Modelling dynamic pantograph loads with combined numerical analysis

Appropriate interaction between pantograph and catenary is imperative for smooth operation of electric trains.Changing heights of overhead lines to accommodate level crossings,overbridges,and tunnels pose significant challenges in maintaining consistent current collection performance as the pantograph aerodynamic profile,and thus aerodynamic load changes significantly with operational height.This research aims to analyse the global flow characteristics and aerodynamic forces acting on individual components of an HSX pantograph operating in different configurations and orientations,such that the results can be combined with multibody simulations to obtain accurate dynamic insight into contact forces.Specifically,computational fluid dynamics simulations are used to investigate the pantograph component loads in a representative setting,such as that of the recessed cavity on a Class 800 train.From an aerodynamic perspective,this study indicates that the total drag force acting on non-fixed components of the pantograph is larger for the knuckle-leading orientation rather than the knuckle-trailing,although the difference between the two is found to reduce with increasing pantograph extension.Combining the aerodynamic loads acting on individual components with multibody tools allows for realistic dynamic insight into the pantograph behaviour.The results obtained show how considering aerodynamic forces enhance the realism of the models,leading to behaviour of the pantograph-catenary contact forces closely matching that seen in experimental tests.

Active suspension in railway vehicles:a literature survey

Since the concept of active suspensions appeared,its large possible benefits has attracted continuous exploration in the field of railway engineering.With new demands of higher speed,better ride comfort and lower maintenance cost for railway vehicles,active suspensions are very promising technologies.Being the starting point of commercial application of active suspensions in rail vehicles,tilting trains have become a great success in some countries.With increased technical maturity of sensors and actuators,active suspension has unprecedented development opportunities.In this work,the basic concepts are summarized with new theories and solutions that have appeared over the last decade.Experimental studies and the implementation status of different active suspension technologies are described as well.Firstly,tilting trains are briefly described.Thereafter,an indepth study for active secondary and primary suspensions is performed.For both topics,after an introductory section an explanation of possible solutions existing in the literature is given.The implementation status is reported.Active secondary suspensions are categorized into active and semi-active suspensions.Primary suspensions are instead divided between acting on solid-axle wheelsets and independently rotating wheels.Lastly,a brief summary and outlook is presented in terms of benefits,research status and challenges.The potential for active suspensions in railway applications is outlined.

Influence of Shear Effects on the Characteristics of Axisymmetric Wave Propagation in a Buried Fluid‑Filled Pipe

The acoustic propagation characteristics of axisymmetric waves have been widely used in leak detection of fluid-filled pipes.The related acoustic methods and equipment are gradually coming to the market,but their theoretical research obviously lags behind the field practice,which seriously restricts the breakthrough and innovation of this technology.Based on the fully three-dimensional effect of the surrounding medium,a coupled motion equation of axisymmetric wave of buried liquid-filled pipes is derived in detail,a contact coefficient is used to express the coupling strength between surrounding medium and pipe,then,a general equation of motion was derived which contain the pipe soil lubrication contact,pipe soil compact contact and pipe in water and air.Finally,the corresponding numerical calculation model is established and solved used numerical method.The shear effects of the surrounding medium and the shear effects at the interface between surrounding medium and pipe are discussed in detail.The output indicates that the surrounding medium is to add mass to the pipe wall,but the shear effect is to add stiffness.With the consideration of the contact strength between the pipe and the medium,the additional mass and the pipe wall will resonate at a specific frequency,resulting in a significant increase in the radiation wave to the surrounding medium.The research contents have great guiding effect on the theory of acoustic wave propagation and the engineering application of leak detection technology in the buried pipe.

Evaluation of power regeneration in primary suspension for a railway vehicle

To improve the fuel economy of rail vehicles,this study presents the feasibility of using power regenerating dampers(PRDs)in the primary suspension systems of railway vehicles and evaluates the potential and recoverable power that can be obtained.PRDs are configured as hydraulic electromagnetic-based railway primary vertical dampers and evaluated in parallel and series modes(with and without a viscous damper).Hydraulic configuration converts the linear behavior of the track into a unidirectional rotation of the generator,and the electromagnetic configuration provides a controllable damping force to the primary suspension system.In several case studies,generic railway vehicle primary suspension systems that are configured to include a PRD in the two configuration modes are modeled using computer simulations.The simulations are performed on measured tracks with typical irregularities for a generic UK passenger route.The performance of the modified vehicle is evaluated with respect to key performance indicators,including regenerated power,ride comfort,and running safety.Results indicate that PRDs can simultaneously replace conventional primary vertical dampers,regenerate power,and exhibit desirable dynamic performance.A peak power efficiency of 79.87%is theoretically obtained in series mode on a top-quality German Intercity Express track(Track 270)at a vehicle speed of 160 mile/h(~257 km/h).

IGIgram:An Improved Gini Index-Based Envelope Analysis for Rolling Bearing Fault Diagnosis

The transient impulse features caused by rolling bearing faults are often present in the resonance frequency band which is closely related to the dynamic characteristics of the machine structure.Informative frequency band identification is a crucial prerequisite for envelope analysis and thereby accurate fault diagnosis of rolling bearings.In this paper,based on the ratio of quasi-arithmetic means and Gini index,improved Gini indices(IGIs)are proposed to quantify the transient impulse features of a signal,and their effectiveness and advantages in sparse quantification are confirmed by simulation analysis and comparisons with traditional sparsity measures.Furthermore,an IGI-based envelope analysis method named IGIgram is developed for fault diagnosis of rolling bearings.In the new method,an IGI-based indicator is constructed to evaluate the impulsiveness and cyclostationarity of the narrow-band filtered signal simultaneously,and then a frequency band with abundant fault information is adaptively determined for extracting bearing fault features.The performance of the IGIgram method is verified on the simulation signal and railway bearing experimental signals and compared with typical sparsity measures-based envelope analysis methods and log-cycligram.The results demonstrate that the proposed IGIs are efficient in quantifying bearing fault-induced transient features and the IGIgram method with appropriate power exponent can effectively achieve the diagnostics of different axle-box bearing faults.