靠近軸向中心軸,同時離中心撞擊面距離越遠壓力波動強度值越大。槳葉面積的增大有利于撞擊過程中軸向壓力和速度沿著徑向壓力和速度的轉換,同時各撞擊面最大壓力值與無量綱槳葉面積成線性關系,與離中心撞擊面的距離成倍數(shù)關系,面積越大,距離越遠流場的壓力波動值越大。筒徑比的增大即導流筒長度的增加使導流筒內入口處軸向壓力和速度增大,導流筒長度適度增大,撞擊面中心處壓力減小,中心軸向方向壓力增大,但過度增大反而呈相反趨勢,同時就速度場而言,隨著筒徑比的增加,導流筒入口處附近軸向速度增大,撞擊后徑向速度減小,各撞擊平面上最大壓力值隨筒徑比的變化成二次曲線關系,呈現(xiàn)先增加后減小的趨勢。隨著槳葉對置距離的增加,導流筒入口附近區(qū)域壓力波動值和速度會增大,同時也減弱了撞擊區(qū)域內壓力波動和速度值,槳葉對置距離增加一倍,相應的壓力值和速度值會減小一倍。當槳葉對置距離由100mm增加到140mm時,各撞擊面上的壓力波動強度值保持一致,說明對置距離增加到一定值時,壓力波動不增加而是保持在一定范圍內,各撞擊面上最大壓力值隨槳葉無量綱對置距離成遞減冪函數(shù)關系。物料中空氣組分含量的增加會減弱撞擊區(qū)域內壓力波動和速度波動,流場不穩(wěn)定階段,速度波動幅度和劇烈程度隨空氣體積分數(shù)的增加而增大,同時循環(huán)區(qū)域與導流筒入口區(qū)域水的速度和流動范圍也減小,空氣含量的增大不利于整個流場中水的流動性能。反應器中空氣成分主要集中在撞擊面兩側,水成分主要集中在反應器上下底部,整個流場的體積分數(shù)分布關于徑向軸線成對稱結構,各撞擊面上最大壓力值與與空氣組分體積比成指數(shù)函數(shù)關系。槳葉轉速的增加加強了撞擊區(qū)域內壓力波動和速度波動,轉速為1500r/min時相鄰兩撞擊面壓力波動強度的最大增幅值為123.92Pa,而轉速為1000r/min和500r/min時其最大增幅分別為47.01Pa與13.17Pa。同一轉速下隨著離中心撞擊面距離的增加,撞擊面整體速度增大且變的均勻,同時導流筒外的循環(huán)區(qū)域速度也在增加,速度梯度明顯增大,各撞擊面上的最大壓力與槳葉的轉速及直徑成遞增冪函數(shù)關系。
[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.
【學位授予單位】：武漢工程大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ052
本文編號：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.
【學位授予單位】：武漢工程大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ052
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