Determination of braking force on the aerodynamic brake by numerical simulations (original) (raw)
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Analysis of the action of aerodynamic forces in case a passenger train
IOP Conference Series: Materials Science and Engineering, 2018
The growing need for mobility, cumulative with the technological development of the last decades, represents the elements that led to achieving and increasing travel speeds for the rail transport system. Currently, for classical trains formed from locomotives and wagons, the maximum travel speeds admitted into circulation are between 200 km/h and 250 km/h. Regarding the trains consisting of the multiple high-speed electric frames, they have values of the maximum permissible speeds in the range 300 km/h and 450 km/h. For obtaining such sizes of the travel speeds, it would not have been possible without having previously studied the aerodynamic phenomena much more closely which occur during the movement of vehicles. The present paper is in the same order with the studies they are pursuing analyzing the influence of aerodynamic forces acting on a train. In this regard, we considered the case of a classic passenger train made up of a motor vehicle (locomotive) and many towed vehicles (wagons). To be able to observe, how aerodynamic forces acting and what are their values, will be used a simulation program on the flow of air. The importance of determining the values and distribution of aerodynamic forces stems from the fact that they directly affect the energy consumed while traveling and in some cases even the vehicle safety.
Aerodynamics characteristics around simplified high speed train model under the effect of crosswinds
ARPN journal of engineering and applied sciences, 2015
The aerodynamics problems of train commonly come when the flow pass through train body. The increasing speed of train to achieve highly technology demands has led to increase the forces and moments and increase sensitivity of train stability and may cause the train to overturn. In this paper, two prisms arranged in tandem represent a simplified model of high speed train are performed at different yaw angle ranging from 0° to 90° by using the unsteady Reynolds-Averaged Navier Stokes (URANS) equation combined with k-? SST turbulence model. The Reynolds number is 3.14x105 based on height of the train and the free stream velocity. The aerodynamic quantities such as the side force, lift force and drag force coefficient show a similar trend where the forces increase with the yaw angle until a certain critical yaw angle before start to decrease till the yaw angle of 90°. The flow structure around the train under the effect of crosswind is visualized. The vorticiticy start to form from the ...
Wind Tunnel Testing on Crosswind Aerodynamic Forces Acting on Railway Vehicles
Journal of Fluid Science and Technology, 2010
This study is devoted to measure the aerodynamic forces acting on two railway trains, one of which is a high-speed train at 300km/h maximum operation speed, and the other is a conventional train at the operating speed 100km/h. The three-dimensional train shapes have been modeled as detailed as possible including the inter-car, the upper cavity for pantograph, and the bogie systems. The aerodynamic forces on each vehicle of the trains have been measured in the subsonic wind tunnel with 4m×3m test section of Korea Aerospace Research Institute at Daejeon, Korea. The aerodynamic forces and moments of the train models have been plotted for various yaw angles and the characteristics of the aerodynamic coefficients has been discussed relating to the experimental conditions.
Study on the aerodynamic force which acts in the case of a train type multiple unit electric
IOP Conference Series: Materials Science and Engineering
This paper seeks to analyse the values of the aerodynamic resistance forces occurring during the movement of a train type multiple unit electric whit are running in Romania. Taking into account what has been said so far in the literature, regarding the fact that the aerodynamic forces acting on the vehicles are directly proportional to the square of the traveling speed, it is intended to estimate the values of these forces in the case of the proposed train for analysis. An exact determination is difficult to achieve and requires very high costs in terms of both the measuring equipment and the actual realization of the experiment. To avoid this, we will opt for a numerical analysis of aerodynamic force measurements. In this regard, the geometric shape of the train will be first modelled and then inserted into an airflow simulation program.
Aerodynamic performances and vehicle dynamic response of high-speed trains passing each other
Journal of Modern Transportation, 2012
Based on the aerodynamics and vehicle dynamics, the aerodynamic performances and vehicle dynamic characteristics of two high-speed trains passing each other on the ground, embankment and bridge are studied. Firstly, a train aerodynamic model and a vehicle dynamic model are established. Through the simulation of the two models, the pressure waves, aerodynamic forces, and vehicle dynamic responses are obtained. Then, the pressure waves and aerodynamic forces on different foundations are compared. The results show that the variation trends of pressure wave and aerodynamic forces of trains passing each other on different foundations are almost similar. The peak-to-peak differences in pressure wave and aerodynamic force are below 4% and 3% in three cases in open air. Besides, the differences of security indexes, including coefficient of derailment, wheel unloading rate, the wheelset lateral force, and the wheelrail vertical force, are below 2% among the three cases; the differences of comfort indexes, including the lateral acceleration and the vertical acceleration, are also below 2%. It is concluded that the dynamic performances of trains passing each other are influenced little by different foundations in open air.
Effects of Crosswind on the Drag of Medium Speed Trains
Jurnal Rekayasa Mesin
Aerodynamic research on medium-speed trains is trying to map the flow of fluid around trains. The train model testing is conducted to study Cd values experimentally using a closed-loop wind tunnel at the Balai Besar Teknologi Aerodinamika, Aeroelastika, dan Aeroakustika. In addition to the experimental method, the computational method can be used to validate the experimental results, map the fluid flow around the train model, and calculate Cd values. The computational results of Cd obtained using ANSYS are compared against Cd values from wind tunnel tests. Further analysis using the ANSYS program with variations in the yaw angle can predict crosswind effects on the train model. It is found that vortices are formed around the train body, and modifying the head shape and adding fairing increases Cd values.
Effect of Crosswind on Aerodynamic Characteristics of a Generic Train Model using ANSYS
Journal of Industry, Engineering and Innovation, 2020
Today, trains are used in a variety of ways from small city trams to high-speed bullet trains and become more important to the community as it can be faster than others transport. When trains are operating at high speed, crosswind is a major issue to be encountered. Strong crosswinds may affect the running of trains via the amplified aerodynamic forces and moments. This paper analyses the effects of crosswinds on aerodynamic of a generic train model by using ANSYS Fluent. The simulations of turbulent crosswind flow over the leading and end car of the train have been performed at different yaw angles of crosswinds occurring around the train. The velocity inlet for this project is 36 km/h, the pressure outlet is 0 and the turbulence model selected is Realizable −. The incident flow angle of crosswind was varied from 0° to 90° and the worst case of the generic train model was chosen based on the validation study. The Reynolds number used, based on the height of the train and the freestream velocity was 3.7× 10 5. The results which are mainly focused and detail on the coefficient of drag, side and coefficient of lift will be analysed and predict flow patterns in various fluid flow situations. It was observed that variations of the crosswind's angles produced different flow regimes that representing slender body flow regime at a smaller range of Ψ (i.e. Ψ ≤ 45°), transition flow regime at a medium range of Ψ (i.e. 45° ≤ Ψ ≤ 60°) and bluff body flow regime at a higher range of Ψ (i.e. Ψ ≥ 60°). Side force (Cs), lift force (Cl) and drag force (Cd) were measured to consider vehicle stability due to the crosswind. Side force (Cs) was occurred due to the pressure difference on the two sides of the train and as the yaw angles increases, the side force was indicated a steady increase in value. At Ψ ≥ 60°, the decrease in lifting force (Cl) was due to the lift force's changing direction at the yaw angle is above 60°. The surface area reached by the flow decreases as the flow yaw angles increase, resulting in a reduction in the viscous friction of the ground and therefore the mean Cd. In terms of flow structures, vortex cores were observed on the train surface in slender body regime, transition flow regime, and bluff body regime. As the yaw angles increases, the more vortices were merged to form massively separated vortices on the leeward area. At Ψ = 60° and above, the conditions for the train to operate are not safe and cause overturning because the mean Cs in the bluff body flow regime is almost at its highest point.
Effect of crosswinds on aerodynamic characteristics around a generic train model
International Journal of Rail Transportation, 2018
In this article, simulations of crosswinds over a rectangular prism with two types of train nose shapes (i.e. blunt and ellipse) that are running on flat ground case are discussed. The incident flow angle is varied from 0°to 90°. The flow around the train is solved using the incompressible form of the unsteady Reynolds Navier-Stokes (URANS) equations combined with the Shear-Stress-Transport k À ω turbulence model. The Reynolds number used, based on the height of the train is 3.7 × 10 5. Two distinctive flow regimes appear which represent a slender body behaviour at a smaller range of incident flow angles (below 45°) and bluff body behaviour at a much higher range of incident flow angles (above 45°). The safety guidelines for train's operation suggested that both the train's nose geometry and the wind speed condition are the two major factors that limit the maximum allowable speed for a particular train to be travelling.
2013
Train braking performance is important for the safety and reliability of railway systems. The availability of a tool that allows evaluating such performance on the basis of the main train features can be useful for train system designers to choose proper dimensions for and optimize train's subsystems. This paper presents a modular tool for the prediction of train braking performance, with a particular attention to the accurate prediction of stopping distances. The tool takes into account different loading and operating conditions, in order to verify the safety requirements prescribed by European technical specifications for interoperability of high-speed trains and the corresponding EN regulations. The numerical results given by the tool were verified and validated by comparison with experimental data, considering as benchmark case an Ansaldo EMU V250 train-a European high-speed train-currently developed for Belgium and Netherlands high-speed lines, on which technical information and experimental data directly recorded during the preliminary tests were available. An accurate identification of the influence of the braking pad friction factor on braking performances allowed obtaining reliable results.
Braking Systems in Railway Vehicles
— Brake is an essential feature in order to retard and stop the railway vehicle within minimum possible time. This paper presents a discussion about the different braking systems used in railway vehicles. This paper also considers electrodynamic and electromagnetic braking of trains, which is of particular importance in high-speed trains. The calculation for stopping distance for railway vehicle is provided in this study. Keywords— Air brake; Straight air brake system; Automatic air brake system; Braking distance; Brake cylinder; Brake pipe; Vacuum brake; Brake delay time