Particle motion and separation in a laminar tube flow with downstream enlargement

Particle classification becomes difficult when the difference in density between particle and fluid is low or negligible and the fluid is viscous. For such applications, a process capable of separating the particles according to their size is needed. Such applications are, e.g. found in biological systems for cell separation or in the removal of gel particles from polymer melts. Particle transport in laminar tube flows at low but non zero Reynolds numbers leads to accumulation of large particles near the tube center and forms a particle free zone near the wall. Small particles find their position on their equilibrium radius. Downstream widening of the flow enhances segregation between large and small particles. Large particles can be collected in a centered collector tube downstream, whereas small particles follow their streamlines around the collector tube and can be removed with the remaining flow. The said particle migration is observed when the ratio of particle to tube diameter is 0.2<d/D<0.51 and the tube Reynolds number is in between 0.2<Re<40. CFD simulations reveal the shape of the streamlines in the downstream enlargement with different tube Reynolds number. The efficiency of the classification process is characterized. Particles need a sufficient transportation length in the tube for proper demixing. This effect is analyzed by a laser sheet illuminated system within an acrylic glass tube.     

催化裂化装置反应再生工段动态仿真培训系统

以安庆石化总厂炼油厂催化装置反应再生过程为具体对象 ,根据反应机理和现场操作数据 ,建立了系统的动态数学模型 ,开发了仿真培训系统并成功地应用于操作工人的培训。同时 ,介绍了系统的功能、仿真数学模型及应用效果     

箭竹1井胶凝酸酸压返排液处理及回注技术

胶凝酸主要由盐酸和胶凝剂配制而成,在低渗透碳酸盐岩地层压裂时,盐酸溶蚀地层,沟通缝隙。胶凝酸与地层岩石的化学反应在2小时内完成,返排液中的残酸用以NaOH为主的碱中和剂处理,通过中和、沉降、过滤、杀菌等一系列处理后回注地层。     

页岩气措施返排液重复利用技术研究

页岩气主要通过采用大规模减阻水多级分段压裂获得。减阻水压裂会产生大量的返排液,返排液若直接排放会对周边的生态环境造成一定的影响,必须对其进行有效处理。如果能够实现对返排液中减阻水压裂液的重复利用,就可减少对环境的污染、降低开采成本、节约水资源,研究其处理方法具有极大的技术价值和经济价值。根据页岩气措施液性能要求,在仔细分析返排液性质的基础上,评选出絮凝剂、杀菌剂等水处理药剂,筛选出适合返排液重复利用的减阻剂,在焦页8-2HF和焦页12-3HF井应用中取得较好的效果。     

复杂环形输气管网内的瞬变流

本文依据复杂管道内气体不稳定流动(瞬变流)的概括性方程,结合生产实际条件,首先提出单环管网和双环并联管网的数学模型,应用拉普拉斯变换方法,经过一系列的数学演算过程,最后得出描述环形输气管网内气体瞬变流的规律之数学表达式,为了得到实际上的应用,再将这些数学表达式进行一系列运算,转变成易于用计算机进行计算的公式;然后编制出计算程序;最后给出实例,打印出计算结果;并绘制了管网内压力随时间和管长的变化曲线。     

The mechanical behaviour of coal with respect to CO2 sequestration in deep coal seams

Carbon dioxide displays a strong affinity for coal due to its propensity to adsorb to the coal surface. The process of CO₂ adsorption on coal causes lowering of surface energy and, it is hypothesised that an associated decrease in surface film confinement results in a decrease in material tensile resistance. Following the results of work carried out on the mechanical influence of CO₂ on brown coal under in situ conditions [Viete DR, Ranjith PG. The effect of CO₂ on the geomechanical and permeability behaviour of brown coal: implications for coal seam CO₂ sequestration. Int J Coal Geol 2006;66(3):204–16], a theoretical explanation is proposed for the perceived lack of a weakening effect with the adsorption of CO₂ to coal at significant confining pressures. We propose that at significant hydrostatic stresses, resistance to failure is otherwise provided (by external confinement) and the effects of adsorptive weakening are concealed. Our model predicts that adsorptive weakening, fracturing under in situ stresses, and associated permeability increases are not an issue for coal seam CO₂ sequestration for sufficiently deep target seams. Lowering of the elastic modulus of coal upon introduction of CO₂ may proceed by means other than surface energy lowering and could well occur irrespective of the depth of sequestration. The effect of elastic modulus lowering under in situ conditions would be beneficial for the long-term retention of sequestered gases.     

不同材料界面边缘的应力奇异场

利用构造的应力函数,根据不同材料界面边缘的连接条件及自由边界条件求得了这类问题的应力奇异场.结果表明:不同材料界面边缘的应力奇异性与两种材料的材料常数有关,也与界面边缘的角度有关。     

Studying Fluid Characteristics Atop Surface Patterned Membranes via Particle Image Velocimetry

Surface patterning is a recent promising approach to promote performance of pressure-driven membranes in water treatment and desalination. Nevertheless, knowledge about foulant deposition mechanisms, especially at early stage of filtration, is still lacking. The applicability of particle imaging velocimetry to study fluid characteristics atop surface patterned thin-film composite membranes was investigated at different operating conditions. This work is an important first step toward reliable understanding of the impacts of topographical membrane surface modification on hydrodynamic conditions and foulant deposition mechanisms.     

Application of the Electrodiffusion Method to Measure Wall Shear Stress: Integrating Theory and Practice

The electrodiffusion method has been used in fluid dynamic research for the past 50 years. It allows the measurement of wall shear stress, a crucial parameter, e.g., for the cleaning of membrane modules used in water filtration. Various authors have published articles dealing with the theory behind this technique. But no paper collects all the knowledge assembled over five decades of application. Here, comprehensive summary of the theory of steady flow, unsteady flow, and transient voltage step experiments is given. Factors influencing the accuracy of the measurements are discussed. Furthermore, a new approach to calibrate the system from voltage step experiments is introduced, and practical issues related to its application in flow measurements are discussed for an exemplary signal response to a near‐wall flow.