scholarly journals Numerical modeling of fine particle fractal aggregates in turbulent flow

2015 ◽  
Vol 19 (4) ◽  
pp. 1189-1193
Author(s):  
Feifeng Cao ◽  
Zhanhong Wan ◽  
Minmin Wang ◽  
Zhenjiang You ◽  
Zongfu Ren
Keyword(s):  
Numerical Modeling ◽  
Turbulent Flow ◽  
Moment Method ◽  
Particle Transport ◽  
Fine Particle ◽  
Taylor Expansion ◽  
Fine Particles ◽  
Particle Dynamics ◽  
Fractal Aggregates

A method for prediction of fine particle transport in a turbulent flow is proposed, the interaction between particles and fluid is studied numerically, and fractal agglomerate of fine particles is analyzed using Taylor-expansion moment method. The paper provides a better understanding of fine particle dynamics in the evolved flows.

Method of Taylor Expansion Moment Incorporating Fractal Theories for Brownian Coagulation of Fine Particles

2012 ◽  
Vol 13 (7-8) ◽  
Author(s):  
Zhanhong Wan ◽  
Zhenjiang You ◽  
Zhilin Sun ◽  
Wenbin Yin
Keyword(s):  
Fractal Dimension ◽  
Moment Method ◽  
Taylor Expansion ◽  
Fine Particles ◽  
Second Order ◽  
New Method ◽  
Particle Removal ◽  
Brownian Coagulation ◽  
Combination Process ◽  
Laguerre Method

AbstractFine particles aggregating into larger units or flocculation body is a random combination process. Increasing the size and density of flocculation body is the main approach to rapid particle removal or sedimentation in water. Aiming at the Brownian coagulation of fine particles, a new method of Taylor expansion moment construction of fractal flocs has been developed in this paper, incorporating the Taylor expansion approach based on the moment method and the fractal dimension of the floc structure originated from fractal theories. This method successfully overcomes the limit of previous moment methods that require pre-assumed particle size distribution. Results of the zero and second order moments of Brownian flocs from the proposed method are compared with those from the Laguerre method, integral moment method and finite element method. It is found that the higher accuracy and efficiency of computation have been achieved by the new method, compared to the previous ones. Effects of the fractal dimension on the zero and second order moments, geometric average volume and standard deviation are also analyzed using this method. The self-conservation characteristics of particle distribution is observed without presumption of initial distributions.

scholarly journals Fractal aggregation and breakup of fine particles

2016 ◽  
Vol 20 (3) ◽  
pp. 797-801 ◽  
Author(s):  
Bingru Li ◽  
Feifeng Cao ◽  
Zhanhong Wan ◽  
Zhigang Feng ◽  
Honghao Zheng
Keyword(s):  
Fluid Dynamics ◽  
Moment Method ◽  
Taylor Expansion ◽  
Fine Particles ◽  
Size Distributions ◽  
Number Density ◽  
Dynamics Modeling ◽  
Particle Size Distributions ◽  
Particle Volume ◽  
Computational Fluid Dynamics Modeling

Breakup may exert a controlling influence on particle size distributions and particles either are fractured or are eroded particle-by-particle through shear. The shear-induced breakage of fine particles in turbulent conditions is investigated using Taylor-expansion moment method. Their equations have been derived in continuous form in terms of the number density function with particle volume. It suitable for future implementation in computational fluid dynamics modeling.

Application of Ceramic Membrane Technology in Tungsten Fine Particle Concentration Process

2014 ◽  
Vol 692 ◽  
pp. 191-199
Author(s):  
Wan Fu Huang ◽  
Xiao Feng Wang ◽  
Xin Dong Li ◽  
Si Ming Yan
Keyword(s):  
Fine Particle ◽  
Particle Concentration ◽  
Fine Particles ◽  
Ceramic Membrane ◽  
Membrane Technology ◽  
Factors Affecting ◽  
Membrane Flux ◽  
Concentration Test ◽  
Optimal Effect ◽  
Membrane Concentration

This study used ceramic membrane technology to concentrate tungsten fine particles for its inefficient recycling issue. Factors affecting the membrane concentration test were discussed, and the results show that: under the feed flow of 7000 mL/min, concentration time of 3 hours, and concentration liquid flow of 500 mL/min, it is the optimal effect of ceramic membrane concentration tungsten fine particle, which the interception rate reaches more than 99%, the membrane permeation flux can be nearly reach 470mL/(min×1099cm2) above, and concentrate concentration can be basically stable at around 29% . Ceramic membrane flux recovery rate can be as high as 93% by 7 minutes backwashing firstly and then 2 minutes forward cleaning.

scholarly journals Study of pressurised metered dose inhalers for the purpose of standardization of quality attributes characterizing uniformity of dosing

2021 ◽  
pp. 11-23
Author(s):  
Elena Bezuglaya ◽  
Nikolay Lyapunov ◽  
Vladimir Bovtenko ◽  
Igor Zinchenko ◽  
Yurij Stolper
Keyword(s):  
Particle Size ◽  
Fine Particle ◽  
Fine Particles ◽  
Average Dose ◽  
Metered Dose Inhalers ◽  
Fine Particle Dose ◽  
Particle Dose ◽  
Metered Dose ◽  
Delivered Dose

Aim. The purpose was to provide the rationale of test in regard to uniformity of fine particles dose for pressurised metered dose inhalers (pMDIs). Materials and methods. The pMDIs containing suspensions of salbutamol sulfate (SS) or solutions of beclometasone dipropionate (BD) were studied by laser diffraction and high performance liquid chromatography (HPLC). The particle size distribution of SS, the average dose mass and uniformity of dose mass, the average delivered dose and the uniformity of delivered dose, the average fine particles dose and uniformity of fine particles dose were determined. Apparatus A was used for assessment of fine particles dose. Results. The two analytical procedures for the quantitative determination of SS and BD by HPLC were validated in the ranges with low concentrations of these substances. The 5 medicinal products in pMDI dosage form were studied: 3 preparations were with SS and 2 ones contained BD. It was shown that three products with SS were very similar in regard to particle size distribution in containers and the average values of delivered dose were almost the same, but these products were different in the average dose mass and fine particle dose. According to the research results, the expediency of determining the average dose mass and the tests concerning uniformity of dosing of preparations by dose mass and by fine particle dose was substantiated. It was shown that in the case of pMDI the dosing of solutions of BD was more uniform compared to suspensions of SS. The approaches of leading and other pharmacopoeias concerning uniformity of dosing for pMDIs were critically discussed. The expediency of determination of uniformity of fine particle dose at the stage of pharmaceutical development was substantiated, as the therapeutic effect depends on fine particle dose. Issues concerning standardization pMDIs in regard to uniformity of fine particle dose were discussed. Conclusions. The expediency of standardization and quality control of pMDIs in regard to such attributes as the average dose mass, which characterizes the volume of the metering chamber of the valve as well as the uniformity of the dose mass and the uniformity of fine particle dose, which assure the therapeutic effect of each dose of the product was substantiated

scholarly journals Atmospheric oxidation capacity in Chinese megacities during photochemical polluted season: radical budget and secondary pollutants formation

2018 ◽  
Author(s):  
Zhaofeng Tan ◽  
Keding Lu ◽  
Meiqing Jiang ◽  
Rong Su ◽  
Hongli Wang ◽  
...  
Keyword(s):  
Fine Particle ◽  
Fine Particles ◽  
Nox Reduction ◽  
Ozone Production ◽  
Atmospheric Oxidation ◽  
Ozone Pollution ◽  
Oxidation Capacity ◽  
Radical Chemistry ◽  
Budget Analysis ◽  
Secondary Pollutants

Abstract. Atmospheric oxidation capacity is the core of converting fresh-emitted substances to secondary pollutants. In this study, we present the in-situ measurements at four Chinese megacities (Beijing, Shanghai, Guangzhou, and Chongqing) in China during photochemical polluted seasons. The atmospheric oxidation capacity is evaluated using an observational-based model with the input of radical chemistry precursor measurements. The radical budget analysis illustrates the importance of HONO and HCHO photolysis, which contribute nearly half of the total radical primary sources. The radical propagation is efficient due to abundant of NO in the urban environments. Hence, the production rate of secondary pollutants, i.e. ozone and fine particle precursors (H2SO4, HNO3, and ELVOCs) is fast resulting in secondary air pollution. The ozone budget demonstrates that strong ozone production occurs in the urban area which results in fast ozone concentration increase locally and further transported to downwind areas. On the other hand, the O3-NOx-VOC sensitivity tests show that ozone production is VOC-limited, among which alkenes and aromatics should be first mitigated for ozone pollution control in the presented four megacities. However, NOx emission control will lead to more server ozone pollution due to the drawback-effect of NOx reduction. For fine particle pollution, the role of HNO3−NO3− partitioning system is investigated with a thermal dynamic model (ISORROPIA2) due to the importance of particulate nitrate during photochemical polluted seasons. The strong nitrate acid production converts efficiently to nitrate particles due to high RH and ammonium-rich conditions during photochemical polluted seasons. This study highlights the efficient radical chemistry maintains the atmospheric oxidation capacity in Chinese megacities, which results in secondary pollutions characterized by ozone and fine particles.

scholarly journals Changes in Particle Size Composition under Seepage Conditions of Reclaimed Soil in Xinjiang, China

Processes ◽  
2018 ◽  
Vol 6 (10) ◽  
pp. 201 ◽  
Author(s):  
Zizhao Zhang ◽  
Wanghua Sui ◽  
Kaikai Wang ◽  
Guobin Tang ◽  
Xiaoping Li
Keyword(s):  
Particle Size ◽  
Fine Particle ◽  
Granulometric Composition ◽  
Fine Particles ◽  
Land Reclamation ◽  
Sharp Decrease ◽  
Size Composition ◽  
Particle Content ◽  
Reclaimed Soil ◽  
Different Depths

The distribution of reclaimed soil particle size under seepage conditions after the management period will directly determine the success or failure of reclamation work. The geotechnical experimental method was used in this paper to study the changes in the granulometric composition of soil. The results show that the granulometric composition of the reclaimed soil varied obviously at different depths. The granulometric composition of the soil at a depth of 10 cm was not much different from undisturbed reclaimed soil (URS). At a depth of 30 cm, as the sharp decrease of the content of fine particles resulted in coarser reclaimed soil, the soil became more uniform, with an increase in porosity and water content. At a depth of 50 cm, the fine particle content was generally slightly lower than that of URS. At a depth of 70 cm, the fine particle content of the soil greatly exceeded that of the URS, with the finest soil particles and lowest porosity. The main reason for the above-mentioned changes of granulometric composition in the reclaimed soil was the seepage in soil caused by irrigation during the management period. The research results can provide a reference for management after land reclamation at non-metallic mines in Xinjiang, China.

scholarly journals Evidence for Asian dust effects from aerosol plume measurements during INTEX-B 2006 near Whistler, BC

2009 ◽  
Vol 9 (11) ◽  
pp. 3523-3546 ◽  
Author(s):  
W. R. Leaitch ◽  
A. M. Macdonald ◽  
K. G. Anlauf ◽  
P. S. K. Liu ◽  
D. Toom-Sauntry ◽  
...  
Keyword(s):  
Organic Material ◽  
Fine Particle ◽  
Radiative Forcing ◽  
Fine Particles ◽  
Anthropogenic Sources ◽  
Dust Particles ◽  
Coarse Particles ◽  
Organic Mass ◽  
Ion Chemistry ◽  
Scanning Transmission

Abstract. Several cases of aerosol plumes resulting from trans-Pacific transport were observed between 2 km and 5.3 km at Whistler, BC from 22 April 2006 to 15 May 2006. The fine particle (<1 μm) chemical composition of most of the plumes was dominated by sulphate that ranged from 1–5 μg m−3 as measured with a Quadrapole Aerosol Mass Spectrometer (Q-AMS). Coarse particles (>1 μm) were enhanced in all sulphate plumes. Fine particle organic mass concentrations were relatively low in most plumes and were nominally anti-correlated with the increases in the number concentrations of coarse particles. The ion chemistry of coarse particles sampled at Whistler Peak was dominated by calcium, sodium, nitrate, sulphate and formate. Scanning transmission X-ray microscopy of coarse particles sampled from the NCAR C-130 aircraft relatively close to Whistler indicated carbonate, potassium and organic functional groups, in particular the carboxyl group. Asian plumes reaching Whistler, BC during the INTEX-B study were not only significantly reduced of fine particle organic material, but organic compounds were attached to coarse particles in significant quantities. Suspension of dust with deposited organic material and scavenging of organic materials by dust near anthropogenic sources are suggested, and if any secondary organic aerosol (SOA) was formed during transport from Asian source regions across the Pacific it was principally associated with the coarse particles. An average of profiles indicates that trans-Pacific transport between 2 and 5 km during this period increased ozone by about 10 ppbv and fine particle sulphate by 0.2–0.5 μg m−3. The mean sizes of the fine particles in the sulphate plumes were larger when dust particles were present and smaller when the fine particle organic mass concentration was larger and dust was absent. The coarse particles of dust act to accumulate sulphate, nitrate and organic material in larger particles, diminishing the role of these compounds in indirect radiative forcing, but potentially enhancing their roles in direct radiative forcing.

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