本文選題：稠密顆粒流 + 氣-液-固三相曳力方程�。� 參考：《天津大學(xué)》2015年博士論文

【摘要】：臥式螺旋離心機(jī)是工業(yè)上常用的固液分離設(shè)備,其基本原理是利用離心力和螺桿軸向推動力實(shí)現(xiàn)密度不同的液固兩相的分離。該設(shè)備具有自動化程度高,能夠無人值守連續(xù)性生產(chǎn)的特點(diǎn),應(yīng)用前景十分廣闊。在臥螺離心機(jī)正常工作過程時轉(zhuǎn)鼓內(nèi)存在氣-液-固三相流中各相之間耦合運(yùn)動,而現(xiàn)有的兩相流理論無法準(zhǔn)確描述氣-液-固多相顆粒流在離心機(jī)轉(zhuǎn)鼓內(nèi)流動狀態(tài),使離心機(jī)的固液分離理論不能滿足實(shí)際的工業(yè)生產(chǎn)需求。因此,本文基于歐拉模型理論體系,建立能夠用于多相流的曳力模型,在螺旋線坐標(biāo)下構(gòu)建臥螺離心機(jī)數(shù)學(xué)模型,分析固液兩相在離心機(jī)內(nèi)的運(yùn)動機(jī)理,研究在不同操作條件下顆粒流在離心機(jī)內(nèi)部的運(yùn)動規(guī)律,提出離心機(jī)出口物料含水率的預(yù)測方程,為離心機(jī)的結(jié)構(gòu)設(shè)計(jì)和操作工藝優(yōu)化提供理論基礎(chǔ)和科學(xué)依據(jù)。基于顆粒流運(yùn)動理論,本文完善了稠密顆粒運(yùn)動本構(gòu)方程以描述在離心機(jī)工作過程中固相顆粒在其內(nèi)部的運(yùn)動行為。通過在傳統(tǒng)稠密顆粒流固相摩擦壓力方程中提出了新的壓力常數(shù),在固相摩擦黏度方程中添加顆粒碰撞摩擦黏度方程和滯后運(yùn)動方程,并提出了新的流體湍流與顆粒碰撞對擬熱動能源項(xiàng)模型以封閉顆粒擬熱動能平衡方程,完善了稠密顆粒運(yùn)動本構(gòu)方程。并通過顆粒擬靜態(tài)堆積實(shí)驗(yàn)和稠密顆粒流剪切力運(yùn)動實(shí)驗(yàn),驗(yàn)證了該本構(gòu)方程對模擬稠密顆粒流運(yùn)動行為的可靠性。應(yīng)用建立的稠密顆粒流運(yùn)動模型方程,研究了顆粒群擬靜態(tài)堆積和剪切力運(yùn)動過程中的力學(xué)性質(zhì)的變化。針對現(xiàn)有連續(xù)相-分散相的兩相流曳力理論模型,無法模擬臥螺離心機(jī)運(yùn)行過程中氣-液-固三相并行存在的運(yùn)動狀態(tài),本文建立了新的多相流流體力學(xué)耦合計(jì)算模型(TCP理論模型)用以模擬氣-液-固三相間的耦合運(yùn)動行為關(guān)系。根據(jù)臥螺離心機(jī)內(nèi)氣相和液相的運(yùn)動特點(diǎn),在該模型中,氣相和液相按照體積分?jǐn)?shù)加權(quán)的形式組合為一個新的虛擬連續(xù)相,進(jìn)而將氣-液-固多相流體系簡化為虛擬連續(xù)相-分散相的多相流體系。將原有的氣-液-固三相間復(fù)雜的曳力作用行為簡化為兩部分:一是虛擬連續(xù)相與分散相之間的曳力作用;二是虛擬連續(xù)相內(nèi)部的動量分配過程。通過氣-液-固三相鼓泡床實(shí)驗(yàn)對該模型進(jìn)行了驗(yàn)證,結(jié)果表明TCP理論模型有效的簡化了數(shù)值模型中的各個相間復(fù)雜的曳力耦合計(jì)算過程,在非均勻性相分布體系中實(shí)現(xiàn)了有效平滑的從多相流流動到單相流運(yùn)動過程中的過渡,提高了計(jì)算精度。采用TCP理論模型,對三相鼓泡床中的氣相、固相和液相的運(yùn)動狀態(tài)進(jìn)行了模擬研究,討論這三相流體之間的運(yùn)動耦合性質(zhì)及其相互作用關(guān)系。采用本文完善的稠密顆粒流運(yùn)動本構(gòu)方程和提出的TCP理論模型,在螺旋運(yùn)動參考系下建立了臥螺離心機(jī)數(shù)值模型,用以描述離心機(jī)轉(zhuǎn)鼓和螺桿的相對運(yùn)動過程對轉(zhuǎn)鼓內(nèi)混合物料運(yùn)動的作用規(guī)律,并通過臥螺離心機(jī)污泥脫水實(shí)驗(yàn)的研究驗(yàn)證了數(shù)學(xué)模型對于臥螺離心機(jī)內(nèi)部流場運(yùn)動模擬的可靠性。在此基礎(chǔ)上,本文分析了固相和液相在離心機(jī)內(nèi)部運(yùn)動機(jī)理,當(dāng)固液兩相在離心力作用下按照密度差在離心機(jī)內(nèi)部分層后,這兩相在離心機(jī)軸向推動作用下的運(yùn)動發(fā)生變化:由于固相顆粒群與離心機(jī)內(nèi)壁面具有較大的摩擦作用,其所受到離心機(jī)的剪切作用較強(qiáng),因此固相運(yùn)動速度隨離心機(jī)內(nèi)壁面的推動作用逐漸增加,固相的運(yùn)動方向亦隨之在離心機(jī)筒段內(nèi)發(fā)生折返;與之相對,由于液相的黏度較小,其所受到的離心機(jī)的剪切作用較弱,因此液相的運(yùn)動方向較難發(fā)生變化。固相顆粒在進(jìn)入離心機(jī)后會向離心機(jī)的小端方向運(yùn)動,而液相則從離心機(jī)的大端處溢流而出。所以固液兩相在離心機(jī)軸向方向按照彼此所受到的剪切作用的強(qiáng)弱,這兩相之間的相對運(yùn)動方向發(fā)生改變。通過研究不同操作條件下離心機(jī)內(nèi)部流場流動行為,得到了離心力和軸向推力對固相和液相在離心機(jī)內(nèi)部運(yùn)動的影響規(guī)律。針對在離心機(jī)不同操作條件下固相和液相在離心機(jī)出口處的運(yùn)動過程研究,提出了臥螺離心機(jī)出口物料含水率預(yù)測方程。
[Abstract]:The horizontal spiral centrifuge is a commonly used solid-liquid separation equipment in industry. Its basic principle is to separate the liquid and solid two phases with different density by using the centrifugal force and the axial thrust of the screw. The equipment has the characteristics of high automation and unmanned continuous production. The application of the equipment is very wide. The normal working process of the decubitus centrifuge is done. When the current theory of two phase flow can not accurately describe the flow state of gas liquid solid particle flow in the centrifuge drum, the theory of separation of solid and liquid of the centrifuge can not meet the actual demand of industrial production. Therefore, this paper is based on the Euler model theory system. The model of the drag force for the multiphase flow is enough, and the mathematical model of the horizontal screw centrifuge is constructed under the spiral coordinate. The movement mechanism of the solid and liquid two phases in the centrifuge is analyzed. The motion law of the particle flow in the centrifuge is studied under different operating conditions. The prediction equation of the water content of the centrifuge outlet is put forward, which is the structure design and operation of the centrifuge. The process optimization provides theoretical basis and scientific basis. Based on the theory of particle flow motion, this paper perfects the motion constitutive equation of dense particles to describe the motion behavior of solid particles in the centrifuge working process. A new pressure constant is put forward in the traditional dense particle flow solid friction pressure equation, and the solid friction viscosity in solid phase is obtained. In the degree equation, a particle collision friction viscosity equation and a lagging motion equation are added. A new fluid turbulence and particle collision model is proposed for the quasi thermal energy term model with closed particle quasi thermal equilibrium equation, and the motion constitutive equation of dense particles is perfected. The reliability of the constitutive equation is verified to simulate the motion behavior of dense granular flow. The change of mechanical properties in the process of quasi static accumulation and shear force movement is studied by using the motion model equation of dense particle flow. The theory model of the current drag force of the current continuous phase and dispersion phase can not simulate the movement of the horizontal screw centrifuge. In the course of the moving state of gas liquid solid three-phase, a new multi phase flow hydrodynamic coupling calculation model (TCP theoretical model) is established to simulate the coupling motion behavior relationship between gas liquid solid three phase. According to the motion characteristics of the gas phase and liquid phase in the decanter centrifuge, the gas phase and liquid phase are in accordance with the volume fraction in this model. The weighted form is combined into a new virtual continuous phase, and then the gas liquid solid multiphase flow system is simplified as a virtual continuous phase dispersed phase multiphase flow system. The original complex drag action of the gas liquid solid three phase is simplified into two parts: one is the drag force between the virtual continuous phase and the dispersed phase, and the two is in the virtual continuous phase. The momentum distribution process of the part is verified by a gas-liquid solid three-phase bubbling bed experiment. The results show that the TCP theoretical model effectively simplifies the complex drag coupling calculation process of each phase in the numerical model, and realizes the effective smooth sliding from multiphase flow to single phase flow in the non-uniform phase distribution system. The moving state of gas phase and solid phase and liquid phase in a three-phase bubbling bed is simulated by using the TCP theory model. The motion coupling properties and the interaction relationship between the three-phase fluid are discussed. The dynamic constitutive equation of dense particle flow and the proposed TCP theory model are adopted in this paper. The numerical model of the decanter centrifuge is set up under the reference frame of the spiral motion to describe the action of the relative motion of the centrifuge drum and the screw on the movement of the mixed material in the drum, and the reliability of the mathematical model is verified by the study of the sludge dewatering experiment of the decanter centrifuge. On this basis, the motion mechanism of the solid and liquid phase in the centrifuge is analyzed. When the solid-liquid two phases are stratified in the centrifuge under the action of the density difference under the action of the centrifugal force, the motion of the two phase under the centrifugal force of the centrifuge is changed. As the solid particle group has greater friction with the inner wall of the centrifuge, it is subjected to a large friction effect. The shear action of the centrifuge is stronger, so the solid motion velocity increases with the inner wall of the centrifuge, and the motion direction of the solid phase is also reentrant in the centrifuge tube section. After entering the centrifuge, the solid particles move to the small end of the centrifuge, and the liquid phase spillage from the large end of the centrifuge. So the solid and liquid two phases are in the axial direction of the centrifuge in accordance with the shear strength of each other, and the relative motion direction between the two phases is changed. The centrifuge under different operating conditions is studied. The effect of centrifugal force and axial thrust on the motion of the solid and liquid phase in the centrifuge is obtained by the centrifugal force and the axial thrust. The prediction equation for the water content of the outlet material of the centrifuge is put forward in view of the movement process of the solid and liquid phase at the centrifuge outlet under the different operating conditions of the centrifuge.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TQ051.84

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本文編號：1911189