The Influence of Track Structure Parameters on the Dynamic Response Sensitivity of Heavy Haul Train-LVT System

Background: In order to study the applicability of Low Vibration Track (LVT) in heavy-haul railway tunnels, this paper carried out research on the dynamic effects of LVT heavy-haul railway wheels and rails and provided a technical reference for the structural design of heavy-haul railway track structures. Methods: Based on system dynamics response sensitivity and vehicle-track coupling dynamics, the stability of the upper heavy-haul train, the track deformation tendency, and the dynamic response sensitivity of the vehicle-track system under the influence of random track irregularity and different track structure parameters were calculated, compared and analyzed. Results: Larger under-rail lateral and vertical structural stiffness can reduce the dynamic response of the rail system. The vertical and lateral stiffness under the block should be set within a reasonable range to achieve the purpose of reducing the dynamic response of the system, and beyond a certain range, the dynamic response of the rail system will increase significantly, which will affect the safety and stability of train operation. Conclusions: Considering the changes of track vehicle body stability coefficients, the change of deformation control coefficients, and the sensitivity indexes of dynamic performance coefficients to track structure stiffness change, the recommended values of the vertical stiffness under rail, the lateral stiffness under rail, the vertical stiffness under block, and the lateral stiffness under block are, respectively 160 kN/mm, 200 kN/mm, 100 kN/mm, and 200 kN/mm.

Analysis of positioning of wayside charging stations for hybrid locomotive consists in heavy haul train operations

Hybrid locomotive concepts have been considered as a step towards converting the railway industry into a green transport mode. One of the challenges in integrating a hybrid locomotive in the train consist is that the battery pack in the locomotive needs to be recharged during a long-haul trip which requires stopping of the train. A typical battery pack requires about 1 h to recharge which is unacceptable. With the improvement in the charging system, it is now possible that the same capacity battery pack could be recharged in 10–12 min which can be a competitive option for the railway companies. This paper proposes a method based on simulation to evaluate the positioning of charging stations on a train network. A typical example of a heavy haul train operation hauled by diesel-electric and hybrid locomotives is used to demonstrate the method by using simulation softwares. The result of the simulation study show that the method developed in this paper can be used to evaluate the state of charge (SoC) status of a hybrid locomotive along the track. It is also shown that the SoC status obtained by the simulation method can be further used to assess the positions of charging stations along the track at the design stage.

An Advanced Anti-Slip Control Algorithm for Locomotives Under Complex Friction Conditions

The locomotive wheelsets configured with high-power AC traction motors are very prone to slip under poor friction conditions, which usually impair traction/braking efficiency. To avoid the adverse consequence caused by the conspicuous slipping behaviors of wheels, the anti-slip control modules are consequently equipped on high-power locomotives. This paper presents an advanced anti-slip control algorithm for heavy-haul locomotives travelling with complex wheel/rail friction conditions. The proposed anti-slip control model is implemented in a three-dimensional (3D) heavy-haul train-track coupled dynamics model, in which the real-time estimation of wheel/rail adhesion conditions and relevant optimization adjustment of control threshold values are considered. The wheel/rail dynamic interactions of the heavy-haul locomotive under traction/braking conditions and multifarious friction conditions are investigated. The control effects of the anti-slip controllers with changeable and constant threshold values are compared. It is shown that the traction/braking loads and friction conditions have a significant effect on wheel/rail interactions. The optimal traction/braking efficiency can be realized by adopting the anti-slip controller with alterable threshold values.

Hill-starting a heavy haul train with a 24-axle locomotive

Head-end trains are more efficient than Distributed Power trains in terms of train marshalling. This paper studied an unprecedent real-world engineering problem to hill-start a long heavy haul train at a 1.2% up-hill gradient by using a 14400 kW 24-axle AC electric locomotive (maximum traction force 2280 kN). Longitudinal Train Dynamics simulation were conducted to assess five potential driving strategies in terms of train speed and in-train forces. The simulation results show that the locomotive can hill-start the heavy haul train with 80% traction throttle. However, maximum locomotive coupler forces (1840 kN) exceeded coupler knuckle yield strength (1780 kN) of the original coupler system design. Sensitivity analyses were conducted to assess the implications of train starting resistance for train speeds and in-train forces. The study recommends increasing coupler knuckle yield strength to 2450 kN. The increased knuckle yield strength is still lower than that of the chassis, which is able to meet system design requirement; it also enables the locomotive to hill-start by using traction throttles of 80, 90, and 100% with safety factors of 1.3, 1.2 and 1.1 respectively.