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numerical simulation of the dynamic migration mechanism and prediction of saturation of tight sandstone oil

Science China Earth Sciences 2024年第1期67卷 179-195页

作者： Gaohui CAO Mian LIN Likuan ZHANG Lili JI Wenbin JIANG Institute of Mechanics Chinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China Institute of Geology and Geophysics Chinese Academy of SciencesBeijing 100029China

Quantitative characterization of tight sandstone oil migration and accumulation is an emerging research frontier in the field of oil and gas exploration.In this study,a conceptual model containing multiple basic geological elements is developed,and a nonlinear seepage numerical model for tight sandstone oil migration and accumulation is established.The effects of the slip effect,overpressure driving force,buoyancy,and capillary force on the migration and accumulation of tight oil are examined.The results showed that(1)the differences in oil migration and accumulation between tight and conventional reservoirs are reflected in the growth mode of oil saturation,distribution characteristics of oil and water,and extent of the effect of the formation dip angle;(2)the slip effect has a significant impact when the average pore throat radius is less than 150 nm and the overpressure driving force and capillary force are the main mechanical mechanisms controlling oil migration and accumulation in tight sandstone,while the coupling effect of buoyancy,capillary force,and overpressure driving force controls the upper and lower limits of oil saturation.Finally,a dimensional and dimensionless identification chart for rapidly predicting the oil saturation of tight sandstone is proposed and verified using the measured data.This study provides a basis for analyzing the migration and accumulation mechanisms of tight sandstone oil and a new approach for predicting oil saturation.Additionally,we developed digital and visual analysis methods for the migration results,enriching the expression of the dynamics of hydrocarbon accumulation.

关键词： Tight sandstone Migration and accumulation Dynamics Oil saturation numerical simulation

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numerical simulation of transient characteristics in a bulb turbine during the load rejection process

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Journal of Hydrodynamics 2024年第1期36卷 170-183页

作者： Yue Lu Yu-quan Zhang Zhong-wei He Yuan Zheng College of Water Conservancy and Hydropower Engineering Hohai UniversityNanjing210098China College of Energy and Electrical Engineering Hohai UniversityNanjing210098China Huadong Engineering Corporation Ltd. Hangzhou311122China

To evaluate the safety of the bulb tubular turbine,the dynamic hydraulic characteristics of a hydropower station system during the load rejection process are studied through numerical simulations and a prototype test.In the developed model,a dynamic grid technology(DGT)controls the closure of the guide vane and the blade,whilst the moment balance equation and the user-defined function(UDF)provide the runner’s rotation speed.The 3-D transient simulation method can well predict the rotation speed and mass flow curves in the state of load rejection.The simulation outcomes of the system performance are basically consistent with the measurement data of the prototype.As observed,the runner is subjected to the reversely increased torque and axial force,the system is in a braking phase,and the maximum speed peaks at 144.6%of the rated speed.Moreover,the internal flow of the runner is greatly affected by the closure of the guide vane,and the draft tube forms an eccentric spiral vortex rope.It breaks downstream,aggravating the instability of the draft tube.Overall,the transient characteristics span for the first five seconds,demonstrating the importance of establishing an efficient governing controller.The obtained results are useful for designing the turbine’s flow channel with a double regulating function and comprehending the turbine’s transient characteristics.

关键词： Bulb tubular turbine load rejection numerical simulation dynamic grid prototype test

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numerical simulation of tritium behavior under a postulated accident condition for CFETR TEP system

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Nuclear Science and Techniques 2023年第7期34卷 206-218页

作者： Hai-Xia Wang Xue-Wei Fu Wei-Ping Liu Tao-Sheng Li Jie Yu Institute of Nuclear Energy Safety Technology Hefei Institutes of Physical ScienceChinese Academy of SciencesHefei 230031China

China Fusion Engineering Test Reactor(CFETR)is China's self-designed and ongoing next-generation fusion reactor project.Tritium confinement systems in CFETR guarantee that the radiation level remains below the safety limit during tritium handling and operation in the fuel cycle system.Our tritium technology team is responsible for studying tritium transport behavior in the CFETR tritium safety confinement systems of the National Key R&D Program of China launched in 2017,and we are conducting CFETR tritium plant safety analysis by using CFD software.In this paper,the tritium migration and removal behavior were studied under a postulated accident condition for the Tokamak Exhaust Processing system of CFETR.The quantitative results of the transport behavior of tritium in the process room and glove box during the whole accident sequence(e.g.,tritium release,alarm,isolation,and tritium removal)have been presented.The results support the detailed design and engineering demonstration-related research of CFETR tritium plant.

关键词： China Fusion Engineering Test Reactor(CFETR) Tokamak Exhaust Processing(TEP)system numerical simulation Tritium transport behavior Tritium confinement system Accident condition

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numerical simulation on the multiphase flow and reoxidation of the molten steel in a two-strand tundish during ladle change

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International Journal of Minerals,Metallurgy and Materials 2024年第7期31卷 1540-1553页

作者： Jingcheng Wang Zhentong Liu Wei Chen Hongliang Chen Lifeng Zhang School of Mechanical Engineering Yanshan UniversityQinhuangdao 066004China School of Materials Science and Engineering Tianjin UniversityTianjin 300350China School of Mechanical and Materials Engineering North China University of TechnologyBeijing 100144China

A 3D mathematical model was proposed to investigate the molten steel–slag–air multiphase flow in a two-strand slab continuous casting(CC)tundish during ladle change.The study focused on the exposure of the molten steel and the subsequent reoxidation occurrence.The exposure of the molten steel was calculated using the coupled realizable k–εmodel and volume of fluid(VOF)model.The diffusion of dissolved oxygen was determined by solving the user-defined scalar(UDS)equation.Moreover,the user-defined function(UDF)was used to describe the source term in the UDS equation and determine the oxidation rate and oxidation position.The effect of the refilling speed on the molten steel exposure and dissolved oxygen content was also discussed.Increasing the refilling speed during ladle change reduced the refilling time and the exposure duration of the molten steel.However,the elevated refilling speed enlarged the slag eyes and increased the average dissolved oxygen content within the tundish,thereby exacerbating the reoxidation phenomenon.In addition,the time required for the molten steel with a high dissolved oxygen content to exit the tundish varied with the refilling speed.When the inlet speed was 3.0 m·s^(-1)during ladle change,the molten steel with a high dissolved oxygen content exited the outlet in a short period,reaching a maximum dissolved oxygen content of 0.000525wt%.Conversely,when the inlet speed was 1.8 m·s^(-1),the maximum dissolved oxygen content was 0.000382wt%.The refilling speed during the ladle change process must be appropriately decreased to minimize reoxidation effects and enhance the steel product quality.

关键词： tundish ladle change reoxidation multiphase flow numerical simulation

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numerical simulation of rime ice accretion on a threedimensional wind turbine blade using a Lagrangian approach

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Frontiers of Structural and Civil Engineering 2023年第12期17卷 1895-1906页

作者： Tiange ZHANG Xuanyi ZHOU Zhenbiao LIU State Key Laboratory of Disaster Reduction in Civil Engineering Tongji UniversityShanghai 200092China State Key Laboratory of Photovoltaic Science and Technology Trina SolarChangzhou 213031China

The accreted ice on wind turbine blades significantly deteriorates the blade aerodynamic performance and consequently the power production.The existing numerical simulations of blade icing have mostly been performed with the Eulerian approach for two-dimensional(2D)blade profiles,neglecting the possible three-dimensional(3D)rotating effect.This paper conducts a numerical simulation of rime ice accretion on a 3D wind turbine blade using the Lagrangian approach.The simulation results are validated through previously published experimental data.The icing characteristics along the blade radial direction are then investigated in detail.Significant radial airflow along the blade is observed,which demonstrates the necessity of 3D simulation.In addition,more droplets are found to impinge on the blade surface near the tip region,thereby producing severer ice accretion there.The accreted ice increases almost linearly along the blade radial direction in terms of both ice mass and maximum ice thickness.

关键词： ice accretion wind turbine numerical simulation Lagrangian approach

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numerical simulation study on multiphase flow pattern of hydrate slurry

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Petroleum Science 2023年第6期20卷 3897-3917页

作者： Xiao-Fang Lv Feng Chen Jie Zhang Yang Liu Qian-Li Ma Hui Du Chuan-Shuo Wang Shi-Dong Zhou Bo-Hui Shi Shang-Fei Song Jing Gong Jiangsu Key Laboratory of Oil and Gas Storage&Transportation Technology Changzhou UniversityChangzhou213016JiangsuChina China Petroleum&Chemical Corporation Northwest Oilfield Branch Petroleum Engineering Technology Research InstituteUrumqi830011XinjiangChina Sinopec Shengli Oilﬁeld Company Dongying257001ShandongChina National Engineering Laboratory for Pipeline Safety/MOE Key Laboratory of Petroleum Engineering China University of Petroleum-Beijing102249BeijingChina

The research on the multiphase flow characteristics of hydrate slurry is the key to implementing the risk prevention and control technology of hydrate slurry in deep-water oil and gas mixed transportation system.This paper established a geometric model based on the high-pressure hydrate slurry experimental loop.The model was used to carry out simulation research on the flow characteristics of gas-liquid-solid three-phase flow.The specific research is as follows:Firstly,the effects of factors such as slurry flow velocity,hydrate particle density,hydrate particle size,and hydrate volume fraction on the stratified smooth flow were specifically studied.Orthogonal test obtained particle size has the most influence on the particle concentration distribution.The slurry flow velocity is gradually increased based on stratified smooth flow.Various flow patterns were observed and their characteristics were analyzed.Secondly,increasing the slurry velocity to 2 m/s could achieve the slurry flow pattern of partial hydrate in the pipeline transition from stratified smooth flow to wavy flow.When the flow rate increases to 3 m/s,a violent wave forms throughout the entire loop.Based on wave flow,as the velocity increased to 4 m/s,and the flow pattern changed to slug flow.When the particle concentration was below 10%,the increase of the concentration would aggravate the slug flow trend;if the particle concentration was above 10%,the increase of the concentration would weaken the slug flow trend,the increase of particle density and liquid viscosity would weaken the tendency of slug flow.The relationship between the pressure drop gradients of several different flow patterns is:slug flow>wave flow>stratified smooth flow.

关键词： Hydrate slurry numerical simulation Multiphase flow Flow field distribution Flow pattern transition

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numerical simulation of Nanofluid-Based Parallel Cooling Photovoltaic Thermal Collectors

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Journal of Thermal Science 2023年第4期32卷 1644-1656页

作者： WANG Jiangjiang QIN Yanbo HUO Shuojie XIE Kangzhen LI Yiming Hebei Key Laboratory of Low Carbon and High Efficiency Power Generation Technology North China Electric Power UniversityBaoding071003China

A novel hybrid cogeneration system based on a parallel-cooled photovoltaic/thermal(PV/T)module is presented in this paper.The temperature of the parallel-cooled PV/T module is more uniform due to the parallel cooling fluid of air mixed with water or nanofluids(SiO2,CuO,Ag,and Al_(2)O_(3)).The results show that the overall temperature of the PV cell in the parallel-cooled module is about 2 K lower than that in the single-cooled module,with a 9.01%improvement in thermal efficiency and a 0.09%enhancement in electrical efficiency.The PV/T module with nanofluid shows a significant improvement in thermal and electrical efficiency.The thermal and electrical efficiencies of the parallel-cooled PV/T module consisting of Al_(2)O_(3)nanofluid and air are 89.21%and 9.84%,respectively.Compared with the non-nanofluid parallel cooling scheme,the cooling method consisting of 1 wt%,3 wt%,or 5 wt%Al_(2)O_(3)and air,the thermal efficiency of PV/T was improved by 5.47%,5.30%,and 3.93%,respectively with the solar radiation of 800 W/m^(2)and the flow rate of 0.10 m/s,while the electrical efficiency was improved by 0.026%,0.027%,and 0.034%,respectively.In addition,when the solar radiation is 1000 W/m^(2)with a flow rate of 0.025 m/s,the air-water parallel cooling PV/T module achieves a maximum exergy efficiency of 11.74%.

关键词： PV/T parallel cooling exergy efficiency nanofluid numerical simulation

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numerical simulation of flow and heat transfer of n-decane in sub-millimeter spiral tube at supercritical pressure

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中国化学工程学报:英文版 2023年第8期60卷 173-185页

作者： Jiahao Xing Huaizhi Han Ruitian Yu Wen Luo School of Chemical Engineering Sichuan UniversityChengdu 610065China Engineering Research Center of Combustion and Cooling for Aerospace Power Ministry of EducationSichuan UniversityChengdu 610065China

The flow and heat transfer characteristics of n-decane in the sub-millimeter spiral tube(SMST) at supercritical pressure(p = 3 MPa) are studied by the RNG k-ε numerical model in this paper. The effects of various Reynolds numbers(Re) and structural parameters pitch(s) and spiral diameter(D) are analyzed.Results indicate that the average Nusselt numberNu and friction factorNu increase with an increase in Re, and decrease with an increase in D/d(tube diameter). In terms of the structural parameter s/d, it is found that as s/d increases, the Nu first increase, and then decrease. and the critical structural parameter is s/d = 4. Compared with the straight tube, the SMST can improve Nu by 34.8% at best, while it can improve Nu by 102.1% at most. In addition, a comprehensive heat transfer coefficient is applied to analyze the thermodynamic properties of SMST. With the optimal structural parameters of D/d = 6 and s/d = 4, the comprehensive heat transfer factor of supercritical pressure hydrocarbon fuel in the SMST can reach 1.074. At last, correlations of the average Nusselt number and friction factor are developed to predict the flow and heat transfer of n-decane at supercritical pressure.

关键词： Sub-millimeter spiral tube Supercritical pressure numerical simulation Heat transfer performance

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numerical simulation for the comparison of thermal and plastic material flow behavior between symmetrical and asymmetrical boundary conditions during friction stir welding

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Advances in Manufacturing 2023年第1期11卷 143-157页

作者： Hao Su Chuan-Song Wu MOE Key Lab for Liquid-Solid Structure Evolution and Materials Processing Institute of Materials JoiningShandong UniversityJinan250061People’s Republic of China

An accurate description of the contact condition between the tool and the workpiece material is one of the most important issues for expounding the underlying multi-physics coupled mechanism during friction stir welding(FSW)process.In the present study,a novel asymmetrical boundary condition around the tool-workpiece contact interface is proposed for the FSW of AA2024-T4 alloy.A three-dimensional computational fluid dynamics model is employed for the comparison of the coupled thermal and plastic material flow behavior between asymmetrical and symmetrical boundary conditions.numerical results of heat generation,temperature distribution,tunnel defect formation and material flow streamline during the welding process are quantitatively analyzed.Besides,various experimental measuring methods are utilized to obtain information about temperature,thermal cycle,tool torque and horizontal cross-section around the exiting keyhole.It is revealed that the modeling results of heat flux density and temperature distribution around the pin,as well as material flow characteristics all change significantly for the two models with different boundary conditions.Particularly,the asymmetrical boundary condition is more capable of predicting temperature fluctuation,plastic material flow along the vertical direction,as well as tunnel defect formation during FSW.Therefore,the superiority of the model with asymmetrical boundary condition over the symmetrical one during the numerical simulation of FSW is elucidated.

关键词： Friction stir welding(FSW) numerical simulation Heat generation Plastic material flow Asymmetrical boundary condition

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numerical simulation study on shear resistance of anchorage joints considering tensile-shear fracture criterion of 2G-NPR bolt

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International Journal of Coal Science & Technology 2023年第4期10卷 186-202页

作者： Shulin Ren Zhigang Tao Manchao He Mengnan Li Qiru Sui State Key Laboratory for Geomechanics and Deep Underground Engineering Beijing 100083China School of Mechanics and Civil Engineering China University of Mining and TechnologyBeijing 100083China

2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has signifcant efects on improving the shear strength of jointed rock mass and controlling the stability of surrounding rock. To achieve an accurate simulation of bolted joint shear tests, we have studied a numerical simulation method that takes into account the 2G-NPR bolt's tensile–shear fracture criterion. Firstly, the indoor experimental study on the tensile–shear mechanical properties of 2G-NPR bolt is carried out to explore its mechanical properties under diferent tensile–shear angles, and the fracture criterion of 2G-NPR bolt considering the tensile–shear angle is established. Then, a three-dimensional numerical simulation method considering the tensile–shear mechanical constitutive and fracture criterion of 2G-NPR bolt, the elastoplastic mechanical behavior of surrounding rock and the damage and deterioration of grouting body is proposed. The feasibility and accuracy of the method are verifed by comparing with the indoor shear test results of 2G-NPR bolt anchorage joints. Finally, based on the numerical simulation results, the deformation and stress of the bolt, the distribution of the plastic zone of the rock mass, the stress distribution and the damage of the grouting body are analyzed in detail. The research results can provide a good reference value for the practical engineering application and shear mechanical performance analysis of 2G-NPR bolt.

关键词： Anchorage joints 2G-NPR bolt Tensile-shear fracture criterion Shear behavior numerical simulation

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