With its high strength and hardness, wear-resistant steel has become an important material in the field of construction machinery manufacturing.Given that quenching technology is a crucial component of wear-resistant ...With its high strength and hardness, wear-resistant steel has become an important material in the field of construction machinery manufacturing.Given that quenching technology is a crucial component of wear-resistant steel production, the selection of the cooling method to be used during this process is important.In this study, the feasibility of quenching wear-resistant steel by air-atomized water spray cooling was studied, and the cooling rate, microstructure, and hardness of wear-resistant steel under various cooling device structures were analyzed.The results reveal that the air-atomized water spray cooling method is an effective technique in quenching wear-resistant steel.Furthermore, martensite and uniform hardness were obtained by the air-atomized water spray cooling technique.As the space between the nozzles in each row in the device increased, the cooling rate was reduced during quenching.Meanwhile, the martensite content decreased, and more carbides were observed in the martensitic structure.A mixture comprising self-tempered martensite and bainite was formed at a large distance over a longer period of time.All these factors resulted in lower hardness and worse property uniformity.展开更多
Owing to the increasing worldwide demand for natural gas,the development of a large submerged combustion vaporizer is required.Its burner is equipped with a water spray nozzle to reduce nitrogen oxides,and a practi-ca...Owing to the increasing worldwide demand for natural gas,the development of a large submerged combustion vaporizer is required.Its burner is equipped with a water spray nozzle to reduce nitrogen oxides,and a practi-cal simulation method is required for the optimal design.The non-adiabatic flamelet approach can predict the combustion emissions and is useful for reducing simulation costs.However,as the number of control variables increases,the database requires larger memory and cannot be dealt with by general computers.In this study,an artificial neural network(ANN)model based on a five-dimensional flamelet database,which includes the effects of heat loss and vapor concentration by sprayed water evaporation,is developed.Furthermore,large eddy sim-ulations(LESs)for turbulent combustion fields with and without water spray are conducted employing flamelet generated manifold(FGM)approach with this ANN model,and the validity is investigated.For comparison,a lab-scale burner equipped with a water spray nozzle is manufactured,and combustion experiments with and without water spray are conducted.The results show that CO,NO,temperature,and reaction rate of progress variable predicted by the present ANN model are in good agreement with those of a five-dimensional flamelet database.In the condition without water spray,the flame behavior predicted by the LES employing the FGM/ANN ap-proach is in good agreement with that employing the conventional FGM approach,while indicating much lower memory,although there appeared some quantitative discrepancies in the temperature against the experiment probably partially because of the insufficiency of the FGM approach for the present complex flame structure.In the condition with water spray,the LES employing the FGM/ANN approach is able to capture the effect of the water spray on the flame behavior in the experiment,such that the water spray decreases the temperature,which causes the decrease in NO but increase in CO.展开更多
A finite element is established for analyzing the dynamical mechanics and deformation of steel frame at high temperature when it is rapidly cooled down by spray water in fire fighting, The simulation result shows that...A finite element is established for analyzing the dynamical mechanics and deformation of steel frame at high temperature when it is rapidly cooled down by spray water in fire fighting, The simulation result shows that remarkable mechanical coupling effects are produced in the process, and the sectional stress in rapid cooling down is found considerably larger than that in heating-up. Meanwhile, the stress and deformation of a beam mainly related to cooling rate and location are much larger than those of a column in rapid cooling, In fire fighting, the structure on the first or second floor was more dangerous than those on other floors in rapid cooling, These results could provide a theoretical reference for the design of steel structure and fire fighting.展开更多
Electric discharge in and in contact with water can accompany ultraviolet(UV)radiation and electron impact, which can generate a large number of active species such as hydroxyl radicals(OH), oxygen radical(O), o...Electric discharge in and in contact with water can accompany ultraviolet(UV)radiation and electron impact, which can generate a large number of active species such as hydroxyl radicals(OH), oxygen radical(O), ozone(O_3) and hydrogen peroxide(H_2O_2). In this paper, a nonthermal plasma processing system was established by means of dielectric barrier discharge(DBD)arrays in water mist spray. The relationship between droplet size and water content was examined,and the effects of the concentrations of oxides in both treated water and gas were investigated under different water content and discharge time. The relative intensity of UV spectra from DBD in water mist was a function of water content. The concentrations of both O_3 and nitrogen dioxide(NO_2) in DBD room decreased with increasing water content. Moreover, the concentrations of H_2O_2, O_3 and nitrogen oxides(NOx) in treated water decreased with increasing water content,and all the ones enhanced after discharge. The experimental results were further analyzed by chemical reaction equations and commented by physical principles as much as possible. At last,the water containing phenol was tested in this system for the concentration from 100 mg/L to9.8 mg/L in a period of 35 min.展开更多
To make full use of plant shellfibers(rice husk,walnut shell,chestnut shell),three kinds of wood-plastic com-posites of plant shellfibers and polyvinyl chloride(PVC)were prepared.X-ray diffraction analysis was carried o...To make full use of plant shellfibers(rice husk,walnut shell,chestnut shell),three kinds of wood-plastic com-posites of plant shellfibers and polyvinyl chloride(PVC)were prepared.X-ray diffraction analysis was carried out on three kinds of plant shellfibers to test their crystallinity.The aging process of the composites was conducted under 2 different conditions.One was artificial seawater immersion and xenon lamp irradiation,and the other one was deionized water spray and xenon lamp irradiation.The mechanical properties(tensile strength,flexural strength,impact strength),changes in color,water absorption,Fourier transform infrared spectroscopy(FTIR),and microstructures of the composites before and after the two aging experiments were analyzed.The results showed that the chestnut shell had the highest crystallinity,which was 42%.The chestnut shell/PVC composites had the strongest interface bonding,the least internal defects,and the best general mechanical properties among the three composites.Its tensile strength,bending strength and impact strength were 23.81 MPa,34.12 MPa,and 4.32 KJ·m^(-2),respectively.Comparing the two aging conditions,artificial seawater immersion and xenon lamp irradiation destroyed the quality of the combination of plant shellfibers and PVC,making the internal defects of the composites increase.This made the water absorption ability and changes in the color of the composites more obvious and led to a great decrease in the mechanical properties.The general mechanical properties of the chestnut shell/PVC composites were the best,but their water absorption ability changed more obviously.展开更多
Accumulation of float coal dust(FCD)in underground mines is an explosion hazard that affects all underground coal mine workers.While this hazard is addressed by the application of rock dust,inadequate rock dusting pra...Accumulation of float coal dust(FCD)in underground mines is an explosion hazard that affects all underground coal mine workers.While this hazard is addressed by the application of rock dust,inadequate rock dusting practices can leave miners exposed to an explosion risk.Researchers at the National Institute for Occupational Safety and Health(NIOSH)have focused on developing a water curtain that removes FCD from the airstream,thereby reducing the buildup of FCD in mine airways.In this study,the number and spacing of the active sprays in the water curtain were varied to determine the optimal configuration to obtain peak knockdown efficiency(KE)while minimizing water consumption.展开更多
文摘With its high strength and hardness, wear-resistant steel has become an important material in the field of construction machinery manufacturing.Given that quenching technology is a crucial component of wear-resistant steel production, the selection of the cooling method to be used during this process is important.In this study, the feasibility of quenching wear-resistant steel by air-atomized water spray cooling was studied, and the cooling rate, microstructure, and hardness of wear-resistant steel under various cooling device structures were analyzed.The results reveal that the air-atomized water spray cooling method is an effective technique in quenching wear-resistant steel.Furthermore, martensite and uniform hardness were obtained by the air-atomized water spray cooling technique.As the space between the nozzles in each row in the device increased, the cooling rate was reduced during quenching.Meanwhile, the martensite content decreased, and more carbides were observed in the martensitic structure.A mixture comprising self-tempered martensite and bainite was formed at a large distance over a longer period of time.All these factors resulted in lower hardness and worse property uniformity.
基金The temperature measurements and PIA were supported by Prof.M.Nishioka of University of Tsukuba and Prof.K.Nishino of Yokohama National University,respectively.This work was partially supported by MEXT as"Program for Promoting Researches on the Supercomputer Fu-gaku"(Digital Twins of Real World’s Clean Energy Systems with Inte-grated Utilization of Super-simulation and AI).
文摘Owing to the increasing worldwide demand for natural gas,the development of a large submerged combustion vaporizer is required.Its burner is equipped with a water spray nozzle to reduce nitrogen oxides,and a practi-cal simulation method is required for the optimal design.The non-adiabatic flamelet approach can predict the combustion emissions and is useful for reducing simulation costs.However,as the number of control variables increases,the database requires larger memory and cannot be dealt with by general computers.In this study,an artificial neural network(ANN)model based on a five-dimensional flamelet database,which includes the effects of heat loss and vapor concentration by sprayed water evaporation,is developed.Furthermore,large eddy sim-ulations(LESs)for turbulent combustion fields with and without water spray are conducted employing flamelet generated manifold(FGM)approach with this ANN model,and the validity is investigated.For comparison,a lab-scale burner equipped with a water spray nozzle is manufactured,and combustion experiments with and without water spray are conducted.The results show that CO,NO,temperature,and reaction rate of progress variable predicted by the present ANN model are in good agreement with those of a five-dimensional flamelet database.In the condition without water spray,the flame behavior predicted by the LES employing the FGM/ANN ap-proach is in good agreement with that employing the conventional FGM approach,while indicating much lower memory,although there appeared some quantitative discrepancies in the temperature against the experiment probably partially because of the insufficiency of the FGM approach for the present complex flame structure.In the condition with water spray,the LES employing the FGM/ANN approach is able to capture the effect of the water spray on the flame behavior in the experiment,such that the water spray decreases the temperature,which causes the decrease in NO but increase in CO.
基金supported by the National Natural Science Foundation of China (51478002)
文摘A finite element is established for analyzing the dynamical mechanics and deformation of steel frame at high temperature when it is rapidly cooled down by spray water in fire fighting, The simulation result shows that remarkable mechanical coupling effects are produced in the process, and the sectional stress in rapid cooling down is found considerably larger than that in heating-up. Meanwhile, the stress and deformation of a beam mainly related to cooling rate and location are much larger than those of a column in rapid cooling, In fire fighting, the structure on the first or second floor was more dangerous than those on other floors in rapid cooling, These results could provide a theoretical reference for the design of steel structure and fire fighting.
基金supported by National Natural Science Foundation of China(Nos.11274092,51107033,11404092,11274091)the Nantong Science and Technology Project,China(No.BK2014024)+1 种基金the Open Project of Jiangsu Province Key Laboratory of Environmental Engineering,China(No.KF2014001)the Fundamental Research Funds for the Central Universities,China(No.2014B11414)
文摘Electric discharge in and in contact with water can accompany ultraviolet(UV)radiation and electron impact, which can generate a large number of active species such as hydroxyl radicals(OH), oxygen radical(O), ozone(O_3) and hydrogen peroxide(H_2O_2). In this paper, a nonthermal plasma processing system was established by means of dielectric barrier discharge(DBD)arrays in water mist spray. The relationship between droplet size and water content was examined,and the effects of the concentrations of oxides in both treated water and gas were investigated under different water content and discharge time. The relative intensity of UV spectra from DBD in water mist was a function of water content. The concentrations of both O_3 and nitrogen dioxide(NO_2) in DBD room decreased with increasing water content. Moreover, the concentrations of H_2O_2, O_3 and nitrogen oxides(NOx) in treated water decreased with increasing water content,and all the ones enhanced after discharge. The experimental results were further analyzed by chemical reaction equations and commented by physical principles as much as possible. At last,the water containing phenol was tested in this system for the concentration from 100 mg/L to9.8 mg/L in a period of 35 min.
基金This study was supported by the financial support of Natural Science Research Projects in Higher Education Institutions in Jiangsu Province(No.18KJD430002).
文摘To make full use of plant shellfibers(rice husk,walnut shell,chestnut shell),three kinds of wood-plastic com-posites of plant shellfibers and polyvinyl chloride(PVC)were prepared.X-ray diffraction analysis was carried out on three kinds of plant shellfibers to test their crystallinity.The aging process of the composites was conducted under 2 different conditions.One was artificial seawater immersion and xenon lamp irradiation,and the other one was deionized water spray and xenon lamp irradiation.The mechanical properties(tensile strength,flexural strength,impact strength),changes in color,water absorption,Fourier transform infrared spectroscopy(FTIR),and microstructures of the composites before and after the two aging experiments were analyzed.The results showed that the chestnut shell had the highest crystallinity,which was 42%.The chestnut shell/PVC composites had the strongest interface bonding,the least internal defects,and the best general mechanical properties among the three composites.Its tensile strength,bending strength and impact strength were 23.81 MPa,34.12 MPa,and 4.32 KJ·m^(-2),respectively.Comparing the two aging conditions,artificial seawater immersion and xenon lamp irradiation destroyed the quality of the combination of plant shellfibers and PVC,making the internal defects of the composites increase.This made the water absorption ability and changes in the color of the composites more obvious and led to a great decrease in the mechanical properties.The general mechanical properties of the chestnut shell/PVC composites were the best,but their water absorption ability changed more obviously.
文摘Accumulation of float coal dust(FCD)in underground mines is an explosion hazard that affects all underground coal mine workers.While this hazard is addressed by the application of rock dust,inadequate rock dusting practices can leave miners exposed to an explosion risk.Researchers at the National Institute for Occupational Safety and Health(NIOSH)have focused on developing a water curtain that removes FCD from the airstream,thereby reducing the buildup of FCD in mine airways.In this study,the number and spacing of the active sprays in the water curtain were varied to determine the optimal configuration to obtain peak knockdown efficiency(KE)while minimizing water consumption.