The existing torque roll axis(TRA) decoupling theories for a powertrain mounting system assume that the stiffness and viscous damping properties are constant. However, real-life mounts exhibit considerable spectrally ...The existing torque roll axis(TRA) decoupling theories for a powertrain mounting system assume that the stiffness and viscous damping properties are constant. However, real-life mounts exhibit considerable spectrally varying stiffness and damping characteristics, and the influence of the spectrally-varying properties of the hydraulic mounts on the powertrain system cannot be ignored. To overcome the deficiency, an analytical quasi-linear model of the hydraulic mount and the coupled properties of the powertrain and hydraulic mounts system are formulated. The influence of the hydraulic mounts on the TRA decoupling of a powertrain system is analytically examined in terms of eigensolutions, frequency, and impulse responses, and then a new analytical axiom is proposed based on the TRA decoupling indices. With the experimental setup of a fixed decoupler hydraulic mount in the context of non-resonant dynamic stiffness testing procedure, the quasi-linear model of the hydraulic mount is verified by comparing the predictions with the measurement. And the quasi-linear formulation of the coupled system is also verified by comparing the frequency responses with the numerical results obtained by the direct inversion method. Finally, the mounting system with a combination of hydraulic mounts is redesigned in terms of the stiffness, damping and mount locations by satisfying the new axiom. The frequency and time domain results of the redesigned system demonstrate that the torque roll axis of the redesigned powertrain mounting system is indeed decoupled in the presence of hydraulic mounts (given oscillating torque or impulsive torque excitation). The proposed research provides an important basis and method for the research on a powertrain system with spectrally-varying mount properties, especially for the TRA decoupling.展开更多
To improve high-speed road feel and enhance energetic efficiency of hydraulic power steering(HPS) system in heavy-duty vehicles, an electromagnetic slip coupling(ESC) was applied to the steering system, which regulate...To improve high-speed road feel and enhance energetic efficiency of hydraulic power steering(HPS) system in heavy-duty vehicles, an electromagnetic slip coupling(ESC) was applied to the steering system, which regulated discharge flow of steering pump to realize variable assist characteristic as well as uniquely transfer on-demand power from engine to steering pump. The model of ESC was established and the dynamic characteristics of ESC were presented by the way of simulation and experiment. Upon the layout of the assist characteristics, output torque of ESC was derived. Based on the ESC model, the output torque characteristics of ESC were simulated under steering situation and straight driving situation, respectively. The consistency of simulated ESC output torque and the one deduced from assist characteristics verifies the correctness of the ESC dynamic model. To illustrate energy saving characteristics of ESC-HPS, energy consumption comparison of ESC-HPS and conventional HPS was carried out qualitatively and quantitatively. It follows that the energy consumption of ESC-HPS decreases by 50% compared with that of HPS.展开更多
In the core of a molten salt fast reactor(MSFR),heavy metal fuel and fission products can be dissolved in a molten fluoride salt to form a eutectic mixture that acts as both fuel and coolant.Fission energy is released...In the core of a molten salt fast reactor(MSFR),heavy metal fuel and fission products can be dissolved in a molten fluoride salt to form a eutectic mixture that acts as both fuel and coolant.Fission energy is released from the fuel salt and transferred to the second loop by fuel salt circulation.Therefore,the MSFR is characterized by strong interaction between the neutronics and the thermal hydraulics.Moreover,recirculation flow occurs,and nuclear heat is accumulated near the fertile blanket,which significantly affects both the flow and the temperature fields in the core.In this work,to further optimize the conceptual geometric design of the MSFR,three geometries of the core and fertile blanket are proposed,and the thermal-hydraulic characteristics,including the three-dimensional flow and temperature fields of the fuel and fertile salts,are simulated and analyzed using a coupling scheme between the open source codes OpenMC and OpenFOAM.The numerical results indicate that a flatter core temperature distribution can be obtained and the hot spot and flow stagnation zones that appear in the upper and lower parts of the core center near the reflector can be eliminated by curving both the top and bottom walls of the core.Moreover,eight cooling loops with a total flow rate of0.0555 m3 s-1 ensur an acceptable temperature distribusure an acceptable temperature distribution in the fertile blanket.展开更多
Natural fractures(NFs)are common in shale and tight reservoirs,where staged multi-cluster fracturing of horizontal wells is a prevalent technique for reservoir stimulation.While NFs and stress interference are recogni...Natural fractures(NFs)are common in shale and tight reservoirs,where staged multi-cluster fracturing of horizontal wells is a prevalent technique for reservoir stimulation.While NFs and stress interference are recognized as significant factors affecting hydraulic fracture(HF)propagation,the combined influence of these factors remains poorly understood.To address this knowledge gap,a novel coupled hydromechanical-damage(HMD)model based on the phase field method is developed to investigate the propagation of multi-cluster HFs in fractured reservoirs.The comprehensive energy functional and control functions are established,while incorporating dynamic fluid distribution between multiple perforation clusters and refined changes in rock mechanical parameters during hydraulic fracturing.The HMD coupled multi-cluster HF propagation model investigates various scenarios,including single HF and single NF,reservoir heterogeneity,single HF and NF clusters,and multi-cluster HFs with NF clusters.The results show that the HMD coupling model can accurately capture the impact of approach angle(θ),stress difference and cementation strength on the interaction of HF and NF.The criterion of the open and cross zones is not fixed.The NF angle(a)is not a decisive parameter to discriminate the interaction.According to the relationship between approach angle(θ)and NF angle(a),the contact relationship of HF can be divided into three categories(θ=a,θ<a,andθ>a).The connected NF can increase the complexity of HF by inducing it to form branch fracture,resulting in a fractal dimension of HF as high as2.1280 at angles of±45°.Inter-fracture interference from the heel to the toe of HF shows the phenomenon of no,strong and weak interference.Interestingly,under the influence of NFs,distant HFs from the injection can become dominant fractures.However,as a gradually increases,inter-fracture stress interference becomes the primary factor influencing HF propagation,gradually superseding the dominance of NF induced fractures.展开更多
As the power transmission system of an aircraft,a hydraulic pipeline system is equivalent to the " blood vessel" of the aircraft. With the development of aircraft hydraulic system to high pressure,high speed...As the power transmission system of an aircraft,a hydraulic pipeline system is equivalent to the " blood vessel" of the aircraft. With the development of aircraft hydraulic system to high pressure,high speed and high power ratio,the fluid-structure interaction vibration mechanism of hydraulic pipeline is more complex and the influence of friction coupling on vibration cannot be ignored. The fluid-structure interaction of hydraulic pipeline will lead to system vibration,lower reliability of system operation and even pipeline rupture. Taking a hydraulic pipeline of C919 aircraft wingtip as the research object,a 14-equation model of fluid-structure interaction vibration considering friction coupling effect is established in this paper. The effects of friction and fluid parameters on the pipeline fluid-structure interaction vibration characteristics are studied and verified by experiments. The research results will provide theoretical guidance for the analysis of the pipeline fluid-structure interaction vibration and have important theoretical significance and great engineering value for promoting the localization process of large aircraft.展开更多
The virtual prototyping models of the mechanical, hydraulic and control system of the ITER tractor were built with CATIA, ADAMS and MATLAB/Simulink respectively according to its heavy load and high precision character...The virtual prototyping models of the mechanical, hydraulic and control system of the ITER tractor were built with CATIA, ADAMS and MATLAB/Simulink respectively according to its heavy load and high precision characteristics, and the data transfer between the different models was accomplished by the integration interface between different software. Consequently the virtual experimental platform for the multi-disciplinary co-simulation was established. A co-simulation study of the mechanical-hydraulic-control coupling system of the ITER tractor was carried out. The synchronization servo control of parallel hydraulic cylinders was implemented, and the tracking control of the preconcerted trajectory of the hydraulic cylinders was realized on the established experimental platform. This paper presents the optimization design and technology rebuilding for the complicated coupling system with its theoretic foundation and co-simulation virtual experimental platform.展开更多
In order to solve the coupling problem of power in Hydraulic Hybrid City Bus (HHB), a hydraulic hybrid power coupling system based on planetary gear transmission principle is proposed in this paper. The system consist...In order to solve the coupling problem of power in Hydraulic Hybrid City Bus (HHB), a hydraulic hybrid power coupling system based on planetary gear transmission principle is proposed in this paper. The system consists of diesel engine, power coupler, hydraulic pump/motor, etc. The realizable operating modes of power coupling system are analyzed in this paper. Under coordination of clutches, the engine driven mode, hydraulic driven mode, hybrid driven mode, hydraulic engine-start mode and braking energy recovery mode are realizable. Based on Lagrange equation, kinetic analysis and kinematics analyses are presented. In addition, the simulation model of the power coupling system is proposed, which includes diesel engine model, power coupler model, hydraulic pump/motor model, etc. The example simulation analysis is proposed under the hybrid driven mode;the results show that the power coupling system proposed in this paper can realize power coupling of hydraulic hybrid city bus. Compared with traditional city bus, the hydraulic hybrid city bus can choose small-displacement engine so as to improve fuel economy and dynamic property.展开更多
Rigid model of the aerial work platform and hydraulic model of the oscillating mechanism were established with ADAMS. The simulation of two parameters, cy-linder force and oil chamber pressure, was carried out. The si...Rigid model of the aerial work platform and hydraulic model of the oscillating mechanism were established with ADAMS. The simulation of two parameters, cy-linder force and oil chamber pressure, was carried out. The simulation result is useful to the design of the oscillating mechanism.展开更多
Hydroformed parts are widely used in industrial automotive parts because of their higher stiffness and fatigue strength and reduced weight relative to their corresponding cast and welded parts.This paper reports a hyd...Hydroformed parts are widely used in industrial automotive parts because of their higher stiffness and fatigue strength and reduced weight relative to their corresponding cast and welded parts.This paper reports a hydraulicforming experimental platform for rectangular tube fittings that was constructed to conduct an experiment on the hydraulic forming of rectangular tube fittings.A finite element model was established on the basis of the fluid–solid coupling method and simulation analysis.The correctness of the simulation analysis and the feasibility of the fluid–solid coupling method for hydraulic forming simulation analysis were verified by comparing the experimental results with the simulation results.On the basis of the simulation analysis of the hydraulic process of the torsion beam using the fluid–solid coupling method,a sliding mold suitable for the hydroforming of torsion beams was designed for its structural characteristics.The effects of fluid characteristics,shaping pressure,axial feed rate,and friction coefficient on the wall thicknesses of torsions beams during formation were investigated.Fluid movement speed was related to tube deformation.Shaping pressure had a significant effect on rounded corners and straight edges.The axial feed speed was increased,and the uneven distribution of wall thicknesses was effectively improved.Although the friction coefficient had a nonsignificant effect on the wall thickness of the ladder-shaped region,it had a significant influence on a large deformation of wall thickness in the V-shaped area.In this paper,a method of fluid-solid coupling simulation analysis and sliding die is proposed to study the high pressure forming law in torsion beam.展开更多
The coupling vibration of a hydraulic pipe system consisting of two pipes is studied.The pipes are installed in parallel and fixed at their ends,and are restrained by clips to one bracket at their middle points.The pi...The coupling vibration of a hydraulic pipe system consisting of two pipes is studied.The pipes are installed in parallel and fixed at their ends,and are restrained by clips to one bracket at their middle points.The pipe subjected to the basement excitation at the left end is named as the active pipe,while the pipe without excitation is called the passive pipe.The clips between the two pipes are the bridge for the vibration energy.The adjacent natural frequencies will enhance the vibration coupling.The governing equation of the coupled system is deduced by the generalized Hamilton principle,and is discretized to the modal space.The modal correction is used during the discretization.The investigation on the natural characters indicates that the adjacent natural frequencies can be adjusted by the stiffness of the two clips and bracket.The harmonic balance method(HBM)is used to study the responses in the adjacent natural frequency region.The results show that the vibration energy transmits from the active pipe to the passive pipe swimmingly via the clips together with a flexible bracket,while the locations of them are not node points.The adjacent natural frequencies may arouse wide resonance curves with two peaks for both pipes.The stiffness of the clip and bracket can release the vibration coupling.It is suggested that the stiffness of the clip on the passive pipe should be weak and the bracket should be strong enough.In this way,the vibration energy is reflected by the almost rigid bracket,and is hard to transfer to the passive pipe via a soft clip.The best choice is to set the clips at the pipe node points.The current work gives some suggestions for weakening the coupled vibration during the dynamic design of a coupled hydraulic pipe system.展开更多
A complex interface exists between waterflow and solid particles during hydraulic soil erosion.In this study,the particle discrete element method(DEM)has been used to simulate the hydraulic erosion of a granular soil ...A complex interface exists between waterflow and solid particles during hydraulic soil erosion.In this study,the particle discrete element method(DEM)has been used to simulate the hydraulic erosion of a granular soil under moving bed conditions and surrounding terrain changes.Moreover,the weakly compressible smoothed particle hydrodynamics(WCSPH)approach has been exploited to simulate the instability process of the free surfacefluid and its propagation characteristics at the solid–liquid interface.The influence of a suspended medium on the waterflow dynamics has been characterized using the mixed viscosity concept accounting for the solid–liquid mixed particle volume ratio.Numerical simulations of wall-jet scouring and reservoir sedimentflushing on a mobile bed were performed and validated with experiments.The results show that the proposed WCSPH–DEM coupling model is highly suitable for determining parameters,such as the local maximum scour depth,the scour pit width,and the sand bed profile.The effects on the hydraulic erosion process of two important para-meters of the mixed viscosity coefficient(initial solid volume concentration and initial viscosity coefficient)are also discussed to a certain extent in this study.展开更多
Tension Leg Platform(TLP)in deepwater oil and gas field development usually consists of a hull,tendons,and top tension risers(TTRs).To maintain its top tension,each TTR is connected with a tensioner system to the hull...Tension Leg Platform(TLP)in deepwater oil and gas field development usually consists of a hull,tendons,and top tension risers(TTRs).To maintain its top tension,each TTR is connected with a tensioner system to the hull.Owing to the complicated configuration of the tensioners,the hull and TTRs form a strong coupled system.Traditionally,some simplified tensioner models are applied to analyze the TLP structures.There is a large discrepancy between their analysis results and the actual mechanism behaviors of a tensioner.It is very necessary to develop a more detailed tensioner model to consider the coupling effects between TLP and TTRs.In the present study,a fully coupled TLP hull-TTR system for hydrodynamic numerical simulation is established.A specific hydraulic pneumatic tensioner is modeled by considering 4 cylinders.The production TTR model is stacked up by specific riser joints.The simulation is also extended to analyze an array of TTRs.Different regular and irregular waves are considered.The behaviors of different cylinders are presented.The results show that it is important to consider the specific configurations of the tensioner and TTRs,which may lead to obviously different response behaviors,compared with those from a simplified model.展开更多
By considering the thermo poroelastic effects of rock,the constitutive relationship of fatigue deterioration of rock under cyclic loading,elastic-brittle failure criteria and wellbore stress superposition effects,a th...By considering the thermo poroelastic effects of rock,the constitutive relationship of fatigue deterioration of rock under cyclic loading,elastic-brittle failure criteria and wellbore stress superposition effects,a thermal-hydraulic-mechanicalfatigue damage coupled model for fracture propagation during soft hydraulic fracturing in hot dry rock(HDR)was established and validated.Based on this model,numerical simulations were conducted to investigate the fracture initiation and propagation characteristics in HDR under the combined effects of different temperatures and cyclic loading.The results are obtained in three aspects.First,cyclic injection,fluid infiltration,pore pressure accumulation,and rock strength deterioration collectively induce fatigue damage of rocks during soft hydraulic fracturing.Second,the fracture propagation pattern of soft hydraulic fracturing in HDR is jointly controlled by temperature difference and cyclic loading.A larger temperature difference generates stronger thermal stress,facilitating the formation of complex fracture networks.As cyclic loading decreases,the influence range of thermal stress expands.When the cyclic loading is 90%pb and 80%pb(where pb is the breakdown pressure during conventional hydraulic fracturing),the stimulated reservoir area increases by 88.33% and 120%,respectively,compared to conventional hydraulic fracturing(with an injection temperature of 25℃).Third,as cyclic loading is further reduced,the reservoir stimulation efficiency diminishes.When the cyclic loading decreases to 70%pb,the fluid pressure far away from the wellbore cannot reach the minimum breakdown pressure of the rock,resulting in no macroscopic hydraulic fractures.展开更多
基金supported by National Natural Science Foundation of China (Grant Nos. 51075112, 51175135)Fundamental Research Funds for the Central Universities of China (Grant Nos. 2012HGBZ0618,2013HGBH0008)
文摘The existing torque roll axis(TRA) decoupling theories for a powertrain mounting system assume that the stiffness and viscous damping properties are constant. However, real-life mounts exhibit considerable spectrally varying stiffness and damping characteristics, and the influence of the spectrally-varying properties of the hydraulic mounts on the powertrain system cannot be ignored. To overcome the deficiency, an analytical quasi-linear model of the hydraulic mount and the coupled properties of the powertrain and hydraulic mounts system are formulated. The influence of the hydraulic mounts on the TRA decoupling of a powertrain system is analytically examined in terms of eigensolutions, frequency, and impulse responses, and then a new analytical axiom is proposed based on the TRA decoupling indices. With the experimental setup of a fixed decoupler hydraulic mount in the context of non-resonant dynamic stiffness testing procedure, the quasi-linear model of the hydraulic mount is verified by comparing the predictions with the measurement. And the quasi-linear formulation of the coupled system is also verified by comparing the frequency responses with the numerical results obtained by the direct inversion method. Finally, the mounting system with a combination of hydraulic mounts is redesigned in terms of the stiffness, damping and mount locations by satisfying the new axiom. The frequency and time domain results of the redesigned system demonstrate that the torque roll axis of the redesigned powertrain mounting system is indeed decoupled in the presence of hydraulic mounts (given oscillating torque or impulsive torque excitation). The proposed research provides an important basis and method for the research on a powertrain system with spectrally-varying mount properties, especially for the TRA decoupling.
基金Project(51275211)supported by the National Natural Science Foundation of ChinaProject(11KJA580001)supported by the Natural Science Fund for Colleges and Universities in Jiangsu Province,ChinaProject(CXZZ12_0665)supported by the Postgraduate Innovation Natural Science Foundation of Jiangsu Province,China
文摘To improve high-speed road feel and enhance energetic efficiency of hydraulic power steering(HPS) system in heavy-duty vehicles, an electromagnetic slip coupling(ESC) was applied to the steering system, which regulated discharge flow of steering pump to realize variable assist characteristic as well as uniquely transfer on-demand power from engine to steering pump. The model of ESC was established and the dynamic characteristics of ESC were presented by the way of simulation and experiment. Upon the layout of the assist characteristics, output torque of ESC was derived. Based on the ESC model, the output torque characteristics of ESC were simulated under steering situation and straight driving situation, respectively. The consistency of simulated ESC output torque and the one deduced from assist characteristics verifies the correctness of the ESC dynamic model. To illustrate energy saving characteristics of ESC-HPS, energy consumption comparison of ESC-HPS and conventional HPS was carried out qualitatively and quantitatively. It follows that the energy consumption of ESC-HPS decreases by 50% compared with that of HPS.
基金supported by the Chinese TMSR Strategic Pioneer Science and Technology Project(No.XDA02010000)the Frontier Science Key Program of the Chinese Academy of Sciences(No.QYZDY-SSW-JSC016)。
文摘In the core of a molten salt fast reactor(MSFR),heavy metal fuel and fission products can be dissolved in a molten fluoride salt to form a eutectic mixture that acts as both fuel and coolant.Fission energy is released from the fuel salt and transferred to the second loop by fuel salt circulation.Therefore,the MSFR is characterized by strong interaction between the neutronics and the thermal hydraulics.Moreover,recirculation flow occurs,and nuclear heat is accumulated near the fertile blanket,which significantly affects both the flow and the temperature fields in the core.In this work,to further optimize the conceptual geometric design of the MSFR,three geometries of the core and fertile blanket are proposed,and the thermal-hydraulic characteristics,including the three-dimensional flow and temperature fields of the fuel and fertile salts,are simulated and analyzed using a coupling scheme between the open source codes OpenMC and OpenFOAM.The numerical results indicate that a flatter core temperature distribution can be obtained and the hot spot and flow stagnation zones that appear in the upper and lower parts of the core center near the reflector can be eliminated by curving both the top and bottom walls of the core.Moreover,eight cooling loops with a total flow rate of0.0555 m3 s-1 ensur an acceptable temperature distribusure an acceptable temperature distribution in the fertile blanket.
基金supported by the National Natural Science Foundation of China(No.52174045)。
文摘Natural fractures(NFs)are common in shale and tight reservoirs,where staged multi-cluster fracturing of horizontal wells is a prevalent technique for reservoir stimulation.While NFs and stress interference are recognized as significant factors affecting hydraulic fracture(HF)propagation,the combined influence of these factors remains poorly understood.To address this knowledge gap,a novel coupled hydromechanical-damage(HMD)model based on the phase field method is developed to investigate the propagation of multi-cluster HFs in fractured reservoirs.The comprehensive energy functional and control functions are established,while incorporating dynamic fluid distribution between multiple perforation clusters and refined changes in rock mechanical parameters during hydraulic fracturing.The HMD coupled multi-cluster HF propagation model investigates various scenarios,including single HF and single NF,reservoir heterogeneity,single HF and NF clusters,and multi-cluster HFs with NF clusters.The results show that the HMD coupling model can accurately capture the impact of approach angle(θ),stress difference and cementation strength on the interaction of HF and NF.The criterion of the open and cross zones is not fixed.The NF angle(a)is not a decisive parameter to discriminate the interaction.According to the relationship between approach angle(θ)and NF angle(a),the contact relationship of HF can be divided into three categories(θ=a,θ<a,andθ>a).The connected NF can increase the complexity of HF by inducing it to form branch fracture,resulting in a fractal dimension of HF as high as2.1280 at angles of±45°.Inter-fracture interference from the heel to the toe of HF shows the phenomenon of no,strong and weak interference.Interestingly,under the influence of NFs,distant HFs from the injection can become dominant fractures.However,as a gradually increases,inter-fracture stress interference becomes the primary factor influencing HF propagation,gradually superseding the dominance of NF induced fractures.
基金Supported by the National Key Basic Research Program of China(No.2014CB046405)
文摘As the power transmission system of an aircraft,a hydraulic pipeline system is equivalent to the " blood vessel" of the aircraft. With the development of aircraft hydraulic system to high pressure,high speed and high power ratio,the fluid-structure interaction vibration mechanism of hydraulic pipeline is more complex and the influence of friction coupling on vibration cannot be ignored. The fluid-structure interaction of hydraulic pipeline will lead to system vibration,lower reliability of system operation and even pipeline rupture. Taking a hydraulic pipeline of C919 aircraft wingtip as the research object,a 14-equation model of fluid-structure interaction vibration considering friction coupling effect is established in this paper. The effects of friction and fluid parameters on the pipeline fluid-structure interaction vibration characteristics are studied and verified by experiments. The research results will provide theoretical guidance for the analysis of the pipeline fluid-structure interaction vibration and have important theoretical significance and great engineering value for promoting the localization process of large aircraft.
基金supported by design of the ITER transfer casks system (ITER International Team) ITA 23-01-CNthe Key Laboratory of Biomimetic Sensing and Advanced Robot Technology,Anhui Province,China
文摘The virtual prototyping models of the mechanical, hydraulic and control system of the ITER tractor were built with CATIA, ADAMS and MATLAB/Simulink respectively according to its heavy load and high precision characteristics, and the data transfer between the different models was accomplished by the integration interface between different software. Consequently the virtual experimental platform for the multi-disciplinary co-simulation was established. A co-simulation study of the mechanical-hydraulic-control coupling system of the ITER tractor was carried out. The synchronization servo control of parallel hydraulic cylinders was implemented, and the tracking control of the preconcerted trajectory of the hydraulic cylinders was realized on the established experimental platform. This paper presents the optimization design and technology rebuilding for the complicated coupling system with its theoretic foundation and co-simulation virtual experimental platform.
文摘In order to solve the coupling problem of power in Hydraulic Hybrid City Bus (HHB), a hydraulic hybrid power coupling system based on planetary gear transmission principle is proposed in this paper. The system consists of diesel engine, power coupler, hydraulic pump/motor, etc. The realizable operating modes of power coupling system are analyzed in this paper. Under coordination of clutches, the engine driven mode, hydraulic driven mode, hybrid driven mode, hydraulic engine-start mode and braking energy recovery mode are realizable. Based on Lagrange equation, kinetic analysis and kinematics analyses are presented. In addition, the simulation model of the power coupling system is proposed, which includes diesel engine model, power coupler model, hydraulic pump/motor model, etc. The example simulation analysis is proposed under the hybrid driven mode;the results show that the power coupling system proposed in this paper can realize power coupling of hydraulic hybrid city bus. Compared with traditional city bus, the hydraulic hybrid city bus can choose small-displacement engine so as to improve fuel economy and dynamic property.
文摘Rigid model of the aerial work platform and hydraulic model of the oscillating mechanism were established with ADAMS. The simulation of two parameters, cy-linder force and oil chamber pressure, was carried out. The simulation result is useful to the design of the oscillating mechanism.
基金Natural Science Foundation of China(Grant No.81960332)Guangxi Provincial Innovation driven Development Project(Grant No.GKAA17204062)+1 种基金Guangxi Provincial Natural Science Foundation(Grant No.2016GXNSFAA380211)Liuzhou Municipal Scientific Research and Technology Development Plan(Grant No.2016C050203)。
文摘Hydroformed parts are widely used in industrial automotive parts because of their higher stiffness and fatigue strength and reduced weight relative to their corresponding cast and welded parts.This paper reports a hydraulicforming experimental platform for rectangular tube fittings that was constructed to conduct an experiment on the hydraulic forming of rectangular tube fittings.A finite element model was established on the basis of the fluid–solid coupling method and simulation analysis.The correctness of the simulation analysis and the feasibility of the fluid–solid coupling method for hydraulic forming simulation analysis were verified by comparing the experimental results with the simulation results.On the basis of the simulation analysis of the hydraulic process of the torsion beam using the fluid–solid coupling method,a sliding mold suitable for the hydroforming of torsion beams was designed for its structural characteristics.The effects of fluid characteristics,shaping pressure,axial feed rate,and friction coefficient on the wall thicknesses of torsions beams during formation were investigated.Fluid movement speed was related to tube deformation.Shaping pressure had a significant effect on rounded corners and straight edges.The axial feed speed was increased,and the uneven distribution of wall thicknesses was effectively improved.Although the friction coefficient had a nonsignificant effect on the wall thickness of the ladder-shaped region,it had a significant influence on a large deformation of wall thickness in the V-shaped area.In this paper,a method of fluid-solid coupling simulation analysis and sliding die is proposed to study the high pressure forming law in torsion beam.
基金Project supported by the National Natural Science Foundation of China(No.12002195)the Pujiang Project of Shanghai Science and Technology Commission of China(No.20PJ1404000)。
文摘The coupling vibration of a hydraulic pipe system consisting of two pipes is studied.The pipes are installed in parallel and fixed at their ends,and are restrained by clips to one bracket at their middle points.The pipe subjected to the basement excitation at the left end is named as the active pipe,while the pipe without excitation is called the passive pipe.The clips between the two pipes are the bridge for the vibration energy.The adjacent natural frequencies will enhance the vibration coupling.The governing equation of the coupled system is deduced by the generalized Hamilton principle,and is discretized to the modal space.The modal correction is used during the discretization.The investigation on the natural characters indicates that the adjacent natural frequencies can be adjusted by the stiffness of the two clips and bracket.The harmonic balance method(HBM)is used to study the responses in the adjacent natural frequency region.The results show that the vibration energy transmits from the active pipe to the passive pipe swimmingly via the clips together with a flexible bracket,while the locations of them are not node points.The adjacent natural frequencies may arouse wide resonance curves with two peaks for both pipes.The stiffness of the clip and bracket can release the vibration coupling.It is suggested that the stiffness of the clip on the passive pipe should be weak and the bracket should be strong enough.In this way,the vibration energy is reflected by the almost rigid bracket,and is hard to transfer to the passive pipe via a soft clip.The best choice is to set the clips at the pipe node points.The current work gives some suggestions for weakening the coupled vibration during the dynamic design of a coupled hydraulic pipe system.
基金funded by the National Natural Science Foundation of China(No.51568022)the Science and Technology Project of Education Department,Jiangxi Province,China(No.GJJ217404).
文摘A complex interface exists between waterflow and solid particles during hydraulic soil erosion.In this study,the particle discrete element method(DEM)has been used to simulate the hydraulic erosion of a granular soil under moving bed conditions and surrounding terrain changes.Moreover,the weakly compressible smoothed particle hydrodynamics(WCSPH)approach has been exploited to simulate the instability process of the free surfacefluid and its propagation characteristics at the solid–liquid interface.The influence of a suspended medium on the waterflow dynamics has been characterized using the mixed viscosity concept accounting for the solid–liquid mixed particle volume ratio.Numerical simulations of wall-jet scouring and reservoir sedimentflushing on a mobile bed were performed and validated with experiments.The results show that the proposed WCSPH–DEM coupling model is highly suitable for determining parameters,such as the local maximum scour depth,the scour pit width,and the sand bed profile.The effects on the hydraulic erosion process of two important para-meters of the mixed viscosity coefficient(initial solid volume concentration and initial viscosity coefficient)are also discussed to a certain extent in this study.
基金The research was financially supported by the National Natural Science Foundation of China for Youth(Grant No.51609169)Guangxi Science and Technology Major Project(Grant No.Guike AA17292007)+2 种基金the National Key R&D Program of China(Grant No.2018YFC0310502)National Natural Science Foundation of China(Grant No.51779173)China Scholarship Council(CSC).
文摘Tension Leg Platform(TLP)in deepwater oil and gas field development usually consists of a hull,tendons,and top tension risers(TTRs).To maintain its top tension,each TTR is connected with a tensioner system to the hull.Owing to the complicated configuration of the tensioners,the hull and TTRs form a strong coupled system.Traditionally,some simplified tensioner models are applied to analyze the TLP structures.There is a large discrepancy between their analysis results and the actual mechanism behaviors of a tensioner.It is very necessary to develop a more detailed tensioner model to consider the coupling effects between TLP and TTRs.In the present study,a fully coupled TLP hull-TTR system for hydrodynamic numerical simulation is established.A specific hydraulic pneumatic tensioner is modeled by considering 4 cylinders.The production TTR model is stacked up by specific riser joints.The simulation is also extended to analyze an array of TTRs.Different regular and irregular waves are considered.The behaviors of different cylinders are presented.The results show that it is important to consider the specific configurations of the tensioner and TTRs,which may lead to obviously different response behaviors,compared with those from a simplified model.
基金Supported by the China National Natural Science Foundation Major Project(52192621)。
文摘By considering the thermo poroelastic effects of rock,the constitutive relationship of fatigue deterioration of rock under cyclic loading,elastic-brittle failure criteria and wellbore stress superposition effects,a thermal-hydraulic-mechanicalfatigue damage coupled model for fracture propagation during soft hydraulic fracturing in hot dry rock(HDR)was established and validated.Based on this model,numerical simulations were conducted to investigate the fracture initiation and propagation characteristics in HDR under the combined effects of different temperatures and cyclic loading.The results are obtained in three aspects.First,cyclic injection,fluid infiltration,pore pressure accumulation,and rock strength deterioration collectively induce fatigue damage of rocks during soft hydraulic fracturing.Second,the fracture propagation pattern of soft hydraulic fracturing in HDR is jointly controlled by temperature difference and cyclic loading.A larger temperature difference generates stronger thermal stress,facilitating the formation of complex fracture networks.As cyclic loading decreases,the influence range of thermal stress expands.When the cyclic loading is 90%pb and 80%pb(where pb is the breakdown pressure during conventional hydraulic fracturing),the stimulated reservoir area increases by 88.33% and 120%,respectively,compared to conventional hydraulic fracturing(with an injection temperature of 25℃).Third,as cyclic loading is further reduced,the reservoir stimulation efficiency diminishes.When the cyclic loading decreases to 70%pb,the fluid pressure far away from the wellbore cannot reach the minimum breakdown pressure of the rock,resulting in no macroscopic hydraulic fractures.
