Blade mold area estimation method, computer device, and readable storage medium

Abstract

The present invention belongs to the field of wind turbine blade design and manufacturing, and particularly relates to a blade mold area estimation method, a computer device, and a readable storage medium. The method comprises: during area calculation, reading geometric parameters of a wind turbine blade, and for standard airfoils of different relative thicknesses within a corresponding airfoil family, generating a corresponding arc length-relative thickness relationship table for the standard airfoils; for each section of the blade, by means of the corresponding arc length-relative thickness relationship table for the standard airfoils, interpolating to compute the arc lengths of the SS surface and the PS surface of the standard airfoil thereof; multiplying the arc lengths of the SS surface and the PS surface of the standard airfoil by a scaling coefficient k to obtain the actual arc lengths of the SS surface and the PS surface of each section, and integrating the arc lengths of the SS surface and the PS surface of each section to obtain a surface area of the blade, that is, solving the surface area of the mold. During an early-stage iterative design process of a wind turbine blade, the present invention can rapidly estimate the area of each segment of mold for the SS surface or the PS surface of the blade, which is more reliable than empirical estimation, thus avoiding the substantial work of repeatedly drawing 3D profiles.

Description

A method for estimating the area of ​​a blade mold, a computer device, and a readable storage medium. Technical Field

[0001] This invention belongs to the field of wind turbine blade design and manufacturing, specifically relating to a method for estimating the area of ​​a blade mold, a computer device, and a readable storage medium. Background Technology

[0002] With the introduction of dual-carbon goals, renewable energy sources such as wind power are developing rapidly. In the manufacturing process of wind turbine blades, the cost of the mold is a major part of the blade production cost, and the cost of the mold is positively correlated with the mold area. Therefore, obtaining information on the blade mold area is crucial in the design process of wind turbine blades.

[0003] The area of ​​the mold for a wind turbine blade is roughly equal to the surface area of ​​the wind turbine blade. Currently, in the early design process of wind turbine blades, industry professionals often estimate the approximate area of ​​a certain section of the mold based on experience. After the aerodynamic shape of the wind turbine blade is determined, detailed 3D drawings can be created using mechanical drawing software such as CATIA, SolidWorks, and UG, and the surface area of ​​the blade can be measured in the software.

[0004] Empirical estimations often have large deviations and are not accurate or reliable enough; while the method of measurement through 3D maps is more accurate, the drawing process is more cumbersome and it is difficult to apply it repeatedly in the early iterative design.

[0005] Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for estimating the area of ​​blade molds, along with a computer device and a readable storage medium. This method enables rapid estimation of the mold area of ​​each segment of the blade using aerodynamic shape data during the early iterative design phase of wind turbine blades, providing industry professionals with relatively accurate information and thus reflecting the approximate required cost.

[0007] The objective of this invention is achieved through the following technical solution. A method for estimating the area of ​​a wind turbine blade mold, according to this invention, includes the following steps:

[0008] Read the geometric parameters of the wind turbine blade, including the distance between each section and the blade root, chord length, relative thickness, and the code of the selected airfoil;

[0009] For standard airfoils with different relative thicknesses in the corresponding airfoil family, the corresponding standard airfoil arc length-relative thickness relationship table is obtained by doubling the number of scatter points.

[0010] For each section of the blade, the arc lengths of the SS and PS surfaces of the standard airfoil can be calculated by interpolation using the corresponding standard airfoil arc length-relative thickness relationship table;

[0011] The arc lengths of the SS and PS surfaces of the standard airfoil are multiplied by a scaling factor k to obtain the actual arc lengths of the SS and PS surfaces of each cross section. From this, a table showing the relationship between the arc lengths of the SS and PS surfaces of each blade cross section and the blade root distance is obtained.

[0012] By integrating the arc lengths of the SS and PS surfaces of each cross section, the surface area of ​​the blade is obtained, which in turn determines the surface area of ​​the mold.

[0013] Furthermore, the formula for calculating the arc length of a standard airfoil is as follows:

[0014] In the formula, L is the arc length of the airfoil segment on the SS or PS surface, (x i ,y i ) represents the coordinates of a point on the airfoil, and i represents the number of the point on the airfoil.

[0015] Furthermore, in the standard airfoil arc length calculation process, a certain number of scattered points are first used to describe the airfoil curve segment of the SS or PS surface, and its arc length is calculated. Then, the number of scattered points is continuously multiplied, and its arc length is calculated again. If the difference between the two arc lengths is less than the allowable error, the calculation is stopped, and the arc length of the SS or PS surface of the standard airfoil under the relative thickness is obtained; otherwise, the above process is repeated, thereby obtaining the arc length-relative thickness relationship table of the family of standard airfoils.

[0016] Furthermore, when doubling the number of scatter points, take:

[0017] If the specific formula for the airfoil is known, then x can be substituted into it. i+1 / 2 Find y i+1 / 2 Otherwise, y can be obtained using spline interpolation. i+1 / 2 .

[0018] Furthermore, the trapezoidal integral method is used to integrate the arc lengths of the SS and PS surfaces of each cross-section, and the distances x1, x2, x3, ..., x between each cross-section of the wind turbine blade and the blade root are calculated. n-1 ,x n The corresponding airfoil SS or PS surface arc lengths y1, y2, y3, ..., y n-1 ,y n Then the surface area of ​​the SS or PS surface of the blade is:

[0019] Furthermore, the Simpson method is used to integrate the arc lengths of the SS and PS surfaces of each cross-section to obtain the blade surface area. The arc lengths of the SS or PS surfaces of each cross-section of the wind turbine blade with equal spacing are y1, y2, y3, ..., y n-2 ,y n-1 ,y nIf the distance between adjacent sections is l, then the surface area of ​​the SS or PS surface of the blade can be expressed as:

[0020] Furthermore, in order to make the value of the distance between adjacent sections of the wind turbine blade accurate to 0.1m, we can take l = 0.1m, and calculate the arc length of the airfoil SS surface or PS surface of each section by interpolation based on the calculated arc length of the section, and then calculate the surface area of ​​the blade SS surface or PS surface.

[0021] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method.

[0022] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] This invention can quickly estimate the area of ​​each section of the mold on the SS or PS surface of the wind turbine blade using a small amount of aerodynamic shape data (the calculation time is on the order of 1 second) during the early iterative design process of the wind turbine blade, thereby reflecting the approximate required cost. This is more reliable than empirical estimation (the error is within about 4%) and avoids a lot of work in repeatedly drawing 3D shapes.

[0025] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0026] Figure 1 is a schematic diagram of the segments of a wind turbine blade;

[0027] Figure 2a is a schematic cross-sectional view of a wind turbine blade;

[0028] Figure 2b is a schematic diagram of the SS and PS surfaces of the wind turbine blade mold cross-section;

[0029] Figure 3 is a schematic diagram of the airfoil parameters of a wind turbine blade;

[0030] Figure 4 is a comparison of the NACA0018 standard airfoil and the NACA0048 standard airfoil;

[0031] Figure 5a is a schematic diagram of the scatter sequence of standard airfoils;

[0032] Figure 5b is a schematic diagram of the method for doubling the number of scatter points;

[0033] Figure 6 is a schematic diagram of a blunt trailing edge airfoil;

[0034] Figure 7 is a schematic diagram of the principle of Simpson's first method.

[0035] [Attached image labels]

[0036] 1-SS surface, 2-PS surface, 3-NACA0048 standard airfoil, 4-NACA0018 standard airfoil, 5-upper trailing edge point, 6-lower trailing edge point. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] The area of ​​a wind turbine blade mold is approximately equal to the surface area of ​​the wind turbine blade. A typical wind turbine blade has the shape shown in Figure 1 along its length. Wind turbine blade molds are mostly manufactured in segments. Multiple segments of the wind turbine blade mold are spliced ​​together to form a complete mold.

[0039] Figure 2a shows a schematic diagram of one cross-section of a wind turbine blade. The wind turbine blade is divided into an SS surface (suction surface) and a PS surface (pressure surface), as shown in Figure 2b. Correspondingly, the wind turbine blade mold is also divided into an SS surface and a PS surface. The surface areas of the SS surface and PS surface of the wind turbine blade mold are estimated based on the areas of the SS surface and PS surface of the wind turbine blade during design. The estimation method for the surface area of ​​the SS surface is the same as that for the surface area of ​​the PS surface.

[0040] As shown in Figure 3, the line connecting the leading and trailing edges of the airfoil is called the chord, and its length is called the chord length, usually denoted by b. A standard airfoil refers to an airfoil with a chord length of 1 unit, which is taken as 1m in this invention. The distance between the perpendicular line to the chord and the intersection points of the upper and lower surfaces of the airfoil is called the thickness, and its maximum value is called the maximum thickness. The thickness usually mentioned is the maximum thickness, usually denoted by t. The ratio of the maximum thickness to the chord length... That is, the relative thickness.

[0041] Table 1

[0042] When estimating the surface area of ​​the SS or PS surface of a wind turbine blade, the geometric parameters of the blade are first read. A wind turbine blade has multiple cross-sections distributed along its length. These geometric parameters include the distance between each cross-section and the blade root (blade radius), chord length, relative thickness, and the airfoil code. For blades in the 100-meter range, approximately 60 cross-sections are typically selected, with adjacent cross-sections within 2 meters. Table 1 only shows a portion of the geometric parameters of the wind turbine blade. Generally, the twist angle variation between adjacent cross-sections is small (less than 2°), having a minimal impact on the blade's surface area; therefore, it is not considered in this invention, and the distribution of twist angles does not need to be read.

[0043] Each blade's SS or PS surface comprises at least one family of airfoils. This embodiment uses one family of airfoils as an example. When the relative thickness of the same family of airfoils differs, the airfoil's perimeter varies. Figure 4 shows a comparison between the NACA0018 and NACA0048 standard airfoils, with relative thicknesses of 18% and 48% respectively, resulting in significantly different perimeters. Therefore, for a family of standard airfoils with different relative thicknesses, the corresponding "Standard Airfoil Perimeter (Sum of SS and PS Surface Arc Lengths) - Relative Thickness Relationship Table" must first be obtained. Table 2 lists the SS and PS surface arc lengths for some relative thicknesses. Subsequently, spline interpolation can be performed based on this table to obtain the standard airfoil perimeter (sum of SS and PS surface arc lengths) for other different relative thicknesses.

[0044] A standard airfoil consists of an approximately uniformly distributed sequence of scattered points, as shown in Figure 5a, which represents a standard airfoil with a certain relative thickness. For the SS or PS surface, when the number of scattered points is sufficient, it can be approximated by the following formula:

[0045] In the formula, L is the arc length of the airfoil segment on the SS or PS surface, (x i ,y iLet π be the coordinates of a point on the airfoil, and i be the number of that point. The formula approximates the length of the arc by using the length of the straight line between two points, which requires a small distance between adjacent points. In calculating the arc length, this embodiment first uses approximately 30 scattered points to describe the airfoil curve segment of the SS or PS surface, as shown in Figure 5a, and calculates its arc length. It is worth noting that when using a certain number of scattered points to describe the airfoil, the first and last points of the scattered point sequence should be the same point to ensure that no curve segment is missed during the calculation. Then, the number of scattered points is continuously increased, as shown in Figure 5b, and the arc length is calculated again. If the difference between the two arc lengths is less than the allowable error (1 cm in this embodiment), the calculation is stopped, and the standard airfoil (SS or PS surface) arc length at that relative thickness is obtained; otherwise, the above process is repeated. Using the above calculation method (the calculation method for the arc length of the SS surface and the PS surface is the same), the arc length of a certain family of standard airfoils with different relative thicknesses is calculated, thereby obtaining the arc length-relative thickness relationship table of a certain family of standard airfoils (SS surface and PS surface), as shown in Table 2.

[0046] Table 2

[0047] The method for doubling the number of scatter points is shown in Figure 5b. Take:

[0048] If the specific formula for a standard airfoil is known, then x can be substituted into it. i+1 / 2 Find y i+1 / 2 Otherwise, y can be obtained using spline interpolation. i+1 / 2 .

[0049] If the blade contains a blunt trailing edge airfoil (as shown in Figure 6), the above-mentioned arc length calculation method is still applicable, but there is a difference in the calculation details: because there is a straight line segment between the upper trailing edge point 5 and the lower trailing edge point 6 of the blunt trailing edge airfoil, when using a certain number of scattered points to describe the blunt trailing edge airfoil, the upper trailing edge point 5 of the blunt trailing edge airfoil can be set as the first point of the scattered point sequence, and the lower trailing edge point 6 of the blunt trailing edge airfoil can be set as the last point of the scattered point sequence. In the process of doubling the scattered points, this straight line segment will not be subjected to doubling operations.

[0050] For each section of the blade, the arc length of the SS and PS surfaces of the standard airfoil corresponding to each section (each section has a different relative thickness) can be calculated using the cubic spline interpolation method through the corresponding "standard airfoil (SS surface, PS surface) arc length-relative thickness relationship table".

[0051] Since the actual airfoil is scaled down proportionally from the standard airfoil, the arc lengths of the SS and PS surfaces of each section can be obtained by multiplying the arc lengths of the SS and PS surfaces of the standard airfoil by a scaling factor k. Among these,

[0052] In the formula, b is the actual chord length of each section, which can be obtained during the design process, and b0 is the chord length of the standard airfoil at that section.

[0053] This yields a table showing the relationship between the arc length of the SS and PS surfaces of the blade and the distance between the blade root, as follows:

[0054] Table 3 shows the relationship between the arc length of the SS and PS surfaces of each cross section and the distance between the cross section and the blade root.

[0055] Table 3

[0056] Since the outer surface of the blade is relatively smooth, the arc lengths of the SS and PS surfaces of each cross-section can be assumed to change smoothly with the distance between the cross-section and the blade root. Therefore, the trapezoidal integration method can be directly used (or more cross-sections can be appropriately added through interpolation, and then the trapezoidal integration method can be used) to integrate the arc lengths of the SS and PS surfaces of each cross-section. If the distances between each cross-section and the blade root of a wind turbine blade are x1, x2, x3, ..., x... n-1 ,x n The corresponding airfoil SS and PS surface arc lengths are y1, y2, y3, ..., y n-1 ,y n Then the surface area of ​​the SS or PS surface of the blade is:

[0057] Alternatively, the Simpson method can be used to integrate the arc lengths of the SS and PS surfaces of each cross-section to obtain the blade surface area. The Simpson method, also known as the parabolic method, uses equally spaced quadratic or cubic parabolas to approximate the actual curve, and then calculates the area under each parabola segment using numerical integration to obtain the blade surface area. In engineering, quadratic parabolas are often used to approximate the actual curve; this calculation method is called Simpson's first method.

[0058] The principle of Simpson's first method is as follows:

[0059] As shown in Figure 7, taking points A, B, and C as examples, the surface area between the three cross-sections of the blade is calculated. The y-axis coordinates of points A, B, and C represent the arc lengths of the SS or PS surfaces of the airfoil at different positions on the wind turbine blade, and the x-axis coordinates represent the positions of the cross-sections at different positions on the wind turbine blade. The difference between the x-axis coordinates of two points is the distance between the corresponding cross-sections of the two points. Therefore, the area enclosed by curve ABC and the x-axis is the surface area of ​​the blade between the cross-sections at A and C. The specific value can be obtained by integration, as follows:

[0060] In Figure 7: x2=0 x1=-l x3=l

[0061] Let curve ABC be a quadratic parabola: y = a + bx + cx 2

[0062] The area S enclosed by curve ABC and the x-axis is:

[0063] Express the area S in terms of the known y1, y2, and y3: S = py1 + qy2 + ry3

[0064] Substituting the coordinates of points A, B, and C into the above equation, we can solve for the values ​​of p, q, and r, and then we have:

[0065] When calculating the surface area of ​​the blade, the arc lengths y1, y2, y3, ..., y of the airfoil SS or PS surfaces corresponding to the equally spaced sections of the wind turbine blade can be obtained. n-2 ,y n-1 ,y n If the distance between adjacent sections is l, then the surface area of ​​the SS or PS surface of the blade can be expressed as:

[0066] The value of the spacing between the cross sections of wind turbine blades is usually accurate to 0.1m. Therefore, l = 0.1m can be taken, and the arc length of the airfoil SS or PS surface at each cross section position can be obtained by cubic spline interpolation based on the original cross sections (such as the cross sections in Table 3). Then, the surface area of ​​the SS or PS surface of the blade can be calculated.

[0067] Other numerical integration methods can also be used to solve the problem. Theoretically, if the curve shape is closer to a parabola, the Simpson method is more accurate than the trapezoidal integral method for each micro-segment. However, this embodiment does not consider torsion, pre-bending, sweepback, etc., so it is difficult to determine which method is superior in practice. Both methods can provide a relatively accurate and rapid estimate of the blade surface area (mold area). After calculating the blade surface area, the mold area can be obtained.

[0068] In this invention, the blade may also contain multiple airfoil families. After obtaining the parameters of the wind turbine blade, the "standard airfoil (SS surface, PS surface) arc length-relative thickness relationship table" corresponding to each airfoil family is first calculated. Then, the arc length of the SS surface or PS surface of the standard airfoil corresponding to each cross section, the arc length of the SS surface or PS surface corresponding to the actual cross section, and the surface area of ​​the SS surface or PS surface of the blade are calculated.

[0069] An embodiment of the blade mold area estimation method of the present invention is summarized as follows:

[0070] First, read the geometric parameters of the wind turbine blade. The geometric parameters of the wind turbine blade include the distance between each section and the blade root (Blade radius), chord length (Chord), relative thickness (Relative Thickness), and the code of the selected airfoil (Airfoil). The required geometric parameters of the wind turbine blade are shown in Table 1.

[0071] Secondly, for a certain family of standard airfoils with different relative thicknesses, the corresponding "standard airfoil (SS surface, PS surface) arc length-relative thickness relationship table" is obtained by doubling the number of scatter points, as shown in Table 2;

[0072] For each section of the blade, the arc length of the SS and PS surfaces of the corresponding standard airfoil is calculated by interpolation using the corresponding "standard airfoil (SS surface, PS surface) arc length-relative thickness relationship table";

[0073] The arc length of the SS and PS surfaces of each section can be obtained by multiplying the arc length of the SS and PS surfaces of the standard airfoil by a scaling factor k. Thus, the relationship between the arc length of the SS and PS surfaces of each blade section and the distance between the section and the blade root is obtained, as shown in Table 3.

[0074] The trapezoidal integral method or Simpson's first method can be used to integrate the arc length of each section (SS surface or PS surface) to obtain the blade surface area, and then the mold surface area. Table 4 shows the mold area and relative error of SS surface and PS surface.

[0075] Assuming the area measured by the 3D software is a standard value, the error analysis using the method of this invention shows that the error is within 4%, which is quite good, as shown in Table 4.

[0076] Table 4

[0077] The present invention also provides a computer device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the aforementioned method for estimating the area of ​​a blade mold.

[0078] The present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the aforementioned method for estimating the area of ​​a blade mold.

[0079] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for estimating the area of ​​a blade mold, characterized in that: Includes the following steps: Read the geometric parameters of the wind turbine blade, including the distance between each section and the blade root, chord length, relative thickness, and the code of the selected airfoil; For standard airfoils with different relative thicknesses in the corresponding airfoil family, the corresponding standard airfoil arc length-relative thickness relationship table is obtained by doubling the number of scatter points. For each section of the blade, the arc lengths of the SS and PS surfaces of the standard airfoil can be calculated by interpolation using the corresponding standard airfoil arc length-relative thickness relationship table; The arc lengths of the SS and PS surfaces of the standard airfoil are multiplied by a scaling factor k to obtain the actual arc lengths of the SS and PS surfaces of each cross section. From this, a table showing the relationship between the arc lengths of the SS and PS surfaces of each blade cross section and the blade root distance is obtained. By integrating the arc lengths of the SS and PS surfaces of each cross section, the surface area of ​​the blade is obtained, which in turn determines the surface area of ​​the mold.

2. The method for estimating the area of ​​a blade mold according to claim 1, characterized in that: The formula for calculating the arc length of a standard airfoil is as follows: In the formula, L is the arc length of the airfoil segment on the SS or PS surface, (x i ,y i ) represents the coordinates of a point on the airfoil, and i represents the number of the point on the airfoil.

3. The method for estimating the area of ​​a blade mold according to claim 1, characterized in that: In the standard airfoil arc length calculation process, a certain number of scattered points are first used to describe the airfoil curve segment of the SS or PS surface, and its arc length is calculated. Then, the number of scattered points is continuously multiplied, and its arc length is calculated again. If the difference between the two arc lengths is less than the allowable error, the calculation is stopped, and the arc length of the SS or PS surface of the standard airfoil under the relative thickness is obtained; otherwise, the above process is repeated, thereby obtaining the arc length-relative thickness relationship table of the family of standard airfoils.

4. The method for estimating the area of ​​a blade mold according to claim 3, characterized in that: When doubling the number of scatter points, take: If the specific formula for the airfoil is known, then x can be substituted into it. i+1 / 2 Find y i+1 / 2 Otherwise, y can be obtained using spline interpolation. i+1 / 2 .

5. The method for estimating the area of ​​a blade mold according to claim 1, characterized in that: The arc lengths of the SS and PS surfaces of each cross section are integrated using the trapezoidal integration method. The distances x1, x2, x3, ..., x between each cross section and the blade root of the wind turbine blade are calculated. n-1 ,x n The corresponding airfoil SS or PS surface arc lengths y1, y2, y3, ..., y n-1 ,y n Then the surface area of ​​the SS or PS surface of the blade is:

6. The method for estimating the area of ​​a blade mold according to claim 1, characterized in that: The Simpson method is used to integrate the arc lengths of the SS and PS surfaces of each cross-section to obtain the blade surface area. The arc lengths of the SS or PS surfaces of each cross-section of the airfoil for a wind turbine blade with equal spacing are y1, y2, y3, ..., y n-2 ,y n-1 ,y n If the distance between adjacent sections is l, then the surface area of ​​the SS or PS surface of the blade can be expressed as:

7. The method for estimating the area of ​​a blade mold according to claim 1, characterized in that: To ensure the accuracy of the spacing between adjacent sections of a wind turbine blade to 0.1m, we can take l = 0.1m and interpolate the calculated arc length of the section to obtain the arc length of the airfoil SS or PS surface of each section. Then, we can calculate the surface area of ​​the blade SS or PS surface.

8. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, it implements the method according to any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, it implements the method of any one of claims 1 to 7.

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