Accurate prediction of the frictional pressure drop is important for the design and operation of subsea oil and gas transporting system considering the length of the pipeline. The applicability of the correlations to ...Accurate prediction of the frictional pressure drop is important for the design and operation of subsea oil and gas transporting system considering the length of the pipeline. The applicability of the correlations to pipeline-riser flow needs evaluation since the flow condition in pipeline-riser is quite different from the original data where they were derived from. In the present study, a comprehensive evaluation of 24prevailing correlation in predicting frictional pressure drop is carried out based on experimentally measured data of air-water and air-oil two-phase flows in pipeline-riser. Experiments are performed in a system having different configuration of pipeline-riser with the inclination of the downcomer varied from-2°to-5°to investigated the effect of the elbow on the frictional pressure drop in the riser. The inlet gas velocity ranges from 0.03 to 6.2 m/s, and liquid velocity varies from 0.02 to 1.3 m/s. A total of885 experimental data points including 782 on air-water flows and 103 on air-oil flows are obtained and used to access the prediction ability of the correlations. Comparison of the predicted results with the measured data indicate that a majority of the investigated correlations under-predict the pressure drop on severe slugging. The result of this study highlights the requirement of new method considering the effect of pipe layout on the frictional pressure drop.展开更多
In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different para...In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different parameters investigated by means of observation and a high-speed camera.Since the appearance of spiral flow makes the distribution of twophase flow more complicated,the flow patterns appearing in the experiments were divided into the Spiral Wavy Stratified Flow(SWS),the Spiral Bubble Flow(SB),the Spiral Slug Flow(SS),the Spiral Linear Flow(SL),the Spiral Axial Flow(SA),and the Spiral Dispersed Flow(SD) by the observations and with reference to the predecessors' research achievements.A flow pattern map has been drawn up.The influence of velocity,vane angle and vane area on flow pattern conversion boundary and pressure drop has been studied,with a solid foundation laid for the future research work.展开更多
Tetracycline(TC)is an antibiotic mainly used in livestock production and respiratory infection.Traditional methods are not effective in removing TC from solution.In this study,TC was degraded by gas–liquid plasma in ...Tetracycline(TC)is an antibiotic mainly used in livestock production and respiratory infection.Traditional methods are not effective in removing TC from solution.In this study,TC was degraded by gas–liquid plasma in the presence of rGO-TiO_(2)in solution.The rGO-TiO_(2)was prepared by modified hummers and hydrothermal method.The electrical and optical properties of the gas–liquid discharge plasma were studied and the produced long-lived reactive species were analyzed by spectrophotometer.The degradation efficiency of TC was improved by 41.4%after plasma treatment for 12 min in presence of 30 mg l-1 r GO-TiO_(2)compared to that with plasma alone.The degradation efficiency increased with increasing discharge power,but as the initial concentration was increased from 20 to 80 mg l-1,the degradation efficiency of TC decreased.The initial p H had no significant effect on the degradation of TC.The intermediate products were determined by UV–vis spectrophotometry and ESI(+)–MS,and the degradation mechanism was analyzed.The reactive species,including O_(3),·OH,and H_(2)O_(2),etc.,produced in the plasma/catalyst system attracted electron-rich functional groups(amino group,aromatic ring,and double bond).Therefore,the gas–liquid plasma/catalyst system could be an effective and promising method for pharmaceutical wastewater treatment in future.展开更多
Atmospheric pressure plasma technology is gaining increasing importance because it is a simple and tunable synthesis process for the production of metallic nanoparticles.In addition to the development of the power sup...Atmospheric pressure plasma technology is gaining increasing importance because it is a simple and tunable synthesis process for the production of metallic nanoparticles.In addition to the development of the power supply,improving the reactor is also one of the main strategies to enhanee the utility.In this study,a simple reactor for the gas-liquid discharge plasma induced by argon gas was applied to synthesize silver nanopailicles from silver nitrate(AgNO3)in solution.An AC power supply with a peak voltage of 3.5 kV was used.The frequency and on-time were set to 50 kHz and 2.5“s,respectively.The oscilloscope showed that the rising time was approximately 2“s.The ethanol was used as the source for the reactive reducing agent.No more additional comp on ents existed in the solution during the discharge and neither of the electrodes was in contact with the treated solution.The temperature in creased by 10°C within 1 min without a cooling system.Carbon was the main impurity and was expected to be produced from the decomposition of the organics under the plasma.The elevated temperature decreased the organic by-products by evaporation and could also decrease the production of carbon.Transmission electron microscopy showed that the spherical silver nanoparticles with a size of approximately 10 nm were synthesized with a crystal structure and that a low concentration of ethanol prefers the production of the mono-dispersed colloid.展开更多
The plasma characteristics of a gas-liquid phase discharge reactor were investigated by optical and electrical methods.The nozzle-cylinder electrode in the discharge reactor was supplied witha negative nanosecond puls...The plasma characteristics of a gas-liquid phase discharge reactor were investigated by optical and electrical methods.The nozzle-cylinder electrode in the discharge reactor was supplied witha negative nanosecond pulsed generator.The optical emission spectrum diagnosis revealed that OH（A2∑＋ → X2Π,306–309 nm）,N32（CΠ→B3Πg,337 nm）,O（3p5p→3s-5s-0,777.2 nm）and O（3p3p→3s3s0,844.6 nm）were produced in the discharge plasma channels.The electron temperature（Te）was calculated from the emission relative intensity ratio between the atomic O 777.2 nm and 844.6 nm,and it increased with the applied voltage and the pulsed frequency and fell within the range of 0.5–0.8 e V.The gas temperature（Tg）that was measured by Lifbase was in a range from 400 K to 600 K.展开更多
Sustainable nitrogen fixation driven by renewable energy sources under mild conditions has been widely sought to replace the industrial Haber-Bosch process.The fixation of nitrogen in the form of NO_(x)^(-)and NH_4^(+...Sustainable nitrogen fixation driven by renewable energy sources under mild conditions has been widely sought to replace the industrial Haber-Bosch process.The fixation of nitrogen in the form of NO_(x)^(-)and NH_4^(+)into aqueous solutions using electricity-driven gas-liquid discharge plasma is considered a promising prescription.In this paper,a scalable bubble discharge excited by nanosecond pulse power is employed for nitrogen fixation in the liquid phase.The nitrogen fixation performance and the mechanisms are analyzed by varying the power supply parameters,working gas flow rate and composition.The results show that an increase in voltage and frequency can result in an enhanced NO_(3)^(-)yield.Increases in the gas flow rate can result in inadequate activation of the working gas,which together with more inefficient mass transfer efficiencies can reduce the yield.The addition of O_(2) effectively elevates NO_(3)^(-)production while simultaneously inhibiting NH_4^(+) production.The addition of H_(2)O vapor increases the production of OH and H,thereby promoting the generation of reactive nitrogen and enhancing the yield of nitrogen fixation.However,the excessive addition of O_(2) and H_(2)O vapor results in negative effect on the yield of nitrogen fixation,due to the significant weakening of the discharge intensity.The optimal nitrogen fixation yield was up to 16.5 μmol/min,while the optimal energy consumption was approximately 21.3 MJ/mol in this study.Finally,the mechanism related to nitrogen fixation is discussed through the optical emission spectral(OES) information in conjunction with the simulation of energy loss paths in the plasma by BOLSIG+.The work advances knowledge of the effect of parameter variations on nitrogen fixation by gas-liquid discharge for higher yield and energy production.展开更多
A typical quinolones antibiotic ciprofloxacin(CIP) in aqueous solution was degraded by a gas–liquid discharge non-thermal plasma system. The discharge plasma power and the emission intensity of the excited reactive s...A typical quinolones antibiotic ciprofloxacin(CIP) in aqueous solution was degraded by a gas–liquid discharge non-thermal plasma system. The discharge plasma power and the emission intensity of the excited reactive species(RS) generated in the gas phase were detected by the oscilloscope and the optical emission spectroscopy. The effects of various parameters on CIP degradation, i.e. input powers, initial concentrations addition of radical scavengers and p H values were investigated. With the increase of discharge power, the degradation efficiency increased but the energy efficiency significantly reduced. The degradation efficiency also reduced under high concentration of initial CIP conditions due to the competitive reactions between the plasma-induced RS with the degradation intermediates of CIP. Different radical scavengers(isopropanol and CCl_4) on ·OH and H· were added into the reaction system and the oxidation effects of ·OH radicals have been proved with high degradation capacity on CIP.Moreover, the long-term degradation effect on CIP in the plasma-treated aqueous solution proved that the long-lived RS(H_2O_2 and O_3, etc) might play key roles on the stay effect through multiple aqueous reactions leading to production of ·OH. The degradation intermediates were determined by the method of electrospray ionization(+)-mass spectroscopy, and the possible degradation mechanism were presented.展开更多
We are interested in a viscous two-phase gas-liquid mixture model relevant for modeling of well control operations within the petroleum industry. We focus on a simplified mixture model and provide an existence result ...We are interested in a viscous two-phase gas-liquid mixture model relevant for modeling of well control operations within the petroleum industry. We focus on a simplified mixture model and provide an existence result within an appropriate class of weak solutions. We demonstrate that upper and lower limits can be obtained for the gas and liquid masses which ensure that transition to single-phase regions do not occur. This is used together with appropriate a prior estimates to obtain convergence to a weak solution for a sequence of approximate solutions corresponding to mollified initial data. Moreover, by imposing an additional regularity condition on the initial masses, a uniqueness result is obtained. The framework herein seems useful for further investigations of more realistic versions of the gas-liquid model that take into account different flow regimes.展开更多
Cold atmospheric plasmas(CAPs)have attracted considerable interest in the field of plasma medicine.Generated reactive species such as hydroxyl(OH)species play an important role in applications of CAPs.Transportation o...Cold atmospheric plasmas(CAPs)have attracted considerable interest in the field of plasma medicine.Generated reactive species such as hydroxyl(OH)species play an important role in applications of CAPs.Transportation of OH species towards the target and distribution of these OH species in the plasma plume play an important role in the applications of plasma medicine.In the present work,a computational model was built to simulate the transportation and distribution of OH species in CAP discharges,which was based on the level set method to dynamically track the propagation of plasma carrier gas in air.A reaction term was incorporated for the OH species.The OH species tended to diffuse around the main stream of the carrier gas,and thus covered larger radial and axial distances.A CAP discharge onto a skin layer led to the largest accumulation of OH species at the central part of the exposed area.The distribution of OH species on the skin was asymmetric,which agreed with experiments.The computational model itself and the obtained results would be useful for future development of plasma medicine.展开更多
This paper reports a 3-d numerical simulation system to analyze the complicated flow in plasma reactors for coal gasification, which involve complex chemical reaction, two-phase flow and plasma effect. On the basis of...This paper reports a 3-d numerical simulation system to analyze the complicated flow in plasma reactors for coal gasification, which involve complex chemical reaction, two-phase flow and plasma effect. On the basis of analytic results, the distribution of the density, temperature and components' concentration are obtained and a different plasma reactor configuration is proposed to optimize the flow parameters. The numerical simulation results show an improved conversion ratio of the coal gasification. Different kinds of chemical reaction models are used to simulate the complex flow inside the reactor. It can be concluded that the numerical simulation system can be very useful for the design and optimization of the plasma reactor.展开更多
An atmospheric-pressure dielectric barrier discharge （DBD） gas-liquid cold plasma was employed to synthesize Cu-doped TiO~ nanoparticles in an aqueous solution with the assistance of [C2MIM]BF4 ionic liquid （IL） a...An atmospheric-pressure dielectric barrier discharge （DBD） gas-liquid cold plasma was employed to synthesize Cu-doped TiO~ nanoparticles in an aqueous solution with the assistance of [C2MIM]BF4 ionic liquid （IL） and using air as the working gas. The influences of the discharge voltage, IL and the amount of copper nitrite were investigated. X-ray diffraction, N2 adsorption-desorption measurements and UV-Vis spectroscopy were adopted to characterize the samples. The results showed that the specific surface area of TiO2 was promoted with Cu-doping （from 57.6 m^2.g^-1 to 106.2 m^2.g^-1 with 3% Cu-doping）, and the content of anatase was increased. Besides, the band gap energy of TiO~ with Cu-doping decreased according to the UV-Vis spec- troscopy test. The 3%Cu-IL-TiO2 samples showed the highest eificiency in degrading methylene blue （MB） dye solutions under simulated sunlight with an apparent rate constant of 0.0223 min-1, which was 1.2 times higher than that of non-doped samples. According to the characterization results, the reasons for the high photocatalytic activity were discussed.展开更多
During deepwater managed pressure drilling(MPD),the gas kick may occur in abnormally high-pressure formations.If the traditional well control method is adopted,the treatment time is long and the advantage of early gas...During deepwater managed pressure drilling(MPD),the gas kick may occur in abnormally high-pressure formations.If the traditional well control method is adopted,the treatment time is long and the advantage of early gas kick detection of MPD is lost.The dynamic managed pressure well-control(MPWC)method can be used to rapidly treat gas kick in deepwater MPD.In this paper,considering the effect of large-variable-diameter annulus and complex wellbore temperature in deepwater drilling,a simplified model of non-isothermal gas-liquid two-phase flow was established for dynamic deepwater MPWC simulation.Using this model,the response characteristics of outlet flow and wellhead backpressure were investigated.The results indicated that the gas fraction,outlet liquid flow rate,pit gain and wellhead backpressure presented complex alternating characteristics when gas moved upwards in the wellbore due to the large-variable-diameter annulus.The outlet liquid flow rate would be lower than the inlet flow rate and the pit gain would decrease before the gas moved to the wellhead.The variation trend of the wellhead backpressure was consistent with that of the pit gain.When the gas-liquid mixture passed through the choke,the expansion or compression of the gas caused part of the choke pressure drop to be supplemented or unloaded,delaying the response rate of the wellhead backpressure.The wellbore temperature,borehole diameter and seawater depth had different effects on outlet flow rate,pit gain and wellhead backpressure.This research could provide a new idea for well control methods in deepwater managed pressure drilling.展开更多
In order to study the influence of gas-liquid two-phase flow on the performance and internal flow field of a centrifugal pump,the steady three-dimensional flow with different gas volume fractions was simulated by appl...In order to study the influence of gas-liquid two-phase flow on the performance and internal flow field of a centrifugal pump,the steady three-dimensional flow with different gas volume fractions was simulated by applying the Reynolds-average N-S equation and mixture gas-liquid two-phase flow model,and the compressibility of gas was taken into consideration in the simulation. Then the centrifugal pump characteristic and the gas distribution law in different gas volume fractions were analyzed. The computational results show that gas volume fraction has a certain influence on the performance of the centrifugal pump,and the efficiency and head of the pump are on the decline with the increase of it.Static pressure in the impeller increases in the radial direction,but the pressure gradient in the flow direction is different under the different gas volume fractions. The gas volume is distributed mainly in the ipsilateral direction of impeller back shroud in the flow channel of the volute. On the suction side of the blade inlet there is an obvious low-pressure area,which causes bubbles agglutination and higher gas volume fraction. With the gas entering passage flow,gas volume fraction in the suction decreases and the pressure surface rises gradually. Higher gas volume fraction causes air blocking phenomenon in the flow passage and the discharge capacity reduces. The increase of gas volume makes the turbulent motion within the impeller more and more intense,which leads to more and more energy loss.展开更多
In this paper, the AC-excited helium discharges generated between the powered needle electrode enclosed in a conical quartz tube and the grounded de-ionized water electrode are investigated. The current and voltage wa...In this paper, the AC-excited helium discharges generated between the powered needle electrode enclosed in a conical quartz tube and the grounded de-ionized water electrode are investigated. The current and voltage waveforms exhibit a transition from the glow-like to streamer-like mode discharges, which forms a stable cone-shaped structure at the gas-liquid interface. In this region, the air and water vapor diffusion initiate various physical-chemical processes leading to substantial changes of the primary species emission intensities （e.g., OH, N2, NO, and O） and the rotational temperatures. The experimentally measured rotational temperature at the gas-liquid interface is 870 K from the Nz（C-B） band with a power input of 26 W. With the prolongation of the discharge time, significant changes in the discharge voltage and current, discharge emission patterns, instantaneous concentrations of the secondary species （e.g., H202, NO2, and NO3） in the liquid phase, pH values and electrical conductivities of the liquids are observed experimentally. The present study is helpful for deepening the understandings to the basic physical-chemical processes in the discharges in contact with liquids, especially to those occurring in the vicinity of the gas-liquid interface, and also for promoting existing and potential applications of such type of discharges in the fields of environmental protection, biomedicine, agriculture, and so on.展开更多
基金the support of the Opening Fund of State Key Laboratory of Multiphase Flow in Power Engineering(SKLMF-KF-2102)。
文摘Accurate prediction of the frictional pressure drop is important for the design and operation of subsea oil and gas transporting system considering the length of the pipeline. The applicability of the correlations to pipeline-riser flow needs evaluation since the flow condition in pipeline-riser is quite different from the original data where they were derived from. In the present study, a comprehensive evaluation of 24prevailing correlation in predicting frictional pressure drop is carried out based on experimentally measured data of air-water and air-oil two-phase flows in pipeline-riser. Experiments are performed in a system having different configuration of pipeline-riser with the inclination of the downcomer varied from-2°to-5°to investigated the effect of the elbow on the frictional pressure drop in the riser. The inlet gas velocity ranges from 0.03 to 6.2 m/s, and liquid velocity varies from 0.02 to 1.3 m/s. A total of885 experimental data points including 782 on air-water flows and 103 on air-oil flows are obtained and used to access the prediction ability of the correlations. Comparison of the predicted results with the measured data indicate that a majority of the investigated correlations under-predict the pressure drop on severe slugging. The result of this study highlights the requirement of new method considering the effect of pipe layout on the frictional pressure drop.
基金supported by the National Natural Science Foundation of China (Grant number 51776015)
文摘In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different parameters investigated by means of observation and a high-speed camera.Since the appearance of spiral flow makes the distribution of twophase flow more complicated,the flow patterns appearing in the experiments were divided into the Spiral Wavy Stratified Flow(SWS),the Spiral Bubble Flow(SB),the Spiral Slug Flow(SS),the Spiral Linear Flow(SL),the Spiral Axial Flow(SA),and the Spiral Dispersed Flow(SD) by the observations and with reference to the predecessors' research achievements.A flow pattern map has been drawn up.The influence of velocity,vane angle and vane area on flow pattern conversion boundary and pressure drop has been studied,with a solid foundation laid for the future research work.
基金financially supported by National Natural Science Foundation of China(Nos.51777206 and 51541807)Natural Science Foundation of Anhui Province(Nos.1908085MA29,1708085MB47 and 1708085MA13)+4 种基金Doctoral Fund of Ministry of Education of China(No.2017M612058)Specialized Research Fund for the Doctoral Program of Hefei University of Technology(No.JZ2016HGBZ0769)Chinese Academy of Sciences under Grant No.DSJJ-14-YY02Science and Technology Cooperation Program between China and Finland(No.2017YFE0115200)Hong Kong Research Grants Council(RGC)General Research Funds(GRF)(No.City U 11205617)。
文摘Tetracycline(TC)is an antibiotic mainly used in livestock production and respiratory infection.Traditional methods are not effective in removing TC from solution.In this study,TC was degraded by gas–liquid plasma in the presence of rGO-TiO_(2)in solution.The rGO-TiO_(2)was prepared by modified hummers and hydrothermal method.The electrical and optical properties of the gas–liquid discharge plasma were studied and the produced long-lived reactive species were analyzed by spectrophotometer.The degradation efficiency of TC was improved by 41.4%after plasma treatment for 12 min in presence of 30 mg l-1 r GO-TiO_(2)compared to that with plasma alone.The degradation efficiency increased with increasing discharge power,but as the initial concentration was increased from 20 to 80 mg l-1,the degradation efficiency of TC decreased.The initial p H had no significant effect on the degradation of TC.The intermediate products were determined by UV–vis spectrophotometry and ESI(+)–MS,and the degradation mechanism was analyzed.The reactive species,including O_(3),·OH,and H_(2)O_(2),etc.,produced in the plasma/catalyst system attracted electron-rich functional groups(amino group,aromatic ring,and double bond).Therefore,the gas–liquid plasma/catalyst system could be an effective and promising method for pharmaceutical wastewater treatment in future.
文摘Atmospheric pressure plasma technology is gaining increasing importance because it is a simple and tunable synthesis process for the production of metallic nanoparticles.In addition to the development of the power supply,improving the reactor is also one of the main strategies to enhanee the utility.In this study,a simple reactor for the gas-liquid discharge plasma induced by argon gas was applied to synthesize silver nanopailicles from silver nitrate(AgNO3)in solution.An AC power supply with a peak voltage of 3.5 kV was used.The frequency and on-time were set to 50 kHz and 2.5“s,respectively.The oscilloscope showed that the rising time was approximately 2“s.The ethanol was used as the source for the reactive reducing agent.No more additional comp on ents existed in the solution during the discharge and neither of the electrodes was in contact with the treated solution.The temperature in creased by 10°C within 1 min without a cooling system.Carbon was the main impurity and was expected to be produced from the decomposition of the organics under the plasma.The elevated temperature decreased the organic by-products by evaporation and could also decrease the production of carbon.Transmission electron microscopy showed that the spherical silver nanoparticles with a size of approximately 10 nm were synthesized with a crystal structure and that a low concentration of ethanol prefers the production of the mono-dispersed colloid.
基金supported by National Natural Science Foundation of China(Grant No.51207089)
文摘The plasma characteristics of a gas-liquid phase discharge reactor were investigated by optical and electrical methods.The nozzle-cylinder electrode in the discharge reactor was supplied witha negative nanosecond pulsed generator.The optical emission spectrum diagnosis revealed that OH（A2∑＋ → X2Π,306–309 nm）,N32（CΠ→B3Πg,337 nm）,O（3p5p→3s-5s-0,777.2 nm）and O（3p3p→3s3s0,844.6 nm）were produced in the discharge plasma channels.The electron temperature（Te）was calculated from the emission relative intensity ratio between the atomic O 777.2 nm and 844.6 nm,and it increased with the applied voltage and the pulsed frequency and fell within the range of 0.5–0.8 e V.The gas temperature（Tg）that was measured by Lifbase was in a range from 400 K to 600 K.
基金National Natural Science Foundation of China (Grant Nos. 52277151 and 51907088)。
文摘Sustainable nitrogen fixation driven by renewable energy sources under mild conditions has been widely sought to replace the industrial Haber-Bosch process.The fixation of nitrogen in the form of NO_(x)^(-)and NH_4^(+)into aqueous solutions using electricity-driven gas-liquid discharge plasma is considered a promising prescription.In this paper,a scalable bubble discharge excited by nanosecond pulse power is employed for nitrogen fixation in the liquid phase.The nitrogen fixation performance and the mechanisms are analyzed by varying the power supply parameters,working gas flow rate and composition.The results show that an increase in voltage and frequency can result in an enhanced NO_(3)^(-)yield.Increases in the gas flow rate can result in inadequate activation of the working gas,which together with more inefficient mass transfer efficiencies can reduce the yield.The addition of O_(2) effectively elevates NO_(3)^(-)production while simultaneously inhibiting NH_4^(+) production.The addition of H_(2)O vapor increases the production of OH and H,thereby promoting the generation of reactive nitrogen and enhancing the yield of nitrogen fixation.However,the excessive addition of O_(2) and H_(2)O vapor results in negative effect on the yield of nitrogen fixation,due to the significant weakening of the discharge intensity.The optimal nitrogen fixation yield was up to 16.5 μmol/min,while the optimal energy consumption was approximately 21.3 MJ/mol in this study.Finally,the mechanism related to nitrogen fixation is discussed through the optical emission spectral(OES) information in conjunction with the simulation of energy loss paths in the plasma by BOLSIG+.The work advances knowledge of the effect of parameter variations on nitrogen fixation by gas-liquid discharge for higher yield and energy production.
基金financially supported by National Natural Science Foundation of China (Nos. 51777206 and 51541807)Natural Science Foundation of Anhui Province (Nos. 1708085MB47 and 1708085MA13)+2 种基金Foundation of Anhui Province Key Laboratory of Medical Physics and Technology (No. LMPT2017Y7BP0U1581)Doctoral Fund of Ministry of Education of China (No. 2017M612058)Specialized Research Fund for the Doctoral Program of Hefei University of Technology (Nos. JZ2016HGBZ0768, JZ2016HGBZ0769, and JZ2017HGBZ0944)
文摘A typical quinolones antibiotic ciprofloxacin(CIP) in aqueous solution was degraded by a gas–liquid discharge non-thermal plasma system. The discharge plasma power and the emission intensity of the excited reactive species(RS) generated in the gas phase were detected by the oscilloscope and the optical emission spectroscopy. The effects of various parameters on CIP degradation, i.e. input powers, initial concentrations addition of radical scavengers and p H values were investigated. With the increase of discharge power, the degradation efficiency increased but the energy efficiency significantly reduced. The degradation efficiency also reduced under high concentration of initial CIP conditions due to the competitive reactions between the plasma-induced RS with the degradation intermediates of CIP. Different radical scavengers(isopropanol and CCl_4) on ·OH and H· were added into the reaction system and the oxidation effects of ·OH radicals have been proved with high degradation capacity on CIP.Moreover, the long-term degradation effect on CIP in the plasma-treated aqueous solution proved that the long-lived RS(H_2O_2 and O_3, etc) might play key roles on the stay effect through multiple aqueous reactions leading to production of ·OH. The degradation intermediates were determined by the method of electrospray ionization(+)-mass spectroscopy, and the possible degradation mechanism were presented.
文摘We are interested in a viscous two-phase gas-liquid mixture model relevant for modeling of well control operations within the petroleum industry. We focus on a simplified mixture model and provide an existence result within an appropriate class of weak solutions. We demonstrate that upper and lower limits can be obtained for the gas and liquid masses which ensure that transition to single-phase regions do not occur. This is used together with appropriate a prior estimates to obtain convergence to a weak solution for a sequence of approximate solutions corresponding to mollified initial data. Moreover, by imposing an additional regularity condition on the initial masses, a uniqueness result is obtained. The framework herein seems useful for further investigations of more realistic versions of the gas-liquid model that take into account different flow regimes.
基金funded by National Natural Science Foundation of China (Nos. U1632145, 81573093 and 81227902)funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) and Jiangsu Provincial Key Laboratory of Radiation Medicine and Protection, China Postdoctoral Science Foundation (No. 2016M592584)Strategic Research Grant 7004641 from City University of Hong Kong
文摘Cold atmospheric plasmas(CAPs)have attracted considerable interest in the field of plasma medicine.Generated reactive species such as hydroxyl(OH)species play an important role in applications of CAPs.Transportation of OH species towards the target and distribution of these OH species in the plasma plume play an important role in the applications of plasma medicine.In the present work,a computational model was built to simulate the transportation and distribution of OH species in CAP discharges,which was based on the level set method to dynamically track the propagation of plasma carrier gas in air.A reaction term was incorporated for the OH species.The OH species tended to diffuse around the main stream of the carrier gas,and thus covered larger radial and axial distances.A CAP discharge onto a skin layer led to the largest accumulation of OH species at the central part of the exposed area.The distribution of OH species on the skin was asymmetric,which agreed with experiments.The computational model itself and the obtained results would be useful for future development of plasma medicine.
基金The project supported by the National 973 Project of China (No. G1999022106)
文摘This paper reports a 3-d numerical simulation system to analyze the complicated flow in plasma reactors for coal gasification, which involve complex chemical reaction, two-phase flow and plasma effect. On the basis of analytic results, the distribution of the density, temperature and components' concentration are obtained and a different plasma reactor configuration is proposed to optimize the flow parameters. The numerical simulation results show an improved conversion ratio of the coal gasification. Different kinds of chemical reaction models are used to simulate the complex flow inside the reactor. It can be concluded that the numerical simulation system can be very useful for the design and optimization of the plasma reactor.
基金supported by National Natural Science Foundation of China(Nos.21173028,11505019)the Science and Technology Research Project of Liaoning Provincial Education Department(No.L2013464)+2 种基金the Scientific Research Foundation for the Doctor of Liaoning Province(No.20131004)the Program for Liaoning Excellent Talents in University(No.LR2012042)Dalian Jinzhou New District Science and Technology Plan Project(No.KJCX-ZTPY-2014-0001)
文摘An atmospheric-pressure dielectric barrier discharge （DBD） gas-liquid cold plasma was employed to synthesize Cu-doped TiO~ nanoparticles in an aqueous solution with the assistance of [C2MIM]BF4 ionic liquid （IL） and using air as the working gas. The influences of the discharge voltage, IL and the amount of copper nitrite were investigated. X-ray diffraction, N2 adsorption-desorption measurements and UV-Vis spectroscopy were adopted to characterize the samples. The results showed that the specific surface area of TiO2 was promoted with Cu-doping （from 57.6 m^2.g^-1 to 106.2 m^2.g^-1 with 3% Cu-doping）, and the content of anatase was increased. Besides, the band gap energy of TiO~ with Cu-doping decreased according to the UV-Vis spec- troscopy test. The 3%Cu-IL-TiO2 samples showed the highest eificiency in degrading methylene blue （MB） dye solutions under simulated sunlight with an apparent rate constant of 0.0223 min-1, which was 1.2 times higher than that of non-doped samples. According to the characterization results, the reasons for the high photocatalytic activity were discussed.
基金supported by the Youth Program of National Natural Science Foundation of China(Grant No.52104012)the Key Program of the National Natural Science Foundation of China(Grant No.51734010)+2 种基金the China Postdoctoral Science Foundation(Grant No.2021M693494)Science Foundation of China University of Petroleum,Beijing(Grant No.2462020XKBH011)the Key Natural Science Projects of Scientific Research Plan in Colleges and Universities of Xinjiang Uygur Autonomous Region(Grant No.XJEDU2021I028)。
文摘During deepwater managed pressure drilling(MPD),the gas kick may occur in abnormally high-pressure formations.If the traditional well control method is adopted,the treatment time is long and the advantage of early gas kick detection of MPD is lost.The dynamic managed pressure well-control(MPWC)method can be used to rapidly treat gas kick in deepwater MPD.In this paper,considering the effect of large-variable-diameter annulus and complex wellbore temperature in deepwater drilling,a simplified model of non-isothermal gas-liquid two-phase flow was established for dynamic deepwater MPWC simulation.Using this model,the response characteristics of outlet flow and wellhead backpressure were investigated.The results indicated that the gas fraction,outlet liquid flow rate,pit gain and wellhead backpressure presented complex alternating characteristics when gas moved upwards in the wellbore due to the large-variable-diameter annulus.The outlet liquid flow rate would be lower than the inlet flow rate and the pit gain would decrease before the gas moved to the wellhead.The variation trend of the wellhead backpressure was consistent with that of the pit gain.When the gas-liquid mixture passed through the choke,the expansion or compression of the gas caused part of the choke pressure drop to be supplemented or unloaded,delaying the response rate of the wellhead backpressure.The wellbore temperature,borehole diameter and seawater depth had different effects on outlet flow rate,pit gain and wellhead backpressure.This research could provide a new idea for well control methods in deepwater managed pressure drilling.
基金The National Natural Science Foundation of China(51679196,51879216,51339005)
文摘In order to study the influence of gas-liquid two-phase flow on the performance and internal flow field of a centrifugal pump,the steady three-dimensional flow with different gas volume fractions was simulated by applying the Reynolds-average N-S equation and mixture gas-liquid two-phase flow model,and the compressibility of gas was taken into consideration in the simulation. Then the centrifugal pump characteristic and the gas distribution law in different gas volume fractions were analyzed. The computational results show that gas volume fraction has a certain influence on the performance of the centrifugal pump,and the efficiency and head of the pump are on the decline with the increase of it.Static pressure in the impeller increases in the radial direction,but the pressure gradient in the flow direction is different under the different gas volume fractions. The gas volume is distributed mainly in the ipsilateral direction of impeller back shroud in the flow channel of the volute. On the suction side of the blade inlet there is an obvious low-pressure area,which causes bubbles agglutination and higher gas volume fraction. With the gas entering passage flow,gas volume fraction in the suction decreases and the pressure surface rises gradually. Higher gas volume fraction causes air blocking phenomenon in the flow passage and the discharge capacity reduces. The increase of gas volume makes the turbulent motion within the impeller more and more intense,which leads to more and more energy loss.
基金supported by the Major Science and Technology Program for Water Pollution Control and Treatment(No.2014ZX07215-001)partly by National Natural Science Foundation of China(Nos.11475103,51578309)the Chinese Scholarship Council for the financial assistance of my PhD program in Tsinghua University of China
文摘In this paper, the AC-excited helium discharges generated between the powered needle electrode enclosed in a conical quartz tube and the grounded de-ionized water electrode are investigated. The current and voltage waveforms exhibit a transition from the glow-like to streamer-like mode discharges, which forms a stable cone-shaped structure at the gas-liquid interface. In this region, the air and water vapor diffusion initiate various physical-chemical processes leading to substantial changes of the primary species emission intensities （e.g., OH, N2, NO, and O） and the rotational temperatures. The experimentally measured rotational temperature at the gas-liquid interface is 870 K from the Nz（C-B） band with a power input of 26 W. With the prolongation of the discharge time, significant changes in the discharge voltage and current, discharge emission patterns, instantaneous concentrations of the secondary species （e.g., H202, NO2, and NO3） in the liquid phase, pH values and electrical conductivities of the liquids are observed experimentally. The present study is helpful for deepening the understandings to the basic physical-chemical processes in the discharges in contact with liquids, especially to those occurring in the vicinity of the gas-liquid interface, and also for promoting existing and potential applications of such type of discharges in the fields of environmental protection, biomedicine, agriculture, and so on.
