机油滤纸过滤阻力的实验与模拟研究

模拟分析滤纸过滤阻力与各影响因素的关系。根据模拟需要,对不同种常见机油滤纸进行了孔隙率、厚度、过滤阻力、含尘浓度和过滤速度等测试;并依据实验数据,分析得到了滤纸模拟模型,模拟边界条件。通过模拟得到了各影响因素变化时,滤纸过滤阻力随之变化的趋势,给出了滤纸过滤性能的模拟与实验对比结果,验证了模拟方法的可靠性,最后回归分析得到滤纸压降与含尘浓度、过滤速度及孔隙率的关系,为滤纸的优化选择及设计提供参考依据。     

旋流滤清器过滤速度研究

通过对旋流滤清器的过滤性能进行测试,得出质量流速随时间的变化规律,并采用量纲分析法根据实验测试结果,得出旋流滤清器过滤速度的数学统计模型,此模型可以指导旋流滤清器的结构设计。     

内循环三相生物流化床反应器中流体的循环速度

通过实验和CFD模拟研究了反应器内气含率和局部阻力系数与操作参数和结构参数的关系. 结果表明,气含率随进气速率Ugr增大而增大,局部阻力系数随反应器升、降流区截面积比Ar/Ad增大而减小,随导流筒直径与导流筒距反应器底高度之比d/h增大而增大,由此建立了升、降流区气含率和导流筒底端局部阻力系数关联式. 在此基础上,采用降流区流体速度模型,研究了局部阻力与沿程阻力对降流区速度的影响,并实验测试不同操作和结构条件下降流区的流体速度. 模型计算与实测速度对比分析表明,根据所建局部阻力系数关联式并考虑沿程阻力影响,可获得与实测结果吻合较好的降流区速度. Ugr取最大值2.29 m/s时,降流区流体速度最大可达0.32 m/s,且Ar/Ad取最大值1.61、d/h取最小值1.75时反应器中流体循环更好.     

一种中空纤维滤料过滤性能研究

为了解天然气净化中使用的中空纤维的过滤性能,采用均匀设计法~([1])实验,DPS数据回归处理方法~([2])分析结果,影响未覆膜滤料过滤性能的因素为:过滤速度含尘浓度过滤时间;对于覆膜滤料,过滤时间和含尘浓度影响极小,影响过滤性能的因素主要为过滤速度。采用CFD数值模拟对颗粒在滤料层内部的过滤细节进行分析,得出:中空纤维的内部结构对大颗粒的捕集影响较大;而对于细微颗粒,只能通过提高过滤精度来提增大收尘效率。     

组合式滤清器阻力特性研究

为考察由惯性级、网垫级组成的三级滤清器的阻力特性,采用了对三级滤清器进行整体数值模拟的研究方法。该方法改进了对惯性级、网垫级各级阻力叠加来获得组合滤清器的阻力特性的方法,能够较真实地反映流场的流动特性,为分析研究滤清器性能及优化设计提供合理的依据。通过实验获得的不同工况下三级滤清器的阻力特性曲线与数值模拟结果的对比验证了整体模拟方法的高精度。     

螺旋叶片转子强化传热机理分析

以螺旋叶片转子为研究对象,对转子的强化换热机理进行理论分析,提出螺旋叶片转子3种强化传热机理,包括截面收缩效应强化、螺旋流动效应强化以及二次流效应强化。采用理论推导的方法,建立湍流区内Nusselt数预测关联式以及压力降预测关联式,从而预测转子几何参数等对转子强化传热特性及阻力特性的影响。同时,将关联式预测结果与对应的强化传热实验结果进行对比,对比结果表明:推导得出的Nusselt数预测关联式计算值与实验得到的Nusselt数之间的最大偏差为7.4%,阻力系数的预测关联式计算值与其实验值之间的最大偏差为10.1%。     

变截面管管内实验研究及其关联式

根据正交实验设计提出了几种变截面管强化传热管的结构尺寸 ,并由实验结果回归得出了变截面管的传热和阻力关联式 ,经过管型的分析比较 ,筛选出性能较好的变截面管尺寸参数     

小孔筛板上清液层高度的测量与计算

通过对小孔筛板的流体力学实验研究给出了筛板上清液层高度的测量结果,实验在塔径为1.2m的冷模精馏塔中应用空气-水系统进行.利用实验数据对文献中用于计算筛板上清液层高度关联式中的拟合参数进行重新回归,通过比较得出能够更好地预测小孔筛板上清液层高度的关联式.     

换热管内置开边槽扭带的阻力及转动特性研究

将18种不同结构参数的铝制扭带分别置入换热管进行实验,研究并分析了换热管内置开三角形边槽扭带的阻力和转动特性。实验结果表明,插入开边槽扭带后管内的流动阻力和转动性能都有较大的提高,扭带的扭转比Y、扭带宽度D和边槽结构是影响压降和转速的主要因素。通过多元线性回归分析,得到了相应的压降Δp关联式和转速n关联式。实验表明,开边槽结构具有强化扭带转动特性的应用价值。     

折褶滤芯过滤阻力的数值模拟与分析

由于滤芯折褶结构过于微小,再加上温度和环境等因素的存在,运用试验测试这种方法来研究折褶滤芯的过滤阻力有一定弊端。采用CFD技术对过滤器进行数值模拟,观察流体在过滤器内腔中的水流现象,分析其通过滤网时的流动状态,找到了二维数值模拟方法误差大的原因,并采集十个折褶滤芯的样本点,拟合出理论计算与数值模拟的相对误差曲线。结果表明,对于折褶滤芯而言,采用三维数值模拟方法得出来的过滤阻力误差不到5%,这对滤芯的设计和选型具有指导意义。     

气体干法净化旋流吸附耦合设备压降特性

气体干法净化旋流吸附耦合设备将旋流分离和移动床吸附/过滤分离有机结合,可适应较宽的温度范围,为高温气体净化提供了一种新思路。在不加尘及不同的移动床循环速率和旋风入口气速下对该设备进出口静压差进行了测量和分析。实验结果表明,设备静压差在整个运行过程中较为稳定,有较强的可预测性,无量纲标准偏差维持在0.4%以内;实验范围内,移动床循环量的大小对设备静压差没有影响;设备压降与旋风入口气速呈现出良好的二次方程（抛物线）关系;将设备实际压降划分为进口管路沿程摩擦损失、入口天圆地方摩擦损失、旋流体摩擦损失、内置移动床摩擦损失和出口管路沿程摩擦损失五个部分;获得了旋流体摩擦损失及设备实际压降与入口速度头的关联方程;该设备的阻力系数与普通旋风分离器相比,没有明显增大;初步加尘实验确认了旋风壳体与移动床之间旋流作用的存在,为进一步结构优化提供了参考。     

Design Impact on Airflow Patterns in Fluidization Units

The airflow behavior in a fluidization unit was integrally studied by means of experimental work and computational fluid dynamics simulation. The computational domain included the gas inlet pipe, plenum, perforated plate, fluidization chamber, and air outlet pipe. Different scenarios were simulated to allow distinguishing the best way to represent perforated‐plate distributors and elucidate the impact of the grid design on the fluidization performance. The simulated pressure drop across the distributor and the plenum flow pattern were in concordance with the experimental data. It was found that the distance between the peripheral holes and walls has a great impact on the airflow downstream the distributor.     

金属丝网过滤器过滤初期阶段压力特性的研究

对5μm刚性金属丝网滤筒过滤初期阶段的压力特性,选用高密度聚乙烯粉料进行了实验研究,主要考察过滤速度和入口浓度对滤袋筒压降的影响。实验结果表明在过滤初期阶段滤筒的过滤压降上升趋势很明显,这种压降的增大主要来自于残余压降。滞留在滤筒内的粉尘改变了丝网内部的流道结构,从而导致了滤筒残余压降的不断升高。过滤速度和入口浓度的增加均可使残余压降增大。最后通过压降组成的分析,提出了滤筒总压降的计算模型。     

Experimental study of filter clogging with monodisperse PSL particles

A fibrous filter is a common cleaning device often used to remove particle from industrial gas streams. The main question that often arises concerns the evolution of the pressure drop and the filtration efficiency during the filter clogging. The increase of pressure drop and filter efficiency was measured and was linked to both the clogging degree inside the filter bed and the deposit structure observed thanks to scanning electron micrograph. We have also studied the influence of various parameters such as air velocity, particle size, aerosol concentration and filter main characteristics. An empirical equation for predicting the pressure drop across the filter as a function of inverse particle diameter and Cunningham correction factor was suggested without considering the particle density in the cellulose paper filter. The values of porosity, obtained from the pressure drop responses of loading in the paper filter using Rudnick and First equation, were compared with other researchers.     

Performance characteristics of air intake pleated panel filters for internal combustion engines in a two-stage configuration

Previous numerical studies that have used computational fluid dynamics (CFD) and experimental software to address the effects of the geometric parameters of pleats on the pressure drop and air flow rate through a fibrous filter are analyzed. The analysis establishes that using a test dust with gradually smaller particle sizes (10, 5, and 1?μm) results in a more intense increase in the filter pressure drop, thus decreasing the service life of the filter. The benefits of using a multicyclone as the first stage of air filtration are discussed. Selecting the air filter by determining the active surface of the filter medium A_c based on the allowable filtration rate is not sufficient; to select the filter medium of a motor vehicle air filter, the dust mass retained per unit of filtration area (mass loading of dust k_m) must be known for a specific allowable pressure drop Δp_fdop. New methods and conditions for determining the mass loading of dust k_m for filter paper and non-woven fabric in single-stage and two-stage filtration systems are presented. The characteristics of the separation efficiency and filtration performance as well as the pressure drop of a filter set comprising a single cyclone and a filter element with a specific filter medium surface are determined. The effects of the particle size distribution of the dust in the air downstream of the cyclone on the mass loading of dust k_m of the filter paper and non-woven fabric in a two-stage filtration system are presented. The mileage of a truck fitted with a single-stage or two-stage filtration system in a “multicyclone–panel filter” configuration is estimated based on the calculated mass loading of dust k_m of the filter paper and non-woven fabric.

© 2018 American Association for Aerosol Research     

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。     

高分子烧结刚性微孔管空气精密过滤

介绍了空气预过滤的重要性 ,测定了PA 6T微孔管过滤空气的效率和压力降 ,分析了影响过滤效率、压力降的因素。实验结果表明 ,PA 6T微孔管具有过滤效率高、压力降低、容尘量大等特点 ,适合于空气的精密过滤     

错流旋转填料床气相压降特性

旋转填料床的气相压降是旋转填料床应用和设计的一项重要指标。在气液两相错流流动条件下,利用空气-水系统对错流旋转填充床的气相压降进行分段模型化和实验研究。按照错流旋转填料床气体流动的路径将气相压降分为进口压降、填料层压降、集气段旋转动能转化压降和出气段压降。推导出压降与操作工况的关联式,其计算值与实测值吻合较好。实验表明错流旋转填料床的气相总压降与气体流量、旋转床转速、液体流量有关。在高转速和小气量的条件下,气相压降随气量增大先下降后上升;其他情况随气量增大而上升。错流旋转填料床气相压降随转速上升而下降,在小气量情况下转速对气相压降有明显影响。气相压降随进液量的增大而增大,当旋转填料床在低转速时进液量对气相压降有明显影响。     

气液两相流流过阀门局部阻力特性研究

以空气,水为工质,对进口和出口水平管内气相两相流流过闸阀的局部阻力特性进行了研究,管内直径38 mm、阀门通径4p mm.根据实验结果,总结出了空气和水两相流体流过闸阀时的局部阻力变化规律,并与前人的结果进行比较,提出了闸阀局部阻力修正系数,计算值和实验符合良好.     

Air flows and pressure drop modelling for different pleated industrial filters

A dimensionless model was developed to determine the pressure drop across clean pleated filters, according to filter medium type, geometric characteristics of the pleating (distance between two pleats, pleat height, etc) and air flow parameters (filtration velocity, air density, etc). The model was derived from both experimental and numerical results obtained from nuclear and automotive filters — high efficiency particulate air (HEPA) and low efficiency particulate (LE), respectively. The major findings were that a more homogeneous air flow distribution occured over the surface of the pleated HEPA filter, while geometric characteristics had a greater influence on the initial pressure drop across the LE filter. The numerical model highlighted the fundamental importance of the filter medium's air flow resistance on air flow distribution.