A method for calculating throat area measurement error

Abstract

A method for calculating throat area measurement error, comprising the following steps: installing a turbine casing on a rotary table of a coordinate measuring machine, the turbine casing having a pilot; obtaining an inclination vector of the pilot; obtaining a first set of measuring points; obtaining a pilot throat angle; obtaining a second set of measuring points according to the inclination vector and the first set of measuring points; substituting the first set of measuring points and the second set of measuring points into a throat area calculation formula respectively, and calculating a difference value to obtain a throat area measurement error.

Description

Technical Field

[0001] This invention relates to engine assembly, and more specifically to a method for calculating the measurement error of the throat area. Background Technology

[0002] The minimum exhaust edge area in the converging channel of the guide vane is called the guide vane throat area. The size of the guide vane throat area directly affects engine performance. Practice has shown that changes in the throat area of ​​the high-pressure turbine first-stage guide vane and the low-pressure turbine first-stage guide vane affect the engine's high-pressure speed, thrust, Mach 2 performance, T4 temperature, and fuel consumption rate. Therefore, the throat area of ​​the engine blade is an important parameter for engine assembly and debugging, and its measurement is crucial for blade assembly. The blade channel is a spatial curved surface channel formed by the upper and lower edge plates of the blade and the airfoil profiles between each pair of blades. The designed throat area measuring instrument can accurately detect the channel width dimension of a specified cross-section between each channel window and the channel height dimension of the upper and lower edge plates, thereby calculating the blade's throat area. The flow rate of the throat area is related to the engine's thrust. Obtaining the uniformity of exhaust volume in the blade channel through the throat area measuring instrument is key to engine performance analysis.

[0003] Currently, the common method for measuring throat area is to use a coordinate measuring machine (CMM). The measurement process involves placing a turntable on the CMM, then placing the turbine casing unit with the guide assembly on the turntable, and performing centering, that is, aligning the center of the guide with the center of the turntable. Then, the CMM is used to measure the area of ​​the first window. After the measurement is completed, the turntable is controlled to move by one division angle phase, and then the area of ​​the next window is measured.

[0004] Based on error analysis during the actual measurement process, the inventors discovered that the measurement results obtained from the experiment contained errors. Summary of the Invention

[0005] The purpose of this invention is to provide a method for calculating the measurement error of the throat area, which is used to perform error analysis on the measurement results of the throat area of ​​a turbine guide vane, so as to reduce the test error.

[0006] The method for calculating the throat area measurement error includes the following steps: mounting the turbine casing on the turntable of a coordinate measuring machine, the turbine casing having a guide; obtaining the tilt vector of the guide; obtaining a first set of measuring points; obtaining the graduated throat angle; obtaining a second set of measuring points based on the tilt vector and the first set of measuring points, the second set of measuring points being obtained by the following formula:

[0007] {G}=R1 -1 R -1 R1R{E}

[0008]

[0009]

[0010] Where β is the graduated throat angle, v y v is the component of the tilt vector in the y-direction. z Let {E} be the component of the tilt vector in the z-direction, {G} be the first set of measuring points, and {G} be the second set of measuring points.

[0011] Substitute the first set of measuring points and the second set of measuring points into the formula for calculating the throat area, and calculate the difference between the two to obtain the throat area measurement error.

[0012] In one or more embodiments, the tilt vector is obtained by the following steps: using the coordinate measuring machine, a measurement coordinate system is established with the reference plane of the guide as a reference; the turntable is rotated to obtain the rotation axis of the turntable; the unit direction vector of the measurement coordinate system relative to the rotation axis is the tilt vector.

[0013] In one or more embodiments, the tilt vector is obtained through the following steps: rotating the turntable; during rotation, measuring the end runout value of the guide's reference plane relative to the rotation plane of the turntable; obtaining the tilt amount and low-point angle phase of the reference plane relative to the rotation plane; obtaining the runout measurement diameter of the reference plane; and obtaining the components of the tilt vector in the x, y, and z directions using the following formulas:

[0014]

[0015] Among them, v x v is the component of the tilt vector in the x-direction. y v is the component of the tilt vector in the y-direction. z Let be the component of the tilt vector in the z-direction, D be the jump measurement diameter, p be the tilt amount, and u be the low point angle phase.

[0016] In one or more embodiments, during the measurement process, considering that the first set of measuring points rotates by a first angle λ about the z-axis, the second set of measuring points is obtained by the following formula:

[0017] {G}=R2 -1 R1 -1 R -1 R1RR2{E}

[0018]

[0019] The above-mentioned method for calculating the throat area measurement error is based on the tilt vector generated during the assembly of the turbine guide assembly and the turntable of the coordinate measuring machine. The error value caused by the change of the tilt vector relative to the established coordinate system during the measurement rotation is obtained. The throat area measurement result is analyzed, and the error analysis result can also be used to assist in the subsequent correction of the throat area measurement result and reduce the measurement error. Attached Figure Description

[0020] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, wherein:

[0021] Figure 1 This is a schematic diagram of throat area detection according to one embodiment.

[0022] Figure 2 This is a flowchart of the calculation method for the measurement error of the throat area. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description to provide a full understanding of the invention. However, the invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual applications without departing from the spirit of the invention. Therefore, the scope of protection of the invention should not be limited by the content of these specific embodiments. It should be noted that these and subsequent accompanying drawings are merely examples and are not drawn to scale, and should not be construed as limiting the actual scope of protection claimed by the invention.

[0024] like Figure 1 As shown, a coordinate measuring machine 3 is used to measure the throat area of ​​the guide 2. The turbine casing assembly with the guide 2 is mounted on the turntable 1 of the coordinate measuring machine 3. When measuring the throat area of ​​one window and then measuring the throat area of ​​the next window, the turntable 1 will rotate a certain angle. Since the plane of the coordinate system established for the throat measurement (the plane indicated by mark 21 in the figure) is not parallel to the plane where the turntable 1 is located (the plane indicated by mark 11 in the figure), the guide 2 will rotate at a different angle. If the coordinate system used for the previous window measurement is still used for measurement, the throat area measurement result will be incorrect.

[0025] like Figure 2As shown, a method for calculating the throat area measurement error includes the following steps: S1 assembling the turntable 1 and the guide 2; S2 obtaining the tilt vector v; S3 obtaining the first set of measuring points {E}; S4 obtaining the graduated throat angle β; S5 obtaining the second set of measuring points {G}; S6 calculating the throat area measurement error. This method performs error analysis on the throat area measurement results based on the tilt vector v, obtaining the systematic error value caused by the change of the tilt vector v relative to the established coordinate system during the measurement rotation process. It then analyzes the throat area measurement results and performs auxiliary corrections to reduce experimental error.

[0026] Step S1: Assemble turntable 1 and guide 2, refer to Figure 1 The turbine casing is installed on the turntable 1 of the coordinate measuring machine 3. The turbine casing has a guide 2. The guide 2 is aligned so that the center of the guide 2 is aligned with the center of the turntable 1. In the assembly state shown in the figure, there is a certain angle between the rotation plane 11 of the turntable 1 (i.e. the upper surface of the turntable) and the upper surface 21 of the guide.

[0027] Step S2: Obtain the tilt vector v. In one embodiment, the tilt vector v of the guide 2 relative to the turntable 1 can be obtained through the following steps:

[0028] Using a coordinate measuring machine 3, a measurement coordinate system is established with the reference plane of the guide 2 as a reference;

[0029] Rotate turntable 2 to obtain the rotation axis 12 of turntable 1;

[0030] The unit direction vector of the measurement coordinate system relative to the rotation axis 12 is the tilt vector v.

[0031] The reference plane of guide 2 refers to the reference plane of the coordinate system established for measuring the throat area of ​​guide 2. This plane is perpendicular to the rotation axis 22 of guide 2. A measurement coordinate system is established with this reference plane as the yz plane. Figure 1 In the embodiment shown, the reference plane of the guide 2 is the upper surface 21 of the guide.

[0032] In the above embodiment, a coordinate measuring machine 3 is used to establish a measurement coordinate system on the guide 2. Then, the turntable 1 is rotated. During the rotation, the coordinate measuring machine 3 is used to measure multiple measuring points formed by the rotation. The coordinate measuring machine 3 can obtain the rotation axis 12 of the turntable 1 through the coordinate positions of the multiple measuring points before and after the rotation. The unit direction vector of the rotation axis 12 relative to the reference plane of the established coordinate system is the tilt vector v, which can be obtained by calculation.

[0033] In another implementation, the tilt vector v can be obtained through the following steps:

[0034] Rotate turntable 1;

[0035] During rotation, the end runout value of the reference plane of the measuring guide 2 relative to the rotation plane of the turntable 1 is measured.

[0036] Obtain the tilt p of the reference plane relative to the rotation plane and the low point angle u;

[0037] Obtain the runout measurement diameter D of the reference plane;

[0038] The components of the tilt vector v in the x, y, and z directions can be obtained using the following formula (1):

[0039]

[0040] Among them, v x v is the component of the tilt vector in the x-direction. y v is the component of the tilt vector in the y-direction. z The x-direction in this embodiment refers to the axial direction of the guide vane 2 along the engine's heading, and the yz-plane is a plane perpendicular to the rotation axis 22 of the guide vane 2. Figure 1 In one embodiment shown, the yz plane is the upper surface 21 of the guide.

[0041] In the above embodiment, the guide 2 is driven by the turntable 1 to rotate around the rotation axis 12 of the turntable 1. The end runout value of the reference plane relative to the rotation plane is measured by the coordinate measuring machine 3. The tilt amount p and the low point angle u are obtained by least square fitting of the end runout value. The runout measurement diameter D of the reference plane of the guide 2 can be directly measured by the coordinate measuring machine 3 or by the vernier caliper. Then, the tilt vector v can be obtained by substituting it into formula (1).

[0042] Step S3: Obtain the first set of measuring points {E}. Starting from step 3, the throat area of ​​the guide vane 2 is measured. First, the throat area of ​​the first window is measured. Using a coordinate measuring machine 3, multiple key measuring points on the upper and lower edge plates of the guide vane 2, as well as the guide vane base and the back of the vane, are measured and calculated to obtain the coordinate positions of multiple key measuring points. The set of coordinates of these multiple key measuring points is defined as the first set of measuring points {E}. Key measuring points refer to the multiple measuring points specified in the experimental design that need to be measured during the throat area measurement process. Substituting the coordinate positions of these multiple measuring points into the throat area calculation formula yields the throat area of ​​the guide vane 2.

[0043] Step S4: Obtain the graduated throat angle β. The graduated throat angle β refers to the angle that the rotating turntable 1 rotates when it switches from the first window where the throat area needs to be measured to the second window, that is, the angle of rotation around the X-axis.

[0044] When switching from the first window to the second window for measurement, the turntable 1 rotates relative to its own turntable axis 12, not relative to the rotation axis 22 of the guide 2. However, when establishing the throat area measurement coordinate system using the coordinate measuring machine 3, the axis selected for this measurement coordinate system must be the rotation axis 22 of the guide 2. In the actual measurement process, when the turntable 1 rotates by an angle β, it is assumed that the guide 2 also rotates by an angle β around its own axis. Subsequently, multiple key measuring points are measured and the throat area is calculated. Therefore, after the turntable 1 rotates, due to the influence of the tilt vector v, the coordinate positions of multiple key measuring points in the second window are not the coordinate positions of the first measuring point set {E} when measuring the first window. The coordinate positions of multiple key measuring points after rotation should be obtained according to the coordinate system established by the rotation axis 22 of the guide 2, and the coordinate positions of multiple key measuring points after rotation should be defined as the second measuring point set {G}. Substituting the first measuring point set {E} and the second measuring point set {G} into the throat area calculation formula, the difference between the latter and the former calculation result is the throat area measurement error. In summary, finding the second set of measurement points {G} based on the tilt vector v is the key to error analysis.

[0045] Step S5: Obtain the second set of measuring points {G}. Specifically, the second set of measuring points {G} is obtained based on the tilt vector v, the first set of measuring points {E}, and the graduation throat angle β. The second set of measuring points {G} can be calculated using the following formula (2):

[0046] {G}=R1 -1 R -1 R1R{E}

[0047]

[0048]

[0049] Among them, v y Let v be the component of the tilt vector v in the y-direction. z Let v be the component of the tilt vector v in the z direction. The tilt vector v is obtained in the aforementioned step S2. R1 is the rotation matrix of turntable 1, and R is the error matrix formed due to the existence of the tilt vector v.

[0050] In one implementation, taking the z-axis of the measurement coordinate system established by the guide 2 as an example, during the measurement process, considering that the first set of measuring points {E} rotates by a first angle λ with the z-axis as the rotation axis, the attitude adjustment matrix R2 needs to be added to the calculation formula of the second set of measuring points {G}. The attitude adjustment matrix R2 can be obtained through formula (3):

[0051]

[0052] Wherein, λ is the direction angle specified in the measurement requirements. The presence or absence of λ is related to the required measurement direction. Specifically, when calculating the throat area, some calculation methods can simplify the calculation process by measuring the direction angle λ. Therefore, in these methods of calculating the throat area, the direction angle λ is often assumed during measurement. The second set of measurement points {G} after adding the attitude adjustment matrix R2 can be obtained by formula (4):

[0053] {G}=R2 -1 R1 -1 R -1 R1RR2{E} (4)

[0054] Step S6: Calculate the throat area measurement error σ. Specifically, substitute the first set of measuring points {E} and the second set of measuring points {G} into the throat area calculation formula f(x) respectively, and calculate the difference between the two according to formula (5) to obtain the throat area measurement error σ. This measurement error is the measurement error caused by the existence of the tilt vector v.

[0055] σ=f({G})-f({E}) (5)

[0056] The formula for calculating the throat area varies depending on the actual experimental design requirements. The principle is to obtain the width characteristics from the measuring points on the leaf base and leaf back in the key measuring point set, and to obtain the height characteristics from the measuring points on the upper and lower edge plates. The throat area is then calculated by constructing a quadrilateral. Since the throat structures of different guides used in actual experiments are different, the formula for calculating the throat area is also different. Therefore, the above formula (5) uses f(x) to represent the throat area calculation formula, and f(x) can be different in different experiments.

[0057] The above-mentioned method for calculating the throat area measurement error uses the tilt vector caused by the assembly of the guide assembly to perform error analysis on the throat area measurement. The result of this error analysis can be used to assist in the subsequent correction of the throat area measurement result, thereby improving the engine inspection quality and the first-time assembly pass rate of the engine.

[0058] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any variations and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for calculating the measurement error of the throat area, characterized in that, Includes the following steps: The turbine casing is mounted on the turntable of a coordinate measuring machine, and the turbine casing has a guide. Obtain the tilt vector of the guide; Obtain the first set of measurement points; Obtain the graduated throat angle; A second set of measuring points is obtained based on the tilt vector and the first set of measuring points, and the second set of measuring points is obtained by the following formula: {G}R1 -1 R -1 R1R{E} Where β is the graduated throat angle, v y v is the component of the tilt vector in the y-direction. z Let {E} be the component of the tilt vector in the z-direction, {G} be the first set of measuring points, and {G} be the second set of measuring points. Substitute the first set of measuring points and the second set of measuring points into the formula for calculating the throat area, and calculate the difference between the two to obtain the throat area measurement error.

2. The method for calculating the error in throat area measurement as described in claim 1, characterized in that, The tilt vector is obtained through the following steps: Using the coordinate measuring machine, a measurement coordinate system is established with the reference plane of the guide as a reference; Rotate the turntable to obtain the rotation axis of the turntable; The unit direction vector of the measurement coordinate system relative to the axis of rotation is the tilt vector.

3. The method for calculating the measurement error of the throat area as described in claim 1, characterized in that, The tilt vector is obtained through the following steps: Rotate the turntable; During rotation, the end runout value of the guide's reference plane relative to the rotation plane of the turntable is measured; Obtain the tilt amount and low-point angle phase of the reference plane relative to the rotation plane; Obtain the runout measurement diameter of the reference plane; The components of the tilt vector in the x, y, and z directions are obtained using the following formula: Among them, v x v is the component of the tilt vector in the x-direction. y v is the component of the tilt vector in the y-direction. z Let be the component of the tilt vector in the z-direction, D be the jump measurement diameter, p be the tilt amount, and u be the low point angle phase.

4. The method for calculating the error in throat area measurement as described in claim 1, characterized in that, During the measurement process, considering that the first set of measuring points rotates by a first angle λ about the z-axis, the second set of measuring points is obtained by the following formula: {G}=R2 -1 R1 -1 R -1 R1RR2{E}

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