侧风下半挂货车侧移特性的分析与优化

为提高某带导流罩的半挂货车侧风作用下的行驶安全性,首先采用CFD与多体动力学软件,对高速行驶的半挂货车侧风作用下的侧移特性进行了分析;然后以导流罩为对象,采用优化拉丁超立方方法进行试验设计;最后基于Kriging模型建立了代理模型,并以此为基础,利用多岛遗传算法进行优化.结果表明,与安装初始导流罩的半挂货车相比,安装优化导流罩后的半挂货车在侧风作用下的侧向位移最大约降低了10％.     

MLX01磁悬浮列车横风气动力特性数值分析

基于二维定常不可压缩N-S方程和κ-ε两方程湍流模型,采用有限容积法对MLX01型磁悬浮列车在横风作用下的气动力特性进行了详细的数值计算,得到了列车在不同运行工况下受到的侧向力、升力和倾覆力矩变化规律;深入探讨了自然风速分布和列车运行速度对磁悬浮列车横风气动力特性的影响。     

强侧风下高架桥上轨道列车的安全运行

城市轨道列车在高架桥上运行时会受到强侧 风的影响,危及列车的安全运行。结合北京地铁 13 号 线、昌平线等线路的实际情况,针对强侧向风下列车的 安全运行问题,采用 SIMPACK 软件建立单车三维动力 学仿真模型。以高速列车在侧向风下的空气动力学模 拟计算得到的风载荷数据为基础,推导出列车在低速行 驶的风荷载,分析强侧风对列车在高架线路曲线段上 动力学性能的影响。结果表明,在强侧风影响下,列车 的轮轨动力参数考察指标( 如轮轨横向力、脱轨系数及 减载率) 均显著增大。最后提出在强侧风影响下,列车 在不同曲线半径下安全运行的最高车速参考值。     

A model for vehicle–track random interactions on effects of crosswinds and track irregularities

A stochastic mathematical model is developed to evaluate the dynamic behaviours and statistical responses of vehicle–track systems when random system excitations including crosswinds and track irregularities are imposed. In this model, the railway vehicle is regarded as a multi-rigid-body system, the track system is modelled by finite element theory. These two systems are spatially coupled by the nonlinear wheel–rail contact forces and unsteady aerodynamic forces. The high efficiency and accuracy of this stochastic model are validated by comparing to the robust Monte-Carlo method. Numerical studies show that crosswinds have a great influence on the dynamic performance of vehicle–track systems, especially on transverse vibrations. When the railway vehicle initially runs into the wind field, it will experience a severe vibration stage, and then stepping into a relatively steady state where the fluctuating winds and track irregularities will play deterministic roles in the deviations of system responses. Moreover, it is found that track irregularities should be properly considered in the safety assessment of the vehicle even in strong crosswinds.     

The design of a hold-off device to improve the lateral comfort of rail vehicles

ABSTRACT

Rail vehicles negotiating curves or in crosswinds are subjected to high lateral forces which provoke high displacements of the lateral suspension. As these displacements need to be limited due to gauging restrictions these forces cause the lateral suspension to reach the bumpstops and consequently the passenger comfort is significantly jeopardized. The paper presents the design of a pneumatic system that allows limiting the lateral displacement during curve negotiation (hold-off device). It describes the different phases of the design process starting from the definition of requirements to be fulfilled. The main components and the effect of their characteristics on the overall performance of the centring system are studied, and completed with an experimental analysis of the centring system. Finally, the described methodology is applied to a typical high speed rail vehicle. The results prove that the concept of a centring system which uses the same technology and components that are used in rail vehicles for the pneumatic height control system of secondary suspensions is possible. This fact is particularly interesting as the market offers this kind of components and has proven their reliability during many hours of service therefore the new hold-off system will be based on in-service validated components.