Simulation study on the influence of longitudinal dynamic force on extreme-long heavy-haul trains

Purpose–The objective of this study is to investigate the impact of longitudinal forces on extreme-long heavy-haul trains,providing new insights and methods for their design and operation,thereby enhancing safety,operational efficiency and track system design.Design/methodology/approach–A longitudinal dynamics simulation model of the super long heavy haul train was established and verified by the braking test data of 30,000 t heavy-haul combination train on the long and steep down grade of Daqing Line.The simulation model was used to analyze the influence of factors on the longitudinal force of super long heavy haul train.Findings–Under normal conditions,the formation length of extreme-long heavy-haul combined train has a small effect on the maximum longitudinal coupler force under full service braking and emergency braking on the straight line.The slope difference of the long and steep down grade has a great impact on the maximum longitudinal coupler force of the extreme-long heavy-haul trains.Under the condition that the longitudinal force does not exceed the safety limit of 2,250 kN under full service braking at the speed of 60 km/h the maximum allowable slope difference of long and steep down grade for 40,000 t super long heavy-haul combined trains is 13‰,and that of 100,000 t is only 5‰.Originality/value–The results will provide important theoretical basis and practical guidance for further improving the transportation efficiency and safety of extreme-long heavy-haul trains.

波浪作用下高速列车-轨道-桥梁系统耦合振动研究

为研究波浪作用对高速铁路跨海桥梁车-轨-桥系统耦合振动的影响,基于线性波浪理论和Morison方程模拟波浪荷载,采用分布力模式输入既有车-轨-桥系统耦合振动分析程序,提出波浪作用下的车-轨-桥系统耦合振动分析方法。以某高速铁路跨海斜拉桥为背景,研究波坡面效应、波浪重现期、车速对车-轨-桥系统动力响应的影响,并评估不同重现期波浪作用下过桥列车的走行性。结果表明:波坡面效应会使作用于不同单桩的波浪荷载初始相位不同,从而导致作用于群桩基础的波浪荷载合力不同;随着波浪重现期的增大,车-轨-桥系统的横向动力响应均增大,而竖向动力响应几乎不变;考虑波浪作用后,列车的行车安全性指标均随车速的增大而增大,波浪荷载会显著降低桥上列车的乘坐舒适性并增加桥上列车的脱轨风险。常遇波浪(10年重现期)和极端波浪(100年重现期)作用下列车的安全车速阈值分别为325 km/h和275 km/h。

Aerodynamic performance analysis of trains on slope topography under crosswinds

This work used the computational fluid dynamics method combined with full-scale train tests to analyze the train aerodynamic performance on special slope topography. Results show that with the increment in the slope gradient, the aerodynamic forces and moment increase sharply. Compared with the flat ground condition, the lateral force, lift force, and overturning moment of the train on the first line increase by 153.2%, 53.4% and 124.7%, respectively, under the slope gradient of 20°. However, with the increment of the windward side's depth, the windbreak effect is improved obviously. When the depth is equal to 10 m, compared with the 0 m, the lateral force, lift force and overturning moment of the train on the first line decrease by 70.9%, 77.0% and 70.6%,respectively. Through analyzing the influence of slope parameters on the aerodynamic performance of the train, the relationships among them are established. All these will provide a basic reference for enhancing train aerodynamic performances under different slope conditions and achieve reasonable train speeds for the operation safety in different wind environments.

Numerical investigation on the aerodynamic characteristics of high-speed train under turbulent crosswind

Increasing velocity combined with decreasing mass of modern highspeed trains poses a question about the influence of strong crosswinds on its aerodynamics. Strong crosswinds may affect the running stability of high speed trains via the amplified aerodynamic forces and moments. In this study, a simulation of turbulent crosswind flows over the leading and end cars of ICE2 highspeed train was performed at different yaw angles in static and moving ground case scenarios. Since the train aerodynamic problems are closely associated with the flows occurring around train, the flow around the train was considered as incompressible and was obtained by solving the incom pressible form of the unsteady Reynoldsaveraged Navier Stokes （RANS） equations combined with the realizable kepsilon turbulence model. Important aerodynamic coef ficients such as the side force and rolling moment coeffi cients were calculated for yaw angles ranging from 30° to 60° and compared with the results obtained from wind tunnel test. The dependence of the flow structure on yaw angle was also presented. The nature of the flow field and its structure depicted by contours of velocity magnitude and streamline patterns along the train＇s crosssection were presented for different yaw angles. In addition, the pressure coefficient around the circumference of the train at dif ferent locations along its length was computed for yaw angles of 30° and 60°, The computed aerodynamic coef ficient outcomes using the realizable kepsilon turbulencemodel were in good agreement with the wind tunnel data. Both the side force coefficient and rolling moment coeffi cients increase steadily with yaw angle till about 50° before starting to exhibit an asymptotic behavior. Contours of velocity magnitude were also computed at different cross sections of the train along its length for different yaw angles. The result showed that magnitude of rotating vortex in the lee ward side increased with increasing yaw angle, which leads to the creation of a lowpressure region in the lee ward side of the train causing high side force and roll moment. Generally, this study shows that unsteady CFD RANS methods combined with an appropriate turbulence model can present an important means of assessing the crucial aerodynamic forces and moments of a highspeed train under strong crosswind conditions.

Main Detrainment Height of Deep Convection Systems over the Tibetan Plateau and Its Southern Slope

Deep convection systems (DCSs) can rapidly lift water vapor and other pollutants from the lower troposphere to the upper troposphere and lower stratosphere. The main detrainment height determines the level to which the air parcel is lifted. We analyzed the main detrainment height over the Tibetan Plateau and its southern slope based on the CloudSat Cloud Profiling Radar 2B_GEOPROF dataset and the Aura Microwave Limb Sounder Level 2 cloud ice product onboard the Atrain constellation of Earth-observing satellites. It was found that the DCSs over the Tibetan Plateau and its southern slope have a higher main detrainment height (about 10-16 km) than other regions in the same latitude. The mean main detrainment heights are 12.9 and 13.3 km over the Tibetan Plateau and its southern slope, respectively. The cloud ice water path decreases by 16.8% after excluding the influences of DCSs, and the height with the maximum increase in cloud ice water content is located at 178 hPa (about 13 km). The main detrainment height and outflow horizontal range are higher and larger over the central and eastern Tibetan Plateau, the west of the southern slope, and the southeastern edge of the Tibetan Plateau than that over the northwestern Tibetan Plateau. The main detrainment height and outflow horizontal range are lower and broader at nighttime than during daytime.

基于SLOPE／W的汾离高速公路靳家庄1^#滑坡研究

汾(阳)-离(石)高速公路是青岛至银川国道主干线在山西境内的重要路段。文章以汾离高速公路靳家庄1#滑坡为研究对象,从岩性条件、地质构造及地下水等方面详细分析了滑坡的成因。应用基于刚体极限平衡理论的SLOPE/W程序,对滑坡的稳定性进行分析与计算。结果表明:该滑坡在天然状态下,整体处于稳定状态;在工程状态下,受水动力条件的变化以及人为活动的影响,易发生复活。为设计人员提供了参考。

大坡道长大隧道及隧道群环境下高速列车车内外压力波特性的实车试验研究

高速列车通过25‰单面坡隧道时,形成压力波和大气压两者耦合下的车内外压力变化特征,因此,有必要研究在隧道大气压持续变化下的高速列车通过大坡道隧道时的气动载荷和车内压力舒适性问题。采用实车试验的方法,获取动车组通过西成高铁西安北—汉中线路的列车车内外压力测试数据。研究结果表明:1)列车下坡通过25‰特长隧道时车外压力波动受隧道压力波与大气压的共同作用,整体呈上升的变化趋势;2)单面坡上坡和单面坡下坡隧道的长度由1541.2 m增大至8399.2 m时,列车车内外最大压力峰值越靠近隧道出口,单面坡隧道长度越长,列车车内外压力峰值越大;3)随着大坡道隧道长度的增大,列车头车和尾车的整车气密效率在不断减小,列车车内Δp/1 s、Δp/3 s、Δp/10 s和Δp/60 s在不断增大,相应的车内压力舒适性环境更恶劣,当列车通过长大坡道隧道群时,车内压力舒适性环境和列车车体的气密性能更差;4)与压力保护阀逻辑控制相比,压力保护阀全程关闭时列车车内压力和不同时间间隔下的最大压力变化量要更小,车内压力舒适性环境更优。

基于加权二部图的Slope One推荐算法

相对协同过滤算法,Slope One算法在执行速度上更加迅速,并且易于实现.但是算法没有考虑项目之间的推荐关系,故提出了一种基于加权二部图的Slope One推荐算法.利用加权二部图推荐算法计算项目之间的推荐程度,并用计算得到的项目之间的推荐程度对Slope One预测评分过程进行加权处理,由于二部图推荐算法计算得到的项目之间的推荐程度是非对称的,从而使推荐结果更加多样化.在MovieLens数据集上利用5-折交叉验证以及4种评价指标对算法进行验证,实验表明改进后的算法在提高了推荐准确性的同时也提高了推荐的多样性.

Evolvement of tsunami waves on the continental shelves with gentle slope in the China Seas

Potential tsunami generated in the Okinawa Trench or the Manila Trench may attack the southeast coast of China. The continental shelves with extremely gentle slope in the China Seas affect the evolvement of tsunami waves. In this paper, we carry out the simulation of tsunami propagation based on the fully nonlinear and highly dispersive Boussinesq model, which could describe the nonlinearity and dispersion of water waves quite well. So the undulation characters could be well presented. In terms of the real topographies of the East China Sea and the South China Sea, we take some typical profiles to simulate the hypothetical tsunamis generated in the Okinawa Trench and the Manila Trench. Different waveforms in the near shore regions are obtained. The N-shape tsunami waves will evolve into long wave trains, undular bores or solitons near the coastal area. The numerical results of the near shore waveform provide essential conditions for the further studies of tsunami runup and inundation.

Longitudinal dynamics and energy analysis for heavy haul trains

Whole trip longitudinal dynamics and energy analysis of heavy haul trains are required by operators and manufacturers to enable optimisation of train controls and rolling stock components. A new technology named train dynamics and energy analyser/train simulator （TDEAS） has been developed by the State Key Laboratory of Traction Power in China to perform detailed whole trip longitudinal train dynamics and energy analyses. Facilitated by a controller user interface and a graphic user interface, the TDEAS can also be used as a train driving simulator. This paper elaborates the modelling of three primary parts in the TDEAS, namely wagon connection systems, air brake systems and train energy components. TDEAS uses advanced wedge-spring draft gear models that can simulate a wider spectrum of friction draft gear behaviour. An effective and efficient air brake model that can simulate air brake systems in various train configurations has been integrated. In addition, TDEAS simulates the train energy on the basis of a detailed longitudinal train dynamics simulation, which enables a further perspective of the train energy composition and the overall energy consumption. To demonstrate the validity of the TDEAS, a case study was carried out on a 120-km-long Chinese railway. The results show that the employment of electric locomotives with regenerative braking could bring considerable energy benefits. Nearly 40 % of the locomotive energy usage could be collected from the dynamic brake system. Most of tractive energy was dissipated by propulsion resistance that accounted for 42.48 % of the total energy. Only a small amount of tractive energy was dissipated by curving resistance, air brake and draft gear systems.

Seismic stability evaluation of embankment slope based on catastrophe theory

An evaluation method for the seismic stability of embankment slope was presented based on catastrophe theory. Seven control factors, including internal frictional angle, cohesion force, slope height, slope angle, surface gradients, peak acceleration, and distance to fault were selected for analysis of multi-level objective decomposition. According to the normalization formula and the fuzzy subject function produced by combination of catastrophe theory and fuzzy math, a recursive calculation was carried out to obtain a catastrophic affiliated functional value, which can be used to evaluate the seismic stability of embankment slope. Fifteen samples were used to verify the effectiveness of this method. The results show that compared with the traditional quantitative method, the catastrophe progression owns higher accuracy and good application potential in predicting the seismic stability of embankment slope.

A Simulated Annealing Approach tothe Train Routing and Makeup

This paper presents the formulation and solution of a train routing and makeupmodel.This formulation results in a large scale 0-1 integer programmingproblem with nonlinear objective function, and linear and nonlinearcoastraints. We know this problem is NP-complete;hence,it is diffieult to solvefor a globelly optimal solution. In this paper we propose a simulated annealingalgorithm for the train routing and makeup problem. This method avoidsentrapment in the local minima of the objective function. The effectiveness ofthis approach has been demonstrasted by results from test casee,

The Optimizing Model and Its Solution for Making Train Working Graph with Computer on Separative Division of Double－Track Lines

The authoros specialize in the field of optunization and automatic programme oftrain working graph. In this peper, at frist, a mixed 0-1 integer progranimingmodel about this problem for duuble-track lines is set up, then the principle andProcess of selution are stated, with an application exaiiiple put forward.

基于改进非支配排序遗传算法的重载列车长大下坡运行策略

选择合适的制动缓解时机是重载列车长大下坡安全运行的关键,而列车循环制动要综合考虑线路坡度、区间限速、副风缸再充风时间等多种因素,现有的列车驾驶优化算法存在收敛速度慢和局部搜索能力不足等问题。因此,对非支配排序遗传算法(NSGA-II)进行改进,以最短空气制动距离和最高运行效率为优化目标,构建基于INSGA-II(改进NSGA-II)的重载列车长大下坡循环制动优化模型。一方面,采用动态拥挤度和精英保留方式选择个体,同时加入劣质种群自动修复策略,保证解的多样性的同时保留优秀个体;另一方面,在NSGA-II中引入变邻域搜索策略(VNS),以解决NSGA-II局部搜索能力不足的问题。最后选取朔黄铁路一段长大下坡道实际线路数据,仿真得到最优的工况转换序列,并生成列车驾驶曲线,证明了所提方法的有效性。

大坡度自移设备列车关键结构受力分析

设备列车是综采工作面上重要的辅助运输设备,能够实现工作面上相关配套设备的长距离运输。然而,传统设备列车采用钢丝绳牵引工艺,在煤矿井下大坡度的运输过程中易发生自滑移、溜车、钢丝绳断裂等事故,存在严重的安全隐患。为适应大坡度的工况,研制一种新型自移设备列车组,基于该设备列车建立其在大坡度下的受力数学模型,并对其关键元部件抱闸机构进行有限元分析,满足设备列车在±12°坡度的正常使用,充分发挥其安全高效的优势。

云巴系统线路最小坡段长度参数的探讨

列车乘坐舒适度是城市轨道交通设计过程应首先考虑到的因素。其中,线路最小坡段长度的选取对于其有着重要影响。而对于云巴系统来说,目前相关规范未对线路最小坡段长度做出明确的规定。参考跨坐式单轨等城市轨道交通制式线路最小坡段长度的计算方法,结合云巴系统自身的技术特点,通过动力学软件仿真分析与计算,得出云巴系统线路的最小坡段长度的取值。综合考虑影响最小坡段长的多种因素,包括远期列车长度、竖曲线半径及切线长度等,可以得出云巴系统的最小坡段长度一般情况下可以取200 m,困难情况下可以取100 m。

关于云巴系统最大设计坡度参数的研究

线路纵断面设计参数尤其是最大设计坡度的选取直接关系到系统运行能力、车辆运行的平稳性以及旅客乘坐的舒适性。结合诸多因素,在一般设计过程中,选取合理的最大设计坡度。论文主要创新之处在于参考地铁、跨坐式单轨等成熟的轨道交通研究理论基础上结合云巴的自身特点对云巴系统进行分析。

软土环境重载列车振动荷载作用下的边坡动力响应分析

基于某城际铁路工程,通过FLAC3D有限差分软件进行数值模拟,分析列车不同运行距离与速度下边坡的动力响应。结果表明:重载列车荷载作用下,最大主应力集中在边坡底部,随着边坡高度以及铁路与边坡距离的增加而减小。软土边坡的竖向与水平峰值加速度随着铁路与边坡距离的增大而衰减,说明当边坡与震源的距离增加后列车振动荷载对边坡的影响也随之减小。坡脚附近监测点的峰值加速度显著大于其他监测点,坡脚位置处更容易受到列车荷载影响而振动破坏。峰值加速度值越大的监测点,其峰值加速度随着边坡与铁路距离增加的衰减率越大,边坡下部对于运行距离相关的加速度衰减要比边坡其余部分更敏感。列车时速与水平、竖向峰值加速度都呈现正相关关系。

上海优秀男子短距离自行车运动员力量训练和冲坡训练课后生化指标变化规律的研究

目的:应用生化指标了解力量训练和冲坡训练后优秀男子短距离自行车运动员机体的适应规律,并对运动员机能状态和训练效果进行评定;方法:上海自行车队8名优秀男子运动员为研究对象,对其力量训练课与冲坡训练课后CK、BU、尿10项、BIa进行监测;结果: 1)力量训练课后5min的CK就达到峰值,次日晨BU、Hb较前一天早上结果变化不显著,但尿潜血栓出率增加。2)冲坡训练课后4 h的CK达到高值,次日晨CK、Hct明显升高,Hb、BU变化不显著,尿潜血检出率增加;结论:1)力量训练课后的CK达到峰值时间早于冲坡训练,但冲坡训练强度大,对肌肉的刺激较强,导致Hb破坏得更多,恢复相对较慢。2)力量训练与冲坡训练课后,尿潜血检出率增加,但是尿潜血出现的时间有明显的个体差异。3)使用Bla、CK、BU、尿10项对运动训练进行监控,可以了解运动员对运动负荷的适应情况,对教练员科学训练有重要的辅助作用。