Icing influence analysis method for electrified railway contact line

Abstract

The invention discloses an electrified railway contact line icing influence analysis method, which comprises the following steps of: obtaining key parameters such as a collision coefficient and a freezing coefficient of a water drop and a contact line in an icing calculation process by analyzing a line surrounding flow field of an overhead line system and researching heat balance of the surface of the contact line; and meanwhile, carrying out grid analysis on environmental parameters and icing boundaries so as to establish a time-varying meteorological numerical model of the contact line. By means of a contact line icing numerical model, the influence of the temperature (T), the liquid water content (LWC), the median volume diameter (MVD) and the wind speed (Vp) on contact line icing evolution is analyzed through a control variable method. Therefore, an important basis is provided for contact line icing prediction, ice prevention and ice removal in the future.

Description

Technical Field

[0001] The present invention relates to the field of data analysis, and in particular to a method for analyzing the impact of icing on an electrified railway contact line. Background Art

[0002] As the carrier of electric energy transmission for trains, the contact line of electrified railways is affected by factors such as contact line tension and the sliding electrical contact condition of the catenary. The limit of ice coverage on its surface is very small, and traditional ice detection methods, such as weighing method and tilt angle method, are difficult to apply. The weighing method is greatly affected by environmental factors such as wind speed and temperature, which may lead to measurement errors. The current weighing method calculation model is mainly based on static analysis, but it fails to fully consider the influence of wind load and has poor applicability under certain special conditions. The ice coverage of the contact network is usually non-uniform, which makes it difficult for the traditional tilt angle method to accurately reflect the actual ice thickness and distribution. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for analyzing the impact of icing on contact lines of electrified railways.

[0004] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0005] An analysis method for the impact of ice coating on an electrified railway contact line comprises the following steps:

[0006] S1. Build time-varying grid division according to the changes of environmental parameters and ice boundary, and perform flow field analysis and grid analysis on the contact line surface;

[0007] S2, updating the grid according to the parameters after the initial icing, and establishing a numerical model of contact line meteorological time-varying icing based on the updated grid;

[0008] S3. Based on the established numerical model of contact line meteorological time-varying icing, the control variable method is used to analyze the factors affecting icing.

[0009] Furthermore, the specific method of performing flow field analysis on the contact surface in S1 is:

[0010] S11, obtaining the water droplet velocity and the collision coefficient between the water droplet and the contact line;

[0011] S12, calculating the freezing coefficient according to the heat balance equation;

[0012] S13, based on the water droplet velocity in S11, the collision coefficient between the water droplet and the contact line, and the freezing coefficient in S12, the ice mass per unit time is calculated to complete the ice calculation.

[0013] Furthermore, the heat balance equation in S12 is expressed as:

[0014] q i +q v =q c +q e +q l +q s

[0015] In the formula, q i is the latent heat released by freezing of supercooled droplets per unit length of the icing object; q v The friction between the airflow and the ice-covered structure generates heat; q c is the heat loss on the surface of the icing object caused by convection heat transfer; q e The heat absorbed by the evaporation and sublimation of water on the ice surface; q l The heat absorbed by raising the temperature of the supercooled droplets attached to the surface of the icing object to the reference temperature; q s It is the heat loss caused by radiation from the surface of ice-covered conductor.

[0016] Furthermore, the specific calculation method of the ice mass in S13 is:

[0017]

[0018] In the formula, α 1 is the local collision rate of water droplets; α 2 is the water drop collection coefficient, generally taken as 1; α 3 is the droplet freezing coefficient; LWC is the atmospheric liquid water content; v p is the velocity of water droplet impacting the wire; L c is the surface length of the micro-element control body on the ice-covered conductor; L is the unit conductor length.

[0019] Furthermore, the S2 specifically includes the following steps:

[0020] S21, updating the grid according to the parameters after the initial icing, inputting the contour points of the icing surface after the contact line is iced, defining the geometric area boundary and the grid parameters, and completing the icing grid update in a loop;

[0021] S22, after the grid is updated, flow field analysis is performed to calculate the collision coefficient and collision angle, and the state water content, wind speed, median diameter of water droplets, ice-covering time, and ambient temperature are set respectively, and the secondary ice-covering mass is calculated to generate an ice-covering contour curve;

[0022] S23, combining the ice coverage contour curve with the updated grid to obtain a new grid for the next ice coverage and repeating steps S21-S22 to complete the construction of the contact line icing meteorological time-varying numerical model.

[0023] Furthermore, the control variable method used in S3 to analyze ice influencing factors specifically includes monotonicity level analysis, sensitivity level analysis and state tracking capability analysis.

[0024] Furthermore, the specific calculation method of the monotonicity level is:

[0025]

[0026] In the formula, β i is the monotonicity level, D i is the sum at time point i, t j ,t k are the characteristic values ​​of the ice state at the j-th and k-th time points respectively, and j,k∈[1,n], n is the total number of characteristic points, and sgn() is the sign function.

[0027] Furthermore, the specific calculation method of the sensitivity level is:

[0028]

[0029] Where η i is the state tracking ability, median is the median, t j ,t k are the characteristic values ​​of the ice state at the jth and kth time points, respectively; d(j) and d(k) are the characteristic values ​​of the ice state of the characteristic sequence before and after the jth and kth time points.

[0030] Furthermore, the specific calculation method of the state tracking capability is:

[0031]

[0032] In the formula, Z i is the state tracking capability, β i is the monotonicity level, η i The sensitivity level is medium.

[0033] The present invention has the following beneficial effects:

[0034] In order to study the contact line icing, a numerical simulation model of the contact line meteorological time-varying icing was built, and the icing characteristics of the contact line were obtained.

[0035] The state tracking capability was derived through the analysis of monotonicity and sensitivity. The effects of four factors, namely ambient temperature, liquid water content, median volume diameter and wind speed, on the evolution of contact line icing were studied. The influence of key influencing factors on contact line icing was discovered, which will be helpful for future anti-icing and de-icing research. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1The present invention is a flow chart of the method for analyzing the impact of icing on the contact line of an electrified railway. DETAILED DESCRIPTION

[0037] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0038] A method for analyzing the impact of ice coating on contact wires of electrified railways. Figure 1 As shown, the following steps are included:

[0039] S1. Build time-varying grid division according to the changes of environmental parameters and ice boundary, and perform flow field analysis and grid analysis on the contact line surface;

[0040] According to the changes in environmental parameters and ice boundaries, a time-varying grid is constructed, that is, the division of regional grids and boundary grids. Then, the flow field analysis is performed on the contact line surface to obtain key ice parameters such as the water droplet velocity and the collision coefficient between the water droplet and the contact line. The freezing coefficient is then obtained based on the heat balance equation. The ice mass per unit time is calculated by combining the above parameters to complete the ice calculation. The heat balance equation that plays a key role in the calculation of the freezing coefficient is as follows:

[0041] q i +q v =q c +q e +q l +q s (1)

[0042] Where: q i is the latent heat released by freezing of supercooled droplets per unit length of the icing object; q v The friction between the airflow and the ice-covered structure generates heat; q c is the heat loss on the surface of the icing object caused by convection heat transfer; q e The heat absorbed by the evaporation and sublimation of water on the ice surface; q l The heat absorbed by raising the temperature of the supercooled droplets attached to the surface of the icing object to the reference temperature; q s is the heat loss caused by radiation on the surface of the ice-covered conductor. In addition, the adhesion coefficient is solved using the approximate calculation formula as shown in formula (2).

[0043]

[0044] Where: α 2 is the adhesion coefficient; v is the wind speed.

[0045] S2, updating the grid according to the parameters after the initial icing, and establishing a numerical model of contact line meteorological time-varying icing based on the updated grid;

[0046] Then, the secondary calculation of the icing model is carried out, and the grid is updated according to the parameters after the initial icing. In order to keep the model generating speed and good fit after the icing boundary is updated, the non-structured grid generated by the propulsion wave is used. The closer to the contact line, the higher the grid density. The grid update mainly inputs the contour points of the icing surface after the contact line is iced, and then defines the geometric area boundary, and then defines the grid parameters, so as to complete the dynamic update of the icing grid in a cycle. After the grid is updated, the flow field analysis is continued with Fluent software, and then the data generated by Fluent software is read with MATLAB software to solve the collision coefficient and collision angle.

[0047] Collision coefficient:

[0048]

[0049] Where dy is the difference in the initial ordinate before the water droplet hits the wire, dL is the surface length between the upper and lower limits after the water droplet hits the wire, and α 1 is the collision coefficient.

[0050] Collision Angle:

[0051]

[0052] Where y is the ordinate of the collision point, x is the abscissa, and θ is the collision angle.

[0053] Then set the liquid water content, wind speed, median diameter of water droplets, ice-covering time, and ambient temperature respectively, complete the calculation of the secondary ice-covering mass through the code, and generate the ice-covering contour curve. Combine the ice-covering curve with the previous ice-covering grid to obtain a new grid for the next ice-covering, and then import the grid into Fluent for the next ice-covering calculation. Finally, the above steps are repeated continuously to realize the automatic iteration of the ice-covering model, thereby building a dynamic contact line ice-covering meteorological time-varying numerical model.

[0054] S3. Based on the established numerical model of contact line meteorological time-varying icing, the control variable method is used to analyze the factors affecting icing.

[0055] The dynamic evolution of the ice characteristics of the contact line is uncertain and nonlinear. In order to quantitatively track the evolution of ice characteristics, the sensitivity and monotonicity of the median diameter of water droplets, wind speed, ambient temperature, and liquid water content to the changes in ice profile are analyzed, and finally the state tracking capability is obtained. i =(t 1,t 2 ,…,t n ) to conduct state tracking analysis, and the specific calculation method is as follows:

[0056] Monotonicity level

[0057] t 1 , t 2 ,…,t n is the characteristic sequence T i The eigenvalues ​​at time points 1, 2, ..., n are calculated using equation (3) for monotonic statistics.

[0058]

[0059] In the formula, sgn is the sign function, and the monotonicity level of the feature sequence is calculated as shown in (4).

[0060]

[0061] Sensitivity level

[0062] With the characteristic sequence T i t 1 is the initial state characteristic of ice cover, and the calculation method of characteristic sequence sensitivity level is shown in formula (5).

[0063]

[0064] median is the median, d(j) and d(k) are the characteristic sequence T i The RMS of the eigenvalues ​​before and after time j and k represents the growth process of the feature sequence.

[0065] State feature tracking capability

[0066] Through the previous monotonicity and sensitivity calculations, its state tracking capability is calculated as shown in formula (6).

[0067]

[0068] Finally, the effects of the median diameter of water droplets, wind speed, ambient temperature, and liquid water content on contact line icing are analyzed by using the state tracking capability.

[0069] Combined with the research on conductor icing at home and abroad, it is known that wind speed, liquid water content, median diameter of water droplets and atmospheric temperature are the main factors affecting icing. At the same time, combined with the actual working conditions of the contact line, the wind speed v is set to 9m / s and the liquid water content LWC is set to 0.6g / m 3, the median diameter of water droplets MVD = 0.035mm, the atmospheric temperature T = -12℃ as the reference value, the control variable method is used for research. When exploring a parameter, the other parameters keep the reference settings unchanged. The control variables also have a certain range to be more in line with the actual icing analysis, as shown in the following table. When studying the influence of a certain parameter, keep other parameters as the reference value unchanged, and continuously change the parameter to use the above numerical model to calculate the icing, and then study the influence law of the parameter, as shown in Table 1.

[0070] Table 1 (initial reference value data)

[0071]

[0072] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0073] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0074] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0075] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

[0076] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A method for analyzing the impact of ice coating on contact lines of electrified railways, characterized in that: The steps include: S1. Build time-varying grid division according to the changes of environmental parameters and ice boundary, and perform flow field analysis and grid analysis on the contact line surface; S2, updating the grid according to the parameters after the initial icing, and establishing a numerical model of contact line meteorological time-varying icing based on the updated grid; S3. Based on the established numerical model of contact line meteorological time-varying icing, the control variable method is used to analyze the factors affecting icing.

2. The method for analyzing the impact of ice coating on contact lines of electrified railways according to claim 1, characterized in that: The specific method of performing flow field analysis on the contact surface in S1 is: S11, obtaining the water droplet velocity and the collision coefficient between the water droplet and the contact line; S12, calculating the freezing coefficient according to the heat balance equation; S13, based on the water droplet velocity in S11, the collision coefficient between the water droplet and the contact line, and the freezing coefficient in S12, the ice mass per unit time is calculated to complete the ice calculation.

3. The method for analyzing the impact of ice coating on contact lines of electrified railways according to claim 2, characterized in that: The heat balance equation in S12 is expressed as: q i +q υ =q c +q e +q l +q s In the formula, q i is the latent heat released by freezing of supercooled droplets per unit length of the icing object; q υ The friction between the airflow and the ice-covered structure generates heat; q c is the heat loss on the surface of the icing object caused by convection heat transfer; q e The heat absorbed by the evaporation and sublimation of water on the ice surface; q l The heat absorbed by raising the temperature of the supercooled droplets attached to the surface of the icing object to the reference temperature; q s It is the heat loss caused by radiation from the surface of ice-covered conductor.

4. The method for analyzing the impact of icing on contact lines of electrified railways according to claim 2, characterized in that: The specific calculation method of ice mass in S13 is: Where α1 is the local collision rate of water droplets; α2 is the water droplet collection coefficient, which is generally taken as 1; α3 is the water droplet freezing coefficient; LWC is the atmospheric liquid water content; v p is the velocity of water droplet impacting the wire; L c is the surface length of the micro-element control body on the ice-covered conductor; L is the unit conductor length.

5. The method for analyzing the impact of ice coating on contact lines of electrified railways according to claim 1, characterized in that: The S2 specifically includes the following steps: S21, updating the grid according to the parameters after the initial icing, inputting the contour points of the icing surface after the contact line is iced, defining the geometric area boundary and the grid parameters, and completing the icing grid update in a loop; S22, after the grid is updated, flow field analysis is performed to calculate the collision coefficient and collision angle, and the state water content, wind speed, median diameter of water droplets, ice-covering time, and ambient temperature are set respectively, and the secondary ice-covering mass is calculated to generate an ice-covering contour curve; S23, combining the ice coverage contour curve with the updated grid to obtain a new grid for the next ice coverage and repeating steps S21-S22 to complete the construction of the contact line icing meteorological time-varying numerical model.

6. The method for analyzing the impact of ice coating on contact lines of electrified railways according to claim 1, characterized in that: The control variable method used in S3 to analyze ice cover influencing factors specifically includes monotonicity level analysis, sensitivity level analysis and state tracking capability analysis.

7. The method for analyzing the impact of ice coating on contact lines of electrified railways according to claim 5, characterized in that: The specific calculation method of the monotonicity level is: In the formula, β i is the monotonicity level, D i is the sum at time point i, t j ,t k are the characteristic values ​​of the ice state at the j-th and k-th time points respectively, and j,k∈[1,n], n is the total number of characteristic points, and sgn() is the sign function.

8. The method for analyzing the impact of ice coating on contact lines of electrified railways according to claim 5, characterized in that: The specific calculation method of the sensitivity level is: Where η i is the state tracking ability, median is the median, t j ,t k are the characteristic values ​​of the ice state at the jth and kth time points, respectively; d(j) and d(k) are the characteristic values ​​of the ice state of the characteristic sequence before and after the jth and kth time points.

9. The method for analyzing the impact of ice coating on contact lines of electrified railways according to claim 5, characterized in that: The specific calculation method of the state tracking capability is: In the formula, Z i is the state tracking capability, β i is the monotonicity level, η i is the sensitivity level.

Images