MODELLING THE INTERACTION BETWEEN RAILWAY WHEEL AND RAIL

Transport ◽  
2008 ◽  
Vol 23 (3) ◽  
pp. 236-239 ◽  
Author(s):  
Stasys Dailydka ◽  
Leonas Povilas Lingaitis ◽  
Sergey Myamlin ◽  
Vladimir Prichodko
Keyword(s):  
Mathematical Model ◽  
Operating Conditions ◽  
Rolling Stock ◽  
Dynamic Processes ◽  
Running Speed ◽  
Railway Wheel ◽  
The Real ◽  
The Impact ◽  
Railway Rolling Stock

The article presents a mathematical model for assessing the real operating conditions of railway rolling stock, taking into account the situations when the wheel loses contact with rail. The obtained amplitudinal fluctuation characteristics depend on the set roughness function and the running speed of the wheel. When calculating dynamic processes, the contact between wheel and rail should be considered unstable. With the increase of speed, the impact of this instability increases.

scholarly journals NECESSITY TO IMPROVE THE MATHEMATICAL MODEL OF FREIGHT CARS TO STUDY CASES OF ITS DERAILMENTS

2020 ◽  
pp. 442-451
Author(s):  
А.V. Batig ◽  
A. Ya. Kuzyshyn
Keyword(s):  
Mathematical Model ◽  
Mathematical Models ◽  
Computer Experiment ◽  
Rolling Stock ◽  
Software Systems ◽  
Freight Car ◽  
The Stability ◽  
The Many ◽  
The Impact ◽  
The Mathematical Model

One of the most important problems that pose a serious threat to the functioning of railways is the problem of freight cars derailment. However, according to statistics, the number of cases of the derailments of freight cars in trains annually grows. Тo prevent such cases, the necessary preventive measures are developed, and to study the causes of their occurrence, a significant number of mathematical models, programs and software systems created by leading domestic and foreign scientists. Studies of such mathematical models by the authors of this work have led to the conclusion that they are not sufficiently detailed to the extent that it is necessary for analyze the reasons of its derailment. At the same time, an analysis of the causes of the rolling stock derailments on the railways of Ukraine over the past five years showed that in about 20 % of cases they are obvious, and in 7 % of cases they are not obvious and implicitly expressed. The study of such cases of rolling stock derailment during an official investigation by the railway and during forensic railway transport expertises requires the use of an improved mathematical model of a freight car, which would allow a quantitative assessment of the impact of its parameters and rail track on the conditions of railway accidents. Therefore, taking into account the main reasons that caused the occurrence of such railroad accidents over the last five years on the railways of Ukraine, the article selected the main directions for improving the mathematical model of a freight car, allowing to cover all the many factors (explicit and hidden) and identify the most significant ones regarding the circumstances of the derailment rolling stock off the track, established on the basis of a computer experiment. It is proposed in the mathematical model of a freight car to take into account the guiding force, the value of which is one of the main indicators of the stability of the rolling stock. The authors of the article noted that not taking into account the influence of the guiding forces on the dynamics of the freight car can lead to an erroneous determination of the reasons for the rolling stock derailment or even to the impossibility of establishing them.

scholarly journals Generalization of research results on the dynamics of continuous wide-strip hot-rolling mills

2018 ◽  
pp. 275-289
Author(s):  
V.V. Verenev
Keyword(s):  
Mathematical Model ◽  
Hot Rolling ◽  
Large Data ◽  
Dynamic Processes ◽  
Technological Parameters ◽  
Rolling Moment ◽  
Rolling Mills ◽  
Wide Strip ◽  
The Impact ◽  
First Time

The aim of the work is to summarize the results of experimental-industrial and theoretical studies of dynamic processes in wide-strip hot rolling mills 1680, 1700, 2000 and 2500. We describe the methods of collecting, storing, identifying, visualizing and mathematical processing of large data arrays, which made it possible to establish new laws and correlations of technological parameters. New results related to the peculiarities of transient processes, their patterns and the use of the latter for the purpose of diagnosing technology and equipment condition are presented. Vibrodynamic processes are described when the strip is captured by the rollers. For the first time, a correlation between the maximum peak moment when the strip is captured and the static rolling moment on the 1680 mill is obtained and substantiated by measuring and statistical modeling. A new mathematical model of the roll line is developed, incorporating the equations of dynamic processes in gears and axles of the gearbox. For the first time, the dynamics of the formation of intercellular tensions in the process of sequential filling and release with a 6-cell band is shown. A complete mathematical model and a computer program for the dynamic interaction of six-group stands of a rolling strip have been developed. A new line of research has been proposed, which includes the search, substantiation and testing of new methods and methods for diagnosing the technical condition of rolling mills based on the use of transients and their parameters in various modes of equipment operation. Proposed and tested in industrial conditions at the mills 1680 and 1700-M are effective ways to reduce the impact loads during the period of the strip capture by the rollers.

Geometrical Effects of Channel Configuration on the Performance of Membraneless Fuel Cells

2017 ◽  
Author(s):  
Hector Gomez ◽  
Usama Tohid ◽  
Arturo Pacheco-Vega
Keyword(s):  
Mathematical Model ◽  
Fuel Cell ◽  
Stokes Equations ◽  
Single Channel ◽  
Numerical Data ◽  
Operating Conditions ◽  
Straight Channel ◽  
Wavy Channel ◽  
Channel Configuration ◽  
The Impact

In this study, numerical simulations were performed to find the current-voltage distribution for a laminar flow-based membraneless fuel cell (LFFC). The system uses formic acid and oxygen as the fuel and oxidant, respectively, and has a Y-shaped geometry with two separate inlets that merge into a single channel. The main objective of this work is to analyze the impact of geometry and operating conditions on the performance of these devices. This is done by proposing a novel wavy-channel-based geometry for the side walls, along with planar top and bottom walls, and comparing the behavior of the corresponding system to that of LFFCs based on straight-channel walls. Special attention is placed on the effect of both the amplitude of the sinusoid and its wavelength on the performance of the device. The effect of flow rates — in the range of [200, 350] μL/min — is also studied. The mathematical model is formulated by considering the Navier-Stokes equations along with Butler-Volmer and Fick’s law. For each fuel-cell configuration, the governing equations are discretized and solved using finite elements, and the solutions given in terms of the polarization curves. The model was first verified using published numerical data for a straight-channel-based LFFC. The simulations show that the performance achieved by the device, based on the proposed wavy channel geometry, is slightly better than that of the LFFC with straight channel walls. On the other hand, higher flowrates significantly improve the power density of the device. Although the current mathematical model may be useful in a variety of applications, improvements on it are currently underway to account for the effects of potential distributions on ions within the flow channel, and results from it will be reported in the future.

A Mathematical Model and Performance Evaluation for a Single-Stage Grid-Connected Photovoltaic (PV) System

2008 ◽  
Vol 9 (6) ◽  
Author(s):  
Prajna Paramita Dash ◽  
Amirnaser Yazdani
Keyword(s):  
Mathematical Model ◽  
Control Strategy ◽  
Voltage Control ◽  
Current Control ◽  
Operating Conditions ◽  
Single Stage ◽  
Control Loop ◽  
Pv System ◽  
Wide Range ◽  
The Impact

This paper proposes a control strategy for important transients of a single-stage, three-phase, PV system that is connected to a distribution network. The proposed control strategy adopts an inner current-control loop and an outer DC-link voltage control loop. The current-control mechanism renders the PV system protected against external faults, enables control of the DC-link voltage and, therefore, controls/maximizes the PV system power output. The paper also proposes a feed-forward compensation strategy for the DC-link voltage control loop to mitigate the impact of the nonlinear characteristic of the PV array on the closed-loop stability, and to permit design and optimization of the DC-link voltage controller for a wide range of operating conditions. A mathematical model and a control design methodology are presented for the PV system, and it is shown that under the proposed control, the PV system fulfills the operational requirements of a grid-connected PV system. The effectiveness of the proposed control strategy and the most important transients of the PV system are evaluated through simulation studies conducted on a detailed switched model of the PV system in the PSCAD/EMTDC software environment.

scholarly journals Influence of the axial loads of rolling stock on the contact-fatigue life of rails

2018 ◽  
Vol 77 (3) ◽  
pp. 149-156 ◽  
Author(s):  
V. S. Kossov ◽  
G. M. Volokhov ◽  
O. G. Krasnov ◽  
M. N. Ovechnikov ◽  
A. L. Protopopov ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Contact Fatigue ◽  
Calculated Data ◽  
Operating Conditions ◽  
Rolling Stock ◽  
Axial Loads ◽  
Rolling Surface ◽  
Contact Fatigue Life ◽  
The Impact

Analysis of operational data for defective and highly defective rails showed that up to 25 % is the contact-fatigue defects. In connection with the development of heavy haul traffic on the Russian railways, it is relevant to determine the influence of cars with increased axial loads of 25 and 27 tf on the contact fatigue life of rails. The solution of this problem is set forth in this article. The Brown-Miller model of multi-axial fatigue was used in the calculation. This model is integrated into the Fatigue software system, which is tied to the Marc calculation system through Pat-ran. Since under operating conditions the wheel moves (rolls) along the rail on meandering trajectory, in computer modeling weight coefficients were taken into account that characterize the percentage of wheels in the cross-sectional areas of the rail. Calculations of contact fatigue life took into account the variability of vertical loads from the impact on the track of trains formed from innovative open cars with axial loads of 23.5, 25 and 27 tf under operating conditions, loaded with real loading blocks. According to the analysis of calculated data with an increase in axial loads from 23.5 to 25 tf, it is necessary to expect a decrease in the service life of rails in contact fatigue resistance by 19 %, with a further increase in axle loads of up to 27 tf per 32 %. Considering that the share of freight cars with axial loads of 25 tf does not exceed 15...20 %, then on the routes of its use the service life of rails should be expected to decrease by 3...4 %. The method proposed by the authors for predicting the contact fatigue life of rails with increasing axial loads is advisable to improve in part of the experimental determination of the fatigue and strength characteristics of rail steel from the degree of hardening of the rolling surface, its probabilistic properties and the use of the integral distribution law for vertical forces, taking into account the structure of the freight traffic passing through the section. The work was carried out according to the RFBR project 17-20 01088.

scholarly journals PRINCIPLES OF CONSTRUCTION OF THE GENERALIZED MATHEMATICAL MODEL OF THE HYDRAULIC EXTINGUISHER OF OSCILLATIONS OF THE PASSENGER CAR

2021 ◽  
Vol 1 (38) ◽  
pp. 173-184
Author(s):  
I. Shcherbyna
Keyword(s):  
Mathematical Model ◽  
Operating Conditions ◽  
Working Fluid ◽  
Operating Parameters ◽  
Hydraulic Systems ◽  
Passenger Cars ◽  
Passenger Car ◽  
Periodic Movement ◽  
Depth Analysis ◽  
The Impact

The study of the processes associated with the use of working fluids in the elements of hydraulic drives was preceded by studies of the unsteady periodic movement of the working fluid in the pipelines of hydraulic systems. Such processes take place in hydraulic drives and their elements, and are associated with the compressibility of the working fluid. The stability of the operation of hydraulic valves, which are supplied to hydraulic systems in order to maintain, within the required limits, pressures or flow rates, is also largely predetermined by non-stationary hydro mechanical processes occurring in the pipelines of these systems, channels and chambers of hydraulic devices. The peculiarities of the working processes of passive vibration dampers of passenger cars include the interaction of the working fluid with moving parts and its flow through the channels and through the calibrated holes with local artificial resistance. For in-depth analysis of changes in operating parameters, it is necessary to use a mathematical model that should reflect the processes that occur during the operation of the hydraulic device. In the presented article the generalized mathematical model of the hydraulic damper of fluctuations of the passenger car of the НЦ-1100 type is developed. This model takes into account the special operating conditions of the hydraulic shock absorber, which allows you to study the impact of operating parameters on the performance of the device.

On the Extrapolation of Rim Sealing Performance From Test Bench to Real Engine: A Numerical Survey

2021 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Cosimo Bianchini ◽  
Lorenzo Mazzei ◽  
Alessio Bonini ◽  
Luca Innocenti ◽  
...  
Keyword(s):  
Test Bench ◽  
Flow Path ◽  
Operating Conditions ◽  
Turbine Wheel ◽  
General Application ◽  
The Real ◽  
Sealing Performance ◽  
Alternative Approach ◽  
Effectiveness Prediction ◽  
The Impact

Abstract The main annulus hot gas ingress into turbine wheel-spaces is still one of the most challenging problem designers face. During the decades, several experimental test benches were developed worldwide to improve the knowledge associated to the rim seal flow physics. Even if in some cases quite complex and advanced rig configurations were proposed, limitations in the operating conditions and in the reproduction of the real engine geometries/characteristics into the rig are present. In this paper, validated CFD computations are used to explore the impact of some experimental rigs design choices/limitations on the sealing effectiveness prediction and their ability to mimic the real engine configuration behaviour. Attention is paid on several test rig related aspects such as operating conditions, flow path configuration (blade and vane count) and accuracy in the real engine rim seal geometry reconstruction applied to the rig. From the computations it emerges that a scaled geometry operated at lab conditions is able to mimic pretty well the real engine sealing performance when rig and engine experience the same flow path ΔCp. The ability of the rig to match the engine data is not affected by the differences in main annulus Mach number between test bench and engine. A further result that emerges from the computation regards the fact that the Φ0 - ΔCp0.5 curve is not linear, proving that the linear extrapolation of rim sealing performance from test bench to real engine when rig and engine are characterized by different ΔCp0.5 values is not of general application and an alternative approach is given. Finally, it is found that the impact of vane count on the rim sealing effectiveness is significant, making the extrapolation of data from rig to engine difficult.

Mathematical model of railway rolling stock with elastically deformed automatic couplers in starting moment of movement

2021 ◽  
pp. 26-31
Author(s):  
Igor Pavlovich Popov ◽  
Keyword(s):  
Mathematical Model ◽  
Rolling Stock ◽  
Railway Rolling Stock

The paper presents a mathematical model of movement start of railway rolling stock with elastic automatic couplers. It shows that starting of a heavy-loaded train equipped with elastically deformed automatic couplers occurs significantly easier in comparison with non-deformable ones, and the more cars are in the train, the higher this advantage is. Essentially, it is stipulated by the substitution of simultaneous start of cars movement on alternating. In order to exclude longitudinal fluctuations of the train after reaching maximal stretch of the automatic coupler it is necessary to block the possibility of the harmonic compression mechanically.

Pantograph cooling system mathematical model during motion of the railway electric transport

2020 ◽  
pp. 86-92
Author(s):  
Valeriy Viktorovich Tomilov ◽  
◽  
Sandugash Myrzabekovna Utepbergenova ◽  
Oleg Alexeevich Sidorov ◽  
◽  
...  
Keyword(s):  
Mathematical Model ◽  
Thermal State ◽  
Cooling System ◽  
Rolling Stock ◽  
Contact Network ◽  
Electric Transport ◽  
Three Dimensional Model ◽  
Standard Design ◽  
Uneven Heating ◽  
The Impact

Uneven heating of the pantograph slide is the reason for limiting the pantograph removal of the maximum permissible long-term current from the contact network. The highest heating point is observed in the center of the pantograph head relative to the path axis, which can be taken into account when developing a pantograph slide cooling device. Existing models of the thermal state of the pantograph slide do not describe the transient modes of distributed heating of a closed-type structure (euro pantograph head) as a result of the impact of a contact wire in the plan when moving a rolling stock. Existing methods for calculating the heating of the pantograph slide require the use of special programs for the development of its three-dimensional model and significant power of electronic computers. The paper presents a mathematical model euro pantograph head standard design and are equipped with passive cooling system the center through the frame device of the confuser type, which can calculate the load characteristics of the pantograph slide, to evaluate the reduction of uneven heating of its design and to determine the maximal permissible continuous current of the pantograph.

scholarly journals INFLUENCE OF LATERAL DISPLACEMENT OF BOGIES ON THE FREIGHT CAR DYNAMICS

2021 ◽  
pp. 66-81
Author(s):  
A. O Shvets
Keyword(s):  
Mathematical Model ◽  
Lateral Displacement ◽  
Operating Conditions ◽  
Movement Speed ◽  
Rolling Stock ◽  
Transverse Displacement ◽  
Resource Saving ◽  
Freight Car ◽  
Curved Track ◽  
Dynamic Indicators

Purpose. The work is aimed at determining the influence of the lateral displacement of a freight car bogie, taking into account the value of the movement speed on its main dynamic indicators and interaction indicators of the rolling stock and the track. Methodology. The quantitative assessment of dynamic indicators was obtained by the method of mathematical and computer modeling. The design scheme of the car takes into account the interaction peculiarities of cars as part of the train: the possibility of all modes of body vibration in space, the transmission of longitudinal force from neighboring cars in vertical and horizontal directions, taking into account the technical condition of individual parts of the car and their design features, as well as various operating conditions. Findings. During the research, a mathematical model of a coupling of five freight cars was applied to study the dynamic loading of a gondola car and a track. Main dynamic and interaction indicators of the rolling stock and the track in case of transverse bogie displacement when moving along curved track sections assessment were assessed. The maximum possible values of the lateral displacement of the freight car bogie were substantiated. Originality. The mathematical model of the coupling of freight cars in the train has been improved. In the calculation schemes describing the vibrations of the cars, the peculiarities of the freight car bogies, lozenging of the bogie side frames are taken into account. The model makes it possible to study the effect of changing rotation angle of the central axis of the car body, which in turn leads to the lateral displacement of bogies relative to each other, on the main dynamic and interaction indicators of the rolling stock and the track. For the first time, the influence of transverse displacement of the bogie was investigated, taking into account the wear of its parts and assemblies when moving on track sections with unevenness. Practical value. The calculation results can be used to assess the influence of the bogie transverse displacement on the dynamic qualities of the rolling stock and interaction indicators of the rolling stock and the track, taking into account the wear of parts and units of the bogie when moving in straight and curved track sections with irregularities. The application of the results obtained will contribute to an increase in the stability of freight rolling stock in the conditions of increasing travel speeds, which in turn will allow developing technical conditions for the implementation of resource-saving technologies for transporting goods that meet the safety requirements of train traffic.

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