Method for determining optimal arrangement position of micro-guiding structure in transformer winding area

Abstract

The invention discloses a micro-guiding structure design method considering a transformer winding cake, and the method comprises the steps: carrying out the calculation based on a dimension analysis method and a fluid mechanics equation, and obtaining an oil flow proportional relation in a transformer winding; a winding area two-dimensional CFD model added with different micro guiding structures is established in Ansys Icem software, the winding area two-dimensional CFD model is imported into Ansys Fluent finite element simulation software, and the flow proportion of each oil duct is extracted; simulating a parameterized scanning result of each oil duct in the transformer winding according to finite element software to obtain a flow proportional functional expression of oil flow in the transformer winding; and iteratively calculating the optimal arrangement position of the micro-guiding structure according to the flow proportional functional expression and the oil flow simulation result graph. Compared with the prior art, the method has the advantages that the optimal arrangement position of the micro guide structure is quantitatively calculated through the oil flow proportional function expression, so that the oil flow uniformity in a transformer winding is favorably optimized, the reverse oil flow phenomenon is more effectively inhibited, the cooling design of the transformer is improved, and the service life of the transformer is prolonged.

Description

Technical Field

[0001] The invention belongs to the field of electrical equipment, and in particular relates to a micro-guide structure design method considering transformer windings. Background Art

[0002] The on-board traction transformer of an EMU (referred to as "on-board transformer") is the core equipment in the EMU electrical system. Its efficient cooling is the key link in achieving the speed increase of the EMU, ensuring that various equipment on the train, such as traction motors, lighting, and control, can operate efficiently and safely.

[0003] Compared with the existing highest speed EMUs, the power of EMUs with a speed of 400 kilometers per hour or above will increase by 50%, and the loss will also increase synchronously, but the assembly space of the on-board transformer has not been expanded accordingly, which further increases the difficulty of cooling design and insulation layout. In the current research and development, the expected cooling effect has not been achieved by increasing the output of the oil pump and adjusting the flow rate. It is even found that although increasing the inlet flow rate can reduce the average temperature rise, some oil channels in the winding area have reverse flow, resulting in the temperature rise of the hottest point to increase instead of decrease. Even if the design can avoid abnormal phenomena under several typical working conditions such as rated load and stable operation, the large changes in oil viscosity and speed will trigger reverse flow in the variable and diverse actual working conditions. The resulting local overheating threatens the long-term reliability of the insulation, and the area where it is located is also the weak insulation point of the whole machine. Therefore, for the internal cooling design of the on-board transformer under the harsh conditions of higher loss density, it is proposed to add a micro-guide structure to the transformer winding wall to change the direction of the oil flow streamline 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, "A method for designing a local micro-guide structure in a transformer winding area", can determine the diameter and depth of the micro-guide structure, but it is difficult to determine the optimal arrangement position of the micro-guide structure. Summary of the invention

[0005] Purpose of the invention: In response to the problems in the background technology, the present invention proposes a method for determining the optimal layout position of the micro-guide structure in the transformer winding area. By establishing a transformer winding area model with an added micro-guide structure, and based on dimensional analysis and fluid mechanics equations, the proportional function of the oil flow in the transformer winding is obtained, and then the optimal layout position of the micro-guide structure is calculated.

[0006] Technical solution: The present invention discloses a method for determining the optimal arrangement position of a micro-guide structure in a transformer winding area, comprising:

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

[0008] Step 2: Create a two-dimensional CFD model of the winding area with different micro-guide structures in Ansys Icem software, import it into Ansys Fluent finite element simulation software, extract the flow ratio of each oil channel, and observe the oil flow streamline;

[0009] Step 3: Using Ansys Fluent finite element simulation software to simulate the parametric scanning results of each oil channel in the transformer winding, the proportional function of the oil flow in the transformer winding is obtained;

[0010] Step 4: According to the flow ratio function and the oil flow simulation result diagram, iteratively calculate the optimal layout position of the micro-guide structure.

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

[0012]

[0013] Where: g i ' is a function, representing the function of the following variables, ρ is the density of the oil flow, is the average oil velocity at the inlet, is the average velocity of the oil flow in the transformer winding, n 1 W is the number of windings per gear in the transformer winding area; oin and W oout H are the widths of the inner and outer vertical oil passages respectively; o is the height of the horizontal oil channel; H d and W d are the height and width of the winding cake respectively; R in R is the length from the center of the micro-guide structure to the upper side of the second-gear oil guide gasket; w is the radius of the micro-guiding structure; D w is the depth of the micro-guiding structure; k fi It is the flow ratio of the i-th horizontal oil channel in the winding, i=1,2,...,n.

[0014] Furthermore, in step 2, the two-dimensional CFD model mode of the winding area is set to steady, the solver is set to Pressure-Based mode, and the solving algorithm is set to Implicit. Since the two-dimensional CFD model of the winding area is an axisymmetric model, the two-dimensional space attribute is set to axisymmetric, the viscosity model is set to Laminar, the pressure-velocity coupling mode is SIMPLE, and the pressure is set to PRESTO.

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

[0016]

[0017] Where: k fi is the flow rate ratio of the i-th horizontal oil channel; n is a positive integer, indicating the number of horizontal oil channels, Re is the Reynolds number of the oil flow, a ij , b ijk 、c ijkm is the virtual coefficient introduced, and k for each oil channel fitted fi A number of d coefficients will be generated, d ijkm1 ,d ijkm2 ,d ijkm3 That is to generate several d coefficients; α is the ratio of the radius of the micro-guide structure to the height of the winding cake; β is the ratio of the depth of the micro-guide structure to the height of the winding cake; 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 cake.

[0018] Furthermore, in step 4, the average oil channel flow ratio and the maximum value of the average oil channel flow ratio of the oil channels with different structures are iteratively calculated according to the flow ratio function, and γ in the flow function of the maximum value of the average oil channel flow ratio is extracted to determine the optimal arrangement position of the micro-guide structure as follows:

[0019]

[0020] R in =γ 1 H d

[0021] Where: is the average oil flow ratio of oil channels with different structures; k fmax is the maximum value of the average oil flow ratio of different oil channels; γ 1 To obtain the maximum value of the average oil channel flow ratio k fmax The γ, R in the flow function in H is the length from the center of the micro-guide structure to the upper side of the second-gear oil guide gasket; d is the height and width of the winding cake.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1: The present invention can realize the modeling of adding different micro-guide structures to the transformer winding area, which can not only reflect the flow characteristics of the oil flow inside the transformer winding and the inhibitory effect of the micro-guide structure on the reverse oil flow, but also proposes an oil flow rate ratio function, which can quantitatively calculate the flow ratio of each oil channel inside the transformer winding with the micro-guide structure added.

[0024] 2: The present invention can find the optimal arrangement point of the micro-guide structure under transformer structures of different sizes, which helps to optimize the uniformity of oil flow inside the transformer winding and more effectively suppress the reverse oil flow phenomenon, thereby improving the cooling design of the transformer and increasing the service life of the transformer, providing a theoretical basis for the design of on-board transformers for the next generation of EMUs with a speed of 400 kilometers per hour and above. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram of the method flow chart;

[0026] Figure 2 Schematic diagram of transformer winding area with added micro-guide structure;

[0027] Figure 3 Establish a 2D CFD model of transformer winding with micro-guide structure in Ansys Icem;

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

[0029] Figure 5 It is the oil flow ratio diagram in transformer winding under different γ;

[0030] Figure 6 A graph showing the experimental results of adding micro-guide structures at the optimal arrangement position. DETAILED DESCRIPTION

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

[0032] The present invention discloses a method for determining the optimal arrangement position of a micro-guide structure in a transformer winding region, which is aimed at suppressing reverse oil flow inside the transformer winding and determining the calculation of the arrangement position of the micro-guide structure. Figure 1 As shown, the method includes:

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

[0034] In step S1, based on the dimensional analysis method and the fluid mechanics equation, the proportional relationship of the oil flow in the transformer winding is calculated, which specifically includes:

[0035] First, the average oil velocity at the inlet is related to the following variables:

[0036]

[0037] Where: n 1 is the number of winding cakes in each gear; is the average oil velocity at the inlet; W oin and W oout H are the widths of the inner and outer vertical oil passages respectively; o is the height of the horizontal oil channel; H d and W d are the height and width of the winding cake respectively; R in R is the length from the center of the micro-guide structure to the upper side of the second-gear oil guide gasket; w is the radius of the micro-guiding structure; D w is the depth of the micro-guide structure.

[0038] Then ρ and W oout Set as the control parameter, and convert the dimensional expression into dimensionless form according to the theorem as follows:

[0039]

[0040] Finally, the ratio of the average oil channel velocity is replaced by the product of the oil channel velocity, the horizontal oil channel height and the inlet vertical oil channel width, and the flow rate ratio in the oil channel is obtained:

[0041]

[0042] Where: k fi It is the flow rate ratio of the i-th horizontal oil channel in the winding, i = 1, 2, ..., n. The schematic diagram of each parameter can be shown as Figure 2 As shown, in this embodiment, the flow ratio of 7 horizontal oil channels is studied, that is, i=1,2,...,7 is selected.

[0043] S2: A two-dimensional CFD model of the winding area with different micro-guide structures added was established in Ansys Icem software, and then imported into Ansys Fluent finite element simulation software to extract the flow ratio of each oil channel and observe the oil flow streamlines and hot spot temperatures.

[0044] A two-dimensional CFD model of the winding area with different micro-guide structures is established in Ansys Icem software, such as Figure 3 As shown; then imported into Ansys Fluent finite element simulation software, the flow ratio of each oil channel was extracted, the oil flow streamline was observed, and the two-dimensional CFD model oil flow rate simulation diagram was shown 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, and since the model is an axisymmetric model, the two-dimensional space property is set to axisymmetric, the viscosity model is set to Laminar, the pressure-velocity coupling mode is SIMPLE, and the pressure is set to PRESTO.

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

[0046] The different dimensionless parameters of the windings with different micro-guide structures were scanned, and a total of 560 simulations were obtained; the geometric parameters α, β and position parameters γ can generate a total of 81 models with different structures, all of which need to be modified and meshed again in CFD; the oil flow ratio diagram in the transformer winding under different γ is shown in Figure 5 As shown; Substituting the simulation results into the flow ratio relationship and iterating, the oil flow ratio function formula in the transformer winding is obtained as follows:

[0047]

[0048] Where: k fi is the flow rate ratio of the i-th horizontal oil channel; a ij , b ijk 、c ijkm is the virtual coefficient introduced, and k for each oil channel fitted 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 cake; β is the ratio of the depth of the micro-guide structure to the height of the winding cake; 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 cake.

[0049] In this embodiment, the flow ratio of 7 horizontal oil channels is studied, that is, i=1, 2, ..., 7 is selected, and when generating a plurality of d coefficients, d ijkm1 ,d ijkm2 ,d ijkm3 That is the 64 d coefficients generated.

[0050] S4: According to the flow ratio function and the oil flow simulation result diagram, the optimal layout position of the micro-guide structure is iteratively calculated.

[0051] According to the flow rate proportional function and the oil flow simulation result diagram, the optimal layout position of the micro-guide structure is iteratively calculated as follows:

[0052] First, the average oil channel ratio and the maximum value of the average oil channel flow ratio of different structural oil channels are iteratively calculated according to the flow ratio function. The calculation formula is:

[0053]

[0054] Where: is the average oil flow ratio of oil channels with different structures; k fmaxis the maximum value of the average oil channel flow ratio of different structures; then extract γ in the function of the maximum value of the average oil channel flow ratio, and obtain the length from the center of the micro-guide structure to the upper side of the second-gear oil guide gasket, that is, the optimal layout position of the micro-guide structure, and the calculation formula is as follows:

[0055] R in =γ 1 H d

[0056] Where: γ 1 To obtain the maximum value of the average oil channel flow ratio k fmax γ in the flow function when .

[0057] Using R in Determine the optimal arrangement position of the final micro-guide structure, see 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 gear oil guide gasket is used for experimental arrangement. Figure 6 The experimental results of adding micro-guide structures at the optimal arrangement position are shown in Figure 2. Figure 6 It can be seen that the micro-guide structure at this position determined by the present invention has a good effect on suppressing reverse oil flow.

[0058] The above content is merely an illustration of the structure of the present invention. Various modifications or additions made by technicians in the technical field to the specific structure described shall be protected by the present invention as long as they do not deviate from the structure of the invention or exceed the scope defined by the claims.

Claims

1. A method for determining the optimal arrangement position of a micro-guide structure in a transformer winding area, characterized in that: include: Step 1: Based on dimensional analysis and fluid mechanics equations, calculate the proportional relationship of oil flow in the transformer winding; Step 2: Create a two-dimensional CFD model of the winding area with different micro-guide structures in Ansys Icem software, import it into Ansys Fluent finite element simulation software, extract the flow ratio of each oil channel, and observe the oil flow streamline; Step 3: Using Ansys Fluent finite element simulation software to simulate the parametric scanning results of each oil channel in the transformer winding, the proportional function of the oil flow in the transformer winding is obtained; Step 4: According to the flow ratio function and the oil flow simulation result diagram, iteratively calculate the optimal layout position of the micro-guide structure.

2. A method for determining the optimal arrangement position of the micro-guide structure in the transformer winding area according to claim 1, characterized in that: The oil flow ratio relationship in the transformer winding obtained in step 1 is: Where: g i ' is a function, representing the function of the following variables, ρ is the density of the oil flow, is the average oil velocity at the inlet, is the average speed of oil flow in transformer winding, n1 is the number of winding cakes in each gear of transformer winding area; W oin and W oout H are the widths of the inner and outer vertical oil passages respectively; o is the height of the horizontal oil channel; H d and W d are the height and width of the winding cake respectively; R in R is the length from the center of the micro-guide structure to the upper side of the second-gear oil guide gasket; w is the radius of the micro-guide structure; D w is the depth of the micro-guiding structure; k fi It is the flow ratio of the i-th horizontal oil channel in the winding, i=1,2,...,n.

3. The method for determining the optimal arrangement position of the micro-guide structure in the transformer winding area according to claim 1, characterized in that: In step 2, the two-dimensional CFD model mode of the winding area is set to steady, the solver is set to Pressure-Based mode, and the solving algorithm is set to Implicit. Since the two-dimensional CFD model of the winding area is an axisymmetric model, the two-dimensional space attribute is set to axisymmetric, the viscosity model is set to Laminar, the pressure-velocity coupling mode is SIMPLE, and the pressure is set to PRESTO.

4. The method for determining the optimal arrangement position of the micro-guide structure in the transformer winding area according to claim 1, characterized in that: In step 3, the oil flow rate ratio function in the transformer winding is determined as: Where: k fi is the flow rate ratio of the i-th horizontal oil channel; n is a positive integer, indicating the number of horizontal oil channels, Re is the Reynolds number of the oil flow, a ij , b ijk 、c ijkm is the virtual coefficient introduced, and k of each oil channel is fitted fi A number of d coefficients will be generated, d ijkm1 d ijkm2 d ijkm3 That is to generate several d coefficients; α is the ratio of the radius of the micro-guide structure to the height of the winding cake; β is the ratio of the depth of the micro-guide structure to the height of the winding cake; 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 cake.

5. The method for determining the optimal arrangement position of the micro-guide structure in the transformer winding area according to claim 4, characterized in that: In step 4, the average oil channel flow ratio and the maximum value of the average oil channel flow ratio of the oil channels with different structures are iteratively calculated according to the flow ratio function, and γ in the flow function of the maximum value of the average oil channel flow ratio is extracted to determine the optimal arrangement position of the micro-guide structure: R in =c 1 H d Where: is the average oil flow ratio of oil channels with different structures; k fmax is the maximum value of the average oil flow ratio of different oil channels; γ 1 To obtain the maximum value of the average oil channel flow ratio k fmax γ, R in the flow function in H is the length from the center of the micro-guide structure to the upper side of the second-gear oil guide gasket; d is the height and width of the winding cake.

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