Propeller blade modeling data measuring method

Abstract

The invention relates to the technical field of propeller manufacturing, in particular to a propeller blade modeling data measuring method which comprises the steps of acquiring basic data, performing data unification processing, calculating casting allowance, adding the casting allowance, increasing a reduced scale, measuring the distance between points on a suction surface and a pressure surface and a measurement elevation, and acquiring three-dimensional coordinates of a blade tip and the size of a measurement angle. According to the method, radial parameters and blade section shape values under different section radiuses can be unified through cubic B-spline difference values, measurement can be realized no matter which form a designed data point is given, and the measurement is not affected by a drawing format; through the three B spline difference values, the casting allowance corresponding to each type value point can be obtained under the condition that a small amount of casting allowance corresponding to the blade section type value is provided, so that the setting of the casting allowance is more reasonable and accurate; and the casting allowance is added in the normal direction of the type value point, so that the precision degree of adding the casting allowance can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of propeller manufacturing, and in particular to a method for measuring propeller blade shaping data. Background Art

[0002] Marine propeller blades are complex curved structures with extremely high manufacturing requirements. The traditional propeller blade blank casting process requires confirming the number of blade section radii in the design drawings and determining the number of data points on each radial section on the blade, which is generally 18-22. Use two-dimensional drawing software to mark each data point in the design drawings with the help of horizontal and vertical coordinate values, and connect each data point to obtain the blade section contour diagram. Based on the design data in the drawings, apply casting allowances and scales to the contour diagram; calculate the pitch angle and rotate the blade section contour diagram; move the blade section contour diagram position according to the propeller forward and backward tilt data in the design drawings, and combine the hub relative position data in the drawings to calculate the measurement elevation and the step length of each blade section position, and finally obtain the propeller blade shape measurement data. This traditional method of obtaining propeller blade shape measurement data takes up a lot of time for process designers, and the data is relatively complex, usually accurate to 2-3 decimal places. When the number of data points is large, manual operation and calculation are prone to errors. The rotation angle, forward and backward tilt and longitudinal position are prone to errors, which makes the blade pitch direction prone to errors, resulting in the pitch of the manufactured propeller blade not matching the design drawing. Summary of the invention

[0003] In order to overcome the technical problems of large amount of calculation and poor precision in the prior art of measuring propeller blade shaping data, the present invention provides a method for measuring propeller blade shaping data.

[0004] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: a method for measuring propeller blade shape data, comprising the following steps:

[0005] S1: Obtain the main parameters of the propeller blade designed in the propeller drawing, the propeller section radius, the radial parameters coaxial with the propeller section radius direction, the blade section type value and the casting allowance. The main parameters include the propeller diameter, the section type value arrangement direction, the scale, and the suction surface measurement reference. The radial parameters include the pitch, the longitudinal inclination, the maximum thickness, the chord length, the mid-guide distance, and the distance from the maximum thickness position to the guide edge;

[0006] S2: The propeller section radius, the section chord-wise shape value point position, the radial parameters, and the blade section shape value are fitted by cubic B-spline interpolation, and the radial parameters and blade section shape value at the same section radius and the same section chord-wise shape value point are obtained by the fitted curve;

[0007] S3: Through cubic B-spline interpolation, the cross-section chord-wise type value point positions at the leading edge of the blade, the maximum thickness of the blade, and the blade following edge are fitted with the casting allowances corresponding to the leading edge of the blade, the maximum thickness of the blade, and the blade following edge. The casting allowance size at each type value point on the entire blade cross section is obtained through the fitted curve;

[0008] S4: Calculate the tangent vector at each value point by differential method, calculate the normal vector at each value point on the blade cross section by trigonometric function, and add the casting allowance at each value point obtained in step S2 to the direction of the normal vector at each value point to obtain the contour line of the blade cross section with the casting allowance added;

[0009] S5: Rotate the blade cross-section value point coordinates by pitch angle and perform longitudinal translation through matrix transformation;

[0010] S6: Add a scale to the coordinates of the blade cross-section value point after translation;

[0011] S7: Measure the height of the points on the suction surface and pressure surface from the measuring elevation according to the measurement position line spacing requirements;

[0012] S8: According to the distance from the maximum thickness position to the guide edge at the radius of each propeller section, the height of the pressure surface at the maximum thickness position from the measuring elevation is measured as the height of the pressure surface, and the section radius and its corresponding pressure surface height are fitted by cubic B-spline interpolation. The pressure surface height of the blade tip is obtained through the fitted curve, and the three-dimensional coordinates of the blade tip are obtained through the mid-guide distance. The coordinates are rotated by pitch angle and translated longitudinally and obliquely. The angle between the transformed coordinate point and the center line is the measured angle.

[0013] Preferably, the expression for rotating the blade cross-section value point coordinates by the pitch angle through matrix transformation in step S5 is:

[0014] B=O×A

[0015]

[0016] Among them, B is the point after the pitch angle rotation, A is the point before the pitch angle rotation, x1 and y1 are the X-axis coordinate value and Y-axis coordinate value of the point before rotation, O is the intermediate matrix, and θ is the pitch angle

[0017] The expression of the longitudinal and oblique translation is: y=y2+longitudinal and oblique value, wherein y is the Y-axis coordinate value of the point after the longitudinal and oblique translation, and y2 is the Y-axis coordinate value of the point after the pitch angle rotation.

[0018] Preferably, the measurement position line spacing requirement in step S7 is that, with the center line as a reference, measurement position lines are selected toward the following edge and the leading edge with a step length of 10°. During the selection process, if the width between two adjacent measurement position lines selected with a step length of 10° exceeds 400 mm, then the measurement position lines are continued to be selected toward the following edge and the leading edge with a step length of 5°. If the width between two adjacent measurement position lines selected exceeds 400 mm, then the measurement position lines are continued to be selected toward the following edge and the leading edge with a step length of 5° until the width of a measurement position line closest to the edge point is less than 200 mm from the edge point.

[0019] Preferably, the three-dimensional coordinates of the blade tip are obtained by the mid-range distance, and the three-dimensional coordinates of the blade tip are expressed as:

[0020] (x, y, z) = (-DLL, R, 0);

[0021] Among them, DLL is the intermediate range distance and R is the propeller radius.

[0022] Preferably, the three-dimensional coordinates of the blade tip are obtained through the mid-guide distance, and the coordinates are subjected to pitch angle rotation and longitudinal and oblique translation. The angle between the transformed coordinate point and the center line is the measured angle, where the expression for pitch angle rotation is:

[0023] D=O×C

[0024]

[0025] Among them, B is the point after the pitch angle rotation, A is the point before the pitch angle rotation, x and z are the X-axis coordinate value and Y-axis coordinate value of the point before rotation, O is the intermediate matrix, and θ is the pitch angle

[0026] The expression of the longitudinal and oblique translation is: z2 = z1 + longitudinal and oblique value

[0027] Among them, z2 is the ordinate value of the point after longitudinal and oblique translation, and z1 is the ordinate value of the point after pitch angle rotation;

[0028] The expression of the angle measurement is:

[0029] in To measure the angle, x and y are the coordinate values ​​of the X-axis and Y-axis in the three-dimensional coordinates of the blade tip respectively.

[0030] Compared with the prior art, the present invention has the beneficial effect that, through the cubic B-spline difference, the radial parameters and the blade cross-sectional shape values ​​under different cross-sectional radii can be unified, and measurement can be achieved regardless of the form in which the design data points are given, so that the measurement can be made unaffected by the drawing format; through the cubic B-spline difference, the casting allowance corresponding to each shape value point can be obtained while providing a small amount of casting allowance corresponding to the blade cross-sectional shape value, so that the setting of the casting allowance is more reasonable and accurate, and by setting; by adding the casting allowance in the normal direction of the shape value point, the accuracy of adding the casting allowance can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a top view of the propeller of the present invention.

[0032] Figure 2 It is a schematic cross-sectional view of a propeller blade of the present invention.

[0033] Figure 3 It is a schematic diagram of the blade cross section and casting allowance line of the present invention.

[0034] Figure 4 It is a height schematic diagram of measuring elevations for measuring the distance between points on the suction surface and the pressure surface according to the present invention.

[0035] Figure 5 It is a flow chart of the method of the present invention.

[0036] In the figure: 1: blade; 2: edge point; 3: propeller section radius; 4: width; 5: blade section; 6: guide edge; 7: casting allowance contour line; 8: normal vector at the shape value point; 9: following edge; 10: suction surface; 11: pressure surface; 12: position of the highest point of the blade; 13: measurement elevation; 14: center line; 15: step length 10°; 16: step length 5°; 17: step length 2.5°; 18: measurement height; 19: blade tip; 20: angle measurement. DETAILED DESCRIPTION

[0037] A specific implementation method of a propeller blade shape data measurement method of the present invention is as follows Figures 1 to 5 As shown, a method for measuring propeller blade shape data is characterized by comprising the following steps:

[0038] S1: Obtain the main parameters of the propeller blade 1 designed in the propeller drawing, the propeller section radius 3, the radial parameters coaxial with the propeller section radius direction, the blade section type value and the casting allowance. The main parameters include the propeller diameter, the section type value arrangement direction, the scale, and the suction surface measurement reference. The radial parameters include the pitch, the longitudinal inclination, the maximum thickness, the chord length, the mid-guide distance, and the distance from the maximum thickness position to the guide edge;

[0039] S2: The propeller section radius 3, the section chord-wise shape value point position, the radial parameters, and the blade section shape value are fitted by cubic B-spline interpolation, and the radial parameters and blade section shape value at the same section radius and the same section chord-wise shape value point are obtained by the fitted curve;

[0040] S3: Through cubic B-spline interpolation, the cross-section chord-wise type value point positions at 6 of the blade leading edge, the maximum thickness of the blade, and 9 of the blade trailing edge are fitted with the casting allowances corresponding to 6 of the blade leading edge, the maximum thickness of the blade, and 9 of the blade trailing edge. The casting allowance size at each type value point on the entire blade cross section 5 is obtained through the fitted curve;

[0041] S4: Calculate the tangent vector at each value point by differential method, and calculate the normal vector 8 at each value point on the blade cross section by trigonometric function, and add the casting allowance at each value point obtained in step S2 to the direction of the normal vector 8 at each value point to obtain the contour line 7 of the blade cross section with the casting allowance added;

[0042] S5: Rotate the blade cross-section value point coordinates by pitch angle and perform longitudinal and oblique translation by matrix transformation; the expression for rotating the blade cross-section value point coordinates by pitch angle by matrix transformation in step S5 is:

[0043] B=O×A

[0044]

[0045] Among them, B is the point after the pitch angle rotation, A is the point before the pitch angle rotation, x1 and y1 are the X-axis coordinate value and Y-axis coordinate value of the point before rotation, O is the intermediate matrix, and θ is the pitch angle

[0046] The expression of the longitudinal and oblique translation is: y = y2 + longitudinal and oblique value

[0047] Among them, y is the Y-axis coordinate value of the point after longitudinal and oblique translation, and y2 is the Y-axis coordinate value of the point after pitch angle rotation

[0048] S6: Add a scale to the coordinates of the blade cross-section value point after translation;

[0049] S7: According to the measurement position line interval requirement, measure the heights of points on the suction surface 10 and the pressure surface 11 from the measurement elevation 13, wherein the measurement elevation 13 is higher than the highest point position 12 of the blade;

[0050] The measurement position line interval requirement is that, with the center line 14 as the reference, the measurement position line is selected toward the trailing edge 9 and the guide edge 6 with a step length of 10°15. During the selection process, if the width between two adjacent measurement position lines selected with a step length of 10°15 exceeds 400mm, the measurement position line is selected toward the trailing edge and the guide edge with a step length of 5°16. If the width between two adjacent measurement position lines selected exceeds 400mm, the measurement position line is selected toward the trailing edge 9 and the guide edge 6 with a step length of 5°16 until the measurement position line closest to the edge point 2 is less than 200mm in width 4 from the edge point 2. If the selected measurement position line has two intersections with the trailing edge 9 or the guide edge 6 at the same time, the measurement position line is discarded. ;

[0051] The three-dimensional coordinates of the blade tip 19 are obtained by the mid-range distance, and the three-dimensional coordinates of the blade tip 19 are expressed as:

[0052] (x, y, z) = (-DLL, R, 0);

[0053] Among them, DLL is the mid-range distance, and R is the propeller radius;

[0054] The three-dimensional coordinates of the blade tip 19 are obtained by the mid-guide distance, and the coordinates are subjected to pitch angle rotation and longitudinal and oblique translation. The angle between the coordinate point and the center line after the transformation is the measured angle size, where the expression for pitch angle rotation is:

[0055] D=O×C

[0056]

[0057] Among them, B is the point after the pitch angle rotation, A is the point before the pitch angle rotation, x and z are the X-axis coordinate value and Y-axis coordinate value of the point before rotation, O is the intermediate matrix, and θ is the pitch angle

[0058] The expression of longitudinal and oblique translation is: z2 = z1 + longitudinal and oblique value

[0059] Among them, z2 is the ordinate value of the point after longitudinal and oblique translation, and z1 is the ordinate value of the point after pitch angle rotation.

[0060] The expression of the angle measurement is:

[0061] in For angle measurement, x and y are the coordinate values ​​of the X axis and Y axis in the three-dimensional coordinates of the blade tip 19, respectively;

[0062] S8: According to the distance from the maximum thickness position at the radius 3 of each propeller section to the guide edge 6, the height of the pressure surface at the maximum thickness position from the measured elevation is measured as the height of the pressure surface, and the section radius and its corresponding pressure surface height are fitted by cubic B-spline interpolation. The pressure surface height of the blade tip 19 is obtained through the fitted curve, and the three-dimensional coordinates of the blade tip 19 are obtained through the mid-guide distance. The coordinates are rotated by pitch angle and translated longitudinally and obliquely. The angle between the transformed coordinate point and the center line is the measured angle 20.

[0063] The present invention is described by way of embodiments, and those skilled in the art will appreciate that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the protection scope of the present invention.

Claims

1. A method for measuring propeller blade shape data, characterized in that: The following steps are involved: S1: Obtain the main parameters of the propeller blade (1) designed in the propeller drawing, the propeller section radius (3), the radial parameters coaxial with the propeller section radius direction, the blade section shape value and the casting allowance. The main parameters include the propeller diameter, the section shape value arrangement direction, the scale, and the suction surface measurement reference. The radial parameters include the pitch, the longitudinal inclination, the maximum thickness, the chord length, the mid-guide distance, and the distance from the maximum thickness position to the guide edge; S2: The propeller section radius (3), the section chord-wise shape value point position, the radial parameters, and the blade section shape value are fitted by cubic B-spline interpolation, and the radial parameters and blade section shape value at the same section radius and the same section chord-wise shape value point are obtained by the fitted curve; S3: By using cubic B-spline interpolation, the cross-section chord-wise type value point positions at the leading edge (6) of the blade, the maximum thickness of the blade, and the blade trailing edge (9) are fitted with the casting allowances corresponding to the leading edge (6), the maximum thickness of the blade, and the blade trailing edge (9) of the blade, and the casting allowance size at each type value point on the entire blade cross section is obtained through the fitted curve; S4: Calculate the tangent vector at each value point by differential method, and calculate the normal vector (8) at each value point on the blade cross section by trigonometric function, and add the casting allowance at each value point obtained in step S2 to the direction of the normal vector (8) at each value point to obtain the contour line (7) of the blade cross section with the casting allowance added; S5: Rotate the blade cross-section value point coordinates by pitch angle and perform longitudinal translation through matrix transformation; S6: Add a scale to the coordinates of the blade cross-section value point after translation; S7: According to the measurement position line spacing requirement, measuring the height of the points on the suction surface (10) and the pressure surface (11) from the measurement elevation; S8: According to the distance from the maximum thickness position to the guide edge (6) at the radius of each propeller section (3), the height of the pressure surface at the maximum thickness position from the measuring elevation is measured as the height of the pressure surface, and the section radius and its corresponding pressure surface height are fitted by cubic B-spline interpolation. The pressure surface height of the blade tip (19) is obtained through the fitted curve, and the three-dimensional coordinates of the blade tip (19) are obtained through the mid-guide distance. The coordinates are rotated by pitch angle and translated longitudinally and obliquely. The angle between the transformed coordinate point and the center line is the measured angle (20).

2. A propeller blade shape data measurement method according to claim 1, characterized in that: The expression for rotating the blade cross-section value point coordinates by pitch angle through matrix transformation in step S5 is: B=O×A Among them, B is the point after the pitch angle rotation, A is the point before the pitch angle rotation, x1 and y1 are the X-axis coordinate value and Y-axis coordinate value of the point before rotation, O is the intermediate matrix, and θ is the pitch angle; The expression of the longitudinal and oblique translation is: y = y2 + longitudinal and oblique value Among them, y is the Y-axis coordinate value of the point after longitudinal and oblique translation, and y2 is the Y-axis coordinate value of the point after pitch angle rotation.

3. A propeller blade shape data measurement method according to claim 1, characterized in that: The measurement position line spacing requirement in step S7 is that, with the center line (14) as a reference, measurement position lines are selected toward the trailing edge (9) and the leading edge (6) with a step length of 10° (15). During the selection process, if the width between two adjacent measurement position lines selected with a step length of 10° (15) exceeds 400 mm, the measurement position lines are selected toward the trailing edge and the leading edge with a step length of 5° (16). If the width between two adjacent measurement position lines selected exceeds 400 mm, the measurement position lines are selected toward the trailing edge (9) and the leading edge (6) with a step length of 5° (16) until the width (4) of a measurement position line closest to the edge point (2) is less than 200 mm from the edge point (2).

4. A propeller blade shape data measurement method according to claim 1, characterized in that: The three-dimensional coordinates of the blade tip (19) are obtained by the mid-range distance. The three-dimensional coordinates of the blade tip (19) are expressed as: (x, y, z) = (-DLL, R, 0); Among them, DLL is the intermediate range distance and R is the propeller radius.

5. A propeller blade shape data measurement method according to claim 4, characterized in that: The three-dimensional coordinates of the blade tip (25) are obtained by the mid-guide distance, and the coordinates are subjected to pitch angle rotation and longitudinal and oblique translation. The angle between the coordinate point and the center line after the transformation is the measured angle size, where the expression for pitch angle rotation is: D=O×C Among them, B is the point after the pitch angle rotation, A is the point before the pitch angle rotation, x and z are the X-axis coordinate value and Y-axis coordinate value of the point before rotation, O is the intermediate matrix, and θ is the pitch angle The expression of the longitudinal and oblique translation is: z2 = z1 + longitudinal and oblique value Among them, z2 is the ordinate value of the point after longitudinal and oblique translation, and z1 is the ordinate value of the point after pitch angle rotation. The expression of the angle measurement is: in For angle measurement, x and y are the coordinate values ​​of the X axis and the Y axis in the three-dimensional coordinates of the blade tip (25), respectively.

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