Propeller geometry feature extraction and surface reconstruction method

Abstract

The application provides a propeller geometry feature extraction and curved surface reconstruction method, and the geometry feature extraction method specifically comprises the following steps: S1, using a ring cutting procedure, a cylinder with a bottom surface radius equal to r is used to cut the propeller blade at different radial positions r, and the cross section obtained after the ring cutting is unfolded along a propeller reference line in a three-dimensional coordinate system to obtain a wing profile corresponding to the propeller blade at the different radial positions r; S2, the wing profile is subjected to a pitch unitization deformation; S3, the maximum thickness t and the maximum camber c of the wing profile are read by a program; S4, the wing profile corresponding to the propeller blade at an arbitrary radial position r is taken, and the wing profile chord length, thickness and camber are subjected to a unitization deformation to obtain an initial airfoil corresponding to the propeller blade in a propeller three-dimensional model. The technical scheme of the application can realize reverse transformation from a propeller entity model to geometry feature parameters and curved surface reconstruction of the propeller blade, so as to analyze the relationship between the propeller geometry features and the performance.

Description

Technical Field

[0001] This invention relates to the field of ship propulsion technology, and more particularly to a method for extracting propeller geometric features and reconstructing curved surfaces. Background Technology

[0002] Ellande Tang et al. used 3D scanning technology to perform photogrammetry of propeller blade parameters and extract propeller geometry, but this method requires sophisticated equipment. Zhang Hongwei et al. proposed a program design method for calculating propeller profile coordinates, manually importing data files into ProE software for solid modeling, but the blade representation still uses three-dimensional coordinate points. Cheng Dong et al. conducted secondary development on UG / Grip, exploring key technologies for propeller modeling, and reasonably processing key parts such as the blade tip and root transitions to establish an accurate three-dimensional propeller model. Wu Lihong et al. used MATLAB to calculate propeller blade spatial coordinates, importing the spatial coordinates in one go through ProE, but failed to extract accurate feature parameters, requiring manual creation of a three-dimensional solid propeller. Liu Yongjie et al. manually calculated blade profile points using Excel, and wrote a program in VB.NET to import the profile coordinate data from Excel into CATIA to generate profile cloud maps. Liu Kanle et al. combined PropCAD and Rhino software to study a rapid method for propellers, but could not parametrically represent the propeller.

[0003] Current research only extracts the three-dimensional coordinates of propeller blades, without extracting propeller characteristic parameters and initial airfoil configuration. This is not conducive to flexible control of propeller geometry in the later stages, and it is impossible to change the solid model by changing the characteristic parameters, nor can it establish the relationship between propeller geometry and propeller performance. Summary of the Invention

[0004] In view of the technical problems existing in the prior art, a method for extracting propeller geometric features and reconstructing surfaces is provided.

[0005] The technical means employed in this invention are as follows:

[0006] A method for extracting the geometric features of a propeller, specifically including the following steps:

[0007] S1. Establish a three-dimensional coordinate system xyz in the modeling software, place the three-dimensional model of the target propeller into the three-dimensional coordinate system, and make the propeller shaft and propeller reference line of the three-dimensional model coincide with the x-axis and y-axis of the three-dimensional coordinate system respectively. The coordinates of any point A0 on the blade in the three-dimensional model of the propeller in the three-dimensional coordinate system are (x0, y0, z0).

[0008] A ring-cutting program, developed in the modeling software, is used to perform ring-cutting on the blade at different radial positions r using a cylinder with a base radius equal to r. The central axis of the cylinder coincides with the propeller shaft of the three-dimensional propeller model. The cross-section obtained after ring-cutting is then unfolded along the propeller reference line in the three-dimensional coordinate system to obtain the airfoil corresponding to the blade at different radial positions r.

[0009] S2. Develop a pitch-normalization deformation program in the modeling software to perform pitch-normalization deformation on the airfoil sections corresponding to different radial positions r of the blade obtained in S1:

[0010] (1) The program reads the chord length and position of the airfoil at different radial positions r of the blade, as well as the pitch angle β.

[0011] (2) The pitch normalization deformation program includes a function that allows the airfoil to rotate about the origin of the three-dimensional coordinate system by a pitch angle β. Based on the length and position of the chord length of the airfoil, the midpoint of the chord length is determined, and then the function is applied. The airfoil is rotated around the origin of the three-dimensional coordinate system by a pitch angle β, and then the pitch x of the airfoil is read through the program. r Lateral tilt θ s and pitch;

[0012] S3. Using a program developed in the modeling software, the airfoil corresponding to different radial positions r of the blade after pitch unit deformation is uniformly divided into n parts along the thickness direction. The maximum distance between the dividing line and the upper and lower intersection points of the airfoil is taken, and the maximum thickness t and maximum camber c of the airfoil are read by the program.

[0013] S4. Take the airfoil at any radial position r of the blade, and use a program developed in the modeling software to perform unitized deformation of the airfoil's chord length, thickness, and camber. Specifically, this includes:

[0014] Based on the chord length, maximum thickness t, and maximum camber c of the airfoil obtained from S2 and S3, the airfoil is scaled in the three-dimensional coordinate system to complete the unitized deformation of the airfoil chord length and thickness. Then, the degree of curvature of the airfoil is controlled by the camber control curve function f(x) included in the program to remove the influence of camber on the airfoil, thereby completing the unitized deformation of the airfoil camber. Finally, the initial airfoil corresponding to the blade in the three-dimensional model of the propeller is obtained, thus completing the extraction of the propeller's geometric features.

[0015] Furthermore, in S1, the coordinates of any point A0 at different radial positions r of the blade, after being circumferentially cut and unfolded, become A1(x1, y1, z1) using the following formula:

[0016]

[0017] Where x1 represents the absolute value of the x-coordinate of point A1; α represents the angle between the line connecting point A0 and the origin of the three-dimensional coordinate system and the y-axis.

[0018] Furthermore, in S2, the program reads the longitudinal tilt x of the airfoil section. r First, the total longitudinal tilt value x of the airfoil section is measured. T Then, the longitudinal tilt x of the airfoil is obtained using the following formula. r :

[0019] x T =x r +rθ s tanβ.

[0020] Furthermore, in S2, after pitch-normalized deformation, the coordinates of points on the airfoil section are transformed into A2(x2, y2, z2) using the following formula:

[0021]

[0022] Furthermore, in S4, after normalized deformation of the chord length, thickness, and camber, the coordinates of points on the flange section are transformed into A using the following formula:

[0023] A(x,y,z)=(f(x2) / t,y2,z2 / c).

[0024] The present invention also provides a propeller surface reconstruction method, which adopts the propeller geometric feature extraction method, including obtaining the initial airfoil corresponding to the blade of the target propeller using the propeller geometric feature extraction method, and reconstructing the blade of the target propeller surface using the initial airfoil as needed to reconstruct the three-dimensional model of the target propeller.

[0025] The specific steps for reconstructing the propeller blade surface using the initial airfoil, as needed, include:

[0026] S1' Based on the geometric features of the airfoil at each radial position r of the target propeller blade obtained using the propeller geometric feature extraction method: chord length, pitch x r Lateral tilt θ s For each geometric feature, including pitch, maximum thickness t, and maximum camber c, an original parameter curve representing the radial distribution of the blade geometry of the target propeller is formed. The original parameter curve corresponding to each geometric feature is fitted using F-spline curve fitting to obtain the fitted parameter curve corresponding to each geometric feature.

[0027] S2' By developing a program in the modeling software, the fitting parameter curves corresponding to the geometric features obtained in S1' are used to parametrically model the blades of the target propeller. The shape of each fitting parameter curve is adjusted according to the requirements of the geometric features of the reconstructed propeller blades, thereby realizing the surface reconstruction of the propeller blades and thus reconstructing the three-dimensional model of the target propeller.

[0028] Furthermore, S2' specifically includes:

[0029] (1) In a three-dimensional coordinate system, a program developed in the modeling software is used to assign values ​​to the chord length, maximum thickness, and maximum camber of the initial airfoil at each radial position r of the blade. The initial airfoil is then fitted with the chord length, maximum thickness, and maximum camber values ​​corresponding to the adjusted chord length, maximum thickness (t′), and maximum camber (c′) at the radial position r. This process yields the two-dimensional deformable airfoil at each radial position r of the blade, specifically including:

[0030] The program controls the initial airfoil to scale based on the chord length and maximum thickness values ​​to assign the chord length and maximum thickness; and the program uses the camber control curve function f(x) to control the degree of curvature of the initial airfoil based on the maximum camber value to assign the maximum camber.

[0031] After assigning values ​​to the chord length, maximum thickness, and maximum camber, the coordinates (x0′, y′0, z′0) of any point A0′ on the initial airfoil in the three-dimensional coordinate system are transformed into A1′(x1′, y1′, z1′) using the following formula:

[0032] A1′(x1′,y1′,z1′)=(f(t′x0′),y0′,c′z′0)

[0033] (2) Using a program developed in the modeling software, the fitted parameter curves corresponding to the pitch, skew, and pitch after adjusting according to the requirements of the geometric characteristics of the reconstructed propeller blades are obtained. The pitch value x at the radial position r is obtained. r ′, the value of lateral tilt θ s The values ​​of pitch β′ and the pitch angle β′ corresponding to the pitch are used to assign pitch, skew, and pitch values ​​to the two-dimensional deformable airfoil at each radial position r of the blade, thereby obtaining the reconstructed airfoil at each radial position r of the blade; the program includes a function to rotate the two-dimensional deformable airfoil about the origin of the three-dimensional coordinate system by the pitch angle β′.

[0034] Specifically, this includes: obtaining the midpoint position of the chord length of the two-dimensional deformable airfoil through a program, and then using a function... The pitch angle β′ of the two-dimensional deformable airfoil is controlled to rotate around the origin of the three-dimensional coordinate system. Then, the pitch, skew and pitch of the two-dimensional deformable airfoil are assigned by the program.

[0035] After assigning values ​​to the pitch, skew, and lead angle, the coordinates of a point on the two-dimensional deformable airfoil are transformed into A2′(x2′, y′2, z′2) using the following formula:

[0036]

[0037] (3) Using a roll-up program developed in the modeling software, the reconstructed airfoil at each radial position r of the blade is rolled up using a cylinder with a bottom radius equal to r to obtain the reconstructed section of the blade at each radial position r.

[0038] The coordinates of points on the reconstructed airfoil after winding are transformed into A′(x′,y′,z′) using the following formula:

[0039]

[0040] Where x′ represents the absolute value of the x-coordinate of point A′; α′ represents the angle between the line connecting A2′ and the origin of the three-dimensional coordinate system and the y-axis;

[0041] (4) In the modeling software, the reconstructed cross sections corresponding to each radial position r of the blade are smoothly joined to complete the surface reconstruction of the blade of the target propeller. Then, multiple reconstructed blades are arranged according to the number of blades of the target propeller to realize the reconstruction of the three-dimensional model of the target propeller.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] The propeller geometric feature extraction and surface reconstruction method provided by this invention can realize the reverse transformation from the propeller solid model to geometric feature parameters. Through a secondary development program, the propeller blades are circumferentially cut and unfolded to obtain an airfoil. By geometrically deforming and reading the airfoil, the geometric features of the blades (chord length, thickness, camber, pitch, skew, and pitch) are extracted to obtain the initial airfoil of the propeller. Simultaneously, by fitting the corresponding parameter curves based on the extracted propeller geometric features, the surface reconstruction of the propeller blades can be achieved. During the surface reconstruction process, this invention defines the propeller geometric features as control variables that can control the geometric changes of the propeller solid model. By changing the geometric feature parameters, the relationship between the propeller geometric features and performance can be analyzed.

[0044] Based on the above reasons, this invention can be widely applied in fields such as wings, rudder blades, impellers, and pump blades in aviation, aerospace, marine, and industrial energy and power sectors. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a schematic diagram of the geometric features of a propeller blade.

[0047] Figure 2 This is a schematic diagram showing the relationship between α and the coordinates of point A0 in the propeller geometric feature extraction method described in this invention.

[0048] Figure 3 This is a schematic diagram of the blade circumferential cutting process in the propeller geometric feature extraction method of the present invention.

[0049] Figure 4 This is a comparison chart of the actual chord length of the propeller blades and the chord length extracted using the propeller geometric feature extraction method described in this invention.

[0050] Figure 5 This is a comparison chart of the actual pitch of the propeller blades and the pitch extracted using the propeller geometric feature extraction method described in this invention.

[0051] Figure 6 This is a schematic diagram of the fitting parameter curves corresponding to the geometric features obtained by the propeller geometric feature extraction method described in this invention.

[0052] Figure 7 This is a schematic diagram of the fully parameterized propeller blades of the present invention. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. 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.

[0054] Example 1

[0055] A propeller is a three-dimensional solid formed by stretching and rotating an airfoil in space; typically, the radial distribution of geometric features corresponding to each radial airfoil section is given to represent the entire propeller; for example... Figure 1 As shown, the design variables for propeller blades are mainly used to express and locate the shape of the corresponding airfoil section. Chord, maximum thickness, and maximum camber can express the shape of the airfoil section, while rake, skew, and pitch can accurately represent the distribution of the propeller in the circumferential, axial, and radial directions of each blade section. The straight line connecting the center points of the chord lines of the airfoil without skew or rake is called the blade reference line. The straight line connecting the center points of the chord lines of the actual propeller airfoil is called the propeller reference line. The longitudinal distance between the blade reference line and the propeller reference line is called the rake. The angle formed by the blade reference line and the propeller reference line in the frontal view direction is called the skew. Take a blade section, extend the chord line of the blade section, and wrap it around the axis. The axial distance between the two ends of the spiral formed is the pitch of the blade in that radial section.

[0056] This invention provides a method for extracting the geometric features of a propeller, specifically including the following steps:

[0057] S1. Establish a three-dimensional coordinate system xyz in the modeling software, place the three-dimensional model of the target propeller into the three-dimensional coordinate system, and make the propeller shaft and propeller reference line of the three-dimensional model coincide with the x-axis and y-axis of the three-dimensional coordinate system respectively. The coordinates of any point A0 on the blade in the three-dimensional model of the propeller in the three-dimensional coordinate system are (x0, y0, z0).

[0058] A circumferential cutting program, developed in modeling software, is used to perform circumferential cutting on the blade at different radial positions r using cylinders with a base radius equal to r (e.g., ...). Figure 3 As shown), the central axis of the cylinder coincides with the propeller shaft of the 3D propeller model. The cross-section obtained after circumferential cutting is unfolded along the propeller reference line in the 3D coordinate system to obtain the airfoil corresponding to different radial positions r of the blade. The coordinates of any point A0 at different radial positions r of the blade become A1(x1, y1, z1) after circumferential cutting and unfolding using the following formula:

[0059]

[0060] Where x1 represents the absolute value of the x-coordinate of point A1; α represents the angle between the line connecting point A0 and the origin of the three-dimensional coordinate system and the y-axis, such as... Figure 2 As shown;

[0061] S2. Develop a pitch-normalization deformation program in the modeling software to perform pitch-normalization deformation on the airfoil sections corresponding to different radial positions r of the blade obtained in S1:

[0062] (1) The program reads the chord length and position of the airfoil at different radial positions r of the blade, as well as the pitch angle β.

[0063] (2) The pitch normalization deformation program includes a function that allows the airfoil to rotate about the origin of the three-dimensional coordinate system by a pitch angle β. Based on the length and position of the chord length of the airfoil, the midpoint of the chord length is determined, and then the function is applied. The airfoil is rotated around the origin of the three-dimensional coordinate system by a pitch angle β, and then the pitch x of the airfoil is read through the program. r Lateral tilt θ s And the pitch, after pitch normalization deformation, the coordinates of the points on the airfoil section are transformed into A2(x2, y2, z2) by the following formula:

[0064]

[0065] S3. Using a program developed in the modeling software, the airfoil corresponding to different radial positions r of the blade after pitch unit deformation is uniformly divided into n parts along the thickness direction. The maximum distance between the dividing line and the upper and lower intersection points of the airfoil is taken, and the maximum thickness t and maximum camber c of the airfoil are read by the program.

[0066] S4. Take the airfoil at any radial position r of the blade, and use a program developed in the modeling software to perform unitized deformation of the airfoil's chord length, thickness, and camber. Specifically, this includes:

[0067] Based on the chord length, maximum thickness t, and maximum camber c of the airfoil obtained from S2 and S3, the airfoil is scaled in a three-dimensional coordinate system to complete the unitized deformation of the chord length and thickness. Then, using the camber control curve function f(x) included in the program to control the camber, the curvature of the airfoil is controlled, eliminating the influence of camber on the airfoil, thus completing the unitized deformation of the airfoil camber. Finally, the initial airfoil corresponding to the blade in the propeller's three-dimensional model is obtained. This completes the extraction of the propeller's geometric features. After the unitized deformation of the chord length, thickness, and camber, the coordinates of points on the airfoil are transformed into A using the following formula:

[0068] A(x,y,z)=(f(x2) / t,y2,z2 / c).

[0069] Furthermore, in S2, the program reads the longitudinal tilt x of the airfoil section. r At that time, firstly according to Figure 1 Measure the total longitudinal pitch value x of the airfoil section T Then, the longitudinal tilt x of the airfoil is obtained using the following formula. r :

[0070] x T =xr +rθ s tanβ.

[0071] Furthermore, the function described in this invention for rotating the airfoil about the origin of the three-dimensional coordinate system by a pitch angle β Both the camber control curve function f(x) used to control the camber of the airfoil can be implemented in 3D modeling software through programming, and will not be elaborated further in this invention.

[0072] The propeller geometric feature extraction method described in this invention can extract geometric feature parameters of different propeller models. In particular, for special propellers with unconventional airfoils or blades with unknown feature parameters, the extracted geometric feature parameters can be used for further parametric modeling and optimization design of the propeller. The feature extraction process is carried out automatically by the modeling software program, which better realizes the rapid conversion between the propeller solid model and geometric features.

[0073] By comparing the data of chord length and pitch of a propeller blade extracted using the propeller geometric feature extraction method described in this invention with the actual data of the propeller blade, the comparison results are as follows: Figure 4-5 As shown, the feature data extracted using the method provided by this invention has a small error and is reliable.

[0074] Example 2

[0075] like Figure 7 As shown, the present invention also provides a propeller surface reconstruction method, which adopts the propeller geometric feature extraction method, including obtaining the initial airfoil corresponding to the blade of the target propeller using the propeller geometric feature extraction method, and reconstructing the blade of the target propeller surface using the initial airfoil as needed, thereby reconstructing the three-dimensional model of the target propeller. The three-dimensional model of the target propeller reconstructed as needed can be used to analyze the relationship between propeller geometric features and propeller performance.

[0076] The specific steps for reconstructing the propeller blade surface using the initial airfoil, as needed, include:

[0077] S1' Based on the geometric features of the airfoil at each radial position r of the target propeller blade obtained using the propeller geometric feature extraction method: chord length, pitch x r Lateral tilt θ s For each geometric feature, including pitch, maximum thickness t, and maximum camber c, an original parameter curve representing the radial distribution of the target propeller blade geometry is generated. Then, an F-spline curve fitting method is used to fit the original parameter curves corresponding to each geometric feature, resulting in the fitted parameter curve for each geometric feature, as shown below. Figure 6As shown, the error between the fitted parameter curve obtained by spline curve fitting and the original parameter curve is small, which can ensure that the radial distribution curves corresponding to each geometric feature have good smoothness, and is more conducive to expressing the geometric features of the propeller in a parametric way in the later stage, so as to establish the relationship between the propeller solid model and the geometric features.

[0078] S2' By developing a program in the modeling software, the fitting parameter curves corresponding to the geometric features obtained in S1' are used to parametrically model the blades of the target propeller. Based on the requirements for the geometric features of the reconstructed propeller blades, the shape of each fitting parameter curve is adjusted, such as the fullness, area, and end point coordinates of the fitting parameter curves, so as to realize the surface reconstruction of the propeller blades and thus reconstruct the three-dimensional model of the target propeller.

[0079] Furthermore, S2' specifically includes:

[0080] (1) In a three-dimensional coordinate system, a program developed in the modeling software is used to assign values ​​to the chord length, maximum thickness, and maximum camber of the initial airfoil at each radial position r of the blade. The initial airfoil is then fitted with the chord length, maximum thickness, and maximum camber values ​​corresponding to the adjusted chord length, maximum thickness (t′), and maximum camber (c′) at the radial position r. This process yields the two-dimensional deformable airfoil at each radial position r of the blade, specifically including:

[0081] The program controls the initial airfoil to scale based on the chord length and maximum thickness values ​​to assign the chord length and maximum thickness; and the program uses the camber control curve function f(x) to control the degree of curvature of the initial airfoil based on the maximum camber value to assign the maximum camber.

[0082] After assigning values ​​to the chord length, maximum thickness, and maximum camber, the coordinates (x0′, y′0, z′0) of any point A0′ on the initial airfoil in the three-dimensional coordinate system are transformed into A1′(x1′, y1′, z1′) using the following formula:

[0083] A1′(x1′,y1′,z1′)=(f(t′x0′),y0′,c′z′0)

[0084] (2) Using a program developed in the modeling software, the fitted parameter curves corresponding to the pitch, skew, and pitch after adjusting according to the requirements of the geometric characteristics of the reconstructed propeller blades are obtained. The pitch value x at the radial position r is obtained. r ′, the value of lateral tilt θ sThe values ​​of pitch β′ and the pitch angle β′ corresponding to the pitch are used to assign pitch, skew, and pitch values ​​to the two-dimensional deformable airfoil at each radial position r of the blade, thereby obtaining the reconstructed airfoil at each radial position r of the blade; the program includes a function to rotate the two-dimensional deformable airfoil about the origin of the three-dimensional coordinate system by the pitch angle β′.

[0085] Specifically, this includes: obtaining the midpoint position of the chord length of the two-dimensional deformable airfoil through a program, and then using a function... The pitch angle β′ of the two-dimensional deformable airfoil is controlled to rotate around the origin of the three-dimensional coordinate system. Then, the pitch, skew and pitch of the two-dimensional deformable airfoil are assigned by the program.

[0086] After assigning values ​​to the pitch, skew, and lead angle, the coordinates of a point on the two-dimensional deformable airfoil are transformed into A2′(x2′, y′2, z′2) using the following formula:

[0087]

[0088] (3) Using a roll-up program developed in the modeling software, the reconstructed airfoil at each radial position r of the blade is rolled up using a cylinder with a bottom radius equal to r to obtain the reconstructed section of the blade at each radial position r.

[0089] The coordinates of points on the reconstructed airfoil after winding are transformed into A′(x′,y′,z′) using the following formula:

[0090]

[0091] Where x′ represents the absolute value of the x-coordinate of point A′; α′ represents the angle between the line connecting A2′ and the origin of the three-dimensional coordinate system and the y-axis;

[0092] (4) In the modeling software, the reconstructed cross sections corresponding to each radial position r of the blade are smoothly joined to complete the surface reconstruction of the blade of the target propeller. Then, multiple reconstructed blades are arranged according to the number of blades of the target propeller to realize the reconstruction of the three-dimensional model of the target propeller.

[0093] The propeller surface reconstruction method described in this invention can modify the three-dimensional model of the propeller by changing its geometric feature parameters, thereby analyzing the relationship between the propeller's geometric features and performance.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for extracting the geometric features of a propeller, characterized in that, Specifically, the following steps are included: S1. Establish a three-dimensional coordinate system xyz in the modeling software, place the three-dimensional model of the target propeller into the three-dimensional coordinate system, and make the propeller shaft and propeller reference line of the three-dimensional model coincide with the x-axis and y-axis of the three-dimensional coordinate system respectively. The coordinates of any point A0 on the blade in the three-dimensional model of the propeller in the three-dimensional coordinate system are (x0, y0, z0). A ring-cutting program, developed in the modeling software, is used to perform ring-cutting on the blade at different radial positions r using a cylinder with a base radius equal to r. The central axis of the cylinder coincides with the propeller shaft of the three-dimensional propeller model. The cross-section obtained after ring-cutting is then unfolded along the propeller reference line in the three-dimensional coordinate system to obtain the airfoil corresponding to the blade at different radial positions r. S2. Develop a pitch-normalization deformation program in the modeling software to perform pitch-normalization deformation on the airfoil sections corresponding to different radial positions r of the blade obtained in S1: (1) The program reads the chord length and position of the airfoil at different radial positions r of the blade, as well as the pitch angle β. (2) The pitch normalization deformation program includes a function that allows the airfoil to rotate about the origin of the three-dimensional coordinate system by a pitch angle β. Based on the length and position of the chord length of the airfoil, the midpoint of the chord length is determined, and then the function is applied. The airfoil is rotated around the origin of the three-dimensional coordinate system by a pitch angle β, and then the pitch x of the airfoil is read through the program. r Lateral tilt θ s and pitch; S3. Using a program developed in the modeling software, the airfoil corresponding to different radial positions r of the blade after pitch unit deformation is uniformly divided into n parts along the thickness direction. The maximum distance between the dividing line and the upper and lower intersection points of the airfoil is taken, and the maximum thickness t and maximum camber c of the airfoil are read by the program. S4. Take the airfoil at any radial position r of the blade, and use a program developed in the modeling software to perform unitized deformation of the airfoil's chord length, thickness, and camber. Specifically, this includes: Based on the chord length, maximum thickness t, and maximum camber c of the airfoil obtained from S2 and S3, the airfoil is scaled in the three-dimensional coordinate system to complete the unitized deformation of the airfoil chord length and thickness. Then, the degree of curvature of the airfoil is controlled by the camber control curve function f(x) included in the program to remove the influence of camber on the airfoil, thereby completing the unitized deformation of the airfoil camber. Finally, the initial airfoil corresponding to the blade in the three-dimensional model of the propeller is obtained, thus completing the extraction of the propeller's geometric features.

2. The propeller geometric feature extraction method according to claim 1, characterized in that, In S1, the coordinates of any point A0 at different radial positions r of the blade become A1(x1, y1, z1) after circumferential cutting and unfolding using the following formula: Where x1 represents the absolute value of the x-coordinate of point A1; α represents the angle between the line connecting point A0 and the origin of the three-dimensional coordinate system and the y-axis.

3. The propeller geometric feature extraction method according to claim 2, characterized in that, In S2, the program reads the pitch x of the airfoil section. r First, the total longitudinal tilt value x of the airfoil section is measured. T Then, the longitudinal tilt x of the airfoil is obtained using the following formula. r : x T =x r +rθ s tanβ。 4. The propeller geometric feature extraction method according to claim 3, characterized in that, In S2, after pitch-normalized deformation, the coordinates of points on the airfoil section are transformed into A2(x2, y2, z2) using the following formula:

5. The propeller geometric feature extraction method according to claim 4, characterized in that, In S4, after normalized deformation of chord length, thickness, and camber, the coordinates of points on the flange section are transformed into A using the following formula: A(x,y,z)=(f(x2) / t,y2,z2 / c).

6. A method for reconstructing a propeller surface, characterized in that, The propeller geometric feature extraction method according to any one of claims 1-5 is adopted, including obtaining the initial airfoil corresponding to the blade of the target propeller using the propeller geometric feature extraction method, and reconstructing the three-dimensional model of the target propeller by using the initial airfoil to reconstruct the blade of the target propeller as needed. The specific steps for reconstructing the propeller blade surface using the initial airfoil, as needed, include: S1' Based on the geometric features of the airfoil at each radial position r of the target propeller blade obtained using the propeller geometric feature extraction method: chord length, pitch x r Lateral tilt θ s For each geometric feature, including pitch, maximum thickness t, and maximum camber c, an original parameter curve representing the radial distribution of the blade geometry of the target propeller is formed. The original parameter curve corresponding to each geometric feature is fitted using F-spline curve fitting to obtain the fitted parameter curve corresponding to each geometric feature. S2' By developing a program in the modeling software, the fitting parameter curves corresponding to the geometric features obtained in S1' are used to parametrically model the blades of the target propeller. The shape of each fitting parameter curve is adjusted according to the requirements of the geometric features of the reconstructed propeller blades, thereby realizing the surface reconstruction of the propeller blades and thus reconstructing the three-dimensional model of the target propeller.

7. The propeller surface reconstruction method according to claim 6, characterized in that, S2' specifically includes: (1) In a three-dimensional coordinate system, a program developed in the modeling software is used to assign values ​​to the chord length, maximum thickness, and maximum camber of the initial airfoil at each radial position r of the blade. The initial airfoil is then fitted with the chord length, maximum thickness, and maximum camber values ​​corresponding to the adjusted chord length, maximum thickness (t′), and maximum camber (c′) at the radial position r. This process yields the two-dimensional deformable airfoil at each radial position r of the blade, specifically including: The program controls the initial airfoil to scale based on the chord length and maximum thickness values ​​to assign the chord length and maximum thickness; and the program uses the camber control curve function f(x) to control the degree of curvature of the initial airfoil based on the maximum camber value to assign the maximum camber. After assigning values ​​to the chord length, maximum thickness, and maximum camber, the coordinates (x0′, y′0, z′0) of any point A0′ on the initial airfoil in the three-dimensional coordinate system are transformed into A1′(x1′, y1′, z1′) using the following formula: A1′(x1′,y1′,z1′)=(f(t′x0′),y0′,c′z′0) (2) Using a program developed in the modeling software, the fitted parameter curves corresponding to the pitch, skew, and pitch after adjusting according to the requirements of the geometric characteristics of the reconstructed propeller blades are obtained. The pitch value x at the radial position r is obtained. r ′, the value of lateral tilt θ s The values ​​of pitch β′ and the pitch angle β′ corresponding to the pitch are used to assign pitch, skew, and pitch values ​​to the two-dimensional deformable airfoil at each radial position r of the blade, thereby obtaining the reconstructed airfoil at each radial position r of the blade; the program includes a function to rotate the two-dimensional deformable airfoil about the origin of the three-dimensional coordinate system by the pitch angle β′. Specifically, this includes: obtaining the midpoint position of the chord length of the two-dimensional deformable airfoil through a program, and then using a function... The pitch angle β′ of the two-dimensional deformable airfoil is controlled to rotate around the origin of the three-dimensional coordinate system. Then, the pitch, skew and pitch of the two-dimensional deformable airfoil are assigned by the program. After assigning values ​​to the pitch, skew, and lead angle, the coordinates of a point on the two-dimensional deformable airfoil are transformed into A2′(x2′, y′2, z′2) using the following formula: (3) Using a roll-up program developed in the modeling software, the reconstructed airfoil at each radial position r of the blade is rolled up using a cylinder with a bottom radius equal to r to obtain the reconstructed section of the blade at each radial position r. The coordinates of points on the reconstructed airfoil after winding are transformed into A′(x′,y′,z′) using the following formula: Where x′ represents the absolute value of the x-coordinate of point A′; α′ represents the angle between the line connecting A2′ and the origin of the three-dimensional coordinate system and the y-axis; (4) In the modeling software, the reconstructed cross sections corresponding to each radial position r of the blade are smoothly joined to complete the surface reconstruction of the blade of the target propeller. Then, multiple reconstructed blades are arranged according to the number of blades of the target propeller to realize the reconstruction of the three-dimensional model of the target propeller.

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