本文關鍵詞：射流循環(huán)DTB結晶器的水力學模擬與實驗　出處：《大連理工大學》2016年碩士論文　論文類型：學位論文

  更多相關文章： DTB結晶器 射流泵 數(shù)值模擬 PIV

【摘要】：射流技術廣泛應用于混合和傳動過程,用射流實現(xiàn)DTB結晶器內(nèi)攪拌槳軸向推進功能,可有效降低由攪拌槳和晶體碰撞引起的二次成核,提高產(chǎn)品粒度。本文通過模擬,優(yōu)化以及實驗,研究了DTB結晶器導流筒的結構和流場,為射流循環(huán)DTB結晶器設計和優(yōu)化提供指導。具體的研究內(nèi)容如下：采用RNG k-ε湍流模型對直導流筒射流DTB結晶器的單相流流場進行了數(shù)值模擬,選取最優(yōu)導流筒筒徑,并利用歐拉多相流模型對該結構下的結晶器進行模擬分析。結果表明,導流筒內(nèi)射流滿足線性擴展,軸向速度分布基本滿足高斯分布。剛進入導流簡內(nèi)的射流主體段,軸線速度倒數(shù)與流程呈良好的線性關系,隨射流發(fā)展,軸線速度加速衰減。在噴嘴入口直徑恒定時,循環(huán)速率比(γγ)隨導流筒擋板間環(huán)隙面積與導流筒橫截面積比(β)的增加呈先增大再減小的趨勢,存在最優(yōu)值。直導流筒為最優(yōu)直徑時,射流DTB結晶器中導流筒內(nèi)顆粒濃度分布沿徑向方向減小,其循環(huán)速率比較單相流模擬結果略低,但基本可實現(xiàn)顆粒濃度較為均勻的分布,滿足DTB結晶器的水力學要求。參照射流泵結構對結晶器導流筒進行優(yōu)化,利用RNGk-ε湍流模型模擬了不同結晶器內(nèi)的流場,分析不同導流筒結構下射流DTB結晶器內(nèi)流體流動；利用組分輸運模型對結晶器有效區(qū)域進行階躍示蹤法實驗,考察其混合特性；利用滑移網(wǎng)格法模擬常規(guī)DTB結晶器內(nèi)的流動性質(zhì),并與射流DTB結晶器的流場和能耗進行對比；利用歐拉多相流模型模擬不同導流筒結構的射流DTB結晶器的顆粒濃度場,對比顆粒濃度分布。結果表明,參照射流泵結構優(yōu)化的導流筒提高了內(nèi)循環(huán)量,本例中較直導流筒最高提升23%,同時對結晶器內(nèi)的混合有一定的促進作用。同時,相同內(nèi)循環(huán)流量下,射流泵DTB結晶器與常規(guī)DTB結晶器相比,單位體積能耗稍小。射流循環(huán)可較好的實現(xiàn)DTB結晶器內(nèi)顆粒懸浮,且相比于其它射流DTB結晶器,結構優(yōu)化的射流泵DTB結晶器顆粒分布更加均勻,顆粒相的內(nèi)循環(huán)量更高。因此射流泵導流筒的優(yōu)化,不僅使射流方案滿足DTB結晶器溶液充分混合、顆粒均勻懸浮的水力學要求,在能耗上較常規(guī)DTB結晶器也有一定優(yōu)勢。利用粒子圖像測速法(PIV)考察不同攪拌位置與轉速下常規(guī)DTB結晶器的流場,以及不同噴嘴直徑與外循環(huán)流量下射流DTB結晶器的流場,并與數(shù)值模擬結果對比。結果表明,RNGk-ε湍流模型可較為準確有效的模擬常規(guī)DTB結晶器與射流DTB結晶器內(nèi)的流場。
[Abstract]:Jet technology is widely used in mixing and transmission process, with the realization of DTB jet crystallizer impeller axial push function, can effectively reduce the two secondary nucleation and crystal caused by impeller collision, improve the product size. Through the simulation, optimization and experimental research, the structure and flow field of DTB crystallizer of the tube. Provide guidance for the design and optimization of jet loop DTB crystal. The specific contents are as follows: single RNG k- turbulence model of straight guide tube jet DTB mold flow field numerical simulation was carried out to select the optimal draft tube diameter, and the Eulerian multiphase flow model of the mould structure is carried out simulation analysis. The results show that the draft tube jet linear expansion, axial velocity distribution satisfies the Gauss distribution. Just enter the main jet section of the diversion in the axis, reciprocal velocity is a linear relationship with the flow With the development of the jet axis, and accelerate the speed of decay. At the nozzle entrance diameter constant, circulation rate ratio () with draft tube baffle between the annular area and diversion tube cross-sectional area ratio (beta) increases firstly increased and then decreased gradually, there is an optimal value. The optimal diameter of the straight flow tube. Is the crystallization of DTB guided jet flow decreases along the radial direction, the particle concentration distribution in the cylinder, the comparison of the simulation results of single-phase flow circulation rate is slightly lower, but can achieve the basic particle concentration distribution is uniform, meet DTB crystallizer hydraulic requirements. According to the draft tube crystallizer to optimize structure of jet pump, numerical simulation of different crystallization is the use of RNGk- turbulence model, DTB analysis of fluid jet flow in the mould of different draft tube structure; the component transport model of the effective area of crystallizer step experimental tracer method, the mixing characteristics by sliding; Simulation of flow properties of conventional DTB mold moving grid method, and the flow and energy consumption and jet DTB crystallizer were compared; the particle concentration distribution by using Eulerian multiphase flow model to simulate the jet DTB mold different draft tube structure, concentration of particle size distribution. The results show that the optimization of draft tube structure of the pump flow and irradiation the increase in circulation, in this case a straight guide tube up 23%, and mixed in the mold to a certain extent. At the same time, the same internal circulation flow, compared with conventional jet pump DTB crystallizer DTB crystallizer, energy consumption per unit volume smaller. Jet loop can realize particle suspension DTB mold good, and compared to other DTB jet mould structure optimization of jet pump is the crystallization of DTB particle distribution is more uniform, the particle internal circulation quantity higher. Therefore the optimization of jet pump draft tube, not only make the jet program Meet the DTB mold solution mixing, hydraulics particles suspended, in energy consumption compared with the conventional DTB mold also has certain advantages. By using particle image velocimetry (PIV) effects of different mixing flow field position and speed of conventional DTB crystallizer, and different nozzle diameter and jet flow straight DTB crystallizer circulating flow the results of numerical simulation and comparison. The results show that the RNGk- turbulence model can accurately simulate the conventional DTB crystallizer and jet DTB crystallizer effectively in the field.

【學位授予單位】：大連理工大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TQ051.63

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本文編號：1379571