Introduction. The authors considered the problem of increasing the energy efficiency of an asynchronous drive, in particular, auxiliary electric machines of an electric locomotive. The publication continues the topic of optimal control of asynchronous machines from the past articles in No. 5, 2021 and No. 1, 2022 of the Russian Railway Science Journal.

Materials and methods. The calculation of the dynamic characteristics of an asynchronous drive used the SimInTech software of 3V Service, a Russian company, designed to simulate various applied problems. The SimInTech software package was used in the development of a mathematical model of the proposed system for optimal vector control of an asynchronous drive.

Results. The authors have found that the developed system of optimal control enables to reduce the current consumed by the asynchronous drive. These simulation modeling results confirmed that the adopted circuit solutions are correct.

Discussion and conclusion. The proposed system of optimal control of electric locomotive auxiliary machines is designed to improve the energy efficiency of the drive with a new algorithm for selecting the optimal value of the rotor flux linkage by reducing the current consumed by the drive. This vector control structure could be successfully implemented on the basis of modern microcontrollers.

Introduction. Today, ensuring stable train traffic remains relevant, particularly on the heavy traffic lines of the Russian Railways network. Solutions to this problem largely involve the development of polygon technologies based on harmonised use of the infrastructure, locomotive and car fleets. This requires the elimination of bottlenecks, which in the future would help increase service speed on long railway lines.

Materials and methods. Since service speed is an important quality indicator that identifies rail sections and lines with traffic obstruction, the authors applied the service speed method, in order to identify bottleneck sections and their causes.

Results. The authors consider the operating results of the double-track heavy traffic line of Koshta — Volkhovstroy-I of the Oktyabrskaya Railway, which joins sections with DC (Volkhovstroy-I — Babayevo) and AC (Koshta — Babayevo) electric traction. At the docking station, the authors assessed the impact of providing freight trains with locomotives on the service speed of loaded train traffic to the ports of the North-West, identified the bottleneck and analysed the transportation performance on the line under consideration. The authors propose a new method for reserving the locomotive fleet at docking stations of DC and AC railway sections, which enables to determine the necessary technological reserve of locomotives depending on the established service speed standard, given all operational changes in the organisation of transportation with full shortage compensation of locomotives.

Discussion and conclusion. The authors found that the bottleneck interferes with the steady traffic of loaded trains. In the area under study, this is due to infrastructural limitations of traction power supply. The authors consider options for strengthening the traction power supply system by harmonising AC and DC locomotive fleets. The proposed steps to eliminate the bottleneck would help achieve significant technological effects in the railway line operation.

Introduction. An urgent task today is to optimise the interaction between rolling stock and the railway track. A solution to it will increase train speed, enhance the safety and service life of wheels and rails. The service life of wheels and rails is under significant influence of contact stress and pressures. Their magnitude depends on the track geometry, including rail canting, contact spot and elastic properties of the contacting elements.

Materials and methods. The authors analysed the effects of rail canting on contact stress and pressure in the wheel – rail system at various loads from the rolling stock wheels, and assessed the effects of the underrail base elasticity on deformation and stress in the contact spot ignoring the force interaction between the track and the rolling stock when the overall stiffness of the track changes. Thus, this work sets the magnitude of the forces transmitted from the wheels of the rolling stock to the rails as the input data for determining the stress-strain state of the wheel – rail system. For the analysis, the authors developed a finite element model for calculating the stress-strain state of the wheel – rail system at various compaction degrees of the underrail base. The analysis of the obtained calculated data led to conclusions about the influence of the underrail base elasticity and the canting on the contact stresses and pressures in the wheel – rail system. The authors also assessed the effects of rail canting on the stress-strain state of the wheel – rail system for deviations from the standard position within the allowed limits.

Results. The calculation results show that the change in the underrail base elasticity has a weak effect on contact pressures and stresses (excluding the effect on the immediate force interaction of the rolling stock and the track). At the same time changes in the canting within the allowable values from 1/12 to 1/60 causes the contact stresses to exceed the yield strength of the rail steel, which, among other reasons, reduces the durability of the material and, as a result, reduces the service life of the rails, and, at the same time, increases the risk of brittle fracture in the area of extreme mechanical stress.

Discussion and conclusion. The obtained results of the calculation show that such a parameter of the rail track as canting requires control, since a change in the stress-strain state of the rails due to a change in canting affects their service life and traffic safety in general. It is suggested to automated and manual diagnostic tools to monitor this parameter.

Introduction. The new Rules for the perishable freight conveyance have changed the structure of freight flows towards higher volumes of transportation in special isothermal vehicles. When choosing them, the shipper should know the estimated period of transportation of perishable food, where the temperature of the latter would remain within the range of established transportation and storage temperatures.

Materials and methods. The calculation of the permissible transportation period uses the overall heat transfer coefficient of the body of a special vehicle determined by thermal tests using internal heating or cooling methods with mathematical dependencies that factor in the calculated change in the heat transfer coefficient during movement in train set.

Results. The authors calculated the permissible transportation period of bottled beer in a special isothermal vehicle in summer for permissible storage temperatures of perishable food from 0 to 10 °C in the range of average train speeds from 0 to 120 km/h. The calculation results show that the permissible transportation time with the heat transfer coefficient obtained in thermal tests amounted to 69.4 hours, and the calculation using external factors showed 57.1 hours, i. e. decreased by 12.3 hours, or approximately 18 %.

Discussion and conclusion. The permissible period of perishable freight conveyance in special isothermal vehicles depends on the average transportation speed and the infiltration of outside air and solar radiation into the vehicle. The shipper should consider these circumstances while selecting the parameters of special vehicles in order to prevent food from
deterioration or spoilage.

Introduction. The diesel air supply system is designed to increase the air supply to the piston part of the engine, which increases its power. The system includes a supercharging unit (turbocharger) and an aftercooler. As their connection with the piston part is gas-air, this limits the range of feasible operation of the diesel engine. In recent years, the development of the air supply system, which is contributed to the improvement of the fuel efficiency of the diesel engine, is aimed at increasing the turbocharger efficiency and expanding its feasible operation range. The article proposes a new way of improving the fuel efficiency of diesel locomotives: control of two supercharging units (registered supercharging) by successively switching on each for diesel operation in each of the two power modes — below and above average power.

Materials and methods. A diagram of the diesel engine air supply with a registered supercharging system is given, and a method for graph-analytical computation of the combined operation of supercharging units with the piston part of the engine is given.

Results. The authors substantiated and selected ways of increasing the fuel efficiency of diesel locomotives in operation by improving the characteristics of the air supply system at modes below average power. The calculation and experimental method gave an estimate of the increase in the fuel efficiency of a 2TE25K diesel locomotive equipped with a diesel engine with a registered supercharging system, compared with a standard 21-26DG diesel generator.

Discussion and conclusion. The practice of creating, researching and implementing registered supercharging systems at JSC Kolomensky Zavod and abroad shows that, despite the complexity of the design, such systems give a significant increase in the efficiency of the propulsion system in operation. It is recommended to check the characteristics of a diesel locomotive with the proposed registered air supply system on a bench diesel generator, followed by an operational check on a diesel locomotive.

Introduction. The article considers the determination of the impact velocities of empty and loaded Class 2 dangerous freight cistern cars on a gravity hump, the forces acting on the car through the automatic coupler, as well as the accelerations acting on the loading and unloading, safety valves and elements of the tank shell interior. Currently Class 2 dangerous freight cars with Classification Code 2112 and UN numbers 1011, 1965, 1969, 1978 could be shunted over the gravity hump only with a shunting locomotive, backing off with extreme caution, without jerks or sudden stops. This limitation prevents shunting gas cistern cars on automated gravity humps, which complicates shunting operations during train formation.

Materials and methods. Impact test of a cistern car alternately equipped with cushions of Classes T1, T2 and T3 with measurement of speeds, forces and accelerations.

Results. The maximum permissible impact velocities of the cistern car are determined.

Discussion and conclusion. According to the test results, as well as the GOST 32913–2014 requirements, the authors state that the implementation of the previously developed technology for shunting Class 2 dangerous freight cistern cars equipped with Class T3 draft gears on gravity humps, with a maximum approach speed of 3 km/h complies with shunting safety requirements.

Introduction. The aim is to study the formation and accumulation of contact-fatigue damage in a welded rail joint area and to determine the degree of influence of the presence and deformation behaviour of the rail tread surface on an electrically welded joint on the occurrence and development of contact-fatigue damage, including the number of cycles to crack formation, which determines the service life of the welded joint.

Materials and methods. In order to simulate the accumulation of contact-fatigue damage in the material surface under cyclical stress the authors take an approach that considers the peak values of the maximum shear stresses as an accumulation criterion. The following stages have been implemented as part of the given approach: determine the distribution of the probability density of wheel load on the rails; solve the contact problem of a rolling wheel considering the rail shape change in the collapse area; simulate the damage accumulation process.

Results. The collapse of the rail material in a welded rail joint area causes, on the one hand, an additional dynamic load that increases the contact and internal stresses, and on the other hand, increases the contact area due to the flattening of the rail head, which reduces contact stresses. Depending on the depth of collapse, initial damage, nature of loading, the accumulation of contact-fatigue damage can both accelerate and slow down.

Discussion and conclusion. It is confirmed that need for heat treatment to eliminate zones of reduced hardness in welded rail joint areas resulting in saddling, cracks and spalling. Reducing the weakened zone to the size of the contact spot will practically prevent the formation of impulse irregularities, and their formation upon contact would eliminate additional dynamic load. The problem may be solved by intensifying local heat treatment after welding, bandoning separate local heat treatment of rails after welding, and combining accelerated cooling of rail heads with the general welding process.

Introduction. Most modern bullet and high-speed electric trains are equipped with a Class II power actuator with stiff or elastic support of electric motors on the bogie frame. Both tractive motors on the bogies of electric trains of the Velaro platform and on the Sapsan High-Speed Electric Train are rigidly supported on the underpan, which is elastically connected to the bogie frame in the transverse direction by means of four leaf springs. Due to the low lateral stiffness of the suspension, when the train is moving, the underpan with the electric tractive motor makes transverse displacement relative to the bogie frame depending on the amount of free play of the underpan. This design acts as a dynamic shock absorber in a certain frequency range and contributes to an increase in the critical speed of the train.

Materials and methods. In order to evaluate the properties of the electric tractive motor transverse cushioning, the bogie frame was subjected to an amplitude-frequency analysis and a study of free and forced horizontal oscillations of the elastic and stiff suspension systems of the electric tractive motor on the bogie frame with the definition of probabilistic characteristics of random processes. For these purposes, a 3D simulation model of a motor car of a high-speed electric train has been developed in the Universal Mechanism software package. Numerical simulations gave realisations of stationary and ergodic random processes.

Results. The transverse cushioning of the electric tractive motor gives it the function of a dynamic shock absorber, has a positive impact on the stability of the cab at high speed, significantly reduces the amplitude and frequency of horizontal oscillations of the bogie frame, as well as frame forces. The maximum effect of dynamic damping is achieved at a natural frequency of transverse oscillations of the electric tractive motor, close to the frequency of transverse oscillations of the wheel pair.

Discussion and conclusion. The dynamic damping effect can be obtained within a certain range of the natural frequency of transverse oscillations of the electric tractive motor, depending on the parameters of the contact between the wheel and the rail, damping of the horizontal oscillations of the electric motor necessary to limit the resonant oscillation amplitudes. At the same time, the low stiffness of the suspension contributes to an increase in the transverse and angular displacement of the electric tractive motor. Permissible transverse and angular displacement require regulation depending on the characteristics of the gear clutch and the parameters of the undercarriage as a whole at the design stage of this design.