CN113393428A - Method for detecting shape of air inlet and outlet edges of aero-engine blade - Google Patents

Method for detecting shape of air inlet and outlet edges of aero-engine blade Download PDF

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CN113393428A
CN113393428A CN202110600366.2A CN202110600366A CN113393428A CN 113393428 A CN113393428 A CN 113393428A CN 202110600366 A CN202110600366 A CN 202110600366A CN 113393428 A CN113393428 A CN 113393428A
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theoretical
blade
edge
vertex
shape
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CN113393428B (en
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李大力
陈雷
张旭
王婧雯
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HUST Wuxi Research Institute
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/0002—Inspection of images, e.g. flaw detection
    • G06T7/0004—Industrial image inspection
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/10—Segmentation; Edge detection
    • G06T7/12—Edge-based segmentation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/10—Segmentation; Edge detection
    • G06T7/13—Edge detection
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/10—Segmentation; Edge detection
    • G06T7/136—Segmentation; Edge detection involving thresholding
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/10—Image acquisition modality
    • G06T2207/10028—Range image; Depth image; 3D point clouds
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/30—Subject of image; Context of image processing
    • G06T2207/30108—Industrial image inspection
    • G06T2207/30164—Workpiece; Machine component
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation

Abstract

The invention relates to the technical field of aero-engine blade detection, and particularly discloses a method for detecting shapes of air inlet and exhaust edges of an aero-engine blade, wherein the method comprises the following steps: acquiring theoretical point cloud data of the blade profile of the blade, actual measurement point cloud data of the blade profile and a deviation value; performing curve fitting according to the theoretical point cloud data of the blade profile to obtain a theoretical blade profile curve and a theoretical blade profile pitch arc, and performing curve fitting according to the actually measured point cloud data of the blade profile to obtain an actually measured blade profile curve and an actually measured blade profile pitch arc; calculating according to the theoretical blade profile curve and the theoretical mean camber line to obtain a leading edge theoretical peak and a trailing edge theoretical peak; calculating according to the actually measured blade profile curve and the actually measured camber line to obtain an actually measured vertex of the front edge and an actually measured vertex of the rear edge; calculating the curvature radius of the actually measured vertex of the front edge and the curvature radius of the actually measured vertex of the rear edge; and comparing and judging the shape of the front edge and the shape of the rear edge of the blade. The method for detecting the shape of the air inlet and outlet edges of the aero-engine blade improves the defect detection efficiency of the blade.

Description

Method for detecting shape of air inlet and outlet edges of aero-engine blade
Technical Field
The invention relates to the technical field of aero-engine blade detection, in particular to a method for detecting shapes of air inlet and exhaust edges of an aero-engine blade.
Background
The shape of the inlet and exhaust edges (leading edge and trailing edge) of a blade, which is one of the important parts of an aircraft engine, has a great influence on the aerodynamic performance of the engine. The shape of the front/rear edge of the blade is generally designed to be an arc or an elliptic arc, and in the actual production process, the front/rear edge of the blade is often caused to be in a non-ideal arc shape due to the influence of a processing technology. Definition of "leading/trailing edge arc shape control" is specified in standard HB 5647-1998 "labeling, tolerance and blade surface roughness for blade profiles", page 21, item 6.6. The shape of the leading/trailing edge, the smoothness of the transition of the leading/trailing edge arc with the blade basin and the blade back profile line and the smoothness of the change of the leading/trailing edge arc in the blade span direction need to be controlled. Among these, four cases (chamfered, sharp, necked, flat) in which the leading/trailing edge transition is likely to occur are not allowed.
The existing special evaluation software for blade parameters can only evaluate the parameters of the thickness of the front/rear edge of the blade, the radius of an arc, the points of the front/rear edge, the chord length, the torsion angle, the profile degree and the like, but can not effectively identify the non-ideal arc shape of the front/rear edge. The evaluation of the edge shape of the front exhaust and the rear exhaust mainly depends on manual work, and a detector compares the front/rear edge outline enlarged image with a front/rear edge unqualified process shape standard pattern to visually obtain an evaluation conclusion. The detection method has the defects of nonstandard image magnification, strong subjectivity of judgment results and the like, and is easy to cause the problem of inconsistent detection results of different personnel; meanwhile, as the blades are produced in batches and the number of the detection sections is large, the manual judgment workload is large, the time consumption is long, and the comprehensive evaluation efficiency of the blade quality is seriously influenced.
Therefore, how to provide a detection method capable of improving the efficiency of blade production and quality inspection becomes an urgent technical problem to be solved by those skilled in the art.
Disclosure of Invention
The invention provides a method for detecting the shape of an air inlet and outlet edge of an aircraft engine blade, which solves the problem of low blade detection efficiency in the related technology.
As one aspect of the present invention, there is provided a method for detecting shapes of inlet and outlet edges of an aircraft engine blade, comprising:
acquiring blade profile contour theoretical point cloud data of a blade, blade profile contour actual measurement point cloud data of the blade and a deviation value between the blade profile contour theoretical point cloud data and the blade profile contour actual measurement point cloud data, wherein the blade profile contour theoretical point cloud data and the blade profile contour actual measurement point cloud data respectively comprise point cloud data corresponding to a blade basin, a blade back, a front edge and a rear edge;
performing curve fitting according to the theoretical point cloud data of the blade profile to obtain a theoretical blade profile curve and a theoretical blade profile pitch arc, and performing curve fitting according to the actually measured point cloud data of the blade profile to obtain an actually measured blade profile curve and an actually measured blade profile pitch arc;
calculating according to the theoretical blade profile curve and the theoretical mean camber line to obtain a leading edge theoretical peak and a trailing edge theoretical peak; calculating according to the actually measured blade profile curve and the actually measured mean camber line to obtain an actually measured vertex of the front edge and an actually measured vertex of the rear edge;
respectively calculating a leading edge theoretical vertex curvature radius and a trailing edge theoretical vertex curvature radius according to the leading edge theoretical vertex and the trailing edge theoretical vertex, and respectively calculating a leading edge actual measurement vertex curvature radius and a trailing edge actual measurement vertex curvature radius according to the leading edge actual measurement vertex and the trailing edge actual measurement vertex;
and judging the shape of the front edge and the shape of the rear edge of the blade according to the comparison of the front edge theoretical vertex curvature radius and the rear edge theoretical vertex curvature radius with the front edge actual measurement vertex curvature radius and the rear edge actual measurement vertex curvature radius.
Further, the performing curve fitting according to the theoretical point cloud data of the leaf profile to obtain a theoretical leaf profile curve and a theoretical mean camber line, and performing curve fitting according to the actually measured point cloud data of the leaf profile to obtain an actually measured leaf profile curve and an actually measured mean camber line includes:
performing curve fitting on the theoretical point cloud data of the leaf profile according to a least square method and a NURBS method to obtain a theoretical leaf profile curve and a theoretical mean camber line;
and performing curve fitting on the actually measured point cloud data of the leaf profile according to a least square method and a NURBS method to obtain an actually measured leaf profile curve and an actually measured mean camber line.
Further, the curve fitting is performed on the theoretical point cloud data of the blade profile according to a least square method and a NURBS method to obtain a theoretical blade profile curve and a theoretical blade profile mean camber line, and the method comprises the following steps:
respectively carrying out circle fitting or ellipse fitting on the leading edge point cloud data and the trailing edge point cloud data in the leaf profile theoretical point cloud data according to a least square method to obtain a fitted leading edge theoretical circle center coordinate and a fitted trailing edge theoretical circle center coordinate;
respectively performing curve fitting on the leaf basin point cloud data and the leaf back point cloud data in the leaf profile theoretical point cloud data according to a NURBS method;
calculating the theoretical point cloud data of the leaf profile according to an inscribed circle method to obtain a theoretical inscribed circle center point;
and carrying out NURBS curve fitting according to the theoretical center coordinates of the front edge, the theoretical center coordinates of the rear edge and the theoretical center point of the inscribed circle to obtain a theoretical blade profile camber line.
Further, the calculating according to the theoretical blade profile curve and the theoretical mean camber line to obtain a leading edge theoretical vertex and a trailing edge theoretical vertex includes:
calculating the intersection point of a theoretical front edge circular arc or a front edge elliptic arc and the theoretical mean camber line to obtain a front edge theoretical vertex;
and calculating the intersection point of the theoretical trailing edge circular arc or the trailing edge elliptic arc and the theoretical mean camber line to obtain the theoretical vertex of the trailing edge.
Further, the calculating the leading edge theoretical vertex curvature radius and the trailing edge theoretical vertex curvature radius according to the leading edge theoretical vertex and the trailing edge theoretical vertex respectively includes:
calculating the curvature radius value of the theoretical vertex of the front edge according to an arc curvature radius calculation formula or an elliptic arc curvature radius calculation formula and the theoretical front edge arc or the front edge elliptic arc;
and calculating the curvature radius value of the theoretical vertex of the trailing edge according to an arc curvature radius calculation formula or an elliptic arc curvature radius calculation formula and the theoretical trailing edge arc or the trailing edge elliptic arc.
Further, performing curve fitting on the actually measured point cloud data of the leaf profile according to a least square method and a NURBS method to obtain an actually measured leaf profile curve and an actually measured mean camber line, including:
respectively carrying out circle fitting or ellipse fitting on the leading edge point cloud data and the trailing edge point cloud data in the measured point cloud data of the blade profile outline according to a least square method to obtain fitted leading edge measured circle center coordinates and trailing edge measured circle center coordinates;
respectively performing curve fitting on the leaf basin point cloud data and the leaf back point cloud data in the actually measured point cloud data of the leaf profile according to a NURBS method;
calculating the actually measured point cloud data of the leaf profile according to an inscribed circle method to obtain an actually measured inscribed circle center point;
and carrying out NURBS curve fitting according to the measured center coordinates of the front edge, the measured center coordinates of the rear edge and the measured inscribed circle center point to obtain the measured blade profile camber line.
Further, the calculating according to the measured blade profile curve and the measured mean camber line to obtain a measured vertex of the leading edge and a measured vertex of the trailing edge includes:
carrying out NURBS curve fitting on the actual measurement points of the front edge of the blade and the actual measurement points of the rear edge of the blade respectively to obtain an actual curve of the front edge of the blade and an actual curve of the rear edge of the blade;
and calculating the intersection point of the actual curve of the blade leading edge and the camber line of the actual blade profile to obtain an actual vertex of the leading edge, and calculating the intersection point of the actual curve of the blade trailing edge and the camber line of the actual blade profile to obtain an actual vertex of the trailing edge.
Further, the calculating the curvature radius of the actually measured vertex of the leading edge and the curvature radius of the actually measured vertex of the trailing edge according to the actually measured vertex of the leading edge and the actually measured vertex of the trailing edge respectively includes:
respectively calculating a curvature radius model of the actual curve of the front edge of the blade and a curve radius model of the actual curve of the rear edge of the blade;
and calculating the curvature radius value of the actual vertex of the front edge according to the curvature radius model of the actual curve of the front edge of the blade, and calculating the curvature radius value of the actual vertex of the rear edge according to the curve radius model of the actual curve of the rear edge of the blade.
Further, the determining the leading edge shape and the trailing edge shape of the blade according to the comparison of the leading edge theoretical vertex curvature radius and the trailing edge theoretical vertex curvature radius with the leading edge actual measurement vertex curvature radius and the trailing edge actual measurement vertex curvature radius includes:
calculating the ratio of the theoretical vertex curvature radius of the front edge to the actual vertex curvature radius of the front edge to obtain the ratio of the curvature radii of the front edge;
calculating the ratio of the theoretical vertex curvature radius of the trailing edge to the actual vertex curvature radius of the trailing edge to obtain the ratio of the curvature radii of the trailing edge;
and respectively comparing the ratio of the curvature radius of the front edge and the ratio of the curvature radius of the rear edge with a preset theoretical range, and judging the shape of the front edge and the shape of the rear edge of the blade according to the comparison result.
Further, the comparing the ratio of the curvature radius of the leading edge and the ratio of the curvature radius of the trailing edge with a preset theoretical range respectively, and determining the shape of the leading edge and the shape of the trailing edge of the blade according to the comparison result includes:
when the ratio of the curvature radius of the front edge is smaller than the lower limit value of the preset theoretical range, the shape of the front edge of the blade is judged to be a pointed shape, and when the ratio of the curvature radius of the rear edge is smaller than the lower limit value of the preset theoretical range, the shape of the rear edge of the blade is judged to be a pointed shape;
when the ratio of the curvature radius of the front edge is not smaller than the lower limit value of the preset theoretical range, if the minimum value of the curvature radius appears on both sides of the front edge of the blade and the ratio of the curvature radius of the front edge is larger than the upper limit value of the preset theoretical range, the shape of the front edge of the blade is determined to be a blunt shape; when the ratio of the curvature radius of the trailing edge is not less than the lower limit value of the preset theoretical range, if the minimum value of the curvature radius appears on both sides of the trailing edge of the blade and the ratio of the curvature radius of the trailing edge is greater than the upper limit value of the preset theoretical range, the shape of the trailing edge of the blade is determined to be a blunt shape;
when the shape of the front edge of the blade is judged to be a pointed shape or a blunt shape, calculating a front edge blade profile intersection point between an actual curve of the front edge of the blade and the theoretical blade profile curve, and when the shape of the rear edge of the blade is judged to be a pointed shape or a blunt shape, calculating a rear edge blade profile intersection point between an actual curve of the rear edge of the blade and the theoretical blade profile curve;
judging whether the leading edge shape of the blade has any one or more of a skewed shape feature, a necking shape feature and a size/size shape feature according to the change trend of the leading edge blade profile intersection point; and judging whether the trailing edge shape of the blade has any one or more of a crooked head shape characteristic, a necking shape characteristic and a size/size shape characteristic according to the change trend of the trailing edge blade profile intersection point.
The invention provides a method for detecting the shape of the air inlet and outlet edges of an aircraft engine blade, which comprises the steps of firstly obtaining theoretical point clouds of the blade, measuring point clouds and deviation values of corresponding points, fitting a blade profile curve and a mean camber line, calculating the vertex of the front edge/the back edge, establishing a curvature radius model of the front edge and the back edge, calculating the curvature radius of the vertex of the front edge/the back edge, finally evaluating the shape of the front edge/the back edge of the blade according to the curvature characteristics and the deviation value change characteristics of the front edge/the back edge of the blade in different shapes, the method for detecting the shape of the air inlet and exhaust edge of the aero-engine blade can combine the curvature characteristic of the front edge/the rear edge with the deviation value change characteristic, the characteristic value is visual, the shape of the air inlet and exhaust edge of the blade can be automatically interpreted, the influence of artificial subjective factors is eliminated, and compared with a method for manually and visually detecting the shape of the air inlet and exhaust edge, the method for detecting the shape of the air inlet and exhaust edge of the aero-engine blade has higher detection efficiency and consistency.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a flow chart of a method for detecting the shape of an inlet and outlet edge of an aircraft engine blade according to the present invention.
Fig. 2 is a schematic structural diagram of the shape of the blade provided by the invention.
FIG. 3 is a flowchart of an embodiment of a method for detecting the shape of the inlet and outlet edges of an aircraft engine blade according to the present invention.
Fig. 4a is a schematic view of the shape of the tip provided by the present invention.
Fig. 4b is a schematic view of the blunt tip shape provided by the present invention.
Fig. 4c is a schematic view of a head-tilted shape according to the present invention.
FIG. 4d is a schematic view of the shape of the constriction provided by the present invention.
Fig. 4e is a schematic diagram of the size/shape provided by the present invention.
Fig. 5 is a schematic diagram of an example of interpreting the shape of the tip provided by the present invention.
Fig. 6 is a schematic diagram of an exemplary interpretation of the blunt tip shape provided by the present invention.
Fig. 7 is a schematic diagram of an exemplary skew head shape interpretation provided by the present invention.
FIG. 8 is a schematic view of an exemplary interpretation of the shape of a neck provided by the present invention.
Fig. 9 is a schematic diagram of an example interpretation of the size/shape provided by the present invention.
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged under appropriate circumstances in order to facilitate the description of the embodiments of the invention herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
In the present embodiment, a method for detecting an inlet and outlet edge shape of an aircraft engine blade is provided, and fig. 1 is a flowchart of a method for detecting an inlet and outlet edge shape of an aircraft engine blade according to an embodiment of the present invention, as shown in fig. 1, including:
s110, acquiring blade profile contour theoretical point cloud data of a blade, blade profile contour actual measurement point cloud data of the blade and a deviation value between the blade profile contour theoretical point cloud data and the blade profile contour actual measurement point cloud data, wherein the blade profile contour theoretical point cloud data and the blade profile contour actual measurement point cloud data respectively comprise point cloud data corresponding to a blade basin, a blade back, a front edge and a rear edge;
in the embodiment of the invention, the theoretical point cloud data of the blade profile of the blade, the actually measured point cloud data of the blade profile of the blade and the deviation value between the theoretical point cloud data of the blade profile and the actually measured point cloud data of the blade profile can be obtained through a measurement file of a coordinate measuring machine, the measurement file can be generated through the measurement of the coordinate measuring machine in the production process of the blade, and the data can be obtained only by obtaining the measurement file.
It should be noted that, as shown in fig. 2, the shape and structure of the blade are schematically illustrated, the blade is divided into four parts, namely a blade basin, a blade back, a leading edge and a trailing edge, and specifically, the blade may be divided into a leading edge arc 100, a trailing edge arc 200, a blade basin profile 300, a blade back profile 400, a leading edge tangent point 500 and a trailing edge tangent point 600. Therefore, the acquired point cloud data is also correspondingly divided into point cloud data of a leaf basin, point cloud data of a leaf back, point cloud data of a leading edge and point cloud data of a trailing edge, and the point cloud data of the leaf basin, the point cloud data of the leaf back, the point cloud data of the leading edge and the point cloud data of the trailing edge are included in both the leaf profile contour theoretical point cloud data of the leaf and the leaf profile contour actual measurement point cloud data of the leaf.
S120, performing curve fitting according to the theoretical point cloud data of the blade profile contour to obtain a theoretical blade profile curve and a theoretical blade profile mean camber line, and performing curve fitting according to the actually measured point cloud data of the blade profile contour to obtain an actually measured blade profile curve and an actually measured blade profile mean camber line;
in the embodiment of the invention, curve fitting is respectively carried out on the theoretical point cloud data of the leaf profile and the actually measured point cloud data of the leaf profile to obtain a corresponding theoretical leaf profile curve and a theoretical leaf profile mean camber line as well as an actually measured leaf profile curve and an actually measured leaf profile mean camber line.
S130, calculating according to the theoretical blade profile curve and the theoretical mean camber line to obtain a leading edge theoretical peak and a trailing edge theoretical peak; calculating according to the actually measured blade profile curve and the actually measured mean camber line to obtain an actually measured vertex of the front edge and an actually measured vertex of the rear edge;
in the embodiment of the present invention, the theoretical vertex of the leading edge/the theoretical trailing edge and the measured vertex of the leading edge/the measured trailing edge are calculated according to the theoretical blade profile curve and the theoretical mean camber line and the measured blade profile curve and the measured camber line obtained by fitting as described above, respectively.
S140, respectively calculating a leading edge theoretical vertex curvature radius and a trailing edge theoretical vertex curvature radius according to the leading edge theoretical vertex and the trailing edge theoretical vertex, and respectively calculating a leading edge actual measurement vertex curvature radius and a trailing edge actual measurement vertex curvature radius according to the leading edge actual measurement vertex and the trailing edge actual measurement vertex;
in the embodiment of the invention, the curvature radius of the theoretical vertex of the front edge/the rear edge is calculated through the theoretical vertex of the front edge/the rear edge, and the curvature radius of the measured vertex of the front edge/the rear edge is calculated through the measured vertex of the front edge/the rear edge.
S150, judging the shape of the front edge and the shape of the rear edge of the blade according to the comparison between the front edge theoretical vertex curvature radius and the rear edge theoretical vertex curvature radius and the front edge actual measurement vertex curvature radius and the rear edge actual measurement vertex curvature radius.
In an embodiment of the present invention, the leading edge shape and trailing edge shape are analyzed based on the comparison of the leading/trailing edge theoretical apex radius of curvature and the leading/trailing edge measured apex radius of curvature described above.
The method for detecting the shape of the air inlet and outlet edges of the blade of the aero-engine, provided by the embodiment of the invention, comprises the steps of firstly obtaining theoretical point clouds of the blade, measuring point clouds and deviation values of corresponding points, fitting a blade profile curve and a mean camber line, calculating the vertex of the front edge/the back edge, establishing a curvature radius model of the front edge and the back edge, calculating the curvature radius of the vertex of the front edge/the back edge, finally evaluating the shape of the front edge/the back edge of the blade according to the curvature characteristics and the deviation value change characteristics of the front edge/the back edge of the blade in different shapes, the method for detecting the shape of the air inlet and exhaust edge of the aero-engine blade can combine the curvature characteristic of the front edge/the rear edge with the deviation value change characteristic, the characteristic value is visual, the shape of the air inlet and exhaust edge of the blade can be automatically interpreted, the influence of artificial subjective factors is eliminated, and compared with a method for manually and visually detecting the shape of the air inlet and exhaust edge, the method for detecting the shape of the air inlet and exhaust edge of the aero-engine blade has higher detection efficiency and consistency.
As a specific implementation manner, as shown in fig. 3, the performing curve fitting according to the theoretical point cloud data of the leaf profile to obtain a theoretical leaf profile curve and a theoretical mean camber line, and performing curve fitting according to the actually measured point cloud data of the leaf profile to obtain an actually measured leaf profile curve and an actually measured mean camber line includes:
s121, performing curve fitting on the theoretical point cloud data of the leaf profile according to a least square method and a NURBS method to obtain a theoretical leaf profile curve and a theoretical mean camber line;
further specifically, performing circle fitting or ellipse fitting on the leading edge point cloud data and the trailing edge point cloud data in the theoretical point cloud data of the blade profile according to a least square method to obtain a fitted leading edge theoretical circle center coordinate and a fitted trailing edge theoretical circle center coordinate;
respectively performing curve fitting on the leaf basin point cloud data and the leaf back point cloud data in the leaf profile theoretical point cloud data according to a NURBS method;
calculating the theoretical point cloud data of the leaf profile according to an inscribed circle method to obtain a theoretical inscribed circle center point;
and carrying out NURBS curve fitting according to the theoretical center coordinates of the front edge, the theoretical center coordinates of the rear edge and the theoretical center point of the inscribed circle to obtain a theoretical blade profile camber line.
Further specifically, the calculating according to the theoretical blade profile curve and the theoretical mean camber line to obtain a leading edge theoretical vertex and a trailing edge theoretical vertex includes:
calculating the intersection point of a theoretical front edge circular arc or a front edge elliptic arc and the theoretical mean camber line to obtain a front edge theoretical vertex;
and calculating the intersection point of the theoretical trailing edge circular arc or the trailing edge elliptic arc and the theoretical mean camber line to obtain the theoretical vertex of the trailing edge.
Further specifically, the calculating the leading edge theoretical vertex curvature radius and the trailing edge theoretical vertex curvature radius according to the leading edge theoretical vertex and the trailing edge theoretical vertex respectively includes:
calculating the curvature radius value of the theoretical vertex of the front edge according to an arc curvature radius calculation formula or an elliptic arc curvature radius calculation formula and the theoretical front edge arc or the front edge elliptic arc;
and calculating the curvature radius value of the theoretical vertex of the trailing edge according to an arc curvature radius calculation formula or an elliptic arc curvature radius calculation formula and the theoretical trailing edge arc or the trailing edge elliptic arc.
And S122, performing curve fitting on the actually measured point cloud data of the leaf profile according to a least square method and a NURBS method to obtain an actually measured leaf profile curve and an actually measured middle arc.
Further specifically, performing circle fitting or ellipse fitting on the leading edge point cloud data and the trailing edge point cloud data in the measured point cloud data of the blade profile according to a least square method to obtain fitted leading edge measured circle center coordinates and trailing edge measured circle center coordinates;
respectively performing curve fitting on the leaf basin point cloud data and the leaf back point cloud data in the actually measured point cloud data of the leaf profile according to a NURBS method;
calculating the actually measured point cloud data of the leaf profile according to an inscribed circle method to obtain an actually measured inscribed circle center point;
and carrying out NURBS curve fitting according to the measured center coordinates of the front edge, the measured center coordinates of the rear edge and the measured inscribed circle center point to obtain the measured blade profile camber line.
Further specifically, the calculating according to the measured blade profile curve and the measured mean camber line to obtain a measured vertex of the leading edge and a measured vertex of the trailing edge includes:
carrying out NURBS curve fitting on the actual measurement points of the front edge of the blade and the actual measurement points of the rear edge of the blade respectively to obtain an actual curve of the front edge of the blade and an actual curve of the rear edge of the blade;
and calculating the intersection point of the actual curve of the blade leading edge and the camber line of the actual blade profile to obtain an actual vertex of the leading edge, and calculating the intersection point of the actual curve of the blade trailing edge and the camber line of the actual blade profile to obtain an actual vertex of the trailing edge.
Further specifically, the calculating the curvature radius of the actually measured vertex of the leading edge and the curvature radius of the actually measured vertex of the trailing edge according to the actually measured vertex of the leading edge and the actually measured vertex of the trailing edge respectively includes:
respectively calculating a curvature radius model of the actual curve of the front edge of the blade and a curve radius model of the actual curve of the rear edge of the blade;
and calculating the curvature radius value of the actual vertex of the front edge according to the curvature radius model of the actual curve of the front edge of the blade, and calculating the curvature radius value of the actual vertex of the rear edge according to the curve radius model of the actual curve of the rear edge of the blade.
In an embodiment of the present invention, the determining the leading edge shape and the trailing edge shape of the blade according to the comparison between the leading edge theoretical vertex curvature radius and the trailing edge theoretical vertex curvature radius and the leading edge actual measurement vertex curvature radius and the trailing edge actual measurement vertex curvature radius includes:
calculating the ratio of the theoretical vertex curvature radius of the front edge to the actual vertex curvature radius of the front edge to obtain the ratio of the curvature radii of the front edge;
calculating the ratio of the theoretical vertex curvature radius of the trailing edge to the actual vertex curvature radius of the trailing edge to obtain the ratio of the curvature radii of the trailing edge;
and respectively comparing the ratio of the curvature radius of the front edge and the ratio of the curvature radius of the rear edge with a preset theoretical range, and judging the shape of the front edge and the shape of the rear edge of the blade according to the comparison result.
Further specifically, the comparing the ratio of the leading edge curvature radius and the ratio of the trailing edge curvature radius with a preset theoretical range respectively, and determining the leading edge shape and the trailing edge shape of the blade according to the comparison result includes:
when the ratio of the curvature radius of the front edge is smaller than the lower limit value of the preset theoretical range, the shape of the front edge of the blade is judged to be a pointed shape, and when the ratio of the curvature radius of the rear edge is smaller than the lower limit value of the preset theoretical range, the shape of the rear edge of the blade is judged to be a pointed shape;
when the ratio of the curvature radius of the front edge is not smaller than the lower limit value of the preset theoretical range, if the minimum value of the curvature radius appears on both sides of the front edge of the blade and the ratio of the curvature radius of the front edge is larger than the upper limit value of the preset theoretical range, the shape of the front edge of the blade is determined to be a blunt shape; when the ratio of the curvature radius of the trailing edge is not less than the lower limit value of the preset theoretical range, if the minimum value of the curvature radius appears on both sides of the trailing edge of the blade and the ratio of the curvature radius of the trailing edge is greater than the upper limit value of the preset theoretical range, the shape of the trailing edge of the blade is determined to be a blunt shape;
when the shape of the front edge of the blade is judged to be a pointed shape or a blunt shape, calculating a front edge blade profile intersection point between an actual curve of the front edge of the blade and the theoretical blade profile curve, and when the shape of the rear edge of the blade is judged to be a pointed shape or a blunt shape, calculating a rear edge blade profile intersection point between an actual curve of the rear edge of the blade and the theoretical blade profile curve;
judging whether the leading edge shape of the blade has any one or more of a skewed shape feature, a necking shape feature and a size/size shape feature according to the change trend of the leading edge blade profile intersection point; and judging whether the trailing edge shape of the blade has any one or more of a crooked head shape characteristic, a necking shape characteristic and a size/size shape characteristic according to the change trend of the trailing edge blade profile intersection point.
As shown in fig. 4a to 4e, the various shapes of the blade are schematically illustrated, fig. 4a shows a pointed shape, fig. 4b shows a blunt shape, fig. 4c shows a skewed shape, fig. 4d shows a constricted shape, and fig. 4e shows a size/size shape.
The following describes in detail a specific implementation process of the method for detecting the shape of the inlet and outlet edges of the aircraft engine blade according to the embodiment of the present invention with reference to fig. 3 to 9.
Step 1, for a certain aero-engine blade, theoretical point cloud data of a blade profile (namely a blade body section line), actual measurement data of corresponding points and deviation values are obtained, and the point cloud data is divided into four areas, namely a front edge, a rear edge, a blade basin and a blade back.
And 2, respectively reading theoretical point cloud and actually measured point cloud data of the blade profile, and performing (elliptical) circle fitting on the point cloud of the front edge and the point cloud of the rear edge of the blade profile by adopting a least square method to obtain theoretical central point coordinates and actual central point coordinates of the front edge and the rear edge.
And 3, respectively carrying out curve fitting on the theoretical point cloud and the actual point cloud of the leaf basin and the leaf back by adopting a NURBS method.
And 4, fitting the blade profile mean camber line. The definition of the camber line is: the center of the blade profile inscribed circle is connected with the center of the front/rear edge, and extends to intersect with the front/rear edge in the tangential direction at the center of the front/rear edge. Therefore, according to the molded lines of the basin and the back of the blade obtained in the step 2, a series of inscribed circle data inside the blade profile are obtained by using an inscribed circle method, and the circle center of the obtained series of inscribed circles is the theoretical mean camber line point cluster Pi(i ═ 1,2,. cndot, n) and cluster of actual mean camber line points Pi' (i ═ 1, 2.. times, n), then sorting and de-noising the clusters of pointsAnd interpolating.
Step 5, the coordinates of the theoretical center point of the front edge/the rear edge obtained in the step 2 and the point cluster P obtained in the step 4 are combinediAnd (i ═ 1, 2., n), carrying out NURBS curve fitting, and extending the tangent direction at the center of the front/rear edge to intersect with the front/rear edge, so as to obtain the theoretical mean camber line of the blade profile.
Similarly, the coordinates of the actually measured central point of the front edge/the rear edge obtained in the step 2 and the point cluster P obtained in the step 4 are usedi' n, and extending the tangent direction at the center of the front/rear edge to intersect with the front/rear edge to obtain the actually measured camber line of the blade profile.
And 6, calculating the intersection point of the theoretical front and rear edge (elliptic) circular arcs and the theoretical mean camber lines, and calling the two intersection points as a front edge theoretical vertex and a rear edge theoretical vertex.
And 7, calculating a curvature radius value rho (L) of the theoretical top point of the front edge and a curvature radius value rho (T) of the theoretical top point of the rear edge according to the (elliptical) arc curvature radius calculation formula by the theoretical front/rear edge (elliptical) arcs fitted in the step 2.
And 8, carrying out NURBS curve fitting on the measurement points of the front/rear edge parts. According to the definition of curve curvature, a curvature radius model of the actual curve of the front edge/the rear edge is calculated, and NURBS curve curvature and curvature radius are calculated according to the following formula:
Figure BDA0003092505220000091
Figure BDA0003092505220000092
in the formula, k(u)For curve curvature, p '(u) and p' (u) are the first and second derivatives of the points determined by the curve parameter u, and ρ is the radius of curvature of the curve.
And 9, calculating the intersection points of the front edge actual curve and the rear edge actual curve and the actual camber line, wherein the two intersection points are called a front edge actual vertex and a rear edge actual vertex.
Further, according to the curvature radius model obtained in the previous step, the curvature radius value ρ (L ') of the front edge actual vertex and the curvature radius value ρ (T') of the rear edge actual vertex are calculated, respectively.
Hereinafter, the shape of a certain intake/exhaust edge (leading edge or trailing edge, which is the same in judgment and will be referred to as a "blade edge" hereinafter for convenience of description) is analyzed and evaluated.
Step 10, calculating the ratio of the actual vertex V' curvature radius to the theoretical vertex V curvature radius
Figure BDA0003092505220000093
And 11, interpreting the shape of the pointed end. As can be seen in fig. 5, the blade edge is pointed with the following features: the radius of curvature at the tip V' of the blade edge is significantly smaller than the theoretical value. So that the ratio obtained in step 11 can be used
Figure BDA0003092505220000094
As a characteristic value for the tip interpretation. Setting the threshold value of the characteristic value as
Figure BDA0003092505220000095
If it is
Figure BDA0003092505220000096
Judging that the blade edge is in a tip shape and turning to step 13; otherwise step 12 is entered.
And step 12, judging the shape of the blunt head. As can be seen in fig. 6, the blade edge has a blunt shape with the following features: (i) obvious minimum values of curvature radius appear on two sides of the blade edge; (ii) the radius of curvature of the location of the tip of the blade edge itself is significantly greater than on both sides.
Further, it is judged whether or not the curvature radius minimum value point M, N shown in FIG. 6 appears on both sides of the actual vertex, and if it exists, the distance d between the two points is determinedMNAs a feature value of blunt interpretation, a threshold value of the feature value is set to (d)MN)max. If d isMN＞(dMN)maxThen, the feature (i) is satisfied.
Further, the ratio obtained in step 9
Figure BDA0003092505220000101
As a characteristic value of the blunt interpretation, the threshold value of the characteristic value is set to
Figure BDA0003092505220000102
If it is
Figure BDA0003092505220000103
The (ii) feature is met.
If the blade edge meets the characteristics (i) and (ii) at the same time, the blade edge can be determined to be blunt.
Step 13, calculating the intersection point of the actual curve and the theoretical curve of the blade edge, and combining the series of points Qi(i ═ 1, 2.., n) is referred to as the "leaf intersection.
And step 14, judging the shape of the head with skew. As can be seen from fig. 7, the blade edge has a skew shape with the following features: (i) the two sides of the mean camber line are obviously asymmetric; (ii) on the plump side of the molded line, the distribution of the blade profile curve in the profile tolerance zone from the front edge to the back obviously has a process of continuously changing from the upper limit to the lower limit (the back edge is from the back to the front) and passing through the nominal profile.
And when the deviation of the full side of the molded line has no trend of changing from the upper limit to the lower limit, the head is not judged to be head-skewed.
Further, the distance d from the actual vertex to the theoretical mean camber line is calculatedlThis is used as a feature value for head-skewing determination. Setting the threshold value of the characteristic value as (d)l)max. If d isl＞(dl)maxThen, the condition (i) is satisfied.
Further, whether a leaf-shaped intersection point exists on the plump side (namely, the actual vertex side) of the molded line is judged, and if so, a leaf-shaped intersection point Q closest to the vertex is taken as shown in FIG. 7kSeparately calculate QkThe maximum positive deviation devi (A) and the maximum negative deviation | devi (B) of the two side regions, devi (A) + | devi (B) is used as a characteristic value for the head-off judgment, and the characteristic value of the threshold is set as [ devi (A) + | devi (B) ]]max. If the following conditions are met:
[devi(A)+|devi(B)|]＞[devi(A)+|devi(B)|]max
the condition (ii) is met. If the blade edge meets the characteristics (i) and (ii) at the same time, the blade edge can be determined to be in a skewed shape.
And step 15, judging the shape of the necking. As can be seen in fig. 8, the blade edge has a constricted shape with the following characteristics: the molded lines on the two sides of the basin back pass through the nominal contour from the two sides of the front edge to the back and have a process of continuously changing from the upper limit to the lower limit (the back edge is from the back to the front).
Further, whether the blade profile intersection points exist on both sides of the actual vertex is judged, if so, the blade profile intersection points Q with the blade basin side and the blade back side closest to the vertex are respectively taken as shown in FIG. 8kAnd Qk+1Separately calculate QkAnd Qk+1The maximum positive deviation devi (A) and the maximum negative deviation | devi (B) of the two side regions are used as the characteristic value for judging necking, and the characteristic value of the threshold is set as [ devi (A) + | devi (B) ]]max. If the basin back meets the following requirements:
[devi(A)+|devi(B)|]＞[devi(A)+|devi(B)|]max
the blade edge is determined to be in the shape of a neck.
And step 16, judging the size/the small size and the shape. As can be seen in fig. 9, the blade edge has a big/small shape with the following characteristics: the edge profile undergoes a continuous change near "min-max-min" or "max-min-max" and the area of change is near or covers the edge vertex.
Further, the change condition of the point cloud deviation value at the leaf edge is analyzed, the continuous change of negative-positive-negative exists, namely the leaf profile is close to the minimum-maximum-minimum, and the continuous change of positive-negative-positive exists, namely the leaf profile is close to the maximum-minimum-maximum. Therefore, whether three sections of continuous change areas meeting the change phenomenon of negative-positive-negative/positive-negative-positive can be judged, and the actual vertexes of the blade edges are covered. If the deviation value exists, calculating extreme values | devi (A) |, | devi (B) |, | devi (C) | of the deviation value of the area between every two adjacent leaf profile intersection points, and taking the deviation extreme values as one characteristic value for interpretation. Setting the threshold value of the characteristic value to devimaxIf, at the same time:
|devi(A)|＞devimax；
|devi(B)|＞devimax；
|devi(C)|＞devimax；
the leaf edge is determined to be a big/small shape.
And step 17, evaluating the shape of the air inlet and outlet edges of the blade according to the analysis results of the steps 11-16: normal, sharp, blunt, skewed, necked, or size/small.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.

Claims (10)

1. A method for detecting the shape of an air inlet and outlet edge of an aircraft engine blade is characterized by comprising the following steps:
acquiring blade profile contour theoretical point cloud data of a blade, blade profile contour actual measurement point cloud data of the blade and a deviation value between the blade profile contour theoretical point cloud data and the blade profile contour actual measurement point cloud data, wherein the blade profile contour theoretical point cloud data and the blade profile contour actual measurement point cloud data respectively comprise point cloud data corresponding to a blade basin, a blade back, a front edge and a rear edge;
performing curve fitting according to the theoretical point cloud data of the blade profile to obtain a theoretical blade profile curve and a theoretical blade profile pitch arc, and performing curve fitting according to the actually measured point cloud data of the blade profile to obtain an actually measured blade profile curve and an actually measured blade profile pitch arc;
calculating according to the theoretical blade profile curve and the theoretical mean camber line to obtain a leading edge theoretical peak and a trailing edge theoretical peak; calculating according to the actually measured blade profile curve and the actually measured mean camber line to obtain an actually measured vertex of the front edge and an actually measured vertex of the rear edge;
respectively calculating a leading edge theoretical vertex curvature radius and a trailing edge theoretical vertex curvature radius according to the leading edge theoretical vertex and the trailing edge theoretical vertex, and respectively calculating a leading edge actual measurement vertex curvature radius and a trailing edge actual measurement vertex curvature radius according to the leading edge actual measurement vertex and the trailing edge actual measurement vertex;
and judging the shape of the front edge and the shape of the rear edge of the blade according to the comparison of the front edge theoretical vertex curvature radius and the rear edge theoretical vertex curvature radius with the front edge actual measurement vertex curvature radius and the rear edge actual measurement vertex curvature radius.
2. The method for detecting the shape of the air inlet and outlet edges of the aircraft engine blade according to claim 1, wherein the step of performing curve fitting according to the theoretical point cloud data of the blade profile to obtain a theoretical blade profile curve and a theoretical mean camber line and the step of performing curve fitting according to the actually measured point cloud data of the blade profile to obtain an actually measured blade profile curve and an actually measured mean camber line comprises the following steps:
performing curve fitting on the theoretical point cloud data of the leaf profile according to a least square method and a NURBS method to obtain a theoretical leaf profile curve and a theoretical mean camber line;
and performing curve fitting on the actually measured point cloud data of the leaf profile according to a least square method and a NURBS method to obtain an actually measured leaf profile curve and an actually measured mean camber line.
3. The method for detecting the shape of the air inlet and outlet edges of the aero-engine blade as claimed in claim 2, wherein the step of performing curve fitting on the theoretical point cloud data of the blade profile according to a least square method and a NURBS method to obtain a theoretical blade profile curve and a theoretical blade profile mean camber line comprises the following steps:
respectively carrying out circle fitting or ellipse fitting on the leading edge point cloud data and the trailing edge point cloud data in the leaf profile theoretical point cloud data according to a least square method to obtain a fitted leading edge theoretical circle center coordinate and a fitted trailing edge theoretical circle center coordinate;
respectively performing curve fitting on the leaf basin point cloud data and the leaf back point cloud data in the leaf profile theoretical point cloud data according to a NURBS method;
calculating the theoretical point cloud data of the leaf profile according to an inscribed circle method to obtain a theoretical inscribed circle center point;
and carrying out NURBS curve fitting according to the theoretical center coordinates of the front edge, the theoretical center coordinates of the rear edge and the theoretical center point of the inscribed circle to obtain a theoretical blade profile camber line.
4. The method for detecting the shape of the air inlet and outlet edges of the aero-engine blade as claimed in claim 3, wherein the calculating according to the theoretical blade profile curve and the theoretical mean camber line to obtain the leading edge theoretical peak and the trailing edge theoretical peak comprises:
calculating the intersection point of a theoretical front edge circular arc or a front edge elliptic arc and the theoretical mean camber line to obtain a front edge theoretical vertex;
and calculating the intersection point of the theoretical trailing edge circular arc or the trailing edge elliptic arc and the theoretical mean camber line to obtain the theoretical vertex of the trailing edge.
5. The method for detecting the shape of the inlet and outlet edges of the aero-engine blade according to claim 4, wherein the step of calculating the leading edge theoretical vertex curvature radius and the trailing edge theoretical vertex curvature radius according to the leading edge theoretical vertex and the trailing edge theoretical vertex respectively comprises the steps of:
calculating the curvature radius value of the theoretical vertex of the front edge according to an arc curvature radius calculation formula or an elliptic arc curvature radius calculation formula and the theoretical front edge arc or the front edge elliptic arc;
and calculating the curvature radius value of the theoretical vertex of the trailing edge according to an arc curvature radius calculation formula or an elliptic arc curvature radius calculation formula and the theoretical trailing edge arc or the trailing edge elliptic arc.
6. The method for detecting the shape of the air inlet and outlet edges of the aero-engine blade as claimed in claim 2, wherein the step of performing curve fitting on the point cloud data of the measured blade profile point cloud according to a least squares method and a NURBS method to obtain a measured blade profile curve and a measured mean camber line comprises the steps of:
respectively carrying out circle fitting or ellipse fitting on the leading edge point cloud data and the trailing edge point cloud data in the measured point cloud data of the blade profile outline according to a least square method to obtain fitted leading edge measured circle center coordinates and trailing edge measured circle center coordinates;
respectively performing curve fitting on the leaf basin point cloud data and the leaf back point cloud data in the actually measured point cloud data of the leaf profile according to a NURBS method;
calculating the actually measured point cloud data of the leaf profile according to an inscribed circle method to obtain an actually measured inscribed circle center point;
and carrying out NURBS curve fitting according to the measured center coordinates of the front edge, the measured center coordinates of the rear edge and the measured inscribed circle center point to obtain the measured blade profile camber line.
7. The method for detecting the shape of the air intake and exhaust edges of the aircraft engine blade as recited in claim 6, wherein the step of calculating the measured leading edge vertex and the measured trailing edge vertex according to the measured profile curve and the measured mean camber line comprises:
carrying out NURBS curve fitting on the actual measurement points of the front edge of the blade and the actual measurement points of the rear edge of the blade respectively to obtain an actual curve of the front edge of the blade and an actual curve of the rear edge of the blade;
and calculating the intersection point of the actual curve of the blade leading edge and the camber line of the actual blade profile to obtain an actual vertex of the leading edge, and calculating the intersection point of the actual curve of the blade trailing edge and the camber line of the actual blade profile to obtain an actual vertex of the trailing edge.
8. The method for detecting the shape of the inlet and outlet edges of the aircraft engine blade as claimed in claim 7, wherein the step of calculating the curvature radius of the measured leading edge vertex and the curvature radius of the measured trailing edge vertex from the measured leading edge vertex and the measured trailing edge vertex respectively comprises the steps of:
respectively calculating a curvature radius model of the actual curve of the front edge of the blade and a curve radius model of the actual curve of the rear edge of the blade;
and calculating the curvature radius value of the actual vertex of the front edge according to the curvature radius model of the actual curve of the front edge of the blade, and calculating the curvature radius value of the actual vertex of the rear edge according to the curve radius model of the actual curve of the rear edge of the blade.
9. The method for detecting the shape of the inlet and outlet edges of the aero-engine blade according to claim 1, wherein the step of judging the shape of the leading edge and the shape of the trailing edge of the blade according to the comparison between the leading edge theoretical vertex curvature radius and the trailing edge theoretical vertex curvature radius and the leading edge actual measurement vertex curvature radius and the trailing edge actual measurement vertex curvature radius comprises the following steps:
calculating the ratio of the theoretical vertex curvature radius of the front edge to the actual vertex curvature radius of the front edge to obtain the ratio of the curvature radii of the front edge;
calculating the ratio of the theoretical vertex curvature radius of the trailing edge to the actual vertex curvature radius of the trailing edge to obtain the ratio of the curvature radii of the trailing edge;
and respectively comparing the ratio of the curvature radius of the front edge and the ratio of the curvature radius of the rear edge with a preset theoretical range, and judging the shape of the front edge and the shape of the rear edge of the blade according to the comparison result.
10. The method for detecting the shape of the inlet and outlet edges of the aero-engine blade as claimed in claim 9, wherein the comparing the ratio of the radius of curvature of the leading edge and the ratio of the radius of curvature of the trailing edge with a preset theoretical range respectively, and the determining the shape of the leading edge and the shape of the trailing edge of the blade according to the comparison result comprises:
when the ratio of the curvature radius of the front edge is smaller than the lower limit value of the preset theoretical range, the shape of the front edge of the blade is judged to be a pointed shape, and when the ratio of the curvature radius of the rear edge is smaller than the lower limit value of the preset theoretical range, the shape of the rear edge of the blade is judged to be a pointed shape;
when the ratio of the curvature radius of the front edge is not smaller than the lower limit value of the preset theoretical range, if the minimum value of the curvature radius appears on both sides of the front edge of the blade and the ratio of the curvature radius of the front edge is larger than the upper limit value of the preset theoretical range, the shape of the front edge of the blade is determined to be a blunt shape; when the ratio of the curvature radius of the trailing edge is not less than the lower limit value of the preset theoretical range, if the minimum value of the curvature radius appears on both sides of the trailing edge of the blade and the ratio of the curvature radius of the trailing edge is greater than the upper limit value of the preset theoretical range, the shape of the trailing edge of the blade is determined to be a blunt shape;
when the shape of the front edge of the blade is judged to be a pointed shape or a blunt shape, calculating a front edge blade profile intersection point between an actual curve of the front edge of the blade and the theoretical blade profile curve, and when the shape of the rear edge of the blade is judged to be a pointed shape or a blunt shape, calculating a rear edge blade profile intersection point between an actual curve of the rear edge of the blade and the theoretical blade profile curve;
judging whether the leading edge shape of the blade has any one or more of a skewed shape feature, a necking shape feature and a size/size shape feature according to the change trend of the leading edge blade profile intersection point; and judging whether the trailing edge shape of the blade has any one or more of a crooked head shape characteristic, a necking shape characteristic and a size/size shape characteristic according to the change trend of the trailing edge blade profile intersection point.
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