The maintenance of railway systems is critical for their safe operation. However some landscape geographical features force the track line to have sharp curves with small radii. Sharp curves are known to be the main source of wheel flange wear. The reduction of wheel flange thickness to an extreme level increases the probability of train accidents. To avoid the unsafe operation of a rail vehicle, it is important to stay continuously up to date on the status of the wheel flange thickness dimensions by using precise and accurate measurement tools. The wheel wear measurement tools that are based on laser and vision technology are quite expensive to implement in railway lines of developing countries. Alternatively significant measurement errors can result from using imprecise measurement tools such as the hand tools, which are currently utilized by the railway companies such as Addis Ababa Light Rail Transit Service (AALRTS). Thus, the objective of this research is to propose and test a new measurement tool that uses an inductive displacement sensor. The proposed system works in both static and dynamic state of the railway vehicle and it is able to save the historical records of the wheel flange thickness for further analysis. The measurement system is fixed on the bogie frame. The fixture was designed using dimensions of the bogie and wheelset structure of the trains currently used by AALRTS. Laboratory experiments and computer simulations for of the electronic system were carried out to assess the feasibility of the data acquisition and analysis method. The noises and unwanted signals due to the dynamics of the system are filtered out from the sensor readings. The results show that the implementation of the proposed measurement system can accurately measure the wheel flange wear. Also, the faulty track section can be identified using the system recorded data and the operational control center data.
In this study, a novel hybrid annular radial magnetorheological damper (HARMRD) is proposed to improve the ride comfort of an electric vehicle (EV) powered by an in-wheel motor (IWM). The model primarily comprises annular-radial ducts in series with permanent magnets. Mathematical models representing the governing motions are formulated, followed by finite element analysis of the HARMRD to investigate the distribution of the magnetic field density and intensity of the magnetorheological (MR) fluid in both the annular and radial ducts. The optimized model generates a damping force of 87.3–445.7 N at the off-state (zero input current) with the excitation velocity ranging between 0 and 0.25 m/s. By contrast, the generated damping force varies from 3386.4 N to 3753.9 N at an input current of 1.5 A with the same velocity range as the off state. The damping forces obtained using the proposed model are 31.4% and 19.2% higher for the off-field and on-field states, respectively, compared with those of the conventional annular radial MR damper. The efficiency of the proposed model is evaluated by adopting two different vehicles: a conventional vehicle powered by an engine and an EV powered by an IWM. The simulation results demonstrate that the proposed HARMRD along with the skyhook controller significantly improves both the ride comfort and road-holding capability for both types of vehicles.
Pollutants in exhaust gases and the high fuel consumption of internal combustion engines remain key issues in the automotive industry despite the emergence of electric vehicles. Engine overheating is a major cause of these problems. Traditionally, engine overheating was solved using electric pumps and cooling fans with electrically operated thermostats. This method can be applied using active cooling systems that are currently available on the market. However, the performance of this method is undermined by its delayed response time to activate the main valve of the thermostat and the dependence of the coolant flow direction control on the engine. This study proposes a novel active engine cooling system incorporating a shape memory alloy-based thermostat. After discussing the operating principles, the governing equations of motion were formulated and analyzed using COMSOL Multiphysics and MATLAB. The results show that the proposed method improved the response time required to change the coolant flow direction and led to a coolant temperature difference of 4.90 °C at 90 °C cooling conditions. This result indicates that the proposed system can be applied to existing internal combustion engines to enhance their performance in terms of reduced pollution and fuel consumption.
A rapidly growing demand and shortage of electric energy require mankind to efficiently use it, recuperate and store it from the existing system, when possible, for further applications whenever the need arises. Electric trains figure among big energy consumers and among different railway transportation services; light rail transit trains are characterized by frequent stoppings to entrain and detrain passengers. In their operation, traction drives are made to keep on braking in order to meet their service requirements between closely spaced passenger stations. The modern service braking system used is regenerative braking, which acts as an electric energy generator during the braking period. The objective of this paper is to estimate the magnitude of regenerative energy that can be recuperated as a percentage of train energy consumption on East-West (Ayat to Tolhailoch) and West-East (Tolhailoch-Ayat) directions of Addis Ababa Light Rail Transit. Mathematical equations have been used to calculate the energy consumed between stations followed by the quantification of regenerative energy at each passenger station. Considering the current average running speed (24km/h) of the line, it resulted that 26.31% and 28.18% of energy consumption for East-West and West-East directions respectively are saved through regenerative braking energy recuperation. From the above results, it was observed that the magnitude of regenerative energy strongly depends on the speed at which the train is running and the efficiencies of inverter and traction induction motor.
The slipping of railway vehicle wheels during curve negotiation has been always a major problem in railway transportation. One of the causes of these slippages is predicted to be the lack of proper curve radius which incites high creepages. The creepages cause improper wheel rail interaction during curve negotiation. Most of the light rail transit system, with condensed population, there is a huge demand which increases the railway vehicles' weight to the maximum. However, this weight is again expected to have additional effects on the wheelset slipping when negotiating the curve or braking on a gradient curvature. Therefore, the aim of this paper is to model the anti-skid control of a railway vehicle in curved track operating in two instances: when the train is braking on a gradient curve and when the train is negotiating a curved track. To achieve this objective, the lateral dynamics equations of motion of the wheelset have been solved to predict the yaw angle and lateral displacements as well as their velocities. These quantities are used to calculate the creepages and creep forces. In return, they are input to the control model to limit the skidding. Computer simulations using MATLAB/ Simulink have been carried out to assess the feasibility of the control method. The results have used to design proper control systems that the rail network in congested environment are able to use. Antiskid control offers other benefits such as increasing the lateral comfort by reducing lateral forces and limiting noises generated by skidding in curvatures.
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