On the process of interaction of technical stations and hauls when passing train flows

The issues of traffic intensification on railway lines are always of high relevance. The throughput and carrying capacity of the railway line is determined by calculation on the basis of analytical dependencies, however, as in previous periods of the development of railway transport, currently, certain directions experience serious difficulties in passing train flows. At the same time, accepted calculated indicators of the throughput capacity of such lines do not allow to objectively determine the causes of difficulties in passing train flows and to develop the necessary solutions to overcome them. Railway infrastructure can be divided into several enlarged elements: sections, inlet and outlet necks of technical stations, pick-up and drop-off parks. This article does not consider power supply devices, locomotive facilities, performance of which changes less dynamically. Based on the research and experience in organizing the passage of train flows on one of the busiest railway lines of the Trans-Baikal Railway, the authors attempted to identify the main factors affecting the throughput and carrying capacity of freight-intensive directions, as well as to justify the need for integrated approaches in analyzing the throughput of a railway line with the interconnection of its main constituent elements and the definition of limiting. The article discusses in dynamics the interaction and mutual influence of the indicators of the main elements of the railway lines, as well as the analytical dependencies that allow to interlink the indicators that determine the throughput of individual elements of the railway line during their interaction. The results of analytical calculations are consistent with statistical indicators of the operation of railway lines in real operating conditions. With this in mind, significant dependencies between stages and technical stations were determined.

Study of climatic factors influence on the performance of pneumoshells securing freight during transportation by rail

The article provides the results of a computational study of the influence of external climatic factors (ambient temperature and atmospheric pressure) during the transportation of freights by rail on the performance of the pneumoshell as a means to secure unit and packaged freights in cars and containers. The preservation of the operability of the pneumoshells from the moment of installation to the moment of removal is determined by the need to maintain an excess pressure inside the pneumoshells not higher than the explosion pressure to prevent destruction of the pneumoshells and not less than zero to prevent its “collapse”.

The calculation formulas for the study were obtained according to the Mendeleev — Clapeyron equation. The examples show the dependence of the excess pressure in the pneumoshell on temperature at constant atmospheric pressure for pneumoshells with operating pressures of 0.20, 0.25, 0.30, 0.40, 0.55 and 0.69 bar when the ambient temperature changes from the initial at which the pneumoshell was pumped up to its limit values established by the current regulatory documents and possible when transporting through the territory of Russia. The examples also show the general dependence of the overpressure in the pneumoshell on temperature and atmospheric pressure for pneumoshells with operating pressures of 0.30 and 0.40 bar. Based on the results of computational studies, it is recommended to use pneumoshells with a working pressure of 0.30 bar in cases where freight is not transported by rail from low areas in the high-pressure region with temperatures lower than –30 °C, in these cases — the use of pneumoshells with working pressure of 0.40 bar and above. Taking into account the obtained maximum calculated values of the overpressure inside the pneumoshell, the pressure of the “explosion” of the applied pneumoshell should be at least 0.80 bar.

Technology and determination of the applicability of stone blowing at the current track maintenance

Grain composition of track ballast is in a narrow size range, which provides maximum volume of ballast voids of 30 – 60 mm for category 1 crushed stone, 25 – 60 mm for category 2 crushed stone with round sieves and 22.4 – 63.0 mm for category B crushed stone with square sieves. This range facilitates drainage and provides significant intra-ballast cavities for storing products of spalling and abrasion of particles of ballast material. All of these useful ballast functions are provided when the ballast is properly packed. The wider size range of ballast particles provides, in turn, increased strength and deformation resistance due to a denser arrangement of particles, but in this case the ballast has a smaller volume of voids. In the event of increased abrasion of the ballast, for example in the form of a shake, accompanied by the formation of fine particles (less than 0.01 mm), a decrease in the volume of the voids of the ballast prism can be critical for the drainage properties of the ballast. The article presents the test results of experimental technology for surfacing of the track ballast — surfacing with stone blowing carried out by specialists of the JSC “VNIIZhT” and the RUT MIIT (“Tracks and track facility” Department) in 2018. In October 2017 comparative tests of surfacing for under-sleeper pads and stone blowing were carried out under the conditions of the Test Ring of the JSC “VNIIZhT” which is close to the actual operating conditions. Then, three sections were laid in the operational area of the Test Ring — two tested (with surfacing for under-sleeper pads and stone blowing) and one reference. The need to continue researching exactly the stone blowing technology arose due to the fact that in October 2017, due to climatic conditions (air temperature fluctuations to negative values), it was not possible to obtain force track profiles and clarify the migration factors of blown crushed stone into track ballast. The test results confirmed the effectiveness of track surfacing with a stone blowing process. The use of new equipment allows improving this surfacing technology. As part of the tests, it was possible to find ways to counteract the migration of blown crushed stone into track ballast.

Switchable filter compensating installation in AC traction network

In the AC traction network, the use of adjustable transverse capacitive compensation systems has become necessary primarily for normalizing the voltage at the current collector of the electric rolling stock. Currently, static reactive power generators are used at the sections of the traction network, which have proved their effectiveness in increasing and stabilizing the voltage level, as a result of which the railway capacity is increased. This article substantiates the necessity and expediency of the inclusion of adjustable transverse capacitive compensation installations at sectioning posts in AC traction networks to normalize the voltage at the current collector of electric rolling stock, and therefore, increase the throughput capacity of railway sections. It is shown that, in modern conditions, it is expedient and economically justified to modernize existing unregulated installations with transferring them to a controlled mode by introducing an additional subsequently connected second section of capacitors, which is automatically shunted by the switching device at high loads in the traction network. Modernized installation, proposed by the authors and called switchable, has been successfully operating on the Gorky Railway for more than 6 years. A description of the proposed installation is given and the results of a theoretical analysis of transients during shunting and unloading of the additional section are presented. An algorithm for switching the proposed installation is given. It is shown that the additional section should be shunted at a time when the voltage across the capacitors is zero. Theoretical and experimental oscillograms of switching processes are presented. Recommendations are given for choosing thyristors for a controlled key, as well as recommendations for improving the reliability of the proposed installation.

On the influence of external factors on the heat transfer coefficient of the body of a specialized vehicle for the transportation of perishable freight

Satisfying the needs of the population in the delivery of perishable freight of good quality largely depends on the stable operation of specialized vehicles and the accuracy of calculating the deadline for transporting freight to the consumer. The main value used to calculate the deadline for the transportation of perishable freight by rail is the heat transfer coefficient of the body of an insulated car or container. The accuracy of estimating this value is especially important when using isothermal cars or containers that are not equipped with cooling or heating systems as specialized vehicles. In this paper authors assess the influence of some external factors on the value of the heat transfer coefficient of the body of an isothermal vehicle. The change in the heat transfer coefficient due to the influence of the speed of the isothermal vehicle and insolation is taken into account. The heat transfer coefficients from the internal and external building envelopes to the ambient air for the standing car and during its movement are determined to assess the change in the heat transfer coefficient from the criterion dependencies. Taking into account real external factors, in particular outdoor temperature, humidity, train speed, significantly affects the heat transfer coefficient of the body of an isothermal vehicle, the value was determined in stationary conditions of the workshop and underlying the calculation of the maximum permissible terms for the transportation of perishable freights. This value is excellent from the actual value. As a result of the calculations, a discrepancy of the value of the deadline for the transportation of perishable freights in comparison with the current method is 3–10 %. Changes to the existing methodology will reduce the risk of delivery of perishable freight of inadequate quality due to incorrectly calculated deadlines for transportation.

Study of electromagnetic processes in the system “contact network — electric locomotive” while reducing the minimum opening angle of the thyristors in the rectifier-inverter converter

A new method is proposed for increasing the power factor of an electric locomotive by changing the minimum opening angle of thyristors α0 of a rectifier-inverter converter. The decrease in the angle α0 is due to changes in both the structure of the transducer and the zone of its regulation. A pulse synchronization device has been developed that makes it possible to generate pulses with strong distortions of the mains voltage Uc at the points of natural transition of the voltage of the fundamental frequency Uс through the zero line. Based on this device, an α0 pulse-forming device was developed that eliminates the influence of pre- and post-switching voltage fluctuations. A “contact network — electric locomotive” model was created in the environment of MatLab/Simulink, taking into account the nonlinearity of the longitudinal parameters of the contact network. The effect of decreasing the angle α0 on the character of pre- and post-switching voltage fluctuations was analyzed, and the parameters of transient processes were calculated. Particular attention was paid to modeling the parameters of traction network. The primary network parameters adopted in the model correspond to theoretical parameters for the selected type of contact suspension. Their high convergence is confirmed by the calculation of the coefficient of determination R2. Calculations on the “contact network — electric locomotive” model show that compared with the standard scheme of the electric locomotive, where the minimum opening angle of the thyristors is α0 = 9° el., the decrease in the angle α0 to 4.5° el. leads to an almost twofold decrease in the amplitude of pre-switching voltage fluctuations and a small decrease in the amplitude of post-switching voltage fluctuations. The model results indicate that a decrease in the minimum thyristor opening angle α0 leads to an increase in the power factor of the electric locomotive.

Study of the functional diagram and algorithm of tracking system for electrodynamic braking of DC electric train

One of the key ways to save operating costs in suburban traffic on lines electrified with direct current is to increase the return of electric energy when the drivers use the regenerative braking mode. Electrodynamic braking control systems that track the magnitude of the voltage of the contact network can increase the percentage of return of electric energy from the use of regenerative braking due to the rapid redistribution of energy generated by traction motors. Similar systems (the so-called tracking systems) are used on DC electric trains with an asynchronous traction drive. In this work, authors analyzed an electrodynamic braking system for a DC electric train with a collector traction drive, which regulates the recovery current by changing the resistance of the braking resistor, and the armature current due to the magnetic flux of the motors. Characteristics of the pulse braking resistance controller for the current settings of the 250 and 350 A armature were calculated. Functional diagram of the tracking system with a description of its individual elements is developed. On a simulation model, electromagnetic processes in the power circuit of an electric train were studied with a changing current consumption. Based on the analysis of the model results, the ability of the tracking system to regulate the armature current with full absorption of electricity by the consumer is shown. The article provides the refined algorithm for the transition of the servo system from the mode of regenerativerheostatic braking to rheostatic with excessive generation of electricity. The developed algorithm of the tracking system provides a stable implementation of the braking force in the entire range of speeds and at various levels of consumption of generated electricity. A rheostatic braking circuit with stabilization of the maximum value of the excitation current at low speeds is proposed.