Method and device for measuring blade tip clearance of moving blade of gas compressor

Abstract

The invention provides a gas compressor moving blade tip clearance measuring method and device, and belongs to the field of aero-gas turbine gas compressors. The problems of low measurement precision, low measurement efficiency and small measurement range in the prior art are solved. The method comprises the following steps that an angle encoder is installed on a main shaft, and a three-dimensional laser profile measuring instrument is arranged on the blade tip side of a blade at intervals; the impeller is rotated, the three-dimensional laser profile measuring instrument scans the blade tip, and three-dimensional point cloud data of the whole circle of blade tip profile are obtained; after the casing and the impeller are assembled, a plurality of continuous blades on the impeller are detached, and the three-dimensional laser profile measuring instrument is arranged at the vacant position of the impeller; the impeller is rotated, the three-dimensional laser profile measuring instrument scans the inner wall of the casing, and three-dimensional point cloud data of the whole circle of the inner wall of the casing are obtained; processing data; registering the processed three-dimensional point cloud data of the blade tip contour and the processed three-dimensional point cloud data of the inner wall in the same coordinate system to form a registration model; and the blade tip clearance value of the whole circle is calculated. The method is mainly used for measuring the blade tip clearance.

Description

Technical Field

[0001] The invention belongs to the field of aviation gas turbine compressors, and in particular relates to a method and a device for measuring the tip clearance of compressor moving blades. Background Art

[0002] As one of the three major components of a gas turbine, the performance of the compressor is directly related to the overall life and performance of the engine. The distance between the inner wall of the compressor casing and the top of the blade rotor is called the tip clearance, which is an important parameter affecting the performance of the gas turbine. The compressor contains multi-stage blades, with a compact structure and curved surfaces at both ends of the tip clearance, which brings challenges to the measurement of the tip clearance. Common methods for measuring tip clearance after assembly include the plasticine method, the lead wire measurement method, and the feeler gauge measurement method.

[0003] The above methods have large errors in manual measurement, low measurement efficiency and accuracy, and poor intelligence. At the same time, the above methods cannot obtain the tip clearance value of the entire circle during the measurement process, which in turn affects the accuracy and efficiency of compressor performance evaluation, maintenance strategy formulation, and technical improvement.

[0004] In summary, a method and device for measuring the tip clearance of compressor rotor blades are proposed. Summary of the invention

[0005] In view of this, the present invention aims to provide a method and device for measuring the tip clearance of compressor moving blades, so as to solve the problems of low measurement accuracy, low measurement efficiency and small measurement range in the prior art.

[0006] To achieve the above object, the present invention adopts the following technical solution. According to one aspect of the present invention, a method for measuring the tip clearance of a compressor rotor blade is provided, comprising the following steps:

[0007] S1. An angle encoder is installed on the main shaft to measure the angle information of the impeller, and a three-dimensional laser profile measuring instrument is set in the air on the tip side of the blade;

[0008] S2, rotating the impeller, and scanning the blade tip with a three-dimensional laser profile measuring instrument to obtain three-dimensional point cloud data of the entire blade tip profile;

[0009] S3. After assembling the casing and the impeller, remove several consecutive blades on the impeller and set the three-dimensional laser profile measuring instrument at the empty position of the impeller;

[0010] S4, rotating the impeller at a certain speed, and scanning the inner wall of the casing with a 3D laser profile measuring instrument to obtain 3D point cloud data of the inner wall of the casing in a whole circle;

[0011] S5, data processing, filtering, signal amplification, data fusion and data coordinate conversion processing of the three-dimensional point cloud data of the blade tip profile obtained in S2 and the three-dimensional point cloud data of the inner wall obtained in S4;

[0012] S6. By calibration, registering the processed three-dimensional point cloud data of the blade tip profile and the three-dimensional point cloud data of the inner wall in the same coordinate system to form a registration model;

[0013] S7. Visualize the registration model to display the relative position of the blade tip and the inner wall of the casing, and calculate the tip clearance value of the entire circle.

[0014] Furthermore, in S3, three consecutive blades on the impeller are removed.

[0015] Furthermore, in S5, the data fusion is to fit the angle data measured by the angle encoder to generate a curve, and correspond the measurement timestamp of each three-dimensional laser profilometer to the curve to obtain the relationship between the angle change and time, thereby realizing time alignment.

[0016] Furthermore, the polynomial for obtaining the relationship between the angle and time is:

[0017] θ(t)=a 0 +a 1 t+a 2 t 2 +…+a n t n

[0018] Among them, a can be obtained by the least squares method 0 ,a 1 …a n value, and the measurement time t of the 3D laser profile measuring instrument j Substituting into the above formula, the corresponding angle value is calculated. Each measurement of the 3D laser scanning measurement sensor can find the corresponding angle value θ on the fitting curve. j , thus achieving time alignment.

[0019] Furthermore, according to the spatial position relationship between the three-dimensional laser profilometer and the main axis, the fused data with angle information is converted into coordinates, and the processed blade tip and casing point cloud data are aligned in the same coordinate system through calibration to form a registration model.

[0020] Furthermore, in S6, the point cloud data registration includes two steps: coarse registration and fine registration.

[0021] Furthermore, the coarse registration comprises the following steps:

[0022] Establish the coordinate system, the measured impeller coordinate system σ o =[O o ;x o ,y o ,z o ]; measure the light coordinate system σ l =[O l ;x l ,y l ,z l ]; 3D laser profile measuring instrument coordinate system σ s =

[0023] [O s ;x s ,y s ,z s ];

[0024] In the measurement light coordinate system σ l The impeller point cloud coordinates obtained by the 3D laser profiler are P l , P l =[x l ,y l ,0,1] T ; According to the measurement light coordinate system σ l With 3D laser profilometer s The spatial position relationship of and translation matrix The point cloud data P of the impeller l Transform to coordinate system σ s The impeller point cloud coordinates are transformed into P s ,

[0025] Where P l =[x s ,y s ,z s ,1] T

[0026]

[0027]

[0028] where q s is the installation parameter of the 3D laser profiler, the value is +1 for normal installation or -1 for reverse installation, h 0 is the reference distance of the sensor; according to the coordinate system σ s With the impeller coordinate system σ o The spatial position relationship between them is used to establish the rotation matrix and translation matrix During measurement, the impeller rotates with the main shaft, and the rotation angle is is the angle value θ obtained based on time registration j Calculate the rotation angle; establish the rotation matrix R during measurement 1 , the point cloud coordinates P s Transform to impeller coordinate system σ o The impeller rotates at an angle of After that, the point cloud coordinates of the impeller are P o , which can be expressed as:

[0029]

[0030] Where P o =[x o ,y o ,z o ,1] T

[0031]

[0032]

[0033]

[0034] Among them, the subscripts δ, θ, They represent the spatial attitude angle ω of the 3D laser profilometer respectively. δ ,ω θ , C and S represent cos() and sin() respectively, such as a o 、b o 、c o They are the tangential, radial and axial offset distances of the three-dimensional laser profile measuring instrument relative to the impeller being measured;

[0035] It can be concluded that:

[0036] Similarly, the point cloud measurement of the inner wall of the casing is converted to the impeller coordinate system σ o In the impeller coordinate system σ o The point cloud coordinates of the inner wall of the casing are Q o , which can be expressed as:

[0037]

[0038] Among them, Q l For l Point cloud of the inner wall of the casing in the coordinate system; and is the coordinate system σ l With σ sThe rotation matrix and translation matrix under the spatial position relationship, and is the coordinate system σ o With σ s The rotation matrix and translation matrix under the spatial position relationship, the rotation matrix during measurement is R 2 .

[0039] Furthermore, the precise registration comprises the following steps:

[0040] For the point cloud {P o} and {Q o}, calculate the normal vector of each point separately, for point p i ∈{P o}, fit a plane in its neighborhood, the normal vector is the eigenvector corresponding to the minimum eigenvalue of the plane, and the neighborhood point set is:

[0041] N(p i )={p j |||p j -p i ||<∈}

[0042] Where ∈ is the neighborhood radius and the covariance matrix is:

[0043]

[0044] The eigenvalue decomposition is: C = UΛU T

[0045] Among them, Λ is a diagonal matrix, U is the eigenvector matrix, and the eigenvector corresponding to the minimum eigenvalue is the normal vector Normalize the normal vector:

[0046]

[0047] For every point p i ∈{P o}, find its nearest neighbor point q in the point cloud Q i , only matching point pairs whose normal vector angle is less than a certain threshold are retained:

[0048]

[0049] Among them, θ max is the preset normal vector angle threshold. If it is not less than θ max , then reselect the matching point pairs and use them as constraints to perform precise registration of the two point clouds.

[0050] According to another aspect of the present invention, a compressor moving blade tip clearance measuring device is provided, using a compressor moving blade tip clearance measuring method, comprising:

[0051] An angle encoder, arranged on the main shaft;

[0052] The measuring instrument fixing fixture has one side connected to the impeller and the other side used to connect to the 3D laser profile measuring instrument when measuring the inner wall of the casing;

[0053] A three-axis mobile platform, when measuring the tip of a blade, used to support and adjust the position of the three-dimensional laser profile measuring instrument relative to the tip of the blade;

[0054] The controller is connected to the angle encoder and the computer, and is used to provide a communication library for acquiring images, a measurement library for contour measurement, interference removal, image synthesis and other functions, and a display library for intuitive scanning results.

[0055] Furthermore, the measuring instrument fixing fixture has the same blade root type as the blade and can be directly assembled with the impeller.

[0056] Beneficial effects:

[0057] 1. A blade tip clearance measurement method that combines 3D laser measurement technology with an angle encoder. Through precise data fusion and coordinate conversion, point cloud reconstruction with spatial relationships between the casing inner wall profile and the blade tip profile can be achieved. This method overcomes the limitations of traditional measurement methods and achieves high-precision and high-efficiency blade tip clearance measurement;

[0058] 2. Implementation of the blade tip clearance measurement system. Before the impeller and casing are assembled, a three-dimensional laser profile measuring instrument is installed on a three-axis mobile platform to rotate the impeller to measure the blade tip profile. The angle encoder records and feeds back the rotation angle data in real time to ensure the accuracy and integrity of the measurement results. The system design avoids opening holes in the casing, protects the aerodynamic shape of the casing, and achieves high-precision measurement of the blade tip profile;

[0059] 3. Remove the three blades and install the 3D laser profiler through a special measuring instrument fixture for measurement. This method ensures that the measurement results reflect the tip clearance in the actual assembly state and avoids the influence of assembly errors. The system design improves measurement efficiency and accuracy, and provides strong support for the performance evaluation and maintenance strategy formulation of rotating machinery;

[0060] 4. Data fusion time registration method: fit the angle data measured by the angle encoder to generate a curve, and correspond the measurement timestamp of each 3D laser profiler to the curve to obtain the relationship between the angle and time, and realize time registration, that is, realize precise fusion. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0062] Figure 1 This is a flow chart of a compressor rotor blade tip clearance measurement method according to the present invention;

[0063] Figure 2 It is a structural schematic diagram of a schematic diagram of an application of a positioning and timing system of a compressor rotor blade tip clearance measurement method according to the present invention;

[0064] Figure 3 A schematic diagram of sensor synchronous triggering comparison of a compressor rotor blade tip clearance measurement method according to the present invention without synchronous triggering;

[0065] Figure 4 This is a schematic diagram of multi-sensor synchronous triggering comparison of a compressor rotor blade tip clearance measurement method according to the present invention. After synchronous triggering;

[0066] Figure 5 This is a time registration effect diagram of a compressor rotor blade tip clearance measurement method according to the present invention;

[0067] Figure 6 A schematic diagram of the position relationship of blade tip profile measurement in a method for measuring blade tip clearance of a compressor rotor blade according to the present invention;

[0068] Figure 7 A schematic diagram of the position relationship of the casing inner wall profile measurement of a compressor blade tip clearance measurement method according to the present invention;

[0069] Figure 8 A schematic diagram of the normal vector distribution of the inner wall profile of a casing in a method for measuring the tip clearance of a compressor rotor blade according to the present invention;

[0070] Fig. 9 A schematic diagram of the normal vector distribution of the blade tip profile of a compressor rotor blade tip clearance measurement method according to the present invention;

[0071] Fig.10 A schematic diagram of a blade tip profile point cloud scanning system of a compressor rotor blade tip clearance measuring device according to the present invention;

[0072] Fig.11 A schematic diagram of a point cloud scanning system for the inner wall contour of a compressor blade tip clearance measuring device according to the present invention;

[0073] Fig.12It is a structural schematic diagram of a measuring instrument fixing fixture of a compressor rotor blade tip clearance measuring device according to the present invention;

[0074] Fig.13 The present invention is a schematic diagram showing the principle of a three-dimensional laser profilometer for measuring the tip clearance of compressor rotor blades.

[0075] In the figure: a three-dimensional laser profile measuring instrument 1; a measuring instrument fixing fixture 2; a blade root type 201; a fixed leaf plate 202; a fixing screw 203; a three-axis moving platform 3; an angle encoder 4; a controller 5; a computer 6; a blade 7; an impeller 8; a main shaft 9; a casing 10; and a positioning and timing system 11. DETAILED DESCRIPTION

[0076] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely explain the technical solutions in the embodiments of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict, and the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0077] It should be noted that the descriptions of the present invention regarding directions such as "left", "right", "left side", "right side", "upper", "lower", "top", and "bottom" are all defined based on the relationship between the orientations or positions shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the structure must be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention. In the description of the present invention, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0078] In the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0079] Embodiment 1:

[0080] See attached Figure 1 The present embodiment provides a method for measuring the tip clearance of a compressor rotor blade, comprising the following steps:

[0081] S1. An angle encoder 4 is installed on the main shaft 9 to measure the angle information of the impeller 8. A three-dimensional laser profile measuring instrument 1 is arranged in the air on the tip side of the blade 7;

[0082] S2, rotating the impeller 8, and scanning the blade tip with a three-dimensional laser profile measuring instrument 1 to obtain three-dimensional point cloud data of the entire blade tip profile;

[0083] S3, after assembling the casing 10 and the impeller 8, remove a number of continuous blades 7 on the impeller 8, and set the three-dimensional laser profile measuring instrument 1 at the empty position of the impeller 8;

[0084] S4, rotating the impeller 8 at a certain speed, and the three-dimensional laser profile measuring instrument 1 scanning the inner wall of the casing 10 to obtain the three-dimensional point cloud data of the inner wall of the entire circle of the casing 10;

[0085] S5, data processing, filtering, signal amplification, data fusion and data coordinate conversion processing of the three-dimensional point cloud data of the blade tip profile obtained in S2 and the three-dimensional point cloud data of the inner wall obtained in S4;

[0086] S6. By calibration, registering the processed three-dimensional point cloud data of the blade tip profile and the three-dimensional point cloud data of the inner wall in the same coordinate system to form a registration model;

[0087] S7. Visually display the registration model to show the relative position of the tip of the blade 7 and the inner wall of the casing 10, and calculate the tip clearance value of the entire circle.

[0088] Among them, step S2 needs to be performed before the casing 10 and the impeller 8 are transferred. The three-dimensional laser profile measuring instrument 1 is installed on the three-axis mobile platform 3, and the three-axis mobile platform 3 is adjusted to a suitable distance so that it can scan the tip of the rotating blade 7 and obtain the three-dimensional point cloud data of the entire circle of the tip profile. Step S4 needs to be performed after the casing 10 and the impeller 8 are assembled. Considering the reasons such as the dead weight of the rotor, the measurement is performed after the assembly is completed to ensure that the measurement results reflect the tip clearance in the actual assembly state. The impeller 8 needs to rotate at a low speed; some errors may be introduced during the assembly process, such as the centering error and installation deviation of the impeller 8 and the casing 10. Measuring after the assembly is completed can avoid the influence of these assembly errors on the measurement results and ensure the accuracy of the measurement results; measuring after the assembly is completed can obtain all necessary data at one time, avoid repeated operations and multiple disassembly and assembly, and improve measurement efficiency.

[0089] In this embodiment, in S3, three consecutive blades 7 on the impeller 8 are removed to make room for installing a three-dimensional laser profiler. A three-dimensional laser profiler 1 is installed on the removed space so that it can scan the inner wall of the casing 10. The impeller 8 is rotated at a low speed, and the three-dimensional laser profiler 1 rotates with the impeller 8 to obtain three-dimensional point cloud data of the inner wall of the entire casing.

[0090] In the point cloud scanning system of the inner wall contour of the casing, the clock references used by the three-dimensional laser contour measuring instrument and the angle encoder are different. In order to ensure that the data collected by each sensor can accurately correspond to the same time, it is necessary to ensure that they use the same clock source. Since clock sources generally have clock drift, and the clock drift characteristics of each clock source are different, even if the timestamps of each sensor are aligned at the initial moment, the effect of the previous alignment will gradually deviate with the passage of time. Based on the above problems, the timestamp synchronization method chooses to use the positioning and timing system 11, which is composed of a global navigation satellite sensor. It has its own second pulse generator, which can synchronously trigger all sensors. The application of the positioning and timing system 11 in the measurement system is as follows: Figure 2 .

[0091] During each triggering process, the sensor will calibrate its own clock, thereby effectively eliminating the accumulated error of the clock source. In this way, it can ensure that each sensor can maintain accurate time synchronization during long-term operation. Figure 3 and Figure 4 .

[0092] This timestamp synchronization method not only ensures the alignment of timestamps of each sensor at the initial moment, but also corrects the clock during each triggering process, which can effectively eliminate the error caused by clock drift.

[0093] In this embodiment, if Figure 5 As shown, in S5, the data fusion is to fit the angle data measured by the angle encoder 4 to generate a curve, and correspond the measurement timestamp of each three-dimensional laser profile measuring instrument 1 to the curve to obtain the relationship between the angle change and time, thereby realizing time alignment.

[0094] The purpose of time alignment is to ensure that the data measured by the two sensors at the same time point can correspond to each other, so as to achieve data fusion. In order to verify the universality of the time alignment method, the frequencies of the two sensors should not be multiples. 36Hz and 20Hz represent the common sampling frequencies of 3D laser profilers and angle encoders in practical applications, which can effectively simulate the frequency differences in practical applications. The measurement frequency of the 3D laser profiler is 36Hz. Its measurement data is determined by the inner wall of the casing, which is random and nonlinear. The measurement frequency of the angle encoder is 20Hz, and the angle data it measures changes linearly and is only affected by speed and rotational acceleration.

[0095] Since the data measured by the angle encoder changes linearly, the angle data measured by the angle encoder is fitted to generate a curve. Suppose the data measured by the angle encoder is where θ i is the angle value measured at the i-th time, ti is the corresponding timestamp.

[0096] In this embodiment, the polynomial for obtaining the relationship between the angle and time is:

[0097] θ(t)=a 0 +a 1 t+a 2 t 2 +…+a n t n

[0098] Among them, a can be obtained by the least squares method 0 ,a 1 …a n value, each measurement time t of the three-dimensional laser profile measuring instrument 1 j Substituting into the above formula, the corresponding angle value is calculated. Each measurement of the 3D laser scanning measurement sensor can find the corresponding angle value θ on the fitting curve. j , thus achieving time alignment.

[0099] In this embodiment, according to the spatial position relationship between the three-dimensional laser profilometer 1 and the main shaft 9, the fused data with angle information is converted into coordinates, and the processed blade tip and casing point cloud data are aligned in the same coordinate system through calibration to form a registration model.

[0100] In this embodiment, in S6, the point cloud data registration includes two steps: coarse registration and fine registration.

[0101] Point cloud registration technology is a process of spatial transformation of two point clouds in two different coordinate systems, and finally aligning the two point clouds to the same coordinate system. Coarse registration and fine registration are two consecutive steps in the point cloud registration process. Coarse registration provides a good initial condition for fine registration, and the fine registration criterion further optimizes the registration accuracy based on the result of coarse registration.

[0102] Traditional point cloud registration methods, such as the ICP point cloud fine registration algorithm, usually rely on the overlapping area between point clouds and achieve alignment by matching the features of the overlapping parts. However, in the tip clearance measurement, there is no overlap between the tip point cloud and the casing inner wall point cloud. In this application environment, the goal of point cloud registration is not to make the two point clouds completely overlap, but to restore the actual tip clearance through registration. Therefore, a coarse registration method based on the spatial relationship between the sensor and the axis is proposed, combined with a fine registration algorithm based on normal vector features to achieve high-precision point cloud registration.

[0103] By using the spatial position of the sensor and the axis to perform coordinate transformation to achieve rough registration, the point cloud is quickly aligned; then the registration accuracy is further optimized by matching the normal vector angle of the point pair to be less than a preset threshold. This method not only solves the problem of no overlap between the two point clouds, but also improves the accuracy and robustness of the registration, which is particularly suitable for complex scenarios such as high-precision alignment of gas turbine tip clearance measurement.

[0104] In this embodiment, if Figure 6 and 7 As shown, the coarse registration includes the following steps:

[0105] Establish the coordinate system, the measured impeller coordinate system σ o =[O o ;x o ,y o ,z o ]; measure the light coordinate system σ l =[O l ;x l ,y l ,z l ]; 3D laser profile measuring instrument coordinate system σ s =

[0106] [O s ;x s ,y s ,z s ]; 3D laser profile measuring instrument coordinate system σ s is a fixed coordinate system. The impeller is fixedly connected to the main shaft and rotates with it. The impeller coordinate system σ o is the moving coordinate system, where x of the impeller coordinate system is o The shaft coincides with the center axis of the impeller, and the origin of the coordinate system of the 3D laser profiler is O s Located at the center of the outgoing laser line, plane X s O s Y s Coplanar with the emitting light plane of the 3D laser profilometer.

[0107] In the measurement light coordinate system σ l In this case, the impeller point cloud coordinates obtained by the 3D laser profile measuring instrument 1 are P l , P l =[x l ,y l ,0,1] T ; According to the measurement light coordinate system σ l With 3D laser profilometer s The spatial position relationship of and translation matrix The point cloud data P of the impeller lTransform to coordinate system σ s The impeller point cloud coordinates are transformed into P s ,

[0108] Where P l =[x s ,y s ,z s ,1] T

[0109]

[0110]

[0111] where q s is the installation parameter of the 3D laser profile measuring instrument 1, the value is +1 for normal installation or -1 for reverse installation, h 0 is the reference distance of the sensor; according to the coordinate system σ s With the impeller coordinate system σ o The spatial position relationship between them is used to establish the rotation matrix and translation matrix During measurement, the impeller 8 rotates with the main shaft, and the rotation angle is is the angle value θ obtained based on time registration j Calculate the rotation angle; establish the rotation matrix R during measurement 1 , the point cloud coordinates P s Transform to impeller coordinate system σ o The impeller rotates at an angle of After that, the point cloud coordinates of the impeller are P o , which can be expressed as:

[0112]

[0113] Where P o =[x o ,y o ,z o ,1] T

[0114]

[0115]

[0116]

[0117] Among them, the subscripts δ, θ, They represent the spatial attitude angle ω of the 3D laser profilometer respectively. δ ,ω θ , C and S represent cos() and sin() respectively, such as a o 、b o 、c o They are the tangential, radial and axial offset distances of the three-dimensional laser profile measuring instrument relative to the impeller being measured;

[0118] It can be concluded that:

[0119] Similarly, the point cloud measurement of the inner wall of the casing 10 is converted to the impeller coordinate system σ o In the impeller coordinate system σ o The point cloud coordinates of the inner wall of the casing are Q o , which can be expressed as:

[0120]

[0121] Among them, Q l For l Point cloud of the inner wall of the casing in the coordinate system; and is the coordinate system σ l With σ s The rotation matrix and translation matrix under the spatial position relationship, and is the coordinate system σ o With σ s The rotation matrix and translation matrix under the spatial position relationship, the rotation matrix during measurement is R 2 .

[0122] In this embodiment, if Figure 8 and 9 As shown, the precise registration comprises the following steps:

[0123] For the point cloud {P o} and {Q o}, calculate the normal vector of each point separately, for point p i ∈{P o}, fit a plane in its neighborhood, the normal vector n pi is the eigenvector corresponding to the minimum eigenvalue of the plane, and the neighborhood point set is:

[0124] N(p i )={p j |||p j -p i ||<∈}

[0125] Where ∈ is the neighborhood radius and the covariance matrix is:

[0126]

[0127] The eigenvalue decomposition is: C = UΛU T

[0128] Among them, Λ is a diagonal matrix, U is the eigenvector matrix, and the eigenvector corresponding to the minimum eigenvalue is the normal vector n pi , normalize the normal vector:

[0129]

[0130] For every point p i ∈{P o}, find its nearest neighbor point q in the point cloud Q i , only matching point pairs whose normal vector angle is less than a certain threshold are retained:

[0131]

[0132] Among them, θ max is the preset normal vector angle threshold. If it is not less than θ max , then reselect the matching point pairs and use them as constraints to perform precise registration of the two point clouds.

[0133] Embodiment 2:

[0134] A compressor rotor blade tip clearance measuring device, an angle encoder 4, arranged on a main shaft 9;

[0135] A measuring instrument fixing fixture 2, one side of which is connected to the impeller 8, and the other side is used to connect the three-dimensional laser profile measuring instrument 1 when measuring the inner wall of the casing 10;

[0136] A three-axis mobile platform 3, used to support and adjust the position of the three-dimensional laser profile measuring instrument 1 relative to the blade tip when measuring the blade tip of the blade 7;

[0137] The controller 5 is connected to the angle encoder 4 and the computer 6, and is used to provide a communication library for acquiring images and a measurement library for contour measurement, interference removal, image synthesis and other functions, as well as a display library for intuitive scanning results.

[0138] like Fig.10 As shown, the three-axis mobile platform 3 is used to adjust the distance between the three-dimensional laser profile measuring instrument 1 and the tip of the blade 7. During measurement, the impeller 8 is rotated, and the three-dimensional laser profile measuring instrument 1 scans the tip of the blade 7, thereby accurately capturing the point cloud information. At the same time, the angle encoder 4 is installed on the main shaft 9 to record and feedback the rotation angle data in real time to ensure the accuracy and integrity of the measurement results.

[0139] like Fig.11As shown, after the casing 10 and the impeller 8 are assembled, due to the space size constraints, the three blades on the impeller 8 need to be removed to make room for the installation of the 3D laser profile measuring instrument 1. Subsequently, the 3D laser profile measuring instrument 1 and the impeller 8 are tightly fixed by a special measuring instrument fixing fixture 2. During the measurement process, the 3D laser profile measuring instrument 1 will dynamically scan the inner wall of the casing 10 as the impeller 8 rotates, thereby accurately capturing the point cloud information.

[0140] In this embodiment, if Fig.12 As shown, the measuring instrument fixing fixture 2 has the same blade root form 201 as the blade 7 and can be directly assembled with the impeller 8. The fixed leaf plate 202 is vertically fixed on the plane of the blade root form 201 away from the impeller 8 side, and the three-dimensional laser profile measuring instrument 1 is installed on the fixed leaf plate 202 by fixing screws 203.

[0141] like Fig.13 As shown in the figure, three-dimensional laser measurement often uses line laser or surface laser as the incident light source, and outputs the measurement results in the form of three-coordinate point sets, which can quickly reconstruct the measured object and reversely restore the spatial surface information of the measured object. It can achieve the reconstruction of complex surfaces with large curvature such as casings and blades. The structure of the scanning three-dimensional laser profile measuring instrument is mainly composed of a laser transmitter, a cylindrical objective lens, a receiving objective lens, an internal processor, and a camera sensor. Figure 3 The measurement principle of the 3D laser profile measuring instrument is as follows: the laser transmitter emits a laser beam, which is diffused into a linear laser light knife through a cylindrical objective lens; after the line laser reaches the surface of the object to be measured, diffuse reflection occurs; the reflected beam is received by the receiving lens group and projected onto the camera sensor to form an image of the object to be measured; the internal processor measures the displacement and shape of the object to be measured by detecting changes in position and shape.

[0142] The embodiments of the present invention disclosed above are only used to help illustrate the present invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. According to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well.

Claims

1. A method for measuring the tip clearance of a compressor rotor blade, characterized in that: The following steps are involved: S1, installing an angle encoder (4) on the main shaft (9) for measuring the angle information of the impeller (8), and setting a three-dimensional laser profile measuring instrument (1) in the air on the tip side of the blade (7); S2, rotating the impeller (8), and scanning the blade tip with a three-dimensional laser profile measuring instrument (1) to obtain three-dimensional point cloud data of the entire blade tip profile; S3, after assembling the casing (10) and the impeller (8), removing a plurality of continuous blades (7) on the impeller (8), and setting the three-dimensional laser profile measuring instrument (1) at an empty position of the impeller (8); S4, rotating the impeller (8) at a certain speed, and scanning the inner wall of the casing (10) with a three-dimensional laser profile measuring instrument (1), to obtain three-dimensional point cloud data of the inner wall of the casing (10) around a whole circle; S5, data processing, filtering, signal amplification, data fusion and data coordinate conversion processing of the three-dimensional point cloud data of the blade tip profile obtained in S2 and the three-dimensional point cloud data of the inner wall obtained in S4; S6. By calibration, registering the processed three-dimensional point cloud data of the blade tip profile and the three-dimensional point cloud data of the inner wall in the same coordinate system to form a registration model; S7. Visually display the registration model to show the relative position of the tip of the blade (7) and the inner wall of the casing (10), and calculate the tip clearance value of the entire circle.

2. A compressor rotor blade tip clearance measurement method according to claim 1, characterized in that: In S3, three consecutive blades (7) on the impeller (8) are removed.

3. The method for measuring the tip clearance of a compressor rotor blade according to claim 1, characterized in that: In S5, the data fusion is to fit the angle data measured by the angle encoder (4) to generate a curve, and correspond the measurement timestamp of each three-dimensional laser profile measuring instrument (1) to the curve to obtain the relationship between the angle and time, thereby achieving time alignment.

4. The method for measuring the tip clearance of a compressor rotor blade according to claim 3, characterized in that: The polynomial for obtaining the relationship between the angle and time is: θ(t)=a0+a1t+a2t 2 +…+a n t n Among them, a0, a1…a can be obtained by the least squares method. n The measurement time t of the three-dimensional laser profile measuring instrument (1) is j Substituting into the above formula, the corresponding angle value is calculated. Each measurement of the 3D laser scanning measurement sensor can find the corresponding angle value θ on the fitting curve. j , thus achieving time alignment.

5. The method for measuring the tip clearance of a compressor rotor blade according to claim 3, characterized in that: According to the spatial position relationship between the three-dimensional laser profile measuring instrument (1) and the main axis (9), the fused data with angle information is subjected to coordinate transformation, and the processed blade tip and casing point cloud data are aligned in the same coordinate system through calibration to form an alignment model.

6. The method for measuring the tip clearance of a compressor rotor blade according to claim 1, characterized in that: In S6, the point cloud data registration includes two steps: coarse registration and fine registration.

7. The method for measuring the tip clearance of compressor rotor blades according to claim 6, characterized in that: The coarse registration comprises the following steps: Establish the coordinate system, the measured impeller coordinate system σ o =[O o ;x o ,y o ,z o ]; measure the light coordinate system σ l =[O l ;x l ,y l ,z l ]; 3D laser profile measuring instrument coordinate system σ s = [O s ;x s ,y s ,z s ]; In the measurement light coordinate system σ l The impeller point cloud coordinates obtained by the 3D laser profile measuring instrument (1) are P l , P l =[x l ,y l ,0,1] T ; According to the measurement light coordinate system σ l With 3D laser profile measuring instrument s The spatial position relationship of and translation matrix The point cloud data P of the impeller l Transform to coordinate system σ s The impeller point cloud coordinates are transformed into P s , Where P l =[x s ,y s ,z s ,1] T where q s is the installation parameter of the 3D laser profiler (1), with the value of +1 for normal installation or -1 for reverse installation, h0 is the reference distance of the sensor; according to the coordinate system σ s With the impeller coordinate system σ o The spatial position relationship between them is used to establish the rotation matrix and translation matrix During measurement, the impeller (8) rotates along with the main shaft, and the rotation angle is is the angle value θ obtained based on time registration j The calculated rotation angle; establish the rotation matrix R1 during measurement, and transform the point cloud coordinates P s Transform to impeller coordinate system σ o The impeller rotates at an angle of After that, the point cloud coordinates of the impeller are P o , which can be expressed as: In the formula P o =[x o ,y o ,z o ,1] T Among them, the subscripts δ, θ, They represent the spatial attitude angle ω of the 3D laser profilometer respectively. δ ,ω θ , C and S represent cos() and sin() respectively, such as a o , b o 、c o They are the tangential, radial and axial offset distances of the three-dimensional laser profile measuring instrument relative to the impeller being measured; It can be concluded that: Similarly, the point cloud measurement of the inner wall of the casing (10) is converted to the impeller coordinate system σ o In the impeller coordinate system σ o The point cloud coordinates of the inner wall of the casing are Q o , which can be expressed as: Among them, Q l For l Point cloud of the inner wall of the casing in the coordinate system; and is the coordinate system σ l With σ s The rotation matrix and translation matrix under the spatial position relationship, and is the coordinate system σ o With σ s The rotation matrix and translation matrix under the spatial position relationship, the rotation matrix during measurement is R2.

8. The method for measuring the tip clearance of a compressor rotor blade according to claim 7, characterized in that: The precise registration comprises the following steps: For the point cloud {P o } and {Q o }, calculate the normal vector of each point separately, for point p i ∈{P o }, fit a plane in its neighborhood, the normal vector is the eigenvector corresponding to the minimum eigenvalue of the plane, and the neighborhood point set is: N(p i )={p j |||p j -p i ||<∈} Where ∈ is the neighborhood radius and the covariance matrix is: The eigenvalue decomposition is: C = UΛU T Among them, Λ is a diagonal matrix, U is the eigenvector matrix, and the eigenvector corresponding to the minimum eigenvalue is the normal vector Normalize the normal vector: For every point p i ∈{P o }, find its nearest neighbor point q in the point cloud Q i , only matching point pairs whose normal vector angle is less than a certain threshold are retained: Among them, θ max is the preset normal vector angle threshold. If it is not less than θ max , then reselect the matching point pairs and use them as constraints to perform precise registration of the two point clouds.

9. A compressor blade tip clearance measuring device, characterized in that: The method for measuring the tip clearance of a compressor rotor blade according to any one of claims 1 to 8 comprises: An angle encoder (4) is arranged on the main shaft (9); A measuring instrument fixing fixture (2), one side of which is connected to the impeller (8), and the other side of which is used to connect to the three-dimensional laser profile measuring instrument (1) when measuring the inner wall of the casing (10); A three-axis mobile platform (3) is used to support and adjust the position of the three-dimensional laser profile measuring instrument (1) relative to the blade tip when measuring the blade tip of the blade (7); The controller (5) is connected to the angle encoder (4) and the computer (6) and is used to provide a communication library for acquiring images and a measurement library for functions such as contour measurement, interference removal, and image synthesis, as well as a display library for intuitive scanning results.

10. The compressor rotor blade tip clearance measuring device according to claim 9, characterized in that: The measuring instrument fixing fixture (2) has the same blade root type (201) as the blade (7) and can be directly assembled with the impeller (8).

Images