Method and system for analyzing charge quantity of water drops in direct-current electric field

Abstract

The invention discloses a water drop charge quantity analysis method and system in a direct-current electric field. The method comprises the steps that basic parameters of water drops are collected; calculating saturation charge quantity of water drops; constructing a field-induced charge model of water drops in the air in the electric field, and calculating field-induced charges of the water drops; comparing whether the water drop field-induced charge is saturated or not; constructing a water drop diffusion charge model, and calculating water drop diffusion charge; and calculating the total charge of the water drops. The electric field force borne by a single water drop can be obtained by calculating the water drop charge capacity under the direct-current electric field, the motion trail of the water drop is analyzed, the icing shape and the growth rule are predicted, and scientific basis and technical support are further provided for power transmission line anti-icing design, icing state prediction and line operation maintenance.

Description

Technical Field

[0001] The present invention relates to the technical field of water drop charge analysis, and in particular to a method and system for analyzing water drop charge under a direct current electric field. Background Art

[0002] During the UHV DC transmission process, transmission lines often need to cross a variety of regions, including some areas with harsh climatic conditions. Among them, the icing problem in winter is a serious challenge. When the live transmission wires are covered with ice, it not only increases the weight of the line, but may also cause line short circuits, tripping and other faults, seriously affecting the safe and stable operation of overhead lines.

[0003] In the natural environment, cooling water droplets move with the air flow toward the charged wire, and freeze to form ice after colliding with the wire. When ice forms on the wire, the volume fraction of the water droplet phase is very low, and the gas-water droplet two-phase flow can be considered as a rarefied flow. By accurately calculating the total charge of a single water droplet, analyzing the electric field force on the water droplet, and further studying the motion state trajectory of the water droplet, the shape and growth law of the ice can be predicted. However, existing analysis methods rarely consider ice on charged wires, and there is no relevant method description for calculating the charge of water droplets when the wire is charged.

[0004] Therefore, in order to solve the above technical problems, it is urgent to propose a new technical means to solve them. Summary of the invention

[0005] In view of the above-mentioned problems, the present invention is proposed.

[0006] Therefore, the technical problem solved by the present invention is: there is no relevant method description for calculating the charge of a water droplet when the conductor is charged.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for analyzing the charge of a water droplet under a DC electric field, comprising:

[0008] Collect basic parameters of water droplets;

[0009] Calculate the saturated charge of the water drop;

[0010] Construct a field-induced charging model for water droplets in the air in an electric field and calculate the field-induced charging of water droplets;

[0011] Compare whether the field-induced charging of the water droplets is saturated;

[0012] Construct a water droplet diffusion charge model and calculate the water droplet diffusion charge;

[0013] Calculate the total charge of the water droplets.

[0014] As a preferred solution of the method for analyzing the charge of a water droplet under a DC electric field described in the present invention, the basic parameters include: the radius of the water droplet R d 、Relative dielectric constant of water droplet ε r , the relative dielectric constant of the air where the water drop is located ε0, the original field strength at the location of the water drop E0, and the ion concentration in the air C i , ambient temperature T, effective diffusion coefficient of ions in air D i .

[0015] As a preferred embodiment of the method for analyzing the charge of a water droplet under a DC electric field of the present invention, the saturated charge includes the maximum electric field intensity E of the external electric field on the particle surface. max The electric field strength is equal to that generated by the charge of the particles themselves, indicating that the field charging of the water droplets has reached saturation.

[0016] As a preferred solution of the method for analyzing the charge of water droplets under a DC electric field of the present invention, the calculation of the saturated charge of water droplets specifically includes: the water droplets in the air are a low volume fraction air-water mixed flow; the saturated charge of the water droplets is calculated as:

[0017]

[0018] As a preferred solution of the method for analyzing the charge of a water droplet under a DC electric field of the present invention, the field-induced charging model includes the following equation: during the movement of a water droplet close to a charged wire, the relationship between the charge of the water droplet and time can be calculated:

[0019]

[0020] Where τ is the time constant associated with corona discharge, τ = 4ε0 / N0eμ i , N0 is the ion number density, μ i is the ion mobility.

[0021] As a preferred embodiment of the method for analyzing the charge of a water droplet under a DC electric field of the present invention, the comparison of whether the field-induced charge of the water droplet is saturated includes: if the charge Q(t) calculated by the water droplet is ≥Q max , then the field charge of the water drop is saturated, and the actual field charge of the water drop is Q1 = Q max ; If the calculated charge of the water droplet Q(t)<Q max , the field charge of the water droplet has not reached saturation, and the actual field charge of the water droplet is Q1 = Q(t).

[0022] As a preferred solution of the water droplet charge analysis method under a DC electric field described in the present invention, the water droplet diffuse charge includes: if the water droplet diameter in the air is less than 50 μm, the water droplet diameter is too small, and its diffuse charge phenomenon is ignored, and the diffuse charge Q2=0; if the water droplet diameter in the air is ≥50 μm, the charge obtained by the interaction between the water droplet and the ions in the air is considered, and the diffuse charge calculation formula is:

[0023] Q2=4πR d D i C i t

[0024] The total charge Q of a water droplet is the sum of the charge Q1 caused by the water droplet field and the charge Q2 caused by the water droplet diffusion:

[0025] Q=Q1+Q2.

[0026] A water droplet charge analysis system under a DC electric field using any method described in the present invention, characterized in that:

[0027] The collection unit collects the basic parameters of water droplets.

[0028] The calculation unit calculates the saturated charge of water droplets; constructs a field-induced charging model of water droplets in the air in an electric field, and calculates the field-induced charging of water droplets.

[0029] The analysis unit compares whether the field-induced charge of the water droplets is saturated; a water droplet diffusion charge model is constructed to calculate the water droplet diffusion charge.

[0030] Output unit, calculate the total charge of the water droplets.

[0031] A computer device comprises: a memory and a processor; the memory stores a computer program, wherein: the processor implements the steps of any one of the methods of the present invention when executing the computer program.

[0032] A computer-readable storage medium stores a computer program, wherein: when the computer program is executed by a processor, the steps of any one of the methods of the present invention are implemented.

[0033] Beneficial effects of the present invention: The method for analyzing the charge of water droplets under a DC electric field provided by the present invention can obtain the electric field force exerted on a single water droplet by calculating the charge of water droplets under a DC electric field, analyze the movement trajectory of water droplets, predict the shape and growth law of ice coating, and further provide a scientific basis and technical support for anti-icing design of transmission lines, prediction of ice coating status, and line operation and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0035] Figure 1 An overall flow chart of a method for analyzing the charge of a water droplet under a DC electric field provided in the first embodiment of the present invention;

[0036] Figure 2 A point dipole model diagram of a water drop in a method for analyzing the charge of a water drop under a direct current electric field provided by the first embodiment of the present invention;

[0037] Figure 3 A one-dimensional radial space charge density distribution diagram of a method for analyzing the charge of a water droplet under a DC electric field provided by the second embodiment of the present invention;

[0038] Figure 4 A two-dimensional radial space charge density distribution diagram in a method for analyzing the charge of a water droplet under a direct current electric field provided by the second embodiment of the present invention;

[0039] Figure 5 A diagram showing the calculation results of the water droplet field-induced charge quantity of a water droplet charge quantity analysis method under a DC electric field provided in the second embodiment of the present invention;

[0040] Figure 6 This is a diagram showing the calculation results of the total charge of a water droplet according to a method for analyzing the charge of a water droplet under a DC electric field provided in the second embodiment of the present invention. DETAILED DESCRIPTION

[0041] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0042] Example 1, reference Figure 1 , 2 , as an embodiment of the present invention, provides a method for analyzing the charge of a water droplet under a direct current electric field, comprising:

[0043] S1. Input basic parameters.

[0044] Furthermore, the basic parameters to be input include: water drop radius R d 、Relative dielectric constant of water droplet ε r, the relative dielectric constant of the air where the water drop is located ε0, the original field strength at the location of the water drop E0, and the ion concentration in the air C i , ambient temperature T, effective diffusion coefficient of ions in air D i .

[0045] S2. Calculate the saturated charge of the water droplet.

[0046] Furthermore, the sign that the field-induced charging of the water droplet has reached saturation is the maximum electric field intensity E on the particle surface. max The electric field strength is equal to that generated by the charge carried by the particle itself.

[0047] Furthermore, in the step S2., the water droplets in the air are a low volume fraction air-water mixed flow.

[0048] S21. For low volume fraction air-water mixed flow, the interaction between water droplets is ignored and each water droplet is considered to be a separate particle placed in an infinite air medium.

[0049] S23. Water droplets are uniform spherical particles and are calculated using the point dipole model, such as Figure 2 shown.

[0050] S24. The electric field intensity on the surface of a water droplet is analyzed using a point dipole model based on the Laplace equation. The electric field intensity at each point on the surface of a spherical particle is obtained as follows:

[0051]

[0052] Where E0 is the original external electric field strength at the location of the water drop, and θ is the angle between each point on the surface and the electric field line. Constant k = (ε r -ε0) / (ε r +2ε0),ε r is the relative dielectric constant of the water droplet, and ε0 is the relative dielectric constant of the air.

[0053] S25. Considering that the relative dielectric constant of water droplets is much greater than that of air, analysis (1) shows that the maximum field strength point is the upper end point of the spherical particle, and the maximum field strength is:

[0054]

[0055] In the formula, ε r =81,ε0=1, it can be obtained that the maximum electric field strength on the surface of the spherical particle placed in the air is close to 3 times the original external electric field strength. The water droplets change the original electric field distribution, the electric field is distorted on the surface of the water droplets, and reaches the maximum value at the upper end point.

[0056] S26. When a water droplet is saturatedly charged, the electric field generated by its own charge should be equal to the maximum electric field strength E on the surface of the water droplet. maxEqual, assuming that the charge of the water droplet is Q max , according to Gauss's theorem:

[0057]

[0058] S27. Combining (2) and (3), we can get the saturation charge of the water droplet as:

[0059]

[0060] The saturated charge of a water droplet is related to the radius of the water droplet, the original field strength at the location of the water droplet, and the relative dielectric constant of the water droplet and the air.

[0061] S3. Construct a field-induced charging model for water droplets in the air in an electric field and calculate the field-induced charging of the water droplets.

[0062] Furthermore, the water droplet goes through the following three stages when moving near the charged wire:

[0063] 1. When a water droplet is released from a position far away from the wire, the water droplet itself is not charged. This is the initial condition for calculating the charge of the water droplet close to the wire.

[0064] 2. As the water droplets move closer to the wire, the corona current generated by the DC discharge of the wire continuously charges the water droplets.

[0065] 3. When the water droplets reach the surface of the ice-covered wire, they collide with the wire and freeze. At this time, the charge of the water droplets reaches the maximum.

[0066] S31. Assuming that the charge of the water droplet at time t is Q(t), then according to the electric field generated by this part of the charge and the external electric field at the location of the water droplet, the total electric flux of the water droplet is:

[0067]

[0068] S32. Calculate the ion current reaching the water droplet as:

[0069]

[0070] Where N0 is the ion concentration, e is the basic charge, e = 1.602 × 10 -19 C, μ i is the ion mobility. On the other hand, the current can be written as the derivative of charge with respect to time:

[0071]

[0072] S33. Combine equations (2-6) and (2-7), integrate both sides of the equation, and substitute the initial conditions to obtain the relationship between the charge of the water droplet and time:

[0073]

[0074] Where τ is the time constant associated with corona discharge, τ = 4ε0 / N0eμ i , N0 is the ion number density, μ i is the ion mobility.

[0075] S4. Compare whether the field charge of the water droplets is saturated.

[0076] S41. If the calculated charge of the water droplet Q(t) ≥ Q max , then the field charge of the water drop is saturated, and the actual field charge of the water drop is Q1 = Q max .

[0077] S42. If the calculated charge of the water droplet Q(t) < Q max , the field charge of the water droplet has not reached saturation, and the actual field charge of the water droplet is Q1 = Q(t).

[0078] Furthermore, in the step S4., in the simulation and experimental study of ice coating on the conductors of the high-voltage direct current transmission line, the water droplets close to the conductors often do not reach the saturation charge.

[0079] S5. Construct a water droplet diffusion charge model and calculate the water droplet diffusion charge.

[0080] Furthermore, the diffuse charging of water droplets is the process by which water droplets in the air acquire electric charge by interacting with ions in the air. This charging mechanism mainly occurs in the absence of an external electric field and relies on the random collision and attachment between ions in the air and water droplets.

[0081] When constructing a calculation model for water droplet diffusion charging, the diameter of the water droplets needs to be considered.

[0082] S51. If the diameter of water droplets in the air is less than 50 μm, the diameter of the water droplets is too small, and the diffusion charging phenomenon can be ignored, and the diffusion charge Q2 = 0.

[0083] S52. If the diameter of water droplets in the air is ≥50μm, it is necessary to consider the charge obtained by the interaction between the water droplets and the ions in the air.

[0084] S53. The formula for calculating the diffusion charge is as follows:

[0085] Q2=4πR d D i C i t

[0086] In the formula, R d is the radius of the water droplet, D i C is the ion diffusion dilution i is the ion concentration, t is the time;

[0087] S6. Calculate the total charge of the water droplets.

[0088] Furthermore, the total charge Q of the water droplet is the sum of the field charge Q1 and the diffusion charge Q2 of the water droplet, that is,

[0089] Q=Q1+Q2

[0090] On the other hand, this embodiment also provides a water droplet charge analysis system under a DC electric field, which includes:

[0091] The collection unit collects the basic parameters of water droplets.

[0092] The calculation unit calculates the saturated charge of water droplets; constructs a field-induced charging model of water droplets in the air in an electric field, and calculates the field-induced charging of water droplets.

[0093] The analysis unit compares whether the field-induced charge of the water droplets is saturated; a water droplet diffusion charge model is constructed to calculate the water droplet diffusion charge.

[0094] Output unit, calculate the total charge of the water droplets.

[0095] If the above functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0096] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0097] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0098] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0099] Embodiment 2, as Figure 3-6 , which is an embodiment of the present invention, provides a method for analyzing the charge of a water droplet under a DC electric field. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0100] Enter the basic parameters required to calculate the charge of water droplets. The calculation is performed with water droplet diameters of 80 μm, 70 μm, and 60 μm, and the parameters are set as follows: wind speed is 3 m / s; electric field strength is E0 = 25 kV / cm; e is the basic charge, e = 1.602 × 10 - 19C; μi is the ion mobility, μi = 2.4 cm 2 / (V·s); relative dielectric constant of water droplet ε r =81; relative dielectric constant of air ε0=1; π=3.14; Comsol software is used to simulate the multi-physics field coupling model of the coaxial cylindrical corona cage. A DC high voltage of E0=25kV / cm is applied to the inner electrode, and the outer electrode is grounded. The space charge density N0 is obtained through simulation analysis. The space charge density distribution is obtained in the Comsol simulation as follows Figure 3 and Figure 4As shown. In the one-dimensional radial space charge density distribution diagram, the horizontal axis represents the radial distance from the wire, and the vertical axis represents the space charge density at different positions in space. In the two-dimensional radial space charge density distribution diagram, the horizontal and vertical axes are the spatial x-axis and y-axis coordinates, respectively. The changing colors in the diagram represent the density of the space charge along the x-axis and y-axis.

[0101] Calculate the water droplet field charge Q1 = Q(t), and substitute the basic parameters into the water droplet field charge calculation model:

[0102]

[0103] The calculated charge distribution of water droplets at different radial positions along the inner conductor is as follows: Figure 5 As shown. The horizontal axis in the figure is the distance of the water droplet along the radial direction of the inner conductor, and the vertical axis represents the charge of the water droplet under the action of the DC electric field. At the position of the inner conductor, the charge of a water droplet with a diameter of 80μm is about 1.01pC, the charge of a water droplet with a diameter of 70μm is about 0.78pC, and the charge of a water droplet with a diameter of 60μm is about 0.57pC.

[0104] At the inner conductor position, a water droplet with a diameter of 80 μm carries a charge of approximately 1.01 pC, a water droplet with a diameter of 70 μm carries a charge of approximately 0.78 pC, and a water droplet with a diameter of 60 μm carries a charge of approximately 0.57 pC.

[0105] In the simulation and experimental study of ice coating on HVDC transmission line conductors, the water droplets near the conductors have not reached the saturated charge, Q1<Q max .

[0106] Since the diameter of the water droplets in the calculation example is ≥50μm, the diffusion charge of the water droplets can be ignored, that is, Q2=0, so the total charge of the water droplets can be obtained as Q=Q1. Figure 6 As shown. The calculation example completes the calculation of the charge of water droplets with diameters of 80μm, 70μm and 60μm by inputting basic parameters, calculating the field-induced charge Q1, calculating and comparing the field-induced charge with the saturated charge to determine that the water droplet charge is not saturated, calculating the diffused charge Q2, and calculating the total charge of the water droplet Q=Q1+Q1. The calculation results can accurately measure the charge of the water droplet and match the actual results.

[0107] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for analyzing the charge of a water droplet under a direct current electric field, characterized in that: include: Collect basic parameters of water droplets; Calculate the saturated charge of the water drop; Construct a field-induced charging model for water droplets in the air in an electric field and calculate the field-induced charging of water droplets; Compare whether the field-induced charging of the water droplets is saturated; Construct a water droplet diffusion charge model and calculate the water droplet diffusion charge; Calculate the total charge of the water droplets.

2. The method for analyzing the charge of a water droplet under a DC electric field as claimed in claim 1, characterized in that: The basic parameters include: water drop radius R d 、Relative dielectric constant of water droplet ε r , the relative dielectric constant of the air where the water drop is located ε0, the original field strength at the location of the water drop E0, and the ion concentration in the air C i , ambient temperature T, effective diffusion coefficient of ions in air D i .

3. The method for analyzing the charge of a water droplet under a DC electric field as claimed in claim 2, characterized in that: The saturation charge includes the maximum electric field strength E of the external electric field on the particle surface. max The electric field strength is equal to that generated by the charge of the particles themselves, indicating that the field charging of the water droplets has reached saturation.

4. The method for analyzing the charge of a water droplet under a direct current electric field as claimed in claim 3, characterized in that: The calculation of the saturated charge of the water droplets specifically includes that the water droplets in the air are a low volume fraction air-water mixed flow; the saturated charge of the water droplets is calculated as:

5. The method for analyzing the charge of a water droplet under a direct current electric field as claimed in claim 4, characterized in that: The field-induced charging model includes the following equation: during the movement of a water droplet close to a charged wire, the relationship between the charge of the water droplet and time can be calculated: Where τ is the time constant associated with corona discharge, τ = 4ε0 / N0eμ i , N0 is the ion number density, μ i is the ion mobility.

6. The method for analyzing the charge of a water droplet under a direct current electric field as claimed in claim 5, characterized in that: The comparison of whether the field-induced charge of the water droplet is saturated includes: if the charge Q(t) calculated by the water droplet is ≥Q max , then the field charge of the water drop is saturated, and the actual field charge of the water drop is Q1 = Q max ; If the calculated charge of the water droplet Q(t)<Q max , the field charge of the water droplet has not reached saturation, and the actual field charge of the water droplet is Q1 = Q(t).

7. The method for analyzing the charge of a water droplet under a direct current electric field as claimed in claim 6, characterized in that: The water droplet diffusion charge includes: if the diameter of the water droplet in the air is less than 50 μm, the water droplet diameter is too small, and the diffusion charge phenomenon is ignored, and the diffusion charge Q2=0; if the diameter of the water droplet in the air is ≥50 μm, the charge obtained by the interaction between the water droplet and the ions in the air is considered, and the diffusion charge calculation formula is: Q2=4πR d D i C i t The total charge Q of a water droplet is the sum of the charge Q1 caused by the water droplet field and the charge Q2 caused by the water droplet diffusion: Q=Q1+Q2.

8. A water droplet charge analysis system under a DC electric field using the method as claimed in any one of claims 1 to 7, characterized in that: The collection unit collects the basic parameters of water droplets. The calculation unit calculates the saturated charge of water droplets; constructs a field-induced charging model of water droplets in the air in an electric field, and calculates the field-induced charging of water droplets. The analysis unit compares whether the field-induced charge of the water droplets is saturated; a water droplet diffusion charge model is constructed to calculate the water droplet diffusion charge. Output unit, calculate the total charge of the water droplets.

9. A computer device comprising: A memory and a processor; the memory stores a computer program, wherein the processor implements the steps of any method as claimed in claim 1 when executing the computer program.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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