Scalable Numerical Tools for Flow and Pressure Drop Computation in Fibrous Filter Media

The prediction of flow behavior and pressure drop in fibrous filter media is challenging due to the complexity of the nonuniform fiber structure. Numerical calculation tools can considerably contribute to pressure drop determination for inhomogeneous filter structures. A numerical solution approach based on the finite element method to simulate 2D and 3D filter structures is considered. As numerical examples, computer designed homogeneous and inhomogeneous 2D cases where the numerical approach is validated by analytical models are investigated. Furthermore, the capability of the numerical method to simulate real 3D structures corresponding to more than 25 million degrees of freedom of the related algebraic system is demonstrated. The large systems involved require the use of dedicated techniques related to high performance computing.     

Evolution of the Efficiency and Pressure Drop of a Filter Media with Loading

A model for calculating the filtration efficiency and the pressure drop of a fiber filter media in dynamic regime was used and modified to take account of both the fiber and the particle size distributions. Measurements were carried out on two medias employed in industry and two loading aerosols to test the possibilities offered by the model to predict the evolution of both the efficiency and pressure drop characteristics. The results show that the model satisfactorily reflects the variations in efficiency and pressure drop of a media with respect to the loading if its structure is homogeneous and if the deposit of particles takes place within the thickness of the filtering layer. On the other hand, the divergence between the model and practical experience becomes significant as soon as surface filtration regime occurs or when the media has a heterogeneous structure. A test rig was developed to determine the filtering characteristics, such as fractional efficiency and pressure drop in relation to the degree of loading, from aerosols of various particle sizes. This study has highlighted the necessity of taking into account the influence of loading in the methods for testing filters, especially those used in the industry, and demonstrates that the particle size of the test aerosol is a very sensitive parameter.     

喷射泵式气、液反应器的流型及其转变规律

本文研究了喷射泵式气、液反应器的四种流型及其转变规律.基于动量原理及能量、质量守恒定律,导得了判定反应器正常工作流型的判别式.实验验证了这种判别式.     

纤维过滤介质过滤压力损失理论计算

为便于计算纤维过滤介质过滤压力损失,对目前各种纤维过滤介质过滤压力损失理论计算公式及半经验公式进行分析计算,将理论计算结果与实验测试结果进行对比分析发现各种理论计算结果普遍相偏大,需要对纤维的非均匀分布进行修正,修正后的大部分计算结果与实验结果基本吻合,同时对理论计算公式的鲁棒性进行了分析。计算结果准确性和鲁棒性兼顾的理论计算公式,较适宜于实际过滤材料压力损失的预测。     

气液两相鼓泡塔流区及其过渡的混沌分析

应用确定性混饨分析技术,以气液两相鼓泡塔内的压力波动时间序列为分析对象,系统研究了鼓泡塔系统的混饨特性．结果表明,鼓泡塔内气液两相流动系统为混饨动力学系统,混饨特征参数最大Ｌｙａｐｕｎｏｖ指数、Ｋｏｌｍｏｇｏｒｏｖ熵和关联维数Ｄ２等可以有效地表征鼓泡塔的流区及其过渡．混沌分析为定量判别鼓泡塔的流区及其过渡提供了新途径．操作条件对鼓泡塔内气液两相流动的混沌特性影响显著,表现为混沌特征参数值随表观气速增加而增加,随表观液速增加而减小,但是,混沌特性随空间位置的变化不显著．     

Pressure Drop and Interception Efficiency of Multifiber Filters

ABSTRACT

The viscous flow fields around multifiber filters have been investigated in a previous paper. The results of the previous work show that the flow becomes periodic immediately after the first fiber array downstream from the entrance if the fibers are arranged uniformly along the flow direction. The characteristics of such flow fields enable the pressure drop and the particle interception efficiency of a multifiber filter to be represented by single-fiber models. The total filtration efficiency, however, cannot be so represented since fibers interact during filtration processes. In this study, the pressure drop and the interception efficiency were investigated by making use of the viscous flow fields modeled in the previous research. The fiber separation ratio was found to have significant effects on pressure drop and efficiency. At a given volume fraction, changes in the fiber separation ratio will result in changes to the patterns of fluid flow and aerosol particle motion. Therefore, the fiber separation ratio significantly affects pressure drop and interception efficiency.     

漏斗-立管系统悬料区的压降计算方法

对于Ｇｅｌｄａｒｔ－Ｄ类颗粒在负压差漏斗－立管系统的悬料操作区的压降可以通过郭慕孙提出的气固移动床的公式求得。计算所得的压降大小与实验结果相比较误差在２０％的范围内;并且证明悬料区的总压降可以近似等于立管的压降。     

防积料型高效低阻预热器的开发研究

在综合多种预热器结构特点的基础上，开发了一种具有较理想的分离效率，很低的压力损失，并且能够防止进口段积料的新型预热风筒，有极好的应用前景。     

气固两相流压降探讨计算

人类很早就开始利用运动的空气(即风力)来驱动物体,如风车舂米磨面,风帆船运输等。随着科学技术和工业的发展,尤其是工业革命以来,用流动气体来输送固体得到了广泛的应用。18世纪末和19世纪初出现了管道的气力输送,20世纪初,在美国、俄罗斯、德国和欧洲许多国家气力输送邮件得到普遍的应用。对于气体输送固体的工艺要求越来越高,尤其是工艺设备和流程的选取、设计以及系统的操作管理的可靠性。     

粗颗粒在负压差漏斗-立管系统悬料区特性

负压差漏斗－立管系统是化工设备中常见的系统。在本文中主要研究了Ｇｅｌｄａｒｔ－Ｄ类物产在此系统中悬料区的特征。实验结果表明：立管底部孔口大小对于悬料萄下限有影响,而对上限无影响;相反,漏斗中的物料高度、漏半的锥度、立管长度和立管直径对悬料区的操作有很大的影响。本文根据实验结果给出了悬料区上、下限的条件。     

填料塔气液并流接触时压降的研究

以内径72 mm的玻璃吸收塔为主体,分别采用Mellapack-250X型金属孔板波纹规整填料以及Dg16塑料阶梯环散堆填料作为传质媒介。以水-SO2作为研究体系,结合气液逆流接触吸收试验对比分析气液并流接触时填料层压降的情况,并分别考察了气相动能因子F和液气比L/V对填料吸收塔气液并流接触时填料层压降的影响。填料层压降随着气相动能因子F的增大呈指数型增长,随着液气比的增加而升高,并流操作时的影响相对逆流操作时变化幅度较小。通过试验结果拟合出相应压降的关联式,为进一步的工艺设计与优化提供相关依据与理论指导。     

非牛顿流体流经弯管时的压降研究

Experimental data on the pressure drop across different types of elbow for non-Newtonian pseudoplastic liquid flow in laminar condition have been presented. A generalized correlation has been developed for predicting the frictional pressure drop across the elbows in the horizontal plane.     

Filtration Efficiency and Pressure Drop of Miniature Diesel Particulate Filters

A method was developed to evaluate miniature diesel particulate filters (DPFs). To validate the performance of the instrumentation and test apparatus, measurements were made using silicon carbide (SiC) and cordierite miniature filters with representative microstructures. Filtration efficiency (FE), the most penetrating particle size (MPPS), and pressure drop were measured for catalyzed and uncatalyzed advanced ceramic material (ACM) acicular mullite and representative commercial filters to determine the impact of substrate morphology, the formation of a soot cake, and the presence of a catalyst coating on filtration properties. FE measurements demonstrated that filter geometry and microstructure significantly influence initial filtration performance. ACM filters had high initial FE and the MPPS near ～200 nm. Reduction of the ACM pore size in the absence of a reduction in porosity increased initial FE even more, but its influence on MPPS was not resolvable. The presence of a catalyst and washcoat on the ACM increased the pressure drop but increased initial FE and reduced MPPS to <100 nm. The addition of a washcoat allowed the rapid buildup of a soot cake, which resulted in a more rapid rate of increase in FE compared to uncatalyzed ACM. The similarity in the ACM and cordierite soot cakes after a long loading time is consistent with theory that suggests the formation of the soot cake depends primarily on the Péclet (Pe) number, which is influenced only by macroscopic filter geometry and prevailing test conditions.

Copyright 2013 American Association for Aerosol Research     

滴流床反应器中泡沫流床层压降的实验研究

选用过氧化氢生产用蒽醌工作液体系,完成了滴流床反应器中泡沫流床层压降的实验研究. 通过测定瞬时床层压降,建立了反应器内的流型识别方法,借以研究了在泡沫流和泡沫脉冲流区的床层压降梯度与气液相流速、填料尺寸的关系,并采用Specchia和Baldi提出的经验式对发泡体系泡沫流区床层压降进行了估算. 结果表明,通过实验数据回归,可采用Specchia和Baldi经验式预测泡沫流区的床层压降,最大偏差小于5%.     

除油型水力旋流分离器压降研究

采用各向异性k ε模型,用有限差分法,以SIMPLE算法为基础对旋流器内流场进行了数值模拟,通过数值计算得到了液液水力旋流分离器溢流管直径对压力降的影响、压降与流量的关系。通过算例与实验校验,得出各向异性κ ε模型能够模拟旋流器内湍流流场。     

微通道中两相流压降与传质的研究

以氮气和水为实验体系,采用均质混合模型,研究微混合器的微通道中两相流通过微通道的压降,并测定了两相流的传质系数.结果表明,微通道当量直径为95.2 μm,气体速率为1.089～4.355 m/s,液体速率为0.006 41～0.170 90 m/s的条件下,均质混合模型计算压降值与实测值吻合良好.气速为1.633～3.484 m/s,液速为0.025 6 m/s时,随着气速增加,传质系数呈递增的趋势.气速为1.633～3.484 m/s,液速为0.019 2 m/s时,随着气速增加,传质系数先增加后降低然后再增加.传质系数对液速变化更为敏感.     

预测气液分层流含气率及压降的模型

The time-dependent liquid film thickness and pressure drop were measured by using parMlel-wire conductance probes and capacitance differential-pressure transducers. Applying the eddy viscosity theory and an appropriate correlation of interfacial sear stress,a new two-dimensional separated model of holdup and pressure drop of turbulent/turbulent gas-liquid stratified flow was presented. Prediction results agreed well with experimental data.     

微通道内液液两相流压力降的测量和关联

微通道内液液两相流的压力降对系统内部热量和质量传递具有重要影响。针对环己烷-含0.3%SDS(十二烷基硫酸钠)蒸馏水液液两相系统,利用高速摄像仪对2种不同深宽比的矩形截面直管微通道内的液液两相流进行了实时观测和记录,用压差变送器测定了其在弹状流型下的压力降。微通道尺寸(深度×宽度)分别为400μm×600μm,400μm×800μm。结果表明:弹状流型下的压力降随系统各相流率、毛细数、雷诺数、连续相黏度的增加而增加,随两相速度比值的增加而减小,且当毛细数Ca>0.015或雷诺数Re>20时,压力降随着通道截面深宽比的增加而增加。基于实验结果,修正了均相流模型,提出了新的压力降预测关联式,模型计算结果与实验值吻合良好。