Results of experimental research of the mixing process of coaxial flows in a pipe with swirled peripheral jet are presented in this paper. Distribution of temperature and concentration of gases on the axis and wall of...Results of experimental research of the mixing process of coaxial flows in a pipe with swirled peripheral jet are presented in this paper. Distribution of temperature and concentration of gases on the axis and wall of the channel under the influence of such factors as the regime flow, ratio of density of flows and swirl degree of the peripheral jet are studied. Research of temperature, swirl angle, circulation in cross sections along with the channel have shown that their distributions have the jet-like character and are described by known dependences for the layer of mixture.展开更多
In recent years,research investigations have focused on the substantial freshwater storage in the Beaufort Gyre(BG)region due to climate change.Despite active mesoscale eddies in the area,a notable gap in understandin...In recent years,research investigations have focused on the substantial freshwater storage in the Beaufort Gyre(BG)region due to climate change.Despite active mesoscale eddies in the area,a notable gap in understanding the three-dimensional structure and induced transport has been observed.This study concentrates on the Canada Basin in the western Arctic Ocean,specifically examining a subsurface anticyclonic eddy(SAE)sampled by a Mooring A in the BG region.Hybrid Coordinate Ocean Model(HYCOM)analysis data reveal its lifecycle from February 15 to March 15,2017,marked by initiation,development,maturity,decay,and termination stages.This work extends the finding of SAE passing through Mooring A by examining its overall effects,spatiotemporal variations,and swirl transport.SAE generation through baroclinic instability,which contributes to the westward tilt of the vertical axis,is also confirmed in this study.Swirl transport induced by SAE is predominantly eastward and downward due to its trajectory and background flow.SAE temporarily weakens stratification and extends the subsurface depth but demonstrates transient effects.Moreover,SAE transports upper-layer freshwater,Pacific Winter Water,and Atlantic Water downward,emphasizing its potential influence on freshwater redistribution in the Canadian Basin.This research provides valuable insights into mesoscale eddy dynamics,revealing their role in modulating the upper water mass in the BG region.展开更多
The electromagnetic swirling flow in nozzle(EMSFN)technique is designed to mitigate the adverse effects of unstable and uneven flow within the submerged entry nozzle in continuous casting.Utilizing electromagnetic for...The electromagnetic swirling flow in nozzle(EMSFN)technique is designed to mitigate the adverse effects of unstable and uneven flow within the submerged entry nozzle in continuous casting.Utilizing electromagnetic forces,EMSFN stabilizes the flow within the nozzle,leading to a more controlled flow in the mold.Numerical simulations were used to quantitatively analyze the magnetic and flow fields in a slab continuous casting system under EMSFN.Results indicate that EMSFN significantly stabilizes the outflow from the nozzle,with stability increasing with higher current intensity.At 10,000 Ampere-turns(At)of the coil,meniscus fluctuations were unstable.They stabilized at 13,000 At,with minimal changes observed beyond this point.The optimal current intensity for stable mold flow,at a casting speed of 1.56 m/min,is 13,000 At.These findings confirm the effectiveness of EMSFN in stabilizing the internal flow field of the slab mold and determining optimal operational current intensity.展开更多
Controlling molten steel flow in the mold and stabilizing the meniscus are critical challenges during the continuous casting,directly impacting the surface quality and internal quality of the final steel slab product....Controlling molten steel flow in the mold and stabilizing the meniscus are critical challenges during the continuous casting,directly impacting the surface quality and internal quality of the final steel slab product.The effects of electromagnetic swirling flow in nozzle(EMSFN)technology on molten steel flow in the mold during slab continuous casting under various casting speeds were investigated.A real-time adjustable EMSFN was developed,and a three-dimensional unsteady Reynolds-averaged Navier–Stokes turbulence mathematical model was established to simulate the flow field within the mold.The results demonstrate that the EMSFN effectively stabilizes the outflow from nozzle,reduces the impact depth and surface velocity of the molten steel,mitigates meniscus fluctuations,and promotes stable flow within the mold.However,a certain matching relationship exists between the casting speed and the current intensity.For the experimental medium-thick slab specifications,the optimal current intensities were found to be 100,130,and 200 A at casting speeds of 1.0,1.5,and 2.0 m/min,respectively.EMSFN can optimize the mold flow field under different casting speeds,providing theoretical support for improving the quality of continuously cast slab products.展开更多
An experimental investigation is conducted to evaluate the performance and the stalling process of a fan subjected to inlet swirls,as well as the effectiveness of an Impedance Boundary-Controlled(IBC)Casing Treatment(...An experimental investigation is conducted to evaluate the performance and the stalling process of a fan subjected to inlet swirls,as well as the effectiveness of an Impedance Boundary-Controlled(IBC)Casing Treatment(CT)on the stall margin recovery.An operating cycle is proposed based on the hysteresis effect of harmonic flap oscillation of airfoils and parallel compressor theory to explain the pressure characteristic of the fan under twin swirl inlets.Twin swirls are observed to reduce the stall margin of the fan,and the circumferential location where the spike is detected turns to the intersection area of the twin swirl.The IBC CT is proven to extend the stall margin of the fan for 12.7%–22.3%when subjected to inlet swirls with an efficiency loss of around 1%.The IBC CT helps to reduce the size of the operating cycle of the fan by redistributing the blade loading and adding the system damping to dissipate the perturbation energy.展开更多
BACKGROUND Intracerebral hemorrhage(ICH)comprises 9%-27%of stroke patients.Hematoma expansion(HE)occurs in approximately 20%of patients following ICH,typically within the first 24 hours.HE increases mortality and long...BACKGROUND Intracerebral hemorrhage(ICH)comprises 9%-27%of stroke patients.Hematoma expansion(HE)occurs in approximately 20%of patients following ICH,typically within the first 24 hours.HE increases mortality and long-term disability in these patients and is being investigated as a therapeutic target to improve the outcome in these patients by limiting HE.Non-contrast computed tomography(NCCT)has potential in predicting HE,which can identify the individuals at risk.AIM To evaluate NCCT markers for predicting HE in patients with ICH and to develop a simple,practical grading system for risk stratification.METHODS This prospective observational study evaluated 192 patients with spontaneous ICH who underwent a baseline NCCT within four hours of admission,followed by a follow-up scan after six hours or earlier if there was clinical deterioration.Hematoma volumes and imaging characteristics that predicted HE were evaluated.A simple five-point grading system score was created to predict HE.In RESULTS Of the 192 patients studied,HE was seen in 106(55.2%).The mean baseline hematoma volume was significantly greater among patients in the HE group(44.1 mL)compared to those in the non-HE group(12.2 mL),with a P-value<0.05.Additionally,imaging biomarkers such as the island sign,swirl sign,and black hole sign were observed with significantly higher frequency in the HE group relative to the non-HE cohort(all P-values<0.05).The island sign was strongly associated with HE[odds ratio(OR)13.7;95%confidence interval(CI):10.15-16.37;P<0.001].Similarly,the black hole sign(OR 9.4;95%CI:7.4-11.62;P<0.001)and the swirl sign(OR 5.2;95%CI:3.72-6.53;P<0.001)emerged as significant predictors of HE.Initial hematoma volume≥30 mL also showed a sig-nificant association(OR 1.9;95%CI:1.41-2.74;P=0.039).A five-point predictive scoring model demonstrated a strong positive association between increasing scores and the probability of HE.Specifically,the likelihood of HE corresponding to scores of 0,1,2,3,4,and 5 was 7.4%,37.5%,75%,85%,93.3%,and 100%,respectively.CONCLUSION The five variables demonstrated statistically significant associations with HE.This simple and practical 5-point prediction score can enable identification of patients at elevated risk of HE based on baseline NCCT findings.This can facilitate timely recognition of high-risk individuals who may benefit from targeted anti-expansion therapy.展开更多
The demand for the swirl nozzle with enhanced temperature resistance and lightweight properties is in-creasing as the thrust-to-weight ratio of aero-engines rises.The Al_(2)O_(3) ceramic swirl nozzle can maintain high...The demand for the swirl nozzle with enhanced temperature resistance and lightweight properties is in-creasing as the thrust-to-weight ratio of aero-engines rises.The Al_(2)O_(3) ceramic swirl nozzle can maintain high strength in a hostile environment of high temperature and severe corrosion,while also meeting the requirements of aircraft to enhance efficiency and decrease weight.However,Al_(2)O_(3) ceramics are limited in their application for aerospace components due to their poor thermal shock resistance(TSR)stemming from their inherent brittleness.This work reported an innovative design and fabrication strategy based on photopolymerization 3D printing technology to realize the three-dimensional shell structure through element interdiffusion and nanoscale stacking of the reinforced phase.With this strategy,a novel type of the new dual-structure Al_(2)O_(3) ceramic composed of MgAl_(2)O_(4) shell structure and matrix could be con-structed in situ.The nano-sized MgAl_(2)O_(4) caused a crack passivation effect after the thermal shock,which could improve the strength and TSR of 3D-printed Al_(2)O_(3) ceramic.In addition,the effects of MgO content and sintering temperature on sintering behavior,flexural strength,porosity,and TSR of Al_(2)O_(3) ceram-ics manufactured by digital light processing(DLP)processing were systematically studied.The optimum overall performance of Al_(2)O_(3) ceramics was obtained at the sintering temperature of 1550℃and the MgO content of 1.0 wt.%,with a maximum flexural strength of 111.929 MPa and a critical temperature difference of 374.24℃for TSR.Based on the above research,an aero-engine swirl nozzle with high ther-mal shock resistance has been successfully prepared by ceramic 3D printing technology,which enhances high-temperature resistance and promotes lightweight design in aero-engine.展开更多
Ammonia (NH_(3)) is currently considered to be a potential carbon-free alternative fuel,and its large-scale use as such would certainly decrease greenhouse gas emissions and meet increasingly stringent emission requir...Ammonia (NH_(3)) is currently considered to be a potential carbon-free alternative fuel,and its large-scale use as such would certainly decrease greenhouse gas emissions and meet increasingly stringent emission requirements.Although the low flame propagation speed and high NO production of NH_(3) hinder its direct application as a renewable fuel,co-combustion of NH_(3)–H_(2)is an effective way to overcome these challenges.In this study,the combustion characteristics of NH_(3)–H_(2)swirling flames under different equivalence ratios and H_2blending ratios conditions are both numerically and experimentally investigated.Numerically,the One-Dimensional (1D) laminar flame computation presents a comparison base and the Three-Dimensional (3D) numerical simulation yields detailed flame property distributions.Experimentally,the high-speed camera takes instantaneous swirl flame images and the gas analyzer measures the NO emission at the exit plane of the flame chamber.Qualitative and quantitative analysis is performed on the flame structure and NO emission for a series of NH_(3)–H_(2)swirl flames.The variation trends of the NO emission calculated using different techniques agree very well.The quantitative results show that the NO emissions are much higher at lean equivalence ratios than those at rich equivalence ratios,and such difference is closely related to the combustion flame structure.Moreover,it is shown that the utilization of secondary air injection can achieve a significant reduction in NO emissions at the exit of the combustion chamber at equivalence ratios less than or equal to 0.9.展开更多
Three-Dimensional(3D)swirling flow structures,generated by a counter-rotating dualstage swirler in a confined chamber with a confinement ratio of 1.53,were experimentally investigated at Re=2.3×10^(5)using Tomogr...Three-Dimensional(3D)swirling flow structures,generated by a counter-rotating dualstage swirler in a confined chamber with a confinement ratio of 1.53,were experimentally investigated at Re=2.3×10^(5)using Tomographic Particle Image Velocimetry(Tomo-PIV)and planar Particle Image Velocimetry(PIV).Based on the analysis of the 3D time-averaged swirling flow structures and 3D Proper Orthogonal Decomposition(POD)of the Tomo-PIV data,typical coherent flow structures,including the Corner Recirculation Zone(CRZ),Central Recirculation Zone(CTRZ),and Lip Recirculation Zone(LRZ),were extracted.The counter-rotating dual-stage swirler with a Venturi flare generates the independence process of vortex breakdown from the main stage and pilot stage,leading to the formation of an LRZ and a smaller CTRZ near the nozzle outlet.The confinement squeezes the CRZ to the corner and causes a reverse rotation flow to limit the shape of the CTRZ.A large-scale flow structure caused by the main stage features an explosive breakup,flapping,and Precessing Vortex Core(PVC).The explosive breakup mode dominates the swirling flow structures owing to the expansion and construction of the main jet,whereas the flapping mode is related to the wake perturbation.Confinement limits the expansion of PVC and causes it to contract after the impacting area.展开更多
To numerically study the impact of total temperature distortion on a transonic compressor with reduced computational costs,a Body-Force Model(BFM)is developed.Firstly,the interactions between the distorted flow and th...To numerically study the impact of total temperature distortion on a transonic compressor with reduced computational costs,a Body-Force Model(BFM)is developed.Firstly,the interactions between the distorted flow and the compressor are analyzed using full-annulus Unsteady Reynolds-Averaged Navier-Stokes(URANS)results and the orbit method.It is found that the induced swirl distortion and the mass flux nonuniformity are intensified in the compressor upstream flow field.A correction factor is thus added to the BFM to account for the effect of the induced swirl,which is crucial for the accurate representation of distortion transfer in the intake.Then,steady simulations with large-amplitude 180circumferential total temperature distortion are performed using the developed BFM.It is shown that the distorted compressor map simulated with the BFM matches well with URANS results.The circumferential phase shift of total temperature and the generation of the additional total pressure distortion across the rotor are in line with the time-averaged URANS flow field.The compressor upstream effects on the distorted inflow can also be exactly captured.All above-mentioned results demonstrate the BFM developed in this paper can effectively capture the distorted flow features inside the compressor,and significantly reduce the computational costs by five orders of magnitude compared with URANS.展开更多
Efficient metal recovery from industrial wastewater facilitates addressing of the environmental hazards and resource requirements of heavy metals.The conventional electrodeposition recovery method is hampered by the l...Efficient metal recovery from industrial wastewater facilitates addressing of the environmental hazards and resource requirements of heavy metals.The conventional electrodeposition recovery method is hampered by the limitations of interfacial ion transport in charge-transfer reactions,creating challenges for simultaneous rapid and high-quality metal recovery.Therefore,we proposed integrating a transient electric field(TE)and swirling flow(SF)to synchronously enhance bulk mass transfer and promote interfacial ion transport.We investigated the effects of the operation mode,transient frequency,and flow rate on metal recovery,enabling determination of the optimal operating conditions for rapid and efficient sequential recovery of Cu in TE&SF mode.These conditions included low and high electric levels of 0 and 4 V,a 50%duty cycle,1 kHz frequency,and 400 L·h^(-1)flow rate.The kinetic coefficients of TE&SF electrodeposition were 3.5-4.3 and 1.37-1.97 times that of single TE and SF electrodeposition,respectively.Simulating the deposition process under TE and SF conditions confirmed the efficient concurrence of interfacial ion transport and charge transfer under TE and SF synergy,which achieved rapid and highquality metal recovery.Therefore,the combined deposition strategy is considered an effective technique for reducing metal pollution and promoting resource recycling.展开更多
A three-dimensional mathematical model has been established for a novel metallurgy process coupling an annular gas curtain with swirling flow at tundish upper nozzle. The discrete phase model and volume of fluid model...A three-dimensional mathematical model has been established for a novel metallurgy process coupling an annular gas curtain with swirling flow at tundish upper nozzle. The discrete phase model and volume of fluid model were applied to simulate the gas–liquid multiphase flow behavior in tundish and nozzle. The effect of argon flow rate on the migration behavior of bubbles and interface behavior between steel and slag was also investigated. The presented results indicate that the novel coupling process can significantly change the flow pattern in the stream zone of a tundish, prolong the average residence time of liquid steel, and reduce the dead fraction. A complete annular gas curtain is formed around the stopper rod of tundish. Under the action of drag force of liquid steel, a part of small bubbles enter the nozzle through the swirling grooves and gather toward the center of the nozzle by centripetal force. As the argon flow rate increases, the volume fraction of argon gas entering the nozzle increases, which enhances the swirl intensity and increases the concentration of bubbles in the nozzle. To avoid the formation of slag open eye in tundish, the argon flow rate should not exceed 8 L min−1.展开更多
The spray characteristics of different regions downstream of swirl cups play a critical role in cold start and re-ignition of gas turbines.The spray measurements were performed at the fuel pressures of 0.5,0.8,1.0,1.5...The spray characteristics of different regions downstream of swirl cups play a critical role in cold start and re-ignition of gas turbines.The spray measurements were performed at the fuel pressures of 0.5,0.8,1.0,1.5,and 2.0 MPa and the fuel temperatures of-23,-13,-3,7,17 and 27℃,respectively.The droplet size,droplet velocity,droplet number,and instantaneous spatial spray image of sprays from an aviation kerosene Jet-A were measured using a two-component phase Doppler particle analyzer and a digital off-axis holography system.As the fuel pressure and temperature increase,the Sauter Mean Diameter(SMD)and spray non-uniformity of the Spray Shear Layer(SSL)gradually decrease.As the fuel pressure increases,the SMD and spray non-uniformity of the Central Toroidal Recirculation Zone(CTRZ)gradually decrease,and the slopes of these curves both decrease.As the fuel pressure increases,the SMD and spray nonuniformity of the CTRZ rapidly decrease at the fuel temperature of23℃,while slightly decrease at the fuel temperature of 27℃.The droplets in the CTRZ come from 3 different sources:simplex nozzle,venturi,and outside the CTRZ.As the fuel pressure increases,the proportion of droplets recirculated from outside the CTRZ decreases.This study proposed the concept of the“pressure critical point”for the swirl cups.As the fuel temperature decreases,the proportion of droplets recirculated from outside the CTRZ increases below the critical pressure,while decreases above the critical pressure.In addition,through the models of liquid film formation and breakup on the curved cylindrical wall,a semi-theoretical model was established to predict the SMD of SSL for swirl cups.The prediction uncertainty of this model is less than 6%for all 14 conditions in this paper.展开更多
The formation of ice on the leading edge of aircraft engines is a serious issue,as it can have catastrophic consequences.The Swirl Anti-Icing(SAI)system,driven by ejection,circulates hot fluid within a 360°annula...The formation of ice on the leading edge of aircraft engines is a serious issue,as it can have catastrophic consequences.The Swirl Anti-Icing(SAI)system,driven by ejection,circulates hot fluid within a 360°annular chamber to heat the engine inlet lip surface and prevent icing.This study employs a validated Computational Fluid Dynamics(CFD)approach to study the impact of key geometric parameters of this system on flow and heat transfer characteristics within the anti-icing chamber.Additionally,the entropy generation rate and exergy efficiency are analyzed to assess the energy utilization in the system.The research findings indicate that,within the considered flow range,reducing the nozzle specific areaφfrom 0.03061 to 0.01083 can enhance the ejection coefficient by over 60.7%.This enhancement increases the air circulating rate,thereby intensifying convective heat transfer within the SAI chamber.However,the reduction inφalso leads to a significant increase in the required bleed air pressure and a higher entropy generation rate,indicating lower exergy efficiency.The nozzle angleθnotably affects the distribution of hot and cold spots on the lip surface of the SAI chamber.Increasingθfrom 0°to 20°reduces the maximum temperature difference on the anti-icing chamber surface by 60 K.展开更多
The intake swirl in the cylinder was induced by a swirler which was fixed in one of two intake ports. In order to understand the characteristics of the intake swirl, a transparent water analog was designed which simul...The intake swirl in the cylinder was induced by a swirler which was fixed in one of two intake ports. In order to understand the characteristics of the intake swirl, a transparent water analog was designed which simulated 150 type single cylinder engine. At the same time, the particle image velocimetry was used to measure the flow fields induced by various swirlers in the analog. After measurement, a new method was presented to evaluate the intensity of the intake swirl. Then, when the measured sections, the lifts of valve and the swirlers were different, the calculated results of the flow field were compared.展开更多
The experimental study on the macro and micro characteristics of the spray from a pressure swirl nozzle embraces the growth of surface unstable wave,disintegration process,spray angle,breakup length and so on.The e...The experimental study on the macro and micro characteristics of the spray from a pressure swirl nozzle embraces the growth of surface unstable wave,disintegration process,spray angle,breakup length and so on.The effects of injection pressure,nozzle geometry and liquid properties on these characteristics are also discussed.The results are helpful to understand the underlying physics of the pressure swirl nozzle and serve as the basis for the practical design,usage and improvement of the nozzle.展开更多
Aim To obtain an optimizing range of the main configuration parameters of double swirls combustion system (DSCS) Methods To analyze the influence of DS combustion cham-ber configuration parameters on fuel spray and mi...Aim To obtain an optimizing range of the main configuration parameters of double swirls combustion system (DSCS) Methods To analyze the influence of DS combustion cham-ber configuration parameters on fuel spray and mixing by means of the fuel jet developmentperiphery charts obtained by the high speed photography with a modeling test device deve-loped by authors,and to examine it by the tests on a single cylinder diesel engine.Resultsand Conclusion The mixing process can be divided into four phases.The optimizing range of the ration of the inner chamber diameter to the cylinder bore,d2/D,is 0.4-0.7; and the outerchamber diameter,d1 the height of the circular ridge to the piston top face,h1,the radius of outer/inner chamber circle,R1,R2 ,the max depth of outer/inner chamber bowl,H1,H2,etc. are also important展开更多
Based on the porosity method and the improved non uniform QUICK scheme, this paper describes a three dimensional computer simulation to predict the flow characteristics in a tangentially fired boiler. The model is ap...Based on the porosity method and the improved non uniform QUICK scheme, this paper describes a three dimensional computer simulation to predict the flow characteristics in a tangentially fired boiler. The model is applied to a 600?MW boiler modeling under different operating conditions of reverse swirl of secondary air. The numerical results achieve reasonable agreement with experimental data. The calculated results of flow field, the pressure distribution, the relative diameter of tangential circle, angular momentum flux in furnace and the velocity distribution index in horizontal gas pass are analyzed in detail. And then the effects of the reverse swirl of secondary air on flue gas imbalance are discussed. Finally a reasonable operating condition of the reverse swirl of secondary air is presented.展开更多
In this paper,the spray characteristics of a double-swirl low-emission combustor are analyzed by using Particle Imaging Velocimetry(PIV)and Planar Laser Induced Fluorescence(PLIF)technologies in an optical three-secto...In this paper,the spray characteristics of a double-swirl low-emission combustor are analyzed by using Particle Imaging Velocimetry(PIV)and Planar Laser Induced Fluorescence(PLIF)technologies in an optical three-sector combustor test rig.Interactions between sectors and the influence of main stage swirl intensity on spray structure are explained.The results illustrate that the swirl intensity has great effect on the flow field and spray structure.The spray cone angle is bigger when the swirl number is 0.7,0.9 than that when the swirl number is 0.5.The fuel distribution zone is larger and the distribution is more uniform when the swirl number is 0.5.The fuel concentration in the center area of the center plane of side sector(Plane 5)is larger than that of the center plane of middle sector(Plane 1).The spray cone angle in Plane 5 is larger than that in Plane 1.The width of spray cone becomes larger with the increase of Fuel-Air Ratio(FAR),whereas the spray cone angle under different fuel-air ratios are absolutely the same.The results of the mechanism of spray organization in this study can be used to support the design of new low-emission combustor.展开更多
文摘Results of experimental research of the mixing process of coaxial flows in a pipe with swirled peripheral jet are presented in this paper. Distribution of temperature and concentration of gases on the axis and wall of the channel under the influence of such factors as the regime flow, ratio of density of flows and swirl degree of the peripheral jet are studied. Research of temperature, swirl angle, circulation in cross sections along with the channel have shown that their distributions have the jet-like character and are described by known dependences for the layer of mixture.
基金support of the Fundamental Research Funds for the Central Universities(No.E2ET0411X2).
文摘In recent years,research investigations have focused on the substantial freshwater storage in the Beaufort Gyre(BG)region due to climate change.Despite active mesoscale eddies in the area,a notable gap in understanding the three-dimensional structure and induced transport has been observed.This study concentrates on the Canada Basin in the western Arctic Ocean,specifically examining a subsurface anticyclonic eddy(SAE)sampled by a Mooring A in the BG region.Hybrid Coordinate Ocean Model(HYCOM)analysis data reveal its lifecycle from February 15 to March 15,2017,marked by initiation,development,maturity,decay,and termination stages.This work extends the finding of SAE passing through Mooring A by examining its overall effects,spatiotemporal variations,and swirl transport.SAE generation through baroclinic instability,which contributes to the westward tilt of the vertical axis,is also confirmed in this study.Swirl transport induced by SAE is predominantly eastward and downward due to its trajectory and background flow.SAE temporarily weakens stratification and extends the subsurface depth but demonstrates transient effects.Moreover,SAE transports upper-layer freshwater,Pacific Winter Water,and Atlantic Water downward,emphasizing its potential influence on freshwater redistribution in the Canadian Basin.This research provides valuable insights into mesoscale eddy dynamics,revealing their role in modulating the upper water mass in the BG region.
基金supported by the Application Technology of Automotive Steels(No.2021040300048)the National Natural Science Foundation of China(No.52304347)+2 种基金Hebei Provincial Natural Science Foundation(No.E2019501008),China Baowu Low Carbon Metallurgy Innovation Foundation(BWLCF202320)Natural Science Foundation of Liaoning Province(Nos.2023-MSBA-135 and 2023-BSBA-107)Fundamental Research Funds for the Central Universities(Nos.N2409008 and N2409006).
文摘The electromagnetic swirling flow in nozzle(EMSFN)technique is designed to mitigate the adverse effects of unstable and uneven flow within the submerged entry nozzle in continuous casting.Utilizing electromagnetic forces,EMSFN stabilizes the flow within the nozzle,leading to a more controlled flow in the mold.Numerical simulations were used to quantitatively analyze the magnetic and flow fields in a slab continuous casting system under EMSFN.Results indicate that EMSFN significantly stabilizes the outflow from the nozzle,with stability increasing with higher current intensity.At 10,000 Ampere-turns(At)of the coil,meniscus fluctuations were unstable.They stabilized at 13,000 At,with minimal changes observed beyond this point.The optimal current intensity for stable mold flow,at a casting speed of 1.56 m/min,is 13,000 At.These findings confirm the effectiveness of EMSFN in stabilizing the internal flow field of the slab mold and determining optimal operational current intensity.
基金National Natural Science Foundation of China(Nos.U21A20117,52104347 and 52272078)the Fundamental Research Funds for the Central Universities(No.N2409006)Natural Science Foundation of Liaoning Province(2023-MSBA-135)for the financial support.
文摘Controlling molten steel flow in the mold and stabilizing the meniscus are critical challenges during the continuous casting,directly impacting the surface quality and internal quality of the final steel slab product.The effects of electromagnetic swirling flow in nozzle(EMSFN)technology on molten steel flow in the mold during slab continuous casting under various casting speeds were investigated.A real-time adjustable EMSFN was developed,and a three-dimensional unsteady Reynolds-averaged Navier–Stokes turbulence mathematical model was established to simulate the flow field within the mold.The results demonstrate that the EMSFN effectively stabilizes the outflow from nozzle,reduces the impact depth and surface velocity of the molten steel,mitigates meniscus fluctuations,and promotes stable flow within the mold.However,a certain matching relationship exists between the casting speed and the current intensity.For the experimental medium-thick slab specifications,the optimal current intensities were found to be 100,130,and 200 A at casting speeds of 1.0,1.5,and 2.0 m/min,respectively.EMSFN can optimize the mold flow field under different casting speeds,providing theoretical support for improving the quality of continuously cast slab products.
基金supported by the National Natural Science Foundation of China(Nos.52306035 and 52325602)the Science Center for Gas Turbine Project,China(Nos.P2022-A-II-002-001 and P2022-C-II-003-001)+1 种基金the National Science and Technology Major Project,China(Nos.Y2022-II-0002-0005 and Y2022-II-0003-0006)the Key Laboratory of Pre-Research Management Centre,China(No.6142702200101)。
文摘An experimental investigation is conducted to evaluate the performance and the stalling process of a fan subjected to inlet swirls,as well as the effectiveness of an Impedance Boundary-Controlled(IBC)Casing Treatment(CT)on the stall margin recovery.An operating cycle is proposed based on the hysteresis effect of harmonic flap oscillation of airfoils and parallel compressor theory to explain the pressure characteristic of the fan under twin swirl inlets.Twin swirls are observed to reduce the stall margin of the fan,and the circumferential location where the spike is detected turns to the intersection area of the twin swirl.The IBC CT is proven to extend the stall margin of the fan for 12.7%–22.3%when subjected to inlet swirls with an efficiency loss of around 1%.The IBC CT helps to reduce the size of the operating cycle of the fan by redistributing the blade loading and adding the system damping to dissipate the perturbation energy.
文摘BACKGROUND Intracerebral hemorrhage(ICH)comprises 9%-27%of stroke patients.Hematoma expansion(HE)occurs in approximately 20%of patients following ICH,typically within the first 24 hours.HE increases mortality and long-term disability in these patients and is being investigated as a therapeutic target to improve the outcome in these patients by limiting HE.Non-contrast computed tomography(NCCT)has potential in predicting HE,which can identify the individuals at risk.AIM To evaluate NCCT markers for predicting HE in patients with ICH and to develop a simple,practical grading system for risk stratification.METHODS This prospective observational study evaluated 192 patients with spontaneous ICH who underwent a baseline NCCT within four hours of admission,followed by a follow-up scan after six hours or earlier if there was clinical deterioration.Hematoma volumes and imaging characteristics that predicted HE were evaluated.A simple five-point grading system score was created to predict HE.In RESULTS Of the 192 patients studied,HE was seen in 106(55.2%).The mean baseline hematoma volume was significantly greater among patients in the HE group(44.1 mL)compared to those in the non-HE group(12.2 mL),with a P-value<0.05.Additionally,imaging biomarkers such as the island sign,swirl sign,and black hole sign were observed with significantly higher frequency in the HE group relative to the non-HE cohort(all P-values<0.05).The island sign was strongly associated with HE[odds ratio(OR)13.7;95%confidence interval(CI):10.15-16.37;P<0.001].Similarly,the black hole sign(OR 9.4;95%CI:7.4-11.62;P<0.001)and the swirl sign(OR 5.2;95%CI:3.72-6.53;P<0.001)emerged as significant predictors of HE.Initial hematoma volume≥30 mL also showed a sig-nificant association(OR 1.9;95%CI:1.41-2.74;P=0.039).A five-point predictive scoring model demonstrated a strong positive association between increasing scores and the probability of HE.Specifically,the likelihood of HE corresponding to scores of 0,1,2,3,4,and 5 was 7.4%,37.5%,75%,85%,93.3%,and 100%,respectively.CONCLUSION The five variables demonstrated statistically significant associations with HE.This simple and practical 5-point prediction score can enable identification of patients at elevated risk of HE based on baseline NCCT findings.This can facilitate timely recognition of high-risk individuals who may benefit from targeted anti-expansion therapy.
基金National Key Research and Development Program of China(No.2017YFA0700704)National Defense Basic Scientific Research Program of China(Grant No.JCKY2022130C005)+3 种基金National Natural Science Foundation of China(No.U22A20129)National Science and Technology Major Project(No.2017-VI-0002–0072)National Key Research and Development Program of China(No.2018YFB1106600)Students’Innovation and Entrepreneurship Foundation of USTC(Nos.CY2022G10 and CY2022C24)。
文摘The demand for the swirl nozzle with enhanced temperature resistance and lightweight properties is in-creasing as the thrust-to-weight ratio of aero-engines rises.The Al_(2)O_(3) ceramic swirl nozzle can maintain high strength in a hostile environment of high temperature and severe corrosion,while also meeting the requirements of aircraft to enhance efficiency and decrease weight.However,Al_(2)O_(3) ceramics are limited in their application for aerospace components due to their poor thermal shock resistance(TSR)stemming from their inherent brittleness.This work reported an innovative design and fabrication strategy based on photopolymerization 3D printing technology to realize the three-dimensional shell structure through element interdiffusion and nanoscale stacking of the reinforced phase.With this strategy,a novel type of the new dual-structure Al_(2)O_(3) ceramic composed of MgAl_(2)O_(4) shell structure and matrix could be con-structed in situ.The nano-sized MgAl_(2)O_(4) caused a crack passivation effect after the thermal shock,which could improve the strength and TSR of 3D-printed Al_(2)O_(3) ceramic.In addition,the effects of MgO content and sintering temperature on sintering behavior,flexural strength,porosity,and TSR of Al_(2)O_(3) ceram-ics manufactured by digital light processing(DLP)processing were systematically studied.The optimum overall performance of Al_(2)O_(3) ceramics was obtained at the sintering temperature of 1550℃and the MgO content of 1.0 wt.%,with a maximum flexural strength of 111.929 MPa and a critical temperature difference of 374.24℃for TSR.Based on the above research,an aero-engine swirl nozzle with high ther-mal shock resistance has been successfully prepared by ceramic 3D printing technology,which enhances high-temperature resistance and promotes lightweight design in aero-engine.
基金the National Natural Science Foundation of China (Nos.51876182 and 52006184)the Fundamental Research Funds for the Central Universities of China (No.20720180058)the Fundamental Research Funds,China (No.2020-JJ-118)。
文摘Ammonia (NH_(3)) is currently considered to be a potential carbon-free alternative fuel,and its large-scale use as such would certainly decrease greenhouse gas emissions and meet increasingly stringent emission requirements.Although the low flame propagation speed and high NO production of NH_(3) hinder its direct application as a renewable fuel,co-combustion of NH_(3)–H_(2)is an effective way to overcome these challenges.In this study,the combustion characteristics of NH_(3)–H_(2)swirling flames under different equivalence ratios and H_2blending ratios conditions are both numerically and experimentally investigated.Numerically,the One-Dimensional (1D) laminar flame computation presents a comparison base and the Three-Dimensional (3D) numerical simulation yields detailed flame property distributions.Experimentally,the high-speed camera takes instantaneous swirl flame images and the gas analyzer measures the NO emission at the exit plane of the flame chamber.Qualitative and quantitative analysis is performed on the flame structure and NO emission for a series of NH_(3)–H_(2)swirl flames.The variation trends of the NO emission calculated using different techniques agree very well.The quantitative results show that the NO emissions are much higher at lean equivalence ratios than those at rich equivalence ratios,and such difference is closely related to the combustion flame structure.Moreover,it is shown that the utilization of secondary air injection can achieve a significant reduction in NO emissions at the exit of the combustion chamber at equivalence ratios less than or equal to 0.9.
基金supported by the National Natural Science Foundation of China(Nos.12232002,12072017,12002199,and 11721202)。
文摘Three-Dimensional(3D)swirling flow structures,generated by a counter-rotating dualstage swirler in a confined chamber with a confinement ratio of 1.53,were experimentally investigated at Re=2.3×10^(5)using Tomographic Particle Image Velocimetry(Tomo-PIV)and planar Particle Image Velocimetry(PIV).Based on the analysis of the 3D time-averaged swirling flow structures and 3D Proper Orthogonal Decomposition(POD)of the Tomo-PIV data,typical coherent flow structures,including the Corner Recirculation Zone(CRZ),Central Recirculation Zone(CTRZ),and Lip Recirculation Zone(LRZ),were extracted.The counter-rotating dual-stage swirler with a Venturi flare generates the independence process of vortex breakdown from the main stage and pilot stage,leading to the formation of an LRZ and a smaller CTRZ near the nozzle outlet.The confinement squeezes the CRZ to the corner and causes a reverse rotation flow to limit the shape of the CTRZ.A large-scale flow structure caused by the main stage features an explosive breakup,flapping,and Precessing Vortex Core(PVC).The explosive breakup mode dominates the swirling flow structures owing to the expansion and construction of the main jet,whereas the flapping mode is related to the wake perturbation.Confinement limits the expansion of PVC and causes it to contract after the impacting area.
基金the National Science and Technology Major Project,China(Nos.J2019-Ⅱ-0020-0041 and J2019-Ⅱ-0017-0038)the Science Center for Gas Turbine Project,China(No.P2022-A-Ⅱ-002-001)the National Natural Science Foundation of China(No.52206061).
文摘To numerically study the impact of total temperature distortion on a transonic compressor with reduced computational costs,a Body-Force Model(BFM)is developed.Firstly,the interactions between the distorted flow and the compressor are analyzed using full-annulus Unsteady Reynolds-Averaged Navier-Stokes(URANS)results and the orbit method.It is found that the induced swirl distortion and the mass flux nonuniformity are intensified in the compressor upstream flow field.A correction factor is thus added to the BFM to account for the effect of the induced swirl,which is crucial for the accurate representation of distortion transfer in the intake.Then,steady simulations with large-amplitude 180circumferential total temperature distortion are performed using the developed BFM.It is shown that the distorted compressor map simulated with the BFM matches well with URANS results.The circumferential phase shift of total temperature and the generation of the additional total pressure distortion across the rotor are in line with the time-averaged URANS flow field.The compressor upstream effects on the distorted inflow can also be exactly captured.All above-mentioned results demonstrate the BFM developed in this paper can effectively capture the distorted flow features inside the compressor,and significantly reduce the computational costs by five orders of magnitude compared with URANS.
基金supported financially by the National Natural Science Foundation of China(52221004).
文摘Efficient metal recovery from industrial wastewater facilitates addressing of the environmental hazards and resource requirements of heavy metals.The conventional electrodeposition recovery method is hampered by the limitations of interfacial ion transport in charge-transfer reactions,creating challenges for simultaneous rapid and high-quality metal recovery.Therefore,we proposed integrating a transient electric field(TE)and swirling flow(SF)to synchronously enhance bulk mass transfer and promote interfacial ion transport.We investigated the effects of the operation mode,transient frequency,and flow rate on metal recovery,enabling determination of the optimal operating conditions for rapid and efficient sequential recovery of Cu in TE&SF mode.These conditions included low and high electric levels of 0 and 4 V,a 50%duty cycle,1 kHz frequency,and 400 L·h^(-1)flow rate.The kinetic coefficients of TE&SF electrodeposition were 3.5-4.3 and 1.37-1.97 times that of single TE and SF electrodeposition,respectively.Simulating the deposition process under TE and SF conditions confirmed the efficient concurrence of interfacial ion transport and charge transfer under TE and SF synergy,which achieved rapid and highquality metal recovery.Therefore,the combined deposition strategy is considered an effective technique for reducing metal pollution and promoting resource recycling.
基金funded by the National Natural Science Foundation of China(Nos.51874215 and 52204351)the China Postdoctoral Science Foundation(2022M722487).
文摘A three-dimensional mathematical model has been established for a novel metallurgy process coupling an annular gas curtain with swirling flow at tundish upper nozzle. The discrete phase model and volume of fluid model were applied to simulate the gas–liquid multiphase flow behavior in tundish and nozzle. The effect of argon flow rate on the migration behavior of bubbles and interface behavior between steel and slag was also investigated. The presented results indicate that the novel coupling process can significantly change the flow pattern in the stream zone of a tundish, prolong the average residence time of liquid steel, and reduce the dead fraction. A complete annular gas curtain is formed around the stopper rod of tundish. Under the action of drag force of liquid steel, a part of small bubbles enter the nozzle through the swirling grooves and gather toward the center of the nozzle by centripetal force. As the argon flow rate increases, the volume fraction of argon gas entering the nozzle increases, which enhances the swirl intensity and increases the concentration of bubbles in the nozzle. To avoid the formation of slag open eye in tundish, the argon flow rate should not exceed 8 L min−1.
基金supported by the Provincial or Ministerial Level Project.
文摘The spray characteristics of different regions downstream of swirl cups play a critical role in cold start and re-ignition of gas turbines.The spray measurements were performed at the fuel pressures of 0.5,0.8,1.0,1.5,and 2.0 MPa and the fuel temperatures of-23,-13,-3,7,17 and 27℃,respectively.The droplet size,droplet velocity,droplet number,and instantaneous spatial spray image of sprays from an aviation kerosene Jet-A were measured using a two-component phase Doppler particle analyzer and a digital off-axis holography system.As the fuel pressure and temperature increase,the Sauter Mean Diameter(SMD)and spray non-uniformity of the Spray Shear Layer(SSL)gradually decrease.As the fuel pressure increases,the SMD and spray non-uniformity of the Central Toroidal Recirculation Zone(CTRZ)gradually decrease,and the slopes of these curves both decrease.As the fuel pressure increases,the SMD and spray nonuniformity of the CTRZ rapidly decrease at the fuel temperature of23℃,while slightly decrease at the fuel temperature of 27℃.The droplets in the CTRZ come from 3 different sources:simplex nozzle,venturi,and outside the CTRZ.As the fuel pressure increases,the proportion of droplets recirculated from outside the CTRZ decreases.This study proposed the concept of the“pressure critical point”for the swirl cups.As the fuel temperature decreases,the proportion of droplets recirculated from outside the CTRZ increases below the critical pressure,while decreases above the critical pressure.In addition,through the models of liquid film formation and breakup on the curved cylindrical wall,a semi-theoretical model was established to predict the SMD of SSL for swirl cups.The prediction uncertainty of this model is less than 6%for all 14 conditions in this paper.
基金Shenyang Key Laboratory of Aircraft Icing and Ice Protection,Grant Number XFX20220303Education Department of Hunan Province,China,Grant Number 23A0504National Natural Science Foundation of China,Grant Number 52275108.
文摘The formation of ice on the leading edge of aircraft engines is a serious issue,as it can have catastrophic consequences.The Swirl Anti-Icing(SAI)system,driven by ejection,circulates hot fluid within a 360°annular chamber to heat the engine inlet lip surface and prevent icing.This study employs a validated Computational Fluid Dynamics(CFD)approach to study the impact of key geometric parameters of this system on flow and heat transfer characteristics within the anti-icing chamber.Additionally,the entropy generation rate and exergy efficiency are analyzed to assess the energy utilization in the system.The research findings indicate that,within the considered flow range,reducing the nozzle specific areaφfrom 0.03061 to 0.01083 can enhance the ejection coefficient by over 60.7%.This enhancement increases the air circulating rate,thereby intensifying convective heat transfer within the SAI chamber.However,the reduction inφalso leads to a significant increase in the required bleed air pressure and a higher entropy generation rate,indicating lower exergy efficiency.The nozzle angleθnotably affects the distribution of hot and cold spots on the lip surface of the SAI chamber.Increasingθfrom 0°to 20°reduces the maximum temperature difference on the anti-icing chamber surface by 60 K.
文摘The intake swirl in the cylinder was induced by a swirler which was fixed in one of two intake ports. In order to understand the characteristics of the intake swirl, a transparent water analog was designed which simulated 150 type single cylinder engine. At the same time, the particle image velocimetry was used to measure the flow fields induced by various swirlers in the analog. After measurement, a new method was presented to evaluate the intensity of the intake swirl. Then, when the measured sections, the lifts of valve and the swirlers were different, the calculated results of the flow field were compared.
文摘The experimental study on the macro and micro characteristics of the spray from a pressure swirl nozzle embraces the growth of surface unstable wave,disintegration process,spray angle,breakup length and so on.The effects of injection pressure,nozzle geometry and liquid properties on these characteristics are also discussed.The results are helpful to understand the underlying physics of the pressure swirl nozzle and serve as the basis for the practical design,usage and improvement of the nozzle.
文摘Aim To obtain an optimizing range of the main configuration parameters of double swirls combustion system (DSCS) Methods To analyze the influence of DS combustion cham-ber configuration parameters on fuel spray and mixing by means of the fuel jet developmentperiphery charts obtained by the high speed photography with a modeling test device deve-loped by authors,and to examine it by the tests on a single cylinder diesel engine.Resultsand Conclusion The mixing process can be divided into four phases.The optimizing range of the ration of the inner chamber diameter to the cylinder bore,d2/D,is 0.4-0.7; and the outerchamber diameter,d1 the height of the circular ridge to the piston top face,h1,the radius of outer/inner chamber circle,R1,R2 ,the max depth of outer/inner chamber bowl,H1,H2,etc. are also important
文摘Based on the porosity method and the improved non uniform QUICK scheme, this paper describes a three dimensional computer simulation to predict the flow characteristics in a tangentially fired boiler. The model is applied to a 600?MW boiler modeling under different operating conditions of reverse swirl of secondary air. The numerical results achieve reasonable agreement with experimental data. The calculated results of flow field, the pressure distribution, the relative diameter of tangential circle, angular momentum flux in furnace and the velocity distribution index in horizontal gas pass are analyzed in detail. And then the effects of the reverse swirl of secondary air on flue gas imbalance are discussed. Finally a reasonable operating condition of the reverse swirl of secondary air is presented.
基金supported by the National Natural Science Foundation of China(Nos.51306182 and 51406202).
文摘In this paper,the spray characteristics of a double-swirl low-emission combustor are analyzed by using Particle Imaging Velocimetry(PIV)and Planar Laser Induced Fluorescence(PLIF)technologies in an optical three-sector combustor test rig.Interactions between sectors and the influence of main stage swirl intensity on spray structure are explained.The results illustrate that the swirl intensity has great effect on the flow field and spray structure.The spray cone angle is bigger when the swirl number is 0.7,0.9 than that when the swirl number is 0.5.The fuel distribution zone is larger and the distribution is more uniform when the swirl number is 0.5.The fuel concentration in the center area of the center plane of side sector(Plane 5)is larger than that of the center plane of middle sector(Plane 1).The spray cone angle in Plane 5 is larger than that in Plane 1.The width of spray cone becomes larger with the increase of Fuel-Air Ratio(FAR),whereas the spray cone angle under different fuel-air ratios are absolutely the same.The results of the mechanism of spray organization in this study can be used to support the design of new low-emission combustor.
