Stability Of High-speed Train Research Articles

Mechanism analysis of low-frequency swaying motion of high-speed trains induced by aerodynamic loads

Abnormal carbody vibrations can significantly affect the safety and stability of high-speed trains. In this study, we conducted field measurements to analyze low-frequency swaying of a high-speed train on the Chinese alpine railway line. The test results reveal that the tail vehicle of the train swayed laterally in certain sections of the track, resulting in vehicle lateral stability index exceeding the limit. The swaying frequency of the carbody was mainly distributed in the range of 1.4–1.5 Hz. The causes of abnormal swaying were analyzed by establishing a computational fluid calculation model. Computational fluid dynamics calculations revealed that lift force, side force, and yaw moment were higher for the tail vehicle compared to the head and middle vehicles. The train-track coupled dynamics simulation results demonstrate that aerodynamics disturbances may be the key factor to intensify the abnormal swaying of the high-speed train tail vehicle.

Deep PCA-Based Incipient Fault Diagnosis and Diagnosability Analysis of High-Speed Railway Traction System via FNR Enhancement

In recent years, the data-driven based FDD (Fault Detection and Diagnosis) of high-speed train electric traction systems has made rapid progress, as the safe operation of traction system is closely related to the reliability and stability of high-speed trains. The internal complexity and external complexity of the environment mean that fault diagnosis of high-speed train traction system faces great challenges. In this paper, a wavelet transform-based FNR (Fault to Noise Ratio) enhancement is realised to highlight incipient fault information and a Deep PCA (Principal Component Analysis)-based diagnosability analysis framework is proposed. First, a scheme for FNR enhancement-based fault data preprocessing with selection of the intelligent decomposition levels and optimal noise threshold is proposed. Second, fault information enhancement technology based on continuous wavelet transform is proposed from the perspective of energy. Further, a Deep-PCA based incipient fault detectability and isolatability analysis are provided via geometric descriptions. Finally, experiments on the TDCS-FIB (Traction Drive Control System–Fault Injection Benchmark) platform fully demonstrate the effectiveness of the method proposed in this paper.

Prediction of Ply Angles of Air Springs According to Airbag Positions and Their Effects on Lateral and Torsional Stiffness

The stiffness in various directions of air springs have a great influence on the stability of high-speed trains. Due to the change in the bogie structure, the required functions of the air springs have also diversified, and the damping of various loading modes such as vertical, lateral, and torsional movements is emerging as important. The stiffnesses are affected by the shape of the air bag, the material, and the ply angles. In this paper, the relationship between the ply angle and the radial position is proposed by equations from deformation modes. The variable angles in the plies were compared and demonstrated in air-spring analysis using the rebar elements. The vertical, lateral, and torsional stiffness of air springs without auxiliary springs were compared between constant ply angles and variable ply angles with respect to the positions. When mainly dealing with the vertical stiffness, the effect of the angle variation was small; however, it was found that it had a large effect of more than 24% and 30% on the stiffness in the lateral direction and torsional direction, respectively.

Shielding and internode effects of truss bridge on the aerodynamic characteristics of high-speed train under crosswinds

Accurately simulating the aerodynamic characteristics is important to the safety and stability of high-speed train, especially when it operates under strong crosswinds. In recent, long span highway-railway bridge has been developed rapidly to enable the high-speed rail to cross wide rivers and valleys, where the truss bridges are usually served as the main girder type. This study aims to investigate the unique interference effects on the aerodynamic characteristics of the high-speed train caused by the truss bridge, i.e., the so-called shielding effect and internode effect. The shielding effect of the truss bridge on the mean aerodynamic coefficients is firstly quantified based on a moving train model test in wind tunnel. Combined with a 3-D computational fluid dynamic (CFD) model validated by the wind tunnel test, a series of numerical simulations are conducted to study the mechanism of internode effect, where the airflow field and pressure distributions around the train body and on the bridge surface are interpreted. The results reveal that the truss bridge has an obvious whole and local shielding effects, with the first effect introducing a remarkable decrease on the aerodynamic forces of trains at the entrance and the second effect leading to an intermittent excitation.

차륜 플랜지 형상변화가 철도차량 주행안전성에 미치는 영향 검토

The wheel profile is important factor for running stability of high speed train. In this study, analysis was performed using VI-rail according to vehicle and line condition for two KTX powered vehicle – in order to examine the safety of the vehicle depending on the thickness of the wheel flange. The evaluation of the derailment coefficient, the ratio of wheel unloading, and the running behavior of the car-body and the bogie were less than the reference limits in the entire speed range in both flange thicknesses in the running stability evaluation. The wear index and vibration acceleration of the flange thickness 27mm were slightly larger than those of 29mm.

Aerodynamic characteristics of high speed train under turbulent cross winds: A numerical investigation using unsteady-RANS method

Increasing velocity combined with reduced mass of modern high speed trains poses the question of influence of strong cross winds on its aerodynamics. Strong cross winds may affect the running stability of high speed trains via the amplified aerodynamic forces and moments. In this study, simulations of turbulent cross wind flows over the leading and end car of ICE-2 high speed train have been performed at different yaw angles The train aerodynamic problems are closely associated with the flows occurring around train. The flow around the train has been considered as incompressible and was obtained by solving the incompressible form of the unsteady Reynolds-Averaged Navier-Stokes (RANS) equations combined with the realizable k-epsilon turbulence model. Important aerodynamic coefficients such as the side force and rolling moment coefficients have been calculated for yaw angles ranging from -30° to 60° and compared to results obtained from wind tunnel tests. The dependence of the flow structure on yaw angle has also been presented.

Stability of high speed trains

Recent developments in the understanding of the lateral dynamics of railway vehicles are reviewed with particular reference to the problems of dynamic stability, guidance and response to track features. The emphasis is placed on the physical models used and the broad conclusions they lead to, rather than the engineering design that represents the practical application of the subject