A method for measuring and evaluating air film holes on blades

Abstract

The present invention discloses a method for measuring and evaluating blade film holes, comprising: measuring blade film holes by using a composite measuring ray coordinate machine to obtain measurement point cloud data of the blade film holes; parsing the MBD model file of the blade film holes to establish a theoretical design parameter table of the blade film holes; automatically segmenting the measurement point cloud data of the blade film holes based on the theoretical design parameter table of the blade film holes established by the analysis to obtain the measured point cloud data of each film hole in the blade; fitting and evaluating the cylindrical surface of the film holes based on the measured point cloud data of the blade film holes after the automatic segmentation to obtain the geometric parameters of the film holes. The present invention can achieve high-precision measurement of blade film holes and automatic evaluation of the geometric parameters of the film holes.

Description

Technical Field

[0001] The invention belongs to the field of geometric parameter measurement and evaluation, and in particular relates to a blade film hole measurement and evaluation method. Background Art

[0002] As the core component of aircraft engines, turbine blades are processed with a large number of air film holes (aperture of about 0.1mm to 0.8mm, and depth of more than 3mm) on the blade body. The cold air released from the inside of the component is convected through the tiny air film holes to form a thin layer of cold air film on the surface of the component, so as to achieve the purpose of isolating the high-temperature combustion gas flow and protecting the component. Air film holes have the characteristics of small aperture, large number, complex spatial angle, and high depth-to-diameter ratio. Not only is the processing process difficult and the forming precision requirements are high, but how to achieve accurate detection has always been a technical problem in the industry.

[0003] At present, there are three main methods for measuring the film holes of turbine blades, namely optical 3D scanning measurement technology, fiber optic measurement technology and industrial CT measurement technology. Optical 3D scanning measurement technology has fast measurement speed and high measurement accuracy, but the measurement of the inner wall of the film hole is limited and it is impossible to obtain relatively complete measurement data; fiber optic measurement technology is generally combined with a coordinate measuring machine to achieve the measurement of small holes with the highest measurement accuracy, but it requires single-hole measurement and the cost of fiber optic is relatively high; industrial CT measurement technology can complete the measurement of the film holes of the blades through tomography of the inner wall of the blades, but the measurement accuracy is not high. In addition, regarding the evaluation method of the film holes, the current commercial software mostly uses a manual interactive evaluation method, which selects point cloud data of different film hole positions, and then performs fitting and evaluation. The evaluation efficiency is not high, and the participation of information related to the design model of the blade film holes is low. Summary of the invention

[0004] The object of the present invention is to provide a blade film hole measurement and evaluation method, which can achieve high-precision measurement of the blade film holes and automatic evaluation of the geometric parameters of the film holes.

[0005] One aspect of the present invention provides a blade film hole measurement and evaluation method, comprising:

[0006] The blade air film holes are measured using a composite measuring ray coordinate machine to obtain the measurement point cloud data of the blade air film holes;

[0007] Analyze the MBD model file of the blade film hole and establish the theoretical design parameter table of the blade film hole;

[0008] Based on the theoretical design parameter table of the blade film holes established by analysis, the measured point cloud data of the blade film holes are automatically segmented to obtain the measured point cloud data of each film hole in the blade;

[0009] Based on the measured point cloud data of the film holes of the blade after automatic segmentation, the cylindrical surface of the film holes is fitted and evaluated to obtain the geometric parameters of the film holes.

[0010] Preferably, the composite measurement ray coordinate measuring machine includes a coordinate measuring machine and a CT measuring device, and the method of measuring the air film holes of the blade by using the composite measurement ray coordinate measuring machine includes:

[0011] Firstly, the blade surface of the blade film holes is measured by a coordinate measuring machine, and then the blade film holes are measured by CT measuring equipment. Finally, the measurement data of the coordinate measuring machine and CT measuring equipment are effectively fused to obtain the measurement point cloud data of the blade film holes.

[0012] Preferably, the measuring of the blade surface of the blade film hole by using a coordinate measuring machine comprises: placing the measured blade on a turntable by means of a fixture, measuring the blade film hole by using the coordinate measuring machine, and establishing a precise coordinate conversion model among the coordinate measuring machine, the CT measuring device, the turntable, the fixture and the measured blade;

[0013] The method of using a CT measuring device to perform tomographic scanning measurement on the blade film holes comprises: using a CT measuring device to perform tomographic scanning measurement on the blade film holes, performing data conversion on the obtained CT image of the film holes, and obtaining measurement point cloud data of the blade film holes;

[0014] The effective fusion of the measurement data of the coordinate measuring machine and the CT measuring device includes: using the established precise coordinate transformation model and taking the measurement data of the coordinate measuring machine as a reference to perform high-precision registration and alignment of the measurement data of the coordinate measuring machine and the CT measuring device.

[0015] Preferably, the theoretical design parameter table of the blade film holes includes the number, size, shape and position parameters of the film holes.

[0016] Preferably, the automatically segmenting the measured point cloud data of the air film holes of the blade to obtain the measured point cloud data of each air film hole in the blade comprises:

[0017] Based on the theoretical design parameter table of the air film hole, the bounding box of the air film hole is established, and the measured point cloud data of the blade air film hole is roughly segmented with the help of the bounding box information;

[0018] Through the relationship discrimination algorithm between points and the point cloud of the film hole surface, the precise segmentation of the measured point cloud data of the film holes in the blade is completed, and the measured point cloud data of each film hole in the blade is obtained.

[0019] Preferably, the algorithm for determining the relationship between the point and the point cloud of the air film hole surface is as follows: through the position information of the air film hole in the theoretical design parameter table of the air film hole, find a point in the measured point cloud data corresponding to the air film hole as a search seed, and the constraints are the distance from the neighborhood point to the surface and the normal vector of the point, and perform a point cloud search on the cylindrical surface of the air film hole; at the same time, for the boundary points of the cylindrical surface, the Crust algorithm is used. When the seed searches all the boundary points, the point cloud segmentation process ends, and the measured point cloud segmentation result of the cylindrical surface is obtained, which is the measured point cloud data of the air film hole.

[0020] Preferably, the cylindrical surface fitting algorithm is an LM fitting algorithm, the initial value is determined according to the air film hole theory design parameter table, and then the LM nonlinear fitting is performed.

[0021] Preferably, the geometric parameters of the air film hole include the diameter, cylindricity, position and inclination of the air film hole.

[0022] The blade film hole measurement and evaluation method according to the above aspect of the present invention can achieve high-precision measurement of the blade film holes and automatic evaluation of the geometric parameters of the film holes. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings used in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work:

[0024] Figure 1 It is a flow chart of a blade film hole measurement and evaluation method according to an embodiment of the present invention;

[0025] Figure 2 is a schematic diagram of a composite measurement ray coordinate machine according to an embodiment of the present invention;

[0026] Figure 3 It is a schematic diagram of the cylindrical surface fitting of the blade film hole according to one embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] An embodiment of the present invention provides a method for measuring and evaluating film holes on a blade. Figure 1FIG. 1 is a flow chart of a blade film hole measurement and evaluation method according to an embodiment of the present invention. Figure 1 As shown, the blade film hole measurement and evaluation method according to the embodiment of the present invention includes steps S1 to S4.

[0029] In step S1, the blade film holes are measured using a composite measurement ray coordinate machine to obtain measurement point cloud data of the blade film holes.

[0030] The composite measuring ray coordinate measuring machine is as follows Figure 2 As shown, it includes a coordinate measuring machine 11 and a CT measuring device, and the CT measuring device includes a ray source 12 and a flat panel detector 13. The use of a composite measuring ray coordinate machine to measure the air film holes of a blade refers to placing the blade with the air film holes to be measured on a turntable with the help of a special fixture based on the complementary advantages of the coordinate measuring machine and the CT measuring device technology, firstly measuring the blade surface of the air film holes of the blade by using the coordinate measuring machine, and then performing tomographic scanning measurement of the air film holes of the blade by using the CT measuring device, and finally effectively integrating the measurement data of the coordinate measuring machine and the CT measuring device to obtain the measurement point cloud data of the air film holes of the blade.

[0031] Specifically, a high-precision coordinate measuring machine is first used to locate and measure the blade surface of the blade film holes, and the coordinate measuring machine measurement data is used as the reference data of the blade film hole measurement data. A precise coordinate conversion model is established among the coordinate measuring machine, CT measuring equipment, turntable, fixture and measured blade as a basis for the registration and alignment of the two types of measurement data from the coordinate measuring machine and the CT measuring equipment. The CT measuring equipment is then used to perform tomographic scanning measurement of the blade film holes, and the obtained CT images of the film holes are converted into measurement data in STL format using relevant CT scanning measurement software to obtain measurement point cloud data of the blade film holes. Finally, the established precise coordinate conversion model is used to effectively and highly precisely register and align the measurement data of the coordinate measuring machine and the CT measuring equipment with the measurement data of the coordinate measuring machine as a reference, and finally the high-precision measurement point cloud data of the blade film holes is obtained.

[0032] In step S2, the MBD model file of the blade film hole is parsed to establish a theoretical design parameter table of the blade film hole.

[0033] The blade film hole MBD (Model Based Definition) model file is parsed, including but not limited to STEP, STP, CATPART, SLDPRT, PRT and other format model files, and a theoretical design parameter table of the blade film hole is established based on secondary development of relevant geometric kernels or modeling software such as OpenCascade, ACIS, Parasolid, etc.; the theoretical design parameter table of the blade film hole includes parameters such as the number, size, shape and position of the film hole.

[0034] In one embodiment, the STEP format file of the blade film hole MBD is parsed, and a parsing module is developed based on the relevant functions in the OpenCascade geometry kernel to establish a theoretical design parameter table containing parameters such as the blade film hole number, diameter, cylindricity, position, and inclination.

[0035] In step S3, based on the blade film hole theoretical design parameter table established by analysis, the measured point cloud data of the blade film holes are automatically segmented to obtain the measured point cloud data of each film hole in the blade.

[0036] The automatic segmentation of the measured point cloud data of the blade film holes is based on the theoretical design parameter table of the blade film holes established by analysis. On the basis of the complete alignment of the theoretical model of the blade film holes and the measured point cloud data, the measured point cloud data of the blade film holes are automatically segmented to obtain the actual measured point cloud data of each air film hole in the blade, and the measured data are named according to the number.

[0037] The automatic segmentation of the measured point cloud data of the blade film holes includes two steps: one is to establish a bounding box of the air film holes based on the theoretical design parameter table of the air film holes, and to roughly segment the point cloud data of the blade film holes with the help of the bounding box information of the air film holes to improve the calculation efficiency of the precise segmentation; the second is to complete the precise segmentation of the point cloud data of the blade film holes through the relationship discrimination algorithm between the points and the point cloud of the air film hole surface, and obtain the measured point cloud data of each air film hole in the blade.

[0038] The algorithm for determining the relationship between the point and the point cloud of the air film hole surface is that, since the air film hole is usually designed as a cylindrical surface, the position information of the air film hole in the theoretical design parameter table is used to find a point in the measured point cloud data corresponding to the air film hole as a search seed. The constraints are the distance from the neighborhood point to the surface and the normal vector of the point, as shown in formulas (1) and (2), and the point cloud search of the cylindrical surface is performed. At the same time, for the boundary points of the cylindrical surface, the Crust algorithm is used. When the seed searches all the boundary points, the point cloud segmentation process ends and the measured point cloud segmentation result of the cylindrical surface is automatically obtained, which is the measured point cloud data of the air film hole.

[0039]

[0040] Where D i represents the target error function of cylindrical surface fitting, (a, b, c) is the direction vector of the cylinder axis, (x0, y0, z0) is a point on the cylinder axis, (x i ,y i , z i ) is the measured point cloud.

[0041]

[0042] Wherein, (A, B, C) is the direction vector of the measured point obtained by the method of fitting a plane with neighborhood points, which is used as the direction vector of the measured point.

[0043] In step S4, based on the measured point cloud data of the film holes of the blade after automatic segmentation, the cylindrical surface of the film holes is fitted and evaluated to obtain the geometric parameters of the film holes.

[0044] The automatic evaluation of geometric parameters such as blade film hole size, shape and position parameters is based on the measured point cloud data of blade film holes after automatic segmentation, such as Figure 3 As shown, the cylindrical surface is fitted and evaluated, and the diameter, cylindricity, position, inclination and other parameters of the air film hole are obtained as evaluation results. For example, cylindricity refers to the difference between the maximum and minimum values ​​of the distance from the cylindrical surface test data to the least squares fitting cylindrical axis, and the least squares fitting cylindrical axis has been fitted and calculated.

[0045] The cylindrical surface fitting algorithm is a LM (Levenberg-Marquardt) fitting algorithm, the initial value is determined according to a theoretical design parameter table, and then the LM nonlinear fitting is performed.

[0046] Preferably, the radiation source in the CT measuring device is selected to be 300KV or above.

[0047] As a preferred option, the composite measurement ray coordinate machine selects multi-axis linkage control, inputs motion control instructions through the human-computer interaction interface, and combines the real-time feedback of the driver position loop and speed loop to efficiently and accurately realize the control movement of the coordinate measuring machine and CT measuring equipment.

[0048] Preferably, the STL format is selected to convert the CT image data into point cloud data.

[0049] As a preferred method, the automatic segmentation of the air film hole point cloud data is completed through an algorithm for distinguishing the relationship between points and the air film hole surface point cloud, mainly based on the distance from the measured point cloud to the surface, the change of the point cloud normal vector and the judgment of the air film hole surface boundary.

[0050] The blade film hole measurement and evaluation method of the above embodiment of the present invention realizes automatic and accurate evaluation of the measured point cloud data of the blade film hole through the measurement of the blade film hole by the composite measurement ray coordinate machine and the conversion of the measurement data, the analysis of the MBD model of the film hole, the automatic segmentation of the film hole point cloud data and the automatic evaluation of the geometric parameters such as the size, shape and position parameters. The blade film hole measurement and evaluation method of the above embodiment of the present invention has the following beneficial effects:

[0051] 1. The MBD model of the blade film hole is introduced into the processing of the film hole measurement point cloud data, and the analytical information is used to establish the theoretical design parameter table of the film hole. The automatic segmentation of the measured point cloud of the film hole and the automatic evaluation of the relevant geometric parameters are realized through the designed surface point cloud relationship discrimination algorithm, which breaks through the original working mode of manual interactive evaluation of the geometric parameters of the film hole, improves the efficiency of the inspectors in evaluating the film hole, and reduces the labor intensity.

[0052] 2. Through the high-precision registration of two types of measurement data from the coordinate measuring machine and the CT measuring equipment, high-precision measurement of the air film holes on the blades is achieved. This can be said to make up for the low accuracy of the CT measuring equipment and provide theoretical and technical support for the measurement technology accuracy, flexibility and intelligence of the air film holes on blades in my country.

[0053] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for measuring and evaluating blade film holes, characterized in that: include: The blade film holes are measured using a composite measuring ray coordinate machine to obtain the measurement point cloud data of the blade film holes; Analyze the MBD model file of the blade film hole and establish the theoretical design parameter table of the blade film hole; Based on the theoretical design parameter table of the blade film holes established by analysis, the measured point cloud data of the blade film holes are automatically segmented to obtain the measured point cloud data of each film hole in the blade; Based on the measured point cloud data of the film holes of the blades after automatic segmentation, the cylindrical surface of the film holes is fitted and evaluated to obtain the geometric parameters of the film holes. The composite measuring ray coordinate measuring machine includes a coordinate measuring machine and a CT measuring device. The method of measuring the air film holes of the blade using the composite measuring ray coordinate measuring machine includes: Firstly, the blade surface of the blade film hole is measured by using a coordinate measuring machine, and then the blade film hole is measured by tomography using a CT measuring device. Finally, the measurement data of the coordinate measuring machine and the CT measuring device are effectively fused to obtain the measurement point cloud data of the blade film hole. The automatic segmentation of the measured point cloud data of the air film holes of the blade to obtain the measured point cloud data of each air film hole in the blade includes: Based on the theoretical design parameter table of the air film hole, the bounding box of the air film hole is established, and the measured point cloud data of the blade air film hole is roughly segmented with the help of the bounding box information; Through the relationship discrimination algorithm between points and the point cloud of the film hole surface, the precise segmentation of the measured point cloud data of the film holes in the blade is completed, and the measured point cloud data of each film hole in the blade is obtained.

2. The method according to claim 1, characterized in that The method of measuring the blade surface of the blade film hole by using a coordinate measuring machine comprises: placing the measured blade on a turntable by means of a fixture, measuring the blade film hole by using a coordinate measuring machine, and establishing a precise coordinate conversion model among the coordinate measuring machine, the CT measuring device, the turntable, the fixture and the measured blade; The method of using a CT measuring device to perform tomographic scanning measurement on the blade film holes comprises: using a CT measuring device to perform tomographic scanning measurement on the blade film holes, performing data conversion on the obtained CT image of the film holes, and obtaining measurement point cloud data of the blade film holes; The effective fusion of the measurement data of the coordinate measuring machine and the CT measuring device includes: using the established precise coordinate transformation model and taking the measurement data of the coordinate measuring machine as a reference to perform high-precision registration and alignment of the measurement data of the coordinate measuring machine and the CT measuring device.

3. The method according to claim 1 or 2, characterized in that The theoretical design parameter table of the blade film holes includes the number, size, shape and position parameters of the film holes.

4. The method according to claim 1 or 2, characterized in that: The algorithm for determining the relationship between the point and the point cloud of the air film hole surface is as follows: through the position information of the air film hole in the air film hole theoretical design parameter table, find a point in the measured point cloud data corresponding to the air film hole as a search seed, and the constraints are the distance from the neighborhood point to the surface and the normal vector of the point, and perform a point cloud search on the cylindrical surface of the air film hole; at the same time, for the boundary points of the cylindrical surface, the Crust algorithm is used. When the seed searches all the boundary points, the point cloud segmentation process ends, and the measured point cloud segmentation result of the cylindrical surface is obtained, which is the measured point cloud data of the air film hole.

5. The method according to claim 1 or 2, characterized in that: The cylindrical surface fitting algorithm is an LM fitting algorithm, the initial value is determined according to the air film hole theory design parameter table, and then the LM nonlinear fitting is performed.

6. The method according to claim 1 or 2, characterized in that: The geometric parameters of the air film hole include the diameter, cylindricity, position and inclination of the air film hole.

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