循环流化床气固传质实验研究

This study is devoted to gas-solid mass transfer behavior in heterogeneous two-phase flow. Experiments were carried out in a cold circulating fluidized bed of 3.0m in height and 72mm in diameter with naphthalene particles. Axial and radial distributions of sublimated naphthalene concentration in air were measured with an online concentration monitoring system HP GC-MS. Mass transfer coefficients were obtained under various operating condition, showing that heterogeneous flow structure strongly influences the axial and radial profiles of mass transfer coefficients. In the bottom dense region, mass transfer rate is high due to intensive dynamic behavior and higher relative slip velocity between gas and clusters. In the middle transition region and the upper diluter region, as a result of low mass transfer driving force and the influence of flow structure, mass transfer rate distribution becomes non-uniform. In conclusion, among the operating parameters influencing mass transfer coefficients, the superficial gas velocity is the most important factor and the solid circulation rate should be also taken into account.     

Prediction of Swelling Behavior of AT-Isopropylacrylamide Hydrogels in Aqueous Solution of Sodium Chloride

In this paper, a model is presented to correlate and predict the swelling behavior of hydrogels in aqueous solutions of electrolytes. The model is a combination of VERS-model, "phantom network" theory and "free-volume" contribution. The VERS-model is used to calculate Gibbs excess energy; "phantom network" theory to describe the elastic properties of polymer network, and "free-volume" contribution to account for additional difference in the size of the species. To test the model, a series of N-isopropylacrylamide based hydrogels are synthesized by free radical polymerization in oxygen-free, deionized water at 25℃ under nitrogen atmosphere. Then, the degree of swelling of all investigated gels as well as the partition of the solute between the gel phase and the surrounding coexisting liquid phase are measured in aqueous solution of sodium chloride. The model test demonstrates that the swelling behavior correlated and predicted by the model agrees with the experimental data within the experimental uncert     

N-异丙基丙烯酰胺凝胶在NaCl水溶液中溶胀行为的预测研究

In this paper, a model is presented to correlate and predict the swelling behavior of hydrogels in aqueous solutions of electrolytes. The model is a combination of VERS-model, “phantom network“ theory and “free-volume“ contribution. The VERS-model is used to calculate Gibbs excess energy; “phantom network“ theory to describe the elastic properties of polymer network, and “free-volume“ contribution to account for additional difference in the size of the species. To test the model, a series of N-isopropylacrylamide based hydrogels are synthesized by free radical polymerization in oxygen-free, deionized water at 25~C under nitrogen atmosphere. Then, the degree of swelling of all investigated gels as well as the partition of the solute between the gel phase and the surrounding coexisting liquid phase are measured in aqueous solution of sodium chloride. The model test demonstrates that the swelling behavior correlated and predicted by the model agrees with the experimental data within the experimental uncertainty. The phase transition appeared in the experiment, and the influences of the total mass fraction of polymerizable materials ξgel as well as the mole fraction of the crosslinking agent YCR on the swelling behavior of IPAAm-gels can also be predicted correctly. All these show the potential of such model for correlation and prediction of the swelling behavior of hydrogels in aqueous solutions of electrolytes.     

可持续的多功能纳米涂层的设计:一种目标驱动的多尺度系统论方法(英文)

Polymer nanocomposites have a great potential to be a dominant coating material in a wide range of applications in the automotive,aerospace,ship-making,construction,and pharmaceutical industries.However,how to realize design sustainability of this type of nanostructured materials and how to ensure the true optimality of the product quality and process performance in coating manufacturing remain as a mountaintop area.The major challenges arise from the intrinsic multiscale nature of the material-process-product system and the need to manipulate the high levels of complexity and uncertainty in design and manufacturing processes.In this work,the challenging objectives of sustainable design and manufacturing are simultaneously accomplished by resorting to multiscale systems theory and engineering sustainability principles.The principal idea is to achieve exceptional system performance through concurrent characterization and optimization of materials,product and associated manufacturing processes covering a wide range of length and time scales.Multiscale modeling and simulation techniques ranging from microscopic molecular modeling to classical continuum modeling are seamlessly coupled.The integration of different methods and theories at individual scales allows the quantitative prediction of macroscopic system performance from the fundamental molecular behavior.Furthermore,mathematically rigorous and methodologically viable approaches are pursued to achieve sustainability-goal-oriented design of material-process-product systems.The introduced methodology can greatly facilitate experimentalists in novel material invention and new knowledge discovery.At the same time,it can provide scientific guidance and reveal various new opportunities and effective strategies for achieving sustainable manufacturing.The methodological attractiveness will be fully demonstrated by a detailed case study on the design of thermoset nanocomposite coatings.     

通过数学规划方法设计具有混合结构的水回用网络

A new design method for a water-reusing network, with a hybrid structure, to reduce the complexity of the network and to minimize freshwater consumption, is proposed. The unique feature of the methodology proposed .in this article is to control the complexity of the water network by regulation of the control number in a water-reusing system. It combines the advantages of a conventional water-reusing network and a water-reusing net work with internal water mains. To illustrate the proposed method, a single contaminant system and a multiple contaminant system serve as examples of the problems.     

伴有生物质热解的流化床中的混沌传递现象

Experiments of biomass pyrolysis were carried out in a fiuidized bed, and dynamic signals of pressure and temperature were recorded. Correlation dimension was employed to characterize the chaotic behavior of pressure and temperature signals. Both pressure and temperature signals exhibit chaotic behavior, and the chaotic behavior of temperature signals is always weaker than that of pressure signals. Chaos transfer theory was advanced to explain the above phenomena. The discussion on the algorithm of the correlation dimension shows that the distance definition based on rhombic neighborhood is a better choice than the traditional one based on spherical neighborhood. The former provides a satisfactory result in a much shorter time.     

气固并流向上流动中颗粒聚集的机理

Two-dimensional unsteady cocurrent upward gas-solid flows in the vertical channel are simulated and the mechanisms of particles accumulation are analyzed according to the simulation results. The gaseous turbulent flow is simulated using the large eddy simulation （LES） method and the solid phase is treated using the Lagrangian approach, and the motion of the gas and particles are coupled. The formation of clusters and the accumulation of particles near the wall in dense gas-solid flows are demonstrated even if the particle-particle collisions were ignored. It is found that a cluster grows up by capturing the particles in the dilute phase due to its lower vertical velocity. By this way the small size clusters can evolve to large-scale clusters. Due to the interaction of gas and particles, the large-scale vortices appear in the channel and the boundary layer separates from the wall, which results in very high particle concentration in the near wall region and a very large-scale cluster formed near the separation point.     

染料残渣焚烧过程中微量元素的形态转化及其迁移分配的预测

The release of heavy metals from the combustion of hazardous wastes is an environmental issue of increasing concern. The species transformation characteristics of toxic heavy metals and their distribution are considered to be a complex problem of mechanism. The behavior of hazardous dyestuff residue is investigated in a tubular furnace under the general condition of hazardous waste pyrolysis and gasfication. Data interpretation has been aided by parallel theoretical study based on a thermodynamic equilibrium model based on the principle of Gibbs free energy minimization. The results show that Ni, Zn, Mn, and Cr are more enriched in dyestuff residue incineration than other heavy metals （Hg, As, and Se） subjected to volatilization. The thermodynamic model calculation is used for explaining the experiment data at 800℃ and analyzing species transformation of heavy metals. These results of species transformation are used to predict the distribution and emission characteristics of trace elements. Although most trace element predictions are validated by the measurements, cautions are in order due to the complexity of incineration systems.     

A CFD model for predicting the heat transfer in the industrial scale packed bed

Compared to the traditional lumped-parameter model,computational fluid dynamics (CFD) attracted more attentions due to facilitating more accurate reactor design and optimization methods when analyzing the heat transfer in the industrial packed bed.Here,a model was developed based on the CFD theory,in which the heterogeneous fluid flow was resolved by considering the oscillatory behavior of voidage and the effective fluid viscosity.The energy transports in packed bed were calculated by the convection and diffusion incorporated with gaseous dispersion in fluid and the contacting thermal conductivity of packed particles in solids.The heat transfer coefficient between fluid and wall was evaluated by considering the turbulence due to the packed particles adjacent to the wall.Thus,the heat transfer in packed bed can be predicted without using any adjustable semi-empirical effective thermal conductivity coefficient.The experimental results from the literature were employed to validate this model.     

Using hot-vapor bypass for pressure control in distillation columns

Distillation column control is widely explored in literature due to its complexity and importance in chemical and petrochemical industries.In this process,pressure represents one of the most important variables to be controlled.However,there are few studies about how pressure affects the dynamic behavior of distillation columns and most research on distillation column control involve direct manipulation of cooling fluid through the condenser.Nevertheless,such an approach demands constant changes in cooling fluid flowrates that are commonly by the order of tons per hour,which can be difficult to work or even unfeasible in a real plant.Furthermore,this strategy is usually avoided,as it can cause fouling and corrosion acceleration.The hot-vapor bypass strategy fits well as a solution for these issues,eliminating the need to dynamically manipulate cooling fluid flowrates in the condensation unit.This work presents the modeling and simulation of a conventional distillation column for the separation of water and ethanol,in which a comparative study between a conventional pressure control and a control using hot-vapor bypass was performed.The main results were obtained through dynamic simulations which considered various disturbances in the feed stream,and demonstrated superior performance by the hot-vapor bypass system over the usual scheme proposed in literature,while evaluating the Integral Absolute Error (IAE) norm as the control performance index.     

支承松动的转子-滚动轴承系统的分岔与混沌

根据转子动力学、非线性动力学及Hertz理论,建立了带有一端支座松动故障的滚动轴承—转子系统的非线性动力学模型。通过数值积分和Poincare映射方法对其非线性动力学行为进行了数值仿真研究,给出了系统响应随转子转动频率变化的分岔图和一些典型的轴心轨迹图及Poincarc截面图,并分析了转动频率对转子系统动力学行为的影响。结论表明,转子在滚动轴承和支承松动这两种非线性因素作用下,具有周期运动、拟周期运动、混沌运动和倍周期分岔等复杂的动力学行为。     

Flow dynamics in a four-inch downer using solids concentration measurements

Local solids concentration fluctuations were measured in a long downer reactor (0.1 m ID, 9.3 m tall) using an optical fiber probe. Axial flow development and radial flow dynamics were analyzed using both statistical and chaos methods. Core, transition and annulus regions were identified and each region showed different flow behavior. Cross-sectional averaged chaos parameters were correlated to cross-sectional averaged solids holdup to develop relationships between non-linear flow dynamics and operating conditions.     

气固流化床压力脉动信号的混沌特征分析

对气固流化床内压力脉动时间序列进行分析,研究了流化床内的混沌特性,分别利用李雅普诺夫指数、相对分散度、分形维数和混沌度来定量描述稳定性、复杂性,自由度和系统状态数,证明四个混沌特征参数的相关性是好的,得到了混沌特性随着气速和床层高度的变化趋势,并且提出气泡行为是流化床内产生混沌运动的重要原因。     

双组分层撞击流反应器浓度场混沌分析

采用平面激光诱导荧光技术测量双组分层式撞击流反应器撞击区浓度分布,利用混沌理论分析不同喷嘴间距、喷嘴直径和射流雷诺数下撞击流反应器浓度场混沌特征参数(关联维、Kolmogorov熵和最大Lyapunov指数)的变化规律。结果表明,撞击流反应器内浓度场混沌特征参数随喷嘴间距的增大呈上下波动的变化趋势,Kolmogorov熵在L=2d时达到最大。浓度场混沌特征参数随喷嘴直径增大呈上下波动的变化趋势,Kolmogorov熵在d=8 mm时整体上最大;射流雷诺数为Re=22 000时整体上混沌特征参数最佳。受二次撞击区的影响,撞击面上靠近二次撞击区各点的混沌特征参数有明显提高。     

混沌理论及其在流态化技术中的应用

概述了非线性系统中的混沌理论及其在流化领域的应用及进展。与其它方法比较 ,说明混沌理论在化工设计、放大、控制方面将是一有力的工具。     

Chaotic Analysis of the Concentration Field in a Submerged Impinging Stream Mixer

The concentration field was measured with various nozzle diameters, nozzle distances, and inlet flow rates in a submerged impinging stream mixer (SISM) using planar laser‐induced fluorescence to obtain characteristic parameters such as correlation dimension, Kolmogorov entropy, and Lyapunov exponents that describe the chaos phenomenon and reflect the microcosmic mixture effect of a SISM by mean of the chaos theory. The chaotic characteristic parameters were influenced significantly by different nozzles distances, nozzle diameters, and inlet flow rates and their distributions followed a similar changing regularity by which all parameters decreased with larger nozzle diameter and increased with higher inlet flow rate.     

开放系统中多步化学反应的混沌及控制

为了更好地控制化学系统中的混沌,以Willamowski-R(o)ssler模型所对应的量纲一动力演化方程为研究对象,进行了复杂动力学特征分析,包括相轨迹图、Lyapunov指数和庞加莱映射图,这些特征都表明该三维动力系统含有混沌吸引子,同时也加深了对系统中复杂行为的认识.以LaSalle恒定性原理为基础,通过线性变换...     

基于混沌理论的电化学噪声谱数据解析及其在局部腐蚀检测中的应用

将混沌理论引入电化学噪声（EN）谱的数据解析,对有机涂层失效过程和应力腐蚀过程的EN数据进行分析,采用关联维数表征局部腐蚀过程,取得了一些有意义的结果。分析了环氧酚醛/镀锡薄钢板失效过程的EN特征,通过计算涂覆镀锡薄钢板腐蚀过程的电化学电位噪声（EPN）谱特征,发现EPN对应的关联维数值随着局部腐蚀程度的加剧有增加的趋势。采用混沌相空间重构理论分析了304不锈钢应力腐蚀过程的电流噪声谱,利用关联维数表征应力腐蚀过程。数据计算结果表明应力腐蚀初期其相空间轨迹呈圆球形,应力腐蚀后期则变为椭圆形。研究结果表明,当裂纹萌生和扩展时,关联维数值增大,表明电化学噪声信号的不确定性与复杂性增加。     

An analysis of pressure drop fluctuation in a circulating fluidized bed

The characteristics of pressure drop fluctuation in a 5.0 cm I.D.×250cm high circulating fluidized bed with fine polymer particles of PE and PVC were investigated. The measurements of time series of the pressure drop were carried out along the three different axial locations. To determine the effects of coarse particles and relative humidity of air on the flow behavior of polymer powders-air suspension in the riser, we employed deterministic chaos analysis of the Hurst exponent, correlation dimension and phase space trajectories as well as classical methods such as standard deviation, probability density function of pressure drop fluctuation. From a statistical and chaos analysis of pressure fluctuations, the upper dilute region was found to be much more homogenous flow compared to that in the bottom dense region at the same operating conditions. It was also found that the addition of coarse particles and higher humidity of air reduced the pressure fluctuations, thus enhancing flow stability in the riser. The analysis of pressure fluctuations by statistical and chaos theory gave qualitative and the quantitative information of flow behavior in the circulating fluidized bed.     

循环流化床颗粒浓度波动信号多重分形测度分析

由于循环流化床气－固两相流动规律相当复杂，使得至今对其流动规律的认知仍不足以直接用于循环流床的工业设计与放大。近十多年来，确定性混沌理论已被用于循环流化床动力学特性的研究，与其密切相关的分形理论也被用于流化床流动特性的研究。然而，这些研究所用均是采用单分形理论，而单分形理论对解释循环流化床复杂的非线性气－固流动行为显得能力不足。为了探讨循环流化床内颗粒流体系统非线性、非均匀性和混沌特性机理。本文引入不同测试多重分形分析的方法，用小波变换模极大值与多重分形测度分析方法相结合，检测循环流化床颗粒浓度波动信号奇异性并得出多重分形奇异谱。结果表明循环流化床颗粒浓度波动信号具有明显的多重分形特性。小波变换多重分形方法可以用来描述床内颗粒流动特性，为探讨循环流化床颗粒流体系统非均匀机制提出了一种新的方法。