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
The dynamic performance of high-speed trains is significantly influenced by sudden changes in aerodynamic loads(ADLs)when exiting a tunnel in a windy environment.Focusing on a double-track tunnel under construction in...The dynamic performance of high-speed trains is significantly influenced by sudden changes in aerodynamic loads(ADLs)when exiting a tunnel in a windy environment.Focusing on a double-track tunnel under construction in a mountain railway,we established an aerodynamic model involving a train exiting the tunnel,and verified it in the Fluent environment.Overset mesh technology was adopted to characterize the train’s movement.The flow field involving the train,tunnel,and crosswinds was simulated using the Reynolds-averaged turbulence model.Then,we built a comprehensive train-track coupled dynamic model considering the influences of ADLs,to investigate the vehicles’dynamic responses.The aerodynamics and dynamic behaviors of the train when affected by crosswinds with different velocities and directions are analyzed and discussed.The results show that the near-wall side crosswind leads to sharper variations in ADLs than the far-wall side crosswind.The leading vehicle suffers from more severe ADLs than other vehicles,which worsens the wheel-rail interaction and causes low-frequency vibration of the car body.When the crosswind velocity exceeds 20 m/s,significant wheel-rail impacts occur,and the running safety of the train worsens rapidly.展开更多
The interaction between the airflow and train influences the aerodynamic characteristics and dynamic performance of high-speed trains.This study focused on the fluid-solid coupling effect of airflow and HST,and propos...The interaction between the airflow and train influences the aerodynamic characteristics and dynamic performance of high-speed trains.This study focused on the fluid-solid coupling effect of airflow and HST,and proposed a co-simulation(CS)approach between computational fluid dynamics and multi-body dynamics.Firstly,the aerodynamic model was developed by employing overset mesh technology and the finite volume method,and the detailed train-track coupled dynamic model was established.Then the User Data Protocol was adopted to build data communication channels.Moreover,the proposed CS method was validated by comparison with a reported field test result.Finally,a case study of the HST exiting a tunnel subjected to crosswind was conducted to compare differences between CS and offline simulation(OS)methods.In terms of the presented case,the changing trends of aerodynamic forces and car-body displacements calculated by the two methods were similar.Differences mainly lie in aerodynamic moments and transient wheel-rail impacts.Maximum pitching and yawing moments on the head vehicle in the two methods differ by 21.1 kN∙m and 29.6 kN∙m,respectively.And wheel-rail impacts caused by sudden changes in aerodynamic loads are significantly severer in CS.Wheel-rail safety indices obtained by CS are slightly greater than those by OS.This research proposes a CS method for aerodynamic characteristics and dynamic performance of the HST in complex scenarios,which has superiority in computational efficiency and stability.展开更多
Purpose–This paper aims to analyze the transverse vibration characteristics of the high speed train window glass when passing through tunnel.Design/methodology/approach–The lateral vibration acceleration response of...Purpose–This paper aims to analyze the transverse vibration characteristics of the high speed train window glass when passing through tunnel.Design/methodology/approach–The lateral vibration acceleration response of glass chamber of high-speed train CR400BF-A on Beijing-Chengdu high-speed railway was tested at different speeds through the tunnel entrance,exit,tunnel interior,Tunnel Group and rendezvous time in the tunnel,the lateral distribution characteristics of vibration frequency and vibration power amplification coefficient of glass of high-speed train were analyzed.Findings–The results show that:The vibration of the high-speed train glass increases significantly during the tunnel,and the amplitude of vibration acceleration in the tunnel is significantly higher than outside the tunnel as the travel speed increases;the amplitude of lateral vibration acceleration of the glass of a high-speed train does not vary with changes in tunnel length and is not affected by the aerodynamic effects of the tunnel when traveling inside the tunnel,but its vibrations create noticeable fluctuations during variations when encountering oncoming traffic;The vibration characteristics of the high-speed train glass are forced harmonic vibrations,the excitation frequency does not vary with travel speed and travel position changes inside and outside the tunnel.The lateral vibration acceleration of the glass of a high-speed train is applied vertically and uniformly to the glass surface as an“inertial force”and creates a cyclic bending vibration stress that can easily lead to fatigue damage.Originality/value–The research results provide guidance for the prevention of glass failure in high-speed trains.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
Ventilation systems are critical for improving the cabin environment in high-speed trains,and their interest has increased significantly.However,whether air supply non-verticality deteriorates the cabin air environmen...Ventilation systems are critical for improving the cabin environment in high-speed trains,and their interest has increased significantly.However,whether air supply non-verticality deteriorates the cabin air environment,and the flow mechanism behind it and the degree of deterioration are not known.This study first analyzes the interaction between deflection angle and cabin flow field characteristics and ventilation performance.The results revealed that the interior temperature and pollutant concentration decreased slightly with increasing deflection angle,but resulted in significant deterioration of thermal comfort and air quality.This is evidenced by an increase in both draught rate and non-uniformity coefficient,an increase in the number of measurement points that do not satisfy the micro-wind speed and temperature difference requirements by about 5% and 15%,respectively,and an increase in longitudinal penetration of pollutants by a factor of about 5 and the appearance of locking regions at the ends of cabin.The results also show that changing the deflection pattern only affects the region of deterioration and does not essentially improve this deterioration.This study can provide reference and help for the ventilation design of high-speed trains.展开更多
Purpose–Regarding that Ultraviolet radiation,pollutant adsorption,and environmental changes may be the main reasons for the aging and yellowing on windshield rubber in high-speed trains,countermeasures are proposed t...Purpose–Regarding that Ultraviolet radiation,pollutant adsorption,and environmental changes may be the main reasons for the aging and yellowing on windshield rubber in high-speed trains,countermeasures are proposed to solve the aging and yellowing of windshield rubber and reduce the adverse effects caused by rubber yellowing.Design/methodology/approach–Scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS)were used to test the yellowed windshield rubber.Aging tests,including UVaging,natural aging and salt spray aging,were conducted to analyze the effects of aging on the windshield rubber.Different cleaning agents were selected to soak the windshield rubber,and the quality,hardness,and surface appearance of the rubber samples were tested.Findings–After UV aging,antioxidants migrated to the surface of the windshield rubber,but due to oxidation failure,they could not capture free radicals,leading to continued oxidation reactions within the material and resulting in yellowing of the rubber in a short period of time.Originality/value–Cleaning agents have a minimal impact on windshield rubber,UV aging has the greatest impact and natural aging is a gradual and slow deterioration process.Through daily deep cleaning and maintenance with protective agents at regular intervals,the deterioration of windshield rubber yellowing in high-speed trains can be effectively suppressed.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
Typically,seat or floor acceleration is used to evaluate the ride comfort of a high-speed train.However,the dynamic performance of the human body significantly differs from that of the floor.Therefore,using the car bo...Typically,seat or floor acceleration is used to evaluate the ride comfort of a high-speed train.However,the dynamic performance of the human body significantly differs from that of the floor.Therefore,using the car body floor and seat accelerations to calculate the ride comfort index of a high-speed train may not reflect the true feelings of passengers.In this study,a 3D human-seat-vehicle-track coupling model was established to investigate the ride comfort of highspeed train passengers.The seated human model,which considers the longitudinal,lateral,vertical,pitching,yawing,and rolling motions,comprises the head,upper torso,lower torso,pelvis,thighs,and shanks.The model parameters were determined using multi-axis excitation measurement data based on a genetic algorithm.Subsequently,the applicability of the small-angle assumption and natural modes of the human model is analyzed.Using the coupling system model,the vibration characteristics of the human-seat interaction surface were analyzed.The ride comfort of the high-speed train and human body dynamic performance were analyzed under normal conditions,track geometric irregularities and train meeting conditions.The results showed that the passenger seats in the front and rear rows adjacent to the window had a higher acceleration value than the others.The human backrest and seat pad connection points have higher vibration amplitudes than the car body floor in the human-sensitive frequency range,indicating that using the acceleration values on the floor may underestimate the discomfort of passengers.The ride comfort of high-speed trains diminishes in the presence of track geometric irregularities and when trains pass each other.When the excitation frequency of track geometry irregularities approached the natural frequency of the human-seat-vehicle system,ride comfort in high-speed trains decreased significantly.Moreover,using seat acceleration to evaluate passenger ride comfort overlooks the vibration characteristics of the human body.The transient aerodynamic force generated when the train meets can cause a larger car body roll and lateral motion at 2 Hz,which,in turn,decreases the passenger ride comfort.This study presents a detailed human-seat-vehicle-track coupling system that can reflect a passenger’s dynamic performance under complex operating conditions.展开更多
Purpose–High-speed turnouts are more complex in structure and thus may cause abnormal vibration of highspeed train car body,affecting driving safety and passenger riding experience.Therefore,it is necessary to analyz...Purpose–High-speed turnouts are more complex in structure and thus may cause abnormal vibration of highspeed train car body,affecting driving safety and passenger riding experience.Therefore,it is necessary to analyze the data characteristics of continuous hunting of high-speed trains passing through turnouts and propose a diagnostic method for engineering applications.Design/methodology/approach–First,Complete Ensemble Empirical Mode Decomposition with Adaptive Noise(CEEMDAN)is performed to determine the first characteristic component of the car body’s lateral acceleration.Then,the Short-Time Fourier Transform(STFT)is performed to calculate the marginal spectra.Finally,the presence of a continuous hunting problem is determined based on the results of the comparison calculations and diagnostic thresholds.To improve computational efficiency,permutation entropy(PE)is used as a fast indicator to identify turnouts with potential problems.Findings–Under continuous hunting conditions,the PE is less than 0.90;the ratio of the maximum peak value of the signal component to the original signal peak value exceeded 0.7,and there is an energy band in the STFT time-frequency map,which corresponds to a frequency distribution range of 1–2 Hz.Originality/value–The research results have revealed the lateral vibration characteristics of the high-speed train’s car body during continuous hunting when passing through turnouts.On this basis,an effective diagnostic method has been proposed.With a focus on practical engineering applications,a rapid screening index for identifying potential issues has been proposed,significantly enhancing the efficiency of diagnostic processes.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
The pantograph area is a critical source of aerodynamic noise in high-speed trains,generating noise both directly and through its cavity,a factor that warrants considerable attention.One effective method for reducing ...The pantograph area is a critical source of aerodynamic noise in high-speed trains,generating noise both directly and through its cavity,a factor that warrants considerable attention.One effective method for reducing aerodynamic noise within the pantograph cavity involves the introduction of a jet at the leading edge of the cavity.This study investigates the mechanisms driving cavity aerodynamic noise under varying jet velocities,using Improved Delayed Detached Eddy Simulation(IDDES)and Ffowcs Williams-Hawkings(FW-H)equations.The numerical simulations reveal that an increase in jet velocity results in a higher elevation of the shear layer above the cavity.This elevation,in turn,diminishes the interaction area between the vortices produced by jet shedding and the trailing edge of the cavity wall.Consequently,the amplitude of pressure pulsations on the cavity surface is reduced,leading to a decrease in radiated far-field noise.Specifically,simulations conducted with a jet velocity of 111.11 m/s indicate a remarkable noise reduction of approximately 4 dB attributable to this mechanism.To further enhance noise mitigation,alterations to the inclination angles of the cavity’s front and rear walls are also explored.The findings demonstrate that,at a constant jet velocity,such modifications significantly diminish pressure pulsations at the intersection of the rear wall and cavity floor,optimizing overall noise reduction and achieving a maximum reduction of approximately 6 dB.展开更多
Purpose-With the rapid advancement of China’s high-speed rail network,the density of train operations is on the rise.To address the challenge of shortening train tracking intervals while enhancing transportation effi...Purpose-With the rapid advancement of China’s high-speed rail network,the density of train operations is on the rise.To address the challenge of shortening train tracking intervals while enhancing transportation efficiency,the multi-objective dynamic optimization of the train operation process has emerged as a critical issue.Design/methodology/approach-Train dynamic model is established by analyzing the force of the train in the process of tracing operation.The train tracing operation model is established according to the dynamic mechanical model of the train tracking process,and the dynamic optimization analysis is carried out with comfort,energy saving and punctuality as optimization objectives.To achieve multi-objective dynamic optimization,a novel train tracking operation calculation method is proposed,utilizing the improved grey wolf optimization algorithm(MOGWO).The proposed method is simulated and verified based on the train characteristics and line data of CR400AF electric multiple units.Findings-The simulation results prove that the optimized MOGWO algorithm can be computed quickly during train tracks,the optimum results can be given within 5s and the algorithm can converge effectively in different optimization target directions.The optimized speed profile of the MOGWO algorithm is smoother and more stable and meets the target requirements of energy saving,punctuality and comfort while maximally respecting the speed limit profile.Originality/value-The MOGWO train tracking interval optimization method enhances the tracking process while ensuring a safe tracking interval.This approach enables the trailing train to operate more comfortably,energy-efficiently and punctually,aligning with passenger needs and industry trends.The method offers valuable insights for optimizing the high-speed train tracking process.展开更多
Purpose–The safety and reliability of high-speed trains rely on the structural integrity of their components and the dynamic performance of the entire vehicle system.This paper aims to define and substantiate the ass...Purpose–The safety and reliability of high-speed trains rely on the structural integrity of their components and the dynamic performance of the entire vehicle system.This paper aims to define and substantiate the assessment of the structural integrity and dynamical integrity of high-speed trains in both theory and practice.The key principles and approacheswill be proposed,and their applications to high-speed trains in Chinawill be presented.Design/methodology/approach–First,the structural integrity and dynamical integrity of high-speed trains are defined,and their relationship is introduced.Then,the principles for assessing the structural integrity of structural and dynamical components are presented and practical examples of gearboxes and dampers are provided.Finally,the principles and approaches for assessing the dynamical integrity of highspeed trains are presented and a novel operational assessment method is further presented.Findings–Vehicle system dynamics is the core of the proposed framework that provides the loads and vibrations on train components and the dynamic performance of the entire vehicle system.For assessing the structural integrity of structural components,an open-loop analysis considering both normal and abnormal vehicle conditions is needed.For assessing the structural integrity of dynamical components,a closed-loop analysis involving the influence of wear and degradation on vehicle system dynamics is needed.The analysis of vehicle system dynamics should follow the principles of complete objects,conditions and indices.Numerical,experimental and operational approaches should be combined to achieve effective assessments.Originality/value–The practical applications demonstrate that assessing the structural integrity and dynamical integrity of high-speed trains can support better control of critical defects,better lifespan management of train components and better maintenance decision-making for high-speed trains.展开更多
The simulation of the ground effect has always been a technical difficulty in wind tunnel tests of high-speed trains.In this paper,large eddy simulation and the curl acoustic integral equation were used to simulate th...The simulation of the ground effect has always been a technical difficulty in wind tunnel tests of high-speed trains.In this paper,large eddy simulation and the curl acoustic integral equation were used to simulate the flow-acoustic field results of high-speed trains under four ground simulation systems(GSSs):“moving ground+rotating wheel”,“stationary ground+rotating wheel”,“moving ground+stationary wheel”,and“stationary ground+stationary wheel”.By comparing the fluid-acoustic field results of the four GSSs,the influence laws of different GSSs on the flow field structure,aero-acoustic source,and far-field radiation noise characteristics were investigated,providing guidance for the acoustic wind tunnel testing of high-speed trains.The calculation results of the aerodynamic noise of a 350 km/h high-speed train show that the moving ground and rotating wheel affect mainly the aero-acoustic performance under the train bottom.The influence of the rotating wheel on the equivalent sound source power of the whole vehicle was not more than 5%,but that of the moving ground slip was more than 15%.The average influence of the rotating wheel on the sound pressure level radiated by the whole vehicle was 0.3 dBA,while that of the moving ground was 1.8 dBA.展开更多
The complex structure of the bottom of a high-speed train is an important source of train aerodynamic drag.Thus,improving the bottom structure is of great significance to reduce the aerodynamic drag of the train.In th...The complex structure of the bottom of a high-speed train is an important source of train aerodynamic drag.Thus,improving the bottom structure is of great significance to reduce the aerodynamic drag of the train.In this study,computational fluid dynamics(CFD)based on three-dimensional steady incompressible Reynolds-average Naiver-Stokes(RANS)equations and Realizable k-εturbulence model were utilized for numerical simulations.Inspired by the concept of streamlined design and the idea of bottom flow field control,this study iteratively designed the bogies in a streamlined shape and combined them with the bottom deflectors to investigate the joint drag reduction mechanism.Three models,i.e.,single-bogie model,simplified train model,and eight-car high-speed train model,were created and their aerodynamic characteristics were analyzed.The results show that the single-bogie model with streamlined design shows a noticeable drag reduction,whose power bogie and trailer bogie experience 13.92%and 7.63%drag reduction,respectively.The range of positive pressure area on the bogie is reduced.The aerodynamic drag can be further reduced to 15.01%by installing both the streamlined bogie and the deflector on the simplified train model.When the streamlined bogies and deflectors are used on the eight-car model together,the total drag reduction rate reaches 2.90%.Therefore,the proposed aerodynamic kit for the high-speed train bottom is capable to improve the flow structure around the bogie regions,reduce the bottom flow velocity,and narrow the scope of the train’s influence on the surrounding environment,achieving the appreciable reduction of aerodynamic drag.This paper can provide a new idea for the drag reduction of high-speed trains.展开更多
Hunting stability is an important performance criterion in railway vehicles.This study proposes an incorporation of a bio-inspired limb-like structure(LLS)-based nonlinear damping into the motor suspension system for ...Hunting stability is an important performance criterion in railway vehicles.This study proposes an incorporation of a bio-inspired limb-like structure(LLS)-based nonlinear damping into the motor suspension system for traction units to improve the nonlinear critical speed and hunting stability of high-speed trains(HSTs).Initially,a vibration transmission analysis is conducted on a HST vehicle and a metro vehicle that suffered from hunting motion to explore the effect of different motor suspension systems from on-track tests.Subsequently,a simplified lateral dynamics model of an HST bogie is established to investigate the influence of the motor suspension on the bogie hunting behavior.The bifurcation analysis is applied to optimize the motor suspension parameters for high critical speed.Then,the nonlinear damping of the bio-inspired LLS,which has a positive correlation with the relative displacement,can further improve the modal damping of hunting motion and nonlinear critical speed compared with the linear motor suspension system.Furthermore,a comprehensive numerical model of a high-speed train,considering all nonlinearities,is established to investigate the influence of different types of motor suspension.The simulation results are well consistent with the theoretical analysis.The benefits of employing nonlinear damping of the bio-inspired LLS into the motor suspension of HSTs to enhance bogie hunting stability are thoroughly validated.展开更多
To improve the passive safety of high-speed trains,it is very important to understand the mechanism of head injury in high-speed train collisions.In this study,the head injury mechanisms of occupants in high-speed tra...To improve the passive safety of high-speed trains,it is very important to understand the mechanism of head injury in high-speed train collisions.In this study,the head injury mechanisms of occupants in high-speed train rear-end collisions were investigated based on the occupant-seat coupling model,which included a dummy representing the Chinese 50th percentile adult male.The typical injury responses in terms of skull fractures,brain contusions,and diffuse axonal injury(DAI)were analyzed.Meanwhile,the influences of collision speed and seat parameters on head injury response were examined.The simulation results indicate that the skull fractures primarily occur at the skull base region due to excessive neck extension,while the brain contusions and DAI result from the relative displacement of different brain regions.The increase in collision speed will promote the probability of skull fracture,brain contusion,and DAI.Seat design modifications,such as reduced seat spacing,increased seat backrest angles,and selecting the appropriate cushion angle(76°)and friction coefficient(0.15),can effectively mitigate probably occupant's head injury.展开更多
Considering the high-temperature distribution along a tunnel in a high-altitude area,the effects of high geotemperature and high altitude on the pressure wave of trains running in long tunnels were investigated using ...Considering the high-temperature distribution along a tunnel in a high-altitude area,the effects of high geotemperature and high altitude on the pressure wave of trains running in long tunnels were investigated using a 3D,compressible,unsteady turbulence model.To reduce the simulation cost and reflect the pressure wave characteristics in long tunnels,a representative tunnel length was first determined for simulation.The simulation results indicated that compared to the condition of a normal ambient-temperature tunnel,when trains go through a high geotemperature tunnel,the distribution of the minimum pressure(Pmin)along the tunnel moves to the tunnel entrance.The pressure amplitudes on the tunnel and train decrease integrally,with maximum reductions of 7.9%in the maximum pressure(Pmax)and 44%in Pmin on the tunnel,and 4.6%in P_(max)and 12%in Pmin on the train.When trains meet in high geotemperature tunnels,the distributions of P_(max)and Pmin along the tunnel change.The pressure amplitudes decrease integrally,with maximum reductions of 13.8%in P_(max)and 36.9%in Pmin on the tunnel,and 7.1%in P_(max)and 15.6%in Pmin on the train.The pressure difference between the two sides of the train during the intersection decreases by 15.9%.As the altitude rises,when trains cross and meet in tunnels,the waveforms of pressures on the tunnel and train and the pressure difference between the two sides of the train remain unchanged,and the peaks decrease linearly.展开更多
The streamlined nose length(SNL)plays a crucial role in determining the aerodynamic performance of high-speed trains.An appropriate SNL can not only effectively reduce the magnitude of aerodynamic drag and lift forces...The streamlined nose length(SNL)plays a crucial role in determining the aerodynamic performance of high-speed trains.An appropriate SNL can not only effectively reduce the magnitude of aerodynamic drag and lift forces,but also improve the performance of the high-speed train in tunnel passing and crosswind circumstances.In this study,a numerical simulation of the aerodynamic performance of high-speed trains at a speed of 400 km/h,with varying SNLs,is conducted using the k-ωshear stress transport(SST)turbulence model.The different SNLs include 6.0,7.0,8.0,9.0,9.8,12.0,15.0,and 18.0 m.In order to validate the accuracy of the numerical simulation,its results are compared with wind tunnel test data obtained from the literature.Numerical simulation is carried out using compressible and incompressible gases to determine the effect of gas compressibility on results.The impact of SNL on the aerodynamic performance of the trains is analyzed in terms of aerodynamic forces,velocity,and pressure distributions.In comparison to the original train,the train with a 6.0 m SNL experienced a 10.8%increase in overall aerodynamic resistance.Additionally,the lift forces on the head and tail cars increased by 35.7%and 75.5%,respectively.On the other hand,the train with an 18.0 m SNL exhibited a 16.5%decrease in aerodynamic drag.Furthermore,the lift forces on the head and tail cars decreased by 21.9%and 49.7%,respectively.The aerodynamic drag force of the entire train varies linearly with the SNL,while the aerodynamic lift of the tail car follows a quadratic function in relation to the SNL.展开更多
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National Natural Science Foundation of China(No.52388102)New Cornerstone Science Foundation through the Xplorer Prize.
文摘The dynamic performance of high-speed trains is significantly influenced by sudden changes in aerodynamic loads(ADLs)when exiting a tunnel in a windy environment.Focusing on a double-track tunnel under construction in a mountain railway,we established an aerodynamic model involving a train exiting the tunnel,and verified it in the Fluent environment.Overset mesh technology was adopted to characterize the train’s movement.The flow field involving the train,tunnel,and crosswinds was simulated using the Reynolds-averaged turbulence model.Then,we built a comprehensive train-track coupled dynamic model considering the influences of ADLs,to investigate the vehicles’dynamic responses.The aerodynamics and dynamic behaviors of the train when affected by crosswinds with different velocities and directions are analyzed and discussed.The results show that the near-wall side crosswind leads to sharper variations in ADLs than the far-wall side crosswind.The leading vehicle suffers from more severe ADLs than other vehicles,which worsens the wheel-rail interaction and causes low-frequency vibration of the car body.When the crosswind velocity exceeds 20 m/s,significant wheel-rail impacts occur,and the running safety of the train worsens rapidly.
基金Supported by the Sichuan Science and Technology Program(Grant No.2023ZDZX0008)the National Natural Science Foundation of China(Grant No.52388102)the New Cornerstone Science Foundation through the XPLORER PRIZE.
文摘The interaction between the airflow and train influences the aerodynamic characteristics and dynamic performance of high-speed trains.This study focused on the fluid-solid coupling effect of airflow and HST,and proposed a co-simulation(CS)approach between computational fluid dynamics and multi-body dynamics.Firstly,the aerodynamic model was developed by employing overset mesh technology and the finite volume method,and the detailed train-track coupled dynamic model was established.Then the User Data Protocol was adopted to build data communication channels.Moreover,the proposed CS method was validated by comparison with a reported field test result.Finally,a case study of the HST exiting a tunnel subjected to crosswind was conducted to compare differences between CS and offline simulation(OS)methods.In terms of the presented case,the changing trends of aerodynamic forces and car-body displacements calculated by the two methods were similar.Differences mainly lie in aerodynamic moments and transient wheel-rail impacts.Maximum pitching and yawing moments on the head vehicle in the two methods differ by 21.1 kN∙m and 29.6 kN∙m,respectively.And wheel-rail impacts caused by sudden changes in aerodynamic loads are significantly severer in CS.Wheel-rail safety indices obtained by CS are slightly greater than those by OS.This research proposes a CS method for aerodynamic characteristics and dynamic performance of the HST in complex scenarios,which has superiority in computational efficiency and stability.
基金supported by grants from the National Key Research and Development Program(Grant Nos.2023YFC3806205).
文摘Purpose–This paper aims to analyze the transverse vibration characteristics of the high speed train window glass when passing through tunnel.Design/methodology/approach–The lateral vibration acceleration response of glass chamber of high-speed train CR400BF-A on Beijing-Chengdu high-speed railway was tested at different speeds through the tunnel entrance,exit,tunnel interior,Tunnel Group and rendezvous time in the tunnel,the lateral distribution characteristics of vibration frequency and vibration power amplification coefficient of glass of high-speed train were analyzed.Findings–The results show that:The vibration of the high-speed train glass increases significantly during the tunnel,and the amplitude of vibration acceleration in the tunnel is significantly higher than outside the tunnel as the travel speed increases;the amplitude of lateral vibration acceleration of the glass of a high-speed train does not vary with changes in tunnel length and is not affected by the aerodynamic effects of the tunnel when traveling inside the tunnel,but its vibrations create noticeable fluctuations during variations when encountering oncoming traffic;The vibration characteristics of the high-speed train glass are forced harmonic vibrations,the excitation frequency does not vary with travel speed and travel position changes inside and outside the tunnel.The lateral vibration acceleration of the glass of a high-speed train is applied vertically and uniformly to the glass surface as an“inertial force”and creates a cyclic bending vibration stress that can easily lead to fatigue damage.Originality/value–The research results provide guidance for the prevention of glass failure in high-speed trains.
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(12372049)supported by the National Natural Science Foundation of ChinaProject(2682023ZTPY036)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2023TPL-T06)supported by the Independent Project of State Key Laboratory of Rail Transit Vehicle System,China。
文摘Ventilation systems are critical for improving the cabin environment in high-speed trains,and their interest has increased significantly.However,whether air supply non-verticality deteriorates the cabin air environment,and the flow mechanism behind it and the degree of deterioration are not known.This study first analyzes the interaction between deflection angle and cabin flow field characteristics and ventilation performance.The results revealed that the interior temperature and pollutant concentration decreased slightly with increasing deflection angle,but resulted in significant deterioration of thermal comfort and air quality.This is evidenced by an increase in both draught rate and non-uniformity coefficient,an increase in the number of measurement points that do not satisfy the micro-wind speed and temperature difference requirements by about 5% and 15%,respectively,and an increase in longitudinal penetration of pollutants by a factor of about 5 and the appearance of locking regions at the ends of cabin.The results also show that changing the deflection pattern only affects the region of deterioration and does not essentially improve this deterioration.This study can provide reference and help for the ventilation design of high-speed trains.
文摘Purpose–Regarding that Ultraviolet radiation,pollutant adsorption,and environmental changes may be the main reasons for the aging and yellowing on windshield rubber in high-speed trains,countermeasures are proposed to solve the aging and yellowing of windshield rubber and reduce the adverse effects caused by rubber yellowing.Design/methodology/approach–Scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS)were used to test the yellowed windshield rubber.Aging tests,including UVaging,natural aging and salt spray aging,were conducted to analyze the effects of aging on the windshield rubber.Different cleaning agents were selected to soak the windshield rubber,and the quality,hardness,and surface appearance of the rubber samples were tested.Findings–After UV aging,antioxidants migrated to the surface of the windshield rubber,but due to oxidation failure,they could not capture free radicals,leading to continued oxidation reactions within the material and resulting in yellowing of the rubber in a short period of time.Originality/value–Cleaning agents have a minimal impact on windshield rubber,UV aging has the greatest impact and natural aging is a gradual and slow deterioration process.Through daily deep cleaning and maintenance with protective agents at regular intervals,the deterioration of windshield rubber yellowing in high-speed trains can be effectively suppressed.
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Supported by National Natural Science Foundation of China(Grant No.U1934203)Research and Development Project of Science and Technology of China Railway Corporation(Grant No.P2023T002)。
文摘Typically,seat or floor acceleration is used to evaluate the ride comfort of a high-speed train.However,the dynamic performance of the human body significantly differs from that of the floor.Therefore,using the car body floor and seat accelerations to calculate the ride comfort index of a high-speed train may not reflect the true feelings of passengers.In this study,a 3D human-seat-vehicle-track coupling model was established to investigate the ride comfort of highspeed train passengers.The seated human model,which considers the longitudinal,lateral,vertical,pitching,yawing,and rolling motions,comprises the head,upper torso,lower torso,pelvis,thighs,and shanks.The model parameters were determined using multi-axis excitation measurement data based on a genetic algorithm.Subsequently,the applicability of the small-angle assumption and natural modes of the human model is analyzed.Using the coupling system model,the vibration characteristics of the human-seat interaction surface were analyzed.The ride comfort of the high-speed train and human body dynamic performance were analyzed under normal conditions,track geometric irregularities and train meeting conditions.The results showed that the passenger seats in the front and rear rows adjacent to the window had a higher acceleration value than the others.The human backrest and seat pad connection points have higher vibration amplitudes than the car body floor in the human-sensitive frequency range,indicating that using the acceleration values on the floor may underestimate the discomfort of passengers.The ride comfort of high-speed trains diminishes in the presence of track geometric irregularities and when trains pass each other.When the excitation frequency of track geometry irregularities approached the natural frequency of the human-seat-vehicle system,ride comfort in high-speed trains decreased significantly.Moreover,using seat acceleration to evaluate passenger ride comfort overlooks the vibration characteristics of the human body.The transient aerodynamic force generated when the train meets can cause a larger car body roll and lateral motion at 2 Hz,which,in turn,decreases the passenger ride comfort.This study presents a detailed human-seat-vehicle-track coupling system that can reflect a passenger’s dynamic performance under complex operating conditions.
基金support from the funds of National Natural Science Foundation of China(52308473)China Academy of Railway Science Corporation Limited(2022YJ192)are gratefully acknowledged。
文摘Purpose–High-speed turnouts are more complex in structure and thus may cause abnormal vibration of highspeed train car body,affecting driving safety and passenger riding experience.Therefore,it is necessary to analyze the data characteristics of continuous hunting of high-speed trains passing through turnouts and propose a diagnostic method for engineering applications.Design/methodology/approach–First,Complete Ensemble Empirical Mode Decomposition with Adaptive Noise(CEEMDAN)is performed to determine the first characteristic component of the car body’s lateral acceleration.Then,the Short-Time Fourier Transform(STFT)is performed to calculate the marginal spectra.Finally,the presence of a continuous hunting problem is determined based on the results of the comparison calculations and diagnostic thresholds.To improve computational efficiency,permutation entropy(PE)is used as a fast indicator to identify turnouts with potential problems.Findings–Under continuous hunting conditions,the PE is less than 0.90;the ratio of the maximum peak value of the signal component to the original signal peak value exceeded 0.7,and there is an energy band in the STFT time-frequency map,which corresponds to a frequency distribution range of 1–2 Hz.Originality/value–The research results have revealed the lateral vibration characteristics of the high-speed train’s car body during continuous hunting when passing through turnouts.On this basis,an effective diagnostic method has been proposed.With a focus on practical engineering applications,a rapid screening index for identifying potential issues has been proposed,significantly enhancing the efficiency of diagnostic processes.
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 National Natural Science Foundation of China(12172308).
文摘The pantograph area is a critical source of aerodynamic noise in high-speed trains,generating noise both directly and through its cavity,a factor that warrants considerable attention.One effective method for reducing aerodynamic noise within the pantograph cavity involves the introduction of a jet at the leading edge of the cavity.This study investigates the mechanisms driving cavity aerodynamic noise under varying jet velocities,using Improved Delayed Detached Eddy Simulation(IDDES)and Ffowcs Williams-Hawkings(FW-H)equations.The numerical simulations reveal that an increase in jet velocity results in a higher elevation of the shear layer above the cavity.This elevation,in turn,diminishes the interaction area between the vortices produced by jet shedding and the trailing edge of the cavity wall.Consequently,the amplitude of pressure pulsations on the cavity surface is reduced,leading to a decrease in radiated far-field noise.Specifically,simulations conducted with a jet velocity of 111.11 m/s indicate a remarkable noise reduction of approximately 4 dB attributable to this mechanism.To further enhance noise mitigation,alterations to the inclination angles of the cavity’s front and rear walls are also explored.The findings demonstrate that,at a constant jet velocity,such modifications significantly diminish pressure pulsations at the intersection of the rear wall and cavity floor,optimizing overall noise reduction and achieving a maximum reduction of approximately 6 dB.
基金funded by the China Academy of Railway Sciences Corporation Limited Scientific Research Project(No:2023YJ080).
文摘Purpose-With the rapid advancement of China’s high-speed rail network,the density of train operations is on the rise.To address the challenge of shortening train tracking intervals while enhancing transportation efficiency,the multi-objective dynamic optimization of the train operation process has emerged as a critical issue.Design/methodology/approach-Train dynamic model is established by analyzing the force of the train in the process of tracing operation.The train tracing operation model is established according to the dynamic mechanical model of the train tracking process,and the dynamic optimization analysis is carried out with comfort,energy saving and punctuality as optimization objectives.To achieve multi-objective dynamic optimization,a novel train tracking operation calculation method is proposed,utilizing the improved grey wolf optimization algorithm(MOGWO).The proposed method is simulated and verified based on the train characteristics and line data of CR400AF electric multiple units.Findings-The simulation results prove that the optimized MOGWO algorithm can be computed quickly during train tracks,the optimum results can be given within 5s and the algorithm can converge effectively in different optimization target directions.The optimized speed profile of the MOGWO algorithm is smoother and more stable and meets the target requirements of energy saving,punctuality and comfort while maximally respecting the speed limit profile.Originality/value-The MOGWO train tracking interval optimization method enhances the tracking process while ensuring a safe tracking interval.This approach enables the trailing train to operate more comfortably,energy-efficiently and punctually,aligning with passenger needs and industry trends.The method offers valuable insights for optimizing the high-speed train tracking process.
基金This work was partly funded by the National Key R&D Project of China(2021YFB3400704)China State Railway Group(K2022J004 and N2023J011)China Railway Chengdu Group(CJ23018).
文摘Purpose–The safety and reliability of high-speed trains rely on the structural integrity of their components and the dynamic performance of the entire vehicle system.This paper aims to define and substantiate the assessment of the structural integrity and dynamical integrity of high-speed trains in both theory and practice.The key principles and approacheswill be proposed,and their applications to high-speed trains in Chinawill be presented.Design/methodology/approach–First,the structural integrity and dynamical integrity of high-speed trains are defined,and their relationship is introduced.Then,the principles for assessing the structural integrity of structural and dynamical components are presented and practical examples of gearboxes and dampers are provided.Finally,the principles and approaches for assessing the dynamical integrity of highspeed trains are presented and a novel operational assessment method is further presented.Findings–Vehicle system dynamics is the core of the proposed framework that provides the loads and vibrations on train components and the dynamic performance of the entire vehicle system.For assessing the structural integrity of structural components,an open-loop analysis considering both normal and abnormal vehicle conditions is needed.For assessing the structural integrity of dynamical components,a closed-loop analysis involving the influence of wear and degradation on vehicle system dynamics is needed.The analysis of vehicle system dynamics should follow the principles of complete objects,conditions and indices.Numerical,experimental and operational approaches should be combined to achieve effective assessments.Originality/value–The practical applications demonstrate that assessing the structural integrity and dynamical integrity of high-speed trains can support better control of critical defects,better lifespan management of train components and better maintenance decision-making for high-speed trains.
基金This work is supported by the National Natural Science Foundation of China(No.52272363)the Foundation of the Key Laboratory of Aerodynamic Noise Control(No.ANCL20200302),China.
文摘The simulation of the ground effect has always been a technical difficulty in wind tunnel tests of high-speed trains.In this paper,large eddy simulation and the curl acoustic integral equation were used to simulate the flow-acoustic field results of high-speed trains under four ground simulation systems(GSSs):“moving ground+rotating wheel”,“stationary ground+rotating wheel”,“moving ground+stationary wheel”,and“stationary ground+stationary wheel”.By comparing the fluid-acoustic field results of the four GSSs,the influence laws of different GSSs on the flow field structure,aero-acoustic source,and far-field radiation noise characteristics were investigated,providing guidance for the acoustic wind tunnel testing of high-speed trains.The calculation results of the aerodynamic noise of a 350 km/h high-speed train show that the moving ground and rotating wheel affect mainly the aero-acoustic performance under the train bottom.The influence of the rotating wheel on the equivalent sound source power of the whole vehicle was not more than 5%,but that of the moving ground slip was more than 15%.The average influence of the rotating wheel on the sound pressure level radiated by the whole vehicle was 0.3 dBA,while that of the moving ground was 1.8 dBA.
基金Project(2020YFA0710901)supported by the National Key Research and Development Program of ChinaProject(2023JJ30643)supported by the Natural Science Foundation of Hunan Province,China+1 种基金Project(12372204)supported by the National Natural Science Foundation of ChinaProject(2022ZZTS0725)supported by the Self-exploration and Innovation Project for Postgraduates of Central South University,China。
文摘The complex structure of the bottom of a high-speed train is an important source of train aerodynamic drag.Thus,improving the bottom structure is of great significance to reduce the aerodynamic drag of the train.In this study,computational fluid dynamics(CFD)based on three-dimensional steady incompressible Reynolds-average Naiver-Stokes(RANS)equations and Realizable k-εturbulence model were utilized for numerical simulations.Inspired by the concept of streamlined design and the idea of bottom flow field control,this study iteratively designed the bogies in a streamlined shape and combined them with the bottom deflectors to investigate the joint drag reduction mechanism.Three models,i.e.,single-bogie model,simplified train model,and eight-car high-speed train model,were created and their aerodynamic characteristics were analyzed.The results show that the single-bogie model with streamlined design shows a noticeable drag reduction,whose power bogie and trailer bogie experience 13.92%and 7.63%drag reduction,respectively.The range of positive pressure area on the bogie is reduced.The aerodynamic drag can be further reduced to 15.01%by installing both the streamlined bogie and the deflector on the simplified train model.When the streamlined bogies and deflectors are used on the eight-car model together,the total drag reduction rate reaches 2.90%.Therefore,the proposed aerodynamic kit for the high-speed train bottom is capable to improve the flow structure around the bogie regions,reduce the bottom flow velocity,and narrow the scope of the train’s influence on the surrounding environment,achieving the appreciable reduction of aerodynamic drag.This paper can provide a new idea for the drag reduction of high-speed trains.
基金the National Natural Science Foundation of China (Nos. 52388102, 52072317 and U2268210)the State Key Laboratory of Rail Transit Vehicle System (No. 2024RVL-T12)
文摘Hunting stability is an important performance criterion in railway vehicles.This study proposes an incorporation of a bio-inspired limb-like structure(LLS)-based nonlinear damping into the motor suspension system for traction units to improve the nonlinear critical speed and hunting stability of high-speed trains(HSTs).Initially,a vibration transmission analysis is conducted on a HST vehicle and a metro vehicle that suffered from hunting motion to explore the effect of different motor suspension systems from on-track tests.Subsequently,a simplified lateral dynamics model of an HST bogie is established to investigate the influence of the motor suspension on the bogie hunting behavior.The bifurcation analysis is applied to optimize the motor suspension parameters for high critical speed.Then,the nonlinear damping of the bio-inspired LLS,which has a positive correlation with the relative displacement,can further improve the modal damping of hunting motion and nonlinear critical speed compared with the linear motor suspension system.Furthermore,a comprehensive numerical model of a high-speed train,considering all nonlinearities,is established to investigate the influence of different types of motor suspension.The simulation results are well consistent with the theoretical analysis.The benefits of employing nonlinear damping of the bio-inspired LLS into the motor suspension of HSTs to enhance bogie hunting stability are thoroughly validated.
基金supported by the National Natural Science Foundation of China(Grant No.12122211)the Natural Science Foundation of Sichuan Province(Grant No.2022NSFSC0035)。
文摘To improve the passive safety of high-speed trains,it is very important to understand the mechanism of head injury in high-speed train collisions.In this study,the head injury mechanisms of occupants in high-speed train rear-end collisions were investigated based on the occupant-seat coupling model,which included a dummy representing the Chinese 50th percentile adult male.The typical injury responses in terms of skull fractures,brain contusions,and diffuse axonal injury(DAI)were analyzed.Meanwhile,the influences of collision speed and seat parameters on head injury response were examined.The simulation results indicate that the skull fractures primarily occur at the skull base region due to excessive neck extension,while the brain contusions and DAI result from the relative displacement of different brain regions.The increase in collision speed will promote the probability of skull fracture,brain contusion,and DAI.Seat design modifications,such as reduced seat spacing,increased seat backrest angles,and selecting the appropriate cushion angle(76°)and friction coefficient(0.15),can effectively mitigate probably occupant's head injury.
基金supported by the National Key Research and Development Program of China(No.2020YFA0710902)the National Natural Science Foundation of China(Nos.12122211 and 11772275).
文摘Considering the high-temperature distribution along a tunnel in a high-altitude area,the effects of high geotemperature and high altitude on the pressure wave of trains running in long tunnels were investigated using a 3D,compressible,unsteady turbulence model.To reduce the simulation cost and reflect the pressure wave characteristics in long tunnels,a representative tunnel length was first determined for simulation.The simulation results indicated that compared to the condition of a normal ambient-temperature tunnel,when trains go through a high geotemperature tunnel,the distribution of the minimum pressure(Pmin)along the tunnel moves to the tunnel entrance.The pressure amplitudes on the tunnel and train decrease integrally,with maximum reductions of 7.9%in the maximum pressure(Pmax)and 44%in Pmin on the tunnel,and 4.6%in P_(max)and 12%in Pmin on the train.When trains meet in high geotemperature tunnels,the distributions of P_(max)and Pmin along the tunnel change.The pressure amplitudes decrease integrally,with maximum reductions of 13.8%in P_(max)and 36.9%in Pmin on the tunnel,and 7.1%in P_(max)and 15.6%in Pmin on the train.The pressure difference between the two sides of the train during the intersection decreases by 15.9%.As the altitude rises,when trains cross and meet in tunnels,the waveforms of pressures on the tunnel and train and the pressure difference between the two sides of the train remain unchanged,and the peaks decrease linearly.
基金supported by the National Natural Science Foundation of China(No.12372049)the Sichuan Science and Technology Program(No.2023JDRC0062)+1 种基金the Independent Project of State Key Laboratory of Rail Transit Vehicle System(No.2023TPL-T06)the Fundamental Research Funds for the Central Universities,China(No.2682023ZTPY036).
文摘The streamlined nose length(SNL)plays a crucial role in determining the aerodynamic performance of high-speed trains.An appropriate SNL can not only effectively reduce the magnitude of aerodynamic drag and lift forces,but also improve the performance of the high-speed train in tunnel passing and crosswind circumstances.In this study,a numerical simulation of the aerodynamic performance of high-speed trains at a speed of 400 km/h,with varying SNLs,is conducted using the k-ωshear stress transport(SST)turbulence model.The different SNLs include 6.0,7.0,8.0,9.0,9.8,12.0,15.0,and 18.0 m.In order to validate the accuracy of the numerical simulation,its results are compared with wind tunnel test data obtained from the literature.Numerical simulation is carried out using compressible and incompressible gases to determine the effect of gas compressibility on results.The impact of SNL on the aerodynamic performance of the trains is analyzed in terms of aerodynamic forces,velocity,and pressure distributions.In comparison to the original train,the train with a 6.0 m SNL experienced a 10.8%increase in overall aerodynamic resistance.Additionally,the lift forces on the head and tail cars increased by 35.7%and 75.5%,respectively.On the other hand,the train with an 18.0 m SNL exhibited a 16.5%decrease in aerodynamic drag.Furthermore,the lift forces on the head and tail cars decreased by 21.9%and 49.7%,respectively.The aerodynamic drag force of the entire train varies linearly with the SNL,while the aerodynamic lift of the tail car follows a quadratic function in relation to the SNL.
