Vibration-based bearing fault diagnosis of high-speed trains:A literature review

Due to the advantages of comfort and safety,high-speed trains are gradually becoming the mainstream public transport in China.Since the operating speed and mileage of high-speed trains have achieved rapid growth,it is more and more urgent to ensure their reliability and safety.As an important component in the bogies of highspeed trains,the health state of the bearing directly affects the operational safety of the trains.It is therefore necessary to diagnoze the faults of bearings in the bogies of high-speed trains as early as possible.In this paper,the bearing fault diagnostic methods for high-speed trains have been systematically summarized with their challenges and perspectives.First,it briefly introduces the structure of bearings in the bogies as well as the fault characteristic frequencies.Then,a brief review of the research on vibration-based signal processing methods and machine learning methods has been provided.Finally,the challenges and future developments of vibrationbased bearing fault diagnostic methods for high-speed trains have been analyzed.

A study on aerodynamic noise characteristics of a high-speed maglev train with a speed of 600 km/h

Purpose–This study aims to explore the formation mechanism of aerodynamic noise of a high-speed maglev train and understand the characteristics of dipole and quadrupole sound sources of the maglev train at different speed levels.Design/methodology/approach–Based on large eddy simulation(LES)method and Kirchhoff–Ffowcs Williams and Hawkings(K-FWH)equations,the characteristics of dipole and quadrupole sound sources of maglev trains at different speed levels were simulated and analyzed by constructing reasonable penetrable integral surface.Findings–The spatial disturbance resulting from the separation of the boundary layer in the streamlined area of the tail car is the source of aerodynamic sound of the maglev train.The dipole sources of the train are mainly distributed around the radio terminals of the head and tail cars of the maglev train,the bottom of the arms of the streamlined parts of the head and tail cars and the nose tip area of the streamlined part of the tail car,and the quadrupole sources are mainly distributed in the wake area.When the train runs at three speed levels of 400,500 and 600 km$h1,respectively,the radiated energy of quadrupole source is 62.4%,63.3%and 71.7%,respectively,which exceeds that of dipole sources.Originality/value–This study can help understand the aerodynamic noise characteristics generated by the high-speed maglev train and provide a reference for the optimization design of its aerodynamic shape.

Three-dimensional strata movement around coal face of steeply dipping seam group

Steeply dipping seam group,which has complex occurrence conditions,be- longs to the steeply dipping seam.The research on the strata movement around the coal face not only improves safe production technology in practice,but also develops the min- ing theory.By using physical simulation experiments,numerical simulation and site test, the deformation,failure and movement of surrounding rock in longwall working face were analyzed.According to the analysis,characteristics of the seam group were formed which is different from the single seam.Asymmetry mechanics,sequential changes and imbal- ance of strata movement along the tendency working face were summarized.Furthermore the features of upper and lower seams were different.The mining of the lower seam in- duced more complex strata movement along the strike.Multi-section mining disturbed surrounding rocks in larger areas than the single section mining did,which had an impact on and dynamic loading function to the support when mining the lower seam,and pro- duced a great influence on the stability of support-rock system.

列车通过变截面长大海底隧道时的隧道内瞬变压力和列车风研究

在建造长大海底隧道时,为了加固隧道结构并节省成本,通常会改变隧道部分区段的截面面积,这将导致隧道内的空气动力学特性发生变化。本文通过对比变截面(VCS)隧道和常规(CCS)隧道,研究了突变截面对长隧道内压力瞬变和列车风的影响。数值模拟采用RNG k-ε湍流模型,通过动模型试验进行了验证。结果表明,越接近突变截面VCS隧道和CCS隧道内的正峰值压力之间的差异越大,在5.43 km处达到最大值7.63%。在两种隧道之间纵向列车风的差异最高达18.7%,但在其他两个方向上几乎相同。此外,突变截面对隧道不同区域的影响不相同。本研究对长大变截面隧道的参数设计和隧道内附属设施的布置具有参考价值。

弹性波传播对列车撞击动力学特性影响研究

在列车撞击动力学中,简化的刚体模型被广泛应用于研究列车耐撞性,以及进一步优化列车在冲击载荷下的能量分布。然而忽略弹性波传播对列车耐撞性能的影响尚不清楚。为了解决这一问题,本文建立了简化的一维弹性车体模型,并研究了弹性波传播对列车能量耗散以及动力学特性的影响。基于经典的弹性波传播理论,提出了一种密度及弹性模量缩比准则,使一维弹性车体的运动特性与其横截面积无关。讨论了弹性波传播速度对不同冲击速度下三节编组列车在冲击工况下的能量吸收、弹性能储存以及车体最终的等效平衡速度的影响。研究发现,当弹性波的传播速度约为3500 m/s时,一维弹性车体与实际列车模型的一致性最好。在初始冲击速度为10、15和20 m/s时,简化的一维弹性模型吸能量与实际列车模型相比误差仅为2.56%、1.84%和1.45%,而简化的刚性模型能量吸收量比实际列车模型高10.7%、12.4%和14.8%,刚性模型显著高估了列车的能量吸收量。我们的研究结果可以促进列车在碰撞条件下的耐撞性设计和优化。

一种用于高速列车受电弓区域气动减阻的新型鞘翅目仿生导流罩

受电弓区域是列车气动阻力的重要来源,其贡献率约为10%,是列车气动阻力的关键区域。因此,改善受电弓区压力分布成为减小列车气动阻力的潜在有效方法。基于鞘翅目昆虫的生物形态,提出了一种新型的仿生鞘翅目导流罩,将其安装在8节编组的高速列车受电弓区域,以实现该区域的空气流动平顺。建立了原始模型(模型Ⅰ)、带导流罩的受电弓Ⅰ(模型Ⅱ)、带导流罩的受电弓Ⅱ(模型Ⅲ)、带导流罩的受电弓Ⅰ和受电弓Ⅱ(模型Ⅳ)4个计算模型,探讨列车气动减阻机理,提高列车气动性能。结果表明,安装受电弓导流罩后,受在电弓区域的气动阻力显著减小。受电弓Ⅰ区域最大减阻达84.5%,受电弓Ⅱ区域最大减阻为25.0%。当受电弓Ⅰ区域和受电弓Ⅱ区域同时安装导流罩时,受电弓Ⅰ区和受电弓Ⅱ区总减阻可达49.6%。与没有导流罩的原始模型相比,受电弓区域的空气流动更顺畅,堵塞效应更小。但是,下游流速加快,冲击风挡区域,导致气动阻力增大。在受电弓Ⅰ区域或受电弓Ⅱ区域安装导流罩时,8节列车的总阻力分别降低了4.6%和1.8%,而在受电弓Ⅰ区域和受电弓Ⅱ区域同时安装导流罩时,列车的总阻力降低了6.3%。本文可为新一代高速列车的气动设计提供参考。

风洞试验中不同厚度挡风墙合理长度的数值研究

在风洞中,挡风墙的特性对列车的空气动力学特性有重要影响。利用改进的延迟分离涡模拟(IDDES)方法和剪切应力传输(SST)k-ω湍流模型,研究了不同挡风墙厚度下列车气动特性随挡风墙长度的变化。风洞试验结果用于侧滑角为30°时的验证。当挡风墙超过一定长度时,列车的空气动力载荷没有显著变化,可以认为达到了临界长度。通过拟合列车空气动力学系数与挡风墙长度之间的关系,确定了挡风墙的临界长度。挡风墙厚度与临界长度之间的关系满足二次函数y=-57.106x2+10.85x+28.822。当挡风墙厚度大于0.5 m(全尺寸)时,可通过将风洞试验中挡风墙的厚度代入上述函数来获得临界长度,以研究列车的空气动力学特性。

Numerical simulation of formaldehyde distribution characteristics in the high-speed train cabin

The global concern over indoor air pollution in public vehicles has grown significantly.With a focus on enhancing passengers’comfort and health,this study endeavors to investigate the distribution characteristics of formaldehyde within a high-speed train cabin by employing a computational fluid dynamics(CFD)model which is experimentally validated in a real cabin scenario.The research focuses on analyzing the impact of air supply modes,temperature,relative humidity,and fresh air change rate on the distribution and concentration of formaldehyde.The results demonstrate that the difference in average formaldehyde concentration between the two air supply modes is below 1.3%,but the top air supply mode leads to a higher accumulation of formaldehyde near the sidewalls,while the bottom air supply mode promotes a more uniform distribution of formaldehyde.Furthermore,the temperature,relative humidity,and fresh air change rate are the primary factors affecting formaldehyde concentration levels,but they have modest effects on formaldehyde’s distribution pattern within the cabin.As the temperature and relative humidity increase,the changes in formaldehyde concentrations in response to variations in these factors become more evident.Importantly,the formaldehyde concentration may surpass the standard limit of 0.10 mg/m^(3)if the fresh air change rate falls below 212 m^(3)/h.This research provides a systematic approach and referenceable results for exploring formaldehyde pollution in high-speed train cabins.

高速列车头车1位转向架区域的空气动力噪声特性

本文采用大涡模拟和FW-H声学类比的仿真方法对高速列车头车1位转向架气动发声主尺度进行了分析,获得了该区域气动噪声的发声机理。流场气动激励结果表明,转向架将转向架腔分隔为两个腔体,每个腔体内都形成了较大的环流,其流场脉动频谱呈现多峰离散特性。远场噪声结果表明,在55.56~97.22m/s的速度范围内,转向架区域的气动发声机理是相似的。空腔噪声是高速列车头车1位转向架区域的主要噪声机制,转向架的存在将转向架腔分成两个腔体,改变了该腔的发声模式。

转向架区域简化对高速列车气动性能的影响

为探究列车底部转向架区域结构对列车底部流场以及列车气动性能的影响,本文采用SST k-ω湍流模型对不同简化程度转向架、雷诺数Re=2.25×10^(6)下的三车编组高速列车周围流场进行仿真分析,并结合风洞试验结果验证数值方法的正确性。分析结果表明:与原始带转向架的列车模型相比,移除转向架并光顺列车车身的简化模型,可实现列车减阻38.2%;将转向架区域进行全包裹并光顺风挡区域,列车气动阻力减少30.3%;而当移除转向架并保留转向架腔外形时,列车气动阻力不减反增10.2%。因此,在进行高速列车气动外形减阻设计时,可考虑封闭转向架腔的方式,实现列车整车气动减阻。

隧道壁面瞬变压力及其对隧道结构安全的影响

本文采用三维数值方法分析了列车通过隧道引发的洞壁瞬变压力及其对隧道衬砌结构安全的影响。结果表明:单车通过隧道时,随着测点距离隧道入口距离的增加,隧道壁面压力迅速增加,在距隧道入口200 m位置达到最大;两列车在隧道内交会时,隧道壁面最大压力出现在隧道中部。列车以350 km/h速度单车通过70 m^(2)单线隧道、100 m^(2)双线隧道和两车在100 m^(2)双线隧道内交会时,隧道壁面最大峰值压力分别为−4544 Pa,−3137 Pa和−5909 Pa;在隧道气动载荷作用下,隧道衬砌上的轴向力分别仅为岩土压力的8%、5%和9%。若不考虑气动载荷对隧道衬砌裂纹和缺陷的影响,气动载荷对隧道衬砌静强度安全系数的影响不大。

铁路车辆吸能结构的研究进展及应用

随着吸能结构在学术界和工业界的应用达到前所未有的规模,关于列车耐撞性设计和结构优化最新进展的思考对于成功塑造未来的吸能结构就显得至关重要。实车冲击试验和数值仿真是目前研究铁路车辆耐撞性的主要方法。列车的端部碰撞变形区域一般可采用两种结构设计形式:承载式吸能结构设计形式和专有吸能结构设计形式,本文介绍的不同吸能结构可以适用于不同的铁路车辆,从而达到耐撞性和经济性之间的平衡。为了提升吸能结构能量耗散的能力,对于多级吸能系统的研究层出不穷,力求在现有吸能结构能量耗散能力达到极限时寻求突破。为了减少冲击伤害,乘员的自我保护姿势也被广泛研究。迄今为止开展了大量的吸能结构的研究,但针对吸能结构冲击过程的分析与预测所进行的研究较少,这也是未来吸能结构研究的诸多关键挑战之一。

高速列车转向架积雪的数值与试验研究

本文综述了降雪区域高速列车转向架积雪问题研究的现状。首先,通过回顾前人研究,调研了高速列车积雪问题产生的背景和近几十年来提出的应对措施。其次,介绍了中南大学高速列车研究中心关于积雪结冰问题的研究方法,包括针对连续相和两相流风洞试验的数值模拟研究平台和实验装置。在此基础上,提出了引导车体底部气流的有效防积雪流动控制方案及其对转向架安装区域积雪运动和累积的影响。最后,从工程应用的角度,提出了高速铁路积雪结冰问题尚待解决的问题与挑战和展望。

高速列车挡风玻璃雨水积聚与流动特性的数值模拟（英文）

本文建立了欧拉-拉格朗日粒子/流体膜/VOF耦合多相流模型。在此基础上,通过数值模拟的方法研究了两种类型挡风玻璃的雨水聚集和流动特性。结果表明,挡风玻璃表面形成了一层不均匀的水膜,凹面挡风玻璃表面存在雨水聚集现象,凸面挡风玻璃表面没有雨水聚集现象。当列车低速运行时,凹形挡风玻璃的平均液膜厚度大于凸形挡风玻璃。然而,在列车高速行驶的情况下,两者之间的差异较小。此外,存在使挡风玻璃流体膜流动方向发生改变的临界车速。当列车速度小于临界车速时,挡风玻璃下部流体膜和列车机头向下流动,超过临界车速时,整个挡风玻璃和列车机头上方流体膜向上流动。

不同风向角下一节半编组替代三车编组的风洞可行性研究

首先,在风洞中采用1:16.8的模型研究了不同风向角对市域动车组气动性能的影响;其次,采用压力扫描阀和六分度天平对1.5节和3节列车编组的市域动车组模型的头车车体压力分布和气动性能进行了测试;最后,分析了风向角对列车流线型头部压力分布和列车气动力的影响。实验结果表明:压力系数在主型线斜率最大处最小。当风向角为55°时,横风对车头横截面的侧向力系数和压力系数影响最大。在风洞实验中,若风向角在24.2°内,用1.5节车编组代替3节车编组有明显的空间优势。此外,升力系数C_(L)、横摇力矩系数C_(Mx)、侧向力系数C_(S)和阻力系数C_(D)的相对误差均在5.95%以内,实验精度满足要求。

一种对空气中复合材料层合椭圆壳声振分析的统一预测方法

提出了一种半解析法对空气中的复合材料层合椭圆壳进行振动声分析。采用变分法和分段技术建立动力学模型。采用基尔霍夫-亥姆霍兹积分公式计算了外部流场的声辐射。用傅立叶级数和切比雪夫正交多项式组合展开了包含位移和声压的变量。引入配置点构造声积分方程代数系统,这些点分布在切比雪夫多项式的根上,并用组合亥姆霍兹积分消除系统的非唯一解。给出了复合材料层合椭圆壳声辐射问题的数值算例,并给出了周向模态对复合材料层合椭圆壳声学结果的影响。研究了几何参数和材料参数对复合材料层合椭圆壳声辐射的影响。

Numerical study of the influence of dome shape on the unsteady aerodynamic performance of a high-speed train's pantograph subjected to crosswind

This study aims to investigate the unsteady aerodynamic performance of a high-speed train’s pantograph with respect to two different dome shapes and without dome under a20°yaw angle using a delayed detached eddy simulation method.Further,the influence of the dome shape on the simulation results is determined.The accuracy of the numerical method was validated by comparing a few of the numerical results with the wind tunnel test results,and high consistency was observed.An analysis of aerodynamic forces and flow structures around the pantograph was performed.The dome had significant influence on velocity field distribution surrounding the pantograph,particularly in the wake of flow region.Compared with the case where the dome was absent,vortex intensity around the pantograph increased after installing the dome.The existence of the bathtub-type dome resulted in greater flow field disturbance and vortex strength than the baffle-type dome.Moreover,the dome considerably affected time-averaged aerodynamic coefficients and their fluctuations,especially the bathtub-type dome.Additionally,the power spectral density of the unsteady aerodynamic coefficient of each pantograph component exhibited significant peaks and typical broadband distribution characteristics.

列车通过平地至路堑挡风墙过渡区域的动态行为及缓解措施

本文研究了大风环境下从平地至路堑的直角挡风墙过渡区域对列车空气动力学和系统动力学响应的影响,提出一种斜切过渡缓解措施来减小原始挡风墙过渡对列车气动和动力学性能的影响。结果表明,由于直角挡风墙过渡的影响,来流风场在线路内被分为两部分,一部分在平地位置引起强烈回流,另一部分在路堑位置引起强烈回流。因此,列车经过挡风墙过渡区域时受到了两次横向冲击。采用挡风墙斜切过渡后,头车侧向力系数、升力系数和倾覆力矩系数与原始挡风墙过渡相比,峰峰值分别下降了47%、40%和52%。对于车辆系统动力学响应参数的峰峰值,挡风墙斜切过渡相比原始过渡降幅均超过50%,其中原始挡风墙过渡和缓解措施下的列车动力学倾覆系数分别为0.75和0.3。

Effect of low operating temperature on the aerodynamic characteristics of a high-speed train

In this study,an improved delayed detached eddy simulation(IDDES)method based on the shear-stress transport(SST)k-ωturbulence model has been used to investigate the underbody flow characteristics of a high-speed train operating at lower temperatures with Reynolds number Re=1.85×10^(6).The accuracy of the numerical method has been validated by wind tunnel tests.The aerodynamic drag of the train,pressure distribution on the surface of the train,the flow around the vehicle,and the wake flow are compared for four temperature values:+15℃,0℃,−15℃,and−30℃.It was found that lower operating t emperatures significantly increased the aerodynamic drag force of the train.The drag overall at low temperatures increased by 5.3%(0℃),11.0%(−15℃),and 17.4%(−30℃),respectively,relative to the drag at+15℃.In addition,the low temperature e nhances the positive and negative pressures around and on the surface of the car body,raising the peak positive and negative pressure values in areas susceptible to impingement flow and to rapid changes in flow velocity.The range of train-induced winds around the car body is significantly reduced,the distribution area of vorticity moves backwards,and the airflow velocity in the bogie cavity is significantly increased.At the same time,the temperature causes a significant velocity reduction in the wake flow.It can be seen that the temperature reduction can seriously disturb the normal operation of the train while increasing the aerodynamic drag and energy consumption,and significantly interfering with the airflow characteristics around the car body.

Research progress on train operation safety in Xinjiang railway under wind environment

Railway lines in the Xinjiang wind area face severe wind disasters year-round,which seriously affects the safety and economy of the railway in China.Therefore,the wind characteristics and statistics of wind-induced accidents along the Xinjiang railway lines are presented and the basic research route for evaluating the train running safety under crosswinds and effective measures to improve the windproof performances of trains are proposed,which are meaningful to deal with wind-induced train accidents.Based on this research route,a series of numerical simulations are conducted to evaluate train safety and the corresponding measures are provided.The results show the following.The running safety of the train under crosswinds mainly depends on the aerodynamic loads acting on the train.The relationships between the safe speed limit and train type,the load weight,the embankment height,the road cutting depth,the railway line curve parameters,the yaw angle and other factors are obtained.The critical wind-vehicle speed relationship,as well as the engineering speed limit value under different running conditions,are determined.Large values of the aerodynamic and dynamic indices mainly appear in special locations,such as near earth-embankment-type windbreak walls,shallow cuttings and the transition sections between various types of windbreak walls.Measures such as increasing the height of the earth-embankment-type windbreak walls,adding wind barriers with reasonable heights in shallow cuttings and optimizing the design of different types of transition sections are proposed to significantly improve the safe speed limits of trains under crosswinds.