In oil and gas well cementing processes,accurately predicting the bottom hole circulating temperature(BHCT)is critical to ensuring effective zonal isolation.Overestimating the temperature can lead to excessive retarda...In oil and gas well cementing processes,accurately predicting the bottom hole circulating temperature(BHCT)is critical to ensuring effective zonal isolation.Overestimating the temperature can lead to excessive retardation issues,while underestimation can cause cementing accidents.Current methods for calculating the BHCT of cement slurry typically simplify the cementing processes to a single-fluid circulation and ignore the impact of pre-cementing processes on temperature,leading to significant discrepancies between calculated and actual results.In this study,the wellbore and formation are simplified into a two-dimensional axisymmetric structure,and a mathematical model of the temperature field under multi-fluid and multi-step conditions is established based on the law of energy conservation.The finite volume method was used to discretize the model,and a transient temperature field solver for the entire cementing process was developed,which can numerically calculate the temperature of any fluid at any time,any location.For an actual well example,the temperature distribution of the wellbore and formation after casing running is taken as the initial condition.Numerical calculations were performed sequentially to calculate the temperature fields of circulation flushing,wellbore preparation,and cementing,as well as the BHCT of the cement slurry.The study reveals that during the circulation flushing stage,the maximum temperature point in the wellbore is located at a distance of about 366 m above the bottom of the well.In the wellbore preparation stage,due to static heat exchange,the maximum temperature point gradually shifts to the bottom of the well.The BHCT of cement slurry changes continuously under cementing processes with multi-fluid and multi-step,making it a transient value.The BHCT of the lead slurry and tail slurry are not equal,with the maximum BHCT of the tail slurry being 2.46°C higher than that of the lead slurry.If circulation flushing and wellbore preparation are not considered,the calculated BHCT of the cement slurry will have errors of+6.8%and-1.9%.The study highlighted that considering thermal effects of all cementing stages,such as circulation flushing and wellbore preparation,in BHCT calculations can help improve prediction accuracy.展开更多
A multi-fluid blast furnace model was simply introduced and was used to simulate several innovative ironmaking operations. The simulation results show that injecting hydrogen bearing materials, especially injecting na...A multi-fluid blast furnace model was simply introduced and was used to simulate several innovative ironmaking operations. The simulation results show that injecting hydrogen bearing materials, especially injecting natural gas and plastics, the hydrogen reduction is enhanced, and the furnace performance is improved simultaneously. Total heat input shows obvious decrease due to the decrease of heat consumption in direct reduction, solution loss and silicon transfer reactions. If carbon composite agglomerates are charged into the furnace, the temperature of thermal reserve zone will obviously decrease, and the reduction of iron-bearing burden materials will be retarded. However, the efficiency of blast furnace is improved just due to the decrease in heat requirements for solution loss, sinter reduction, and silicon transfer reactions, and less heat loss through top gas and furnace wall. Finally, the model is used to investigate the performance of blast furnace under the condition of top gas recycling together with plastics injection, cold oxygen blasting and carbon composite agglomerate charging. The lower furnace temperature, extremely accelerated reduction rate, drastically decreased CO2 emission and remarkably enhanced heat efficiency were obtained by using the innovative operations, and the blast furnace operation with superhigh efficiency can be realized.展开更多
The Euler-Euler model is less effective in capturing the free surface of flow film in the spiral separator,and thus a Eulerian multi-fluid volume of fluid(VOF)model was first proposed to describe the particulate flow ...The Euler-Euler model is less effective in capturing the free surface of flow film in the spiral separator,and thus a Eulerian multi-fluid volume of fluid(VOF)model was first proposed to describe the particulate flow in spiral separators.In order to improve the applicability of the model in the high solid concentration system,the Bagnold effect was incorporated into the modelling framework.The capability of the proposed model in terms of predicting the flow film shape in a LD9 spiral separator was evaluated via comparison with measured flow film thicknesses reported in literature.Results showed that sharp air–water and air-pulp interfaces can be obtained using the proposed model,and the shapes of the predicted flow films before and after particle addition were reasonably consistent with the observations reported in literature.Furthermore,the experimental and numerical simulation of the separation of quartz and hematite were performed in a laboratory-scale spiral separator.When the Bagnold lift force model was considered,predictions of the grade of iron and solid concentration by mass for different trough lengths were more consistent with experimental data.In the initial development stage,the quartz particles at the bottom of the flow layer were more possible to be lifted due to the Bagnold force.Thus,a better predicted vertical stratification between quartz and hematite particles was obtained,which provided favorable conditions for subsequent radial segregation.展开更多
Recently,electrospinning(ESP)has been widely used as a synthetic technology to prepare nanofibers with unique properties from various raw materials.The applications of functionalized nanofibers have gradually develope...Recently,electrospinning(ESP)has been widely used as a synthetic technology to prepare nanofibers with unique properties from various raw materials.The applications of functionalized nanofibers have gradually developed into one of the most exciting topics in the field of materials science.In this review,we focus on the preparation of multi-structure fibrous nanomaterials by means of multi-fluidic ESP and review the applications of multi-structure nanofibers in energy,catalysis,and biology.First,the working principle and process of ESP are introduced;then,we demonstrate how the microfluidic concept is com-bined with the ESP technique to the multi-fluidic ESP technique.Subsequently,the applications of multi-structure nanofibers in energy(Li^(+)/Na^(+)batteries and Li–S batteries),hetero-catalysis,and biology(drug delivery and tissue engineering)are introduced.Finally,challenges and future directions in this emerging field are summarized.展开更多
Based on the classical Roe method, we develop an interface capture method according to the general equation of state, and extend the single-fluid Roe method to the two-dimensional （2D） multi-fluid flows, as well as ...Based on the classical Roe method, we develop an interface capture method according to the general equation of state, and extend the single-fluid Roe method to the two-dimensional （2D） multi-fluid flows, as well as construct the continuous Roe matrix for the whole flow field. The interface capture equations and fluid dynamic conservative equations are coupled together and solved by using any high-resolution schemes that usually suit for the single-fluid flows. Some numerical examples are given to illustrate the solution of 1D and 2D multi-fluid Riemann problems.展开更多
Two interface capturing methods are studied for multi fluid flows, governed by the stiffened gas equation of state. The mixture type interface capturing algorithm uses a simple volume fraction model Euler equations wr...Two interface capturing methods are studied for multi fluid flows, governed by the stiffened gas equation of state. The mixture type interface capturing algorithm uses a simple volume fraction model Euler equations written in a quasi conservative form, which is solved by a standard high resolution piecewise parabolic method (PPM) with multi fluid Riemann solver. The level set interface capturing method uses a narrow band ghost fluid method (GFM) with no numerical smearing. Several examples are presented and compared for one and two dimensions, which show the feasibility of the two methods applied to various multi fluid problems.展开更多
Quantitative representation of complicated behavior of fluid mixtures in the critical region by any of equation-of-state theories re-mains as a difficult thermodynamic topics to date. In the present work, a computatio...Quantitative representation of complicated behavior of fluid mixtures in the critical region by any of equation-of-state theories re-mains as a difficult thermodynamic topics to date. In the present work, a computational efforts were made for representing various types of critical loci of binary water with hydrocarbon systems showing Type II and Type III phase behavior by an elementary equation of state [called multi-fluid nonrandom lattice fluid EOS (MF-NLF EOS)] based on the lattice statistical mechanical theory. The model EOS requires two mo-lecular parameters which representing molecular size and interaction energy for a pure component and single adjustable interaction energy pa-rameter for binary mixtures. Critical temperature and pressure data were used to obtain molecular size parameter and vapor pressure data were used to obtain interaction energy parameter. The MF-NLF EOS model adapted in the present study correlated quantitatively well the critical loci of various binary water with hydrocarbon systems.展开更多
煤矿井下作业环境复杂多变,钻探成为煤矿开采的必备环节。钻杆加卸是钻探过程中的重要步骤,传统的人工钻杆加卸方式不仅耗时费力,而且劳动强度极大,对工人的身体健康构成严重威胁。为了提高煤矿井下钻机的钻杆加卸效率,降低劳动强度,提...煤矿井下作业环境复杂多变,钻探成为煤矿开采的必备环节。钻杆加卸是钻探过程中的重要步骤,传统的人工钻杆加卸方式不仅耗时费力,而且劳动强度极大,对工人的身体健康构成严重威胁。为了提高煤矿井下钻机的钻杆加卸效率,降低劳动强度,提升作业安全性,探讨并总结当前煤矿井下智能化钻机配套钻杆自动加卸技术,发现多轴液驱机械手式换杆技术具有高度的灵活性和适应性,可作为解决多规格钻具自动加卸问题的有效方案。基于当前机械手关键技术的研究,分析得出动态路径规划方法是多轴机械手式钻杆加卸系统研究的难点,在总结当前机械手动态轨迹规划领域研究进展的基础上,分析现有路径规划方法的优缺点,特别是在动态环境下的适应性表现。在此基础上,研究了基于快速随机搜索树(Rapidly-exploring Random Tree,RRT)算法的混合轨迹规划策略在复杂环境下的应用,展示了这些方法在提升机械手路径规划精度、减少操作时间以及增强系统鲁棒性方面展现出的显著优势。针对未来研究方向,提出了进一步提升机械手动态轨迹规划算法性能,增强机械手自主作业能力,推动煤矿井下自动化技术全面应用的建议。展开更多
In this paper,a remapping-free adaptive GRP method for one dimensional(1-D)compressible flows is developed.Based on the framework of finite volume method,the 1-D Euler equations are discretized on moving volumes and t...In this paper,a remapping-free adaptive GRP method for one dimensional(1-D)compressible flows is developed.Based on the framework of finite volume method,the 1-D Euler equations are discretized on moving volumes and the resulting numerical fluxes are computed directly by the GRP method.Thus the remapping process in the earlier adaptive GRP algorithm[17,18]is omitted.By adopting a flexible moving mesh strategy,this method could be applied for multi-fluid problems.The interface of two fluids will be kept at the node of computational grids and the GRP solver is extended at the material interfaces of multi-fluid flows accordingly.Some typical numerical tests show competitive performances of the new method,especially for contact discontinuities of one fluid cases and the material interface tracking of multi-fluid cases.展开更多
基金supported by the National Natural Science Foundation of China(No.U22B6003 and No.52274010)the China Scholarship Council(No.202008080235)。
文摘In oil and gas well cementing processes,accurately predicting the bottom hole circulating temperature(BHCT)is critical to ensuring effective zonal isolation.Overestimating the temperature can lead to excessive retardation issues,while underestimation can cause cementing accidents.Current methods for calculating the BHCT of cement slurry typically simplify the cementing processes to a single-fluid circulation and ignore the impact of pre-cementing processes on temperature,leading to significant discrepancies between calculated and actual results.In this study,the wellbore and formation are simplified into a two-dimensional axisymmetric structure,and a mathematical model of the temperature field under multi-fluid and multi-step conditions is established based on the law of energy conservation.The finite volume method was used to discretize the model,and a transient temperature field solver for the entire cementing process was developed,which can numerically calculate the temperature of any fluid at any time,any location.For an actual well example,the temperature distribution of the wellbore and formation after casing running is taken as the initial condition.Numerical calculations were performed sequentially to calculate the temperature fields of circulation flushing,wellbore preparation,and cementing,as well as the BHCT of the cement slurry.The study reveals that during the circulation flushing stage,the maximum temperature point in the wellbore is located at a distance of about 366 m above the bottom of the well.In the wellbore preparation stage,due to static heat exchange,the maximum temperature point gradually shifts to the bottom of the well.The BHCT of cement slurry changes continuously under cementing processes with multi-fluid and multi-step,making it a transient value.The BHCT of the lead slurry and tail slurry are not equal,with the maximum BHCT of the tail slurry being 2.46°C higher than that of the lead slurry.If circulation flushing and wellbore preparation are not considered,the calculated BHCT of the cement slurry will have errors of+6.8%and-1.9%.The study highlighted that considering thermal effects of all cementing stages,such as circulation flushing and wellbore preparation,in BHCT calculations can help improve prediction accuracy.
文摘A multi-fluid blast furnace model was simply introduced and was used to simulate several innovative ironmaking operations. The simulation results show that injecting hydrogen bearing materials, especially injecting natural gas and plastics, the hydrogen reduction is enhanced, and the furnace performance is improved simultaneously. Total heat input shows obvious decrease due to the decrease of heat consumption in direct reduction, solution loss and silicon transfer reactions. If carbon composite agglomerates are charged into the furnace, the temperature of thermal reserve zone will obviously decrease, and the reduction of iron-bearing burden materials will be retarded. However, the efficiency of blast furnace is improved just due to the decrease in heat requirements for solution loss, sinter reduction, and silicon transfer reactions, and less heat loss through top gas and furnace wall. Finally, the model is used to investigate the performance of blast furnace under the condition of top gas recycling together with plastics injection, cold oxygen blasting and carbon composite agglomerate charging. The lower furnace temperature, extremely accelerated reduction rate, drastically decreased CO2 emission and remarkably enhanced heat efficiency were obtained by using the innovative operations, and the blast furnace operation with superhigh efficiency can be realized.
基金the National Natural Science Foundation of China(Nos.51974065 and 52274257)the Open Foundation of State Key Laboratory of Mineral Processing(No.BGRIMMKJSKL-2020-13)the Fundamental Research Funds for the Central Universities(Nos.N2201008 and N2201004).
文摘The Euler-Euler model is less effective in capturing the free surface of flow film in the spiral separator,and thus a Eulerian multi-fluid volume of fluid(VOF)model was first proposed to describe the particulate flow in spiral separators.In order to improve the applicability of the model in the high solid concentration system,the Bagnold effect was incorporated into the modelling framework.The capability of the proposed model in terms of predicting the flow film shape in a LD9 spiral separator was evaluated via comparison with measured flow film thicknesses reported in literature.Results showed that sharp air–water and air-pulp interfaces can be obtained using the proposed model,and the shapes of the predicted flow films before and after particle addition were reasonably consistent with the observations reported in literature.Furthermore,the experimental and numerical simulation of the separation of quartz and hematite were performed in a laboratory-scale spiral separator.When the Bagnold lift force model was considered,predictions of the grade of iron and solid concentration by mass for different trough lengths were more consistent with experimental data.In the initial development stage,the quartz particles at the bottom of the flow layer were more possible to be lifted due to the Bagnold force.Thus,a better predicted vertical stratification between quartz and hematite particles was obtained,which provided favorable conditions for subsequent radial segregation.
基金the National Natural Science Foundation of China (22175007, 21975007, 21774005, and21433012)the National Natural Science Foundation for Outstanding Youth Foundation+4 种基金the Fundamental Research Funds for the Central Universitiesthe National Program for Support of Top-Notch Young Professionalsthe 111 project (B14009)the National Postdoctoral Program for Innovative Talents (BX20190027)the China Postdoctoral Science Foundation Funded Project (2019M650431)
文摘Recently,electrospinning(ESP)has been widely used as a synthetic technology to prepare nanofibers with unique properties from various raw materials.The applications of functionalized nanofibers have gradually developed into one of the most exciting topics in the field of materials science.In this review,we focus on the preparation of multi-structure fibrous nanomaterials by means of multi-fluidic ESP and review the applications of multi-structure nanofibers in energy,catalysis,and biology.First,the working principle and process of ESP are introduced;then,we demonstrate how the microfluidic concept is com-bined with the ESP technique to the multi-fluidic ESP technique.Subsequently,the applications of multi-structure nanofibers in energy(Li^(+)/Na^(+)batteries and Li–S batteries),hetero-catalysis,and biology(drug delivery and tissue engineering)are introduced.Finally,challenges and future directions in this emerging field are summarized.
文摘Based on the classical Roe method, we develop an interface capture method according to the general equation of state, and extend the single-fluid Roe method to the two-dimensional （2D） multi-fluid flows, as well as construct the continuous Roe matrix for the whole flow field. The interface capture equations and fluid dynamic conservative equations are coupled together and solved by using any high-resolution schemes that usually suit for the single-fluid flows. Some numerical examples are given to illustrate the solution of 1D and 2D multi-fluid Riemann problems.
文摘Two interface capturing methods are studied for multi fluid flows, governed by the stiffened gas equation of state. The mixture type interface capturing algorithm uses a simple volume fraction model Euler equations written in a quasi conservative form, which is solved by a standard high resolution piecewise parabolic method (PPM) with multi fluid Riemann solver. The level set interface capturing method uses a narrow band ghost fluid method (GFM) with no numerical smearing. Several examples are presented and compared for one and two dimensions, which show the feasibility of the two methods applied to various multi fluid problems.
文摘Quantitative representation of complicated behavior of fluid mixtures in the critical region by any of equation-of-state theories re-mains as a difficult thermodynamic topics to date. In the present work, a computational efforts were made for representing various types of critical loci of binary water with hydrocarbon systems showing Type II and Type III phase behavior by an elementary equation of state [called multi-fluid nonrandom lattice fluid EOS (MF-NLF EOS)] based on the lattice statistical mechanical theory. The model EOS requires two mo-lecular parameters which representing molecular size and interaction energy for a pure component and single adjustable interaction energy pa-rameter for binary mixtures. Critical temperature and pressure data were used to obtain molecular size parameter and vapor pressure data were used to obtain interaction energy parameter. The MF-NLF EOS model adapted in the present study correlated quantitatively well the critical loci of various binary water with hydrocarbon systems.
文摘煤矿井下作业环境复杂多变,钻探成为煤矿开采的必备环节。钻杆加卸是钻探过程中的重要步骤,传统的人工钻杆加卸方式不仅耗时费力,而且劳动强度极大,对工人的身体健康构成严重威胁。为了提高煤矿井下钻机的钻杆加卸效率,降低劳动强度,提升作业安全性,探讨并总结当前煤矿井下智能化钻机配套钻杆自动加卸技术,发现多轴液驱机械手式换杆技术具有高度的灵活性和适应性,可作为解决多规格钻具自动加卸问题的有效方案。基于当前机械手关键技术的研究,分析得出动态路径规划方法是多轴机械手式钻杆加卸系统研究的难点,在总结当前机械手动态轨迹规划领域研究进展的基础上,分析现有路径规划方法的优缺点,特别是在动态环境下的适应性表现。在此基础上,研究了基于快速随机搜索树(Rapidly-exploring Random Tree,RRT)算法的混合轨迹规划策略在复杂环境下的应用,展示了这些方法在提升机械手路径规划精度、减少操作时间以及增强系统鲁棒性方面展现出的显著优势。针对未来研究方向,提出了进一步提升机械手动态轨迹规划算法性能,增强机械手自主作业能力,推动煤矿井下自动化技术全面应用的建议。
基金supported by NSFC(91130021)Jin Qi is supported by NSFC(1171037,11201033)+3 种基金CAEP under project 2012A0202010Jiequan Li is supported by NSFC(91130021,11371063,11031001)the Doctoral program from Educational Ministry(20130003110004)an open project from Institute of Applied Physics and Computational Mathematics,Beijing。
文摘In this paper,a remapping-free adaptive GRP method for one dimensional(1-D)compressible flows is developed.Based on the framework of finite volume method,the 1-D Euler equations are discretized on moving volumes and the resulting numerical fluxes are computed directly by the GRP method.Thus the remapping process in the earlier adaptive GRP algorithm[17,18]is omitted.By adopting a flexible moving mesh strategy,this method could be applied for multi-fluid problems.The interface of two fluids will be kept at the node of computational grids and the GRP solver is extended at the material interfaces of multi-fluid flows accordingly.Some typical numerical tests show competitive performances of the new method,especially for contact discontinuities of one fluid cases and the material interface tracking of multi-fluid cases.
