Radial rotating oscillating heat pipes(R-OHPs)have excellent thermal performance and great potential for application in the thermal management of rotatory machinery.However,the heat transport behavior and temperature ...Radial rotating oscillating heat pipes(R-OHPs)have excellent thermal performance and great potential for application in the thermal management of rotatory machinery.However,the heat transport behavior and temperature characteristics of R-OHPs are complex,and their understanding is still limited,hence necessitating further research.In this study,thanks to an experimental investigation involving a copper R-OHP running with acetone and water,its thermal performance is evaluated,and then the temperature characteristics are analyzed by nonlinear dynamic analysis.The study reveals that the effective heat transfer coefficient of R-OHPs undergoes a notable increase with rising rotational speed,exhibiting a peak at a threshold speed value.Such a peak is present irrespectively of the working fluid,and,after exceeding the threshold,higher rotational speeds lead to a lower thermal performance.Based on nonlinear dynamic analysis,the power spectrum density of the evaporator temperature indicates a lack of dominant frequency in temperature signals,suggesting a complex behavior characterized by random oscillations of vapor slugs and liquid plugs.In order to better understand how strong the chaotic behavior is,an autocorrelation analysis was carried out,the OHP at static state has a stronger chaos than R-OHPs.The correlation dimension analysis of the evaporator temperature provides values ranging from 1.2 to 1.6,which together with the Lyapunov exponent calculations,further support an evident chaotic nature of R-OHPs.展开更多
Fluid-structure interaction （FSI） is essentially a dynamic phenomenon and always exists in fluid-filled pipe system. The four-equation model, which has been proved to be effective to describe and predict the phenome...Fluid-structure interaction （FSI） is essentially a dynamic phenomenon and always exists in fluid-filled pipe system. The four-equation model, which has been proved to be effective to describe and predict the phenomenon of FSI due to friction coupling and Poisson coupling being taken into account, is utilized to describe the FSI of fluid-filled pipe system. Terse compatibility equations are educed by the method of characteristics （MOC） to describe the fluid-filled pipe system. To shorten computing time needed to get the solutions under the condition of keeping accuracy requirement, two steps are adopted, firstly the time step Δt and divided number of the straight pipe are optimized, sec-ondly the mesh spacing Δz close to boundary is subdivided in several submeshes automatically ac-cording to the speed gradient of fluid. The mathematical model and arithmetic are validated by com-parisons between simulation solutions of two straight pipe systems and experiment known from lit-erature.展开更多
The limited availability of studies on the natural convection heat transfer characteristics of fluoride salt has hindered progress in the design of passive residual heat removal systems(PRHRS)for molten salt reactors....The limited availability of studies on the natural convection heat transfer characteristics of fluoride salt has hindered progress in the design of passive residual heat removal systems(PRHRS)for molten salt reactors.This paper presents results from a numerical investigation of natural convection heat transfer characteristics of fluoride salt and heat pipes in the drain tank of a PRHRS.Simulation results are compared with experimental data,demonstrating the accuracy of the calculation methodology.Temperature distribution of fluoride salt and heat transfer characteristics are obtained and analyzed.The radial temperature of liquid fluoride salt in the drain tank shows a uniform distribution,while temperatures increase with increase in axial height from the bottom to the top of the drain tank.In addition,natural convection intensity increases with increase in height of the heat pipes in the tank.Spacing between heat pipes has no obvious effect on the natural convection heat transfer coefficient.This study will contribute to the design of passive heat removal systems for advanced nuclear reactors.展开更多
Simulation investigation on fluid characteristics of the water hydraulic jet pipe servo valve （WHJPSV） is conducted through a commercial computational fluid dynamics （CFD） software package FLUENT. In particular, t...Simulation investigation on fluid characteristics of the water hydraulic jet pipe servo valve （WHJPSV） is conducted through a commercial computational fluid dynamics （CFD） software package FLUENT. In particular, the factors to fluid characteristics of WHJPSV are addressed, which include diameter combination of jet pipe and receiver pipe, jet pipe nozzle clearance, angle between two jet receiver pipes and deflection angle of the jet pipe. It is concluded from the results that： （i） Structural parameters have great influences on fluid characteristics of WHJPSV, when d1 = d2 = 0.3 mm, α= 45 , b = 0.5 mm, and the simulation exhibits better fluid characteristics; （ii） The magnitude of the recovery pressure and flow velocity increase almost linearly with the deflection angle of jet pipe. The research work in this paper is important for determining and optimizing the structural parameters of the jet pipe and jet receiver. The relevant conclusions could be extended to the study of other water hydraulic servo control components.展开更多
Coal dust explosion accidents often cause substantial property damage and casualties and frequently involve nano-sized coal dust.In order to study the impact of nano-sized coal on coal dust and methane–coal dust expl...Coal dust explosion accidents often cause substantial property damage and casualties and frequently involve nano-sized coal dust.In order to study the impact of nano-sized coal on coal dust and methane–coal dust explosions,a pipe test apparatus was used to analyze the explosion pressure characteristics of five types of micro-nano particle dusts(800 nm,1200 nm,45μm,60μm,and 75μm)at five concentrations(100 g/m3,250 g/m3,500 g/m3,750 g/m3,and 1000 g/m3).The explosion pressure characteristics were closely related to the coal dust particle size and concentration.The maximum explosion pressure,maximum rate of pressure rise,and deflagration index for nano-sized coal dust were larger than for its micro-sized counterpart,indicating that a nano-sized coal dust explosion is more dangerous.The highest deflagration index Kst for coal dust was 13.97 MPa/(m·s),indicating weak explosibility.When 7%methane was added to the air,the maximum deflagration index Kst for methane–coal dust was 42.62 MPa/(m·s),indicating very strong explosibility.This indicates that adding methane to the coal dust mixture substantially increased the hazard grade.展开更多
This paper presents an experimental study including visualization on a flat plate closed loop pulsating heat pipes.It consists of a total of 40 channels with square cross section(2 mm×2 mm,165 mm long) machined d...This paper presents an experimental study including visualization on a flat plate closed loop pulsating heat pipes.It consists of a total of 40 channels with square cross section(2 mm×2 mm,165 mm long) machined directly on an aluminum plate(180 mm×120 mm×3 mm) covered by a transparent plate.The working fluid employed is ethanol.As a result,various flow patterns and their transitions are observed and found to be related to the fluid fill ratio,input heat load and the device orientation.Also the operational characteristics and working mechanism are discussed.展开更多
The development of urbanization has led to an increase in the number and scale of construction projects and the types of building construction engineering are getting advance and diverse due to the rapid development o...The development of urbanization has led to an increase in the number and scale of construction projects and the types of building construction engineering are getting advance and diverse due to the rapid development of technology.One of them is the static pressure prestressed pipe pile which is the most commonly used technology in modern building construction work.It is mainly used for pile foundation in construction work,and it has the advantages in less pollution,low noise,and high efficiency compared to the traditional pile foundation.Study on the characteristics of static pressure prestressed pipe pile must be carried out and strengthened the research to increase the effectiveness and quality of static pressure prestressed pipe pile on construction works.This paper is mainly to analyzed the characteristic and construction technology of static pressure prestressed pipe piles on building construction work.展开更多
Due to the material problems and force majeure factors,the leakage will be occurred on the liquid-filled pipe resulting in waste of resources,environmental pollution and even endangering safety.Acoustic wave detection...Due to the material problems and force majeure factors,the leakage will be occurred on the liquid-filled pipe resulting in waste of resources,environmental pollution and even endangering safety.Acoustic wave detection technology is widely used in buried pipeline leak detection,this technology mainly uses the wave(n=0,s=1)in the pipeline acoustic wave to locate the leak.When the leakage acoustic signal propagates along the liquid-filled pipe,the frequency dispersion characteristics can be obtained by wavelet decomposition.And there is a time delay(time difference)value between the leaky acoustic signals collected by the sensors at both ends of the leak.The outputs show that the results obtained by wavelet decomposition are in good agreement with the theoretical calculation results.Based on the obtained dispersion relation,the time delay values at different characteristic frequencies are analyzed by the cross-correlation method,and the leak location accuracy is discussed.This research content provides theoretical support and engineering application guidance for pipe leakage location technology.展开更多
In the process of construction and service,high-grade line pipes will get defective,e.g.dents,which will change its stress and strain distribution characteristics and impact its service reliability.In this paper,a X80...In the process of construction and service,high-grade line pipes will get defective,e.g.dents,which will change its stress and strain distribution characteristics and impact its service reliability.In this paper,a X80 line pipe was taken as the research object.The distribution characteristics of the strain field in the X80 line pipe with plain dents with the change of dent depth under external load were analyzed using the finite element analysis software ABAQUS.Then,the strain distribution and microstructure characteristics in the dent zone were explored by conducting prefabrication test on physical dent.Finally,combined with the finite element simulation results,the strain distribution laws of the X80 line pipe with plain dent were discussed.And the following research results were obtained.First,under the same internal pressure,the strain distribution characteristics in the dent zone at different dent depths are similar,i.e.,the strain increases with the increase of the distance from the center of the dent,and decreases rapidly with the increase of the distance after the peak strain.Second,the strain increases with the increase of dent depth,and under the same internal pressure and dent depth,the axial strain is larger than the radial strain at the same location.Third,the greater the dent depth,the stronger the superposition effect of internal pressure and depth on the strain.Fourth,strain hardening occurs on the materials in the initial stage of the dent deformation.With the aggravation of deformation and the extension of dent radius,the strain response ability of materials increases,the grains at the bottom and side walls of the dent zone are elongated along the direction of maximum deformation,the lattice is distorted and strain hardening occurs.As a result,the dislocation density in this zone increases and the interaction occurs between dislocations,as a result,the strength of line steel is enhanced.In conclusion,the research results do well in predicting the stressestrain evolution laws in the process of dent,and provide a theoretical foundation and an experimental basis for studying the influence of mechanical damage on the service safety of pipelines.展开更多
Previous studies have demonstrated that the surge in jacking force during the Guanjingkou project is caused by the contact conditions of the debris bentonite slurry outside the pipe.Therefore,this paper further system...Previous studies have demonstrated that the surge in jacking force during the Guanjingkou project is caused by the contact conditions of the debris bentonite slurry outside the pipe.Therefore,this paper further systematically investigates the influence of different debris slurry mass ratios(SLRs)and different particle size distributions(PSDs)on the pipe-rock friction characteristics using friction tests.The test results reveal that under the same PSD,an adequate amount of slurry(with an SLR of 1:4)consistently yields the lowest friction coefficient.When the SLR is between 1:2 and 1:3,the viscosity of the slurry reaches its peak,resulting in the highest friction coefficient.Additionally,when the PSD is 1:1:5 and 1:1:15,the friction coefficient is primarily governed by the plowing effect at the contact surface.When the PSD is 5:1:1 and 15:1:1,the friction coefficient is mainly controlled by the void ratio(VR)of debris.In the case of PSDs 1:5:1 and 1:15:1,the friction coefficient is jointly controlled by the adhesion effect of high-viscosity slurry and the plowing effect at the contact surface,and it gradually shifts towards being dominated by the VR as the amount of debris increases.Regardless of the SLRs and PSDs,the continuous deposition of debris and the injection of slurry incessantly exacerbate both the plowing and adhesion effects,creating a vicious cycle.This is the reason why the high-pressure water flushing method can not only fail to resolve the issue but also accelerate the occurrence of the surge in jacking force.展开更多
To elucidate the relationship between pipeline erosion and wear during slurry transportation,this study considers three key influencing parameters,namely,the ratio of inlet to outlet pipe diameter,the length of the va...To elucidate the relationship between pipeline erosion and wear during slurry transportation,this study considers three key influencing parameters,namely,the ratio of inlet to outlet pipe diameter,the length of the variable diameter section,and the roughness of the pipe wall.The impact of these factors on pipeline erosion and wear is analyzed using a single-factor analysis approach.In particular,the Fluent software is employed to conduct the required numerical simulations for variable diameter elbows of varying morphologies.The results indicate that as the inlet to outlet diameter ratio increases,the wear on the pipe inlet and the outer wall of the elbow becomes increasingly pronounced.Notably,when the diameter ratio exceeds 0.8,there is a significant escalation in wear on both the inner and outer elbow walls.Initially,the maximum erosion rate decreases sharply with increasing diameter ratio before a stable condition is attained.Erosion wear in the variable diameter section exhibits a distinct layered distribution pattern.In this region,the wear range for a 40 mm length of the pipe body is relatively small;however,once this length exceeds 40 mm,the wear range expands,ultimately covering the entire pipe section.The length of the variable diameter section significantly influences the maximum erosion rate of the pipeline,with sections shorter than 80 mm experiencing the most severe effects,and showing an exponential decline in erosion rate.As the wall roughness gradually increases,the wear area on both cheeks of the bend section rapidly expands and tends to deepen further.When the roughness reaches 4 mm,the pipeline wear experiences a dramatic shift,resulting in extensive“spot-like”wear patterns emerging at the bottom and sides of the horizontal flow section,which previously exhibited no wear.展开更多
Targeting spontaneous coal combustion during stacking,we developed an efficient heat dissipation&self-supplied wireless temperature measurement system(SPWTM)with gravity heat pipe-thermoelectric integration for du...Targeting spontaneous coal combustion during stacking,we developed an efficient heat dissipation&self-supplied wireless temperature measurement system(SPWTM)with gravity heat pipe-thermoelectric integration for dual safety.The heat transfer characteristics and temperature measurement optimization of the system are experimentally investigated and verified in practical applications.The results show that,firstly,the effects of coal pile heat production power and burial depth,along with heat pipe startup and heat transfer characteristics.At 60 cmburial depth,the condensation section dissipates 98%coal pile heat via natural convection.Secondly,for the temperature measurement error caused by the heat pipe heat transfer temperature difference,the correction method of“superimposing the measured value with the heat transfer temperature difference”is proposed,and the higher the coal temperature,the better the temperature measurement accuracy.Finally,the system can quickly(≤1 h)reduce the temperature of the coal pile to the spontaneous combustion point,significantly inhibiting the spontaneous combustion phenomenon,the maximum temperature does not exceed 49.2℃.Meanwhile,it utilizes waste heat to drive thermoelectric power generation,realizing self-supplied,unattended,and long-term accurate temperature measurement and warning.In a word,synergistic active heat dissipation and self-powered temperature monitoring-warning ensure dual coal pile thermal safety.展开更多
单通道大通径压裂管汇具有连接简洁、安全和高效的优点,但其四通管冲蚀磨损严重,严重影响压裂管汇安全性。针对四通管的冲蚀磨损问题,采用DPM(Deformable Parts Model)研究四通管的冲蚀磨损特性,并探究压裂液排量、砂比、颗粒直径和流...单通道大通径压裂管汇具有连接简洁、安全和高效的优点,但其四通管冲蚀磨损严重,严重影响压裂管汇安全性。针对四通管的冲蚀磨损问题,采用DPM(Deformable Parts Model)研究四通管的冲蚀磨损特性,并探究压裂液排量、砂比、颗粒直径和流体动力黏度对冲蚀磨损的影响规律。结果表明:四通管的支管与出口直管相交的相贯线处和出口直管管壁左右两侧存在磨损,冲蚀模拟结果与实际四通管磨损区域相吻合;在排量16~24 m^(3)/min、砂比2%~10%、颗粒直径0.2~0.85 mm和流体动力黏度10~30 mPa·s工况下,四通管的冲蚀率随着排量、砂比和流体动力黏度的增大而增大,随着颗粒直径的增大而减小;冲蚀区域的面积随砂比的增大而显著增大,随颗粒直径的增大而减小,但几乎不受流体动力黏度的影响。四通管最大冲蚀磨损区域位于支管与出口直管相交的相贯线处,在实际应用过程中需要对该区域进行重点监测和防护处理,同时需要适当使用低黏度、大颗粒的压裂液以降低四通管的冲蚀磨损。展开更多
基金Supported by National Natural Science Foundation of China(Grant No.52205476)Jiangsu Provincial Natural Science Foundation(Grant No.BK20242040)+2 种基金Fundamental Research Funds for the Central Universities(Grant No.NG2024008)the Youth Talent Support Project of CASTthe Fund of Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology(Grant No.1005-ZAA20003-14)。
文摘Radial rotating oscillating heat pipes(R-OHPs)have excellent thermal performance and great potential for application in the thermal management of rotatory machinery.However,the heat transport behavior and temperature characteristics of R-OHPs are complex,and their understanding is still limited,hence necessitating further research.In this study,thanks to an experimental investigation involving a copper R-OHP running with acetone and water,its thermal performance is evaluated,and then the temperature characteristics are analyzed by nonlinear dynamic analysis.The study reveals that the effective heat transfer coefficient of R-OHPs undergoes a notable increase with rising rotational speed,exhibiting a peak at a threshold speed value.Such a peak is present irrespectively of the working fluid,and,after exceeding the threshold,higher rotational speeds lead to a lower thermal performance.Based on nonlinear dynamic analysis,the power spectrum density of the evaporator temperature indicates a lack of dominant frequency in temperature signals,suggesting a complex behavior characterized by random oscillations of vapor slugs and liquid plugs.In order to better understand how strong the chaotic behavior is,an autocorrelation analysis was carried out,the OHP at static state has a stronger chaos than R-OHPs.The correlation dimension analysis of the evaporator temperature provides values ranging from 1.2 to 1.6,which together with the Lyapunov exponent calculations,further support an evident chaotic nature of R-OHPs.
文摘Fluid-structure interaction （FSI） is essentially a dynamic phenomenon and always exists in fluid-filled pipe system. The four-equation model, which has been proved to be effective to describe and predict the phenomenon of FSI due to friction coupling and Poisson coupling being taken into account, is utilized to describe the FSI of fluid-filled pipe system. Terse compatibility equations are educed by the method of characteristics （MOC） to describe the fluid-filled pipe system. To shorten computing time needed to get the solutions under the condition of keeping accuracy requirement, two steps are adopted, firstly the time step Δt and divided number of the straight pipe are optimized, sec-ondly the mesh spacing Δz close to boundary is subdivided in several submeshes automatically ac-cording to the speed gradient of fluid. The mathematical model and arithmetic are validated by com-parisons between simulation solutions of two straight pipe systems and experiment known from lit-erature.
基金supported by the National Key R&D Program of China(No.2019YFB1901100)the National Natural Science Foundation of China(No.11705138)the China National Postdoctoral Program for Innovative Talents(No.BX201600124)。
文摘The limited availability of studies on the natural convection heat transfer characteristics of fluoride salt has hindered progress in the design of passive residual heat removal systems(PRHRS)for molten salt reactors.This paper presents results from a numerical investigation of natural convection heat transfer characteristics of fluoride salt and heat pipes in the drain tank of a PRHRS.Simulation results are compared with experimental data,demonstrating the accuracy of the calculation methodology.Temperature distribution of fluoride salt and heat transfer characteristics are obtained and analyzed.The radial temperature of liquid fluoride salt in the drain tank shows a uniform distribution,while temperatures increase with increase in axial height from the bottom to the top of the drain tank.In addition,natural convection intensity increases with increase in height of the heat pipes in the tank.Spacing between heat pipes has no obvious effect on the natural convection heat transfer coefficient.This study will contribute to the design of passive heat removal systems for advanced nuclear reactors.
基金supported by the National Natural Science Foundation of China (Grant Nos.50375056, 50775081, 51075007)the National High-Technology Research and Development Program of China (Grant No.2006AA09Z238)+1 种基金the New Century Excellent Talents in University of State Education Ministry (Grant No.NCET-07-0330)the Funding Project for Academic Human Resources Development in Institutions of Higher Learning Under the Jurisdiction of Beijing Municipality (Grant No.20090203)
文摘Simulation investigation on fluid characteristics of the water hydraulic jet pipe servo valve （WHJPSV） is conducted through a commercial computational fluid dynamics （CFD） software package FLUENT. In particular, the factors to fluid characteristics of WHJPSV are addressed, which include diameter combination of jet pipe and receiver pipe, jet pipe nozzle clearance, angle between two jet receiver pipes and deflection angle of the jet pipe. It is concluded from the results that： （i） Structural parameters have great influences on fluid characteristics of WHJPSV, when d1 = d2 = 0.3 mm, α= 45 , b = 0.5 mm, and the simulation exhibits better fluid characteristics; （ii） The magnitude of the recovery pressure and flow velocity increase almost linearly with the deflection angle of jet pipe. The research work in this paper is important for determining and optimizing the structural parameters of the jet pipe and jet receiver. The relevant conclusions could be extended to the study of other water hydraulic servo control components.
基金This research was supported by the National Key Research and Development Program of China(2016YFC0801800)the National Nature Science Foundation of China(51774291,51864045).
文摘Coal dust explosion accidents often cause substantial property damage and casualties and frequently involve nano-sized coal dust.In order to study the impact of nano-sized coal on coal dust and methane–coal dust explosions,a pipe test apparatus was used to analyze the explosion pressure characteristics of five types of micro-nano particle dusts(800 nm,1200 nm,45μm,60μm,and 75μm)at five concentrations(100 g/m3,250 g/m3,500 g/m3,750 g/m3,and 1000 g/m3).The explosion pressure characteristics were closely related to the coal dust particle size and concentration.The maximum explosion pressure,maximum rate of pressure rise,and deflagration index for nano-sized coal dust were larger than for its micro-sized counterpart,indicating that a nano-sized coal dust explosion is more dangerous.The highest deflagration index Kst for coal dust was 13.97 MPa/(m·s),indicating weak explosibility.When 7%methane was added to the air,the maximum deflagration index Kst for methane–coal dust was 42.62 MPa/(m·s),indicating very strong explosibility.This indicates that adding methane to the coal dust mixture substantially increased the hazard grade.
基金the Ger man National Science Foundation (GR-412/33-2)Shanghai Leading Academic Discipline Project (No.B604)
文摘This paper presents an experimental study including visualization on a flat plate closed loop pulsating heat pipes.It consists of a total of 40 channels with square cross section(2 mm×2 mm,165 mm long) machined directly on an aluminum plate(180 mm×120 mm×3 mm) covered by a transparent plate.The working fluid employed is ethanol.As a result,various flow patterns and their transitions are observed and found to be related to the fluid fill ratio,input heat load and the device orientation.Also the operational characteristics and working mechanism are discussed.
文摘The development of urbanization has led to an increase in the number and scale of construction projects and the types of building construction engineering are getting advance and diverse due to the rapid development of technology.One of them is the static pressure prestressed pipe pile which is the most commonly used technology in modern building construction work.It is mainly used for pile foundation in construction work,and it has the advantages in less pollution,low noise,and high efficiency compared to the traditional pile foundation.Study on the characteristics of static pressure prestressed pipe pile must be carried out and strengthened the research to increase the effectiveness and quality of static pressure prestressed pipe pile on construction works.This paper is mainly to analyzed the characteristic and construction technology of static pressure prestressed pipe piles on building construction work.
基金The authors gratefully acknowledge the support of the National Nature Science Foundation of China(No.11774378)。
文摘Due to the material problems and force majeure factors,the leakage will be occurred on the liquid-filled pipe resulting in waste of resources,environmental pollution and even endangering safety.Acoustic wave detection technology is widely used in buried pipeline leak detection,this technology mainly uses the wave(n=0,s=1)in the pipeline acoustic wave to locate the leak.When the leakage acoustic signal propagates along the liquid-filled pipe,the frequency dispersion characteristics can be obtained by wavelet decomposition.And there is a time delay(time difference)value between the leaky acoustic signals collected by the sensors at both ends of the leak.The outputs show that the results obtained by wavelet decomposition are in good agreement with the theoretical calculation results.Based on the obtained dispersion relation,the time delay values at different characteristic frequencies are analyzed by the cross-correlation method,and the leak location accuracy is discussed.This research content provides theoretical support and engineering application guidance for pipe leakage location technology.
基金supported by the National Key Research&Development Plan,“Damage Effect and Accident Investigation Technologies of the Burning Explosion of Dangerous Chemical Storage Facilities”(Grant No.2016YFC0801204).
文摘In the process of construction and service,high-grade line pipes will get defective,e.g.dents,which will change its stress and strain distribution characteristics and impact its service reliability.In this paper,a X80 line pipe was taken as the research object.The distribution characteristics of the strain field in the X80 line pipe with plain dents with the change of dent depth under external load were analyzed using the finite element analysis software ABAQUS.Then,the strain distribution and microstructure characteristics in the dent zone were explored by conducting prefabrication test on physical dent.Finally,combined with the finite element simulation results,the strain distribution laws of the X80 line pipe with plain dent were discussed.And the following research results were obtained.First,under the same internal pressure,the strain distribution characteristics in the dent zone at different dent depths are similar,i.e.,the strain increases with the increase of the distance from the center of the dent,and decreases rapidly with the increase of the distance after the peak strain.Second,the strain increases with the increase of dent depth,and under the same internal pressure and dent depth,the axial strain is larger than the radial strain at the same location.Third,the greater the dent depth,the stronger the superposition effect of internal pressure and depth on the strain.Fourth,strain hardening occurs on the materials in the initial stage of the dent deformation.With the aggravation of deformation and the extension of dent radius,the strain response ability of materials increases,the grains at the bottom and side walls of the dent zone are elongated along the direction of maximum deformation,the lattice is distorted and strain hardening occurs.As a result,the dislocation density in this zone increases and the interaction occurs between dislocations,as a result,the strength of line steel is enhanced.In conclusion,the research results do well in predicting the stressestrain evolution laws in the process of dent,and provide a theoretical foundation and an experimental basis for studying the influence of mechanical damage on the service safety of pipelines.
基金the funding support from the National Natural Science Foundations for Young Scientists of China(Grant No.52208391)Doctoral Foundation Project of Guizhou University(Grant No.2021e78).
文摘Previous studies have demonstrated that the surge in jacking force during the Guanjingkou project is caused by the contact conditions of the debris bentonite slurry outside the pipe.Therefore,this paper further systematically investigates the influence of different debris slurry mass ratios(SLRs)and different particle size distributions(PSDs)on the pipe-rock friction characteristics using friction tests.The test results reveal that under the same PSD,an adequate amount of slurry(with an SLR of 1:4)consistently yields the lowest friction coefficient.When the SLR is between 1:2 and 1:3,the viscosity of the slurry reaches its peak,resulting in the highest friction coefficient.Additionally,when the PSD is 1:1:5 and 1:1:15,the friction coefficient is primarily governed by the plowing effect at the contact surface.When the PSD is 5:1:1 and 15:1:1,the friction coefficient is mainly controlled by the void ratio(VR)of debris.In the case of PSDs 1:5:1 and 1:15:1,the friction coefficient is jointly controlled by the adhesion effect of high-viscosity slurry and the plowing effect at the contact surface,and it gradually shifts towards being dominated by the VR as the amount of debris increases.Regardless of the SLRs and PSDs,the continuous deposition of debris and the injection of slurry incessantly exacerbate both the plowing and adhesion effects,creating a vicious cycle.This is the reason why the high-pressure water flushing method can not only fail to resolve the issue but also accelerate the occurrence of the surge in jacking force.
基金supported by the project of the Educational Department of Liaoning Province(No.LJKMZ20220825)the National Natural Science Foundation of China(51774199).
文摘To elucidate the relationship between pipeline erosion and wear during slurry transportation,this study considers three key influencing parameters,namely,the ratio of inlet to outlet pipe diameter,the length of the variable diameter section,and the roughness of the pipe wall.The impact of these factors on pipeline erosion and wear is analyzed using a single-factor analysis approach.In particular,the Fluent software is employed to conduct the required numerical simulations for variable diameter elbows of varying morphologies.The results indicate that as the inlet to outlet diameter ratio increases,the wear on the pipe inlet and the outer wall of the elbow becomes increasingly pronounced.Notably,when the diameter ratio exceeds 0.8,there is a significant escalation in wear on both the inner and outer elbow walls.Initially,the maximum erosion rate decreases sharply with increasing diameter ratio before a stable condition is attained.Erosion wear in the variable diameter section exhibits a distinct layered distribution pattern.In this region,the wear range for a 40 mm length of the pipe body is relatively small;however,once this length exceeds 40 mm,the wear range expands,ultimately covering the entire pipe section.The length of the variable diameter section significantly influences the maximum erosion rate of the pipeline,with sections shorter than 80 mm experiencing the most severe effects,and showing an exponential decline in erosion rate.As the wall roughness gradually increases,the wear area on both cheeks of the bend section rapidly expands and tends to deepen further.When the roughness reaches 4 mm,the pipeline wear experiences a dramatic shift,resulting in extensive“spot-like”wear patterns emerging at the bottom and sides of the horizontal flow section,which previously exhibited no wear.
基金supported by the Engineering Research Centre for Digital Grid Technology for Coordinating New Energy under Grant[Grant number 2021GCZX003]Yunnan Fundamental Research Projects under Grant[Grant number 202301CF070031]+2 种基金Hundred Talents Project 2023 under Grant[Grant number B0201001]2024 Distinctive Innovation Scientific Research Projects for Higher Education Institutions[Grant number 2024KTSCX157]Young Innovative Talent Project under Grant[Grant numbers K0223021,K0224014].
文摘Targeting spontaneous coal combustion during stacking,we developed an efficient heat dissipation&self-supplied wireless temperature measurement system(SPWTM)with gravity heat pipe-thermoelectric integration for dual safety.The heat transfer characteristics and temperature measurement optimization of the system are experimentally investigated and verified in practical applications.The results show that,firstly,the effects of coal pile heat production power and burial depth,along with heat pipe startup and heat transfer characteristics.At 60 cmburial depth,the condensation section dissipates 98%coal pile heat via natural convection.Secondly,for the temperature measurement error caused by the heat pipe heat transfer temperature difference,the correction method of“superimposing the measured value with the heat transfer temperature difference”is proposed,and the higher the coal temperature,the better the temperature measurement accuracy.Finally,the system can quickly(≤1 h)reduce the temperature of the coal pile to the spontaneous combustion point,significantly inhibiting the spontaneous combustion phenomenon,the maximum temperature does not exceed 49.2℃.Meanwhile,it utilizes waste heat to drive thermoelectric power generation,realizing self-supplied,unattended,and long-term accurate temperature measurement and warning.In a word,synergistic active heat dissipation and self-powered temperature monitoring-warning ensure dual coal pile thermal safety.
