Application of tuned-mass system on railway catenary to improve dynamic performance
Introduction
The pantograph-catenary system is widely used to collect and transfer electric current from the stationary infrastructure to the moving trainset. Since the catenary is not continuously supported, the vertical elasticity variation of the catenary causes periodical oscillation when the pantograph slides against the catenary. The oscillation leads to wave propagation forward and backward along the wires of the catenary system. Wire misalignment, structural errors and uneven mass distribution of the catenary make the oscillation heavier and more complicated. If the dynamic response between pantograph and catenary is not sufficiently suppressed, it can lead to poor quality of electric current collection, magnetic interference, short service life of key components, or even excessive movement or structural damage at high speeds [1]. Therefore, the dynamic performance of the pantograph-catenary interaction has become one of the key factors which determines the operational speed.
In order to achieve good dynamic performance and thus high operational speed, there are a lot of investigations ongoing. The common methods to achieve this goal are: increasing the tensile loads on the catenary wires to increase the wave propagation speed, and adopting a low-stiffness-variation catenary designs to minimize the elasticity deviation [1], [2], [3], [4], [5], [6], [7]. With help of these measures, it is possible to achieve operational speeds of 350 km/h and above on newly-built passenger-dedicated lines. However, for a large proportion of the existing railway lines around the world, there is still a huge demand for more reliability and higher operability under increased speed with minimum of modifications. To upgrade the existing catenary systems, other measures, like pre-sag in the mid-span of the catenary, droppers with additional damping, optimized pantograph suspension and actively-control pantograph, have been investigated recently [3], [8], [9], [10], [11], [12]. In addition, the simulation of the pantograph-catenary interaction has been proven to be an efficient method and is widely adopted in the studies on the pantograph-catenary dynamics [13]. Many studies have contributed to improve the numerical models by identifying system damping, including environmental and track perturbations, modeling wind load and comparing simulation with measurement [14], [15], [16], [17], [18], [19], [20], [21].
From the structural aspect, the contact wire of the catenary, which is directly in contact with the pantograph, is suspended to the messenger wire and the supporting structures through droppers to keep the geometry and the vertical elasticity as smooth and uniform as possible. Today, all components fixed to the catenary, e.g. clamps, steady arms and other fittings, have to be made as light and small as possible to minimize disturbances and reflections. These lumped-masses are impossible to be completely removed, but may easily be adjusted on purpose during maintenance to improve the performance. In other engineering applications, some well-designed masses or mass systems are deliberately introduced to beneficially change the dynamic behaviour, such as the masses of stock bridge dampers for overhead power lines, balancing weights used on car wheels and other high-speed rotating bodies, and active and passive tuned-mass systems on large structures, such as buildings and bridges [22], [23], [24]. The additional mass applied neither reduces the overall capacity nor introduces much dynamic disturbance into their systems, but can improve the dynamic behaviour by effectively splitting the resonant peak and reducing the amplitude of mechanical vibration to mitigate excessive oscillations. In order to take advantage of the existing and unavoidable lumped-masses on the railway catenary systems and thus to improve the dynamic performance, it is necessary to carefully investigate the relationship between the lumped masses on the catenary and its resultant dynamic behaviour.
This paper performs a numerical study on additional lumped-mass implementation on a Swedish soft catenary system and its dynamic influence. With help of a 3D pantograph-catenary finite element (FE) model [25], the dynamic performances of different mass arrangements in single-pantograph operation and in multi-pantograph operation are investigated by varying the weight of the catenary clamp and/or introducing additional lumped-masses at different positions on the catenary. To further enhance the dynamic performance, the additional lumped-masses are tuned to the original mass system. This paper takes the following parameters into consideration: the position of the applied mass, the weight of the applied mass and the elasticity of the connection between the mass and the catenary. To address the effect caused by the additional masses, the influencing process of the lumped-mass is shortly described by comparing the results from different mass-applied configurations. Finally, this paper gives some suggestions on the implementation of the tuned-mass system to improve the dynamic behaviour.
Section snippets
Modeling and scenario description
Dynamic analysis of the pantograph-catenary system by numerical simulations is an efficient and widely adopted methodology by many researchers [13] and a general procedure for the dynamic analysis of pantograph-catenary interaction is proposed for example in [26]. The present study on the application of additional lumped-masses is based on a 3D pantograph-catenary finite element (FE) model, which has been validated with on-track testing results and in a benchmark [25]. The model considers the
Results
On the basis of the described system in Section 2, we investigate the effects of the additional lumped-mass and tuned-mass system for both single-pantograph operation and multi-pantograph operation. Initially, the dynamic behaviours of the lumped-mass ranging from 0.5 kg to 2 kg and at the 15 locations on the catenary are all obtained. In addition, in the cases with elastic connection, elasticities of the connection ranging from 500 N/m to 3000 N/m are checked. However, limited by the space of
Discussion
The additional lumped-mass and tuned-mass system can change the dynamic behaviour of the pantograph-catenary system as mentioned above, sometimes positive and sometimes negative. In this process, the location of the mass applied, the amount of weight, and the tuning stiffness determine the dynamic behaviour. However, due to the complexity of the pantograph-catenary system which is subjected to a great number of factors, it is very hard to include all the influencing factors in a simulation in
Conclusions
With help of a 3D pantograph-catenary finite element model, this paper performs a numerical study on additional lumped-mass application on the railway catenary system. The paper mainly discusses the influence of the mass location, the amount of weight, the number of pantographs and the elasticity of the mass connection on the dynamic performance of the pantograph-catenary system and briefly addresses the influencing mechanism of the tuned-mass system. The following conclusions can be drawn from
Acknowledgement
We would like to thank Schunk group for providing us the input data for the pantograph used in the simulation.
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