The safe driving and operation of trains is a necessary condition for ensuring the safe operation of trains.In particular,heavy-haul trains are characterized by the difficulty in driving and operation.Considering the ...The safe driving and operation of trains is a necessary condition for ensuring the safe operation of trains.In particular,heavy-haul trains are characterized by the difficulty in driving and operation.Considering the uncertainties in train driving and operation,this paper analyzes the relationship between the safety of heavy-haul electric locomotive hauled trains and driving and operation.It studies the auxiliary intelligent driving safety operation control methods.Through K-means to identify the characteristics of drivers'driving manipulation,the hidden Markov model adaptively adjusts the train driving and operation sequence,and conducts auxiliary driving reconstruction for heavy-haul locomotive driving and operation.Based on the train running curve and the locomotive traction/braking characteristics,it smoothly controls the exertion of the traction/braking force of heavy-haul locomotives,thereby optimizing the driving safety control of heavy-haul trains in the vehicle-environment-track system.Finally,the train operation simulation and optimized driving verification are carried out by simulating some track sections.The results show that the proposed method can correct and pre-optimize driving operations,improving the smoothness of heavy-haul trains by approximately 10%.It verifies the effectiveness of the proposed train assisted driving control reconstruction method,facilitating the smooth and safe operation of heavy-haul trains.展开更多
Railway noise barriers are an essential piece of infrastructure for reducing noise propagation.However,these barriers experience aerodynamic loads generated by high-speed trains,leading to dynamic effects that may com...Railway noise barriers are an essential piece of infrastructure for reducing noise propagation.However,these barriers experience aerodynamic loads generated by high-speed trains,leading to dynamic effects that may compromise their fatigue capacity.The most common structural design for railway noise barriers consists of vertical configurations of posts and panels.However,there have been few dynamic analyses of steel post/wood panel noise barriers under train-induced aerodynamic loads.This study used dynamic finite element analysis to assess the dynamic behavior of such noise barriers.Analysis of a 40-m-long noise barrier model and a triangular simplified load model,the latter of which effectively represented the detailed aerodynamic load,were first used to establish the model and input of the moving load during dynamic simulation.Then,the effects of different parameters on the dynamic response of the noise barrier were evaluated,including the damping ratio,the profile of the steel post,the span length of the panel,the barrier height,and the train speed.Gray relational analysis indicated that barrier height exhibited the highest correlations with the dynamic responses,followed by train speed,post profile,span length,and damping ratio.A reduction in the natural frequency and an increase in the train speed result in a higher peak response and more pronounced fluctuations between the nose and tail waves.The dynamic amplification factor(DAF)was found to be related to both the natural frequency and train speed.A model was proposed showing that the DAF significantly increases as the square of the natural frequency decreases and the cube of the train speed rises.展开更多
High-speed maglev trains(HSMTs)can run at high running speeds due to their unique design.The pressure waves that these trains generate while passing each other are therefore very intense,and can even have safety impli...High-speed maglev trains(HSMTs)can run at high running speeds due to their unique design.The pressure waves that these trains generate while passing each other are therefore very intense,and can even have safety implications.In order to reduce the transient impact of such waves,the standard k-ε turbulence model is used in this work to assess the effect of railway spacing on the aerodynamic loads,pressure and surrounding flow field of 600 km/h maglev trains passing each other in open air.The sliding mesh technique is used to determine the relative motion between the considered trains.The results show that the surface pressure is approximately linearly correlated with the square of the speed while the amplitude of the pressure wave on the train surface,side force,and rolling moment all have negative exponential relationships with the railway spacing.展开更多
Tunnel-induced noise amplification has become a major constraint for high-speed trains.This study employs a 1/10 scale three-coach high-speed train model,using the improved delayed detached eddy simulation(IDDES)metho...Tunnel-induced noise amplification has become a major constraint for high-speed trains.This study employs a 1/10 scale three-coach high-speed train model,using the improved delayed detached eddy simulation(IDDES)method coupled with the perturbed convective wave model to investigate the unsteady flow evolution,aerodynamic noise source distribution,and near-field acoustic characteristics of high-speed trains under open-air and tunnel conditions.The results show that the blocking effect of the tunnel wall enhances flow compression,increases local velocity,and aggravates flow disturbances and pressure fluctuations near the pantograph and tail car.In the tunnel,the total sound source energy reaches 1.14×10^(12)N^(2)/s^(2),5.26 times higher than in open air,with significant increases in the tail car,bogies,and pantograph.Bogie noise concentrates in the 50 to 1000 Hz range,while pantograph noise dominates from 1500 to 2500 Hz.Tunnel conditions further enhance peak distributions in the low and medium frequency bands.Although pressure disturbances on the train surface are mainly dominated by hydrodynamic effects,the radiated acoustic energy of the sound pressure levels on the roof and side surfaces is amplified by 33.3 and 22.6 times,far exceeding hydrodynamic energy amplification factors of 8.6 and 6.3.The study reveals coupled flow and acoustic mechanisms in tunnels,supporting noise reduction design for high-speed trains.展开更多
Indian Railways have been the largest people moving transport infrastructure in India.Over the years the systems and trains have been upgraded resulting in both better passenger amenities and reduction in travel time....Indian Railways have been the largest people moving transport infrastructure in India.Over the years the systems and trains have been upgraded resulting in both better passenger amenities and reduction in travel time.The newest addition is the Vande Bharat Express,a semi-high-speed train that was introduced in India in 2019.The train currently runs between 10 routes and has brought significant changes to India’s railway network.This article explores the introduction of Vande Bharat Express trains in India and its effects on the country’s interstation time-space shrinkage using cartographic techniques.The cartographic techniques like stepwise multidimensional scaling and interpolation using the distance cartogram plugin in QGIS are mainly used for generating the time-space maps for various speeds.The limitations of these techniques and the methods to overcome those limitations are also explored in this article.展开更多
High-Speed Trains (HSTs) have emerged as a mainstream mode of transportation in China, owing to their exceptional safety and efficiency. Ensuring the reliable operation of HSTs is of paramount economic and societal im...High-Speed Trains (HSTs) have emerged as a mainstream mode of transportation in China, owing to their exceptional safety and efficiency. Ensuring the reliable operation of HSTs is of paramount economic and societal importance. As critical rotating mechanical components of the transmission system, bearings make their fault diagnosis a topic of extensive attention. This paper provides a systematic review of image encoding-based bearing fault diagnosis methods tailored to the condition monitoring of HSTs. First, it categorizes the image encoding techniques applied in the field of bearing fault diagnosis. Then, a review of state-of-the-art studies has been presented, encompassing both monomodal image conversion and multimodal image fusion approaches. Finally, it highlights current challenges and proposes future research directions to advance intelligent fault diagnosis in HSTs, aiming to provide a valuable reference for researchers and engineers in the field of intelligent operation and maintenance.展开更多
This paper aims to explore the influence of different noise barrier heights on the sound source generation mechanisms of higher-speed trains(400 km/h)using a combination of delayed detached eddy simulation(DDES)and Ff...This paper aims to explore the influence of different noise barrier heights on the sound source generation mechanisms of higher-speed trains(400 km/h)using a combination of delayed detached eddy simulation(DDES)and Ffowcs Williams-Hawkings(FW-H)equations.Four cases are investigated and compared,i.e.1)no barrier,2)2.3 m,3)3.3 m,and 4)4.3 m single-side barriers on a bridge.Numerical results show that the presence of noise barriers causes an increase in sound source intensity ranging from 2.1 to 2.8 dB(A).However,the relationship between the barrier height and the increase in sound source intensity varies across different parts of the train.Compared with the head and front middle cars,the boundary layer is thicker around the rear-middle and tail car areas.A thick boundary layer introduces the influence of the crash wall,causing asymmetry and increases in sound source intensity.This is due to the deceleration region formed between the crash wall and the rail surface,as well as the acceleration region formed by the contraction of the flow channel in the noise barrier,both of which influence the sound source's characteristics.In addition,higher barriers exacerbate asymmetry and increases in sound source intensity.展开更多
Irregularities in the track and uneven forces acting on the train can cause shifts in the position of the superconducting magnetic levitation train relative to the track during operation.These shifts lead to asymmetri...Irregularities in the track and uneven forces acting on the train can cause shifts in the position of the superconducting magnetic levitation train relative to the track during operation.These shifts lead to asymmetries in the flow field structure on both sides of the narrow suspension gap,resulting in instability and deterioration of the train’s aerodynamic characteristics,significantly impacting its operational safety.In this study,we firstly validate the aerodynamic characteristics of the superconducting magnetic levitation system by developing a numerical simulation method based on wind tunnel test results.We then investigate the influence of lateral translation parameters on the train’s aerodynamic performance under conditions both with and without crosswinds.We aim to clarify the evolution mechanism of the flow field characteristics under the coupling effect between the train and the U-shaped track and to identify the most unfavorable operational parameters contributing to the deterioration of the train’s aerodynamic properties.The findings show that,without crosswinds,a lateral translation of 30 mm causes a synchronous resonance phenomenon at the side and bottom gaps of the train-track coupling,leading to the worst aerodynamic performance.Under crosswind conditions,a lateral translation of 40 mm maximizes peak pressure fluctuations and average turbulent kinetic energy around the train,resulting in the poorest aerodynamic performance.This research provides theoretical support for enhancing the operational stability of superconducting magnetic levitation trains.展开更多
High-speed railway holds a pivotal position in China's transportation system,closely intertwined with the production and daily lives of people.It serves as a critical carrier for fostering a new development paradi...High-speed railway holds a pivotal position in China's transportation system,closely intertwined with the production and daily lives of people.It serves as a critical carrier for fostering a new development paradigm,supporting high-quality growth,and building a modernized strong nation.Up to 2025,the high-speed railway operating mileage in China has exceeded 50000 km,ranking the first in the world and surpassing the combined total of high-speed railway operating mileage in all other countries.展开更多
Virtual coupling is a novel technology that enables trains to run closely together without physical connections through communication and automation systems.The paper addresses an adaptive polynomial approximation alg...Virtual coupling is a novel technology that enables trains to run closely together without physical connections through communication and automation systems.The paper addresses an adaptive polynomial approximation algorithm for the cooperative control of high-speed trains(HSTs)under virtual coupling.It aims to solve the cooperative tracking control problem of HST formation operations under various scenarios,including known and unknown parameters.To enable the HST formation system to achieve cooperative operation while ensuring an appropriate spacing distance,the tracking errors of displacement and speed throughout the entire operation converge to zero.The proposed control strategy focuses on adopting polynomial approximation to handle unknown parameters,which are estimated via adaptive laws.Additionally,the unknown parameters of the HSTs are estimated online through adaptive laws.Experimental results verify the effectiveness of this method.展开更多
The influence of train height on aerodynamic characteristics of high-speed train(HST)is significant in crosswind environments.This study employed the improved delayed detached eddy simulation(IDDES)turbulence model to...The influence of train height on aerodynamic characteristics of high-speed train(HST)is significant in crosswind environments.This study employed the improved delayed detached eddy simulation(IDDES)turbulence model to analyze the aerodynamic characteristics of trains with three different heights under a crosswind of 20 m/s.The numerical model was validated through comparison with wind tunnel experimental data.A comprehensive analysis was conducted on the characteristics of the flow field around trains,surface pressure distribution,and aerodynamic loads for trains with different heights.Results indicate that the side force coefficient increased by up to 61.54%with an increase in train height from 3.89 to 4.19 m.Compared with the 3.89 m case,the roll moment coefficient on the head,middle,and tail cars for 4.19 m cases increased by 18.11%,24.78%and 34.23%,respectively.The increase in train height widens the impact width of the leading car’s front vortex on the leeward side and intensifies the helical shedding and coupling interactions of two vortices in the wake,leading to an increase in the intensity and extent of wake flow in both vertical and longitudinal directions.Additionally,the increase in height shifted the flow separation point on the leeward side,moving vortices farther from the train,expanding the back-flow region,and intensifying Reynolds stress and turbulent fluctuations on the leeward side,which adversely impacted train stability and safety.The research findings can provide a reference for the design of train configurations and the assessment of dynamic performance in crosswind environments.展开更多
Arrival headway,the minimum time interval between two trains that consecutively stop in the same railway yard,significantly influences overall railway capacity and becomes a bottleneck in large high-speed railway yard...Arrival headway,the minimum time interval between two trains that consecutively stop in the same railway yard,significantly influences overall railway capacity and becomes a bottleneck in large high-speed railway yards.This occurs because the leading train slows considerably along the long receiving route to the yard;while,the following train continues at top speed,creating a substantial spatial and temporal interval between them.This paper proposes a speed profile intervention(SPI)approach to reduce arrival headway.By setting appropriate speed limits in specific block sections for each train,the following train decelerates in advance,thereby shortening the interval with its predecessor.We first study the impact of speed values and locations on arrival headway theoretically,then validate our findings through a multi-agent simulation approach to quantitatively investigate the relationship between headway and SPI parameters.Simulation experiments using real-world data from the Beijing–Shanghai high-speed railway demonstrate that the SPI approach can significantly reduce arrival headway without any infrastructure modifications.To mitigate potential side effects on travel time associated with this approach,we perform an analysis that involves setting appropriate speed limit values and selecting strategic locations for their implementation.展开更多
Virtual coupling(VC) is an emerging technology for addressing the shortage of rail transportation capacity. As a crucial enabling technology, the VC-specific acquisition of train information, especially train followin...Virtual coupling(VC) is an emerging technology for addressing the shortage of rail transportation capacity. As a crucial enabling technology, the VC-specific acquisition of train information, especially train following distance(TFD), is underdeveloped.In this paper, a novel method is proposed to acquire real-time TFD by analyzing the vibration response of the front and following trains, during which only onboard accelerometers and speedometers are required. In contrast to the traditional arts of train positioning, this method targets a relative position between two adjacent trains in VC operation, rather than the global positions of the trains. For this purpose, an adaptive system containing three strategies is designed to cope with possible adverse factors in train operation. A vehicle dynamics simulation of a heavy-haul railway is implemented for the evaluation of feasibility and performance. Furthermore, a validation is conducted using a set of data measured from in-service Chinese high-speed trains. The results indicate the method achieves satisfactory estimation accuracy using both simulated and actual data. It has favorable adaptability to various uncertainties possibly encountered in train operation. Additionally, the method is preliminarily proven to adapt to different locomotive types and even different rail transportation modes. In general, such a method with good performance, low-cost, and easy implementation is promising to apply.展开更多
With increasingly stringent requirements for the airtightness of high-speed train bodies,determining appropriate airtightness levels has become critically important.To calculate the airtightness of high-speed train bo...With increasingly stringent requirements for the airtightness of high-speed train bodies,determining appropriate airtightness levels has become critically important.To calculate the airtightness of high-speed train bodies more accurately,based on one-dimensional isentropic flow theory,this study derives cabin pressure calculation models for both positive and negative pressure conditions during static airtightness tests of high-speed train bodies.Since the flow coefficient,which is closely related to the leakage characteristics of the carriage,is influenced by multiple factors including operating pressure conditions(positive/negative),leakage path cross-sectional shape,and size,a flow coefficient calibration method is proposed to achieve high-precision and efficient calibration of the flow coefficient for trains with varying leakage properties.This method generates a series of flow coefficient values for circular and square cross-sectional shapes under both positive and negative pressure conditions across various cross-sectional areas.Furthermore,functional relationships between flow coefficient and leakage path area under positive/negative pressure are established through curve fitting.Using these functional relationships and the cabin pressure calculation model,the pressure variation curves for a static airtightness test are simulated.Specifically,for circular cross-sectional shapes,the theoretical curves under positive and negative pressure conditions exhibited R^(2) values of 0.9936 and 0.9931,respectively,when compared to experimental data,and for square cross-sectional shapes,the corresponding R^(2) values are 0.9928 and 0.9932,validating the accuracy of the proposed theoretical model.The proposed theoretical model effectively evaluates the airtightness of high-speed train bodies with varying performance levels during static airtightness tests,providing a robust theoretical reference for optimizing high-speed train airtightness design.展开更多
The stability of high-speed trains under crosswind conditions has become a key consideration in aerodynamic design.As running speeds continue to increase and car body weight decreases,crosswinds pose a greater risk to...The stability of high-speed trains under crosswind conditions has become a key consideration in aerodynamic design.As running speeds continue to increase and car body weight decreases,crosswinds pose a greater risk to train safety,significantly lowering the critical wind velocity.Therefore,developing strategies to enhance crosswind stability is essential.This study focuses on the leeward region adjacent to the train body,where separated flows with large vortices generate significant negative surface pressure.Enhancing this negative pressure distribution is proposed as a potential method to improve a train’s resistance to overturning.To achieve this,winglets are installed on the leeward side as a flow control measure,and their effects at different deflection angles are evaluated.The influence of five deflection angles on the leeward-side flow field and aerodynamic loads is analyzed,considering the head,middle,and tail cars.Results indicate that a deflection angle of 90°optimally reduces the overall overturning moment by 27.6%compared to the baseline model in a three-car configuration.These findings highlight that optimizing the winglet deflection angle to approximately 90°can significantly enhance a train’s resistance to overturning,offering valuable insights for aerodynamic optimization in strong wind conditions.展开更多
The metamaterial based on external meshing gears(MEG)is designed based on the principle of external meshing gear transmission.Based on the meshing transmission principle of external meshing gears and planetary gear tr...The metamaterial based on external meshing gears(MEG)is designed based on the principle of external meshing gear transmission.Based on the meshing transmission principle of external meshing gears and planetary gear trains,the internal and external gear rings are designed.Based on the internal and external gear rings,the metamaterial based on inner and outer planetary gear trains(MIP)is designed to study the shear modulus,Young's modulus,and amplitude-frequency characteristics of the metamaterial based on gears at different angles.The effects of the number of planetary gears on the physical characteristics of the MIP are studied.The results show that the MEG can be continuously adjusted by adjusting the shear modulus and Young's modulus due to its meshing characteristics.With the same number of gears,the adjustment range of the MIP is larger than the adjustment range of the MEG.When the number of planetary gears increases,the adjustment range of the MIP decreases.Moreover,when the metamaterial based on gears rotates,the harmonic response changes with the change of the angle.展开更多
The structural safety of high-speed trains is significantly endangered by increasing operating speeds.The objective of this research was to investigate the evolution of the flow field in trains passing through a tunne...The structural safety of high-speed trains is significantly endangered by increasing operating speeds.The objective of this research was to investigate the evolution of the flow field in trains passing through a tunnel while there is a strong crosswind at the tunnel entrance and exit.Moreover,the effect of aerodynamic pressure waves on structural strength was analyzed to evaluate the safety of the carbody.In this study,we selected the improved delayed detached-eddy simulation(IDDES)method as a turbulence model.The mechanism of interaction among the train,tunnel,and crosswind was evaluated through a complex computational fluid dynamics(CFD)model,simulating high-speed trains moving through tunnels at various crosswind speeds.Additionally,the dynamic stress response of the carbody was calculated using a sequential coupling approach,where integral aerodynamic forces were applied as substitutes for direct CFD pressure loads.We assessed the effect of aerodynamic loads on the dynamic stresses of the carbody at different crosswind velocities(0,10,15,and 20 m/s).The results indicate that crosswinds exert a substantial influence on the fluid structure surrounding the train.Consequently,the aerodynamic forces contribute significantly to potential damage to the carbody,posing increased safety risks for high-speed trains.展开更多
Considering passenger trains'key role in remote regions,this study employed machine vision technology to monitor five posture parameters of the second car of a conventional passenger train,aiming to investigate th...Considering passenger trains'key role in remote regions,this study employed machine vision technology to monitor five posture parameters of the second car of a conventional passenger train,aiming to investigate the influence of windbreaks and crosswinds along railways on the operating postures of conventional passenger trains.The study found that when passing through the anti-wind tunnel with holes,the amplitudes of posture parameters were smaller than those of other windbreaks,demonstrating the superior performance of this windbreak in maintaining posture stability compared to others.In tunnel sections,larger amplitudes of these parameters were observed for the tail car than the head car,while the opposite occurred in non-tunnel sections.Notably,during tunnel transit,their amplitudes did not increase monotonically with speed but peaked at a specific speed that most adversely affected the operating posture.These conclusions have a great significance for improving operating safety under crosswinds.展开更多
High-speed trains operating in freezing rain are highly susceptible to severe ice accretion in the pantograph region,which compromises both power transmission efficiency and dynamic performance.To elucidate the underl...High-speed trains operating in freezing rain are highly susceptible to severe ice accretion in the pantograph region,which compromises both power transmission efficiency and dynamic performance.To elucidate the underlying mechanisms of this phenomenon,an Euler-Euler multiphase flow model was employed to simulate droplet impingement and collection on the pantograph surface,while a glaze-ice formation model incorporating wall film dynamics was used to capture the subsequent growth of ice.The effects of key parameters—including liquid water content,ambient temperature,train velocity,and droplet diameter—on the amount and morphology of ice were systematically investigated.The results show that ice accumulation intensifies with increasing liquid water content decreasing ambient temperature,and rising train speed.In contrast,larger droplet diameters reduce the overall ice mass but promote localized accretion on major structural elements.This behavior arises because larger droplets,with greater inertia,are less susceptible to entrainment by airflow into the pantograph's base region.During extended operation,substantial ice buildup develops on the pantograph head and upper and lower arms,severely impairing current collection from the overhead line and hindering the pantograph's lifting and lowering motions.展开更多
The increase in aerodynamic drag brings high energy consumption,which is a critical issue in the development of high-speed trains.Inspired by the excellent hydrodynamic characteristics of fish movement in nature,a two...The increase in aerodynamic drag brings high energy consumption,which is a critical issue in the development of high-speed trains.Inspired by the excellent hydrodynamic characteristics of fish movement in nature,a two-dimensional numerical simulation method based on spring-smoothing model and adaptive mesh technology was utilized to explore the effects of different fishtail structures and two flexible motion modes(Eel mode and Lunate-tail mode)on the wake of high-speed trains,and to assess their potential for aerodynamic drag reduction.Results indicate that the biomimetic fishtail successfully suppresses the alternating shedding of vortices in the wake,and induces the aerodynamic drag fluctuation period to align with the fishtail oscillation period.The fishtail length,oscillation mode,and frequency have a significant impact on the wake flow and aerodynamic drag of the train.Among these,a 1850 mm Eel fishtail with parameters ofλ=1 and T=8 s achieves the optimal drag reduction effect,with drag reduction rates of 39.12%and 26.00%for the tail car and the entire train,respectively.These findings provide a theoretical basis for the design of new low-resistance railway trains,promoting the sustainable development of rail transit towards goals of high-speed and energy-efficient.展开更多
基金Project(U2034211)supported by the National Natural Science Foundation of ChinaProject(20232ACE01013)supported by the Major Scientific and Technological Research and Development Special Project of Jiangxi Province,China。
文摘The safe driving and operation of trains is a necessary condition for ensuring the safe operation of trains.In particular,heavy-haul trains are characterized by the difficulty in driving and operation.Considering the uncertainties in train driving and operation,this paper analyzes the relationship between the safety of heavy-haul electric locomotive hauled trains and driving and operation.It studies the auxiliary intelligent driving safety operation control methods.Through K-means to identify the characteristics of drivers'driving manipulation,the hidden Markov model adaptively adjusts the train driving and operation sequence,and conducts auxiliary driving reconstruction for heavy-haul locomotive driving and operation.Based on the train running curve and the locomotive traction/braking characteristics,it smoothly controls the exertion of the traction/braking force of heavy-haul locomotives,thereby optimizing the driving safety control of heavy-haul trains in the vehicle-environment-track system.Finally,the train operation simulation and optimized driving verification are carried out by simulating some track sections.The results show that the proposed method can correct and pre-optimize driving operations,improving the smoothness of heavy-haul trains by approximately 10%.It verifies the effectiveness of the proposed train assisted driving control reconstruction method,facilitating the smooth and safe operation of heavy-haul trains.
基金financially supported by the Swedish Transport Administration(Trafikverket)through the“Excellence Area 4”and FOI-BBT program(Grant Nos.BBT-2019-022 and BBT-TRV 2024/132497).
文摘Railway noise barriers are an essential piece of infrastructure for reducing noise propagation.However,these barriers experience aerodynamic loads generated by high-speed trains,leading to dynamic effects that may compromise their fatigue capacity.The most common structural design for railway noise barriers consists of vertical configurations of posts and panels.However,there have been few dynamic analyses of steel post/wood panel noise barriers under train-induced aerodynamic loads.This study used dynamic finite element analysis to assess the dynamic behavior of such noise barriers.Analysis of a 40-m-long noise barrier model and a triangular simplified load model,the latter of which effectively represented the detailed aerodynamic load,were first used to establish the model and input of the moving load during dynamic simulation.Then,the effects of different parameters on the dynamic response of the noise barrier were evaluated,including the damping ratio,the profile of the steel post,the span length of the panel,the barrier height,and the train speed.Gray relational analysis indicated that barrier height exhibited the highest correlations with the dynamic responses,followed by train speed,post profile,span length,and damping ratio.A reduction in the natural frequency and an increase in the train speed result in a higher peak response and more pronounced fluctuations between the nose and tail waves.The dynamic amplification factor(DAF)was found to be related to both the natural frequency and train speed.A model was proposed showing that the DAF significantly increases as the square of the natural frequency decreases and the cube of the train speed rises.
基金supported by the National Natural Science Foundation of China(12372049)Fundamental Research Funds for the Central Universities(2682023ZTPY036)Research and Development Project of JDD For HTS Maglev Transportation System(JDDKYCF2024002).
文摘High-speed maglev trains(HSMTs)can run at high running speeds due to their unique design.The pressure waves that these trains generate while passing each other are therefore very intense,and can even have safety implications.In order to reduce the transient impact of such waves,the standard k-ε turbulence model is used in this work to assess the effect of railway spacing on the aerodynamic loads,pressure and surrounding flow field of 600 km/h maglev trains passing each other in open air.The sliding mesh technique is used to determine the relative motion between the considered trains.The results show that the surface pressure is approximately linearly correlated with the square of the speed while the amplitude of the pressure wave on the train surface,side force,and rolling moment all have negative exponential relationships with the railway spacing.
基金Project(2020YFA0710902)supported by the National Key Research and Development Program of ChinaProject(12172308)supported by the National Natural Science Foundation of ChinaProject(2025RVL-QY-T24)supported by the Independent Project of State Key Laboratory of Rail Transit Vehicle System,China。
文摘Tunnel-induced noise amplification has become a major constraint for high-speed trains.This study employs a 1/10 scale three-coach high-speed train model,using the improved delayed detached eddy simulation(IDDES)method coupled with the perturbed convective wave model to investigate the unsteady flow evolution,aerodynamic noise source distribution,and near-field acoustic characteristics of high-speed trains under open-air and tunnel conditions.The results show that the blocking effect of the tunnel wall enhances flow compression,increases local velocity,and aggravates flow disturbances and pressure fluctuations near the pantograph and tail car.In the tunnel,the total sound source energy reaches 1.14×10^(12)N^(2)/s^(2),5.26 times higher than in open air,with significant increases in the tail car,bogies,and pantograph.Bogie noise concentrates in the 50 to 1000 Hz range,while pantograph noise dominates from 1500 to 2500 Hz.Tunnel conditions further enhance peak distributions in the low and medium frequency bands.Although pressure disturbances on the train surface are mainly dominated by hydrodynamic effects,the radiated acoustic energy of the sound pressure levels on the roof and side surfaces is amplified by 33.3 and 22.6 times,far exceeding hydrodynamic energy amplification factors of 8.6 and 6.3.The study reveals coupled flow and acoustic mechanisms in tunnels,supporting noise reduction design for high-speed trains.
文摘Indian Railways have been the largest people moving transport infrastructure in India.Over the years the systems and trains have been upgraded resulting in both better passenger amenities and reduction in travel time.The newest addition is the Vande Bharat Express,a semi-high-speed train that was introduced in India in 2019.The train currently runs between 10 routes and has brought significant changes to India’s railway network.This article explores the introduction of Vande Bharat Express trains in India and its effects on the country’s interstation time-space shrinkage using cartographic techniques.The cartographic techniques like stepwise multidimensional scaling and interpolation using the distance cartogram plugin in QGIS are mainly used for generating the time-space maps for various speeds.The limitations of these techniques and the methods to overcome those limitations are also explored in this article.
基金supported by the Fundamental Research Funds for the Central Universities(No.2024JBZX027)the National Natural Science Foundation of China(No.52375078).
文摘High-Speed Trains (HSTs) have emerged as a mainstream mode of transportation in China, owing to their exceptional safety and efficiency. Ensuring the reliable operation of HSTs is of paramount economic and societal importance. As critical rotating mechanical components of the transmission system, bearings make their fault diagnosis a topic of extensive attention. This paper provides a systematic review of image encoding-based bearing fault diagnosis methods tailored to the condition monitoring of HSTs. First, it categorizes the image encoding techniques applied in the field of bearing fault diagnosis. Then, a review of state-of-the-art studies has been presented, encompassing both monomodal image conversion and multimodal image fusion approaches. Finally, it highlights current challenges and proposes future research directions to advance intelligent fault diagnosis in HSTs, aiming to provide a valuable reference for researchers and engineers in the field of intelligent operation and maintenance.
基金Project(2022YFB2603400)supported by the National Key Research and Development Program,China。
文摘This paper aims to explore the influence of different noise barrier heights on the sound source generation mechanisms of higher-speed trains(400 km/h)using a combination of delayed detached eddy simulation(DDES)and Ffowcs Williams-Hawkings(FW-H)equations.Four cases are investigated and compared,i.e.1)no barrier,2)2.3 m,3)3.3 m,and 4)4.3 m single-side barriers on a bridge.Numerical results show that the presence of noise barriers causes an increase in sound source intensity ranging from 2.1 to 2.8 dB(A).However,the relationship between the barrier height and the increase in sound source intensity varies across different parts of the train.Compared with the head and front middle cars,the boundary layer is thicker around the rear-middle and tail car areas.A thick boundary layer introduces the influence of the crash wall,causing asymmetry and increases in sound source intensity.This is due to the deceleration region formed between the crash wall and the rail surface,as well as the acceleration region formed by the contraction of the flow channel in the noise barrier,both of which influence the sound source's characteristics.In addition,higher barriers exacerbate asymmetry and increases in sound source intensity.
基金Projects(52372369,52302447,52388102)supported by the National Natural Science Foundation of ChinaProjects(2022YFB4301201-02,2023YFB4302502-02)supported by the National Key R&D Program of China。
文摘Irregularities in the track and uneven forces acting on the train can cause shifts in the position of the superconducting magnetic levitation train relative to the track during operation.These shifts lead to asymmetries in the flow field structure on both sides of the narrow suspension gap,resulting in instability and deterioration of the train’s aerodynamic characteristics,significantly impacting its operational safety.In this study,we firstly validate the aerodynamic characteristics of the superconducting magnetic levitation system by developing a numerical simulation method based on wind tunnel test results.We then investigate the influence of lateral translation parameters on the train’s aerodynamic performance under conditions both with and without crosswinds.We aim to clarify the evolution mechanism of the flow field characteristics under the coupling effect between the train and the U-shaped track and to identify the most unfavorable operational parameters contributing to the deterioration of the train’s aerodynamic properties.The findings show that,without crosswinds,a lateral translation of 30 mm causes a synchronous resonance phenomenon at the side and bottom gaps of the train-track coupling,leading to the worst aerodynamic performance.Under crosswind conditions,a lateral translation of 40 mm maximizes peak pressure fluctuations and average turbulent kinetic energy around the train,resulting in the poorest aerodynamic performance.This research provides theoretical support for enhancing the operational stability of superconducting magnetic levitation trains.
文摘High-speed railway holds a pivotal position in China's transportation system,closely intertwined with the production and daily lives of people.It serves as a critical carrier for fostering a new development paradigm,supporting high-quality growth,and building a modernized strong nation.Up to 2025,the high-speed railway operating mileage in China has exceeded 50000 km,ranking the first in the world and surpassing the combined total of high-speed railway operating mileage in all other countries.
基金supported in part by the National Natural Science Foundation of China(Grant Nos.62203246 and 62003127)Shandong Provincial Natural Science Foundation(Grant No.ZR2024QF041)the Natural Science Foundation of Hebei Province(Grant No.F2023202060)。
文摘Virtual coupling is a novel technology that enables trains to run closely together without physical connections through communication and automation systems.The paper addresses an adaptive polynomial approximation algorithm for the cooperative control of high-speed trains(HSTs)under virtual coupling.It aims to solve the cooperative tracking control problem of HST formation operations under various scenarios,including known and unknown parameters.To enable the HST formation system to achieve cooperative operation while ensuring an appropriate spacing distance,the tracking errors of displacement and speed throughout the entire operation converge to zero.The proposed control strategy focuses on adopting polynomial approximation to handle unknown parameters,which are estimated via adaptive laws.Additionally,the unknown parameters of the HSTs are estimated online through adaptive laws.Experimental results verify the effectiveness of this method.
基金Project(2020YFA0710903)supported by the National Key R&D Program of ChinaProject(2024JK2037)supported by the Key Research and Development Program of Hunan Province,China+1 种基金Project(52402458)supported by the National Natural Science Foundation of ChinaProjects(2025ZZTS0703,2025ZZTS0209)supported by the Fundamental Research Funds for the Central Universities,China。
文摘The influence of train height on aerodynamic characteristics of high-speed train(HST)is significant in crosswind environments.This study employed the improved delayed detached eddy simulation(IDDES)turbulence model to analyze the aerodynamic characteristics of trains with three different heights under a crosswind of 20 m/s.The numerical model was validated through comparison with wind tunnel experimental data.A comprehensive analysis was conducted on the characteristics of the flow field around trains,surface pressure distribution,and aerodynamic loads for trains with different heights.Results indicate that the side force coefficient increased by up to 61.54%with an increase in train height from 3.89 to 4.19 m.Compared with the 3.89 m case,the roll moment coefficient on the head,middle,and tail cars for 4.19 m cases increased by 18.11%,24.78%and 34.23%,respectively.The increase in train height widens the impact width of the leading car’s front vortex on the leeward side and intensifies the helical shedding and coupling interactions of two vortices in the wake,leading to an increase in the intensity and extent of wake flow in both vertical and longitudinal directions.Additionally,the increase in height shifted the flow separation point on the leeward side,moving vortices farther from the train,expanding the back-flow region,and intensifying Reynolds stress and turbulent fluctuations on the leeward side,which adversely impacted train stability and safety.The research findings can provide a reference for the design of train configurations and the assessment of dynamic performance in crosswind environments.
基金supported by the National Natural Science Foundation of China(Nos.52232011 and 52272324)the National Natural Science Foundation of Sichuan Province(No.2022NSFSC0397).
文摘Arrival headway,the minimum time interval between two trains that consecutively stop in the same railway yard,significantly influences overall railway capacity and becomes a bottleneck in large high-speed railway yards.This occurs because the leading train slows considerably along the long receiving route to the yard;while,the following train continues at top speed,creating a substantial spatial and temporal interval between them.This paper proposes a speed profile intervention(SPI)approach to reduce arrival headway.By setting appropriate speed limits in specific block sections for each train,the following train decelerates in advance,thereby shortening the interval with its predecessor.We first study the impact of speed values and locations on arrival headway theoretically,then validate our findings through a multi-agent simulation approach to quantitatively investigate the relationship between headway and SPI parameters.Simulation experiments using real-world data from the Beijing–Shanghai high-speed railway demonstrate that the SPI approach can significantly reduce arrival headway without any infrastructure modifications.To mitigate potential side effects on travel time associated with this approach,we perform an analysis that involves setting appropriate speed limit values and selecting strategic locations for their implementation.
基金supported by the National Natural Science Foundation of China(52222217,52388102,52372435)the Major Science and TechnologyProject of China Energy(GJNY-22-7)
文摘Virtual coupling(VC) is an emerging technology for addressing the shortage of rail transportation capacity. As a crucial enabling technology, the VC-specific acquisition of train information, especially train following distance(TFD), is underdeveloped.In this paper, a novel method is proposed to acquire real-time TFD by analyzing the vibration response of the front and following trains, during which only onboard accelerometers and speedometers are required. In contrast to the traditional arts of train positioning, this method targets a relative position between two adjacent trains in VC operation, rather than the global positions of the trains. For this purpose, an adaptive system containing three strategies is designed to cope with possible adverse factors in train operation. A vehicle dynamics simulation of a heavy-haul railway is implemented for the evaluation of feasibility and performance. Furthermore, a validation is conducted using a set of data measured from in-service Chinese high-speed trains. The results indicate the method achieves satisfactory estimation accuracy using both simulated and actual data. It has favorable adaptability to various uncertainties possibly encountered in train operation. Additionally, the method is preliminarily proven to adapt to different locomotive types and even different rail transportation modes. In general, such a method with good performance, low-cost, and easy implementation is promising to apply.
基金Projects(52372402,U2568224)supported by the National Natural Science Foundation of China。
文摘With increasingly stringent requirements for the airtightness of high-speed train bodies,determining appropriate airtightness levels has become critically important.To calculate the airtightness of high-speed train bodies more accurately,based on one-dimensional isentropic flow theory,this study derives cabin pressure calculation models for both positive and negative pressure conditions during static airtightness tests of high-speed train bodies.Since the flow coefficient,which is closely related to the leakage characteristics of the carriage,is influenced by multiple factors including operating pressure conditions(positive/negative),leakage path cross-sectional shape,and size,a flow coefficient calibration method is proposed to achieve high-precision and efficient calibration of the flow coefficient for trains with varying leakage properties.This method generates a series of flow coefficient values for circular and square cross-sectional shapes under both positive and negative pressure conditions across various cross-sectional areas.Furthermore,functional relationships between flow coefficient and leakage path area under positive/negative pressure are established through curve fitting.Using these functional relationships and the cabin pressure calculation model,the pressure variation curves for a static airtightness test are simulated.Specifically,for circular cross-sectional shapes,the theoretical curves under positive and negative pressure conditions exhibited R^(2) values of 0.9936 and 0.9931,respectively,when compared to experimental data,and for square cross-sectional shapes,the corresponding R^(2) values are 0.9928 and 0.9932,validating the accuracy of the proposed theoretical model.The proposed theoretical model effectively evaluates the airtightness of high-speed train bodies with varying performance levels during static airtightness tests,providing a robust theoretical reference for optimizing high-speed train airtightness design.
基金Project(2020YFA0710903)supported by the National Key Research and Development Program of ChinaProject(2025ZZTS0623)supported by the Graduate Student Independent Innovation Project of Central South University,ChinaProject(202406370145)supported by the China Scholarship Council。
文摘The stability of high-speed trains under crosswind conditions has become a key consideration in aerodynamic design.As running speeds continue to increase and car body weight decreases,crosswinds pose a greater risk to train safety,significantly lowering the critical wind velocity.Therefore,developing strategies to enhance crosswind stability is essential.This study focuses on the leeward region adjacent to the train body,where separated flows with large vortices generate significant negative surface pressure.Enhancing this negative pressure distribution is proposed as a potential method to improve a train’s resistance to overturning.To achieve this,winglets are installed on the leeward side as a flow control measure,and their effects at different deflection angles are evaluated.The influence of five deflection angles on the leeward-side flow field and aerodynamic loads is analyzed,considering the head,middle,and tail cars.Results indicate that a deflection angle of 90°optimally reduces the overall overturning moment by 27.6%compared to the baseline model in a three-car configuration.These findings highlight that optimizing the winglet deflection angle to approximately 90°can significantly enhance a train’s resistance to overturning,offering valuable insights for aerodynamic optimization in strong wind conditions.
基金supported by the Guangxi Science and Technology Major Program of China(Nos.AA23073019 and AA24263074)the National Natural Science Foundation of China(No.52265004)+7 种基金the Guangxi Natural Science Fund for Distinguished Young Scholars of China(No.2024JJG160014)the Innovation Project of Guangxi Graduate Education of China(No.YCSW2024119)the Open Fund of State Key Laboratory of Intelligent Manufacturing Equipment and Technology of China(No.IMETKF2025021)the Open Research Fund of State Key Laboratory of Precision Manufacturing for Extreme Service Performance-Central South University of China(No.Kfkt2023-06)the Open Fund of High-end Basic Component Innovation Station of China(No.KY01080030124001)the Open Fund for Academician Mao Ming's Workstation of China(No.XSJSFW-QNKXJ-202404-007)the Technology Innovation Platform Project of China Aviation Engine Group Corporation(No.CXPT-2023-044)the Open Fund for Innovation Workstation in the National Defense Science and Technology Innovation Special Zone(Xi'an Jiaotong University).
文摘The metamaterial based on external meshing gears(MEG)is designed based on the principle of external meshing gear transmission.Based on the meshing transmission principle of external meshing gears and planetary gear trains,the internal and external gear rings are designed.Based on the internal and external gear rings,the metamaterial based on inner and outer planetary gear trains(MIP)is designed to study the shear modulus,Young's modulus,and amplitude-frequency characteristics of the metamaterial based on gears at different angles.The effects of the number of planetary gears on the physical characteristics of the MIP are studied.The results show that the MEG can be continuously adjusted by adjusting the shear modulus and Young's modulus due to its meshing characteristics.With the same number of gears,the adjustment range of the MIP is larger than the adjustment range of the MEG.When the number of planetary gears increases,the adjustment range of the MIP decreases.Moreover,when the metamaterial based on gears rotates,the harmonic response changes with the change of the angle.
基金supported by the National Natural Science Foundation of China(No.52375160)the Natural Science Foundation of Hebei Province(No.2024105064),China.
文摘The structural safety of high-speed trains is significantly endangered by increasing operating speeds.The objective of this research was to investigate the evolution of the flow field in trains passing through a tunnel while there is a strong crosswind at the tunnel entrance and exit.Moreover,the effect of aerodynamic pressure waves on structural strength was analyzed to evaluate the safety of the carbody.In this study,we selected the improved delayed detached-eddy simulation(IDDES)method as a turbulence model.The mechanism of interaction among the train,tunnel,and crosswind was evaluated through a complex computational fluid dynamics(CFD)model,simulating high-speed trains moving through tunnels at various crosswind speeds.Additionally,the dynamic stress response of the carbody was calculated using a sequential coupling approach,where integral aerodynamic forces were applied as substitutes for direct CFD pressure loads.We assessed the effect of aerodynamic loads on the dynamic stresses of the carbody at different crosswind velocities(0,10,15,and 20 m/s).The results indicate that crosswinds exert a substantial influence on the fluid structure surrounding the train.Consequently,the aerodynamic forces contribute significantly to potential damage to the carbody,posing increased safety risks for high-speed trains.
基金Projects(52302447,52388102)supported by the National Natural Science Foundation of China。
文摘Considering passenger trains'key role in remote regions,this study employed machine vision technology to monitor five posture parameters of the second car of a conventional passenger train,aiming to investigate the influence of windbreaks and crosswinds along railways on the operating postures of conventional passenger trains.The study found that when passing through the anti-wind tunnel with holes,the amplitudes of posture parameters were smaller than those of other windbreaks,demonstrating the superior performance of this windbreak in maintaining posture stability compared to others.In tunnel sections,larger amplitudes of these parameters were observed for the tail car than the head car,while the opposite occurred in non-tunnel sections.Notably,during tunnel transit,their amplitudes did not increase monotonically with speed but peaked at a specific speed that most adversely affected the operating posture.These conclusions have a great significance for improving operating safety under crosswinds.
基金Natural Science Foundation of Shandong Province(Grant No.ZR2022ME180)the National Natural Science Foundation of China(Grant No.51705267).
文摘High-speed trains operating in freezing rain are highly susceptible to severe ice accretion in the pantograph region,which compromises both power transmission efficiency and dynamic performance.To elucidate the underlying mechanisms of this phenomenon,an Euler-Euler multiphase flow model was employed to simulate droplet impingement and collection on the pantograph surface,while a glaze-ice formation model incorporating wall film dynamics was used to capture the subsequent growth of ice.The effects of key parameters—including liquid water content,ambient temperature,train velocity,and droplet diameter—on the amount and morphology of ice were systematically investigated.The results show that ice accumulation intensifies with increasing liquid water content decreasing ambient temperature,and rising train speed.In contrast,larger droplet diameters reduce the overall ice mass but promote localized accretion on major structural elements.This behavior arises because larger droplets,with greater inertia,are less susceptible to entrainment by airflow into the pantograph's base region.During extended operation,substantial ice buildup develops on the pantograph head and upper and lower arms,severely impairing current collection from the overhead line and hindering the pantograph's lifting and lowering motions.
基金Project(2025A1515011803)supported by the Guangdong Basic and Applied Basic Research Foundation,ChinaProject(2023JC01020)supported by the Jiangmen Basic and Theoretical Science Research Plan,China。
文摘The increase in aerodynamic drag brings high energy consumption,which is a critical issue in the development of high-speed trains.Inspired by the excellent hydrodynamic characteristics of fish movement in nature,a two-dimensional numerical simulation method based on spring-smoothing model and adaptive mesh technology was utilized to explore the effects of different fishtail structures and two flexible motion modes(Eel mode and Lunate-tail mode)on the wake of high-speed trains,and to assess their potential for aerodynamic drag reduction.Results indicate that the biomimetic fishtail successfully suppresses the alternating shedding of vortices in the wake,and induces the aerodynamic drag fluctuation period to align with the fishtail oscillation period.The fishtail length,oscillation mode,and frequency have a significant impact on the wake flow and aerodynamic drag of the train.Among these,a 1850 mm Eel fishtail with parameters ofλ=1 and T=8 s achieves the optimal drag reduction effect,with drag reduction rates of 39.12%and 26.00%for the tail car and the entire train,respectively.These findings provide a theoretical basis for the design of new low-resistance railway trains,promoting the sustainable development of rail transit towards goals of high-speed and energy-efficient.
