【摘要】：液-液旋流器利用混合液中不同介質(zhì)因密度差而受離心力不同,將多相介質(zhì)進行分離。在針對旋流器的數(shù)值模擬中,分散相液滴直徑常被看作定值,從而忽略旋流器流場對分散相液滴直徑的影響。本文針對分散相液滴在分離過程中產(chǎn)生的聚合和破裂現(xiàn)象,對旋流器的分離特性進行了研究。主要內(nèi)容及結(jié)論如下:對旋流器內(nèi)部流場、分散相液滴受力、分散相的破裂和聚合機理三個方面進行了理論分析。得出液-液旋流器內(nèi)部流場主要由外旋流的自由渦和內(nèi)旋流的強制渦構(gòu)成。當Weber數(shù)大于12時,液滴易產(chǎn)生破裂;僅當兩碰撞液滴的碰撞接觸時間超過臨界值時,才能產(chǎn)生液滴的聚合現(xiàn)象。通過數(shù)值模擬與實驗數(shù)據(jù)對比的方式,對低濃度分散相系統(tǒng)下液-液旋流器中的聚合和破裂核函數(shù)進行了優(yōu)選。同時,對液-液旋流器內(nèi)部流場分布、速度場分布、分散相濃度及分散相破裂和聚合區(qū)域分布進行了分析。研究結(jié)果表明:Lerh提出的聚合和破裂核函數(shù)較其它函數(shù)更適合低濃度分散相下旋流器模擬,其與實驗結(jié)果誤差接近12%。各向速度和湍流強度分布呈組合渦形式與理論分析一致。對旋流器內(nèi)部分散相的體積分數(shù)及源項進行了分析,且對不同入口流量下旋流器內(nèi)部流場及分散相分布進行了對比。結(jié)果表明:分散相的聚合率隨分散相濃度增加而增大,破裂率隨湍流強度以及速度梯度的增大而增大。隨著入口流量的增加,旋流器內(nèi)部各向速度及湍流強度同時增大;分散相在圓柱段、大圓錐段及小圓錐段下端濃度隨之增加。入口流量的增加對于破裂現(xiàn)象起著促進作用,且隨著速度的增加,破裂現(xiàn)象的增強幅度隨之降低。推導(dǎo)出一種低濃度輕質(zhì)分散相下,液-液旋流器分離效率計算方法,并分別對不同入口流量和結(jié)構(gòu)下的實驗結(jié)果進行對比。該公式計算值與實驗值平均誤差為5%,當分離效率低于10%時,隨著分散相直徑的降低,誤差逐漸增大。由于該公式未考慮分散相的相互作用,因此在分散相液滴破裂現(xiàn)象明顯時其準確率降低。
[Abstract]:The liquid-liquid hydrocyclone separates the multiphase medium by the different centrifugal force due to the density difference in the mixed medium. In the numerical simulation of hydrocyclone, the diameter of dispersed droplet is often regarded as a constant value, so the influence of flow field on the diameter of dispersed droplet is ignored. In this paper, the separation characteristics of hydrocyclone are studied in view of the polymerization and rupture of dispersed droplets in the separation process. The main contents and conclusions are as follows: the flow field in the hydrocyclone, the droplet force in the dispersed phase, the fracture and polymerization mechanism of the dispersed phase are analyzed theoretically. It is concluded that the internal flow field of the hydrocyclone is mainly composed of the free vortex of the outer swirl and the forced vortex of the inner swirl. When the Weber number is greater than 12:00, the droplet is prone to rupture, and only when the collision contact time of the two colliding droplets exceeds the critical value, the droplet polymerization can occur. By comparing numerical simulation with experimental data, the polymerization and fracture kernel functions in liquid-liquid hydrocyclone with low concentration dispersion phase were optimized. At the same time, the distribution of flow field, velocity field, concentration of dispersed phase, fracture and polymerization region of dispersed phase in liquid-liquid cyclone are analyzed. The results show that the polymerization and rupture kernel functions proposed by the President Lerh are more suitable for the simulation of hydrocyclone with low concentration dispersion phase than other functions, and the error is close to that of the experimental results. The distributions of velocity and turbulence intensity in each direction are consistent with the theoretical analysis in the form of combined vortex. The volume fraction and source term of the dispersed phase in the hydrocyclone are analyzed, and the flow field and the dispersed phase distribution in the hydrocyclone under different inlet flow rates are compared. The results show that the polymerization rate of the dispersed phase increases with the increase of the concentration of the dispersed phase, and the fracture rate increases with the increase of the turbulence intensity and the velocity gradient. With the increase of inlet flow rate, the velocity and turbulence intensity increase simultaneously, and the concentration of dispersed phase increases at the lower end of cylinder, big cone and small cone. The increase of inlet flow rate promotes the fracture phenomenon, and with the increase of velocity, the increasing amplitude of fracture phenomenon decreases. A method for calculating the separation efficiency of liquid-liquid hydrocyclone with low concentration and light dispersion phase is derived, and the experimental results under different inlet flow rates and structures are compared respectively. The average error between the calculated value and the experimental value is 5. When the separation efficiency is lower than 10, the error increases with the decrease of the diameter of the dispersed phase. Because the interaction of dispersed phase is not taken into account in this formula, the accuracy of the formula is reduced when the droplet fracture of dispersed phase is obvious.
【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】：TQ051.8

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