搅拌釜三维流场的雷诺应力模型数值模拟

引言 近年来,雷诺平均Navier-Stokes方程及其封闭方程组成的湍流模型在应用于搅拌釜复杂湍流现象的模拟上取得了成功,主要是采用标准k-ε[1]、RNG k-ε[2]等模型.     

001×7(732)阳离子交换树脂催化醋酸甲酯水解反应过程模拟与优化

在充分搅拌和可忽略粒度影响条件下,测定了间歇搅拌反应釜中001×7(732)阳离子交换树脂催化醋酸甲酯水解反应动力学数据,建立了其拟均相与非均相反应动力学模型,进行了模型筛选和参数估值.结果表明,醋酸甲酯与水均吸附,表面反应为控制步骤的非均相反应动力学模型能较好地拟合实验数据,并满足统计检验.根据优选的反应动力学模型,对醋酸甲酯水解过程进行了模拟计算,考察了反应温度、树脂浓度、水酯摩尔比对水解过程的影响,得到的优化反应条件为:反应温度55℃、树脂浓度260 g·L-1、水酯摩尔比1.5∶1.此时反应90 min接近醋酸甲酯平衡水解率34.8%.     

Cs-137γ射线CT测量标准Rushton搅拌釜气含率分布及数字图像重建

对一个Cs-137辐射源、7个扇型排列探测器旋转方式的γ射线CT测量气液反应釜气含率分布实验装置作了介绍,建立了该实验装置测量气含率分布和数字彩色图像重建的数学模型,并对20 cm内直径的标准Rushton气液搅拌釜进行了空釜扫描验证实验和气液搅拌两种状态的比较实验.实验结果证明该CT实验装置测量结果准确,所形成气液两相气含率分布数字彩色图像清晰可辨,空间分辨率可达2 mm.为了进一步进行气含率分布的定量比较,列出了平均气含率沿无因次半径的变化曲线.     

基于离散颗粒法模拟搅拌釜气含率分布

The discrete particle method was used to simulate the distribution of gas holdup in a gas-liquid standard Rushton stirred tank. The gas phase was treated as a large number of bubbles and their trajectories were tracked with the results of motion equations. The two-way approach was performed to couple the interphase momentum exchange. The turbulent dispersion of bubbles with a size distribution was modeled using a stochastic tracking model, and the added mass force was involved to account for the effect of bubble acceleration on the surrounding fluid. The predicted gas holdup distribution showed that this method could give reasonable prediction comparable to the reported experimental data when the effect of turbulence was took into account in modification for drag coefficient.     

基于多层次过程强化的化学工程教学改革探讨

在国家"双一流"高校建设背景下,实施化学工程学科教学改革对于提高教学质量和学科影响力具有重要作用。以化学反应工程课程教学为例,将多层次过程分析与计算机模拟有机结合,开展项目驱动式教学,可以让学生不断提高综合分析能力,增强工程意识,做到从理论知识到实际应用的有序转变。     

涡-气泡作用模型对搅拌釜中气泡湍流扩散影响的数值研究

Based on trajectory equations of gas bubble, an eddy-bubble interaction (EBI) model was developed. This model considered the effect of non-drag forces and took the eddy-bubble interaction time as the refreshing time scale of turbulent fluctuations. The relationship between the crossing-eddy time and the eddy lifetime was discussed, and the predicted distributions of radial, axial ve-locities of bubbles and gas holdup were also given. Compared with eddy lifetime (EL) model, the EBI model gives somewhat smaller axial velocity in the upper circulation region and larger velocity in the lower circulation region, causing that fewer bubbles reach the lower circulation region and gas holdup becomes higher in the upper circulation region. The predicted gas holdup by the EBI model approaches closer to the experimental data in the discharge stream region.     

Rushton搅拌釜内的气含率分布及其流动特性的模拟

利用雷诺应力模型结合多参考系法模拟了Rushton气液搅拌釜内的气液流动特性,得到了不同截面处气含率大小分布规律,并与γ射线CT实验所测得的结果做了比较,发现除排出流区CFD模拟值与实验值相差较大外,上循环区与下循环区都吻合得较好;结果表明排出流区的气含率最高,在搅拌桨高速旋转下,流体沿叶片端面急速排出,湍动也十分强烈...     

应用SST k-ω湍流模型计算Rushton搅拌釜流场

应用SSTkω-湍流模型对Rushton搅拌釜流场进行了计算,并与文献报道实验数据以及标准k-ε模型、RNGkω-模型预测结果进行了比较。结果表明SSTkω-模型所计算的排除流量准数与实验值相差较小,桨叶区速度场与实验数据吻合较好,略优于标准k-ε模型,同时也给出了近壁区的计算结果。在湍动动能的预报上,SSTk-ω模型值与标准k-ε模型比较接近,优于RNGkε-模型,但与实验值都还不同程度地存在着一些差异。     

Rushton搅拌釜气含率分布CT彩色数字成像模型研究

为了建立和实现137Cs γ射线CT(computed tomography)测量Rushton气液搅拌釜气含率分布彩色数字成像模型,根据137Cs发射γ射线信号和探测器接受信号的Poisson分布模型和气液两相流体吸收衰减辐射信号的二项分布模型,在给出接受信号实验样本空间条件下,采用最大似然参数估计法,对容器断面气液...     

1,6-己二醇制备工艺进展

综述了1,6-己二醇的生产工艺,主要包括传统的以石油基为原料和新兴的以生物基为原料的工艺路线。目前,工业上仍采用以石油基原料为主的工艺路线,存在环境污染、能耗偏高、产物选择性偏低或产物纯度不高等问题。烯烃直接光催化水合制备1,6-己二醇的方法具有清洁、能耗低、副产物少等特点,但缺乏高效的水合催化剂。以生物基为原料制备1,6-己二醇具有环境污染小、原料可再生的特点,有良好的发展前景。