In this paper,self-designed multi-hollow needle electrodes are used as a high-voltage electrode in a packed bed dielectric barrier discharge reactor to facilitate fast gas flow through the active discharge area and ac...In this paper,self-designed multi-hollow needle electrodes are used as a high-voltage electrode in a packed bed dielectric barrier discharge reactor to facilitate fast gas flow through the active discharge area and achieve large-volume stable discharge.The dynamic characteristics of the plasma,the generated active species,and the energy transfer mechanisms in both positive discharge(PD)and negative discharge(ND)are investigated by using fast-exposure intensified charge coupled device(ICCD)images and time-resolved optical emission spectra.The experimental results show that the discharge intensity,number of discharge channels,and discharge volume are obviously enhanced when the multi-needle electrode is replaced by a multihollow needle electrode.During a single voltage pulse period,PD mainly develops in a streamer mode,which results in a stronger discharge current,luminous intensity,and E/N compared with the diffuse mode observed in ND.In PD,as the gap between dielectric beads changes from 0 to250μm,the discharge between the dielectric bead gap changes from a partial discharge to a standing filamentary micro-discharge,which allows the plasma to leave the local area and is conducive to the propagation of surface streamers.In ND,the discharge only appears as a diffusionlike mode between the gap of dielectric beads,regardless of whether there is a discharge gap.Moreover,the generation of excited states N_(2)^(+)(B^(2)∑_(u)^(+))and N2(C^(3)Π_(u))is mainly observed in PD,which is attributed to the higher E/N in PD than that in ND.However,the generation of the OH(A^(2)∑^(+))radical in ND is higher than in PD.It is not directly dominated by E/N,but mainly by the resonant energy transfer process between metastable N_(2)(A^(3)∑_(u)^(+))and OH(X^(2)Π).Furthermore,both PD and ND demonstrate obvious energy relaxation processes of electron-to-vibration and vibration-to-vibration,and no vibration-to-rotation energy relaxation process is observed.展开更多
Rotating packing bed(RPB) has a better mixing performance than traditional mixers and shows potential application in the petroleum industry. However, acquisition of information about the mixing process directly throug...Rotating packing bed(RPB) has a better mixing performance than traditional mixers and shows potential application in the petroleum industry. However, acquisition of information about the mixing process directly through experiments is difficult because of the compact structure and complex multiphase flow pattern in RPB. To study the mixing characteristic, Fluent, the computational fluid dynamics(CFD) software, was used to explore the effect of airflow field on droplet diameter. For conducting calculations, the gas-liquid two-phase flow inside the packing was simulated with the RNG k-ε turbulence model and the Lagrange Discrete Phase Model(DPM), respectively. The numerical calculation results showed that coalescence and breakup of droplets can take place in the gas phase flow inside the packing and can be strengthened with increased rotating speed, thereby leading to the enlargement of the average diameter.展开更多
Electrochemical reduction of CO_(2) to fuels and chemicals is a viable strategy for CO_(2) utilization and renewable energy storage.Developing free-standing electrodes from robust and scalable electrocatalysts becomes...Electrochemical reduction of CO_(2) to fuels and chemicals is a viable strategy for CO_(2) utilization and renewable energy storage.Developing free-standing electrodes from robust and scalable electrocatalysts becomes highly desirable.Here,dense SnO_(2) nanoparticles are uniformly grown on three-dimensional(3D)fiber network of carbon cloth(CC)by a facile dip-coating and calcination method.Importantly,Zn modification strategy is employed to restrain the growth of long-range order of SnO_(2) lattices and to produce rich grain boundaries.The hybrid architecture can act as a flexible electrode for CO_(2)-to-formate conversion,which delivers a high partial current of 18.8 m A cm-2 with a formate selectivity of 80%at a moderate cathodic potential of-0.947 V vs.RHE.The electrode exhibits remarkable stability over a 16 h continuous operation.The superior performance is attributed to the synergistic effect of ultrafine SnO_(2) nanoparticles with abundant active sites and 3D fiber network of the electrode for efficient mass transport and electron transfer.The sizeable electrodes hold promise for industrial applications.展开更多
Carbon dioxide （CO2） removal is an essential step in natural gas （NG） processing to provide high quality gas stream products and minimize operational difficulties. This preliminary study alms to investigate the re...Carbon dioxide （CO2） removal is an essential step in natural gas （NG） processing to provide high quality gas stream products and minimize operational difficulties. This preliminary study alms to investigate the removal of CO2 at high concentration level from the mixture of CO2-NG gas stream at elevated pressure via absorption process. This is to explore the possibility of exploring high CO2 content natural gas reserves by treatment at offshore platform. A mixed amine solvent, Stonvent-II, was used for the absorption of approximately 75 vol% CO2 in CO2-NG stream at a pressure of 10 barg. The initial solvent temperature was varied in order to study the impact of initial temperature on the absorption performance. Preliminary study at temperatures of 35 ℃ and 45 ℃ indicates that Stonvent-II was able to perform almost 100% removal of CO2 under both conditions. However, the CO2 absorption effect took place faster when the initial liquid temperature was lower. This is because when the initial liquid temperature is high, the temperature increase in the packing bed caused by the reaction heat is high which impacts the efficiency of absorption negatively.展开更多
NaY Zeolite was synthesized in a rotating packed bed （RPB） for the first time. A Si-A1 gel with a specific composition was used as the structure-directing agent. The as-synthesized NaY Zeolite was characterized with...NaY Zeolite was synthesized in a rotating packed bed （RPB） for the first time. A Si-A1 gel with a specific composition was used as the structure-directing agent. The as-synthesized NaY Zeolite was characterized with scanning electron microscopy （SEM）, X-ray diffraction （XRD） and specific surface area （BET）. The characterization result showed that the NaY Zeolite had a particle size of approximately 200 rim, n（SiO2）/n（Al203） ratio of 5.03, crystallinity of 96% and specific surface area of 714 m2/g. The experimental results indicated that the structure of NaY Zeolite was related to the synthesis conditions （such as reactors, crystallization time and so on）. The micromixing efficiency was proven to be the most important factor for synthesis of NaY Zeolite in the high-gravity environment in RPB.展开更多
We analyse the porous structure of the packed beds in the heat transfer test facility built for high temperature gas cooled reactors from several aspects,such as oscillatory porosity,average porosity,thickness effect,...We analyse the porous structure of the packed beds in the heat transfer test facility built for high temperature gas cooled reactors from several aspects,such as oscillatory porosity,average porosity,thickness effect,coordination number and contact angle.An understanding and comparison of the porous structure of the facility bed and the real reactor core are developed to make recommendations for the design and analysis of the heat transfer test facility.The results show that there is very little difference between the porous characteristics of the two packed beds of spheres.展开更多
The rotating packed bed(RPB), mainly including the countercurrent-flow RPB(Counter-RPB) and the crosscurrentflow RPB(Cross-RPB) that are classified from the perspective of gas-liquid contact style, is a novel process ...The rotating packed bed(RPB), mainly including the countercurrent-flow RPB(Counter-RPB) and the crosscurrentflow RPB(Cross-RPB) that are classified from the perspective of gas-liquid contact style, is a novel process intensification device. A significant measurement standard for evaluating the performance of RPB is the mass transfer effect. In order to compare the mass transfer characteristics of Counter-RPB and Cross-RPB with the same size, the liquid volumetric mass transfer coefficient(k_La_e) and effective interfacial area(a_e) were measured under identical operating conditions. Meanwhile, the comparison of comprehensive mass transfer performance was conducted using the ratio of ΔP(pressure drop) to kLae as the standard. Experimental results indicated that kLae and ae increased with the increase in liquid spray density q, gas velocity u, and high gravity factor β. Furthermore, compared with the Cross-RPB, the Counter-RPB has higher liquid volumetric mass transfer coefficient and slightly larger effective interfacial area. The experimental results of comprehensive mass transfer performance showed that the Counter-RPB had higher ΔP/k_La_e than the Cross-RPB with changes in liquid spray density and high gravity factor, and there exists a turning point at 0.71 m/s accompanied by a variation with gas velocity. Moreover, the relative error of experimental value to calculated value, which was computed by the correlative expressions of kLae, was less than 5 %. In conclusion, the mass transfer characteristics of RPB are deeply impacted by the manner in which the flows are established and the Cross-RPB would have a great potential for industrial scale-up applications.展开更多
Traditionally the majority of fractionation columns in natural gas processing plants were equipped with trays.However an option to trayed columns is to use packing.Packed columns offer a larger surface area per unit v...Traditionally the majority of fractionation columns in natural gas processing plants were equipped with trays.However an option to trayed columns is to use packing.Packed columns offer a larger surface area per unit volume for mass transfer and the continuous gas to liquid contact throughout the column rather than at specific levels （such as in tray columns）.For process design purposes,it is essential to estimate the pressure drop for enabling the proper operation of packed columns.In this study,a simple generalized pressure drop correlation （GPDC） which is easier than existing approaches requiring more complicated and longer computations is developed for sizing randomly packed fractionation columns for pressure drops up to 150 mm water per meter of packing.This correlation can be used to estimate pressure drop for a given loading and column diameter.Alternatively,for a given pressure drop the diameter can be determined.The predictions from the proposed correlation have been compared with reported data and found good agreement with average absolute deviation hovering around 4.9%.The proposed predictive tool is superior owing to its accuracy and clear numerical background,wherein the relevant coefficients can be retuned quickly if new and more accurate data are available in the future.This proposed simple-to-use approach can be of immense practical value for the engineers and scientists to have a quick check on the pressure drop in packed columns for a given loading and column diameter.In particular,gas engineers would find the proposed approach can be used very friendly involving no complex expressions with transparent and easy-to-handle calculation steps.展开更多
Recently,a plasma catalyst was employed to efflciently degrade antibiotic residues in the environment.In this study,the plasma generated in a packed bed dielectric barrier reactor combined with TiO_(2)catalyst is used...Recently,a plasma catalyst was employed to efflciently degrade antibiotic residues in the environment.In this study,the plasma generated in a packed bed dielectric barrier reactor combined with TiO_(2)catalyst is used to degrade the antibiotic tiamulin(TIA)loaded on the surface of simulated soil particles.The effects of applied voltage,composition of the working gas,gas flow rate and presence or absence of catalyst on the degradation effect were studied.It was found that plasma and catalyst can produce a synergistic effect under optimal conditions(applied voltage 25 k V,oxygen ratio 1%,gas flow rate 0.6 l min^(-1),treatment time 5 min).The degradation efflciency of the plasma combined with catalyst can reach 78.6%,which is 18.4%higher than that of plasma without catalyst.When the applied voltage is 30 k V,the gas flow rate is 1 l min^(-1),the oxygen ratio is 1%and the plasma combined with TiO_(2)catalyst treats the sample for 5 min the degradation efflciency of TIA reached 97%.It can be concluded that a higher applied voltage and longer processing times not only lead to more degradation but also result in a lower energy efflciency.Decreasing the oxygen ratio and gas flow rate could improve the degradation efflciency.The relative distribution and identity of the major TIA degradation product generated was determined by high-performance liquid chromatography–mass spectrometry analysis.The mechanism of TIA removal by plasma and TiO_(2)catalyst was analyzed,and the possible degradation path is discussed.展开更多
In this article,plasma-assisted NH;synthesis directly from N;and H;over packing materials with different dielectric constants(BaTiO_(2),TiO_(2) and SiO_(2))and thermal conductivities(Be O,Al N and Al_(2)O_(2))at room ...In this article,plasma-assisted NH;synthesis directly from N;and H;over packing materials with different dielectric constants(BaTiO_(2),TiO_(2) and SiO_(2))and thermal conductivities(Be O,Al N and Al_(2)O_(2))at room temperature and atmospheric pressure is reported.The higher dielectric constant and thermal conductivity of packing material are found to be the key parameters in enhancing the NH;synthesis performance.The NH;concentration of 1344 ppm is achieved in the presence of BaTiO_(2),which is 106%higher than that of SiO_(2),at the specific input energy(SIE)of 5.4 k J·l^(-1).The presence of materials with higher dielectric constant,i.e.BaTiO_(2) and TiO_(2)in this work,would contribute to the increase of electron energy and energy injected to plasma,which is conductive to the generation of chemically active species by electron-impact reactions.Therefore,the employment of packing materials with higher dielectric constant has proved to be beneficial for NH;synthesis.Compared to that of Al_(2)O_(3),the presence of Be O and Al N yields 31.0%and 16.9%improvement in NH;concentration,respectively,at the SIE of5.4 k J·l^(-1).The results of IR imaging show that the addition of Be O decreases the surface temperature of the packed region by 20.5%to 70.3℃ and results in an extension of entropy increment compared to that of Al_(2)O_(3),at the SIE of 5.4 k J·l^(-1).The results indicate that the presence of materials with higher thermal conductivity is beneficial for NH;synthesis,which has been confirmed by the lower surface temperature and higher entropy increment of the packed region.In addition,when SIE is higher than the optimal value,further increasing SIE would lead to the decrease of energy efficiency,which would be related to the exacerbation in reverse reaction of NH;formation reactions.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
Recent work has validated a new method for estimating the grain size of microgranular materials in the range of tens to hundreds of micrometers using laser-induced breakdown spectroscopy(LIBS).In this situation,a piec...Recent work has validated a new method for estimating the grain size of microgranular materials in the range of tens to hundreds of micrometers using laser-induced breakdown spectroscopy(LIBS).In this situation,a piecewise univariate model must be constructed to estimate grain size due to the complex dependence of the plasma formation environment on grain size.In the present work,we tentatively construct a unified calibration model suitable for LIBS-based estimation of those grain sizes.Specifically,two unified multivariate calibration models are constructed based on back-propagation neural network(BPNN)algorithms using feature selection strategies with and without considering prior information.By detailed analysis of the performances of the two multivariate models,it was found that a unified calibration model can be successfully constructed based on BPNN algorithms for estimating the grain size in the range of tens to hundreds of micrometers.It was also found that the model constructed with a priorguided feature selection strategy had better prediction performance.This study has practical significance in developing the technology for material analysis using LIBS,especially when the LIBS signal exhibits a complex dependence on the material parameter to be estimated.展开更多
Accurate capacity estimation is of great importance for the reliable state monitoring,timely maintenance,and second-life utilization of lithium-ion batteries.Despite numerous works on battery capacity estimation using...Accurate capacity estimation is of great importance for the reliable state monitoring,timely maintenance,and second-life utilization of lithium-ion batteries.Despite numerous works on battery capacity estimation using laboratory datasets,most of them are applied to battery cells and lack satisfactory fidelity when extended to real-world electric vehicle(EV)battery packs.The challenges intensify for large-sized EV battery packs,where unpredictable operating profiles and low-quality data acquisition hinder precise capacity estimation.To fill the gap,this study introduces a novel data-driven battery pack capacity estimation method grounded in field data.The proposed approach begins by determining labeled capacity through an innovative combination of the inverse ampere-hour integral,open circuit voltage-based,and resistance-based correction methods.Then,multiple health features are extracted from incremental capacity curves,voltage curves,equivalent circuit model parameters,and operating temperature to thoroughly characterize battery aging behavior.A feature selection procedure is performed to determine the optimal feature set based on the Pearson correlation coefficient.Moreover,a convolutional neural network and bidirectional gated recurrent unit,enhanced by an attention mechanism,are employed to estimate the battery pack capacity in real-world EV applications.Finally,the proposed method is validated with a field dataset from two EVs,covering approximately 35,000 kilometers.The results demonstrate that the proposed method exhibits better estimation performance with an error of less than 1.1%compared to existing methods.This work shows great potential for accurate large-sized EV battery pack capacity estimation based on field data,which provides significant insights into reliable labeled capacity calculation,effective features extraction,and machine learning-enabled health diagnosis.展开更多
Cell-to-cell variations(CtCV) compromise the electrochemical performance of battery packs, yet the evolutional mechanism and quantitative impacts of CtCV on the pack's fast-charging performance remain unexplored. ...Cell-to-cell variations(CtCV) compromise the electrochemical performance of battery packs, yet the evolutional mechanism and quantitative impacts of CtCV on the pack's fast-charging performance remain unexplored. This knowledge gap is vital for the proliferation of electric vehicles. This study underlies the relationship between CtCV and charging performance by assessing the pack's charge speed, final electric quantity, and temperature consistency. Cell variations and pack status are depicted using 2D parameter diagrams, and an m PnS configured pack model is built upon a decomposed electrode cell model.Variations in three single electric parameters, i.e., capacity(Q), electric quantity(E), and internal resistance(R), and their dual interactions, i.e., E-Q and R-Q, are analyzed carefully. The results indicate that Q variations predominantly affect the final electric quantity of the pack, while R variations impact the charge speed most. With incremental variances in cell parameters, the pack's fast-charging capability first declines linearly and then deteriorates sharply as variations intensify. This research elucidates the correlations between pack charging capabilities and cell variations, providing essential insights for optimizing cell sorting and assembly, battery management design, and charging protocol development for battery packs.展开更多
The liquid-cooled battery energy sto rage system(LCBESS) has gained significant attention due to its superior thermal management capacity.However,liquid-cooled battery pack(LCBP) usually has a high sealing level above...The liquid-cooled battery energy sto rage system(LCBESS) has gained significant attention due to its superior thermal management capacity.However,liquid-cooled battery pack(LCBP) usually has a high sealing level above IP65,which can trap flammable and explosive gases from battery thermal runaway and cause explosions.This poses serious safety risks and challenges for LCBESS.In this study,we tested overcharged battery inside a commercial LCBP and found that the conventionally mechanical pressure relief valve(PRV) on the LCBP had a delayed response and low-pressure relief efficiency.A realistic 20-foot model of an energy storage cabin was constructed using the Flacs finite element simulation software.Comparative studies were conducted to evaluate the pressure relief efficiency and the influence on neighboring battery packs in case of internal explosions,considering different sizes and installation positions of the PRV.Here,a newly developed electric-controlled PRV integrated with battery fault detection is introduced,capable of starting within 50 ms of the battery safety valve opening.Furthermore,the PRV was integrated with the battery management system and changed the battery charging and discharging strategy after the PRV was opened.Experimental tests confirmed the efficacy of this method in preventing explosions.This paper addresses the safety concerns associated with LCBPs and proposes an effective solution for explosion relief.展开更多
Molecular dynamics simulation is used to calculate the interfacial thermal resistance of a graphene/carbon nanotubes/hexagonal boron nitride(Gr/CNTs/hBN)sandwiched heterostructure,in which vertically aligned carbon na...Molecular dynamics simulation is used to calculate the interfacial thermal resistance of a graphene/carbon nanotubes/hexagonal boron nitride(Gr/CNTs/hBN)sandwiched heterostructure,in which vertically aligned carbon nanotube(VACNT)arrays are covalently bonded to graphene and hexagonal boron nitride layers.We find that the interfacial thermal resistance(ITR)of the Gr/VACNT/hBN sandwiched heterostructure is one to two orders of magnitude smaller than the ITR of a Gr/hBN van der Waals heterostructure with the same plane size.It is observed that covalent bonding effectively enhances the phonon coupling between Gr and hBN layers,resulting in an increase in the overlap factor of phonon density of states between Gr and hBN,thus reducing the ITR of Gr and hBN.In addition,the chirality,size(diameter and length),and packing density of sandwich-layer VACNTs have an important influence on the ITR of the heterostructure.Under the same CNT diameter and length,the ITR of the sandwiched heterostructure with armchair-shaped VACNTs is higher than that of the sandwiched heterostructure with zigzag-shaped VACNTs due to the different chemical bonding of chiral CNTs with Gr and hBN.When the armchair-shaped CNT diameter increases or the length decreases,the ITR of the sandwiched heterostructure tends to decrease.Moreover,the increase in the VACNT packing density also leads to a continuous decrease in the ITR of the sandwiched heterostructure,attributed to the extremely high intrinsic thermal conductivity of CNTs and the increase of out-of-plane heat transfer channels.This work may be helpful for understanding the mechanism for ITR in multilayer vertical heterostructures,and provides theoretical guidance for a new strategy to regulate the interlayer thermal resistance of heterostructures by optimizing the design of sandwich layer thermal interface materials.展开更多
Battery pack capacity estimation under real-world operating conditions is important for battery performance optimization and health management,contributing to the reliability and longevity of batterypowered systems.Ho...Battery pack capacity estimation under real-world operating conditions is important for battery performance optimization and health management,contributing to the reliability and longevity of batterypowered systems.However,complex operating conditions,coupling cell-to-cell inconsistency,and limited labeled data pose great challenges to accurate and robust battery pack capacity estimation.To address these issues,this paper proposes a hierarchical data-driven framework aimed at enhancing the training of machine learning models with fewer labeled data.Unlike traditional data-driven methods that lack interpretability,the hierarchical data-driven framework unveils the“mechanism”of the black box inside the data-driven framework by splitting the final estimation target into cell-level and pack-level intermediate targets.A generalized feature matrix is devised without requiring all cell voltages,significantly reducing the computational cost and memory resources.The generated intermediate target labels and the corresponding features are hierarchically employed to enhance the training of two machine learning models,effectively alleviating the difficulty of learning the relationship from all features due to fewer labeled data and addressing the dilemma of requiring extensive labeled data for accurate estimation.Using only 10%of degradation data,the proposed framework outperforms the state-of-the-art battery pack capacity estimation methods,achieving mean absolute percentage errors of 0.608%,0.601%,and 1.128%for three battery packs whose degradation load profiles represent real-world operating conditions.Its high accuracy,adaptability,and robustness indicate the potential in different application scenarios,which is promising for reducing laborious and expensive aging experiments at the pack level and facilitating the development of battery technology.展开更多
Fixed-bed reactors are generally considered the optimal choice for numerous multi-phase catalytic reactions due to their excellent performance and stability.However,conventional fixed beds often encounter challenges r...Fixed-bed reactors are generally considered the optimal choice for numerous multi-phase catalytic reactions due to their excellent performance and stability.However,conventional fixed beds often encounter challenges related to inadequate mass transfer and a high pressure drop caused by the non-uniform void fraction distribution.To enhance the overall performance of fixed beds,the impact of different packing configurations on performance was investigated.Experimental and simulation methods were used to investigate the fluid flow and mass transfer performances of various packed beds under different flow rates.It was found that structured beds exhibited a significantly lower pressure drop per unit length than conventional packed beds.Furthermore,the packing configurations had a critical role in improving the overall performance of fixed beds.Specifically,structured packed beds,particularly the H-2 packing configuration,effectively reduced the pressure drop per unit length and improved the mass transfer efficiency.The H-2 packing configuration consisted of two parallel strips of particles in each layer,with strips arranged perpendicularly between adjacent layers,and the spacing between the strips varied from layer to layer.展开更多
基金supported by National Natural Science Foundations of China(Nos.51977023 and 52077026)the Fundamental Research Funds for the Central Universities(No.DUT23YG227)。
文摘In this paper,self-designed multi-hollow needle electrodes are used as a high-voltage electrode in a packed bed dielectric barrier discharge reactor to facilitate fast gas flow through the active discharge area and achieve large-volume stable discharge.The dynamic characteristics of the plasma,the generated active species,and the energy transfer mechanisms in both positive discharge(PD)and negative discharge(ND)are investigated by using fast-exposure intensified charge coupled device(ICCD)images and time-resolved optical emission spectra.The experimental results show that the discharge intensity,number of discharge channels,and discharge volume are obviously enhanced when the multi-needle electrode is replaced by a multihollow needle electrode.During a single voltage pulse period,PD mainly develops in a streamer mode,which results in a stronger discharge current,luminous intensity,and E/N compared with the diffuse mode observed in ND.In PD,as the gap between dielectric beads changes from 0 to250μm,the discharge between the dielectric bead gap changes from a partial discharge to a standing filamentary micro-discharge,which allows the plasma to leave the local area and is conducive to the propagation of surface streamers.In ND,the discharge only appears as a diffusionlike mode between the gap of dielectric beads,regardless of whether there is a discharge gap.Moreover,the generation of excited states N_(2)^(+)(B^(2)∑_(u)^(+))and N2(C^(3)Π_(u))is mainly observed in PD,which is attributed to the higher E/N in PD than that in ND.However,the generation of the OH(A^(2)∑^(+))radical in ND is higher than in PD.It is not directly dominated by E/N,but mainly by the resonant energy transfer process between metastable N_(2)(A^(3)∑_(u)^(+))and OH(X^(2)Π).Furthermore,both PD and ND demonstrate obvious energy relaxation processes of electron-to-vibration and vibration-to-vibration,and no vibration-to-rotation energy relaxation process is observed.
基金financially supported by the Natural Science Foundations of China(No.21206153,21376229)the Excellent Youth Science and Technology Foundation of Province Shanxi of China(No.2014021007)+1 种基金the Natural Science Foundation of Shanxi Province(Grant No.2011021012,2012011008-2)the Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi(201316)
文摘Rotating packing bed(RPB) has a better mixing performance than traditional mixers and shows potential application in the petroleum industry. However, acquisition of information about the mixing process directly through experiments is difficult because of the compact structure and complex multiphase flow pattern in RPB. To study the mixing characteristic, Fluent, the computational fluid dynamics(CFD) software, was used to explore the effect of airflow field on droplet diameter. For conducting calculations, the gas-liquid two-phase flow inside the packing was simulated with the RNG k-ε turbulence model and the Lagrange Discrete Phase Model(DPM), respectively. The numerical calculation results showed that coalescence and breakup of droplets can take place in the gas phase flow inside the packing and can be strengthened with increased rotating speed, thereby leading to the enlargement of the average diameter.
基金supported by the National Natural Science Foundation of China(51902204,22003041,21975163)Bureau of Industry and Information Technology of Shenzhen(201901171518)Shenzhen Science and Technology Program(KQTD20190929173914967)。
文摘Electrochemical reduction of CO_(2) to fuels and chemicals is a viable strategy for CO_(2) utilization and renewable energy storage.Developing free-standing electrodes from robust and scalable electrocatalysts becomes highly desirable.Here,dense SnO_(2) nanoparticles are uniformly grown on three-dimensional(3D)fiber network of carbon cloth(CC)by a facile dip-coating and calcination method.Importantly,Zn modification strategy is employed to restrain the growth of long-range order of SnO_(2) lattices and to produce rich grain boundaries.The hybrid architecture can act as a flexible electrode for CO_(2)-to-formate conversion,which delivers a high partial current of 18.8 m A cm-2 with a formate selectivity of 80%at a moderate cathodic potential of-0.947 V vs.RHE.The electrode exhibits remarkable stability over a 16 h continuous operation.The superior performance is attributed to the synergistic effect of ultrafine SnO_(2) nanoparticles with abundant active sites and 3D fiber network of the electrode for efficient mass transport and electron transfer.The sizeable electrodes hold promise for industrial applications.
文摘Carbon dioxide （CO2） removal is an essential step in natural gas （NG） processing to provide high quality gas stream products and minimize operational difficulties. This preliminary study alms to investigate the removal of CO2 at high concentration level from the mixture of CO2-NG gas stream at elevated pressure via absorption process. This is to explore the possibility of exploring high CO2 content natural gas reserves by treatment at offshore platform. A mixed amine solvent, Stonvent-II, was used for the absorption of approximately 75 vol% CO2 in CO2-NG stream at a pressure of 10 barg. The initial solvent temperature was varied in order to study the impact of initial temperature on the absorption performance. Preliminary study at temperatures of 35 ℃ and 45 ℃ indicates that Stonvent-II was able to perform almost 100% removal of CO2 under both conditions. However, the CO2 absorption effect took place faster when the initial liquid temperature was lower. This is because when the initial liquid temperature is high, the temperature increase in the packing bed caused by the reaction heat is high which impacts the efficiency of absorption negatively.
基金supported by the National Basic Research Program of China (973 Program)(No. 2004CB217804)the Science and Technology Development Project of PetroChina (050203-01-06)
文摘NaY Zeolite was synthesized in a rotating packed bed （RPB） for the first time. A Si-A1 gel with a specific composition was used as the structure-directing agent. The as-synthesized NaY Zeolite was characterized with scanning electron microscopy （SEM）, X-ray diffraction （XRD） and specific surface area （BET）. The characterization result showed that the NaY Zeolite had a particle size of approximately 200 rim, n（SiO2）/n（Al203） ratio of 5.03, crystallinity of 96% and specific surface area of 714 m2/g. The experimental results indicated that the structure of NaY Zeolite was related to the synthesis conditions （such as reactors, crystallization time and so on）. The micromixing efficiency was proven to be the most important factor for synthesis of NaY Zeolite in the high-gravity environment in RPB.
基金Supported by the National Science and Technology Major Project under Grant No ZX06901the National Natural Science Foundation of China under Grant No 11072131.
文摘We analyse the porous structure of the packed beds in the heat transfer test facility built for high temperature gas cooled reactors from several aspects,such as oscillatory porosity,average porosity,thickness effect,coordination number and contact angle.An understanding and comparison of the porous structure of the facility bed and the real reactor core are developed to make recommendations for the design and analysis of the heat transfer test facility.The results show that there is very little difference between the porous characteristics of the two packed beds of spheres.
基金supported by the National Key R&D Program of China:The ultra-low emission control technology for coal-fired industrial boilers(2016YFC0204103)the Provincial Key R&D Program of Shanxi:R&D of the coal-fired industrial boiler smoke ultra-low emission technology and equipment(201703D111018)
文摘The rotating packed bed(RPB), mainly including the countercurrent-flow RPB(Counter-RPB) and the crosscurrentflow RPB(Cross-RPB) that are classified from the perspective of gas-liquid contact style, is a novel process intensification device. A significant measurement standard for evaluating the performance of RPB is the mass transfer effect. In order to compare the mass transfer characteristics of Counter-RPB and Cross-RPB with the same size, the liquid volumetric mass transfer coefficient(k_La_e) and effective interfacial area(a_e) were measured under identical operating conditions. Meanwhile, the comparison of comprehensive mass transfer performance was conducted using the ratio of ΔP(pressure drop) to kLae as the standard. Experimental results indicated that kLae and ae increased with the increase in liquid spray density q, gas velocity u, and high gravity factor β. Furthermore, compared with the Cross-RPB, the Counter-RPB has higher liquid volumetric mass transfer coefficient and slightly larger effective interfacial area. The experimental results of comprehensive mass transfer performance showed that the Counter-RPB had higher ΔP/k_La_e than the Cross-RPB with changes in liquid spray density and high gravity factor, and there exists a turning point at 0.71 m/s accompanied by a variation with gas velocity. Moreover, the relative error of experimental value to calculated value, which was computed by the correlative expressions of kLae, was less than 5 %. In conclusion, the mass transfer characteristics of RPB are deeply impacted by the manner in which the flows are established and the Cross-RPB would have a great potential for industrial scale-up applications.
文摘Traditionally the majority of fractionation columns in natural gas processing plants were equipped with trays.However an option to trayed columns is to use packing.Packed columns offer a larger surface area per unit volume for mass transfer and the continuous gas to liquid contact throughout the column rather than at specific levels （such as in tray columns）.For process design purposes,it is essential to estimate the pressure drop for enabling the proper operation of packed columns.In this study,a simple generalized pressure drop correlation （GPDC） which is easier than existing approaches requiring more complicated and longer computations is developed for sizing randomly packed fractionation columns for pressure drops up to 150 mm water per meter of packing.This correlation can be used to estimate pressure drop for a given loading and column diameter.Alternatively,for a given pressure drop the diameter can be determined.The predictions from the proposed correlation have been compared with reported data and found good agreement with average absolute deviation hovering around 4.9%.The proposed predictive tool is superior owing to its accuracy and clear numerical background,wherein the relevant coefficients can be retuned quickly if new and more accurate data are available in the future.This proposed simple-to-use approach can be of immense practical value for the engineers and scientists to have a quick check on the pressure drop in packed columns for a given loading and column diameter.In particular,gas engineers would find the proposed approach can be used very friendly involving no complex expressions with transparent and easy-to-handle calculation steps.
基金supported by National Natural Science Foundation of China(Nos.51967018,11965018 and 51967017)the Science and Technology Development Fund of Xinjiang Production and Construction(No.2019BC009)the Innovation and Development Special Project of Shihezi University(No.CXFZ202105)。
文摘Recently,a plasma catalyst was employed to efflciently degrade antibiotic residues in the environment.In this study,the plasma generated in a packed bed dielectric barrier reactor combined with TiO_(2)catalyst is used to degrade the antibiotic tiamulin(TIA)loaded on the surface of simulated soil particles.The effects of applied voltage,composition of the working gas,gas flow rate and presence or absence of catalyst on the degradation effect were studied.It was found that plasma and catalyst can produce a synergistic effect under optimal conditions(applied voltage 25 k V,oxygen ratio 1%,gas flow rate 0.6 l min^(-1),treatment time 5 min).The degradation efflciency of the plasma combined with catalyst can reach 78.6%,which is 18.4%higher than that of plasma without catalyst.When the applied voltage is 30 k V,the gas flow rate is 1 l min^(-1),the oxygen ratio is 1%and the plasma combined with TiO_(2)catalyst treats the sample for 5 min the degradation efflciency of TIA reached 97%.It can be concluded that a higher applied voltage and longer processing times not only lead to more degradation but also result in a lower energy efflciency.Decreasing the oxygen ratio and gas flow rate could improve the degradation efflciency.The relative distribution and identity of the major TIA degradation product generated was determined by high-performance liquid chromatography–mass spectrometry analysis.The mechanism of TIA removal by plasma and TiO_(2)catalyst was analyzed,and the possible degradation path is discussed.
基金the financial support from National Natural Science Foundation of China(No.51976093)K C Wong Magna Fund in Ningbo University。
文摘In this article,plasma-assisted NH;synthesis directly from N;and H;over packing materials with different dielectric constants(BaTiO_(2),TiO_(2) and SiO_(2))and thermal conductivities(Be O,Al N and Al_(2)O_(2))at room temperature and atmospheric pressure is reported.The higher dielectric constant and thermal conductivity of packing material are found to be the key parameters in enhancing the NH;synthesis performance.The NH;concentration of 1344 ppm is achieved in the presence of BaTiO_(2),which is 106%higher than that of SiO_(2),at the specific input energy(SIE)of 5.4 k J·l^(-1).The presence of materials with higher dielectric constant,i.e.BaTiO_(2) and TiO_(2)in this work,would contribute to the increase of electron energy and energy injected to plasma,which is conductive to the generation of chemically active species by electron-impact reactions.Therefore,the employment of packing materials with higher dielectric constant has proved to be beneficial for NH;synthesis.Compared to that of Al_(2)O_(3),the presence of Be O and Al N yields 31.0%and 16.9%improvement in NH;concentration,respectively,at the SIE of5.4 k J·l^(-1).The results of IR imaging show that the addition of Be O decreases the surface temperature of the packed region by 20.5%to 70.3℃ and results in an extension of entropy increment compared to that of Al_(2)O_(3),at the SIE of 5.4 k J·l^(-1).The results indicate that the presence of materials with higher thermal conductivity is beneficial for NH;synthesis,which has been confirmed by the lower surface temperature and higher entropy increment of the packed region.In addition,when SIE is higher than the optimal value,further increasing SIE would lead to the decrease of energy efficiency,which would be related to the exacerbation in reverse reaction of NH;formation reactions.
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supported in part by the National Key Research and Development Program of China(No.2017YFA0402300)National Natural Science Foundation of China(Nos.U2241288 and 11974359)Major Science and Technology Project of Gansu Province(No.22ZD6FA021-5)。
文摘Recent work has validated a new method for estimating the grain size of microgranular materials in the range of tens to hundreds of micrometers using laser-induced breakdown spectroscopy(LIBS).In this situation,a piecewise univariate model must be constructed to estimate grain size due to the complex dependence of the plasma formation environment on grain size.In the present work,we tentatively construct a unified calibration model suitable for LIBS-based estimation of those grain sizes.Specifically,two unified multivariate calibration models are constructed based on back-propagation neural network(BPNN)algorithms using feature selection strategies with and without considering prior information.By detailed analysis of the performances of the two multivariate models,it was found that a unified calibration model can be successfully constructed based on BPNN algorithms for estimating the grain size in the range of tens to hundreds of micrometers.It was also found that the model constructed with a priorguided feature selection strategy had better prediction performance.This study has practical significance in developing the technology for material analysis using LIBS,especially when the LIBS signal exhibits a complex dependence on the material parameter to be estimated.
基金supported in part by the National Key Research and Development Program of China(No.2022YFB3305403)Project of basic research funds for central universities(2022CDJDX006)+1 种基金Talent Plan Project of Chongqing(No.cstc2021ycjhbgzxm0295)National Natural Science Foundation of China(No.52111530194)。
文摘Accurate capacity estimation is of great importance for the reliable state monitoring,timely maintenance,and second-life utilization of lithium-ion batteries.Despite numerous works on battery capacity estimation using laboratory datasets,most of them are applied to battery cells and lack satisfactory fidelity when extended to real-world electric vehicle(EV)battery packs.The challenges intensify for large-sized EV battery packs,where unpredictable operating profiles and low-quality data acquisition hinder precise capacity estimation.To fill the gap,this study introduces a novel data-driven battery pack capacity estimation method grounded in field data.The proposed approach begins by determining labeled capacity through an innovative combination of the inverse ampere-hour integral,open circuit voltage-based,and resistance-based correction methods.Then,multiple health features are extracted from incremental capacity curves,voltage curves,equivalent circuit model parameters,and operating temperature to thoroughly characterize battery aging behavior.A feature selection procedure is performed to determine the optimal feature set based on the Pearson correlation coefficient.Moreover,a convolutional neural network and bidirectional gated recurrent unit,enhanced by an attention mechanism,are employed to estimate the battery pack capacity in real-world EV applications.Finally,the proposed method is validated with a field dataset from two EVs,covering approximately 35,000 kilometers.The results demonstrate that the proposed method exhibits better estimation performance with an error of less than 1.1%compared to existing methods.This work shows great potential for accurate large-sized EV battery pack capacity estimation based on field data,which provides significant insights into reliable labeled capacity calculation,effective features extraction,and machine learning-enabled health diagnosis.
基金supported by the National Natural Science Foundation of China under No. 52177217the Postdoctoral Innovative Talents Support Program under No. BX20240232。
文摘Cell-to-cell variations(CtCV) compromise the electrochemical performance of battery packs, yet the evolutional mechanism and quantitative impacts of CtCV on the pack's fast-charging performance remain unexplored. This knowledge gap is vital for the proliferation of electric vehicles. This study underlies the relationship between CtCV and charging performance by assessing the pack's charge speed, final electric quantity, and temperature consistency. Cell variations and pack status are depicted using 2D parameter diagrams, and an m PnS configured pack model is built upon a decomposed electrode cell model.Variations in three single electric parameters, i.e., capacity(Q), electric quantity(E), and internal resistance(R), and their dual interactions, i.e., E-Q and R-Q, are analyzed carefully. The results indicate that Q variations predominantly affect the final electric quantity of the pack, while R variations impact the charge speed most. With incremental variances in cell parameters, the pack's fast-charging capability first declines linearly and then deteriorates sharply as variations intensify. This research elucidates the correlations between pack charging capabilities and cell variations, providing essential insights for optimizing cell sorting and assembly, battery management design, and charging protocol development for battery packs.
基金sponsored by the Science and Technology Program of State Grid Corporation of China(4000-202355090A-1-1ZN)。
文摘The liquid-cooled battery energy sto rage system(LCBESS) has gained significant attention due to its superior thermal management capacity.However,liquid-cooled battery pack(LCBP) usually has a high sealing level above IP65,which can trap flammable and explosive gases from battery thermal runaway and cause explosions.This poses serious safety risks and challenges for LCBESS.In this study,we tested overcharged battery inside a commercial LCBP and found that the conventionally mechanical pressure relief valve(PRV) on the LCBP had a delayed response and low-pressure relief efficiency.A realistic 20-foot model of an energy storage cabin was constructed using the Flacs finite element simulation software.Comparative studies were conducted to evaluate the pressure relief efficiency and the influence on neighboring battery packs in case of internal explosions,considering different sizes and installation positions of the PRV.Here,a newly developed electric-controlled PRV integrated with battery fault detection is introduced,capable of starting within 50 ms of the battery safety valve opening.Furthermore,the PRV was integrated with the battery management system and changed the battery charging and discharging strategy after the PRV was opened.Experimental tests confirmed the efficacy of this method in preventing explosions.This paper addresses the safety concerns associated with LCBPs and proposes an effective solution for explosion relief.
基金supported by the Fundamental Research Funds for the Central Universities of China(Grant No.2019ZDPY16)the support of the funding for the key discipline of physics at the China University of Mining and Technologythe support of the Shenzhen Yuliang Technology Co.,Ltd.。
文摘Molecular dynamics simulation is used to calculate the interfacial thermal resistance of a graphene/carbon nanotubes/hexagonal boron nitride(Gr/CNTs/hBN)sandwiched heterostructure,in which vertically aligned carbon nanotube(VACNT)arrays are covalently bonded to graphene and hexagonal boron nitride layers.We find that the interfacial thermal resistance(ITR)of the Gr/VACNT/hBN sandwiched heterostructure is one to two orders of magnitude smaller than the ITR of a Gr/hBN van der Waals heterostructure with the same plane size.It is observed that covalent bonding effectively enhances the phonon coupling between Gr and hBN layers,resulting in an increase in the overlap factor of phonon density of states between Gr and hBN,thus reducing the ITR of Gr and hBN.In addition,the chirality,size(diameter and length),and packing density of sandwich-layer VACNTs have an important influence on the ITR of the heterostructure.Under the same CNT diameter and length,the ITR of the sandwiched heterostructure with armchair-shaped VACNTs is higher than that of the sandwiched heterostructure with zigzag-shaped VACNTs due to the different chemical bonding of chiral CNTs with Gr and hBN.When the armchair-shaped CNT diameter increases or the length decreases,the ITR of the sandwiched heterostructure tends to decrease.Moreover,the increase in the VACNT packing density also leads to a continuous decrease in the ITR of the sandwiched heterostructure,attributed to the extremely high intrinsic thermal conductivity of CNTs and the increase of out-of-plane heat transfer channels.This work may be helpful for understanding the mechanism for ITR in multilayer vertical heterostructures,and provides theoretical guidance for a new strategy to regulate the interlayer thermal resistance of heterostructures by optimizing the design of sandwich layer thermal interface materials.
基金supported by the National Outstanding Youth Science Fund Project of National Natural Science Foundation of China[Grant No.52222708]the Natural Science Foundation of Beijing Municipality[Grant No.3212033]。
文摘Battery pack capacity estimation under real-world operating conditions is important for battery performance optimization and health management,contributing to the reliability and longevity of batterypowered systems.However,complex operating conditions,coupling cell-to-cell inconsistency,and limited labeled data pose great challenges to accurate and robust battery pack capacity estimation.To address these issues,this paper proposes a hierarchical data-driven framework aimed at enhancing the training of machine learning models with fewer labeled data.Unlike traditional data-driven methods that lack interpretability,the hierarchical data-driven framework unveils the“mechanism”of the black box inside the data-driven framework by splitting the final estimation target into cell-level and pack-level intermediate targets.A generalized feature matrix is devised without requiring all cell voltages,significantly reducing the computational cost and memory resources.The generated intermediate target labels and the corresponding features are hierarchically employed to enhance the training of two machine learning models,effectively alleviating the difficulty of learning the relationship from all features due to fewer labeled data and addressing the dilemma of requiring extensive labeled data for accurate estimation.Using only 10%of degradation data,the proposed framework outperforms the state-of-the-art battery pack capacity estimation methods,achieving mean absolute percentage errors of 0.608%,0.601%,and 1.128%for three battery packs whose degradation load profiles represent real-world operating conditions.Its high accuracy,adaptability,and robustness indicate the potential in different application scenarios,which is promising for reducing laborious and expensive aging experiments at the pack level and facilitating the development of battery technology.
文摘Fixed-bed reactors are generally considered the optimal choice for numerous multi-phase catalytic reactions due to their excellent performance and stability.However,conventional fixed beds often encounter challenges related to inadequate mass transfer and a high pressure drop caused by the non-uniform void fraction distribution.To enhance the overall performance of fixed beds,the impact of different packing configurations on performance was investigated.Experimental and simulation methods were used to investigate the fluid flow and mass transfer performances of various packed beds under different flow rates.It was found that structured beds exhibited a significantly lower pressure drop per unit length than conventional packed beds.Furthermore,the packing configurations had a critical role in improving the overall performance of fixed beds.Specifically,structured packed beds,particularly the H-2 packing configuration,effectively reduced the pressure drop per unit length and improved the mass transfer efficiency.The H-2 packing configuration consisted of two parallel strips of particles in each layer,with strips arranged perpendicularly between adjacent layers,and the spacing between the strips varied from layer to layer.
