As a potent grain refiner for steel casting,TiN is now widely used to refineγ-austenite in steel additive manufacturing(AM).However,the refining mechanism of TiN during AM remains unclear despite intensive research i...As a potent grain refiner for steel casting,TiN is now widely used to refineγ-austenite in steel additive manufacturing(AM).However,the refining mechanism of TiN during AM remains unclear despite intensive research in recent years.This work aims to boost our understanding on the mechanism of TiN in refining theγ-austenite in AM-fabricated 316 stainless steel and its corresponding effect on the mechanical behaviour.Experimental results show that addition of 1 wt.%TiN nanoparticles led to complete columnarto-equiaxed transition and significant refinement of the austenite grains to∼2μm in the 316 steel.Thermodynamic and kinetic simulations confirmed that,despite the rapid AM solidification,δ-ferrite is the primary solid phase during AM of the 316 steel andγ-austenite forms through subsequent peritectic reaction or direct transformation from theδ-ferrite.This implies that the TiN nanoparticles actually refined theδ-ferrite through promoting its heterogenous nucleation,which in turn refined theγ-austenite.This assumption is verified by the high grain refining efficiency of TiN nanoparticles in an AM-fabricated Fe-4 wt.%Siδ-ferrite alloy,in whichδ-ferrite forms directly from the melt and is retained at room temperature.The grain refinement is attributed to the good atomic matching betweenδ-ferrite and TiN.Grain refinement in the 316 steel through 1 wt.%TiN inoculation not only eliminated the property anisotropy but also led to a high strain-hardening rate upon plastic deformation and thereby a superior strengthductility synergy with yield strength of 561 MPa,tensile strength of 860 MPa and elongation of 48%.展开更多
There are great interests to capture the CO2 to control the greenhouse gas emission.Amine absorption of CO2 is being taken as an effective way to capture CO2 in industry.However,the amine absorption of CO2 is cost-ine...There are great interests to capture the CO2 to control the greenhouse gas emission.Amine absorption of CO2 is being taken as an effective way to capture CO2 in industry.However,the amine absorption of CO2 is cost-ineffective due to great energy consumption and solution consumption.In order to reduce the capture cost,catalyst fluidization is proposed here to intensify the mass transfer and heat transfer.Catalyst fluidization with field synergy and DFT model is developed by incorporating the effects of catalyst reaction kinetics,drag force and multi-field into the mass transfer,heat transfer,fluid flow and catalyst collision.Experiments with an improved distributor are performed well to validate the model.The reaction kinetics is determined by the DFT simulation and experiment.The mass transfer coefficient in the fluidized reactor is identified as 17%higher than the conventional packed reactor.With the field synergy of catalyst fluidization,the energy consumption for CO2 desorption is reduced by 9%.Stepwise operation and inclination reactor are used to improve catalyst fluidization process.展开更多
The differences of coalbed methane(CBM) desorption-diffusion from coal drilling-core under various drilling fluid medium are not considered in the present calculating methods of lost CBM quantity,which leads possibly ...The differences of coalbed methane(CBM) desorption-diffusion from coal drilling-core under various drilling fluid medium are not considered in the present calculating methods of lost CBM quantity,which leads possibly to the inaccuracy of CBM quantity in coal seam.Here we took the desorption of CBM from coal core under drilling fluid medium as a pressure-swing process,and based on the Langmuir equation and Fick-first law,established the desorption-diffusion model and numerical modeling method of lost gas(including free CBM) calculation in coal core under various drilling fluid mediums through physical simulation test and by considering comprehensively primary factors.The results showed that the physical simulated t-Qt curves can be rightly fitted by the numerical modeling data,which indicated the ultimate desorption quantity from the numerical modeling was adjacent to that from the physical simulation as a whole.It was found that the lost CBM quantity from the modeling method was generally higher than that from the direct method when lost time was relatively long.Thus,we sug-gest that it is necessary to emend the active China national standard through further investigation,since the lost CBM quantity from coal drilling-core was generally underestimated using the method in the current standard.展开更多
Vibrating separation is a significant method for liquid-solid separation.A typical example is the vibrating screen to dewater wet granular matter.The properties of granular matter and the vibrating parameters signific...Vibrating separation is a significant method for liquid-solid separation.A typical example is the vibrating screen to dewater wet granular matter.The properties of granular matter and the vibrating parameters significantly affect the separation efficiency.This study investigates the effect of vibration parameters in separation based on the breakage of large-scale liquid bridge numerically by using a calibrated simulation model.Through analysing the simulation results,the liquid bridge shape and the volume between two sphere particles for various particle sizes and particle distances were studied in the static condition under the effect of gravity.The results show a general reducing trend of liquid bridge volume when the radius ratio of two particles increases,particularly when the ratio increases to 5.Additionally,a set of vibrating motion was applied to the liquid bridge in the simulation model.A group of experiments were also performed to validate the simulation model with vibration.Then,the effect of vibrating peak acceleration,distance between spheres and radius on the separation efficiency which was reflected by the residual water were investigated.It is found that separation efficiency increased obviously with the peak acceleration and the increase slowed down after the peak acceleration over 1 m/s^(2).展开更多
Pore pressure is an important parameter in coalbed methane(CBM)exploration and development;however,the distribution pattern and mechanism for pore pressure differences in the Upper Permian CBM reservoirs are poorly un...Pore pressure is an important parameter in coalbed methane(CBM)exploration and development;however,the distribution pattern and mechanism for pore pressure differences in the Upper Permian CBM reservoirs are poorly understood in the western Guizhou region of South China.In this study,lateral and vertical variations and mechanisms for pore pressure differences are analyzed based on 126 injection-falloff and in-situ stress well test data measured in Permian coal reservoirs.Generally,based on the pore pressure gradient and coefficient in coal reservoirs of the western Guizhou region,five zones can be delineated laterally:the mining areas of Zhina,northem Liupanshui,northern Guizhou,northwestern Guizhou and southern Liupanshui.Vertically,there are two main typical patterns:i)the pore pressure gradient(or coefficient)is nearly unchanged in different coal reservoirs,and ii)the pore pressure gradient(or coefficient)has cyclic variations in a borehole profile with multiple coal seams,which suggests the existence of a"superimposed CBM system".The mechanism analysis indicates that coal permeability,thermal evolution stage and hydrocarbon generation contribute little to pore pressure differences in coal reservoirs in the western Guizhou region.The present-day in-situ stress field,basement structure and tectonic activity may be the dominant factors affecting lateral pore pressure differences.The sealing capacity of caprocks and the present-day in-situ stress field are significant para-meters causing vertical pore pressure differences in coal reservoirs.These results are expected to provide new geological references for CBM exploration and develop-ment in the western Guizhou region.展开更多
基金University of Queensland are very grateful to Australia Research Council(ARC)Discovery Project(DP210103162)program for funding support.Greta Lindwall acknowledges support from Vinnova,Formas and Energimyndigheten via LIGHTer Academy.
文摘As a potent grain refiner for steel casting,TiN is now widely used to refineγ-austenite in steel additive manufacturing(AM).However,the refining mechanism of TiN during AM remains unclear despite intensive research in recent years.This work aims to boost our understanding on the mechanism of TiN in refining theγ-austenite in AM-fabricated 316 stainless steel and its corresponding effect on the mechanical behaviour.Experimental results show that addition of 1 wt.%TiN nanoparticles led to complete columnarto-equiaxed transition and significant refinement of the austenite grains to∼2μm in the 316 steel.Thermodynamic and kinetic simulations confirmed that,despite the rapid AM solidification,δ-ferrite is the primary solid phase during AM of the 316 steel andγ-austenite forms through subsequent peritectic reaction or direct transformation from theδ-ferrite.This implies that the TiN nanoparticles actually refined theδ-ferrite through promoting its heterogenous nucleation,which in turn refined theγ-austenite.This assumption is verified by the high grain refining efficiency of TiN nanoparticles in an AM-fabricated Fe-4 wt.%Siδ-ferrite alloy,in whichδ-ferrite forms directly from the melt and is retained at room temperature.The grain refinement is attributed to the good atomic matching betweenδ-ferrite and TiN.Grain refinement in the 316 steel through 1 wt.%TiN inoculation not only eliminated the property anisotropy but also led to a high strain-hardening rate upon plastic deformation and thereby a superior strengthductility synergy with yield strength of 561 MPa,tensile strength of 860 MPa and elongation of 48%.
基金Supported by the National Natural Science Foundation of China(51506165 and21736008)the Natural Science Basic Research Plan in Shaanxi Province of China(2015JQ5192)Fundamental Research Funds for the Central Universities
文摘There are great interests to capture the CO2 to control the greenhouse gas emission.Amine absorption of CO2 is being taken as an effective way to capture CO2 in industry.However,the amine absorption of CO2 is cost-ineffective due to great energy consumption and solution consumption.In order to reduce the capture cost,catalyst fluidization is proposed here to intensify the mass transfer and heat transfer.Catalyst fluidization with field synergy and DFT model is developed by incorporating the effects of catalyst reaction kinetics,drag force and multi-field into the mass transfer,heat transfer,fluid flow and catalyst collision.Experiments with an improved distributor are performed well to validate the model.The reaction kinetics is determined by the DFT simulation and experiment.The mass transfer coefficient in the fluidized reactor is identified as 17%higher than the conventional packed reactor.With the field synergy of catalyst fluidization,the energy consumption for CO2 desorption is reduced by 9%.Stepwise operation and inclination reactor are used to improve catalyst fluidization process.
基金supported by the Key Project of National Natural Science Foundation of China (Grant No.40730422)Young Project of National Natural Science Foundation of China (Grant No.40802032)
文摘The differences of coalbed methane(CBM) desorption-diffusion from coal drilling-core under various drilling fluid medium are not considered in the present calculating methods of lost CBM quantity,which leads possibly to the inaccuracy of CBM quantity in coal seam.Here we took the desorption of CBM from coal core under drilling fluid medium as a pressure-swing process,and based on the Langmuir equation and Fick-first law,established the desorption-diffusion model and numerical modeling method of lost gas(including free CBM) calculation in coal core under various drilling fluid mediums through physical simulation test and by considering comprehensively primary factors.The results showed that the physical simulated t-Qt curves can be rightly fitted by the numerical modeling data,which indicated the ultimate desorption quantity from the numerical modeling was adjacent to that from the physical simulation as a whole.It was found that the lost CBM quantity from the modeling method was generally higher than that from the direct method when lost time was relatively long.Thus,we sug-gest that it is necessary to emend the active China national standard through further investigation,since the lost CBM quantity from coal drilling-core was generally underestimated using the method in the current standard.
文摘Vibrating separation is a significant method for liquid-solid separation.A typical example is the vibrating screen to dewater wet granular matter.The properties of granular matter and the vibrating parameters significantly affect the separation efficiency.This study investigates the effect of vibration parameters in separation based on the breakage of large-scale liquid bridge numerically by using a calibrated simulation model.Through analysing the simulation results,the liquid bridge shape and the volume between two sphere particles for various particle sizes and particle distances were studied in the static condition under the effect of gravity.The results show a general reducing trend of liquid bridge volume when the radius ratio of two particles increases,particularly when the ratio increases to 5.Additionally,a set of vibrating motion was applied to the liquid bridge in the simulation model.A group of experiments were also performed to validate the simulation model with vibration.Then,the effect of vibrating peak acceleration,distance between spheres and radius on the separation efficiency which was reflected by the residual water were investigated.It is found that separation efficiency increased obviously with the peak acceleration and the increase slowed down after the peak acceleration over 1 m/s^(2).
基金supported by Natural Science Foundation of Jiangsu Province,China(No.BK20201349)National Natural Science Foundation of China(Grant Nos.41702130 and 41971335)Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘Pore pressure is an important parameter in coalbed methane(CBM)exploration and development;however,the distribution pattern and mechanism for pore pressure differences in the Upper Permian CBM reservoirs are poorly understood in the western Guizhou region of South China.In this study,lateral and vertical variations and mechanisms for pore pressure differences are analyzed based on 126 injection-falloff and in-situ stress well test data measured in Permian coal reservoirs.Generally,based on the pore pressure gradient and coefficient in coal reservoirs of the western Guizhou region,five zones can be delineated laterally:the mining areas of Zhina,northem Liupanshui,northern Guizhou,northwestern Guizhou and southern Liupanshui.Vertically,there are two main typical patterns:i)the pore pressure gradient(or coefficient)is nearly unchanged in different coal reservoirs,and ii)the pore pressure gradient(or coefficient)has cyclic variations in a borehole profile with multiple coal seams,which suggests the existence of a"superimposed CBM system".The mechanism analysis indicates that coal permeability,thermal evolution stage and hydrocarbon generation contribute little to pore pressure differences in coal reservoirs in the western Guizhou region.The present-day in-situ stress field,basement structure and tectonic activity may be the dominant factors affecting lateral pore pressure differences.The sealing capacity of caprocks and the present-day in-situ stress field are significant para-meters causing vertical pore pressure differences in coal reservoirs.These results are expected to provide new geological references for CBM exploration and develop-ment in the western Guizhou region.
