Tracer gas technique is a method to analyze the airflow path, measure the airflow quantity, and detect any recirculation or leakages in underground mine. In addition, it is also possible to evaluate the axial gas diff...Tracer gas technique is a method to analyze the airflow path, measure the airflow quantity, and detect any recirculation or leakages in underground mine. In addition, it is also possible to evaluate the axial gas diffusion of gas in turbulent bulk flow by utilizing the tracer gas data. This paper discussed about the measurement using tracer gas technique in Cibaliung Underground Mine, Indonesia and the evaluation of effective axial diffusion coefficient, E, by numerical simulation. In addition, a scheme to treat network flow in mine ventilation system was also proposed. The effective axial diffusion coefficient for each airway was evaluated based on Taylor's theoretical equation. It is found that the evaluated diffusion coefficient agrees well with Taylor's equation by considering that the wall friction factor, f, is higher than those for smooth pipe flow. It also shows that the value of effective diffusion coefficient can be inherently determined and the value is constant when matching with other measurements. Furthermore, there are possibilities to utilize the tracer gas measurement data to evaluate the airway friction factors.展开更多
Hydrogen diffusion coefficients of different regions in the welded joint of X80 pipeline steel were measured using the electro-chemical permeation technique. Using ABAQUS software, hydrogen diffusion in X80 pipeline s...Hydrogen diffusion coefficients of different regions in the welded joint of X80 pipeline steel were measured using the electro-chemical permeation technique. Using ABAQUS software, hydrogen diffusion in X80 pipeline steel welded joint was studied in consideration of the inhomogeneity of the welding zone, and temperature-dependent thermo-physical and mechanical properties of the metals. A three dimensional finite element model was developed and a coupled thermo-mechanical-diffusion analysis was performed. Hydrogen concentration distribution across the welded joint was obtained. It is found that the postweld residual hydrogen exhibits a non-uniform distribution across the welded joint. A maximum equivalent stress occurs in the immediate vicinity of the weld metal. The heat affected zone has the highest hydrogen concentration level, followed by the weld zone and the base metal.Simulation results are well consistent with theoretical analysis.展开更多
We numerically simulated and experimentally studied the interfacialcarbon diffusion between diamond tooland workpiece materials.A diffusion modelwith respect to carbon atoms of diamond toolpenetrating into chips and m...We numerically simulated and experimentally studied the interfacialcarbon diffusion between diamond tooland workpiece materials.A diffusion modelwith respect to carbon atoms of diamond toolpenetrating into chips and machined surface was established.The numericalsimulation results of the diffusion process revealthat the distribution laws of carbon atoms concentration have a close relationship with the diffusion distance,the diffusion time,and the originalcarbon concentration of the work material.In addition,diamond face cutting tests of die steels with different carbon content are conducted at different depth of cuts and feed rates to verify the previous simulation results.The micro-morphology of the chips is detected by scanning electron microscopy.Energy dispersive X-ray analysis was proposed to investigate the change in carbon content of the chips surface.The experimentalresults of this work are of benefit to a better understanding on the diffusion wear mechanism in single crystaldiamond cutting of ferrous metals.Moreover,the experimentalresults show that the diffusion wear of diamond could be reduced markedly by applying ultrasonic vibration to the cutting toolcompared with conventionalturning.展开更多
Background Petrochemical products possess a high risk of flammability,explosivity,and toxicity,making petrochemical accidents exceedingly destructive.Therefore,disaster analysis,prediction,and real-time simulations ha...Background Petrochemical products possess a high risk of flammability,explosivity,and toxicity,making petrochemical accidents exceedingly destructive.Therefore,disaster analysis,prediction,and real-time simulations have become important means of controlling and reducing accident hazards.Methods This study proposes a complete real-time simulation solution of gas diffusion with coordinate and concentration data,which was mainly aimed at simulating the types of harmful gas leakage and diffusion accidents in the petrochemical industry.The rendering effect was more continuous and accurate through grid homogenization and trilinear interpolation.This study presents a data processing and rendering parallelization process to enhance simulation efficiency.Gas concentration and fragment transparency were combined to synthesize transparent pixels in a scene.To ensure the approximate accuracy of the rendering effect,improve the efficiency of real-time rendering,and meet the requirement of intuitive perception using concentration data,a weighted blended order-independent transparency(OIT)with enhanced alpha weight is presented,which can provide a more intuitive perception of the hierarchical information of concentration data while preserving depth information.This study compares and analyzes three OIT algorithms-depth peeling,weighted blended OIT,and weighted blended OIT with enhanced alpha weight-in terms of rendering image quality,rendering time,required memory,and hierarchical information.Results Using weighted blended OIT with an enhanced alpha weight technique,the rendering time was shortened by 53.2%compared with that of the depth peeling algorithm,and the texture memory required was significantly smaller than that of the depth peeling algorithm.The rendering results of weighted blended OIT with an enhanced alpha weight were approximately accurate compared with those of the depth peeling algorithm as the ground truth,and there was no popping when surfaces passed through one another.Simultaneously,compared with weighted blended OIT,weighted blended OIT with an enhanced alpha weight achieved an intuitive perception of the hierarchical information of concentration data.展开更多
The rapid diffusion of nanoparticles （NPs） through mucus layer is critical for efficient transportation of NPs-loaded drug delivery system. To understand how the physical and surface properties of NPs affect their d...The rapid diffusion of nanoparticles （NPs） through mucus layer is critical for efficient transportation of NPs-loaded drug delivery system. To understand how the physical and surface properties of NPs affect their diffusion in mucus, we have developed a coarse-grained molecular dynamics model to study the diffusion of NPs in modeled mucus layer. Both steric obstruction and hydrodynamic interaction are included in the model capable of capturing the key characteristics of NPs＇ diffusion in mucus. The results show that both particle size and surface properties significantly affect the diffusivities of NPs in mucus. Furthermore, we find rodlike NPs can gain a higher diffusivity than spherical NPs with the same hydrodynamic diameter. In addition, the disturbed environment can enhance the diffusivity of NPs. Our findings can be utilized to design mucus penetrating NPs for targeted drug delivery system.展开更多
Simulations of adsorption process using the Reynolds mass flux model described in Part I of these serial articles are presented. The object of the simulation is the methylene chloride adsorption in a packed column(0.0...Simulations of adsorption process using the Reynolds mass flux model described in Part I of these serial articles are presented. The object of the simulation is the methylene chloride adsorption in a packed column(0.041 m id,packed with spherical activated carbon up to a length of 0.2 m). With the Reynolds mass flux model,breakthrough/regeneration curves, concentration and temperature as well as the velocity distributions can be obtained. The simulated results are compared with the experimental data reported in the literature and satisfactory agreement is found both in breakthrough/regeneration curves and temperature curves. Moreover,the anisotropic turbulent mass diffusion is characterized and discussed.展开更多
To avoid potential human casualties and environmental pollution,flowout gas from sulphuric gas wells showing high concentrations of volatile gas must be neutralized by controlled ignition.Simulation model is built by ...To avoid potential human casualties and environmental pollution,flowout gas from sulphuric gas wells showing high concentrations of volatile gas must be neutralized by controlled ignition.Simulation model is built by using CFD software for flowout gas,and ignition methods are analyzed.The simulation results indicate that the optimal ignition zone is located between 150mm and 570mm above the gas flowout device.Two ignition methods,electronical and chemical,are developed.12 and 6 experimental tests are performed respectively for these two methods.Results from the above tests verify that both approaches are successful in igniting the gas promptly and safely.In addition,our experience proves that the former way is more suitable for the fixed position ignition case,while the latter is more suitable for the long-distance or emergent ignition case.These two approaches can potentially be applied to a wide range of situations other than the fixed position ignition case and long distance ignition case.展开更多
In order to safely,efficiently and economically remove the blockages of natural gas hydrate(NGH)in the wellbores of ultra-high pressure gas wells,this paper utilized the heat released from an independently developed a...In order to safely,efficiently and economically remove the blockages of natural gas hydrate(NGH)in the wellbores of ultra-high pressure gas wells,this paper utilized the heat released from an independently developed autogenetic heat based solid blockage remover through chemical reaction in the wellbore to dissolve NGH and prevent it from forming again.In addition,adjustable heat generation time and heat generation amount was realized by regulating the dosage of the blockage remover.Finally,the chemically autogenetic heat based blockage removal technology was applied to remove the blockages in ultra-high pressure sour gas wells in the Sichuan Basin.And the following research results were obtained.First,when the independently developed chemically autogenetic heat based solid blockage remover is adopted,the peak temperature(34.2e88.5℃)and time(24.2e884.0 min)of heat generation can be adjusted by its dosage.What's more,there is NGH inhibitor in the reaction product,which can inhibit the regeneration of NGH.Second,as the concentration of the blockage remover increases,the heat transfer speed increases,leading to an increase of NGH dissociation rate around the blockage remover.Third,blockage removal time increases with the increase of wellbore ID.In addition,the increasing rate of the blockage removal time as the wellbore ID increases from 64 mm to 76 mm is lower than that from 76 mm to 102 mm.Fourth,the coincidence rate between the simulation calculation result of heat diffusion and the on-site actual consumption is more than 85%,which indicates that the proposed model for the heat diffusion of chemically autogenetic heat based blockage remover is reliable and can be used to calculate the dosage of blockage remover.Fifth,solid reagent adding device with resistance to sulfur and pressure of 140 MPa is used to add autogenetic heat based solid blockage remover.This blockage remover has been applied in the ultra-high pressure sour gas wells in the Sichuan Basin three well times.Thanks to its application,NGH blockages in these wells are removed successfully and their production is resumed smoothly.In conclusion,this blockage removal technology has such advantages as effective blockage removal,safe and simple on-site operation and low cost,and a promising application prospect.展开更多
A set of hydrostatic atmospheric thermodynamic equations and diffusion equation are solved numerically to simulate the flow,temperature and concentration fields over the Fenhe River Valley,Shanxi Province. The results...A set of hydrostatic atmospheric thermodynamic equations and diffusion equation are solved numerically to simulate the flow,temperature and concentration fields over the Fenhe River Valley,Shanxi Province. The results are compared with the data observed in a tracer experiment carried out in February of 1984. The concentration distributions are calculated by three approaches:ordinary grid numerical model,nested grid model and Gaussian model.The comparison shows that the nested grid model gives the best results and needs only a little more computer time.展开更多
基金the financial support of this work by Japan Ministry of Education, Culture, Sport, Science and Technology and Kyushu University’s Global COE program
文摘Tracer gas technique is a method to analyze the airflow path, measure the airflow quantity, and detect any recirculation or leakages in underground mine. In addition, it is also possible to evaluate the axial gas diffusion of gas in turbulent bulk flow by utilizing the tracer gas data. This paper discussed about the measurement using tracer gas technique in Cibaliung Underground Mine, Indonesia and the evaluation of effective axial diffusion coefficient, E, by numerical simulation. In addition, a scheme to treat network flow in mine ventilation system was also proposed. The effective axial diffusion coefficient for each airway was evaluated based on Taylor's theoretical equation. It is found that the evaluated diffusion coefficient agrees well with Taylor's equation by considering that the wall friction factor, f, is higher than those for smooth pipe flow. It also shows that the value of effective diffusion coefficient can be inherently determined and the value is constant when matching with other measurements. Furthermore, there are possibilities to utilize the tracer gas measurement data to evaluate the airway friction factors.
基金Project(BK2011258)supported by the Natural Science Foundation of Jiangsu Province,China
文摘Hydrogen diffusion coefficients of different regions in the welded joint of X80 pipeline steel were measured using the electro-chemical permeation technique. Using ABAQUS software, hydrogen diffusion in X80 pipeline steel welded joint was studied in consideration of the inhomogeneity of the welding zone, and temperature-dependent thermo-physical and mechanical properties of the metals. A three dimensional finite element model was developed and a coupled thermo-mechanical-diffusion analysis was performed. Hydrogen concentration distribution across the welded joint was obtained. It is found that the postweld residual hydrogen exhibits a non-uniform distribution across the welded joint. A maximum equivalent stress occurs in the immediate vicinity of the weld metal. The heat affected zone has the highest hydrogen concentration level, followed by the weld zone and the base metal.Simulation results are well consistent with theoretical analysis.
基金Funded by the National High-Tech R&D Program(863 Program)of China(No.2012AA040405)
文摘We numerically simulated and experimentally studied the interfacialcarbon diffusion between diamond tooland workpiece materials.A diffusion modelwith respect to carbon atoms of diamond toolpenetrating into chips and machined surface was established.The numericalsimulation results of the diffusion process revealthat the distribution laws of carbon atoms concentration have a close relationship with the diffusion distance,the diffusion time,and the originalcarbon concentration of the work material.In addition,diamond face cutting tests of die steels with different carbon content are conducted at different depth of cuts and feed rates to verify the previous simulation results.The micro-morphology of the chips is detected by scanning electron microscopy.Energy dispersive X-ray analysis was proposed to investigate the change in carbon content of the chips surface.The experimentalresults of this work are of benefit to a better understanding on the diffusion wear mechanism in single crystaldiamond cutting of ferrous metals.Moreover,the experimentalresults show that the diffusion wear of diamond could be reduced markedly by applying ultrasonic vibration to the cutting toolcompared with conventionalturning.
基金Supported by National Key R&D Program of China (2020YFB1710400)。
文摘Background Petrochemical products possess a high risk of flammability,explosivity,and toxicity,making petrochemical accidents exceedingly destructive.Therefore,disaster analysis,prediction,and real-time simulations have become important means of controlling and reducing accident hazards.Methods This study proposes a complete real-time simulation solution of gas diffusion with coordinate and concentration data,which was mainly aimed at simulating the types of harmful gas leakage and diffusion accidents in the petrochemical industry.The rendering effect was more continuous and accurate through grid homogenization and trilinear interpolation.This study presents a data processing and rendering parallelization process to enhance simulation efficiency.Gas concentration and fragment transparency were combined to synthesize transparent pixels in a scene.To ensure the approximate accuracy of the rendering effect,improve the efficiency of real-time rendering,and meet the requirement of intuitive perception using concentration data,a weighted blended order-independent transparency(OIT)with enhanced alpha weight is presented,which can provide a more intuitive perception of the hierarchical information of concentration data while preserving depth information.This study compares and analyzes three OIT algorithms-depth peeling,weighted blended OIT,and weighted blended OIT with enhanced alpha weight-in terms of rendering image quality,rendering time,required memory,and hierarchical information.Results Using weighted blended OIT with an enhanced alpha weight technique,the rendering time was shortened by 53.2%compared with that of the depth peeling algorithm,and the texture memory required was significantly smaller than that of the depth peeling algorithm.The rendering results of weighted blended OIT with an enhanced alpha weight were approximately accurate compared with those of the depth peeling algorithm as the ground truth,and there was no popping when surfaces passed through one another.Simultaneously,compared with weighted blended OIT,weighted blended OIT with an enhanced alpha weight achieved an intuitive perception of the hierarchical information of concentration data.
基金the financial support from the National Natural Science Foundation of China (No. 11422215, 11272327 and 11672079)supported by the Supercomputing Center of Chinese Academy of Sciences (SC CAS)
文摘The rapid diffusion of nanoparticles （NPs） through mucus layer is critical for efficient transportation of NPs-loaded drug delivery system. To understand how the physical and surface properties of NPs affect their diffusion in mucus, we have developed a coarse-grained molecular dynamics model to study the diffusion of NPs in modeled mucus layer. Both steric obstruction and hydrodynamic interaction are included in the model capable of capturing the key characteristics of NPs＇ diffusion in mucus. The results show that both particle size and surface properties significantly affect the diffusivities of NPs in mucus. Furthermore, we find rodlike NPs can gain a higher diffusivity than spherical NPs with the same hydrodynamic diameter. In addition, the disturbed environment can enhance the diffusivity of NPs. Our findings can be utilized to design mucus penetrating NPs for targeted drug delivery system.
基金Supported by the National Natural Science Foundation of China(21376163)
文摘Simulations of adsorption process using the Reynolds mass flux model described in Part I of these serial articles are presented. The object of the simulation is the methylene chloride adsorption in a packed column(0.041 m id,packed with spherical activated carbon up to a length of 0.2 m). With the Reynolds mass flux model,breakthrough/regeneration curves, concentration and temperature as well as the velocity distributions can be obtained. The simulated results are compared with the experimental data reported in the literature and satisfactory agreement is found both in breakthrough/regeneration curves and temperature curves. Moreover,the anisotropic turbulent mass diffusion is characterized and discussed.
文摘To avoid potential human casualties and environmental pollution,flowout gas from sulphuric gas wells showing high concentrations of volatile gas must be neutralized by controlled ignition.Simulation model is built by using CFD software for flowout gas,and ignition methods are analyzed.The simulation results indicate that the optimal ignition zone is located between 150mm and 570mm above the gas flowout device.Two ignition methods,electronical and chemical,are developed.12 and 6 experimental tests are performed respectively for these two methods.Results from the above tests verify that both approaches are successful in igniting the gas promptly and safely.In addition,our experience proves that the former way is more suitable for the fixed position ignition case,while the latter is more suitable for the long-distance or emergent ignition case.These two approaches can potentially be applied to a wide range of situations other than the fixed position ignition case and long distance ignition case.
基金Project supported by the Scientific Research and Technology Development Project of PetroChina Southwest Oil and Gas Field Company“Research on Hydrate plugging removal Technology for Ultra-high pressure Gas Wells”(No.20180303-03).
文摘In order to safely,efficiently and economically remove the blockages of natural gas hydrate(NGH)in the wellbores of ultra-high pressure gas wells,this paper utilized the heat released from an independently developed autogenetic heat based solid blockage remover through chemical reaction in the wellbore to dissolve NGH and prevent it from forming again.In addition,adjustable heat generation time and heat generation amount was realized by regulating the dosage of the blockage remover.Finally,the chemically autogenetic heat based blockage removal technology was applied to remove the blockages in ultra-high pressure sour gas wells in the Sichuan Basin.And the following research results were obtained.First,when the independently developed chemically autogenetic heat based solid blockage remover is adopted,the peak temperature(34.2e88.5℃)and time(24.2e884.0 min)of heat generation can be adjusted by its dosage.What's more,there is NGH inhibitor in the reaction product,which can inhibit the regeneration of NGH.Second,as the concentration of the blockage remover increases,the heat transfer speed increases,leading to an increase of NGH dissociation rate around the blockage remover.Third,blockage removal time increases with the increase of wellbore ID.In addition,the increasing rate of the blockage removal time as the wellbore ID increases from 64 mm to 76 mm is lower than that from 76 mm to 102 mm.Fourth,the coincidence rate between the simulation calculation result of heat diffusion and the on-site actual consumption is more than 85%,which indicates that the proposed model for the heat diffusion of chemically autogenetic heat based blockage remover is reliable and can be used to calculate the dosage of blockage remover.Fifth,solid reagent adding device with resistance to sulfur and pressure of 140 MPa is used to add autogenetic heat based solid blockage remover.This blockage remover has been applied in the ultra-high pressure sour gas wells in the Sichuan Basin three well times.Thanks to its application,NGH blockages in these wells are removed successfully and their production is resumed smoothly.In conclusion,this blockage removal technology has such advantages as effective blockage removal,safe and simple on-site operation and low cost,and a promising application prospect.
文摘A set of hydrostatic atmospheric thermodynamic equations and diffusion equation are solved numerically to simulate the flow,temperature and concentration fields over the Fenhe River Valley,Shanxi Province. The results are compared with the data observed in a tracer experiment carried out in February of 1984. The concentration distributions are calculated by three approaches:ordinary grid numerical model,nested grid model and Gaussian model.The comparison shows that the nested grid model gives the best results and needs only a little more computer time.
