To simulate steady airflows inside of wall-flow diesel particulate filters （DPF） with different reverse blowing pipes collocation, a mathematical model of the flow in a DPF is established by an equivalent continuum ...To simulate steady airflows inside of wall-flow diesel particulate filters （DPF） with different reverse blowing pipes collocation, a mathematical model of the flow in a DPF is established by an equivalent continuum approach. The experimental results agree well with the theoretical values calculated from the model. Simulation shows that the velocity and the pressure distribution of the filters in the regenerative process are key factors to the filter＇s regeneration. How to decrease the mal-distribution of the flow in the filter and how to achieve the better regenerative performance at the least cost of air consumption in the regenerative process are the ultimate goals of the study. Calculation and experiments show that the goals can be realized through adjusting the angle of two reverse blowing pipes and their relative location suitably.展开更多
In this study,air filter base paper(P)was used as the receiving substrate,polyvinyl alcohol(PVA)and PVA/multi-walled carbon nanotube(MWCNT)spinning solutions were used to prepare electrospun air filter papers(P-PVA an...In this study,air filter base paper(P)was used as the receiving substrate,polyvinyl alcohol(PVA)and PVA/multi-walled carbon nanotube(MWCNT)spinning solutions were used to prepare electrospun air filter papers(P-PVA and P-PVA/MWCNT,respectively).Then,P-PVA/MWCNT was calendered under different pressures.The effect of MWCNTs on the surface performance of P-PVA/MWCNT was explored and the influence of calendering technology on their structure and filtration characteristics was analyzed.Electron scanning microscope observation showed that the PVA nanofibers on the surface of P-PVA/MWCNT had no beading,and MWCNTs weakened the surface electrostatic phenomenon and had a good micromorphology.During the calendering process,with an increase in pressure,the mean pore size and surface roughness of P-PVA/MWCNT decreased,the initial resistance increased,and the filtration efficiency changed slightly.展开更多
In this study, the three-dimensional physical model of pleated air filtration media was simplified to porous media model, and the calculation parameters of porous media were obtained based on experimental data. The mo...In this study, the three-dimensional physical model of pleated air filtration media was simplified to porous media model, and the calculation parameters of porous media were obtained based on experimental data. The model of V-shaped pleated air filter media is constructed, the height of the media pleat is 50 mm and the pleat thickness is 4 mm, the pleat angle is 3.7°. The Hertz-Mindlin contact model was modified by Johnson Kendall Roberts (JKR) adhesion contact model. The deposition process of particles in media was simulated based on computational fluid dynamics (CFD) theory and discrete element method (DEM). Results show that the CFD–DEM coupling method can be effectively applied to the macro research of pleated air filter media. The particles will form dust layer and dendrite structure on the fiber surface, and the dust layer will affect the subsequent air flow organization, and the dendrite structure will eventually form a “particle wall”. The formation of the “particle wall” will prevent the particles from moving further in the fluid domain, which makes area of pleated angle become the “low efficiency” part about the particle deposition. Compared with area of pleated angle, the particles are concentrated in the opening area and the middle area of the pleated to agglomerate and deposit.展开更多
Particulate matter(PM)pollution has become a serious problem worldwide and various kinds of nanofibrous filters aiming to solve the problem have been developed.It is urgent to remove PM from high-temperature pollution...Particulate matter(PM)pollution has become a serious problem worldwide and various kinds of nanofibrous filters aiming to solve the problem have been developed.It is urgent to remove PM from high-temperature pollution sources,such as industrial emissions,coal furnaces,and automobile exhaust gases.However,filtration at pollution sources remains challenging because most existing air filters are not resistant to high temperature.Herein,heat-resistant polyimide(PI)nanofibrous air filters are fabricated via a simple and scalable solution blow-spinning method.These air filters show excellent thermal stability at high temperature up to 420℃.They exhibit a filtration efficiency as high as 99.73%at ambient temperature and over 97%at 300℃.In addition,a field test shows that the filters remove>97%of PM from the car exhaust fumes.Hence,the blow-spun PI nanofibrous membranes combined with the facile preparation strategy have great potential in high temperature air filtration fields and other similar applications such as water purification and protein separation.展开更多
We developed a high-efficiency rotating triboelectric nanogenerator （R-TENG）- enhanced multi.layered antibacterial polyimide （PI） nanofiber air filters for removing ultrafine particulate matter （PM） from ambient...We developed a high-efficiency rotating triboelectric nanogenerator （R-TENG）- enhanced multi.layered antibacterial polyimide （PI） nanofiber air filters for removing ultrafine particulate matter （PM） from ambient atmosphere. Compared to single- layered PI nanofiber filters, the multilayered nanofiber filter can completely remove all of the particles with diameters larger than 0.54 ffm and shows enhanced removal efficiency for smaller PM particles. After connecting with a R-TENG, the removal efficiency of the filer for ultrafine partides is further enhanced. The highest removal efficiency for ultrafine particulate matter is 94.1% at the diameter of 53.3 nm and the average removal efficiency reached 89.9%. Despite an increase in the layer number, the thickness of each individual layer of the film decreased, and hence, the total pressure drop of the filter decreased instead of increasing. Moreover, the nanofiber film exhibited high antibacterial activity because of the addition of a small amount of silver nanoparticles. This technology with zero ozone release and low pressure drop is appropriate for cleaning air, haze treatment, and bacterial control.展开更多
As global air pollution becomes increasingly severe,various types of fibrous filters have been developed to improve air filter performance.However,fibrous filters have limitations such as high packing density that gen...As global air pollution becomes increasingly severe,various types of fibrous filters have been developed to improve air filter performance.However,fibrous filters have limitations such as high packing density that generally causes high-pressure drop and ultimately deterioration in the filtration efficiency.High-pressure particulate matter precipitators are limited in terms of scope for commercialization because they require high voltage supplies and ozone generators.In this study,we develop fibrous filters with enhanced durability and improved performance using metallized microfibers decorated with metal-organic-framework(MOF)nanocrystals.Not only does the efficiency of the developed filters remain at or above 97%for 0.50-1.5μm PMs but the durability also significantly increases.In addition,using the water purification ability of the MOF,we explore the dye degradation effect of the hybrid microfibers by immersing them into Rhodamine B aqueous solution.In such an experiment the Rhodamine B aqueous solution is completely purified by the presence of the hybrid microfibers under the UV irradiation.展开更多
The contribution of leakage in a baghouse filter （defined as a short circuit between the upstream and downstream sides of the filter） to the emission of fine particles is quantified in comparison to other dust emiss...The contribution of leakage in a baghouse filter （defined as a short circuit between the upstream and downstream sides of the filter） to the emission of fine particles is quantified in comparison to other dust emission sources, and the influence of key operating variables on overall system response is analyzed. The study was conducted on a well-maintained pilot-scale filter unit （9 bags of 500 g/m^2 calendered polyester needle felt; total surface area 4.2 m^2） operated in Ap-controlled mode over a range of pulsing intensities, with two types of test dust （one free-flowing and the other cohesive） at inlet concentrations of 10 and 30 g/m^3. Leaks included single holes between 0.5 and 4 mm diameter, intentionally placed in either the plenum plate or one of the filter bags, as well as seamlines from bag confectioning. Emissions were sep- arated by source into a transient contribution due to dust penetration through the filter bags after each cleaning pulse, and a continuous contribution from leaks. This separation was based on a novel method of data processing that relies on time-resolved concentration measurements with a specially calibrated optical particle counter. Tiny leaks on the order of 1 mm generated the same emission level as all the bags combined, and dominated continuous emissions. The equivalent leak cross section （leakage = media emission） was about 1 ppm of the total installed filter surface, independent of upstream dust concentra- tion. Leakage through open seamlines amounted to 75% of media emissions in case of free-flowing test dust. Leakage was restricted to aerodynamic diameters less than ~5 μm （roughly the PM2.s mass frac- tion）. For comparison, time-averaged mass penetration through conventional needle-felt media ranged from about 10^-5 to 10^-6, depending on cohesiveness of the particle material and pulse cleaning intensity, giving emission levels between about 0.02 and 0.2 mg/m^3 at the reference concentration of 10 R/m^2.展开更多
A novel atomic force microscope （AFM） for large samples to be measured in liquid is developed. An innovative laser beam tracking system is proposed to eliminate the tracking and feedback errors. The open probe desig...A novel atomic force microscope （AFM） for large samples to be measured in liquid is developed. An innovative laser beam tracking system is proposed to eliminate the tracking and feedback errors. The open probe design of the AFM makes the operation in liquid convenient and easy. A standard 1200-lines/mm grating and a sheet of filter paper axe imaged respectively in air and liquid to confirm its performance. The corrosion behavior of aluminum surface in 1-mol/L NaOH solution is further investigated by the AFM. Experimental results show that the system can realize wide range （20 × 20 （μm）） scanning for large samples both in air and liquid, while keeping nanometer order resolution in liquid by eliminating the tracking and feedback error.展开更多
基金This project is supported by National Hi-tech Research and DevelopmentProgram of China (863 Program, No.2003AA643010B).
文摘To simulate steady airflows inside of wall-flow diesel particulate filters （DPF） with different reverse blowing pipes collocation, a mathematical model of the flow in a DPF is established by an equivalent continuum approach. The experimental results agree well with the theoretical values calculated from the model. Simulation shows that the velocity and the pressure distribution of the filters in the regenerative process are key factors to the filter＇s regeneration. How to decrease the mal-distribution of the flow in the filter and how to achieve the better regenerative performance at the least cost of air consumption in the regenerative process are the ultimate goals of the study. Calculation and experiments show that the goals can be realized through adjusting the angle of two reverse blowing pipes and their relative location suitably.
文摘In this study,air filter base paper(P)was used as the receiving substrate,polyvinyl alcohol(PVA)and PVA/multi-walled carbon nanotube(MWCNT)spinning solutions were used to prepare electrospun air filter papers(P-PVA and P-PVA/MWCNT,respectively).Then,P-PVA/MWCNT was calendered under different pressures.The effect of MWCNTs on the surface performance of P-PVA/MWCNT was explored and the influence of calendering technology on their structure and filtration characteristics was analyzed.Electron scanning microscope observation showed that the PVA nanofibers on the surface of P-PVA/MWCNT had no beading,and MWCNTs weakened the surface electrostatic phenomenon and had a good micromorphology.During the calendering process,with an increase in pressure,the mean pore size and surface roughness of P-PVA/MWCNT decreased,the initial resistance increased,and the filtration efficiency changed slightly.
文摘In this study, the three-dimensional physical model of pleated air filtration media was simplified to porous media model, and the calculation parameters of porous media were obtained based on experimental data. The model of V-shaped pleated air filter media is constructed, the height of the media pleat is 50 mm and the pleat thickness is 4 mm, the pleat angle is 3.7°. The Hertz-Mindlin contact model was modified by Johnson Kendall Roberts (JKR) adhesion contact model. The deposition process of particles in media was simulated based on computational fluid dynamics (CFD) theory and discrete element method (DEM). Results show that the CFD–DEM coupling method can be effectively applied to the macro research of pleated air filter media. The particles will form dust layer and dendrite structure on the fiber surface, and the dust layer will affect the subsequent air flow organization, and the dendrite structure will eventually form a “particle wall”. The formation of the “particle wall” will prevent the particles from moving further in the fluid domain, which makes area of pleated angle become the “low efficiency” part about the particle deposition. Compared with area of pleated angle, the particles are concentrated in the opening area and the middle area of the pleated to agglomerate and deposit.
基金This study was supported by the National Natural Science Foundation of China(Nos.51788104 and 51661135025)the National Basic Research Program of China(No.2015CB932500)China Postdoctoral Science Foundation(Nos.2018M640124 and 2019T120083).
文摘Particulate matter(PM)pollution has become a serious problem worldwide and various kinds of nanofibrous filters aiming to solve the problem have been developed.It is urgent to remove PM from high-temperature pollution sources,such as industrial emissions,coal furnaces,and automobile exhaust gases.However,filtration at pollution sources remains challenging because most existing air filters are not resistant to high temperature.Herein,heat-resistant polyimide(PI)nanofibrous air filters are fabricated via a simple and scalable solution blow-spinning method.These air filters show excellent thermal stability at high temperature up to 420℃.They exhibit a filtration efficiency as high as 99.73%at ambient temperature and over 97%at 300℃.In addition,a field test shows that the filters remove>97%of PM from the car exhaust fumes.Hence,the blow-spun PI nanofibrous membranes combined with the facile preparation strategy have great potential in high temperature air filtration fields and other similar applications such as water purification and protein separation.
文摘We developed a high-efficiency rotating triboelectric nanogenerator （R-TENG）- enhanced multi.layered antibacterial polyimide （PI） nanofiber air filters for removing ultrafine particulate matter （PM） from ambient atmosphere. Compared to single- layered PI nanofiber filters, the multilayered nanofiber filter can completely remove all of the particles with diameters larger than 0.54 ffm and shows enhanced removal efficiency for smaller PM particles. After connecting with a R-TENG, the removal efficiency of the filer for ultrafine partides is further enhanced. The highest removal efficiency for ultrafine particulate matter is 94.1% at the diameter of 53.3 nm and the average removal efficiency reached 89.9%. Despite an increase in the layer number, the thickness of each individual layer of the film decreased, and hence, the total pressure drop of the filter decreased instead of increasing. Moreover, the nanofiber film exhibited high antibacterial activity because of the addition of a small amount of silver nanoparticles. This technology with zero ozone release and low pressure drop is appropriate for cleaning air, haze treatment, and bacterial control.
基金supported by The National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.NRF-2020R1A5A1018153)King Saud University,Riyadh,Saudi Arabia,for funding this work through Researchers Supporting Project number(RSP-2020/30)。
文摘As global air pollution becomes increasingly severe,various types of fibrous filters have been developed to improve air filter performance.However,fibrous filters have limitations such as high packing density that generally causes high-pressure drop and ultimately deterioration in the filtration efficiency.High-pressure particulate matter precipitators are limited in terms of scope for commercialization because they require high voltage supplies and ozone generators.In this study,we develop fibrous filters with enhanced durability and improved performance using metallized microfibers decorated with metal-organic-framework(MOF)nanocrystals.Not only does the efficiency of the developed filters remain at or above 97%for 0.50-1.5μm PMs but the durability also significantly increases.In addition,using the water purification ability of the MOF,we explore the dye degradation effect of the hybrid microfibers by immersing them into Rhodamine B aqueous solution.In such an experiment the Rhodamine B aqueous solution is completely purified by the presence of the hybrid microfibers under the UV irradiation.
文摘The contribution of leakage in a baghouse filter （defined as a short circuit between the upstream and downstream sides of the filter） to the emission of fine particles is quantified in comparison to other dust emission sources, and the influence of key operating variables on overall system response is analyzed. The study was conducted on a well-maintained pilot-scale filter unit （9 bags of 500 g/m^2 calendered polyester needle felt; total surface area 4.2 m^2） operated in Ap-controlled mode over a range of pulsing intensities, with two types of test dust （one free-flowing and the other cohesive） at inlet concentrations of 10 and 30 g/m^3. Leaks included single holes between 0.5 and 4 mm diameter, intentionally placed in either the plenum plate or one of the filter bags, as well as seamlines from bag confectioning. Emissions were sep- arated by source into a transient contribution due to dust penetration through the filter bags after each cleaning pulse, and a continuous contribution from leaks. This separation was based on a novel method of data processing that relies on time-resolved concentration measurements with a specially calibrated optical particle counter. Tiny leaks on the order of 1 mm generated the same emission level as all the bags combined, and dominated continuous emissions. The equivalent leak cross section （leakage = media emission） was about 1 ppm of the total installed filter surface, independent of upstream dust concentra- tion. Leakage through open seamlines amounted to 75% of media emissions in case of free-flowing test dust. Leakage was restricted to aerodynamic diameters less than ~5 μm （roughly the PM2.s mass frac- tion）. For comparison, time-averaged mass penetration through conventional needle-felt media ranged from about 10^-5 to 10^-6, depending on cohesiveness of the particle material and pulse cleaning intensity, giving emission levels between about 0.02 and 0.2 mg/m^3 at the reference concentration of 10 R/m^2.
基金supported in part by the National"863"Program of China (No.2006AA04Z237)the Open Subject of State Key Laboratory of Modern Optical Instruments (No.200705)
文摘A novel atomic force microscope （AFM） for large samples to be measured in liquid is developed. An innovative laser beam tracking system is proposed to eliminate the tracking and feedback errors. The open probe design of the AFM makes the operation in liquid convenient and easy. A standard 1200-lines/mm grating and a sheet of filter paper axe imaged respectively in air and liquid to confirm its performance. The corrosion behavior of aluminum surface in 1-mol/L NaOH solution is further investigated by the AFM. Experimental results show that the system can realize wide range （20 × 20 （μm）） scanning for large samples both in air and liquid, while keeping nanometer order resolution in liquid by eliminating the tracking and feedback error.
