Switched-capacitor/flying capacitor(FC)based multilevel converters have been gaining higher attention for their voltage-boosting ability.This feature makes them an attractive solution for renewable energy systems,such...Switched-capacitor/flying capacitor(FC)based multilevel converters have been gaining higher attention for their voltage-boosting ability.This feature makes them an attractive solution for renewable energy systems,such as low-voltage input photovoltaic power systems and electric vehicle systems.However,they usually require more high voltage rating switches and flying capacitors along with boosting capability.Furthermore,they suffer from high pulse currents at the switching transients.Aiming to solve these issues,this article proposes a new self-balancing three-phase five-level inverter based on the switched-capacitor(5L-SCTPNPC),which reduces the dc voltage requirement.The number of active switches is relatively smaller and seven active switches are required per phase.Especially,a soft-charging circuit for FC is designed to limit the impulse charging current.Compared to conventional multilevel inverters,the proposed five-level inverter reduces dc bus voltage by 50%.Significantly,the voltage stress of FC and the switches in parallel with FC are all reduced by 50%in comparison with some existing similar boosting five-level active-neutral-point-clamped(5L-BANPC)inverters.The operating principles,modulation strategy,and the design of the FC and charging inductor are provided in detailly.A comprehensive comparison study has been made to highlight the merits of the proposed inverter.Finally,the simulations and experiments validate the feasibility of the proposed topology.展开更多
Renewable electricity-driven production of value-added sulfur and H_(2)via electrocatalytic H_(2)S decomposition represents a sustainable route to conventional thermocatalysis.Both the electrocatalyst and electrolyte ...Renewable electricity-driven production of value-added sulfur and H_(2)via electrocatalytic H_(2)S decomposition represents a sustainable route to conventional thermocatalysis.Both the electrocatalyst and electrolyte solution strongly impact the H_(2)S decomposition performance.Despite significant progress in developing sophisticated electrocatalysts,a well-designed electrolyte solution in conjunction with industrial catalysts is an attractive strategy to advance the industrialization process of electrocatalytic H_(2)S decomposition,but remains unexplored.Here,for the first time,we design a solid-liquid-gas three-phase indirect electrolysis system based on a kind of CS_(2)-N electrolyte solution and Ni-Mo_(2)C that can efficiently enable H_(2)S decomposition into valuable H_(2)and sulfur.Specifically,the solid-phase Ni-Mo_(2)C as a heterogeneous redox mediator presents excellent electrocatalytic efficiency for the H_(2)S removal efficiency of up to 99%,and the formation of liquid-phase sulfur product(CS_(2)-N electrolyte solution dissolves sulfur,yield up to 95%)with the generation of gas-phase H_(2)product(~1.32 mL min^(-1)),resulting in an interesting three-phase indirect electrolysis system.Remarkably,it enables the scale-up production(~6 g in a batch experiment)of sulfur with continuous operation for 120 h without attenuation.This work may inaugurate a new electrocatalytic H_(2)S decomposition avenue to explore porous metal materials and electrolyte systems in simultaneous production of value-added sulfur and H_(2).展开更多
The transient phenomena of re-oxidation and slag entrapment occurring in the tundish during the ladle change-over process have been proven detrimental to clean steel production.Therefore,an unsteady three-phase turbul...The transient phenomena of re-oxidation and slag entrapment occurring in the tundish during the ladle change-over process have been proven detrimental to clean steel production.Therefore,an unsteady three-phase turbulence model,coupling velocity,temperature,and phase field was established to study the effect of the ladle shroud immersion depth on the slag eye formation,slag entrainment,slag dragging,air dragging,and flow characteristics during the ladle change-over process of a two-strand tundish.The results showed that reducing the immersion depth decreases the high-velocity region area under the slag layer in the quasi-steady process.During the emptying stage,as the molten bath level gradually decreases,the outlet temperature exhibits a trend of initially decreasing and subsequently increasing across all three shroud immersion depths.However,under a 210 mm shroud immersion depth,molten slag and air are dragged into the shroud,forming slag droplets and causing significant fluctuations,with a maximum scalar velocity of 0.0764 m/s at the monitoring point.In the filling stage,air and molten slag are dragged into the molten bath,forming bubbles and slag droplets at an immersion depth of 210 mm.Bubbles are observed within the molten slag layer,which can readily cause an emulsification phenomenon,making it easier to be dragged as slag droplets.Additionally,the slag eye area measured under 210 mm immersion depth at 45 s is 0.303 m^(2),while the maximum scalar velocity of 2.4259 m/s is detected at 12 s.At an immersion depth of 360 mm,the average area of the slag eye is minimized to 0.06268 m2,with corresponding variances of 0.006753,representing the optimal immersion depth.展开更多
A three-phase reactor mathematical model was set up to simulate and design a three-phase bubble column reactor for direct synthesis of dimethyl ether （DME） from syngas, considering both the influence of part inert c...A three-phase reactor mathematical model was set up to simulate and design a three-phase bubble column reactor for direct synthesis of dimethyl ether （DME） from syngas, considering both the influence of part inert carrier backmixing on transfer and the influence of catalyst grain sedimentation on reaction. On the basis of this model, the influences of the size and reaction conditions of a 100000 t/a DME reactor on capacity were investigated. The optimized size of the 10000 t/a DME synthesis reactor was proposed as follows： diameter 3.2 m, height 20 m, built-in 400 tube heat exchanger （Ф 38×2 mm）, and inert heat carrier paraffin oil 68 t and catalyst 34.46 t. Reaction temperature and pressure were important factors influencing the reaction conversion for different size reactors. Under the condition of uniform catalyst concentration distribution, higher pressure and temperature were proposed to achieve a higher production capacity of DME. The best ratio of fresh syngas for DME synthesis was 2.04.展开更多
A modified internal-loop airlif reactor （MIALR） with a continuous slurry phase was studied to investigate the local hydrodynamic characteristics, including gas holdup, bubble size, bubble rise velocity and local mas...A modified internal-loop airlif reactor （MIALR） with a continuous slurry phase was studied to investigate the local hydrodynamic characteristics, including gas holdup, bubble size, bubble rise velocity and local mass transfer properties. Based on the analysis of geometrical construction and fluid properties of gas and slurry, MIALR was divided into six flow regions. In these flow regions, the local hydrodynamic characteristics were investigated over a wide range of operating variables. Furthermore, a new method was developed to measure the dissolved oxygen concentration. The volumetric mass-transfer coefficient in six flow regions was also calculated for comparison.展开更多
Local hydrodynamics of a gas–liquid–solid system,such as bubble circulation regime,gas holdup,liquid velocity and axial profile of solid concentration,are studied in a two-stage internal loop airlift reactor.Empiric...Local hydrodynamics of a gas–liquid–solid system,such as bubble circulation regime,gas holdup,liquid velocity and axial profile of solid concentration,are studied in a two-stage internal loop airlift reactor.Empirical correlations for gas holdup and liquid velocity are proposed to ease the reactor design and scale-up.Different bubble circulation regimes were displayed in the first(lower) and second(upper) stages.Increasing superficial gas velocity and solid loading can promote regime transition of the second stage,and the gas holdup of the second stage is higher than that of the lower stage.In addition,the effects of solid loading on bubble behaviour are experimentally investigated for each stage.It is found that bubble size in the downcomer decreases with the presence of solid particles,and bubble size distribution widens under higher superficial gas velocity and lower solid loading.展开更多
The local gas-phase flow characteristics such as local gas holdup(εg), local bubble velocity (V_b) and local bubble mean diameter(d_b) at a specified point in a gas-liquid-solid three-phase reversedflow jet loop reac...The local gas-phase flow characteristics such as local gas holdup(εg), local bubble velocity (V_b) and local bubble mean diameter(d_b) at a specified point in a gas-liquid-solid three-phase reversedflow jet loop reactor was experimentally investigated by a five-pointconductivity probe. The effects of gas jet flow rate, liquid jet flowrate, solid loading, nozzle diameter and axial position on the localεg, V_b and d_b profiles were discussed. The presence of solids atlow solid concentrations not only increased the local εg and V_b,but also decreased the local d_b. The optimum solid loading for themaximum local εg and V_b together with the minimum local d_b was0.16×10^-3 m^3, corresponding to a solid volume fraction ε_S＝2.5/100.展开更多
In this work, the effects of injecting an evaporating liquid jet into solid-gas flow are experimentally investigated. A new model （SHED model） and a supplementary model （spray model） have also been proposed to inv...In this work, the effects of injecting an evaporating liquid jet into solid-gas flow are experimentally investigated. A new model （SHED model） and a supplementary model （spray model） have also been proposed to investigate some flow-field characteristics in three-phase fluidized bed with the mean relative error 4.3% between model and measured results. Some experiments were conducted to study the influences of flow-field parameters such as liquid volumetric flow rate, injection velocity, jet angle and gas superficial velocity as well as solid mass flux on the jet penetration depth （JPD）. In addition, independent variables were experimentally employed to propose two empirical correlations for JPD by using multiple regression method and spray cone angle （SCA） by using dimensional analysis technique. The mean relative errors between the JPD and SCA correlations versus ex- perimental data were 7.5% and 3.9%, respectively. In addition, in order to identify the variable effect, a parametric study was carried out. Applying the proposed model can avoid direct use of expensive devices to measureJPD and to nredict dronlet size.展开更多
To achieve high power rating and low current harmonics of motor drive,this paper develops a dual three-phase open-winding permanent magnet synchronous motor(DTP-OW-PMSM)drive with the DC-link voltage ratio of 2:1:1.Ba...To achieve high power rating and low current harmonics of motor drive,this paper develops a dual three-phase open-winding permanent magnet synchronous motor(DTP-OW-PMSM)drive with the DC-link voltage ratio of 2:1:1.Based on this topology,this paper proposes a DTP four-level space vector pulse width modulation(DTP-FL SVPWM)strategy.First,two identical three-phase four-level space vector diagrams are constructed and divided.Then,three adjacent vectors nearest to the reference vector in each diagram are selected for the vector synthesis to guarantee high modulation precision and low switching frequency.Furthermore,to avoid the modulation error caused by the voltage deviation,the proposed DTP-FL SVPWM strategy is further optimized through unified duty ratio compensation(UDRC).The effectiveness of the proposed strategy is verified through experiments.展开更多
The growing demand for efficient high-power switching power supplies has spurred interest in advanced topologies.The three-phase VIENNA converter stands out for its high power factor,simplified structure,and robust pe...The growing demand for efficient high-power switching power supplies has spurred interest in advanced topologies.The three-phase VIENNA converter stands out for its high power factor,simplified structure,and robust performance.Current research focuses on its operational principles,control strategies,and behavior under various load conditions.Key considerations include component selection,thermal management,and EMI/EMC optimization.This topology finds applications across renewable energy systems,industrial equipment,telecommunications,and electric vehicle charging infrastructures.Comparative analyses with alternative topologies and cost-benefit evaluations are also addressed.Future developments are expected to emphasize the integration of wide-bandgap devices and advancements in digital control techniques to further enhance efficiency and system performance.展开更多
The dual three-phase PMSM(DTP-PMSM)drives have received wide attention at high-power high-efficiency applications due to their merits of high output current ability and copper-loss-free field excitation.Meanwhile,the ...The dual three-phase PMSM(DTP-PMSM)drives have received wide attention at high-power high-efficiency applications due to their merits of high output current ability and copper-loss-free field excitation.Meanwhile,the DTPPMSM drive provides higher fault-tolerant capability for highreliability applications,e.g.,pumps and actuators in aircraft.For high-power drives with limited switching frequencies and highspeed drives with large fundamental frequencies,the ratio of switching frequency to fundamental frequency,i.e.,the carrier ratio,is usually below 15,which would significantly degrade the control performance.The purpose of this paper is to review the recent work on the modulation and control schemes for improving the operation performance of DTP-PMSM drives with low carrier ratios.Specifically,three categories of methods,i.e.,the space vector modulation based control,the model predictive control(MPC),and the optimized pulse pattern(OPP)based control are reviewed with principles and performance.In addition,brief discussions regarding the comparison and future trends are presented for low-carrier-ratio(LCR)modulation and control schemes of DTP-PMSM drives.展开更多
Knowing the precise relationship between fuel loading and reactivity is essential for guiding reactor criticality extrapolation and online refueling in molten salt reactors(MSRs).This study aims to explore and explain...Knowing the precise relationship between fuel loading and reactivity is essential for guiding reactor criticality extrapolation and online refueling in molten salt reactors(MSRs).This study aims to explore and explain the linear relationship between reactivity and the reciprocal of uranium concentration in thermal-spectrum MSRs.By applying neutron balance theory,we analyzed the neutron absorption cross sections of various nuclides in single-lattice models with varying fuel concentrations.Our findings reveal a simple linear correlation between reactivity and the reciprocal of uranium concentration,which can be explained from the perspective of nuclear reaction cross sections that adhere to the 1/v law in the thermal neutron spectrum.Furthermore,we identified that the neutron absorption single-group cross sections of structural materials and carrier salts exhibit an approximately linear relationship with the fission single-group cross section of ^(235) U;similarly,the reciprocal of ^(235)U’s fission cross section exhibits an approximately linear relationship with uranium concentration.This linear relationship deviates as the volume fraction of molten salt increases,due to a greater proportion of neutrons being captured in the resonance energy spectrum.However,it remains valid for molten salt volume fractions up to 25%and demonstrates broad applicability in the physical design and operation of thermal molten salt reactors.展开更多
The electrochemical oxidation of biomass-derived platform molecule 5-hydroxymethylfurfural(HMF)represents a crucial pathway for green transformation into high-value chemicals,yet its reaction pathway selectivity,effic...The electrochemical oxidation of biomass-derived platform molecule 5-hydroxymethylfurfural(HMF)represents a crucial pathway for green transformation into high-value chemicals,yet its reaction pathway selectivity,efficiency,and catalyst stability are strongly dependent on the electrolyte pH environment.Under alkaline conditions,high OH−concentration facilitates preferential aldehyde group oxidation and efficient deprotonation,enabling highly efficient synthesis of 2,5-furandicarboxylic acid,but simultaneously induces HMF self-degradation and complicates product separation.As pH decreases,the reaction mechanism shifts toward enhanced hydroxymethyl oxidation,leading to intermediate accumulation(such as 5-hydroxymethyl-2-furancarboxylic acid,2,5-diformylfuran,and 5-formyl-2-furancarboxylic acid)with challenging selectivity control and significantly slowed reaction kinetics.This review comprehensively examines the systematic differences in HMF oxidation pathways and surface catalytic mechanisms across the full pH range from alkaline to acidic conditions.Addressing the distinct reaction characteristics and core challenges in alkaline,near-neutral,and acidic media,we systematically evaluate design strategies for high-efficiency electrocatalysts and explore reactor design aspects.Future research should focus on process integration(with tailored reactor design)for energy consumption reduction in alkaline systems,targeted synthesis of diverse oxidation products in near-neutral systems,and innovative catalyst development for acidic systems,thereby advancing the efficiency,selectivity,and practical application of HMF electrooxidation technologies across the entire pH spectrum through synergistic optimization of catalyst,reactor,and process.展开更多
Molten salt reactors,being the only reactor type among Generation Ⅳ advanced nuclear reactors that utilize liquid fuels,offer inherent safety,high-temperature,and low-pressure operation,as well as the capability for ...Molten salt reactors,being the only reactor type among Generation Ⅳ advanced nuclear reactors that utilize liquid fuels,offer inherent safety,high-temperature,and low-pressure operation,as well as the capability for online fuel reprocessing.However,the fuel-salt flow results in the decay of delayed neutron precursors(DNPs)outside the core,causing fluctuations in the effective delayed neutron fraction and consequently impacting the reactor reactivity.Particularly in accident scenarios—such as a combined pump shutdown and the inability to rapidly scram the reactor—the sole reliance on negative temperature feedback may cause a significant increase in core temperature,posing a threat to reactor safety.To address these problems,this paper introduces an innovative design for a passive fluid-driven suspended control rod(SCR)to dynamically compensate for reactivity fluctuations caused by DNPs flowing with the fuel.The control rod operates passively by leveraging the combined effects of gravity,buoyancy,and fluid dynamic forces,thereby eliminating the need for an external drive mechanism and enabling direct integration within the active region of the core.Using a 150 MWt thorium-based molten salt reactor as the reference design,we develop a mathematical model to systematically analyze the effects of key parameters—including the geometric dimensions and density of the SCR—on its performance.We examine its motion characteristics under different core flow conditions and assess its feasibility for the dynamic compensation of reactivity changes caused by fuel flow.The results of this study demonstrate that the SCR can effectively counteract reactivity fluctuations induced by fuel flow within molten salt reactors.A sensitivity analysis reveals that the SCR’s average density exerts a profound impact on its start-up flow threshold,channel flow rate,resistance to fuel density fluctuations,and response characteristics.This underscores the critical need to optimize this parameter.Moreover,by judiciously selecting the SCR’s length,number of deployed units,and the placement we can achieve the necessary reactivity control while maintaining a favorable balance between neutron economy and heat transfer performance.Ultimately,this paper provides an innovative solution for the passive reactivity control in molten salt reactors,offering significant potential for practical engineering applications.展开更多
The synthesis of propylene carbonate(PC)from CO_(2) and propylene oxide(PO)is a typical gas-liquid biphasic system,where gas-liquid mass transfer efficiency significantly influences CO_(2) cycloaddition reactions.Here...The synthesis of propylene carbonate(PC)from CO_(2) and propylene oxide(PO)is a typical gas-liquid biphasic system,where gas-liquid mass transfer efficiency significantly influences CO_(2) cycloaddition reactions.Here,we proposed a microchannel reaction system for the CO_(2) cycloaddition reaction catalyzed by ionic liquid within an aqueous environment.The effect of liquid flow rate,temperature and residence time on gas-liquid flow pattern,catalytic performance and mass transfer were systematically investigated.The results revealed that the PC generation rate reached 560.11 mmol·ml^(−1)·h^(−1)at a 50 cm of flow distance under reaction conditions of 105℃,2.5 MPa,QG=176 ml·min^(−1) and QL=0.3 ml·min^(−1).Variations in mass transfer rate and reaction rate at different flow distances were experimentally studied.The reaction efficiency gradually decreased with increasing flow distance,which were attributed to the reduction of mass transfer caused by decreasing bubble velocity.Optimizing bubble velocity at an appropriate position enhanced reaction efficiency by improving mass transfer,achieving a 97.7%PC yield within 2.85 min.Furthermore,a kinetic model coupling intrinsic kinetics with gas-liquid mass transfer was developed for CO_(2) cycloaddition reaction.The kinetic model was applied to predict PC reaction rates in microchannel reactors at various temperatures and liquid flow rates,achieving an average relative error of 9.6%.展开更多
Laser-induced aerosols,predominantly submicron in size,pose significant environmental and health risks during the decommissioning of nuclear reactors.This study experimentally investigated the removal of laser-generat...Laser-induced aerosols,predominantly submicron in size,pose significant environmental and health risks during the decommissioning of nuclear reactors.This study experimentally investigated the removal of laser-generated aerosol particles using a water spray system integrated with an innovative system for pre-injecting electrically charged mist in our facility.To simulate aerosol generation in reactor decommissioning,a high-power laser was used to irradiate various materials(including stainless steel,carbon steel,and concrete),generating aerosol particles that were agglomerated with injected water mist and subsequently scavenged by water spray.Experimental results demonstrate enhanced aerosol removal via aerosol-mist agglomeration,with charged mist significantly improving particle capture by increasing wettability and size.The average improvements for the stainless steel,carbon steel,and concrete were 40%,44%,and 21%,respectively.The results of experiments using charged mist with different polarities(both positive and negative)and different surface coatings reveal that the dominant polarity of aerosols varies with the irradiated materials,influenced by their crystal structure and electron emission properties.Notably,surface coatings such as ZrO_(2)and CeO_(2)were found to possibly alter aerosol charging characteristics,thereby affecting aerosol removal efficiency with charged mist configurations.The innovative aerosol-mist agglomeration approach shows promise in mitigating radiation exposure,ensuring environmental safety,and reducing contaminated water during reactor dismantling.This study contributes critical knowledge for the development of advanced aerosol management strategies for nuclear reactor decommissioning.The understanding obtained in this work is also expected to be useful for various environmental and chemical engineering applications such as gas decontamination,air purification,and pollution control.展开更多
One of the main issues in designing optimum tapered cascades for uranium enrichment for annual fuel production in a power reactor is whether to employ large(fat)or small(thin)cascades.What will be the permissible and ...One of the main issues in designing optimum tapered cascades for uranium enrichment for annual fuel production in a power reactor is whether to employ large(fat)or small(thin)cascades.What will be the permissible and optimal ranges of the number of machines that can be used in a cascade?For the first time,the permissible and optimal ranges of the number of gas centrifuges that can be utilized in a cascade were investigated using two types of centrifuges,and the performance of small and large tapered cascades was discussed.The particle swarm optimization algorithm(PSO)has been used to optimize tapered cascades.The results show:(1)For the first centrifuge,41 cascades(91≤n≤4897)and for the second centrifuge,49 cascades(18≤n≤3839)with small and large sizes can be used in enrichment facilities,and the best cascade for them has 530(with 23 stages)and 39(with 7 stages)centrifuges,respectively.(2)For both centrifuges,when 600≤n(number of centrifuges=n),the large cascade performance changes are relatively insignificant.(3)For both types of gas centrifuges,the annual los s of separation power in enrichment facilities is approximately 1.25%-4.82%of the total separation work required.展开更多
Correction to:Nuclear Science and Techniques(2025)36:111 https://doi.org/10.1007/s41365-025-01681-9.In the sentence beginning‘The weights of the parameters used for the…’in this article,the text‘RCSs’should have ...Correction to:Nuclear Science and Techniques(2025)36:111 https://doi.org/10.1007/s41365-025-01681-9.In the sentence beginning‘The weights of the parameters used for the…’in this article,the text‘RCSs’should have read‘SCRs’.In Table 7 of this article,the column header ρ_fuel was incorrect and should have read CPv_fuel.For completeness and transparency,the old incorrect version and the corrected version of Table 7 are displayed below.展开更多
Electrocatalytic oxidation is a promising technology for wastewater treatment,but poor mass transfer and low current efficiency impaded its engineering applications.To address these issues,researchers have developed f...Electrocatalytic oxidation is a promising technology for wastewater treatment,but poor mass transfer and low current efficiency impaded its engineering applications.To address these issues,researchers have developed flow-through electrochemical reactors(FERs)primarily based on porous electrodes,where the pore structure significantly impacts the electrochemical reaction.Therefore,this study systematically investigated the impact of different pore sizes on the fluid dynamics,current potential distribution,mass transfer processes,and degradation performance of FERs.Computational Fluid Dynamics(CFD)results indicated that smaller pore sizes(10μm,30μm,and 60μm)significantly enhanced convective effects within the fluid,reduced short fluid paths and dead volume regions within the microchannels,and facilitated mass transfer processes.Additionally,smaller pore sizes were conducive to a uniform distribution of current density.Furthermore,Fe(CN)_(6)^(4−)oxidation experiments revealed that the current density at a pore size of 160μm was notably lower than that at 10μm,indicating slower mass transfer of Fe(CN)_(6)^(4−)within larger channels.Calculations based on experimental results demonstrated that the mass transfer rate at a pore size of 10μm was six times than that at 160μm,further confirming the enhancing effect of smaller pore sizes on the mass transfer process.Lastly,experiments on tetracycline degradation showed that at a residence time of 90 s,the removal efficiencies of tetracycline were 80%and 39.1%for porous electrodes with pore sizes of 10μm and 160μm,respectively,demonstrating the superior removal efficiency of smaller pore sizes for tetracycline degradation.展开更多
Unlike previous theories with velocity and/or elastic modulus averaging, we use a three-phase porous rock physics model developed by Santos for analyzing the seismic response of two immiscible fluids in saturated poro...Unlike previous theories with velocity and/or elastic modulus averaging, we use a three-phase porous rock physics model developed by Santos for analyzing the seismic response of two immiscible fluids in saturated porous media. Considering reservoir reference pressure and coupling drag of two fluids in pores, the effects of frequency, porosity, and gas saturation on the phase velocities of the P-and S-waves are discussed in detail under field conditions. The effects of porosity and gas saturation on Vp/Vs are also provided. The data for our numerical experiments are from a sample of deep volcanic rock from Daqing. The numerical results show that the frequency dispersion effect can be ignored for deep volcanic rocks with low porosity and low permeability. It is concluded that for deep volcanic rocks the effect of gas content in pores on Vp/Vs is negligible but the effect of porosity is significant when there is a certain amount of water contained in the pores. The accurate estimate of lithology and porosity in this case is relatively more important.展开更多
基金supported by the National Natural Science Foundation of China(51977069)the National Natural Science Foundation Youth Project of China(52107195)the First Key Research and JieBang Headed Program,Hunan Province,China(2021GK1250).
文摘Switched-capacitor/flying capacitor(FC)based multilevel converters have been gaining higher attention for their voltage-boosting ability.This feature makes them an attractive solution for renewable energy systems,such as low-voltage input photovoltaic power systems and electric vehicle systems.However,they usually require more high voltage rating switches and flying capacitors along with boosting capability.Furthermore,they suffer from high pulse currents at the switching transients.Aiming to solve these issues,this article proposes a new self-balancing three-phase five-level inverter based on the switched-capacitor(5L-SCTPNPC),which reduces the dc voltage requirement.The number of active switches is relatively smaller and seven active switches are required per phase.Especially,a soft-charging circuit for FC is designed to limit the impulse charging current.Compared to conventional multilevel inverters,the proposed five-level inverter reduces dc bus voltage by 50%.Significantly,the voltage stress of FC and the switches in parallel with FC are all reduced by 50%in comparison with some existing similar boosting five-level active-neutral-point-clamped(5L-BANPC)inverters.The operating principles,modulation strategy,and the design of the FC and charging inductor are provided in detailly.A comprehensive comparison study has been made to highlight the merits of the proposed inverter.Finally,the simulations and experiments validate the feasibility of the proposed topology.
基金supported by the National Natural Science Foundation of China(No.22278439 and 21776313).
文摘Renewable electricity-driven production of value-added sulfur and H_(2)via electrocatalytic H_(2)S decomposition represents a sustainable route to conventional thermocatalysis.Both the electrocatalyst and electrolyte solution strongly impact the H_(2)S decomposition performance.Despite significant progress in developing sophisticated electrocatalysts,a well-designed electrolyte solution in conjunction with industrial catalysts is an attractive strategy to advance the industrialization process of electrocatalytic H_(2)S decomposition,but remains unexplored.Here,for the first time,we design a solid-liquid-gas three-phase indirect electrolysis system based on a kind of CS_(2)-N electrolyte solution and Ni-Mo_(2)C that can efficiently enable H_(2)S decomposition into valuable H_(2)and sulfur.Specifically,the solid-phase Ni-Mo_(2)C as a heterogeneous redox mediator presents excellent electrocatalytic efficiency for the H_(2)S removal efficiency of up to 99%,and the formation of liquid-phase sulfur product(CS_(2)-N electrolyte solution dissolves sulfur,yield up to 95%)with the generation of gas-phase H_(2)product(~1.32 mL min^(-1)),resulting in an interesting three-phase indirect electrolysis system.Remarkably,it enables the scale-up production(~6 g in a batch experiment)of sulfur with continuous operation for 120 h without attenuation.This work may inaugurate a new electrocatalytic H_(2)S decomposition avenue to explore porous metal materials and electrolyte systems in simultaneous production of value-added sulfur and H_(2).
基金supported by the National Natural Science Foundation of China(Nos.52422408 and 52171031)the Liaoning Xingliao Talents-Top-notch Young Talents Project(No.XLYC2203064)+1 种基金the Excellent Youth Fund of Liaoning Natural Science Foundation(No.2023JH3/10200001)the Fundamental Research Funds for the Central Universities(No.N2425004).
文摘The transient phenomena of re-oxidation and slag entrapment occurring in the tundish during the ladle change-over process have been proven detrimental to clean steel production.Therefore,an unsteady three-phase turbulence model,coupling velocity,temperature,and phase field was established to study the effect of the ladle shroud immersion depth on the slag eye formation,slag entrainment,slag dragging,air dragging,and flow characteristics during the ladle change-over process of a two-strand tundish.The results showed that reducing the immersion depth decreases the high-velocity region area under the slag layer in the quasi-steady process.During the emptying stage,as the molten bath level gradually decreases,the outlet temperature exhibits a trend of initially decreasing and subsequently increasing across all three shroud immersion depths.However,under a 210 mm shroud immersion depth,molten slag and air are dragged into the shroud,forming slag droplets and causing significant fluctuations,with a maximum scalar velocity of 0.0764 m/s at the monitoring point.In the filling stage,air and molten slag are dragged into the molten bath,forming bubbles and slag droplets at an immersion depth of 210 mm.Bubbles are observed within the molten slag layer,which can readily cause an emulsification phenomenon,making it easier to be dragged as slag droplets.Additionally,the slag eye area measured under 210 mm immersion depth at 45 s is 0.303 m^(2),while the maximum scalar velocity of 2.4259 m/s is detected at 12 s.At an immersion depth of 360 mm,the average area of the slag eye is minimized to 0.06268 m2,with corresponding variances of 0.006753,representing the optimal immersion depth.
基金This work was supported by the National Basic Research Program of China (2005CB221205)
文摘A three-phase reactor mathematical model was set up to simulate and design a three-phase bubble column reactor for direct synthesis of dimethyl ether （DME） from syngas, considering both the influence of part inert carrier backmixing on transfer and the influence of catalyst grain sedimentation on reaction. On the basis of this model, the influences of the size and reaction conditions of a 100000 t/a DME reactor on capacity were investigated. The optimized size of the 10000 t/a DME synthesis reactor was proposed as follows： diameter 3.2 m, height 20 m, built-in 400 tube heat exchanger （Ф 38×2 mm）, and inert heat carrier paraffin oil 68 t and catalyst 34.46 t. Reaction temperature and pressure were important factors influencing the reaction conversion for different size reactors. Under the condition of uniform catalyst concentration distribution, higher pressure and temperature were proposed to achieve a higher production capacity of DME. The best ratio of fresh syngas for DME synthesis was 2.04.
文摘A modified internal-loop airlif reactor （MIALR） with a continuous slurry phase was studied to investigate the local hydrodynamic characteristics, including gas holdup, bubble size, bubble rise velocity and local mass transfer properties. Based on the analysis of geometrical construction and fluid properties of gas and slurry, MIALR was divided into six flow regions. In these flow regions, the local hydrodynamic characteristics were investigated over a wide range of operating variables. Furthermore, a new method was developed to measure the dissolved oxygen concentration. The volumetric mass-transfer coefficient in six flow regions was also calculated for comparison.
基金Supported by the State Key Laboratory of Chemical Engineering(SKL-ChE-16B01)China Postdoctoral Science Foundation(2016M601263)
文摘Local hydrodynamics of a gas–liquid–solid system,such as bubble circulation regime,gas holdup,liquid velocity and axial profile of solid concentration,are studied in a two-stage internal loop airlift reactor.Empirical correlations for gas holdup and liquid velocity are proposed to ease the reactor design and scale-up.Different bubble circulation regimes were displayed in the first(lower) and second(upper) stages.Increasing superficial gas velocity and solid loading can promote regime transition of the second stage,and the gas holdup of the second stage is higher than that of the lower stage.In addition,the effects of solid loading on bubble behaviour are experimentally investigated for each stage.It is found that bubble size in the downcomer decreases with the presence of solid particles,and bubble size distribution widens under higher superficial gas velocity and lower solid loading.
基金Supported by the National Natural Science Foundation of China (No. 29706006) and the General Corporation of Petrochemical Engineering of China (No.X598021).
文摘The local gas-phase flow characteristics such as local gas holdup(εg), local bubble velocity (V_b) and local bubble mean diameter(d_b) at a specified point in a gas-liquid-solid three-phase reversedflow jet loop reactor was experimentally investigated by a five-pointconductivity probe. The effects of gas jet flow rate, liquid jet flowrate, solid loading, nozzle diameter and axial position on the localεg, V_b and d_b profiles were discussed. The presence of solids atlow solid concentrations not only increased the local εg and V_b,but also decreased the local d_b. The optimum solid loading for themaximum local εg and V_b together with the minimum local d_b was0.16×10^-3 m^3, corresponding to a solid volume fraction ε_S＝2.5/100.
文摘In this work, the effects of injecting an evaporating liquid jet into solid-gas flow are experimentally investigated. A new model （SHED model） and a supplementary model （spray model） have also been proposed to investigate some flow-field characteristics in three-phase fluidized bed with the mean relative error 4.3% between model and measured results. Some experiments were conducted to study the influences of flow-field parameters such as liquid volumetric flow rate, injection velocity, jet angle and gas superficial velocity as well as solid mass flux on the jet penetration depth （JPD）. In addition, independent variables were experimentally employed to propose two empirical correlations for JPD by using multiple regression method and spray cone angle （SCA） by using dimensional analysis technique. The mean relative errors between the JPD and SCA correlations versus ex- perimental data were 7.5% and 3.9%, respectively. In addition, in order to identify the variable effect, a parametric study was carried out. Applying the proposed model can avoid direct use of expensive devices to measureJPD and to nredict dronlet size.
基金supported in part by the National Natural Science Foundation of China under Grant 62303333in part by the Project of Hetao Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone under Grant HZQB-KCZYB-2020083.
文摘To achieve high power rating and low current harmonics of motor drive,this paper develops a dual three-phase open-winding permanent magnet synchronous motor(DTP-OW-PMSM)drive with the DC-link voltage ratio of 2:1:1.Based on this topology,this paper proposes a DTP four-level space vector pulse width modulation(DTP-FL SVPWM)strategy.First,two identical three-phase four-level space vector diagrams are constructed and divided.Then,three adjacent vectors nearest to the reference vector in each diagram are selected for the vector synthesis to guarantee high modulation precision and low switching frequency.Furthermore,to avoid the modulation error caused by the voltage deviation,the proposed DTP-FL SVPWM strategy is further optimized through unified duty ratio compensation(UDRC).The effectiveness of the proposed strategy is verified through experiments.
文摘The growing demand for efficient high-power switching power supplies has spurred interest in advanced topologies.The three-phase VIENNA converter stands out for its high power factor,simplified structure,and robust performance.Current research focuses on its operational principles,control strategies,and behavior under various load conditions.Key considerations include component selection,thermal management,and EMI/EMC optimization.This topology finds applications across renewable energy systems,industrial equipment,telecommunications,and electric vehicle charging infrastructures.Comparative analyses with alternative topologies and cost-benefit evaluations are also addressed.Future developments are expected to emphasize the integration of wide-bandgap devices and advancements in digital control techniques to further enhance efficiency and system performance.
基金supported by the National Key Research and Development Program of China under the grant of 2022YFB3403100。
文摘The dual three-phase PMSM(DTP-PMSM)drives have received wide attention at high-power high-efficiency applications due to their merits of high output current ability and copper-loss-free field excitation.Meanwhile,the DTPPMSM drive provides higher fault-tolerant capability for highreliability applications,e.g.,pumps and actuators in aircraft.For high-power drives with limited switching frequencies and highspeed drives with large fundamental frequencies,the ratio of switching frequency to fundamental frequency,i.e.,the carrier ratio,is usually below 15,which would significantly degrade the control performance.The purpose of this paper is to review the recent work on the modulation and control schemes for improving the operation performance of DTP-PMSM drives with low carrier ratios.Specifically,three categories of methods,i.e.,the space vector modulation based control,the model predictive control(MPC),and the optimized pulse pattern(OPP)based control are reviewed with principles and performance.In addition,brief discussions regarding the comparison and future trends are presented for low-carrier-ratio(LCR)modulation and control schemes of DTP-PMSM drives.
基金supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2020261)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA02010000)the Young Potential Program of the Shanghai Institute of Applied Physics,Chinese Academy of Sciences(No.SINAP-YXJH-202412)。
文摘Knowing the precise relationship between fuel loading and reactivity is essential for guiding reactor criticality extrapolation and online refueling in molten salt reactors(MSRs).This study aims to explore and explain the linear relationship between reactivity and the reciprocal of uranium concentration in thermal-spectrum MSRs.By applying neutron balance theory,we analyzed the neutron absorption cross sections of various nuclides in single-lattice models with varying fuel concentrations.Our findings reveal a simple linear correlation between reactivity and the reciprocal of uranium concentration,which can be explained from the perspective of nuclear reaction cross sections that adhere to the 1/v law in the thermal neutron spectrum.Furthermore,we identified that the neutron absorption single-group cross sections of structural materials and carrier salts exhibit an approximately linear relationship with the fission single-group cross section of ^(235) U;similarly,the reciprocal of ^(235)U’s fission cross section exhibits an approximately linear relationship with uranium concentration.This linear relationship deviates as the volume fraction of molten salt increases,due to a greater proportion of neutrons being captured in the resonance energy spectrum.However,it remains valid for molten salt volume fractions up to 25%and demonstrates broad applicability in the physical design and operation of thermal molten salt reactors.
基金supported by the National Key R&D Program of China(2023YFA1507400)the National Natural Science Foundation of China(Grant No.22325805,22441010,22408203)+2 种基金Beijing Natural Science Foundation(Grant No.JQ22003)the Haihe Laboratory of Sustainable Chemical Transformations(24HHWCSS00007)Tsinghua University Dushi Program,and Sinopec Group(PR20232572).
文摘The electrochemical oxidation of biomass-derived platform molecule 5-hydroxymethylfurfural(HMF)represents a crucial pathway for green transformation into high-value chemicals,yet its reaction pathway selectivity,efficiency,and catalyst stability are strongly dependent on the electrolyte pH environment.Under alkaline conditions,high OH−concentration facilitates preferential aldehyde group oxidation and efficient deprotonation,enabling highly efficient synthesis of 2,5-furandicarboxylic acid,but simultaneously induces HMF self-degradation and complicates product separation.As pH decreases,the reaction mechanism shifts toward enhanced hydroxymethyl oxidation,leading to intermediate accumulation(such as 5-hydroxymethyl-2-furancarboxylic acid,2,5-diformylfuran,and 5-formyl-2-furancarboxylic acid)with challenging selectivity control and significantly slowed reaction kinetics.This review comprehensively examines the systematic differences in HMF oxidation pathways and surface catalytic mechanisms across the full pH range from alkaline to acidic conditions.Addressing the distinct reaction characteristics and core challenges in alkaline,near-neutral,and acidic media,we systematically evaluate design strategies for high-efficiency electrocatalysts and explore reactor design aspects.Future research should focus on process integration(with tailored reactor design)for energy consumption reduction in alkaline systems,targeted synthesis of diverse oxidation products in near-neutral systems,and innovative catalyst development for acidic systems,thereby advancing the efficiency,selectivity,and practical application of HMF electrooxidation technologies across the entire pH spectrum through synergistic optimization of catalyst,reactor,and process.
基金supported by Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2020261)Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA02010000)the Young Potential Program of Shanghai Institute of Applied Physics,Chinese Academy of Sciences(No.SINAP-YXJH-202412).
文摘Molten salt reactors,being the only reactor type among Generation Ⅳ advanced nuclear reactors that utilize liquid fuels,offer inherent safety,high-temperature,and low-pressure operation,as well as the capability for online fuel reprocessing.However,the fuel-salt flow results in the decay of delayed neutron precursors(DNPs)outside the core,causing fluctuations in the effective delayed neutron fraction and consequently impacting the reactor reactivity.Particularly in accident scenarios—such as a combined pump shutdown and the inability to rapidly scram the reactor—the sole reliance on negative temperature feedback may cause a significant increase in core temperature,posing a threat to reactor safety.To address these problems,this paper introduces an innovative design for a passive fluid-driven suspended control rod(SCR)to dynamically compensate for reactivity fluctuations caused by DNPs flowing with the fuel.The control rod operates passively by leveraging the combined effects of gravity,buoyancy,and fluid dynamic forces,thereby eliminating the need for an external drive mechanism and enabling direct integration within the active region of the core.Using a 150 MWt thorium-based molten salt reactor as the reference design,we develop a mathematical model to systematically analyze the effects of key parameters—including the geometric dimensions and density of the SCR—on its performance.We examine its motion characteristics under different core flow conditions and assess its feasibility for the dynamic compensation of reactivity changes caused by fuel flow.The results of this study demonstrate that the SCR can effectively counteract reactivity fluctuations induced by fuel flow within molten salt reactors.A sensitivity analysis reveals that the SCR’s average density exerts a profound impact on its start-up flow threshold,channel flow rate,resistance to fuel density fluctuations,and response characteristics.This underscores the critical need to optimize this parameter.Moreover,by judiciously selecting the SCR’s length,number of deployed units,and the placement we can achieve the necessary reactivity control while maintaining a favorable balance between neutron economy and heat transfer performance.Ultimately,this paper provides an innovative solution for the passive reactivity control in molten salt reactors,offering significant potential for practical engineering applications.
基金supported by the National Key Projects for Fundamental Research and development of China(2020YFA0710202)the China Postdoctoral Science Foundation(2024M761567)Shandong Postdoctoral Science Foundation(SDCX-ZG-202400271).
文摘The synthesis of propylene carbonate(PC)from CO_(2) and propylene oxide(PO)is a typical gas-liquid biphasic system,where gas-liquid mass transfer efficiency significantly influences CO_(2) cycloaddition reactions.Here,we proposed a microchannel reaction system for the CO_(2) cycloaddition reaction catalyzed by ionic liquid within an aqueous environment.The effect of liquid flow rate,temperature and residence time on gas-liquid flow pattern,catalytic performance and mass transfer were systematically investigated.The results revealed that the PC generation rate reached 560.11 mmol·ml^(−1)·h^(−1)at a 50 cm of flow distance under reaction conditions of 105℃,2.5 MPa,QG=176 ml·min^(−1) and QL=0.3 ml·min^(−1).Variations in mass transfer rate and reaction rate at different flow distances were experimentally studied.The reaction efficiency gradually decreased with increasing flow distance,which were attributed to the reduction of mass transfer caused by decreasing bubble velocity.Optimizing bubble velocity at an appropriate position enhanced reaction efficiency by improving mass transfer,achieving a 97.7%PC yield within 2.85 min.Furthermore,a kinetic model coupling intrinsic kinetics with gas-liquid mass transfer was developed for CO_(2) cycloaddition reaction.The kinetic model was applied to predict PC reaction rates in microchannel reactors at various temperatures and liquid flow rates,achieving an average relative error of 9.6%.
基金financial support from the Nuclear Energy Science&Technology and Human Resource Development Project of the Japan Atomic Energy Agency/Collaborative Laboratories for Advanced Decommissioning Science(No.R04I034)The author Ruicong Xu appreciates the scholarship(financial support)from the China Scholarship Council(CSC,No.202106380073).
文摘Laser-induced aerosols,predominantly submicron in size,pose significant environmental and health risks during the decommissioning of nuclear reactors.This study experimentally investigated the removal of laser-generated aerosol particles using a water spray system integrated with an innovative system for pre-injecting electrically charged mist in our facility.To simulate aerosol generation in reactor decommissioning,a high-power laser was used to irradiate various materials(including stainless steel,carbon steel,and concrete),generating aerosol particles that were agglomerated with injected water mist and subsequently scavenged by water spray.Experimental results demonstrate enhanced aerosol removal via aerosol-mist agglomeration,with charged mist significantly improving particle capture by increasing wettability and size.The average improvements for the stainless steel,carbon steel,and concrete were 40%,44%,and 21%,respectively.The results of experiments using charged mist with different polarities(both positive and negative)and different surface coatings reveal that the dominant polarity of aerosols varies with the irradiated materials,influenced by their crystal structure and electron emission properties.Notably,surface coatings such as ZrO_(2)and CeO_(2)were found to possibly alter aerosol charging characteristics,thereby affecting aerosol removal efficiency with charged mist configurations.The innovative aerosol-mist agglomeration approach shows promise in mitigating radiation exposure,ensuring environmental safety,and reducing contaminated water during reactor dismantling.This study contributes critical knowledge for the development of advanced aerosol management strategies for nuclear reactor decommissioning.The understanding obtained in this work is also expected to be useful for various environmental and chemical engineering applications such as gas decontamination,air purification,and pollution control.
文摘One of the main issues in designing optimum tapered cascades for uranium enrichment for annual fuel production in a power reactor is whether to employ large(fat)or small(thin)cascades.What will be the permissible and optimal ranges of the number of machines that can be used in a cascade?For the first time,the permissible and optimal ranges of the number of gas centrifuges that can be utilized in a cascade were investigated using two types of centrifuges,and the performance of small and large tapered cascades was discussed.The particle swarm optimization algorithm(PSO)has been used to optimize tapered cascades.The results show:(1)For the first centrifuge,41 cascades(91≤n≤4897)and for the second centrifuge,49 cascades(18≤n≤3839)with small and large sizes can be used in enrichment facilities,and the best cascade for them has 530(with 23 stages)and 39(with 7 stages)centrifuges,respectively.(2)For both centrifuges,when 600≤n(number of centrifuges=n),the large cascade performance changes are relatively insignificant.(3)For both types of gas centrifuges,the annual los s of separation power in enrichment facilities is approximately 1.25%-4.82%of the total separation work required.
文摘Correction to:Nuclear Science and Techniques(2025)36:111 https://doi.org/10.1007/s41365-025-01681-9.In the sentence beginning‘The weights of the parameters used for the…’in this article,the text‘RCSs’should have read‘SCRs’.In Table 7 of this article,the column header ρ_fuel was incorrect and should have read CPv_fuel.For completeness and transparency,the old incorrect version and the corrected version of Table 7 are displayed below.
基金supported by the National Natural Science Foundation of China(Nos.U22A20241 and 21876105)Shaanxi“Scientist&Engineer”Team(No.2023KXJ-131)Xianyang Key S&T Special Projects(No.L2023-ZDKJ-QCY-SXGG-GY-007).
文摘Electrocatalytic oxidation is a promising technology for wastewater treatment,but poor mass transfer and low current efficiency impaded its engineering applications.To address these issues,researchers have developed flow-through electrochemical reactors(FERs)primarily based on porous electrodes,where the pore structure significantly impacts the electrochemical reaction.Therefore,this study systematically investigated the impact of different pore sizes on the fluid dynamics,current potential distribution,mass transfer processes,and degradation performance of FERs.Computational Fluid Dynamics(CFD)results indicated that smaller pore sizes(10μm,30μm,and 60μm)significantly enhanced convective effects within the fluid,reduced short fluid paths and dead volume regions within the microchannels,and facilitated mass transfer processes.Additionally,smaller pore sizes were conducive to a uniform distribution of current density.Furthermore,Fe(CN)_(6)^(4−)oxidation experiments revealed that the current density at a pore size of 160μm was notably lower than that at 10μm,indicating slower mass transfer of Fe(CN)_(6)^(4−)within larger channels.Calculations based on experimental results demonstrated that the mass transfer rate at a pore size of 10μm was six times than that at 160μm,further confirming the enhancing effect of smaller pore sizes on the mass transfer process.Lastly,experiments on tetracycline degradation showed that at a residence time of 90 s,the removal efficiencies of tetracycline were 80%and 39.1%for porous electrodes with pore sizes of 10μm and 160μm,respectively,demonstrating the superior removal efficiency of smaller pore sizes for tetracycline degradation.
文摘Unlike previous theories with velocity and/or elastic modulus averaging, we use a three-phase porous rock physics model developed by Santos for analyzing the seismic response of two immiscible fluids in saturated porous media. Considering reservoir reference pressure and coupling drag of two fluids in pores, the effects of frequency, porosity, and gas saturation on the phase velocities of the P-and S-waves are discussed in detail under field conditions. The effects of porosity and gas saturation on Vp/Vs are also provided. The data for our numerical experiments are from a sample of deep volcanic rock from Daqing. The numerical results show that the frequency dispersion effect can be ignored for deep volcanic rocks with low porosity and low permeability. It is concluded that for deep volcanic rocks the effect of gas content in pores on Vp/Vs is negligible but the effect of porosity is significant when there is a certain amount of water contained in the pores. The accurate estimate of lithology and porosity in this case is relatively more important.
