A method for determining the optimal arrangement of micro-guiding structures in the transformer winding region

Abstract

This invention discloses a micro-guided structure design method considering transformer winding discs. Based on dimensional analysis and fluid dynamics equations, the oil flow ratio relationship within the transformer winding is calculated. A two-dimensional CFD model of the winding region with different micro-guided structures is established in Ansys Icem software and imported into Ansys Fluent finite element simulation software to extract the flow ratio of each oil channel. Based on the parametric scanning results of each oil channel in the transformer winding simulated by the finite element software, the oil flow ratio function within the transformer winding is obtained. Based on the flow ratio function and the oil flow simulation results, the optimal placement of the micro-guided structure is iteratively calculated. Compared with existing technologies, this invention quantitatively calculates the optimal placement of the micro-guided structure through the oil flow ratio function, which helps to optimize the oil flow uniformity inside the transformer winding, more effectively suppresses reverse oil flow, thereby improving the transformer's cooling design and extending its service life.

Description

Technical Field

[0001] This invention belongs to the field of electrical equipment, and specifically relates to a micro-guiding structure design method considering transformer winding discs. Background Technology

[0002] The onboard traction transformer (hereinafter referred to as "onboard transformer") is the core equipment in the electrical system of the EMU. Its efficient cooling is a key link to realize the speed increase of the EMU and ensure that various equipment of the train, such as traction motors, lighting, and control, can operate efficiently and safely.

[0003] Compared to existing high-speed trains with speeds of 400 km / h and above, the power output of EMUs will increase by 50%, and losses will also increase accordingly. However, the assembly space for the onboard transformer has not increased accordingly, further complicating the cooling design and insulation layout. Current research and development has shown that increasing the oil pump output and flow rate has not achieved the expected cooling effect. In fact, it has been found that while increasing the inlet flow rate can reduce the average temperature rise, reverse flow occurs in some oil channels in the winding area, causing the temperature rise of the hottest spots to increase instead of decrease. Even if the design avoids abnormal phenomena under typical operating conditions such as rated load and stable operation, significant changes in oil viscosity and velocity under varied actual operating conditions can trigger reverse flow. The resulting localized overheating threatens the long-term reliability of the insulation, and the affected area is also a weak point in the overall insulation. Therefore, for the internal cooling design of onboard transformers under such stringent conditions of higher loss density, a micro-guiding structure is proposed to be added to the transformer winding wall to change the direction of the oil flow lines inside the winding, optimize the uniformity of the oil flow, and achieve the effect of avoiding reverse oil flow.

[0004] The patent with publication number CN118098763A, entitled "A Design Method for Local Micro-Guiding Structure in Transformer Winding Area", can determine the diameter and depth of the micro-guiding structure, but it is difficult to determine the optimal arrangement position of the micro-guiding structure. Summary of the Invention

[0005] Purpose of the invention: To address the problems in the background art, this invention proposes a method for determining the optimal placement of micro-guided structures in the transformer winding region. By establishing a transformer winding region model with added micro-guided structures, and based on dimensional analysis and fluid dynamics equations, the proportional function of oil flow rate within the transformer winding is obtained, thereby calculating the optimal placement of the micro-guided structures.

[0006] Technical solution: This invention discloses a method for determining the optimal arrangement position of micro-guiding structures in the transformer winding region, comprising:

[0007] Step 1: Based on dimensional analysis and fluid dynamics equations, calculate the proportional relationship of oil flow in the transformer windings;

[0008] Step 2: In Ansys Icem software, create a two-dimensional CFD model of the winding region with different micro-guide structures, import it into Ansys Fluent finite element simulation software, extract the flow rate ratio of each oil passage, and observe the oil flow streamlines.

[0009] Step 3: Based on the parametric scanning results of each oil passage in the transformer winding simulated by Ansys Fluent finite element simulation software, obtain the proportional function of oil flow rate in the transformer winding;

[0010] Step 4: Based on the flow rate ratio function and the oil flow simulation results, iteratively calculate the optimal placement of the micro-guide structure.

[0011] Furthermore, the oil flow ratio formula obtained in step 1 for the transformer winding is:

[0012]

[0013] Where: g i ' is in the form of a function, representing the function formed by the following variables, where ρ is the density of the oil flow. The average oil velocity at the inlet. It is the average velocity of the oil flow within the transformer windings, and n1 is the number of winding discs per span in the transformer winding region; W oin and W oout These are the widths of the inner and outer vertical oil passages, respectively; H o H is the height of the horizontal oil passage. d and W d These are the height and width of the winding disc, respectively; R in R is the length from the center of the micro-guide structure to the upper side of the second-stage oil guide gasket; w D is the radius of the micro-guided structure; w k represents the depth of the microguided structure. fi This represents the flow rate proportion of the i-th horizontal oil passage within the winding, where i = 1, 2, ..., n.

[0014] Furthermore, in step 2, the two-dimensional CFD model mode of the winding region is set to steady, the solver is set to pressure-based mode, the solution algorithm is set to implicit, and since the two-dimensional CFD model of the winding region is an axisymmetric model, the two-dimensional spatial properties are set to axisymmetric, the viscous model is set to Laminar, the pressure-velocity coupling method is SIMPLE, and the pressure is set to PRESTO.

[0015] Furthermore, the proportional function of oil flow rate in the transformer winding in step 3 is determined as follows:

[0016]

[0017] In the formula: k fi Let be the flow rate ratio of the i-th horizontal oil passage; n represents a positive integer, represents the number of horizontal oil passages, Re is the Reynolds number of the oil flow, and a ij b ijk c ijkm The virtual coefficients introduced are k for each fitted oil passage. fi Several d coefficients will be generated, d ijkm1 d ijkm2 d ijkm3 This means generating several d coefficients; α is the ratio of the radius of the micro-guide structure to the height of the winding disc; β is the ratio of the depth of the micro-guide structure to the height of the winding disc; γ is the ratio of the length from the center of the micro-guide structure to the upper side of the second-stage oil guide gasket to the height of the winding disc.

[0018] Further, in step 4, the average oil passage flow ratio and the maximum average oil passage flow ratio of different structured oil passages are iteratively calculated according to the flow ratio function. γ is extracted from the flow function of the maximum average oil passage flow ratio to determine the optimal placement of the micro-guide structure.

[0019]

[0020] R in =γ 1 H d

[0021] In the formula: The average flow rate ratio of oil passages with different structures; k fmax The maximum value of the average flow rate ratio for oil passages with different structures; γ 1 To obtain the maximum value of the average oil passage flow rate ratio k fmax In the flow function at time γ, R in H is the length from the center of the micro-guide structure to the upper side of the second-stage oil guide gasket. d This refers to the height and width of the winding disc.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. This invention can model the addition of different micro-guide structures to the transformer winding region. It can not only reflect the flow characteristics of oil flow inside the transformer winding and the suppression effect of micro-guide structures on reverse oil flow, but also propose an oil flow rate ratio function, which can quantitatively calculate the flow rate ratio of each oil channel inside the transformer winding with added micro-guide structures.

[0024] 2. This invention can find the optimal arrangement point of the micro-guide structure under transformer structures of different sizes, which helps to optimize the oil flow uniformity inside the transformer winding, more effectively suppress the reverse oil flow phenomenon, thereby improving the cooling design of the transformer, increasing the service life of the transformer, and providing a theoretical basis for the design of on-board transformers for next-generation high-speed trains with speeds of 400 km / h and above. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the method.

[0026] Figure 2 A schematic diagram of the transformer winding region with added micro-guided structures;

[0027] Figure 3 Create a two-dimensional CFD model of a transformer winding with micro-guided structure in Ansys Icem;

[0028] Figure 4 The simulation graph of oil flow rate in the two-dimensional CFD model of Ansys Fluent;

[0029] Figure 5 A diagram showing the proportion of oil flow rate within transformer windings under different gamma values;

[0030] Figure 6 The experimental results show the addition of micro-guided structures at the optimal placement location. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0032] This invention discloses a method for determining the optimal arrangement position of micro-guide structures in the transformer winding region. It involves calculating the arrangement position of the micro-guide structures to suppress reverse oil flow inside the transformer winding. Figure 1 As shown, the method includes:

[0033] S1: Based on dimensional analysis and fluid dynamics equations, the proportional relationship of oil flow in the transformer winding is calculated.

[0034] In step S1, based on dimensional analysis and fluid dynamics equations, the proportional relationship of oil flow within the transformer windings is calculated, specifically including:

[0035] First, establish a relationship between the average inlet oil velocity and the following variables:

[0036]

[0037] In the formula: n1 is the number of winding discs in each gear; W represents the average oil velocity at the inlet. oin and W oout These are the widths of the inner and outer vertical oil passages, respectively; H o H is the height of the horizontal oil passage. d and W d These are the height and width of the winding disc, respectively; R in R is the length from the center of the micro-guide structure to the upper side of the second-stage oil guide gasket; w D is the radius of the micro-guided structure; w The depth of the microguided structure.

[0038] Then ρ and W oout Using the reference parameter, the dimensional expression is transformed into a dimensionless form by the theorem as follows:

[0039]

[0040] Finally, replacing the ratio of average velocities in the oil passages with the product of the horizontal oil passage height and the inlet vertical oil passage width, we obtain the flow rate ratio formula within the oil passages:

[0041]

[0042] In the formula: k fi This represents the flow rate proportion occupied by the i-th horizontal oil passage within the winding, where i = 1, 2, ..., n. A schematic diagram of each parameter can be seen as follows... Figure 2 As shown, in this embodiment, the flow rate ratio of the seven horizontal oil passages is studied, that is, i = 1, 2, ..., 7 is selected.

[0043] S2: In Ansys Icem software, a two-dimensional CFD model of the winding region with different micro-guide structures is created and imported into Ansys Fluent finite element simulation software. The flow rate ratio of each oil passage is extracted, and the oil flow streamline and hot spot temperature are observed.

[0044] In Ansys Icem software, a two-dimensional CFD model of the winding region with different micro-guiding structures was created, such as... Figure 3 As shown; then import it into Ansys Fluent finite element simulation software, extract the flow rate ratio of each oil passage, observe the oil flow streamlines, and the simulation diagram of the oil flow rate in the two-dimensional CFD model is as follows. Figure 4 As shown; the two-dimensional CFD winding model mode is set to steady, the solver is set to pressure-based mode, the solution algorithm is set to implicit, since the model is an axisymmetric model, the two-dimensional spatial properties are set to axisymmetric, the viscous model is set to laminar, the pressure-velocity coupling method is SIMPLE, and the pressure is set to PRESTO.

[0045] S3: Based on the parameterized scanning results of each oil passage in the transformer winding simulated by finite element software, the proportional function of oil flow rate in the transformer winding is obtained.

[0046] A total of 560 simulations were obtained by scanning different dimensionless parameters for windings with different micro-guided structures. Geometric parameters α, β, and positional parameter γ could generate 81 models with different structures, all of which required modification and re-meshing in CFD. The oil flow rate ratio within the transformer winding under different γ values ​​is shown in the figure. Figure 5 As shown; substituting the simulation results into the flow ratio formula for iteration, the flow ratio function of the oil flow in the transformer winding is obtained as follows:

[0047]

[0048] In the formula: k fi The flow rate ratio of the i-th horizontal oil passage; a ij b ijk c ijkm The virtual coefficients introduced are k for each fitted oil passage. fi Several d coefficients will be generated; α is the ratio of the radius of the micro-guide structure to the height of the winding disc; β is the ratio of the depth of the micro-guide structure to the height of the winding disc; γ is the ratio of the length from the center of the micro-guide structure to the upper side of the second-stage oil guide gasket to the height of the winding disc.

[0049] In this embodiment, the flow rate ratio of seven horizontal oil passages is studied, that is, i = 1, 2, ..., 7 is selected, and when generating a thousand d coefficients, d ijkm1 d ijkm2 d ijkm3 This results in 64 generated d coefficients.

[0050] S4: Based on the flow rate ratio function and the oil flow simulation results, the optimal placement of the micro-guide structure is calculated iteratively.

[0051] Based on the flow rate ratio function and the oil flow simulation results, the optimal placement of the micro-guide structure was iteratively calculated, as follows:

[0052] First, the average oil passage ratio and the maximum average oil passage flow ratio for different oil passage structures are calculated iteratively based on the flow ratio function. The calculation formula is as follows:

[0053]

[0054] In the formula: The average flow rate ratio of oil passages with different structures; k fmaxThe maximum average oil passage flow rate ratio is calculated for different oil passage structures. Then, γ is extracted from the function of the maximum average oil passage flow rate ratio to obtain the length from the center of the micro-guide structure to the upper side of the second-stage oil guide gasket, which is the optimal placement position of the micro-guide structure. The calculation formula is as follows:

[0055] R in =γ 1 H d

[0056] In the formula: γ 1 To obtain the maximum value of the average oil passage flow rate ratio k fmax γ in the flow function at that time.

[0057] Using R in To determine the optimal placement of the final micro-guide structure, see [link / reference]. Figure 6 In this embodiment, the optimal position determined by the length from the final micro-guide structure center to the upper side of the second-stage oil guide gasket was used for experimental setup. Figure 6 The experimental results of adding microguide structures in the optimal placement position are shown in the figure. Figure 6 It can be seen that the micro-guide structure at this location determined by the present invention has a very good effect on suppressing reverse oil flow.

[0058] The above description is merely an illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific structure described, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, and such modifications or additions should be protected by the present invention.

Claims

1. A method for determining the optimal arrangement position of micro-guiding structures in the transformer winding region, characterized in that, include: Step 1: Based on dimensional analysis and fluid dynamics equations, calculate the proportional relationship of oil flow in the transformer windings; Step 2: In Ansys Icem software, create a two-dimensional CFD model of the winding region with different micro-guide structures, import it into Ansys Fluent finite element simulation software, extract the flow rate ratio of each oil passage, and observe the oil flow streamlines. Step 3: Based on the parametric scanning results of each oil passage in the transformer winding simulated by Ansys Fluent finite element simulation software, obtain the proportional function of oil flow rate in the transformer winding; The proportional function formula for oil flow rate within the transformer winding is determined as follows: ； In the formula: k fi Let be the flow rate ratio of the i-th horizontal oil passage; n represents a positive integer, and represents the number of horizontal oil passages. It is the Reynolds number of the oil flow, a ij b ijk c ijkm The virtual coefficients introduced are k for each fitted oil passage. fi Several d coefficients will be generated. , , This means generating several d coefficients; α is the ratio of the radius of the micro-guide structure to the height of the winding disc; β is the ratio of the depth of the micro-guide structure to the height of the winding disc; γ is the ratio of the length from the center of the micro-guide structure to the upper side of the second-stage oil guide gasket to the height of the winding disc. Step 4: Based on the flow rate ratio function and the oil flow simulation results, iteratively calculate the optimal placement of the micro-guide structure; The average flow rate ratio and the maximum average flow rate ratio of different oil passage structures are calculated iteratively based on the flow rate ratio function. γ is extracted from the flow rate function formula for the maximum average flow rate ratio, and the optimal placement of the micro-guide structure is determined as follows: ； ； ； In the formula: The average oil passage flow rate ratio for oil passages with different structures; This represents the maximum average flow rate ratio of oil passages with different structures. To obtain the maximum value of the average oil passage flow rate ratio In the flow function at time γ, R in H is the length from the center of the micro-guide structure to the upper side of the second-stage oil guide gasket. d This represents the height of the winding disc.

2. The method for determining the optimal arrangement position of the micro-guiding structure in the transformer winding region according to claim 1, characterized in that, The formula for the oil flow ratio in the transformer windings obtained in step 1 is: ； In the formula: It is in the form of a function, representing the function formed by the following variables. It is the density of the oil flow. The average oil velocity at the inlet. It is the average velocity of the oil flow within the transformer windings, and n1 is the number of winding discs per span in the transformer winding region; W oin and W oout These are the widths of the inner and outer vertical oil passages, respectively; H o The height of the horizontal oil passage; W d R is the width of the winding disc; in R is the length from the center of the micro-guide structure to the upper side of the second-stage oil guide gasket; w D is the radius of the micro-guided structure; w The depth of the microguided structure.

3. The method for determining the optimal arrangement position of the micro-guiding structure in the transformer winding region according to claim 1, characterized in that, In step 2, the two-dimensional CFD model mode of the winding region is set to steady, the solver is set to pressure-based mode, the solution algorithm is set to implicit, and since the two-dimensional CFD model of the winding region is an axisymmetric model, the two-dimensional spatial properties are set to axisymmetric, the viscous model is set to Laminar, the pressure-velocity coupling method is SIMPLE, and the pressure is set to PRESTO.

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