The effects of continuously regenerating diesel particulate filter （CRDPF） systems on regulated gaseous emissions, and number-size distribution and mass of particles emanated from a diesel engine have been investiga...The effects of continuously regenerating diesel particulate filter （CRDPF） systems on regulated gaseous emissions, and number-size distribution and mass of particles emanated from a diesel engine have been investigated in this study. Two CRDPF units （CRDPF-1 and CRDPF-2） with different specifications were separately retrofitted to the engine running with European steady-state cycle （ESC）. An electrical low pressure impactor （ELPI） was used for particle number-size distribution measurement and mass estimation. The conversion/reduction rate （RcR） of hydrocarbons （HC） and carbon monoxide （CO） across CRDPF-1 was 83% and 96.3%, respectively. Similarly, the RCR of HC and CO and across CRDPF-2 was 91.8% and 99.1%, respectively. The number concentration of particles and their concentration peaks; nuclei mode, accumulation mode and total particles; and particle mass were highly reduced with the CRDPF units. The nuclei mode particles at downstream of CRDPF-1 and CRDPF-2 decreased by 99.9% to 100% and 97.8% to 99.8% respectively; and the particle mass reduced by 73% to 92.2% and 35.3% to 72.4%, respectively, depending on the engine conditions. In addition, nuclei mode particles increased with the increasing of engine speed due to the heterogeneous nucleation initiated by the higher exhaust temperature, while accumulation mode particles were higher at higher loads due to the decrease in the air-to-fuel ratio （A/F） at higher loads.展开更多
Taking wall-flow diesel particulate filter(DPF) as the research objective and separately assuming its filtering wall to be composed of numerous spherical or cylindrical elements, two different mathematical models of s...Taking wall-flow diesel particulate filter(DPF) as the research objective and separately assuming its filtering wall to be composed of numerous spherical or cylindrical elements, two different mathematical models of steady filtration for wall-flow diesel particulate filter were developed and verified by experiments as well as numerically solved. Furthermore, the effects of the macroand micro-structural parameters of filtering wall and exhaust-flow characteristic parameters on trapping efficiency were also analyzed and researched. The results show that: 1) The two developed mathematical models are consistent with the prediction of variation of particulate size; the influence of various factors on the steady trapping efficiency is exactly the same. Compared to model 2, model 1 is more suitable for describing the steady filtration process of wall-flow diesel particulate filter; 2)The major influencing factors on steady trapping efficiency of wall-flow diesel particulate filter are the macro-and micro-structural parameters of filtering wall; and the secondary influencing factors are the exhaust-flow characteristic parameters and macro-structural parameters of filter; 3)The steady trapping efficiency will be improved by increasing filter body volume, pore density as well as wall thickness and by decreasing exhaust-flow, but effects will be weakened when particulate size exceeds a certain critical value; 4) The steady trapping efficiency will be significantly improved by increasing exhaust-flow temperature and filtering wall thickness, but effects will be also weakened when particulate size exceeds a certain critical value; 5) The steady trapping efficiency will approximately linearly increase with reducing porosity, micropore aperture and pore width.展开更多
A three-dimensional diesel particulate filter(DPF)simulation model was developed by using AVL software FIRE to study the effects of four factors on soot particle distributions along the axial and radial directions in ...A three-dimensional diesel particulate filter(DPF)simulation model was developed by using AVL software FIRE to study the effects of four factors on soot particle distributions along the axial and radial directions in the DPF after the model accuracy was validated.An orthogonal test method was used to determine the importance and weights of the design of experiments(DoE)factors such as the expanding angle,the number of channels per square inch,and the exhaust mass flow rate.The effects of these factors on the uniformity of the soot particle distributions were also analyzed.The results show that when the soot loading time was 400 s,the soot particles inside the DPF along the axial direction exhibited a bowl shape,which was high on the both ends and low in the middle.The uniformity of the axial distribution of soot particles reduces significantly with an increase in the number of channels per square inch.The uniformity of the radial distribution reduced with an increase in the expanding angle of the divergent tube.Based on the impacts on the axial uniformity,the three most influencing factors in a descending order are the number of channels per square inch,the exhaust mass flow rate,and the expanding angle of the divergent tube.展开更多
The Mn-Ce-Nb-O_x/P84 catalytic filter for removal of particulates and NO simultaneous was prepared by a novel method(foam coating method). The process parameters including the concentrations of PTFE emulsion, particle...The Mn-Ce-Nb-O_x/P84 catalytic filter for removal of particulates and NO simultaneous was prepared by a novel method(foam coating method). The process parameters including the concentrations of PTFE emulsion, particle size of catalyst and calcination temperature for preparation of catalytic filters were analyzed. In addition, the physical properties and performance for removal of NO(NH_3-SCR) and particulates of Mn-Ce-Nb-O_x/P84 catalytic filter prepared under the optimized parameters, were also systematic studied. Results show that the process parameters had significant influences on stability and performance of catalytic filter, The Mn-Ce-Nb-O_x/P84 catalytic filter prepared by foam coating method under the optimized parameters, has satisfactory physical properties and catalytic performance for removal of NO and particulates at 140-220 ℃. The NO removal efficiency of catalytic filter can reach95.3% at 200 ℃ as the catalyst loading amount is 450 g/m^2, Moreover,the dust removal efficiency of MnGe-Nb-O_x/P84 catalytic filter reaches as high as 99.98%, and the PM2.5 removal efficiency also reaches99.98%. The anti-sulfur performance of Mn-Ce-Nb-O_x catalytic filter is also attractive, after injecting150 ppm SO_2, the NO removal efficiency still retains up to 85%. It is indicated that the foam coating method can not only make a bond of high strength between catalyst and filter, but also make the catalytic filter possessing an excellent and stable performance for removal of NO and particulates.展开更多
This study investigated the filtration and continuous regeneration of a particulate filter system on an engine test bench, consisting of a diesel oxidation catalyst（DOC） and a catalyzed diesel particulate filter（C...This study investigated the filtration and continuous regeneration of a particulate filter system on an engine test bench, consisting of a diesel oxidation catalyst（DOC） and a catalyzed diesel particulate filter（CDPF）. Both the DOC and the CDPF led to a high conversion of NO to NO2 for continuous regeneration. The filtration efficiency on solid particle number（SPN） was close to100%. The post-CDPF particles were mainly in accumulation mode. The downstream SPN was sensitively influenced by the variation of the soot loading. This phenomenon provides a method for determining the balance point temperature by measuring the trend of SPN concentration.展开更多
A new dual-layer granular bed filter for hot gas cleanup was invented and studied experimentally. Fine sand,0.5-1 mm grain size and about 1350 kg/m3 bulk density,was used as the lower layer of the filter. Expanded per...A new dual-layer granular bed filter for hot gas cleanup was invented and studied experimentally. Fine sand,0.5-1 mm grain size and about 1350 kg/m3 bulk density,was used as the lower layer of the filter. Expanded perlite par-ticles,2-5 mm grain size and about 70 kg/m3 bulk density,was used for the upper layer of the filter in this study. It was confirmed that the sizes and densities of these two media matched well; the binary media remained in complete segre-gation during regeneration by fluidization. Test results show that the filtration of the expanded perlite particle layer was characterized as "deep bed filtration." Filtration of the fine sand layer was "surface cake filtration." The expanded per-lite particle layer contributed about 90% to the bed dust capacity,but only about 20% to the total bed pressure drop,which increased the bed dust capacity ten fold compared to a single-layer bed of the same sand and the same total bed pressure drop. The dust cake on the surface of the fine sand layer raised the collection efficiencies to over 99.99%.展开更多
Diesel powered vehicles,in compliance with the more strict exhaust emission standards such as Euro V,is likely to require a diesel particulate filter(DPF).A DPF used on a vehicle will affect the acoustic emission of t...Diesel powered vehicles,in compliance with the more strict exhaust emission standards such as Euro V,is likely to require a diesel particulate filter(DPF).A DPF used on a vehicle will affect the acoustic emission of the diesel engine,so it is important to investigate the sound propagation rule in DPF and further to propose the optimum DPF design.However,due to the geometrical complexity of the DPF,the traditional analysis method,such as analytical method,can not assess the acoustic performance of DPF accurately in medium and high frequency band.In this paper,a combined approach of finite element analysis and viscosity correction is proposed to predict acoustic performance of DPF.A simplified model of the full DPF is established and is used to analyze the sound propagation characteristic of the DPF.The distribution of the sound pressure and velocity,the transmission matrix of the DPF are obtained using the finite element method.In addition,the method of the viscosity correction is used in the transmission matrix of the DPF to evaluate the acoustic performance of DPF.Based on the FEM computation and the viscosity correction,the transmission losses under the rated load and idle condition of a diesel engine are calculated.The calculation results show that DPF can effectively attenuate exhaust noise,and sound attenuation increase with the rise of the frequency.Sound attenuation is better under rated condition than idle condition of diesel engine,particularly in frequency above 1000 Hz.展开更多
Numerical simulation has been carried out to investigate the major factors affecting the time of composite regeneration due to coupling cerium-based additive and microwave for diesel particulate f3ilter(DPF). Effect o...Numerical simulation has been carried out to investigate the major factors affecting the time of composite regeneration due to coupling cerium-based additive and microwave for diesel particulate f3ilter(DPF). Effect on the composite regeneration time from various factors such as mass flow rate of exhaust gas, temperature of exhaust gas, oxygen concentration of exhaust gas, microwave power and amount of cerium-based additive are investigated. And a mathematical model based on fuzzy least squares support vector machines has been developed to forecast the endpoint of the composite regeneration. The results show that the relative error of endpoint forecasting model of composite regeneration is less than 3.5%, and the oxygen concentration of exhaust gas has the biggest effect on the endpoint of composite regeneration, followed by the mass flow rate of exhaust gas, the microwave power, the temperature of exhaust gas and the amount of cerium-based additive.展开更多
Diesel vehicles are responsible for most of the traffic-related nitrogen oxide（NO x） emissions,including nitric oxide（NO） and nitrogen dioxide（NO2）. The use of after-treatment devices increases the risk of high ...Diesel vehicles are responsible for most of the traffic-related nitrogen oxide（NO x） emissions,including nitric oxide（NO） and nitrogen dioxide（NO2）. The use of after-treatment devices increases the risk of high NO2/NO x emissions from diesel engines. In order to investigate the factors influencing NO2/NO x emissions, an emission experiment was carried out on a high pressure common-rail, turbocharged diesel engine with a catalytic diesel particulate filter（CDPF）. NO2 was measured by a non-dispersive ultraviolet analyzer with raw exhaust sampling. The experimental results show that the NO2/NO x ratios downstream of the CDPF range around 20%–83%, which are significantly higher than those upstream of the CDPF. The exhaust temperature is a decisive factor influencing the NO2/NO x emissions. The maximum NO2/NO x emission appears at the exhaust temperature of 350°C. The space velocity,engine-out PM/NO x ratio（mass based） and CO conversion ratio are secondary factors. At a constant exhaust temperature, the NO2/NO x emissions decreased with increasing space velocity and engine-out PM/NO x ratio. When the CO conversion ratios range from 80% to 90%,the NO2/NO x emissions remain at a high level.展开更多
In this study, the effects of a diesel oxidation catalyst(DOC) coupled with a catalyzed diesel particulate filter(CDPF) with different catalyst loadings on the power, fuel consumption,gaseous and particulate emissions...In this study, the effects of a diesel oxidation catalyst(DOC) coupled with a catalyzed diesel particulate filter(CDPF) with different catalyst loadings on the power, fuel consumption,gaseous and particulate emissions from a non-road diesel engine were investigated. Results showed that the after-treatment had a negligible effect on the power and fuel consumption.The reduction effect of the DOC on the CO and hydrocarbon(HC) increased with the engine load. Further reductions occurred coupling with the CDPF. Increasing the catalyst loading resulted in a more significant reduction in the HC emissions than CO emissions. The DOC could increase the NO_(2)proportion to 37.9%, and more NO_(2)was produced when coupled with the CDPF below 250℃;above 250℃, more NO_(2)was consumed. The after-treatment could reduce more than 99% of the particle number(PN) and 98% of the particle mass(PM).Further reductions in the PN and PM occurred with a higher CDPF catalyst loading. The DOC had a better reduction effect on the nucleation particles than the accumulation ones, but the trend reversed with the CDPF. The DOC shifted the particle size distribution(PSD) to larger particles with an accumulation particle proportion increasing from 13% to 20%, and the geometric mean diameter(GMD) increased from 18.2 to 26.0 nm. The trend reversed with the CDPF and the accumulation particle proportion declined to less than 10%. A lower catalyst loading on the CDPF led to a higher proportion of nucleation particles and a smaller GMD.展开更多
To compensate for the shortcomings of the thermal and catalytic regeneration of the diesel particulate filter(DPF),a self-designed packed-bed dielectric barrier discharge(DBD)reactor for DPF regeneration was developed...To compensate for the shortcomings of the thermal and catalytic regeneration of the diesel particulate filter(DPF),a self-designed packed-bed dielectric barrier discharge(DBD)reactor for DPF regeneration was developed.The DBD reactor with the main active substance of nonthermal plasma(NTP)as the target parameter was optimized by adjusting the feed gas,packing particles(material or size),and cooling water temperature.Moreover,a set of optimal working parameters(gas source,O_2;packing particles,1.2–1.4 mm ZrO_(2);and cooling water temperature,20℃)was selected to evaluate the effect of different O_(3) concentrations on DPF regeneration.The research results showed that selecting packing particles with high dielectric constant and large particles,as well as reducing the cooling water temperature,with oxygen as the feed gas,contributed to an increase in O_(3) concentration.During DPF regeneration,the following changes were observed:the power of the NTP reactor decreased to lower than 100 W,the O_(3) concentration increased from 15 g m^(-3) to 45 g m^(-3),the CO and CO_2 volume fractions of the particulate matter decomposition products increased,and the peak regeneration temperature increased to 173.4℃.The peak temperature arrival time was 60 min earlier,indicating that the regeneration rate of DPF increased with the increase in O_(3) concentration.However,the O_(3) utilization rate(the amount of carbon deposit removed per unit volume O_(3))initially increased and then decreased;when the O_(3) concentration was set to 25 g m^(-3),the highest O_(3) utilization rate was reached.The packed-bed DBD technology contributed to the increase in the concentration of NTP active substances and the regeneration efficiency of DPF.It provides a theoretical and experimental basis for high-efficiency regeneration of DPF at low temperatures(<200℃).展开更多
In order to reveal the mechanics of composite regeneration by coupling cerium-based additive and microwave for a diesel particulate filter, a composite regeneration model by coupling cerium-based additive and microwav...In order to reveal the mechanics of composite regeneration by coupling cerium-based additive and microwave for a diesel particulate filter, a composite regeneration model by coupling cerium-based additive and microwave for a diesel particulate filter was established based on field synergy theory. Performance evaluation on field synergy and composite regeneration of the diesel particulate filter was conducted by using the vortex crushing combustion and field synergy mathematical models. The results show that the peak temperature of the particulate filter body reaches 1180-1190 K when the regeneration time is 175 s, and there are optimal coordination degree between the velocity vector and temperature gradient of the filter body and the maximum ratio0.56-0.60 of the best burning regeneration region is obtained. Accordingly, the largest regeneration combustion rate inside the particulate filter body and the highest regeneration efficiency at the moment are achieved.展开更多
The next-generation Euro 7 standard proposed much lower pollutant limits from gasoline vehicles,specifically for CO and NO_(x),which would be challenging for the three-way catalysts(TWCs)utilized commercially to elimi...The next-generation Euro 7 standard proposed much lower pollutant limits from gasoline vehicles,specifically for CO and NO_(x),which would be challenging for the three-way catalysts(TWCs)utilized commercially to eliminate these pollutants.TWCs with reductive(Rh)and oxidative(Pd)active components on gasoline particulate filters(TWC on GPF)play importantly auxiliary roles in the remediation of CO and NO_(x)downstream the close coupled TWCs to meet their emission targets.Here,a low-content Rh-based TWC(0.17 wt%)zoned with a less expensive Pd-based TWC(0.29 wt%)for GPF applications(cGPF)is reported using improved colloidal deposition method.The supporting of Rh on Y-stabilized ZrO_(2)rather than on CeO_(2)-ZrO_(2)inhibits the formation of inactive Ce rhodate species,while Pd on CeO_(2)-ZrO_(2)not only guarantees the high oxygen storage capacity(OSC)but also enhances catalytic activity.The layout of the front one-fifth in volume being 0.29 wt%Pd on Ce_(0.43)Zr_(0.5)7O_(2)and the rear four-fifths being 0.17 wt%Rh on Zr_(0.85)Y_(0.15)O_(2)prevents the possible alloying of Rh with Pd.The highly effective zoned Rh and Pd TWCs show synergistic three-way activity before and after severe hydrothermal aging at 1000℃with 10%water for24 h,which could be potential choices for close coupled GPF application to satisfy the upcoming stringent emission standards,such as Euro 7 and China 6b.展开更多
An experimental system of diesel particulate filter(DPF)regeneration using non-thermal plasma(NTP)technology assisted by exhaust waste heat was conducted and regeneration experiments of DPFs with different amounts of ...An experimental system of diesel particulate filter(DPF)regeneration using non-thermal plasma(NTP)technology assisted by exhaust waste heat was conducted and regeneration experiments of DPFs with different amounts of trapped particulate matter(PM)were conducted.The concentrations of the PM decomposition products(CO,)and the internal temperature of the DPF were monitored to determine the performance of DPF regeneration and thermal safety of the NTP technology.The results showed that the concentrations of CO and CO2and the mass of P.V1 decomposition increased with the increase in the amount of captured PM,whereas the concentration of the NTP active substance(O,)escaping from the DPF decreased under the same working conditions of the NTP injection system.A higher amount of captured PM promoted the oxidative decomposition reaction between NTP and PM and improved the utilization rate of the NTP active substances.The peak temperature at the same measuring point inside the DPF generally increased and the phases of the peak temperature were delayed as the amount of captured PM increased.The temperature peaks and temperature gradients during the DPF regeneration process were far lower than llie failure limit value,which indicates that NTP regeneration technology has good thermal durability and increases the service life of the DPF.展开更多
Airborne particulate matter(PM),especially PM2.5,can be easily adsorbed by human respiratory system.Their roles in carrying pathogens for spreading epidemic diseases has attracted great concern.Herein,we developed a n...Airborne particulate matter(PM),especially PM2.5,can be easily adsorbed by human respiratory system.Their roles in carrying pathogens for spreading epidemic diseases has attracted great concern.Herein,we developed a novel gelatin filter-based and culture-independent method for investigation of the microbial diversity in PM samples during a haze episode in Tianjin,China.This method involves particle capture by gelatin filters,filter dissolution for DNA extraction,and high-throughput sequencing for analysis of the microbial diversity.A total of 584 operational taxonomic units(OTUs)of bacteria and 370 OTUs of fungi at the genus level were identified during hazy days.The results showed that both bacterial and fungal diversities could be evaluated by this method.This study provides a convenient strategy for investigation of microbial biodiversity in haze,facilitating accurate evaluation of airborne epidemic diseases.展开更多
Numerical simulations are performed both for the single airflow and air-PMtwo-phase flow in wall flow diesel participate filters (DPF) for the first time. The calculationdomain is divided into two regions. In. the inl...Numerical simulations are performed both for the single airflow and air-PMtwo-phase flow in wall flow diesel participate filters (DPF) for the first time. The calculationdomain is divided into two regions. In. the inlet and outlet flow channels, the simulations areperformed for the steady and laminar flow; In the porous filtration walls, the calculation model forflow in porous media is used. The Lagrange two-phase flow model is used to calculate the air-PMflow in DPF, for the dispersed phase (PM), its flow tracks are obtained by the integrating of theLagrange kinetic equation. The calculated velocity, pressure distribution and PM flow tracks in DPFare obtained, which exhibits the main flow characteristics in wall flow DPF and will be help for theoptimal design and performance prediction of wall flow DPF.展开更多
Diesel particulate filter (DPF) is an important factor which influences the sound from exhaust system of an engine. In order to understand the propagation law of sound wave and predict the insertion loss in DPF, based...Diesel particulate filter (DPF) is an important factor which influences the sound from exhaust system of an engine. In order to understand the propagation law of sound wave and predict the insertion loss in DPF, based on the general aero-dynamic equations and Darcy′s law, an acoustic property calculation model of DPF is constructed. Propagation and attenuation characteristics of the forward and backward propagating acoustic waves in the close and open pipe of the filter are investigated. The theoretical model is combined with experiment to investigate sound attenuation property of DPF. The insertion loss obtained from the experiment is compared with that computed for a DPF. The results from the experiment and theoretical calculation agree well.展开更多
In this study,the effect of new and used catalyzed diesel particulate filter(CDPF)with different catalyst loadings on the particulate emissions including the particle mass(PM),particle number(PN),particle size distrib...In this study,the effect of new and used catalyzed diesel particulate filter(CDPF)with different catalyst loadings on the particulate emissions including the particle mass(PM),particle number(PN),particle size distribution(PSD)and geometric mean diameter(GMD)from a diesel vehicle were investigated based on a heavy chassis dynamometer.Results showed that more than 97.9%of the PN and 95.4%of the PM were reduced by the CDPF,and the reduction efficiency was enhanced by the catalyst loading.After using the CDPF,the PSD transformed from bimodal to trimodal with the peak shifting towards smaller particle size,more nucleation mode particles were reduced compared with accumulation mode ones,but the reduction effect on the accumulation mode particles was more significantly influenced by the catalyst loading.Notably,the CDPF increased the accumulation mode particles proportion,producing a larger GMD.For the used CDPF,its reduction effect on the particulate emissions enhanced,especially for the PM in accumulation mode.The PSD returned to bimodal,but the peak at accumulation mode began to be higher than that at nucleation mode,illustrating that more nucleation mode particles was removed.The aging of the CDPF resulted in greater effect on the PN-based PSD than that of PM-based PSD,but the effect of catalyst loading on the PN and PM emission factors was weakened.The used CDPF further increased the GMD,and the effect of catalyst loading on the GMD was strengthened,a higher catalyst loading led to a reduction in the GMD.展开更多
Diesel particulate filter(DPF)is a leading technology reducing particle emissions from marine diesel engines.The removal or regeneration of soot in DPF is an important issue.The purpose of this study is to provide som...Diesel particulate filter(DPF)is a leading technology reducing particle emissions from marine diesel engines.The removal or regeneration of soot in DPF is an important issue.The purpose of this study is to provide some reference strategies to design the DPF for marine diesel engines.In this paper,a mathematical model of a marine DPF was built up and the particle trap process and the regeneration dynamics were simulated.The results show that the cake soot mass concentrations from 0 to 4.2 g/L during the trap process increase linearly with the increase of the exhaust gas flows while the depth soot mass concentrations from 0 to 2.2 g/L firstly increase linearly and then keep constant.Soot is mainly concentrated in the front and rear portion of the filter and less soot is in the middle.The soot distribution in the cake and depth layers shows the unevenness during the trap and regeneration process.The initial soot loadings have great effects on pressure drops and soot mass concentrations before regeneration,but the little effect after regeneration.The exhaust gas temperature heated to 850 K can achieve 94%efficiency for the DPF regeneration.The heating rate has no effects on the pressure drops and soot mass concentrations,but the heating duration time of exhaust gas has an important impact on them.展开更多
基金supported by the National Natural Science Foundation of China (No. 40805053)
文摘The effects of continuously regenerating diesel particulate filter （CRDPF） systems on regulated gaseous emissions, and number-size distribution and mass of particles emanated from a diesel engine have been investigated in this study. Two CRDPF units （CRDPF-1 and CRDPF-2） with different specifications were separately retrofitted to the engine running with European steady-state cycle （ESC）. An electrical low pressure impactor （ELPI） was used for particle number-size distribution measurement and mass estimation. The conversion/reduction rate （RcR） of hydrocarbons （HC） and carbon monoxide （CO） across CRDPF-1 was 83% and 96.3%, respectively. Similarly, the RCR of HC and CO and across CRDPF-2 was 91.8% and 99.1%, respectively. The number concentration of particles and their concentration peaks; nuclei mode, accumulation mode and total particles; and particle mass were highly reduced with the CRDPF units. The nuclei mode particles at downstream of CRDPF-1 and CRDPF-2 decreased by 99.9% to 100% and 97.8% to 99.8% respectively; and the particle mass reduced by 73% to 92.2% and 35.3% to 72.4%, respectively, depending on the engine conditions. In addition, nuclei mode particles increased with the increasing of engine speed due to the heterogeneous nucleation initiated by the higher exhaust temperature, while accumulation mode particles were higher at higher loads due to the decrease in the air-to-fuel ratio （A/F） at higher loads.
基金Projects(5117604551276056)supported by the National Natural Science Foundation of China+1 种基金Projects(201208430262201306130031)supported by the National Studying Abroad Foundation of the China Scholarship Council
文摘Taking wall-flow diesel particulate filter(DPF) as the research objective and separately assuming its filtering wall to be composed of numerous spherical or cylindrical elements, two different mathematical models of steady filtration for wall-flow diesel particulate filter were developed and verified by experiments as well as numerically solved. Furthermore, the effects of the macroand micro-structural parameters of filtering wall and exhaust-flow characteristic parameters on trapping efficiency were also analyzed and researched. The results show that: 1) The two developed mathematical models are consistent with the prediction of variation of particulate size; the influence of various factors on the steady trapping efficiency is exactly the same. Compared to model 2, model 1 is more suitable for describing the steady filtration process of wall-flow diesel particulate filter; 2)The major influencing factors on steady trapping efficiency of wall-flow diesel particulate filter are the macro-and micro-structural parameters of filtering wall; and the secondary influencing factors are the exhaust-flow characteristic parameters and macro-structural parameters of filter; 3)The steady trapping efficiency will be improved by increasing filter body volume, pore density as well as wall thickness and by decreasing exhaust-flow, but effects will be weakened when particulate size exceeds a certain critical value; 4) The steady trapping efficiency will be significantly improved by increasing exhaust-flow temperature and filtering wall thickness, but effects will be also weakened when particulate size exceeds a certain critical value; 5) The steady trapping efficiency will approximately linearly increase with reducing porosity, micropore aperture and pore width.
基金Project(52066008)supported by the National Natural Science Foundation,ChinaProject(2018FA030)supported by Yunnan Province Fundamental Research Key Project Foundation,China+1 种基金Project(2018ZE001)supported by Yunnan Province Major Science and Technology Project Foundation,ChinaProject(202005AG070057)supported by Yunnan Province Science and Technology Innovation Funds for key Laboratories,China。
文摘A three-dimensional diesel particulate filter(DPF)simulation model was developed by using AVL software FIRE to study the effects of four factors on soot particle distributions along the axial and radial directions in the DPF after the model accuracy was validated.An orthogonal test method was used to determine the importance and weights of the design of experiments(DoE)factors such as the expanding angle,the number of channels per square inch,and the exhaust mass flow rate.The effects of these factors on the uniformity of the soot particle distributions were also analyzed.The results show that when the soot loading time was 400 s,the soot particles inside the DPF along the axial direction exhibited a bowl shape,which was high on the both ends and low in the middle.The uniformity of the axial distribution of soot particles reduces significantly with an increase in the number of channels per square inch.The uniformity of the radial distribution reduced with an increase in the expanding angle of the divergent tube.Based on the impacts on the axial uniformity,the three most influencing factors in a descending order are the number of channels per square inch,the exhaust mass flow rate,and the expanding angle of the divergent tube.
基金Project supported by the National Natural Science Foundation of China(21501097,21272118,21577065)the Natural Science Foundation of Jiangsu Province(BK20170954)+2 种基金the Startup Foundation for Introducing Talent of NUIST(2017r073)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China,China(18KJB430019)University Science Research Project of Jiangsu Province(18KJB430019)
文摘The Mn-Ce-Nb-O_x/P84 catalytic filter for removal of particulates and NO simultaneous was prepared by a novel method(foam coating method). The process parameters including the concentrations of PTFE emulsion, particle size of catalyst and calcination temperature for preparation of catalytic filters were analyzed. In addition, the physical properties and performance for removal of NO(NH_3-SCR) and particulates of Mn-Ce-Nb-O_x/P84 catalytic filter prepared under the optimized parameters, were also systematic studied. Results show that the process parameters had significant influences on stability and performance of catalytic filter, The Mn-Ce-Nb-O_x/P84 catalytic filter prepared by foam coating method under the optimized parameters, has satisfactory physical properties and catalytic performance for removal of NO and particulates at 140-220 ℃. The NO removal efficiency of catalytic filter can reach95.3% at 200 ℃ as the catalyst loading amount is 450 g/m^2, Moreover,the dust removal efficiency of MnGe-Nb-O_x/P84 catalytic filter reaches as high as 99.98%, and the PM2.5 removal efficiency also reaches99.98%. The anti-sulfur performance of Mn-Ce-Nb-O_x catalytic filter is also attractive, after injecting150 ppm SO_2, the NO removal efficiency still retains up to 85%. It is indicated that the foam coating method can not only make a bond of high strength between catalyst and filter, but also make the catalytic filter possessing an excellent and stable performance for removal of NO and particulates.
基金supported by the National High Technology Research and Development Program of China(863)(No.2013AA065304)
文摘This study investigated the filtration and continuous regeneration of a particulate filter system on an engine test bench, consisting of a diesel oxidation catalyst（DOC） and a catalyzed diesel particulate filter（CDPF）. Both the DOC and the CDPF led to a high conversion of NO to NO2 for continuous regeneration. The filtration efficiency on solid particle number（SPN） was close to100%. The post-CDPF particles were mainly in accumulation mode. The downstream SPN was sensitively influenced by the variation of the soot loading. This phenomenon provides a method for determining the balance point temperature by measuring the trend of SPN concentration.
基金Projects 2006C23075 supported by the Key Research Project of Zhejiang Province02J20101-19 by the Science Foundation of Ningbo City
文摘A new dual-layer granular bed filter for hot gas cleanup was invented and studied experimentally. Fine sand,0.5-1 mm grain size and about 1350 kg/m3 bulk density,was used as the lower layer of the filter. Expanded perlite par-ticles,2-5 mm grain size and about 70 kg/m3 bulk density,was used for the upper layer of the filter in this study. It was confirmed that the sizes and densities of these two media matched well; the binary media remained in complete segre-gation during regeneration by fluidization. Test results show that the filtration of the expanded perlite particle layer was characterized as "deep bed filtration." Filtration of the fine sand layer was "surface cake filtration." The expanded per-lite particle layer contributed about 90% to the bed dust capacity,but only about 20% to the total bed pressure drop,which increased the bed dust capacity ten fold compared to a single-layer bed of the same sand and the same total bed pressure drop. The dust cake on the surface of the fine sand layer raised the collection efficiencies to over 99.99%.
基金supported by National Hi-tech Research and Development Program of China(863 Program,Grant No.2009AA045103)Tianjin Provincial Natural Science Foundation of China(Grant No.05YFJMJC10700)
文摘Diesel powered vehicles,in compliance with the more strict exhaust emission standards such as Euro V,is likely to require a diesel particulate filter(DPF).A DPF used on a vehicle will affect the acoustic emission of the diesel engine,so it is important to investigate the sound propagation rule in DPF and further to propose the optimum DPF design.However,due to the geometrical complexity of the DPF,the traditional analysis method,such as analytical method,can not assess the acoustic performance of DPF accurately in medium and high frequency band.In this paper,a combined approach of finite element analysis and viscosity correction is proposed to predict acoustic performance of DPF.A simplified model of the full DPF is established and is used to analyze the sound propagation characteristic of the DPF.The distribution of the sound pressure and velocity,the transmission matrix of the DPF are obtained using the finite element method.In addition,the method of the viscosity correction is used in the transmission matrix of the DPF to evaluate the acoustic performance of DPF.Based on the FEM computation and the viscosity correction,the transmission losses under the rated load and idle condition of a diesel engine are calculated.The calculation results show that DPF can effectively attenuate exhaust noise,and sound attenuation increase with the rise of the frequency.Sound attenuation is better under rated condition than idle condition of diesel engine,particularly in frequency above 1000 Hz.
基金Projects(51176045,51276056)supported by the National Natural Science Foundation of ChinaProject(201208430262)supported by the National Studying Abroad Foundation Project of China
文摘Numerical simulation has been carried out to investigate the major factors affecting the time of composite regeneration due to coupling cerium-based additive and microwave for diesel particulate f3ilter(DPF). Effect on the composite regeneration time from various factors such as mass flow rate of exhaust gas, temperature of exhaust gas, oxygen concentration of exhaust gas, microwave power and amount of cerium-based additive are investigated. And a mathematical model based on fuzzy least squares support vector machines has been developed to forecast the endpoint of the composite regeneration. The results show that the relative error of endpoint forecasting model of composite regeneration is less than 3.5%, and the oxygen concentration of exhaust gas has the biggest effect on the endpoint of composite regeneration, followed by the mass flow rate of exhaust gas, the microwave power, the temperature of exhaust gas and the amount of cerium-based additive.
基金supported by the National Natural Science Foundation of China (No. 51006085)the Applied Basic Research Project of Yunnan Province (No. 2013FB052)Department of Education, Yunnan province (No. 2013Z081)
文摘Diesel vehicles are responsible for most of the traffic-related nitrogen oxide（NO x） emissions,including nitric oxide（NO） and nitrogen dioxide（NO2）. The use of after-treatment devices increases the risk of high NO2/NO x emissions from diesel engines. In order to investigate the factors influencing NO2/NO x emissions, an emission experiment was carried out on a high pressure common-rail, turbocharged diesel engine with a catalytic diesel particulate filter（CDPF）. NO2 was measured by a non-dispersive ultraviolet analyzer with raw exhaust sampling. The experimental results show that the NO2/NO x ratios downstream of the CDPF range around 20%–83%, which are significantly higher than those upstream of the CDPF. The exhaust temperature is a decisive factor influencing the NO2/NO x emissions. The maximum NO2/NO x emission appears at the exhaust temperature of 350°C. The space velocity,engine-out PM/NO x ratio（mass based） and CO conversion ratio are secondary factors. At a constant exhaust temperature, the NO2/NO x emissions decreased with increasing space velocity and engine-out PM/NO x ratio. When the CO conversion ratios range from 80% to 90%,the NO2/NO x emissions remain at a high level.
基金sponsored by the National Engineering Laboratory for Mobile Source Emission Control Technology (No. NELMS2020A02)Shanghai Sailing Program (No. 21YF1448900)。
文摘In this study, the effects of a diesel oxidation catalyst(DOC) coupled with a catalyzed diesel particulate filter(CDPF) with different catalyst loadings on the power, fuel consumption,gaseous and particulate emissions from a non-road diesel engine were investigated. Results showed that the after-treatment had a negligible effect on the power and fuel consumption.The reduction effect of the DOC on the CO and hydrocarbon(HC) increased with the engine load. Further reductions occurred coupling with the CDPF. Increasing the catalyst loading resulted in a more significant reduction in the HC emissions than CO emissions. The DOC could increase the NO_(2)proportion to 37.9%, and more NO_(2)was produced when coupled with the CDPF below 250℃;above 250℃, more NO_(2)was consumed. The after-treatment could reduce more than 99% of the particle number(PN) and 98% of the particle mass(PM).Further reductions in the PN and PM occurred with a higher CDPF catalyst loading. The DOC had a better reduction effect on the nucleation particles than the accumulation ones, but the trend reversed with the CDPF. The DOC shifted the particle size distribution(PSD) to larger particles with an accumulation particle proportion increasing from 13% to 20%, and the geometric mean diameter(GMD) increased from 18.2 to 26.0 nm. The trend reversed with the CDPF and the accumulation particle proportion declined to less than 10%. A lower catalyst loading on the CDPF led to a higher proportion of nucleation particles and a smaller GMD.
基金supported by National Natural Science Foundation of China (No. 51806085)China Postdoctoral Science Foundation (No. 2018M642175)+2 种基金Jiangsu Planned Projects for Postdoctoral Research Fund (No. 2018K101C)Open Research Subject of Key Laboratory of Automotive Measurement, Control and Safety (Xihua University) (No. QCCK2021-007)the Graduate Student Innovation Fund Project of Jiangsu Province (No. KYCX21_3354)
文摘To compensate for the shortcomings of the thermal and catalytic regeneration of the diesel particulate filter(DPF),a self-designed packed-bed dielectric barrier discharge(DBD)reactor for DPF regeneration was developed.The DBD reactor with the main active substance of nonthermal plasma(NTP)as the target parameter was optimized by adjusting the feed gas,packing particles(material or size),and cooling water temperature.Moreover,a set of optimal working parameters(gas source,O_2;packing particles,1.2–1.4 mm ZrO_(2);and cooling water temperature,20℃)was selected to evaluate the effect of different O_(3) concentrations on DPF regeneration.The research results showed that selecting packing particles with high dielectric constant and large particles,as well as reducing the cooling water temperature,with oxygen as the feed gas,contributed to an increase in O_(3) concentration.During DPF regeneration,the following changes were observed:the power of the NTP reactor decreased to lower than 100 W,the O_(3) concentration increased from 15 g m^(-3) to 45 g m^(-3),the CO and CO_2 volume fractions of the particulate matter decomposition products increased,and the peak regeneration temperature increased to 173.4℃.The peak temperature arrival time was 60 min earlier,indicating that the regeneration rate of DPF increased with the increase in O_(3) concentration.However,the O_(3) utilization rate(the amount of carbon deposit removed per unit volume O_(3))initially increased and then decreased;when the O_(3) concentration was set to 25 g m^(-3),the highest O_(3) utilization rate was reached.The packed-bed DBD technology contributed to the increase in the concentration of NTP active substances and the regeneration efficiency of DPF.It provides a theoretical and experimental basis for high-efficiency regeneration of DPF at low temperatures(<200℃).
基金Projects(51176045,51276056)supported by the National Natural Science Foundation of ChinaProject(531105050037)supported by the Changjiang Scholars and Innovative Research Team in University,ChinaProjects(201208430262,201306130031)supported by the National Studying Abroad Foundation Project of China
文摘In order to reveal the mechanics of composite regeneration by coupling cerium-based additive and microwave for a diesel particulate filter, a composite regeneration model by coupling cerium-based additive and microwave for a diesel particulate filter was established based on field synergy theory. Performance evaluation on field synergy and composite regeneration of the diesel particulate filter was conducted by using the vortex crushing combustion and field synergy mathematical models. The results show that the peak temperature of the particulate filter body reaches 1180-1190 K when the regeneration time is 175 s, and there are optimal coordination degree between the velocity vector and temperature gradient of the filter body and the maximum ratio0.56-0.60 of the best burning regeneration region is obtained. Accordingly, the largest regeneration combustion rate inside the particulate filter body and the highest regeneration efficiency at the moment are achieved.
基金Project supported by the National Natural Science Foundation of China(22076062,22276070)China Postdoctoral Science Foundation(2022M711957)+1 种基金National Engineering Laboratory for Mobile Source Emission Control Technology(NELMS2019A14)Project of Jinan Municipal Bureau of Science and Technology(2020GXRC021).
文摘The next-generation Euro 7 standard proposed much lower pollutant limits from gasoline vehicles,specifically for CO and NO_(x),which would be challenging for the three-way catalysts(TWCs)utilized commercially to eliminate these pollutants.TWCs with reductive(Rh)and oxidative(Pd)active components on gasoline particulate filters(TWC on GPF)play importantly auxiliary roles in the remediation of CO and NO_(x)downstream the close coupled TWCs to meet their emission targets.Here,a low-content Rh-based TWC(0.17 wt%)zoned with a less expensive Pd-based TWC(0.29 wt%)for GPF applications(cGPF)is reported using improved colloidal deposition method.The supporting of Rh on Y-stabilized ZrO_(2)rather than on CeO_(2)-ZrO_(2)inhibits the formation of inactive Ce rhodate species,while Pd on CeO_(2)-ZrO_(2)not only guarantees the high oxygen storage capacity(OSC)but also enhances catalytic activity.The layout of the front one-fifth in volume being 0.29 wt%Pd on Ce_(0.43)Zr_(0.5)7O_(2)and the rear four-fifths being 0.17 wt%Rh on Zr_(0.85)Y_(0.15)O_(2)prevents the possible alloying of Rh with Pd.The highly effective zoned Rh and Pd TWCs show synergistic three-way activity before and after severe hydrothermal aging at 1000℃with 10%water for24 h,which could be potential choices for close coupled GPF application to satisfy the upcoming stringent emission standards,such as Euro 7 and China 6b.
文摘An experimental system of diesel particulate filter(DPF)regeneration using non-thermal plasma(NTP)technology assisted by exhaust waste heat was conducted and regeneration experiments of DPFs with different amounts of trapped particulate matter(PM)were conducted.The concentrations of the PM decomposition products(CO,)and the internal temperature of the DPF were monitored to determine the performance of DPF regeneration and thermal safety of the NTP technology.The results showed that the concentrations of CO and CO2and the mass of P.V1 decomposition increased with the increase in the amount of captured PM,whereas the concentration of the NTP active substance(O,)escaping from the DPF decreased under the same working conditions of the NTP injection system.A higher amount of captured PM promoted the oxidative decomposition reaction between NTP and PM and improved the utilization rate of the NTP active substances.The peak temperature at the same measuring point inside the DPF generally increased and the phases of the peak temperature were delayed as the amount of captured PM increased.The temperature peaks and temperature gradients during the DPF regeneration process were far lower than llie failure limit value,which indicates that NTP regeneration technology has good thermal durability and increases the service life of the DPF.
基金supported by Project of Science and Technology Development in Wuqing District,Tianjin (No.WQKJ201614)Tianjin 131 innovative talent training project,Postdoctoral Science Foundation
文摘Airborne particulate matter(PM),especially PM2.5,can be easily adsorbed by human respiratory system.Their roles in carrying pathogens for spreading epidemic diseases has attracted great concern.Herein,we developed a novel gelatin filter-based and culture-independent method for investigation of the microbial diversity in PM samples during a haze episode in Tianjin,China.This method involves particle capture by gelatin filters,filter dissolution for DNA extraction,and high-throughput sequencing for analysis of the microbial diversity.A total of 584 operational taxonomic units(OTUs)of bacteria and 370 OTUs of fungi at the genus level were identified during hazy days.The results showed that both bacterial and fungal diversities could be evaluated by this method.This study provides a convenient strategy for investigation of microbial biodiversity in haze,facilitating accurate evaluation of airborne epidemic diseases.
文摘Numerical simulations are performed both for the single airflow and air-PMtwo-phase flow in wall flow diesel participate filters (DPF) for the first time. The calculationdomain is divided into two regions. In. the inlet and outlet flow channels, the simulations areperformed for the steady and laminar flow; In the porous filtration walls, the calculation model forflow in porous media is used. The Lagrange two-phase flow model is used to calculate the air-PMflow in DPF, for the dispersed phase (PM), its flow tracks are obtained by the integrating of theLagrange kinetic equation. The calculated velocity, pressure distribution and PM flow tracks in DPFare obtained, which exhibits the main flow characteristics in wall flow DPF and will be help for theoptimal design and performance prediction of wall flow DPF.
基金Supported by Natural Science Foundation of Tianjin (05YFJMJC10700).
文摘Diesel particulate filter (DPF) is an important factor which influences the sound from exhaust system of an engine. In order to understand the propagation law of sound wave and predict the insertion loss in DPF, based on the general aero-dynamic equations and Darcy′s law, an acoustic property calculation model of DPF is constructed. Propagation and attenuation characteristics of the forward and backward propagating acoustic waves in the close and open pipe of the filter are investigated. The theoretical model is combined with experiment to investigate sound attenuation property of DPF. The insertion loss obtained from the experiment is compared with that computed for a DPF. The results from the experiment and theoretical calculation agree well.
基金supported by the Shanghai Sailing Program (No.21YF1448900)the Jiangxi Technological Innovation Guidance Plan Project (No.20212BDH80015)。
文摘In this study,the effect of new and used catalyzed diesel particulate filter(CDPF)with different catalyst loadings on the particulate emissions including the particle mass(PM),particle number(PN),particle size distribution(PSD)and geometric mean diameter(GMD)from a diesel vehicle were investigated based on a heavy chassis dynamometer.Results showed that more than 97.9%of the PN and 95.4%of the PM were reduced by the CDPF,and the reduction efficiency was enhanced by the catalyst loading.After using the CDPF,the PSD transformed from bimodal to trimodal with the peak shifting towards smaller particle size,more nucleation mode particles were reduced compared with accumulation mode ones,but the reduction effect on the accumulation mode particles was more significantly influenced by the catalyst loading.Notably,the CDPF increased the accumulation mode particles proportion,producing a larger GMD.For the used CDPF,its reduction effect on the particulate emissions enhanced,especially for the PM in accumulation mode.The PSD returned to bimodal,but the peak at accumulation mode began to be higher than that at nucleation mode,illustrating that more nucleation mode particles was removed.The aging of the CDPF resulted in greater effect on the PN-based PSD than that of PM-based PSD,but the effect of catalyst loading on the PN and PM emission factors was weakened.The used CDPF further increased the GMD,and the effect of catalyst loading on the GMD was strengthened,a higher catalyst loading led to a reduction in the GMD.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFE0116100).
文摘Diesel particulate filter(DPF)is a leading technology reducing particle emissions from marine diesel engines.The removal or regeneration of soot in DPF is an important issue.The purpose of this study is to provide some reference strategies to design the DPF for marine diesel engines.In this paper,a mathematical model of a marine DPF was built up and the particle trap process and the regeneration dynamics were simulated.The results show that the cake soot mass concentrations from 0 to 4.2 g/L during the trap process increase linearly with the increase of the exhaust gas flows while the depth soot mass concentrations from 0 to 2.2 g/L firstly increase linearly and then keep constant.Soot is mainly concentrated in the front and rear portion of the filter and less soot is in the middle.The soot distribution in the cake and depth layers shows the unevenness during the trap and regeneration process.The initial soot loadings have great effects on pressure drops and soot mass concentrations before regeneration,but the little effect after regeneration.The exhaust gas temperature heated to 850 K can achieve 94%efficiency for the DPF regeneration.The heating rate has no effects on the pressure drops and soot mass concentrations,but the heating duration time of exhaust gas has an important impact on them.
