Full-scale Train Research Articles

Coupled thermal-structural analysis of an axle mounted C/C-SiC brake disc for high-speed trains

This paper examines the thermal and structural characteristics of high-speed train axle-mounted brake discs. Initially, investigate the mechanical and thermophysical properties of C/C-SiC composites. Then, dynamic data including temperature and friction coefficients of brake discs under various pressures and speeds were obtained using a full-scale train brake dynamometer. Based on the above test data, a finite element model of the C/C-SiC brake disc under emergency braking conditions at 350 km/h is established using ABAQUS software. The accuracy of the finite element model was validated through experiments, followed by a thermal-structural coupling analysis of the brake discs. Simulation results indicate the highest temperature of the brake disc occurred at 68.80 s, reaching 869.90 °C; the maximum thermal stress reached 165.44 MPa at 80.54 s; the maximum axial deformation measured 97.56 μm at 91.03 s. Although the times at which the highest temperature, maximum thermal stress and maximum axial deformation occurred were not synchronised, the overall trend was consistent. Based on the verification of experimental and simulation results, it has been confirmed that the brake disc meets the requirements of a 350 km/h high-speed train. This provides a solid theoretical foundation for the structural design and iterative upgrades of high-speed train brake discs.

Magnetic ion exchange resin for reducing disinfection byproducts in drinking water: Pilot-scale study and organic matter characterization

Disinfection is an essential step in drinking water treatment to prevent waterborne illnesses. However, reaction of disinfectants with organic matter in the water can produce carcinogenic disinfection byproducts (DBPs), including trihalomethanes (THMs) and haloacetic acids (HAAs). Magnetic ion exchange (MIEX) resin has been used as a pretreatment to remove organics and reduce DBPs. In this study, a pilot-scale water treatment plant in Birmingham, AL (USA) that employed MIEX as a pretreatment to the conventional pilot treatment train was compared against an adjacent full-scale train that did not use MIEX. THM and HAA formation was tested via simulated distribution system (SDS) testing, and changes in organic character were assessed using fluorescence spectroscopy. MIEX treatment provided 20 % and 25 % removal of THMs and HAAs, respectively, compared to the full-scale treatment under typical SDS conditions. With higher residence times and incubation temperatures (15 days at 35 °C), MIEX treatment reduced HAAs by 36 %. Parallel factor (PARAFAC) analysis revealed that MIEX treatment reduced loadings for a terrestrial humic-like component. Additionally, MIEX treatment resulted in secondary benefits, including a reduction in the coagulant feed rate and a more stable pH and chlorine residual in the MIEX-treated water compared to full-scale treatment.

Application of a parallel physics-informed neural network to solve the multi-body dynamic equations for full-scale train collisions

The prohibitive cost of acquiring data from full-scale train collision experiments limits the applicability of data-driven machine learning methods in train collision simulation. Physics-informed neural networks (PINN) attempt to address this challenge by incorporating physics equations as part of the loss function construction. However, the PINN approach is relatively time-consuming when it comes to solving a large number of physical equations. In this paper, a parallel physics-informed neural network (PPINN) methodology is developed for the solution of multibody dynamics equations to further reduce the computational cost. As well, a PPINN-based framework for engineering applications is proposed, investigating the dynamic responses, absorbed energy, collision forces, and wheel vertical rises of the full-scale train collision. Automatic differentiation and parallelization algorithms are applied to the multi-body dynamic equations including mass, damping, and stiffness matrices, as well as the. The residuals and the initial conditions are included in the loss function. The dynamic responses, absorbed energy, collision forces, and wheel vertical rise of the full-scale train collision are simulated and studied in detail. The results obtained from the PPINN method are in excellent agreement with those obtained from the finite element method (FEM), Newmark-β, and fourth-order Runge–Kutta methods for all four train collision scenarios. Additionally, the PPINN methodology keeps better stability even under large time steps which implies a big potential for computational cost reduction.

A DES study of the flow around a full-scale train under crosswind condition

A numerical study on the flow around a full-scale train subjected to crosswind has been conducted on the basis of detached-eddy simulation (DES). Finite-volume method is applied to unstructured mesh generated around a three-car-train model whose running speed is fixed to 120 km/h while the crosswind speed is set to 5 m/s,15 m/s, and 25 m/s. A clear longitudinal vortex structure is recognized in the case of the crosswind speed of 25 m/s, where two longitudinal vortices are evolved respectively from the roof and floor of the head car (roof-edge and floor-edge vortices), forming a characteristic vortex pair. This longitudinal vortex structure around the head car is discussed with a focus on its non-trivial role in the side-force mechanism. Our simulation suggests a causal association between these two vortices, which implies an importance of optimum designing of the underfloor equipment in addition to the roof and head shapes of the head car.

A field study on the aerodynamics of freight trains

A novel full-scale field test was undertaken to assess the aerodynamic performance of shipping containers loaded on inter-modal freight trains. The aerodynamic performance of an instrumented 48 ​ft container, located 185 ​m downstream of the locomotive, is assessed in the context of surface pressure, weather station, and GPS data sets. Previous studies on the aerodynamics of trains have been largely limited to low-resolution, reduced-order and scaled; field, numerical and wind-tunnel studies; respectively. The objective here was to determine the capacity of this novel field-based method to assess the aerodynamic performance of full-scale train containers for a large range of operating conditions. For low wind conditions, where the yaw angle is predicted to be low, measured surface pressure distributions on the front and base of the container are similar to that of past work however the magnitude of the drag coefficient was much lower, by up to 65%. This suggests that previous studies are yet to fully detail the drag profile of containers located at large downstream distance. Observed asymmetry of the pressure distribution on the front of the container are generally consistent with wind conditions measured at nearby weather stations and can be used as a proxy to determine the wind yaw angle at the train.

Heat release rate of high-speed train fire in railway tunnels

In this study, a cone calorimeter and an ignition temperature tester were used to conduct experiments on the combustible materials of the main structure of a train for determining its heat release rate and ignition temperature. According to the experimental data of the materials, a numerical model for high-speed train fires was established, and it was validated on the basis of full-scale train fire experiments reported in the literature. Numerical calculations were performed to study the effects of the area of the train carriage vents, power of the fire source, position of the fire source, and longitudinal ventilation velocity of the tunnel on the heat release rate. The results indicated that a higher power of the fire source corresponds to an earlier peak of the heat release rate of the train fire. When the fire source was set at the end wall corner of the carriage and the fire source power was 150–1000 kW, the peak heat release rate was 33.6–36.4 MW. The peak heat release rate of high-speed train fires has an exponential relationship with the area of the train carriage vents and an exponential decay relationship with the longitudinal ventilation velocity of the tunnel. When the fire source is below a seat and its power is low, the flame height is so small that the temperature of the smoke at the top of the train carriage is lower than the ignition temperature of the ceiling material. Hence, the ceiling material does not burn, and it is difficult for the fire to spread in the carriage. The flame spread characteristics of the fire are similar when the source is at other positions. The flame spreads along the ceiling to the two ends of the carriage, causing the seat and floor to burn owing to the heat radiation from the ceiling.

Full-Scale Train Derailment Testing and Analysis of Post-Derailment Behavior of Casting Bogie

In this study, a full-scale train bogie derailment test was conducted. For this, test methodologies to describe the wheel-climbing derailment of the train bogie and to obtain accurate test data were proposed. The derailment test was performed with the casting bogie for a freight train and a Rheda 2000 concrete track. Two different derailment velocities (28.08 km/h and 55.05 km/h) were considered. From the test, it was found that humps in the concrete track affected the post-derailment behavior of the bogie when the derailment velocity was 28.08 km/h. For a higher derailment velocity (55.05 km/h), significant lateral movement of the derailed bogie was observed. This lateral movement was first controlled by wheel–rail contact, followed by contact with the containment wall. Finally, the train was returned to the track center.

Characteristics of fire in high-speed train carriages

With the rapid development of high-speed railways, safety hazards presented by train fires cannot be ignored. An effective design for protection against fire in high-speed trains is essential to ensure passenger safety. In this study, the cone calorimeter and ignition temperature tester were used to carry out combustion experiments on materials constituting the main components of the train. The heat release rate, smoke yield, CO yield, and ignition temperature of combustible materials were tested. Based on the experimental data of material combustion, a numerical model of the high-speed train carriage fire was simulated. The accuracy of the numerical simulation was verified by drawing a comparison with the full-scale train fire experiment in existing literature. The numerical simulation results revealed that when the fire source is present at the corner of the carriage end door, the fire develops to the maximum possible extent in approximately 25 min, with a peak heat release rate of approximately 38.4 MW. Increase in the carriage fire heat release rate and breakage of windows occur almost simultaneously. Improvement of the fireproof performance of windows can inhibit and delay the carriage fire development. For the flashover of carriage fire, the spread speed of the flashover area in the longitudinal direction inside the carriage is approximately 1.9 m/s. The end door area furthest from the fire source in the carriage has strong flashover, while the flashover in other areas is weak.

Numerical-experimental analysis of the slipstream produced by a high speed train

The recent development of high-speed trains over the last decade led to a growing interest in their aerodynamics. A train at full operational speed generates a strong induced airflow that may damage infrastructures near the trackside and endanger people near the rails. Nowadays the tests required for the train homologation are based on full scale measurements of the airspeed taken in specified positions close to the railway line. An important part of the work was initially dedicated to the data analysis of an extensive experimental campaign performed on the Italian high-speed line, in order to obtain reliable results to be used for comparison with CFD results. These ones have been performed on the full-scale train geometry using an URANS approach with a wall treatment based on wall functions, checking mesh and turbulence models dependencies. The full-scale simulations highlighted the great complexity of the problem being the comparison with the experimental measurements performed close to the shear layer of the train boundary layer. Encouraging results are obtained from the numerical analysis on the full-scale train geometry indicating the ability of the URANS coupled with the SST turbulence model in the prediction of both the train induced flow and the turbulent structures around it.

Effect of train length on fluctuating aerodynamic pressure wave in tunnels and method for determining the amplitude of pressure wave on trains

In this study, the aerodynamic performance of full-scale trains of different lengths going through or crossing each other in a tunnel was investigated using sliding mesh technology and a numerical algorithm developed and verified through a full-scale train test. The waveforms of the fluctuating pressure distribution on the train and in the tunnel were compared and analyzed, and the effect of the train length on the flow field in the tunnel examined. The results show that, because of the significant difference in pressure amplitude, long trains cannot be replaced by short trains when simulating trains going through or crossing each other in tunnels. However, some common regular patterns, such as the distribution of the peak values of the time evolution of pressure on the train and in the tunnel, can still be found in both cases. It was found that, for the evaluation of the fatigue effect induced by pressure on the train body, the equivalent load method based on the Paris formula is more secure and reliable than the root-mean-square equivalent load method. It was also discovered that, while analyzing the effect of the fluctuating aerodynamic pressure, it is better from the viewpoint of safety to consider the maximum pressure on the constant-section part of the train body as the representative parameter.

Numerical simulation of the Reynolds number effect on the aerodynamic pressure in tunnels

With an increase in train speed, the aerodynamic effects caused by the train could escalate, especially for a train running in a tunnel. A number of large transient pressure waves are generated owing to the confined spaces within the tunnel, resulting in possible damage to the vehicle structure and the facilities in the tunnel. Therefore, it is necessary to study the aerodynamic performance of a train running in a tunnel. A scaled moving model test system was constructed to facilitate the simulation of the aerodynamic effects caused by a train running in a tunnel. In this study, the influence of grid density, calculation time step, and turbulence model on the pressure caused by the train entering the tunnel was analyzed, which is helpful for choosing suitable values of the aforementioned parameters to simulate the aerodynamic performance of the train in the tunnel. The impacts of Reynolds number effect on the distribution of the surface pressure and peak of pressure wave along the train, and the pressure waveform were also studied through numerical simulation on three scaled model trains (full scale, 1/8, 1/20, and 1/32 scaled). The findings aid in understanding the relationship between the Reynolds and pressure amplitude, and the results of the scaled test can be applied to a full-scale train.

Analysis on Aerodynamic Effect of Common Passenger Train and EMU Passing by Each Other under Crosswind

The three-dimensional unsteady N-S equation and the k-e equation turbulence model were made to solve the aerodynamic performance of common passenger train passing by Electric Multiple Units (EMU) under crosswind based on the finite volume method and sliding mesh method. The results of full-scale train experimental method and numerical simulation method were compared. The results of numerical simulation show that when common passenger train and EMU pass by each other under crosswind, crosswind has great effect on the aerodynamic performance of trains. When there is no crosswind, the lateral force of the locomotive of common passenger train and the first car of EMU are the largest, 11.55 kN and 6.25 kN respectively. When there is crosswind and the wind speed reaches 40 m/s, the overturning moment of common passenger train and EMU are 87.9 kN·m and 239.9 kN·m, which means when trains pass by each other under strong wind, there are great security risks. When wind-break walls are set in line side, lateral forces of trains are significantly decreased.

Numerical study of the aerodynamics of a full scale train under turbulent wind conditions, including surface roughness effects

A numerical simulation of the aerodynamic behavior of a full scale train under synthetic crosswind is presented. Both smooth and rough train surfaces are contemplated in this paper. The synthetic wind is defined based on the Kaimal spectrum, which is generated using Turbsim. The flow description is based on numerical simulations obtained using Large Eddy Simulation (LES) with the commercial code ANSYS-Fluent. Considering a very-high Reynolds number for our train model with LES requires the use of a wall function in the near-wall region. In this way, it is removed the need to resolve any turbulent eddies in the inner part of the wall layer, and the entire inner-layer dynamics are represented by a single value of the wall shear stress. The simulation gives a time history of the force and moments acting on the train; this includes averaged values, standard deviations and extreme values. Of particular interest are the spectra and admittances of the forces and moments. Comparisons are made with numerical and experimental results obtained for a small scale model fixed to the ground in a wind tunnel.

High-Speed Particle Image Velocimetry of the Flow around a Moving Train Model with Boundary Layer Control Elements

Trackside induced airflow velocities, also known as slipstream velocities, are an important criterion for the design of high-speed trains. The maximum permitted values are given by the Technical Specifications for Interoperability (TSI) and have to be checked in the approval process. For train manufactures it is of great interest to know in advance, how new train geometries would perform in TSI tests. The Reynolds number in moving model experiments is lower compared to full-scale. Especially the limited model length leads to a thinner boundary layer at the rear end. The hypothesis is, that the boundary layer rolls up to characteristic flow structures in the train wake, in which the maximum flow velocities can be observed. The idea is to enlarge the boundary layer using roughness elements at the train model head so that the ratio between the boundary layer thickness and the car width at the rear end is comparable to a full-scale train. This may lead to similar flow structures in the wake and better prediction accuracy for TSI tests. In this case, the design of the roughness elements is limited by the moving model rig. Small rectangular roughness shapes are used to get a sufficient effect on the boundary layer, while the elements are robust enough to withstand the high accelerating and decelerating forces during the test runs. For this investigation, High-Speed Particle Image Velocimetry (HS-PIV) measurements on an ICE3 train model have been realized in the moving model rig of the DLR in Gottingen, the so called tunnel simulation facility Gottingen (TSG). The flow velocities within the boundary layer are analysed in a plain parallel to the ground. The height of the plane corresponds to a test position in the EN standard (TSI). Three different shapes of roughness elements are tested. The boundary layer thickness and displacement thickness as well as the momentum thickness and the form factor are calculated along the train model. Conditional sampling is used to analyse the size and dynamics of the flow structures at the time of maximum velocity in the train wake behind the train. As expected, larger roughness elements increase the boundary layer thickness and lead to larger flow velocities in the boundary layer and in the wake flow structures. The boundary layer thickness, displacement thickness and momentum thickness are increased by using larger roughness especially when applied in the height close to the measuring plane. The roughness elements also cause high fluctuations in the form factors of the boundary layer. Behind the roughness elements, the form factors rapidly are approaching toward constant values. This indicates that the boundary layer, while growing slowly along the second half of the train model, has reached a state of equilibrium.

Numerical simulation of aerodynamic performance of a couple multiple units high-speed train

ABSTRACTIn order to determine the effect of the coupling region on train aerodynamic performance, and how the coupling region affects aerodynamic performance of the couple multiple units trains when they both run and pass each other in open air, the entrance of two such trains into a tunnel and their passing each other in the tunnel was simulated in Fluent 14.0. The numerical algorithm employed in this study was verified by the data of scaled and full-scale train tests, and the difference lies within an acceptable range. The results demonstrate that the distribution of aerodynamic forces on the train cars is altered by the coupling region; however, the coupling region has marginal effect on the drag and lateral force on the whole train under crosswind, and the lateral force on the train cars is more sensitive to couple multiple units compared to the other two force coefficients. It is also determined that the component of the coupling region increases the fluctuation of aerodynamic coefficients for each train car under crosswind. Affected by the coupling region, a positive pressure pulse was introduced in the alternating pressure produced by trains passing by each other in the open air, and the amplitude of the alternating pressure was decreased by the coupling region. The amplitude of the alternating pressure on the train or on the tunnel was significantly decreased by the coupling region of the train. This phenomenon did not alter the distribution law of pressure on the train and tunnel; moreover, the effect of the coupling region on trains passing by each other in the tunnel is stronger than that on a single train passing through the tunnel.

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.

Full-scale freight train underbody aerodynamics with application to track spraying

ABSTRACTIn this article, measurements of full-scale freight train underbody aerodynamics relevant to top-of-rail spraying are presented. The velocity near the wheel was measured using hot wire anemometers mounted on the train. The pressure was measured using transducers mounted adjacent to the track. Velocity scaled linearly with locomotive speed and pressure scaled linearly with dynamic pressure, implying negligible Reynolds number effects. The mean velocity near the wheels was less than half of the locomotive speed when the vehicle moved at or greater than the ambient wind speed. The velocity upwind of the wheel was 30% greater than downwind of the wheel. These mean velocities are consistent with computational fluid dynamics simulations of the flow field in the vicinity of the wheel. Turbulence intensity levels were measured to be 0.08–0.16. The pressure at the track depends on the configuration of the leading car; the maximum pressure drop was 65% greater when the hopper car preceded the locomotive compared to when the locomotive preceded the hopper car.

A New Methodology of Design Fires for Train Carriages Based on Exponential Curve Method

Design fires have great influences on the fire safety concepts and safety measures, and are the basis for any assessment and calculation in tunnel fire safety design. A new methodology of design fires for individual train carriages is proposed based on the exponential design fire curve method and state-of-the-art fire research. The three key parameters required for construction of a design fire are the maximum heat release rate, time to maximum heat release rate, and energy content. An overview of the full scale train carriage fire tests is given and the results show that the maximum heat release rate is in a range of 7 MW to 77 MW and the time to reach the maximum heat release rate varies from 7 min to 118 min. The method could be employed to one single train carriage or several carriages, and alternatively one carriage could be divided into several individual sections. To illustrate the use of the methodology, several engineering applications are presented, including design fires for a metro train carriage with a maximum heat release rate of 77 MW, a double-deck railway train carriage with a maximum heat release rate of 60 MW and a tram carriage with a maximum heat release rate of 28 MW. The main objective is to provide practicing engineers with a flexible and reliable methodology to make design fires for individual train carriages in performance-based tunnel fire safety design.

Fault Detection and Isolation for a Railway Vehicle by Evaluating Estimation Residuals

The capacity of transport as well as the number of passengers is growing in the railway industry. At the same time, the pressure to reduce service costs rises. Reliability and dependability in complex mechanical systems can be improved by fault detection and isolation methods (FDI). These techniques are key elements for maintenance on demand, which could decrease service cost and time significantly. This work addresses FDI for a railway vehicle: The mechanical model is described as a multibody system, which is excited randomly due to track irregularities. The aim of this work is to detect faults in the suspension system of the vehicle. A Kalman filter is used to estimate the states. In order to detect and isolate faults, the detection error is minimized with multiple Kalman filters. A full scale train model with nonlinear wheel rail contact and nonlinear suspension forces serves as an example for the described techniques. Numerical results for different test cases are presented. For the analysed system it is possible not only to detect a failure of the suspension system from the system's dynamic response, but also to distinguish clearly between different possible causes for the changes in the dynamical behavior.

Fault detection and isolation for a full-scale railway vehicle suspension with multiple Kalman filters

Reliability and dependability in complex mechanical systems can be improved by fault detection and isolation (FDI) methods. These techniques are key elements for maintenance on demand, which could decrease service cost and time significantly. This paper addresses FDI for a railway vehicle: the mechanical model is described as a multibody system, which is excited randomly due to track irregularities. Various parameters, like masses, spring- and damper-characteristics, influence the dynamics of the vehicle. Often, the exact values of the parameters are unknown and might even change over time. Some of these changes are considered critical with respect to the operation of the system and they require immediate maintenance. The aim of this work is to detect faults in the suspension system of the vehicle. A Kalman filter is used in order to estimate the states. To detect and isolate faults the detection error is minimised with multiple Kalman filters. A full-scale train model with nonlinear wheel/rail contact serves as an example for the described techniques. Numerical results for different test cases are presented. The analysis shows that for the given system it is possible not only to detect a failure of the suspension system from the system's dynamic response, but also to distinguish clearly between different possible causes for the changes in the dynamical behaviour.