A hierarchical progressive geometry feature measurement method for a water turbine runner

Abstract

The application discloses a hierarchical progressive geometric feature measurement method for a water turbine runner, and comprises the following steps: S1, establishing a hierarchical progressive geometric feature evaluation system for the water turbine runner; S2, establishing a multi-level progressive measurement strategy of "global-local-detail", which comprises adopting global photogrammetry reference features, adopting laser tracking measurement of main features, and adopting handheld scanner measurement of detail features; S3, implementing data real-time splicing and registration in the measurement process, and unifying the measurement data of different levels to the same coordinate system through a feature point matching algorithm; and S4, adjusting the measurement density based on the feature level, and performing real-time evaluation and supplementary measurement on the measurement data. The method can efficiently and accurately complete the geometric feature measurement task of the water turbine runner by combining different measurement means and the progressive measurement strategy, and significantly improves the measurement efficiency and precision.

Description

Technical Field

[0001] This invention relates to the field of hydropower station equipment testing technology, and in particular to a hierarchical progressive geometric feature measurement method for a turbine runner. Background Technology

[0002] The turbine runner is a core component of a hydroelectric power unit, and its geometric accuracy directly affects the unit's operating efficiency and safety. As hydroelectric power units develop towards larger and more efficient models, the requirements for the geometric accuracy of the runner are becoming increasingly stringent. However, current runner measurement work faces multiple challenges.

[0003] First, turbine runners are characterized by their large size and complex curved surfaces, with their geometric features distributed across different spatial scales. From the overall installation datum to the details of local curvature, precise measurements are required. Traditional single-method measurement is insufficient to simultaneously meet the measurement needs of different features, often necessitating repeated measurements using multiple tools, which is not only time-consuming and labor-intensive but also prone to data inconsistencies. Second, existing measurement methods lack systematicity and hierarchy, often employing a "one-size-fits-all" approach to uniformly measure the entire blade. This approach wastes measurement resources in non-critical areas and may lead to insufficient measurement accuracy in critical feature areas. Particularly in areas with drastic curvature changes, using a uniform measurement density can easily result in the omission of important features or insufficient measurement accuracy. Furthermore, the importance and accuracy requirements of different geometric features on the runner vary significantly. For example, the positional accuracy of the installation datum directly affects the installation quality, while the accuracy of local curved surfaces affects the local flow regime. Existing measurement methods often fail to provide targeted measurements based on the importance of different features, resulting in low measurement efficiency. Therefore, the hydropower industry urgently needs a turbine runner measurement method that can systematically solve the above problems. Summary of the Invention

[0004] To address the existing technical problems, the main objective of this invention is to provide a hierarchical progressive geometric feature measurement method for turbine runners. This method improves the measurement efficiency and accuracy of turbine runners by performing hierarchical measurements based on the importance of the runner's geometric features, employing corresponding measurement methods and densities, and conducting real-time evaluation and supplementary measurements.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a hierarchical progressive geometric feature measurement method for a water turbine runner, comprising the following steps:

[0006] S1. Establish a hierarchical progressive evaluation system for the geometric features of the turbine runner, classify the turbine runner according to the order from datum features, main features to detailed features, and formulate accuracy evaluation indicators for each feature; among them, datum features include the mounting datum surface and positioning holes, main features include the inlet side profile and outlet side profile, and detailed features include the local curvature of the blade profile and surface roughness.

[0007] S2. Establish a multi-level progressive measurement strategy of "global-local-detail", including using global photogrammetry reference features, using laser tracking to measure main features, and using handheld scanners to measure detailed features;

[0008] S3. During the measurement process, real-time data stitching and registration are implemented, and measurement data at different levels are unified into the same coordinate system through feature point matching algorithms;

[0009] S4. Adjustment of measurement density based on feature level and real-time evaluation and supplementary measurement of measurement data.

[0010] In S1, the reference feature adopts the global accuracy evaluation index, the main feature adopts the key section error evaluation index, and the detail feature adopts the local curvature deviation evaluation index. The measurement accuracy of each feature is determined accordingly. The reference feature requires flatness ≤ 0.1 mm and positioning hole roundness ≤ 0.05 mm; the main feature requires contour ≤ 0.05 mm and continuity deviation ≤ 0.03 mm; the detail feature requires curvature deviation ≤ 0.025 mm and surface roughness Ra ≤ 3.2 μm.

[0011] In S2, the method for using global photogrammetric reference features is as follows:

[0012] A measurement coordinate system is established by uniformly arranging coded targets on the mounting reference surface of the rotary wheel, and a multi-view image matching algorithm is used to obtain the spatial position of the mounting reference surface and the positioning hole.

[0013] In S2, the method for measuring the main features using laser tracking is as follows:

[0014] Using a laser tracker, spatial point information of the entrance and exit side profiles is obtained by automatically tracking the reflector. A continuous scanning mode is used to ensure the integrity of the profiles, and multiple repeated measurements are used to improve data reliability.

[0015] In S2, the method for measuring detailed features using a handheld scanner is as follows:

[0016] The local curvature and surface roughness data of the blade profile are obtained by strip scanning, and the data integrity is ensured by multi-directional overlapping scanning.

[0017] In S4, circular point placement is used for the baseline features, contour tracking point placement is used for the main feature areas, and local densification point placement is used for the detailed feature areas.

[0018] The method of using a circular layout for reference features involves placing coded targets as control points around the mounting reference surface and positioning holes, and then uniformly distributing measurement points in a circle.

[0019] The method of implementing contour tracking for key feature areas is to set the starting point of the inlet and outlet contours at a distance of 50-100mm from the installation reference surface, and take a measurement point at every end along the contour line. In areas with a radius of curvature of less than 100mm, the point spacing is increased.

[0020] The method for implementing local densification of detailed feature areas is to place points at equal intervals on the blade surface, and then adjust the point density according to the curvature value of each area, and densify the points in areas where the curvature is greater than a set threshold.

[0021] In S4, the method for establishing real-time evaluation and supplementary measurement of measurement data is as follows:

[0022] By comparing the actual point cloud density distribution of each measurement area with the theoretical point layout requirements, the data integrity and measurement accuracy are evaluated. When the measurement quality is found to be substandard, the point layout strategy for the corresponding area is adjusted and supplementary measurements are performed until a complete turbine runner measurement model is obtained.

[0023] The present invention has the following beneficial effects:

[0024] This invention establishes a systematic geometric feature evaluation system by classifying and measuring the geometric features of the turbine runner according to their importance. Through feature classification and accuracy definition, it ensures the rational allocation of measurement resources.

[0025] This invention adopts a progressive measurement strategy of "global-local-detail" and significantly improves measurement efficiency and accuracy by complementing the advantages of different measurement methods.

[0026] This invention enables intelligent adjustment and real-time evaluation of measurement density, ensuring the integrity and reliability of measurement data. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Figure 1 This is a flowchart illustrating the implementation of the present invention.

[0029] Figure 2 This is a schematic diagram of the features of a water turbine runner.

[0030] Figure 3A schematic diagram showing the arrangement of coded targets on the mounting reference surface and positioning hole area of ​​the rotor.

[0031] Figure 4 This is a schematic diagram of a laser tracker measurement.

[0032] Figure 5 This is a schematic diagram showing the layout of points in the main feature areas.

[0033] Figure 6 A schematic diagram showing the placement of points in the detailed feature area. Detailed Implementation

[0034] The technical solution of the present invention will be described more clearly below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0035] See Figure 1 As shown, a hierarchical progressive geometric feature measurement method for a water turbine runner includes the following steps:

[0036] S1. Establish a hierarchical, progressive evaluation system for the geometric features of the turbine runner, classifying the turbine runner into levels from baseline features, main features to detailed features, and developing accuracy evaluation indicators for each feature. See [link to relevant documentation]. Figure 2 The datum features include the mounting datum surface and the positioning hole; the main features include the inlet side profile and the outlet side profile; and the detailed features include the local curvature of the blade profile and the surface roughness.

[0037] In S1, progressive accuracy evaluation standards are established for geometric features at different levels. The reference feature adopts the global accuracy evaluation index, the main feature adopts the key section error evaluation index, and the detail feature adopts the local curvature deviation evaluation index. The measurement accuracy of each feature is determined accordingly. Specifically, the reference feature requires flatness ≤ 0.1 mm and positioning hole roundness ≤ 0.05 mm; the main feature requires contour ≤ 0.05 mm and continuity deviation ≤ 0.03 mm; and the detail feature requires curvature deviation ≤ 0.025 mm and surface roughness Ra ≤ 3.2 μm.

[0038] S2. Establish a multi-level progressive measurement strategy of "global-local-detail", including using global photogrammetry reference features, using laser tracking to measure main features, and using handheld scanners to measure detailed features.

[0039] In S2, the method for using global photogrammetric reference features is as follows:

[0040] A measurement coordinate system is established by uniformly arranging coded targets on the mounting reference surface of the rotary wheel. A multi-view image matching algorithm is used to obtain the spatial position of the mounting reference surface and the positioning hole, thereby achieving high-precision measurement of the reference features and providing a unified spatial reference for subsequent measurements.

[0041] For details, see Figure 3 Using an industrial-grade camera and a 12mm wide-angle lens, coded targets are evenly distributed on the mounting reference surface and positioning hole area of ​​the rotating wheel. The industrial-grade camera has a resolution of 4096×3072 pixels. Eight measurement stations are used to complete 360° surround shooting, with each measurement station acquiring 15-20 images to ensure that each target is imaged in more than 3 images. A multi-view image matching algorithm is used to achieve a measurement accuracy of 0.1mm.

[0042] In S2, the method for measuring the main features using laser tracking is as follows:

[0043] Using a laser tracker, spatial point information of the entrance and exit side profiles is obtained by automatically tracking the reflector. A continuous scanning mode is used to ensure the integrity of the profiles, and multiple repeated measurements are used to improve data reliability.

[0044] For details, see Figure 4 A laser tracker with a measurement accuracy of ±15μm +6μm / m, along with a 0.5-inch spherical reflective prism, was used. The equipment was set up 2-3 meters away from the water turbine runner, employing continuous scanning mode with a scanning speed not exceeding 10mm / s to ensure the continuity and stability of data acquisition. Each contour was measured three times, and the average value was taken as the final result. Multiple measurement points were set around the runner using the laser tracker.

[0045] In S2, the method for measuring detailed features using a handheld scanner is as follows:

[0046] The local curvature and surface roughness data of the blade profile are acquired by strip scanning. Multi-directional overlapping scanning is used to ensure data integrity and achieve high-density acquisition of detailed features.

[0047] Specifically, a handheld 3D scanner was used to measure detailed features. A structured light scanner with a resolution of 0.025 mm was selected, achieving a single-scan accuracy of 0.025 mm. A cross-scanning method was employed to ensure an overlap rate of over 60% between adjacent zones. In areas with drastic curvature changes, the scanner distance was reduced to within 200 mm to improve local measurement accuracy.

[0048] S3. During the measurement process, real-time data stitching and registration are implemented, and the measurement data at different levels are unified into the same coordinate system through the feature point matching algorithm.

[0049] Specifically, feature point matching algorithms for key features such as targets and reflective spheres are used to unify measurement data at different levels into the same coordinate system, ensuring the consistency and integrity of the measurement data.

[0050] S4. Adjustment of measurement density based on feature level and real-time evaluation and supplementary measurement of measurement data.

[0051] In S4, a circular point layout is used for the reference features, a contour-tracking point layout is implemented for the main feature areas, and a locally denser point layout is implemented for the detailed feature areas to achieve accurate measurement of complex areas. Specifically, the main features adopt a progressive point layout with a base point spacing of 30mm and 15mm at curvature changes, while the detailed features adopt a denser point layout strategy with a base point spacing of 20mm and 5mm in high curvature areas.

[0052] Among them, see Figure 3 In this embodiment, coded targets are set up as control points around the reference surface and positioning holes, and a measurement point is arranged every 45° of the circumference to fully reflect the overall morphological features of the reference features.

[0053] join Figure 4 , 5 A contour-tracking point placement method is implemented for the main feature areas. In this embodiment, the starting point of the contour line is set at 50mm from the reference plane, and a measurement point is taken every 30mm along the contour line direction. In areas with a radius of curvature of less than 100mm, the point spacing is increased to 15mm. Through this progressive point placement strategy, approximately 100 measurement points are ultimately obtained at the entrance edge and approximately 85 measurement points are obtained at the exit edge, fully ensuring the continuity and accuracy of the contour features.

[0054] See Figure 6 This embodiment employs locally denser point placement for detailed feature areas. Points are placed at equal intervals on the blade surface, with a base point spacing of 20mm. The point density is then adjusted based on the curvature value of each region. For regions with curvature exceeding a set threshold, denser point placement is implemented, with a spacing of up to 5mm. This achieves high-precision measurement of complex surfaces, ensuring that the curvature deviation of detailed features is ≤0.025mm.

[0055] In S4, the method for establishing real-time evaluation and supplementary measurement of measurement data is as follows:

[0056] This embodiment evaluates data integrity and measurement accuracy by comparing the actual point cloud density distribution of each measurement area with the theoretical point layout requirements. When the measurement quality is found to be substandard, the point layout strategy of the corresponding area is adjusted and supplementary measurements are performed until a complete turbine runner measurement model is obtained.

[0057] The method of this invention has been practically applied in the maintenance of turbines at a large hydropower station. Practice has proven that this method can improve the combined efficiency and accuracy of measuring the geometric characteristics of the turbine runner by more than 10%. By establishing a systematic measurement system and adopting advanced measurement methods, the quality of hydropower unit maintenance has been significantly improved, demonstrating significant engineering application value.

Claims

1. A method of measuring geometric features of a water turbine runner by hierarchical progression, characterized in that, The method comprises the following steps: S1, a geometric feature hierarchical progressive evaluation system of a water turbine runner is established, the water turbine runner is graded according to the order from a reference feature, a main feature to a detail feature, and precision evaluation indexes are formulated for each feature; wherein the reference feature comprises an installation reference surface and a positioning hole, the main feature comprises an inlet edge contour and an outlet edge contour, and the detail feature comprises a local curvature of a blade profile and surface roughness; S2, a multi-level progressive measurement strategy of "global-local-detail" is established, which comprises adopting global photogrammetry to measure the reference feature, adopting laser tracking to measure the main feature, and adopting a handheld scanner to measure the detail feature; S3, data real-time splicing and registration are implemented in the measurement process, and different levels of measurement data are unified to the same coordinate system through a feature point matching algorithm; S4, measurement density adjustment based on feature levels and real-time evaluation and supplementary measurement of measurement data are implemented; In S4, the reference feature is measured by adopting circumferential point arrangement, the main feature region is measured by adopting contour tracking point arrangement, and the detail feature region is measured by adopting local encryption point arrangement.

2. The method of claim 1, wherein: In S1, the reference feature adopts a global precision evaluation index, the main feature adopts a key section error evaluation index, and the detail feature adopts a local curvature deviation evaluation index, and the measurement precision of each feature is determined accordingly, wherein the reference feature requires that the flatness is less than or equal to 0.1 mm, and the positioning hole roundness is less than or equal to 0.05 mm; the main feature requires that the contour degree is less than or equal to 0.05 mm, and the continuity deviation is less than or equal to 0.03 mm; and the detail feature requires that the curvature deviation is less than or equal to 0.025 mm, and the surface roughness Ra is less than or equal to 3.2 μm.

3. The method of claim 1, wherein: In S2, the method for measuring the reference feature by adopting global photogrammetry is as follows: A measurement coordinate system is established by uniformly arranging coded targets on the installation reference surface of the runner, and a multi-view image matching algorithm is adopted to obtain the spatial positions of the installation reference surface and the positioning hole.

4. The method of claim 1, wherein: In S2, the method for measuring the main feature by adopting laser tracking is as follows: A laser tracker is used to obtain the spatial point position information of the inlet edge contour and the outlet edge contour by automatically tracking a reflector, a continuous scanning mode is adopted to ensure the integrity of the contour, and the data reliability is improved through multiple repeated measurements.

5. The method of claim 1, wherein: In S2, the method for measuring the detail feature by adopting a handheld scanner is as follows: A strip scanning mode is adopted to obtain the local curvature and surface roughness data of the blade profile, and the data integrity is ensured through multi-directional overlapping scanning.

6. The method of claim 1, wherein: The method for adopting circumferential point arrangement for the reference feature is that coded targets are arranged as control points around the installation reference surface and the positioning hole, and the measurement points are arranged uniformly in a circle.

7. The method of claim 1, wherein: The method for implementing contour tracking point arrangement for the main feature region is that the starting points of the inlet edge contour and the outlet edge contour are arranged at a distance of 50-100 mm from the installation reference surface, a measurement point is arranged at every interval along the contour line, and the point distance is encrypted in the region with a curvature radius less than 100 mm.

8. The method of claim 1, wherein: The method for implementing local encryption point arrangement for the detail feature region is that the blade profile is arranged with equidistance points, and then the point arrangement density is adjusted according to the curvature value of each region, and the point arrangement density is encrypted in the region with a curvature greater than a set threshold value.

9. The method of claim 1, wherein: In S4, the method for establishing real-time evaluation and supplementary measurement of measurement data is as follows: By comparing the actual point cloud density distribution of each measurement area with the theoretical distribution, the data integrity and measurement accuracy are evaluated. When the measurement quality is found to be substandard, the corresponding area's distribution strategy is adjusted, and supplementary measurements are conducted until a complete water turbine runner measurement model is obtained.

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