The slag melting characteristic of slag forming and slag splashing for 300 t BOF less slag process is researched by combining the methods of the slag chemical composition, the melting point determination and the petro...The slag melting characteristic of slag forming and slag splashing for 300 t BOF less slag process is researched by combining the methods of the slag chemical composition, the melting point determination and the petrographic analysis. The results show that the melting point of final slag for less slag smelting is 20 ~C lower than that for conventional smelting. According to results of the petrographic analysis, the C3S （3CaO ~ SiO2） and C2S （2CaO · SiO2） content for less slag smelting are lower than those for conventional smelting, while the RO （FeO, MgO, MnO, etc） phase and C4AF （4CaO · Al2O3· Fe2O3） phase are higher than those for conventional smelting. According to results of the chemical analysis, the （CaO） content and slag basicity for less slag smelting are higher than those for conventional smelting, while （FeO） and （MgO） content in slag for less slag smelting are almost equal to those for conventional smelting. The reason why slag melting point for less slag smelting is lower than that for con- ventional smelting is that the quantity of added fluorite for less slag smelting is more than that for conventional smel- ting. According tO the analysis results the slag melting point is determined by the C3S, C2S, RO phase and C4AF content. According to the results of slag melting characteristic before and after slag splashing for less slag smelting, the present adjusting slag process has little effect. It is important to adjust the composition of BOF final slag. The （FeO） content in slag is to be reduced at the slag splashing and adjusting slag process for less slag smelting.展开更多
Converter off-gas, an important energy resource for steel industries, is one of the weak points in the recov ery and utilization of secondary energy resources. To improve the level of recycling converter off-gas in st...Converter off-gas, an important energy resource for steel industries, is one of the weak points in the recov ery and utilization of secondary energy resources. To improve the level of recycling converter off-gas in steel plants, a novel approach to the recycle of CO2 separated from converter off-gas or other off-gas for the green slag splashing technique was developed, and the CO2 equilibrium conversion ratio of the green CO2 slag splashing under different technological conditions was calculated by the program of enthalpy （H）, entropy （S）, and heat capacity （C）, i.e. HSC software. Furthermore, the experiments of CO2 injected into molten converter slag were carried out, and the influencing factors of the green slag splashing technique using CO2 were analyzed. The experimental results showed that the carbon content for smooth slag splashing using COs was about 4.0%.展开更多
The sudden transition from a high-velocity, supercritical open channel flow into a slow-moving sub-critical flow is a hydraulic jump. Such a flow is characterised by a sudden rise of the free-surface, with some strong...The sudden transition from a high-velocity, supercritical open channel flow into a slow-moving sub-critical flow is a hydraulic jump. Such a flow is characterised by a sudden rise of the free-surface, with some strong energy dissipation and air entrainment, waves and spray. New two-phase flow measurements were performed in the developing flow region using a large-size facility operating at large Reynolds numbers. The experimental results demonstrated the complexity of the flow with a developing mixing layer in which entrained bubbles are advected in a high shear stress flow. The relationship between bubble count rates and void fractions was non-unique in the shear zone, supporting earlier observations of some form of double diffusion process between momentum and air bubbles. In the upper region, the flow consisted primarily of water drops and packets sur-rounded by air. Visually significant pray and splashing were significant above the jump roller. The present study is the first com-prehensive study detailing the two-phase flow properties of both the bubbly and spray regions of hydraulic jumps, a first step towards understanding the interactions between bubble entrainment and droplet ejection processes.展开更多
Some differences in slag splashing between BOF steel works in US and China were investigated. The slag composition,melting point, and mineralogical phases of final slags from both countries were studied. The control o...Some differences in slag splashing between BOF steel works in US and China were investigated. The slag composition,melting point, and mineralogical phases of final slags from both countries were studied. The control of slag superheat is important to an effective slag coating.展开更多
In recent years,forest fires and maritime accidents have occurred frequently,which have had a bad impact on human production and life.Thus,the development of seaplanes is an increasingly urgent demand.It is important ...In recent years,forest fires and maritime accidents have occurred frequently,which have had a bad impact on human production and life.Thus,the development of seaplanes is an increasingly urgent demand.It is important to study the taxiing process of seaplanes for the development of seaplanes,which is a strong nonlinear fluid-structure interaction problem.In this paper,the smoothed particle hydrodynamics(SPH)method based on the Lagrangian framework is utilized to simulate the taxiing process of seaplanes,and the SPH results are compared with those of the finite volume method(FVM)based on the Eulerian method.The results show that the SPH method can not only give the same accuracy as the FVM but also have a strong ability to capture the splashing waves in the taxiing process,which is quite meaningful for the subsequent study of the effect of a splash on other parts of the seaplane.展开更多
The measured results show that the overexpanded supersonic jet velocity produced by low stagnation pressure (0.53 MPa) attenuates quickly, deviates greatly with smaller impact area and large energy loss. According to ...The measured results show that the overexpanded supersonic jet velocity produced by low stagnation pressure (0.53 MPa) attenuates quickly, deviates greatly with smaller impact area and large energy loss. According to the measured results and the analysis of lashing energy of jet on the bath, the technological parameters of nitrogen flow in slag splashing were proposed.展开更多
To understand the effects of spray parameters on the splashing,cast iron particles were plasma-sprayed onto polished surfaces of aluminum substrate to form single splats.Various plasma arc powers and spray distances w...To understand the effects of spray parameters on the splashing,cast iron particles were plasma-sprayed onto polished surfaces of aluminum substrate to form single splats.Various plasma arc powers and spray distances were applied to adjust the morphology of the splats which was studied using a field emission scanning electron microscope（FESEM）.The experimentalresults showed that the splashing of impinging droplets was significantly restrained for the splats deposited with high arc power（30 k W）and short spray distance（80 mm）.This finding would be beneficialto improving the adhesive strength of the coating.展开更多
The influence of three different blowing conditions on the slag splashing process in a basic oxygen furnace for steelmaking is analyzed here using two-dimensional transient Computational Fluid Dynamics simulations. Fo...The influence of three different blowing conditions on the slag splashing process in a basic oxygen furnace for steelmaking is analyzed here using two-dimensional transient Computational Fluid Dynamics simulations. Four blowing conditions are considered in the computer runs: top blowing, combined blowing using just a bottom centered nozzle, combined blowing using two bottom lateral nozzles, and full combined blowing using the three top and the three bottom nozzles. Computer simulations show that full combined blowing provides greater slag splashing than conventional top blowing.展开更多
Physical properties of molten slag such as viscosity, density and surface tension have a significant influence on the slag splashing process in an oxygen steelmaking converter. Particularly, viscosity determines the s...Physical properties of molten slag such as viscosity, density and surface tension have a significant influence on the slag splashing process in an oxygen steelmaking converter. Particularly, viscosity determines the shear forces that rule droplets formation. Besides, stirring of the molten slag bath strongly depends on this property. In this work, the influence of viscosity on the efficiency of slag splashing is explored by means of transient Computational Fluid Dynamics simulations. Several values of viscosity are employed in the computer experiments. In order to quantify the splashing efficiency as function of slag viscosity, an average slag fraction on the converter walls is defined and calculated. CFD results are compared with those of an empirical expression, and at least qualitative agreement is found.展开更多
Basic oxygen steelmaking(BOS)is the most frequently used method to produce molten steel,which is being developed to meet the requirements of being safe,efficient,clean,and intelligent.During the BOS process,splashing ...Basic oxygen steelmaking(BOS)is the most frequently used method to produce molten steel,which is being developed to meet the requirements of being safe,efficient,clean,and intelligent.During the BOS process,splashing events cause undesirable consequences,such as casualties,low efficiency,environmental pollution,and uncontrollable operation.The causes of three types of splashing(eruptive,foaming,and metallic splashing)were unraveled and it is concluded that inappropriate foaming is the root cause of splashing.A variety of monitoring techniques for splashing have been developed to measure real-time slag foaming in a basic oxygen furnace(BOF).The audiometry technique with flexible operation and high accuracy was comprehensively introduced with a practical application.Based on the formation mechanisms,the countermeasures for the three types of splashing were proposed to regulate slag foaming in a BOF by integrating diverse measures in terms of raw materials,slag forming,blowing pattern,and the use of splashing regulating agents.Future work should emphasise an automatic action for these prevention measures in response to the splashing risk from the monitoring technology,promoting the progress of intelligent steelmaking.展开更多
SeveraL parameters affecting slag splashing in LD converter have been discussed. Using parffin and starch model, a simulated test about 30 t converter has been made in laboratory and the modified Frode numberwas chose...SeveraL parameters affecting slag splashing in LD converter have been discussed. Using parffin and starch model, a simulated test about 30 t converter has been made in laboratory and the modified Frode numberwas chosen as the main similar basis of the system. It was results that the optimized slag splashing parameters wasobtained through data treatment The nitrogen gas flow rate is about 8 500 m3/h, the splashing time is of 3 min,and the lance height is of 0.8 m. It is necessary to add MgO or carbon into the slag to adjusting slag composition.Also, it is difficult for the splashed slag condensing on the line when the slag temperature is much higher展开更多
Some variables that influence the slag splashing phenomenon in an oxygen steelmaking converter are numerically analyzed in this work. The effect of lance height, jet velocity, jet exit angle and slag viscosity on the ...Some variables that influence the slag splashing phenomenon in an oxygen steelmaking converter are numerically analyzed in this work. The effect of lance height, jet velocity, jet exit angle and slag viscosity on the washing and ejection mechanisms of slag splashing is studied employing transient two-dimensional computational fluid dynamics simulations. A parameter here called average slag volume fraction is proposed for the quantitative evaluation of the slag splashing efficiency. Besides, a qualitative comparison is made between the computational fluid dynamics results and physical model results from literature.展开更多
“It's coming!”Liu Fuhai shouted,lying prone on a rock,one of his eyes pressed against his camera.Beads of sweat could be seen on his forehead.Roaring water in the Yellow River plunged from the cliff,making gigan...“It's coming!”Liu Fuhai shouted,lying prone on a rock,one of his eyes pressed against his camera.Beads of sweat could be seen on his forehead.Roaring water in the Yellow River plunged from the cliff,making gigantic splashes(落水声)which eventually turned into thick mists.Liu,holding his breath,clicked the shutter quickly to capture the grandeur of the Hukou Waterfall,the largest waterfall on the Yellow River.展开更多
Accurate simulation of ice accretion of supercooled large droplet(SLD)is pivotal for the international airworthiness certification of large aircraft.Its complex dynamics behavior and broad particle size distributions ...Accurate simulation of ice accretion of supercooled large droplet(SLD)is pivotal for the international airworthiness certification of large aircraft.Its complex dynamics behavior and broad particle size distributions pose significant challenges to reliable CFD predictions.A numerical model of multi-particle SLD coupling breaking,bouncing and splashing behaviors is established to explore the relationship between dynamics behavior and particle size.The results show that the peak value of droplet collection efficiencyβdecreases due to splashing.The bounce phenomenon will make the impact limit S_(m)of the water drops decrease.With the increase of the SLD particle size,the water drop bounce point gradually moves toward the trailing edge of the wing.The critical breaking diameter of SLD at an airflow velocity of 50 m/s is approximately 100μm.When the SLD particle size increases,the height of the water droplet shelter zone on the upper edge of the wing gradually decreases,and the velocity in the Y direction decreases first and then increases in the opposite direction,increasing the probability of SLD hitting the wing again.Large particle droplets have a higher effect on the impact limit S_(m)than smaller droplets.Therefore,in the numerical simulation of the SLD operating conditions,it is very important to ensure the proportion of large particle size water droplets.展开更多
The Water-Sprinkling Festival of the Dai ethnic group is the most widely celebrated rite among the ethnic minorities living in Yunnan province.This weeklong celebration,marking the Dai Lunar New Year,usually falls aro...The Water-Sprinkling Festival of the Dai ethnic group is the most widely celebrated rite among the ethnic minorities living in Yunnan province.This weeklong celebration,marking the Dai Lunar New Year,usually falls around mid-April.People of all ages,dressed in their festival best,take part in the solemn ritual of washing statues of Buddha.They later take great展开更多
The variation characteristics of bubble morphology and the thermal-physical properties of bubble boundary in the top-blown smelting furnace were explored by means of the computational fluid dynamics method.The essenti...The variation characteristics of bubble morphology and the thermal-physical properties of bubble boundary in the top-blown smelting furnace were explored by means of the computational fluid dynamics method.The essential aspects of the fluid phase(e.g.,splashing volume,dead zone of copper slag,and gas penetration depth)were explored together with the effect of sinusoidal pulsating gas intake on the momentum-transfer performance between phases.The results illustrated that two relatively larger vortices and two smaller vortices appear in the bubble waist and below the lance,respectively.The expansion of larger ones as well as the shrinking of smaller ones combine to cause the contraction of the bubble waist.Compared to the results of the case with a fixed gas injection velocity(V_(g)=58 m/s),the splashing volume and dead zone volume of the slag under the V_(g)=58+10sin(2πt)condition are reduced by 24.9%and 23.5%,respectively,where t represents the instant time.Gas penetration depth and slag motion velocity of the latter are 1.03 and 1.31 times high-er than those of the former,respectively.展开更多
In this study,we investigate the effect of rail vibrations on the lubrication and efficiency of a splash-lubricated gearbox;specifically,the gearbox of a rail-transit vehicle.A high-fidelity 3D numerical model of the ...In this study,we investigate the effect of rail vibrations on the lubrication and efficiency of a splash-lubricated gearbox;specifically,the gearbox of a rail-transit vehicle.A high-fidelity 3D numerical model of the gearbox in a moving reference system is described,as well as computational fluid dynamics(CFD)simulations of the gearbox with different vibration directions.The effects of rotational speed,oil-immersion depth,and different oil-injection volume rates on lubrication and efficiency are discussed.We propose a method of evaluating the internal lubrication condition of a splash-lubricated gearbox and quantitatively compare the effects of different operating parameters on lubrication and efficiency.Finally,our experiment to verify the feasibility of the simulation method is described.The results show that with vibration,the churning loss and oil supply for the bearings are significantly higher than those under static conditions.In addition,among different vibrational directions,lateral vibration has the greatest influence on the lubrication condition and efficiency of the gearbox.For the studied railway-vehicle gearbox,the best lubrication condition is achieved at a rotational speed of 1600 r/min and an oil-immersion depth of two times the tooth height(2.Oh).Rotational speed is the operating parameter that has the most significant effect on the lubrication and efficiencyofthegearbox.展开更多
To explore the water entry flow and impact load characteristics of northern gannets,we conducted water entry experiments using a northern gannet’s head model based on three-dimensional(3D)printing and several cone mo...To explore the water entry flow and impact load characteristics of northern gannets,we conducted water entry experiments using a northern gannet’s head model based on three-dimensional(3D)printing and several cone models under different Froude numbers.A high-speed camera was used to capture flow images,and an inertial measurement unit(IMU)was used to record the water entry impact loads.The results indicate that the geometric topology of the model considerably influenced the water entry flow and impact load.Specifically,the northern gannet’s head model created a smaller water entry splash crown,cavity geometry,and impact load compared with the cone models of similar sizes.展开更多
The intermediate gearbox of a helicopter operates under splash lubrication.If the bearing produces metal particles due to insufficient lubrication or wear,whether it can be adsorbed by the metal particles signal at th...The intermediate gearbox of a helicopter operates under splash lubrication.If the bearing produces metal particles due to insufficient lubrication or wear,whether it can be adsorbed by the metal particles signal at the bottom of the gearbox and alarm directly affects the flight safety of the helicopter.Based on the CFD method,the factors affecting the accessibility of metal particles are analyzed by using the volume of fluid-discrete phase model(VOFDPM)coupling model,the RNG k-ɛturbulence model and the dynamic grid technology.Furthermore,the optimization research on the casing structure is conducted.Experimental results show that the accessibility of metal particles is optimal when the gear speed is 6000 rad/min or the immersion depth is 24 mm.The density of metal particles exhibits a nonlinear relationship with their accessibility,and the particle size has a relatively small impact on their accessibility without an order of magnitude change.展开更多
基金Item Sponsored by National Science and Technology Support Program for 11th Five-Year Plan of China(2006BAE03A00)
文摘The slag melting characteristic of slag forming and slag splashing for 300 t BOF less slag process is researched by combining the methods of the slag chemical composition, the melting point determination and the petrographic analysis. The results show that the melting point of final slag for less slag smelting is 20 ~C lower than that for conventional smelting. According to results of the petrographic analysis, the C3S （3CaO ~ SiO2） and C2S （2CaO · SiO2） content for less slag smelting are lower than those for conventional smelting, while the RO （FeO, MgO, MnO, etc） phase and C4AF （4CaO · Al2O3· Fe2O3） phase are higher than those for conventional smelting. According to results of the chemical analysis, the （CaO） content and slag basicity for less slag smelting are higher than those for conventional smelting, while （FeO） and （MgO） content in slag for less slag smelting are almost equal to those for conventional smelting. The reason why slag melting point for less slag smelting is lower than that for con- ventional smelting is that the quantity of added fluorite for less slag smelting is more than that for conventional smel- ting. According tO the analysis results the slag melting point is determined by the C3S, C2S, RO phase and C4AF content. According to the results of slag melting characteristic before and after slag splashing for less slag smelting, the present adjusting slag process has little effect. It is important to adjust the composition of BOF final slag. The （FeO） content in slag is to be reduced at the slag splashing and adjusting slag process for less slag smelting.
基金Sponsored by Science and Technology Plan Projects of Tianjin of China(07ZCKFGX03800)Science and Technology Plan Projects for CAS Supporting Tianjin Construction of China(TJZX1-YW-09)
文摘Converter off-gas, an important energy resource for steel industries, is one of the weak points in the recov ery and utilization of secondary energy resources. To improve the level of recycling converter off-gas in steel plants, a novel approach to the recycle of CO2 separated from converter off-gas or other off-gas for the green slag splashing technique was developed, and the CO2 equilibrium conversion ratio of the green CO2 slag splashing under different technological conditions was calculated by the program of enthalpy （H）, entropy （S）, and heat capacity （C）, i.e. HSC software. Furthermore, the experiments of CO2 injected into molten converter slag were carried out, and the influencing factors of the green slag splashing technique using CO2 were analyzed. The experimental results showed that the carbon content for smooth slag splashing using COs was about 4.0%.
文摘The sudden transition from a high-velocity, supercritical open channel flow into a slow-moving sub-critical flow is a hydraulic jump. Such a flow is characterised by a sudden rise of the free-surface, with some strong energy dissipation and air entrainment, waves and spray. New two-phase flow measurements were performed in the developing flow region using a large-size facility operating at large Reynolds numbers. The experimental results demonstrated the complexity of the flow with a developing mixing layer in which entrained bubbles are advected in a high shear stress flow. The relationship between bubble count rates and void fractions was non-unique in the shear zone, supporting earlier observations of some form of double diffusion process between momentum and air bubbles. In the upper region, the flow consisted primarily of water drops and packets sur-rounded by air. Visually significant pray and splashing were significant above the jump roller. The present study is the first com-prehensive study detailing the two-phase flow properties of both the bubbly and spray regions of hydraulic jumps, a first step towards understanding the interactions between bubble entrainment and droplet ejection processes.
文摘Some differences in slag splashing between BOF steel works in US and China were investigated. The slag composition,melting point, and mineralogical phases of final slags from both countries were studied. The control of slag superheat is important to an effective slag coating.
基金supported by: the National Key Research and Development Program of China (Grant No. 2021YFC2800700)the National Natural Science Foundation of China (Grant Nos. 52171329 and 12002404)+2 种基金the Natural Science Foundation of Guangdong Province of China (Grant No. 2022A1515012084)the Fundamental Research Funds for the Central Universities, Sun Yat-sen University (Grant No. 231gbi023)supported by the GHfund A (Grant No. ghfund202302014084)
文摘In recent years,forest fires and maritime accidents have occurred frequently,which have had a bad impact on human production and life.Thus,the development of seaplanes is an increasingly urgent demand.It is important to study the taxiing process of seaplanes for the development of seaplanes,which is a strong nonlinear fluid-structure interaction problem.In this paper,the smoothed particle hydrodynamics(SPH)method based on the Lagrangian framework is utilized to simulate the taxiing process of seaplanes,and the SPH results are compared with those of the finite volume method(FVM)based on the Eulerian method.The results show that the SPH method can not only give the same accuracy as the FVM but also have a strong ability to capture the splashing waves in the taxiing process,which is quite meaningful for the subsequent study of the effect of a splash on other parts of the seaplane.
文摘The measured results show that the overexpanded supersonic jet velocity produced by low stagnation pressure (0.53 MPa) attenuates quickly, deviates greatly with smaller impact area and large energy loss. According to the measured results and the analysis of lashing energy of jet on the bath, the technological parameters of nitrogen flow in slag splashing were proposed.
基金Funded by the State Key Laboratory for Mechanical Behavior of Materials(20131312)the Special Fund for Basic Scientific Research of Central CollegesChang’an University(Nos.310831161018,2014G1311093,and 2014G1311082)
文摘To understand the effects of spray parameters on the splashing,cast iron particles were plasma-sprayed onto polished surfaces of aluminum substrate to form single splats.Various plasma arc powers and spray distances were applied to adjust the morphology of the splats which was studied using a field emission scanning electron microscope（FESEM）.The experimentalresults showed that the splashing of impinging droplets was significantly restrained for the splats deposited with high arc power（30 k W）and short spray distance（80 mm）.This finding would be beneficialto improving the adhesive strength of the coating.
文摘The influence of three different blowing conditions on the slag splashing process in a basic oxygen furnace for steelmaking is analyzed here using two-dimensional transient Computational Fluid Dynamics simulations. Four blowing conditions are considered in the computer runs: top blowing, combined blowing using just a bottom centered nozzle, combined blowing using two bottom lateral nozzles, and full combined blowing using the three top and the three bottom nozzles. Computer simulations show that full combined blowing provides greater slag splashing than conventional top blowing.
文摘Physical properties of molten slag such as viscosity, density and surface tension have a significant influence on the slag splashing process in an oxygen steelmaking converter. Particularly, viscosity determines the shear forces that rule droplets formation. Besides, stirring of the molten slag bath strongly depends on this property. In this work, the influence of viscosity on the efficiency of slag splashing is explored by means of transient Computational Fluid Dynamics simulations. Several values of viscosity are employed in the computer experiments. In order to quantify the splashing efficiency as function of slag viscosity, an average slag fraction on the converter walls is defined and calculated. CFD results are compared with those of an empirical expression, and at least qualitative agreement is found.
基金This work was supported by the National Key R&D Program of China(2021YFC2901200)National Natural Science Foundation of China(52174383)+2 种基金Liaoning Provincial Natural Science Foundation of China(2022-YQ-09)Open Project of State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization(GZ-2022-DK-003)Fundamental Research Funds for the Central Universities(Grant No.N2225007).
文摘Basic oxygen steelmaking(BOS)is the most frequently used method to produce molten steel,which is being developed to meet the requirements of being safe,efficient,clean,and intelligent.During the BOS process,splashing events cause undesirable consequences,such as casualties,low efficiency,environmental pollution,and uncontrollable operation.The causes of three types of splashing(eruptive,foaming,and metallic splashing)were unraveled and it is concluded that inappropriate foaming is the root cause of splashing.A variety of monitoring techniques for splashing have been developed to measure real-time slag foaming in a basic oxygen furnace(BOF).The audiometry technique with flexible operation and high accuracy was comprehensively introduced with a practical application.Based on the formation mechanisms,the countermeasures for the three types of splashing were proposed to regulate slag foaming in a BOF by integrating diverse measures in terms of raw materials,slag forming,blowing pattern,and the use of splashing regulating agents.Future work should emphasise an automatic action for these prevention measures in response to the splashing risk from the monitoring technology,promoting the progress of intelligent steelmaking.
文摘SeveraL parameters affecting slag splashing in LD converter have been discussed. Using parffin and starch model, a simulated test about 30 t converter has been made in laboratory and the modified Frode numberwas chosen as the main similar basis of the system. It was results that the optimized slag splashing parameters wasobtained through data treatment The nitrogen gas flow rate is about 8 500 m3/h, the splashing time is of 3 min,and the lance height is of 0.8 m. It is necessary to add MgO or carbon into the slag to adjusting slag composition.Also, it is difficult for the splashed slag condensing on the line when the slag temperature is much higher
文摘Some variables that influence the slag splashing phenomenon in an oxygen steelmaking converter are numerically analyzed in this work. The effect of lance height, jet velocity, jet exit angle and slag viscosity on the washing and ejection mechanisms of slag splashing is studied employing transient two-dimensional computational fluid dynamics simulations. A parameter here called average slag volume fraction is proposed for the quantitative evaluation of the slag splashing efficiency. Besides, a qualitative comparison is made between the computational fluid dynamics results and physical model results from literature.
文摘“It's coming!”Liu Fuhai shouted,lying prone on a rock,one of his eyes pressed against his camera.Beads of sweat could be seen on his forehead.Roaring water in the Yellow River plunged from the cliff,making gigantic splashes(落水声)which eventually turned into thick mists.Liu,holding his breath,clicked the shutter quickly to capture the grandeur of the Hukou Waterfall,the largest waterfall on the Yellow River.
基金supported in part by the National Natural Science Foundation of China(No.52276009)。
文摘Accurate simulation of ice accretion of supercooled large droplet(SLD)is pivotal for the international airworthiness certification of large aircraft.Its complex dynamics behavior and broad particle size distributions pose significant challenges to reliable CFD predictions.A numerical model of multi-particle SLD coupling breaking,bouncing and splashing behaviors is established to explore the relationship between dynamics behavior and particle size.The results show that the peak value of droplet collection efficiencyβdecreases due to splashing.The bounce phenomenon will make the impact limit S_(m)of the water drops decrease.With the increase of the SLD particle size,the water drop bounce point gradually moves toward the trailing edge of the wing.The critical breaking diameter of SLD at an airflow velocity of 50 m/s is approximately 100μm.When the SLD particle size increases,the height of the water droplet shelter zone on the upper edge of the wing gradually decreases,and the velocity in the Y direction decreases first and then increases in the opposite direction,increasing the probability of SLD hitting the wing again.Large particle droplets have a higher effect on the impact limit S_(m)than smaller droplets.Therefore,in the numerical simulation of the SLD operating conditions,it is very important to ensure the proportion of large particle size water droplets.
文摘The Water-Sprinkling Festival of the Dai ethnic group is the most widely celebrated rite among the ethnic minorities living in Yunnan province.This weeklong celebration,marking the Dai Lunar New Year,usually falls around mid-April.People of all ages,dressed in their festival best,take part in the solemn ritual of washing statues of Buddha.They later take great
基金the Applied Basic Research Project of Yunnan Province,China(No.202301 AT070411).
文摘The variation characteristics of bubble morphology and the thermal-physical properties of bubble boundary in the top-blown smelting furnace were explored by means of the computational fluid dynamics method.The essential aspects of the fluid phase(e.g.,splashing volume,dead zone of copper slag,and gas penetration depth)were explored together with the effect of sinusoidal pulsating gas intake on the momentum-transfer performance between phases.The results illustrated that two relatively larger vortices and two smaller vortices appear in the bubble waist and below the lance,respectively.The expansion of larger ones as well as the shrinking of smaller ones combine to cause the contraction of the bubble waist.Compared to the results of the case with a fixed gas injection velocity(V_(g)=58 m/s),the splashing volume and dead zone volume of the slag under the V_(g)=58+10sin(2πt)condition are reduced by 24.9%and 23.5%,respectively,where t represents the instant time.Gas penetration depth and slag motion velocity of the latter are 1.03 and 1.31 times high-er than those of the former,respectively.
基金supported by the Independent Research and Development Projects of State Key Laboratory of Heavy Duty AC Drive Electric Locomotive Systems Integration(No.R111720H01385),China.
文摘In this study,we investigate the effect of rail vibrations on the lubrication and efficiency of a splash-lubricated gearbox;specifically,the gearbox of a rail-transit vehicle.A high-fidelity 3D numerical model of the gearbox in a moving reference system is described,as well as computational fluid dynamics(CFD)simulations of the gearbox with different vibration directions.The effects of rotational speed,oil-immersion depth,and different oil-injection volume rates on lubrication and efficiency are discussed.We propose a method of evaluating the internal lubrication condition of a splash-lubricated gearbox and quantitatively compare the effects of different operating parameters on lubrication and efficiency.Finally,our experiment to verify the feasibility of the simulation method is described.The results show that with vibration,the churning loss and oil supply for the bearings are significantly higher than those under static conditions.In addition,among different vibrational directions,lateral vibration has the greatest influence on the lubrication condition and efficiency of the gearbox.For the studied railway-vehicle gearbox,the best lubrication condition is achieved at a rotational speed of 1600 r/min and an oil-immersion depth of two times the tooth height(2.Oh).Rotational speed is the operating parameter that has the most significant effect on the lubrication and efficiencyofthegearbox.
基金Supported by the Guangdong Provincial Natural Science Foundation of China under Grant No.2021A1515011917the National Natural Science Foundation of China under Grant No.52371344 and U22A2012+1 种基金Fundamental Research Funds for the Central Universities,Sun Yat-sen University under Grant No.22qntd0601the start-up funding to Y.J.from Sun Yat-sen University.
文摘To explore the water entry flow and impact load characteristics of northern gannets,we conducted water entry experiments using a northern gannet’s head model based on three-dimensional(3D)printing and several cone models under different Froude numbers.A high-speed camera was used to capture flow images,and an inertial measurement unit(IMU)was used to record the water entry impact loads.The results indicate that the geometric topology of the model considerably influenced the water entry flow and impact load.Specifically,the northern gannet’s head model created a smaller water entry splash crown,cavity geometry,and impact load compared with the cone models of similar sizes.
基金supported by the Na‑tional Natural Science Foundation of China(No.52075241)the National Key Laboratory of Science and Technology on Helicopter Transmission(Nanjing University of Aeronau‑tics and Astronautics)(Nos.HTL-A-22K04 and HTL-O21G13).
文摘The intermediate gearbox of a helicopter operates under splash lubrication.If the bearing produces metal particles due to insufficient lubrication or wear,whether it can be adsorbed by the metal particles signal at the bottom of the gearbox and alarm directly affects the flight safety of the helicopter.Based on the CFD method,the factors affecting the accessibility of metal particles are analyzed by using the volume of fluid-discrete phase model(VOFDPM)coupling model,the RNG k-ɛturbulence model and the dynamic grid technology.Furthermore,the optimization research on the casing structure is conducted.Experimental results show that the accessibility of metal particles is optimal when the gear speed is 6000 rad/min or the immersion depth is 24 mm.The density of metal particles exhibits a nonlinear relationship with their accessibility,and the particle size has a relatively small impact on their accessibility without an order of magnitude change.
