CN117669229A - Blade reverse modeling method and system based on airfoil parameter extraction - Google Patents

Abstract

The invention discloses a blade reverse modeling method and a system based on wing profile parameter extraction, wherein the method comprises the following steps: scanning the blade, and extracting to obtain a blade polyhedron model; filling the blade polyhedral model and aligning a coordinate system to obtain a preprocessed polyhedral model; based on the processed polyhedral model, contour line interception and parameter extraction are carried out, and the model of the wing profile is identified; introducing key point constraint based on the airfoil model, and fitting the contour line to obtain a final contour line; reconstructing the blade model from the final contour. The system comprises: the device comprises a scanning module, a preprocessing module, an identification module, a fitting module and a reverse reconstruction module. By using the method, the model obtained by reverse modeling can be enabled to be consistent with the forward CAD blade model. The invention can be widely applied to the field of model design.

Description

Blade reverse modeling method and system based on airfoil parameter extraction

Technical Field

The invention relates to the field of model design, in particular to a blade reverse modeling method and system based on wing profile parameter extraction.

Background

The airfoil is the basic unit of the wind turbine blade, has limited model and standard in the forward design and has decisive effect on the performance of the blade. The blade is a core component for converting wind energy into mechanical energy and electric energy of the wind turbine, and accounts for about 20% -30% of the cost of the whole wind turbine, and the pneumatic performance of the blade has direct influence on the energy conversion efficiency of the wind turbine. Moreover, wind turbine blades are widely applied to water turbines at present so as to improve the energy conversion efficiency of water flow. Therefore, the reverse modeling is used for reverse modeling and redesigning of the wind turbine or the water turbine blade, and the method has important research significance for reducing the maintenance cost of the blade and improving the design and manufacturing efficiency.

In the reverse modeling stage, the contour line is extracted by curvature, and the blade is cut according to the contour line direction, so that the blade is greatly influenced by abrasion or deformation. After the parameters are extracted, the existing method is mainly to correct the parameters by removing deviation points or calculating average values through normal distribution, the model reconstructed by using the data is more similar to the model directly obtained by scanning, the forward design flow of the blade is not considered, and the model has a certain difference with the CAD model of the forward design.

Disclosure of Invention

In view of this, in order to solve the technical problem that the forward design flow of the blade is not considered in the existing reverse modeling method, and thus the reconstructed blade is not matched with the forward CAD blade model, in the first aspect, the invention provides a blade reverse modeling method based on airfoil parameter extraction, which comprises the following steps:

scanning the blade, and extracting to obtain a blade polyhedron model;

filling the blade polyhedral model and aligning a coordinate system to obtain a preprocessed polyhedral model;

based on the processed polyhedral model, contour line interception and parameter extraction are carried out, and the model of the wing profile is identified;

introducing key point constraint based on the airfoil model, and fitting the contour line to obtain a final contour line;

reconstructing the blade model from the final contour.

In some embodiments, the step of filling up and aligning the blade polyhedral model to obtain a preprocessed polyhedral model specifically includes:

filling the missing part of the blade polyhedral model, and smoothing the filled area to obtain a smoothed model;

and carrying out coordinate system alignment on the smoothed model to obtain a preprocessed polyhedral model.

Filling the edge-confirmed portion by the preferable procedure; further, the edges are not smooth after filling, and have larger errors with the real objects, so that the filled parts need to be smoothed.

In some embodiments, the step of performing coordinate system alignment on the smoothed model to obtain a preprocessed polyhedral model specifically includes:

the plane at the top surface of the polyhedron is taken as an 'x-o-z' plane, the tangent point of the front edge of the airfoil profile is taken as an original point, the chord line of the airfoil is taken as an x axis, and the direction of the vertical chord line is taken as a z axis, so that coordinate system alignment is carried out.

Through the optimization step, the fact that the upper surface of the model is taken as a coordinate plane, and the direction of the chord line of the top surface contour and the direction of the vertical chord line are taken as coordinate axes is achieved, and follow-up extraction of parameters of the contour is facilitated. The alignment operation is based on airfoil geometric characteristics, a coordinate system is independently established for each airfoil profile, alignment is not required by means of tenon and blade components, errors caused by deformation of the blades can be reduced, parameter extraction operation process is facilitated, and reverse modeling efficiency can be improved.

In some embodiments, the steps of contour line interception and parameter extraction based on the processed polyhedral model and identifying the model of the airfoil specifically comprise:

setting a section position based on the processed polyhedral model, and obtaining a contour line of a corresponding position;

and extracting parameters according to the geometric characteristics of the contour lines to obtain the airfoil model.

Wherein the parameters include relative blade thickness, relative camber, and maximum camber relative position.

Through the preferred step, parameter extraction is carried out according to geometric features of the contour lines, parameters such as relative thickness, relative camber, relative position of maximum camber and the like of the blades are measured, and therefore the airfoil model of the contour line of the section of the blades is deduced.

In some embodiments, the step of fitting the contour line to obtain a final contour line based on the key point constraint introduced by the airfoil model specifically includes:

acquiring a corresponding airfoil curve expression based on the airfoil model;

and calculating key points passed by the profile line according to the airfoil curve expression, and fitting by taking the positions of the key points as constraints to obtain the edited blade section profile line.

Wherein the airfoil model includes a symmetrical model and an asymmetrical model.

By this preferred procedure, the airfoil profile can be fitted. Similarly, for other sections, the airfoil model can be obtained through the operation, so that a series of airfoil profile lines at different positions can be obtained. After the model of the wing profile is determined, the position of a key point on the profile is calculated by using a curve expression of the model, and a profile line conforming to the wing profile standard is reconstructed by setting position constraint. The operation does not need to preset an airfoil parameter sample library, and can reduce errors generated when scanning entities to a certain extent, and can also improve modeling accuracy and modeling efficiency.

In a second aspect, the present invention also proposes a blade reverse modeling system based on airfoil parameter extraction, the system comprising:

the scanning module is used for scanning the blade and extracting to obtain a blade polyhedron model;

the preprocessing module is used for filling the blade polyhedral model and aligning a coordinate system to obtain a preprocessed polyhedral model;

the identification module is used for carrying out contour line interception and parameter extraction based on the processed polyhedral model and identifying the model of the airfoil;

the fitting module is used for introducing key point constraint based on the airfoil model and fitting the contour line to obtain a final contour line;

and the reverse reconstruction module is used for reconstructing the blade model according to the final contour line.

Based on the scheme, the invention provides a blade reverse modeling method and a system based on airfoil parameter extraction, which combine the forward design intention of a wind turbine or a water turbine blade into reverse modeling. The airfoil model is identified through extracting parameters of the section contour line, so that a three-dimensional model which is more consistent with the forward design intention can be obtained, and the performance analysis and redesign of the blade are facilitated.

Drawings

FIG. 1 is a flow diagram of a vane reverse modeling method based on airfoil parameter extraction in accordance with the present invention;

FIG. 2 is a schematic view of airfoil geometry parameters according to an embodiment of the invention;

FIG. 3 is an alignment schematic of an embodiment of the present invention;

FIG. 4 is a graphical illustration of asymmetric airfoil target parameters according to an embodiment of the invention;

FIG. 5 is a schematic illustration of a symmetrical airfoil according to an embodiment of the invention;

FIG. 6 is a schematic diagram of extraction of symmetric airfoil target parameters using the method of the invention.

Detailed Description

In addition to the forward design flow of the blade not considered in the background art, the existing reverse modeling method needs to rely on the assembly or tenon of the blade to assist in positioning alignment during the alignment stage. The alignment method is complex, and most of the components and tenons of the blades are used as main stress pieces when in work, and the components and tenons are easy to wear or deform after long-time use, so that the alignment errors are caused.

The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.

For convenience of description, only a portion related to the present invention is shown in the drawings. Embodiments and features of embodiments in this application may be combined with each other without conflict.

It should be appreciated that "system," "apparatus," "unit" and/or "module" as used in this application is one method for distinguishing between different components, elements, parts, portions or assemblies at different levels. However, if other words can achieve the same purpose, the word can be replaced by other expressions.

As used in this application and in the claims, the terms "a," "an," "the," and/or "the" are not specific to the singular, but may include the plural, unless the context clearly dictates otherwise. In general, the terms "comprises" and "comprising" merely indicate that the steps and elements are explicitly identified, and they do not constitute an exclusive list, as other steps or elements may be included in a method or apparatus. The inclusion of an element defined by the phrase "comprising one … …" does not exclude the presence of additional identical elements in a process, method, article, or apparatus that comprises an element.

In the description of the embodiments of the present application, "plurality" means two or more than two. The following terms "first", "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature.

Additionally, flowcharts are used in this application to describe the operations performed by systems according to embodiments of the present application. It should be appreciated that the preceding or following operations are not necessarily performed in order precisely. Rather, the steps may be processed in reverse order or simultaneously. Also, other operations may be added to or removed from these processes.

Referring to fig. 1, a flow chart of an alternative example of a vane reverse modeling method based on airfoil parameter extraction according to the present invention, which may be applied to a computer device, may include, but is not limited to, the following steps:

s1, scanning a blade, and extracting to obtain a blade polyhedron model;

the three-dimensional object contour data measurement technology is one of the very important steps in the reverse engineering technology, and the existing measurement technology mainly comprises two types of contact measurement and non-contact measurement. Although the contact measurement has higher measurement precision, in order to ensure that the blade does not deform to generate errors during the measurement, a non-contact data measurement mode is adopted, a three-dimensional digital laser scanning measurement technology is applied, the surface point cloud of the blade entity is collected, and the data point cloud is preprocessed; and reconstructing the blade solid model by means of three-dimensional solid modeling software and related technologies.

S2, filling the blade polyhedral model and aligning a coordinate system to obtain a preprocessed polyhedral model;

s3, carrying out contour line interception and parameter extraction based on the processed polyhedral model, and identifying the model of the airfoil;

s4, introducing key point constraint based on the airfoil model, and fitting the contour line to obtain a final contour line;

and S5, reconstructing a blade model according to the final contour line.

In the embodiment, in the model reconstruction stage, parameter extraction is carried out on the intercepted airfoil profile, the airfoil model is deduced, and fitting is carried out by taking the airfoil expression as a basis, so that the geometric characteristics of the reconstructed section profile line accord with the airfoil model standard, and a three-dimensional model is established. The model obtained by the method can be matched with a CAD model of forward design, and the airfoil profile of each section position of the blade is known, so that the subsequent redesign study is facilitated.

It should be noted that the basic knowledge of the blade design provides a theoretical basis for the reverse modeling study of the method. The cross-sectional shape perpendicular to the radial direction of the airfoil, called airfoil, is the most basic building block of a wind turbine blade, as shown in FIG. 2.

The geometry of the blade airfoil determines its aerodynamic characteristics, which play an important role in ensuring its aerodynamic characteristics, so that the reverse modeling nature of the blade is the derivation and exact reconstruction of the blade airfoil geometry. The geometric definition of an airfoil includes the following aspects:

(1) Leading edge a: the front end point of the airfoil.

(2) Trailing edge B: the tail of the wing, the point furthest from the leading edge.

(3) String C: straight lines connecting the leading and trailing edges of the airfoil. The length of the string is called the chord length c.

(4) Thickness h: the maximum distance between the upper and lower surfaces of the airfoil in the direction of the normal to the chord line.

(5) Midline (mean camber line) D: the midline or camber line of an airfoil is a curve joining the leading and trailing edges. In the direction of the normal to the chord line, the points on the curve are equidistant from the upper and lower surfaces of the airfoil. If the midline is a straight line, the airfoil is vertically symmetrical, and the midline coincides with the chord; otherwise the airfoil is asymmetric, known as a cambered airfoil.

(6) Camber d: the maximum vertical distance from each point on the centerline to the chord line is called the maximum camber of the airfoil, abbreviated camber.

(7) Relative camber m: the ratio of the maximum camber of the airfoil to the chord of the airfoil.

When the wind turbine blade is designed in the forward direction, the chord length of the airfoil profile at the rotating radius is calculated according to the rotating radius of the blade. Next, a series of airfoil profiles are provided in the spanwise direction of the blade, each airfoil profile being selectable for a particular airfoil model, such as the common airfoils of NACA and Clark-Y, and the like, depending upon design requirements. The aerodynamic performance and application of each airfoil may be different, but after the chord length is determined, accurate values of other parameters can be obtained through an airfoil curve expression or an airfoil coordinate table.

In some possible embodiments, the step S2 specifically includes:

s2.1, filling the missing part of the blade polyhedral model, and smoothing the filled region to obtain a smoothed model.

The polyhedral model obtained by scanning is imported into software, and the part of the edge of the polyhedral model of the blade, which is missing, is repaired by using a surface filling function, and the filling mode of bridging is selected because the curvature change of the edge of the curved surface is large. After filling, the edge is not smooth and has larger error with the real object, so that the filled part needs to be smoothed, and the smoothing function of software is used.

S2.2, carrying out coordinate system alignment on the smoothed model to obtain a preprocessed polyhedral model.

In some possible embodiments, the step S2.2 specifically includes:

s2.2, taking a plane at the top surface of the polyhedron as an 'x-o-z' plane, taking a tangent point at the front end of the profile of the airfoil as an origin, taking an airfoil chord line as an x axis, and taking the direction of a vertical chord line as a z axis, and aligning a coordinate system.

The first step in blade redesign is to adjust the working coordinate system based on the reference features. The scanning of the blade model is done in an arbitrary coordinate system, but its position and orientation have a crucial role for the subsequent parameter extraction. Therefore, the patch file needs to be aligned in the coordinate system in the reverse modeling software.

In order to realize convenient parameter extraction after alignment, the airfoil chord line is used as the x-axis for alignment.

Firstly, selecting the upper surface fitting of a patch to generate a plane, establishing a patch sketch in the plane, and cutting a polygon to obtain a reference airfoil profile line of the upper surface position. Then, a curvature analysis function is used, and a point with the largest curvature of the rear end is found according to curvature calculation, namely the tail of the airfoil, and the tail is taken as the rear edge B.

And drawing a circle tangent to the front end of the wing profile by taking the rear edge point B as a circle center, and connecting the circle center with the tangent point. The radius is the longest line segment passing through the center of the circle in the semicircle, and the tangent point is the point with the largest distance between the front end and the rear edge of the airfoil, namely the front edge A of the airfoil, and the straight line connecting the front edge A and the rear edge A is the chord line.

Next, in the reverse modeling software such as Geomagic Design X, the coordinate system alignment is performed using the "x-y-z" alignment method, using the plane at the top surface of the polyhedron as the "x-o-z" plane, using the tangent point of the front end of the airfoil profile as the origin, using the extracted chord line as the x-axis, and using the direction of the vertical chord line as the z-axis, as shown in fig. 3.

After the alignment step, the method takes the upper surface of the model as a coordinate plane and takes the chord line direction of the top surface contour and the direction of the vertical chord line as coordinate axes, thereby being beneficial to the subsequent extraction of the parameters of the contour.

In some possible embodiments, the step S3 specifically includes:

s3.1, setting a section position based on the processed polyhedral model, and obtaining a contour line of a corresponding position;

and S3.2, extracting parameters according to the geometric characteristics of the contour lines to obtain the airfoil model.

In this embodiment, in the model reconstruction stage, according to the rule of the airfoil model defined by the camber, vertical lines are drawn at the chord line ten-dividing points, the midpoints of the vertical lines are sequentially connected, and the maximum distance from the connecting line to the chord line, namely the camber, is measured. And whether the airfoil is of a symmetrical type can be judged by whether the camber is 0. If the thickness is asymmetric, according to the thickness definition, the maximum thickness and the position thereof can be obtained by subtracting Y coordinates of the same X coordinate point. And identifying the model of the airfoil by the extracted parameters, and determining the airfoil model. If the profile line is symmetrical, the external rectangle of the profile line can be directly drawn, the chord length and the thickness of the airfoil are respectively obtained by measuring the length and the width of the rectangle, the relative thickness is obtained by dividing the thickness by the chord length, and then the airfoil model is determined.

The patch file is truncated and the position profile is obtained by setting the position of the cross section using an equidistant truncation function in inverse modeling software such as Geomagic Design X. And selecting a mode of 'N equal division among planes' in a 'section' function, and carrying out N equal division interception on the upper surface and the lower surface of the blade polyhedral model.

Before the profile is subjected to wing profile identification, a series of obtained profile lines are extracted into the same 3d sketch. And (3) using a conversion entity function, selecting all the curves by a frame, and extracting the contour lines into the newly-built 3d sketch. After the extraction is completed, each intercepted contour line can be independently edited.

The extraction process is described below using NACA airfoil as an example. The airfoil is a commonly used airfoil, has a rich database, has the advantage that the surface of the airfoil can be described in an analysis way, and is widely applied to the design of wind turbines, turbine blades and wings. The airfoil used for the blade is known as a NACA 4-digit airfoil profile. The numbering rules determine the geometry of the airfoil, taking the airfoil NACA4421 as an example, the four digits have the meaning of 4% maximum relative camber of the airfoil, 0.4% relative position of maximum camber, and 21% relative thickness of the airfoil, respectively.

For chord length, the chord length c is obtained by measuring the distance between the front and rear ends of the airfoil profile and the intersection point of the X axis in the previous alignment step to align the chord line as the X axis. The definition of model can obtain that the maximum camber relative position is determined by the number 2 digit of the airfoil, namely, the airfoil appears at the ten-dividing point of the chord line, so that a sketch is established by taking the upper view plane as a reference, the ten-dividing point of the chord line is intersected with the contour line to obtain 9 line segments, the midpoints of the 9 line segments are sequentially connected, the central line (mean camber line) of the airfoil of the blade can be obtained, as shown in figure 4, the maximum camber d and the maximum camber position b of the airfoil model can be deduced by measuring the maximum vertical distance from the central line to the chord line, the maximum relative camber m can be obtained by dividing the camber d by the chord length c, and the maximum camber position b is divided by the chord length c to obtain the maximum camber relative position p. From this, the airfoil may be calculated to have a first number of 100m and a second number of 10p, and if the calculation result of 100m or 10p is not an integer, rounding is performed according to the rounding method.

In particular, the characteristics of the airfoil can be classified into symmetrical and asymmetrical cases.

1) Asymmetric model: for the extraction of the thickness h and the relative thickness t, the coordinates of each point on the airfoil profile are derived, and the Y coordinates of the same points of the X coordinates are subtracted. The chord line is taken as an X axis, the front edge is taken as an original point, when the difference value of the Y coordinates obtained by definition is maximum, the maximum thickness h is the difference value, the corresponding X coordinate is the position of the maximum thickness a, and the relative thickness t can be obtained by dividing the thickness h by the chord length c. The last two digits of the wing shape are 100t, so that the accurate wing shape model can be obtained.

2) Symmetrical model: if the distances from the middle point of the cross-bisector of the blade to the chord line are all close to 0, the distance from the middle line of the airfoil to the chord line can be regarded as zero. The camber d of the profile of the airfoil is 0, the maximum relative camber m and its relative position p are all 0, and the airfoil can be determined to be symmetrical, namely NACA00 series. Fig. 5 is a symmetrical airfoil schematic. Because the centerline and chord line of the airfoil coincide, i.e., are symmetrical models, to increase the extraction efficiency of the parameter thickness h and chord length c, a minimum circumscribed rectangle method for drawing the contour line of the airfoil can be used to make each side of the rectangle tangent constraint with the contour, as shown in fig. 6. Since the chord line direction is horizontal, the chord length c and thickness h of the airfoil profile can be obtained by measuring the length and width of the rectangle. Meanwhile, the tangent point of the contour line and the upper and lower sides of the rectangle is taken as the position a where the maximum thickness of the airfoil is located. By measuring the chord length c and the thickness h, calculating the ratio of the thickness to the chord length, i.e. the relative thickness t, the exact model of the airfoil profile can be determined.

In some possible embodiments, the step S4 specifically includes:

s4.1, acquiring a corresponding airfoil curve expression based on the airfoil model;

and S4.2, calculating key points passing by the profile line according to the airfoil curve expression, and fitting by taking the positions of the key points as constraints to obtain the edited blade section profile line.

After the accurate model is obtained, the maximum relative bending m, the relative position p of the maximum bending and the relative thickness t are substituted into an equation, and the position coordinates of the non-special points are obtained.

Symmetrical NACA airfoil curve expression (shape equation y _t ) Is that：

The shape equation used to generate an asymmetric NACA four-digit airfoil is the same as the equation for a00 XX symmetric airfoil, except that the camber line of the asymmetric airfoil is curved. Wherein the arc equation y _c The method comprises the following steps:

wherein: m represents the maximum relative camber (100 m is the first digit of the four-digit airfoil), p represents the position of the maximum camber (10 p is the second digit of the four-digit airfoil), and x represents the coordinate value of the curve in the chord line direction.

For the airfoil with camber, since its thickness is perpendicular to the camber line direction, the coordinates (x _U ,y _U ) And (x) _L ,y _L ) The method comprises the following steps of:

wherein the method comprises the steps of

When the asymmetric airfoil redraws the fitted contour, the contour is required to pass through special points: the leading edge, trailing edge and the point of maximum thickness. Secondly, substituting the extracted chord length c, the maximum relative camber m and the relative position p of the maximum camber into the airfoil expressions (2) and (5) to obtain a mean camber line equation y _c And then y is _c Substituting into the formula (1) to obtain the shape equation y _t . Then the mean camber line equation y to be found _c And shape equation y _t Substituting the non-special points into the formulas (3) and (4), solving the coordinates of the non-special points, setting the coordinates as point constraints, and finally connecting the points in sequence to obtain the complete airfoil profile.

The redrawn contour must pass through the special points that have been found: a leading edge, a trailing edge, and a maximum thickness location point. And substituting the extracted chord length c and the relative thickness t into the airfoil expression (1), and obtaining the coordinates of any non-special point on the airfoil profile line through the expression, thereby obtaining the point set point constraint with proper quantity. Finally, connecting the points in sequence by using a spline curve, and fitting the obtained airfoil profile.

In some possible embodiments, the step S5 specifically includes:

and (3) using a lofting command in software from the contour line to the curved surface, taking the previously obtained airfoil contour line as a lofting contour line, and sequentially connecting the front edge of the contour line as a lofting path to obtain the reconstructed blade model.

A blade reverse modeling system based on airfoil parameter extraction, comprising:

the scanning module is used for scanning the blade and extracting to obtain a blade polyhedron model;

the preprocessing module is used for filling the blade polyhedral model and aligning a coordinate system to obtain a preprocessed polyhedral model;

the identification module is used for carrying out contour line interception and parameter extraction based on the processed polyhedral model and identifying the model of the airfoil;

the fitting module is used for introducing key point constraint based on the airfoil model and fitting the contour line to obtain a final contour line;

and the reverse reconstruction module is used for reconstructing the blade model according to the final contour line.

The content in the method embodiment is applicable to the system embodiment, the functions specifically realized by the system embodiment are the same as those of the method embodiment, and the achieved beneficial effects are the same as those of the method embodiment.

Blade reverse modeling device based on airfoil parameter extraction:

at least one processor;

at least one memory for storing at least one program;

the at least one program, when executed by the at least one processor, causes the at least one processor to implement a blade reverse modeling method based on airfoil parameter extraction as described above.

The content in the method embodiment is applicable to the embodiment of the device, and the functions specifically realized by the embodiment of the device are the same as those of the method embodiment, and the obtained beneficial effects are the same as those of the method embodiment.

A storage medium having stored therein processor-executable instructions which, when executed by a processor, are for implementing a blade reverse modeling method based on airfoil parameter extraction as described above.

The content in the method embodiment is applicable to the storage medium embodiment, and functions specifically implemented by the storage medium embodiment are the same as those of the method embodiment, and the achieved beneficial effects are the same as those of the method embodiment.

While the preferred embodiment of the present invention has been described in detail, the invention is not limited to the embodiment, and various equivalent modifications and substitutions can be made by those skilled in the art without departing from the spirit of the invention, and these modifications and substitutions are intended to be included in the scope of the present invention as defined in the appended claims.

Claims (8)

1. The blade reverse modeling method based on airfoil parameter extraction is characterized by comprising the following steps of:

scanning the blade, and extracting to obtain a blade polyhedron model;

filling the blade polyhedral model and aligning a coordinate system to obtain a preprocessed polyhedral model;

based on the processed polyhedral model, contour line interception and parameter extraction are carried out, and the model of the wing profile is identified;

introducing key point constraint based on the airfoil model, and fitting the contour line to obtain a final contour line;

reconstructing the blade model from the final contour.

2. The method for reverse modeling of a blade based on extraction of airfoil parameters according to claim 1, wherein the step of filling and coordinate system alignment of the blade polyhedral model to obtain a preprocessed polyhedral model specifically comprises the following steps:

filling the missing part of the blade polyhedral model, and smoothing the filled area to obtain a smoothed model;

and carrying out coordinate system alignment on the smoothed model to obtain a preprocessed polyhedral model.

3. The method for reverse modeling of a blade based on extraction of airfoil parameters according to claim 1, wherein the step of aligning the smoothed model in a coordinate system to obtain a preprocessed polyhedral model specifically comprises:

the plane at the top surface of the polyhedron is taken as an 'x-o-z' plane, the tangent point of the front edge of the airfoil profile is taken as an original point, the chord line of the airfoil is taken as an x axis, and the direction of the vertical chord line is taken as a z axis, so that coordinate system alignment is carried out.

4. The method for reverse modeling of a blade based on airfoil parameter extraction according to claim 1, wherein the steps of contour line interception and parameter extraction based on the processed polyhedral model and identifying an airfoil model specifically comprise:

setting a section position based on the processed polyhedral model, and obtaining a contour line of a corresponding position;

and extracting parameters according to the geometric characteristics of the contour lines to obtain the airfoil model.

5. The method of claim 4, wherein the parameters include relative thickness, relative camber and maximum camber relative position.

6. The method for reverse modeling of a blade based on extraction of airfoil parameters according to claim 1, wherein the step of fitting a contour line to obtain a final contour line by introducing a key point constraint based on the airfoil model specifically comprises:

acquiring a corresponding airfoil curve expression based on the airfoil model;

and calculating key points passed by the profile line according to the airfoil curve expression, and fitting by taking the positions of the key points as constraints to obtain the edited blade section profile line.

7. The method of reverse modeling a blade based on extraction of airfoil parameters according to claim 6, wherein the airfoil model comprises a symmetric model and an asymmetric model.

8. A blade reverse modeling system based on airfoil parameter extraction, comprising:

the scanning module is used for scanning the blade and extracting to obtain a blade polyhedron model;

the preprocessing module is used for filling the blade polyhedral model and aligning a coordinate system to obtain a preprocessed polyhedral model;

the identification module is used for carrying out contour line interception and parameter extraction based on the processed polyhedral model and identifying the model of the airfoil;

the fitting module is used for introducing key point constraint based on the airfoil model and fitting the contour line to obtain a final contour line;

and the reverse reconstruction module is used for reconstructing the blade model according to the final contour line.