搅拌釜内空气-PPG分散特性的数值模拟与实验测量

文章借助FLUENT软件,采用Euler-Euler方法、Laminar层流模型、MFR法处理旋转搅拌桨、气泡单一尺寸假设,对搅拌釜内空气-PPG体系的气含率和搅拌功率进行了数值模拟,模拟结果与实验值吻合较好.同时,考察了搅拌转速和通气流量对气含率和通气搅拌功率的影响.结果表明,数值模拟所选取的模型,能较好地模拟搅拌釜内空气-PPG体系的分散特性.     

微污染原水混凝动力学初步研究

实验采用激光微米粒度测试仪在线测定混凝处理时絮粒的成长过程,并初步探讨了搅拌槽内三种絮凝剂Pac、PFC、PAM以及复配的絮凝剂PAC与PAM、PFC与PAM处理长江水时的絮凝动力学.研究结果表明,在絮凝初期絮团的生长过程可以用絮凝动力学方程lnN/N0=-kt描述.其中,k值为初始速率常数.k值越大,絮凝速度越快,最终的混凝效果越好;反之,k值越小,则絮凝速度越慢,最终的混凝效果越差.在实际应用中可以通过k值的大小来确定混凝时所需要的最佳条件.     

T型微通道内气泡生成的实验研究

利用高速摄像仪CCD可视化实验系统研究T型微通道内气泡生成过程,分别以去离子水和氩气作为液相和气相,通过改变两相入口的压力,在不同结构的微通道内对气泡生成机理进行实验研究。结果表明,当气液相的通道直径比大于1时,随着直径比值进一步增大,气泡生成直径和生成周期随着气相压力的增加整体呈增大趋势。但对于气泡大小均匀度,直径比值越小,均匀度越好,且随着直径比值减小,微通道内两相流区域所占区域变窄。这些结论为获得尺寸较小、生成频率稳定、均匀度最佳的微气泡提供必要的实验依据。     

用蒸发和液化说明沸腾(初二)

观察水沸腾实验时会看到:开始,气泡在器壁上生成,当体积增大到一定程度后,气泡就脱离器壁上升,并且体积逐渐减小,大部分在还没有达到液面就消失了.当温度升高到一定值后,上升的气泡体积不再减小而是增大,最后冲破液面,水就沸腾了.对整个沸腾过程,可以用蒸发和液化的知识作初步的解释.     

氨气化学吸收过程气液两相流的数值模拟

应用计算流体动力学(CFD)的研究方法,对氨气(尿素醇解法合成碳酸乙烯酯工艺的副产物)在磷酸中化学吸收的气液两相流过程进行了数值模拟.模拟计算采用了多重参考系(MRF)模型和流体体积函数(VOF)多相流模型,通过建立气泡流动的准三维流场和加载传质及非均相反应UDF程序来进行.结果表明,在强烈机械搅拌下进行鼓泡吸收时,N...     

提高搅拌实验模拟混合沉淀工艺的相似性探讨

本文通过对混凝动力学基本公式进行推导,求出水力梯度G值与搅拌实验转速的关系,同时对自来水厂混合、絮凝、沉淀三个净水处理工艺条件进行计算,依据计算结果对烧杯混凝搅拌实验进行改进,提高模拟工艺的相似性,为生产运行提供更为精确的实验数据,取到很好的经济效益。     

侧伸搅拌厌氧反应器流场的数值模拟

侧伸搅拌厌氧反应器是一常用的厌氧反应器。对侧伸搅拌厌氧反应器进行数值模拟。模拟结果表明,流体在反应器内形成循环流动,反应器内的湍流特性分布并不均匀。     

环管反应器中高粘度催化剂在液—固体系的混合特征研究

在环管反应器中对高粘度催化剂在液固体系的混合特征进行了研究,探讨了催化剂粘度、循环速率、固含率以及混合雷诺数对混合时间的影响,对混合过程参数进行了准数关联,并建立了混合过程的数学模型,模型值与实验值吻合较好.     

几个小实验的成功做法

高一化学新教材Ｐ6 7[实验 4 - 1 ],按教材所述步骤操作 ,由于灼热铜丝在转移过程中温度很快降低 ,伸入到盛氯气的集气瓶中不易点燃 ,实验失败。若改用一根直径约为 2ｍｍ的铜丝 ,将其一端绕成螺旋状 ,灼热后在转移过程中温度降低较慢 ,伸入盛氯气的集气瓶容易点燃 ,现象明显。高一化学新教材Ｐ1 34[实验 6 - 4],按教材所述步骤操作 ,由于在搅拌过程中热量散失很快 ,不能提供足够热量使浓硫酸继续与碳反应产生气泡 ,导致黑色糊状物不能上胀 ,实验失败。若改为先滴浓硫酸 ,使其浸润迅速搅拌 ,再滴 3- 4滴蒸馏水 ,再搅拌均匀 ,过半分钟即可看…     

矿物选浮中颗粒与气泡黏附效率实验观测装置开发与教学应用

为促进浮选理论与实验教学的融合,设计了矿物颗粒与气泡碰撞、黏附实验观测装置并开发了视频数据可视化转换软件,用于观测颗粒与气泡的碰撞–黏附过程和行为,计算颗粒与气泡碰撞–黏附的过程参数和黏附效率,实现浮选理论微观知识的数据化和可视化.实验结果表明该装置结构合理、调节精准,可自动记录视频并进行数据分析.实验教学过程表明,该...     

Robust nonlinear control of continuous stirred tank reactors

１ＩｎｔｒｏｄｕｃｔｉｏｎＲｏｂｕｓｔｃｏｎｔｒｏｌｏｆｕｎｃｅｒｔａｉｎｓｙｓｔｅｍｓｉｓａｃｅｎｔｒａｌｉｓｓｕｅｉｎｃｏｎｔｒｏｌｔｈｅｏｒｙ．Ｉｎｔｈｅｐａｓｔｆｅｗｙｅａｒｓｍｕｃｈｉｎｔｅｒｅｓｔｈａｓｂｅｅｎｄｅｖｏｔｅｄｔｏｔｈｅｄｅ...     

Nonlinear model predictive control with guaranteed stability based on pseudolinear neural networks

~~identificationis7-7-1,where3nm==,andtheRPEalgorithmisusedtoupdatetheweightingofPNN.Thewholetrainingprocessuses800iterations.InordertoovercometheinaccuracyofPNNmodel,thecontrollerstructureisacompositeoneasfbff()()()ututut=+,(37)wherefb()utistheoutputoffeedbackcontroller,ff()utistheoutputofpredictivecontrollerdescribedbyEq.(14),with0.20=,0.40=,andmax5K=.Insimulatedclosedloopcontrol,ufb(t)isaproportionalcontroller,fb()()Putket=and5.0Pk=.Theset-pointofthesystemisd0.15,if040,and120()0.24,if4…     

Nonlinear model predictive control with guaraneed stability based on pesudolinear neural networks

A nonlinear model predictive control problem based on pseudo-linear neural network (PNN) is discussed, in which the second order on-line optimization method is adopted. The recursive computation of Jacobian matrix is investigated. The stability of the closed loop model predictive control system is analyzed based on Lyapunov theory to obtain the sufficient condition for the asymptotical stability of the neural predictive control system. A simulation was carried out for an exothermic first-order reaction in a continuous stirred tank reactor. It is demonstrated that the proposed control strategy is applicable to some of nonlinear systems.     

Absorption of NO2 into Na2S solution in a stirred tank reactor

To understand the absorption mechanism of nitrogen dioxide into a sodium sulfide solution, a stirred tank reactor with a plane gas-liquid interface was used to measure the chemical absorption rate of diluted nitrogen dioxide into sodium sulfide solution. The absorption rates under various experimental conditions were measured and the effects of experimental conditions on nitrogen dioxide absorption rate were discussed. The results show that, in the range of this study, nitrogen dioxide absorption rate increases with increasing sodium sulfide concentration, nitrogen dioxide inlet concentration, and flue gas flow rate, but decreases with increasing reaction temperature and oxygen content in flue gas.     

7-lump kinetic model for residual oil catalytic cracking

INTRODUCTION Residua catalytic cracking (RCC) is a process in which crude oil fractions are cracked into more valuable lighter products in a riser reactor with flu- idized catalyst. The complexity of charge stocks make it extremely infeasible to characterize and de- scribe at a molecular level, so attempts have been made to lump large numbers of chemical compounds into a kinetic species to describe the complex reac- tions in the process (Wei and Kuo, 1969; Kuo and Wei, 1969). Some early…     

坦克装甲车辆机动性虚拟仿真实验设计与实现

围绕坦克装甲车辆领域人才培养的需求,突出学科优势与专业特色,依托相关领域的科研和教学成果,基于Unity 3D开发了坦克装甲车辆机动性虚拟仿真实验。坦克装甲车辆机动性虚拟仿真该实验利用虚拟仿真手段重现了高仿真度的实验环境与测试过程,为学生提供了开放的实践条件,并支持学生独立自主地进行机动性实验研究与探索,为装甲车辆工程专业的虚实结合教学实践体系提供了重要支撑和补充完善。     

Statistical process monitoring based on improved principal component analysis and its application to chemical processes

In this paper, a novel criterion is proposed to determine the retained principal components (PCs) that capture the dominant variability of online monitored data. The variations of PCs were calculated according to their mean and covariance changes between the modeling sample and the online monitored data. The retained PCs containing dominant variations were selected and defined as correlative PCs (CPCs). The new Hotelling’s T ² statistic based on CPCs was then employed to monitor the process. Case studies on the simulated continuous stirred tank reactor and the well-known Tennessee Eastman process demonstrated the feasibility and effectiveness of the CPCs-based fault detection methods.     

油缸试验台自动采集系统设计

介绍了油缸试验台自动采集系统的设计与实现.该系统采用主从式结构,主机用于数据采集管理,从机是二次仪表(压力和温度采集)和单片机为核心的采集器,系统通过JC485芯片和RS232串口进行采集数据,完成主机和从机的数据通信,实现油缸试验台的压力和温度自动采集,完成油缸的出厂试验和型式试验.     

Absorption of NO2 into Na2S solution in a stirred tank reactor

To understand the absorption mechanism of nitrogen dioxide into a sodium sulfide solution, a stirred tank reactor with a plane gas-liquid interface was used to measure the chemical absorption rate of diluted nitrogen dioxide into sodium sulfide solution. The absorption rates under various experimental conditions were measured and the effects of experimental conditions on nitrogen dioxide absorption rate were discussed. The results show that, in the range of this study, nitrogen dioxide absorption rate increases with increasing sodium sulfide concentration, nitrogen dioxide inlet concentration, and flue gas flow rate, but decreases with increasing reaction temperature and oxygen content in flue gas.     

Two dimensional potential mapping-Monte Carlo simulation

A very useful experiment of two dimensional potential mapping, namely electrolytic tank model, for graduate and post graduate level physics students is given here. Laplace's equation is solved for the above and the results are compared with the experiment. The agreement is so good that this is extended to complex problems. Monte Carlo simulation, an alternative to the above experiment, is developed for these complex problems and compared with the experimental results of electrolytic tank model.