A testing system and method for testing the profile characteristics of complex-shaped blades

Abstract

This invention provides a testing system and method for the profile characteristics of complex-shaped propeller blades, including a measuring device, a screw-slide table, a blade root clamping device, a loading device, and a frame. One end of the blade under test is mounted on the top of the frame via the blade root clamping device, and the other end is connected to the loading device. The measuring device is mounted on the side of the frame via the screw-slide table. The blade root clamping device, in conjunction with the loading device, applies loads in the flapping, tessellation, and torsional directions of the blade. This invention enables distributed measurement of deformation displacement under flapping, tessellation, and torsional loads, and analyzes and determines the distribution of flapping, tessellation, and torsional stiffness in the blade profile. This invention eliminates the need to attach strain sensors to the blade, utilizes lasers for non-contact measurement, and employs a screw-slide table for precise control of the measurement points, significantly shortening test preparation time, avoiding the influence of human factors, and possessing the advantages of simple operation, good repeatability, and high measurement accuracy.

Description

Technical Field

[0001] This invention relates to the field of helicopter rotor blade measurement technology, specifically a test system and method for testing the profile characteristics of complex-shaped rotor blades. Background Technology

[0002] The rotor blade is a core component of a helicopter. Its dynamic characteristics directly determine the helicopter's vibration level, aeroelastic stability, and structural fatigue performance. Therefore, rotor blade dynamic characteristic design is a crucial step in helicopter rotor blade design. To accurately calculate the dynamic characteristics of the blade, it is necessary to accurately measure the distribution of the blade's flapping, flaring, and torsional section stiffness along the blade's spanwise direction. In helicopter design, measuring the section characteristics of the manufactured blades is an essential and crucial step. The measurement data can not only confirm the difference between the designed stiffness and the actual stiffness but also provide input data for helicopter aeroelastic dynamic analysis, ensuring the validity of the analysis results.

[0003] Traditional helicopter blade profile characteristic measurement technology measures the strain distribution of the blade under different loads by attaching sensors such as resistance strain gauges or fiber optic gratings to different positions on the blade surface. The attachment and loading processes are cumbersome, the amount of preparation work before testing is large, and the post-test cleaning is difficult.

[0004] New-generation rotor blades often employ complex shapes with single or double folds, such as swept-back or anhedral, to improve rotor aerodynamic performance and reduce noise levels. However, the complex geometry causes significant bending-torsional coupling deformation on the inner blade profile during blade profile characteristic measurements due to the applied tip load. This necessitates deploying more sensors to measure the distribution of blade deformation, greatly increasing the testing difficulty. Therefore, there is an urgent need for a testing method and system to achieve high-precision and efficient measurement of the profile characteristics of blades with complex shapes. Summary of the Invention

[0005] In order to solve the problems of the prior art, the present invention provides a test system and test method for the profile characteristics of complex-shaped propeller blades, which realizes non-contact, high-precision and efficient measurement of the profile characteristics of propeller blades.

[0006] This invention provides a test system for the profile characteristics of a complex-shaped blade, including a measuring device, a screw slide device, a blade root clamping device, a loading device, and a frame. One end of the blade to be tested is mounted on the top of the frame via the blade root clamping device, and the other end is connected to the loading device. The measuring device is mounted on the side of the frame via the screw slide device.

[0007] The measuring device includes a laser Doppler vibration meter and a fixed box. The fixed box is connected to a lead screw slide device and achieves vertical and lateral sliding and alignment with the loading device through the transverse lead screw slide device.

[0008] The frame includes columns and a support frame located on top of the columns, and the blade root clamping device is fixed to the support frame; short pulley rods and long pulley rods are arranged between the columns, and the loading device includes blade clamps, pulleys and weights. The pulleys are respectively connected to the short pulley rods and long pulley rods of the frame, and the blade clamps, pulleys and weights are connected by thin lines.

[0009] In a further improvement, the lead screw slide device includes one transverse lead screw slide device and two vertical lead screw slide devices. The vertical lead screw slide devices are fixed to the frame by a fixing plate. The transverse lead screw slide devices are connected to the vertical lead screw slide devices and slide vertically along the vertical lead screw slide devices. The measuring device is connected to the transverse lead screw slide device and slides laterally along the transverse lead screw slide device. Both the transverse and vertical lead screw slide devices include a bearing seat, a fixing plate, a lead screw, a lead screw slider, a coupling, and a stepper motor. The vertical lead screw slide devices are fixed to the frame by a fixing plate, while the transverse lead screw slide devices are fixed to the lead screw slider of the vertical lead screw slide device by a fixing plate.

[0010] Further improvements include a rotor root clamping device comprising a rotor root clamp, with a hole at the bottom for fixing to the helicopter rotor blade, and a groove at the top of the rotor root clamp parallel to the rotor blade chord line when clamping the rotor blade, for confirming the dial reading.

[0011] The present invention also provides a test method for a test system for the profile characteristics of a complex-shaped blade. The test system includes three test methods: measuring the blade flapping bending stiffness distribution, measuring the blade oscillation bending stiffness distribution, and measuring the blade torsional stiffness distribution.

[0012] When measuring the flapping bending stiffness distribution of the blade, the scale in the blade root clamping device is used to align the upper surface of the blade with the laser Doppler vibrometer. With and without a flapping load, the stepper motor is controlled to move the measuring point of the laser Doppler vibrometer along the blade pitch axis from the blade root to the blade tip. The distance between the blade pitch axis and the laser Doppler vibrometer is measured along the blade spanwise before and after loading to determine the deflection distribution in the flapping direction. The flapping stiffness of different blade profiles is then calculated using the following formula:

[0013]

[0014] In the formula, F is the concentrated load in the flapping direction, L is the spanwise position of the concentrated load applied to the blade, w1 is the flapping direction deflection of the micro-segment with endpoint position x1, and w2 is the flapping direction deflection of the micro-segment with endpoint position x2.

[0015] When measuring the distribution of blade oscillation bending stiffness, the scale in the blade root clamping device is used to align the blade leading edge with the laser Doppler vibration meter. Under no load and with oscillation load, the stepper motor is controlled to measure the distribution of the distance between the blade leading edge and the laser Doppler vibration meter along the blade span before and after loading, to determine the deflection distribution in the blade oscillation direction. The above formula is used to determine the oscillation stiffness of different blade sections.

[0016] When measuring the torsional stiffness distribution of the blade, the scale in the blade root clamping device is used to align the upper surface of the blade with the laser Doppler vibration meter. With and without torque load, a stepper motor is controlled to move the measurement points of the laser Doppler vibration meter from the blade root to the blade tip along the leading and trailing edges, respectively. The distances from the leading and trailing edges of the blade to the laser Doppler vibration meter are measured along the blade span before and after loading. The distribution of the blade torsion angle along the span is determined by the following formula:

[0017]

[0018] In the formula, and z L (x), z T (x) represents the distances from the leading and trailing edges of the blade to the laser Doppler vibration meter before and after loading, respectively; c is the blade chord length; and the torsional stiffness of different blade profiles is calculated using the following formula:

[0019]

[0020] In the formula, m is the weight of a single weight to which the torque is applied, φ1 is the torsion angle of the micro-segment with endpoint position x1, and φ2 is the torsion angle of the micro-segment with endpoint position x2.

[0021] The beneficial effects of this invention are as follows:

[0022] 1. The complex-shaped blade profile characteristic testing system of the present invention achieves non-contact, high-precision measurement of blade deformation displacement through laser technology, simplifies test preparation time, and greatly improves the measurement efficiency of blade profile characteristics.

[0023] 2. This invention utilizes a motor-driven screw slide mechanism to achieve rapid positioning and precise movement of the laser Doppler vibration meter in the vertical plane within the measuring device. This simplifies operation, reduces the influence of human factors, and improves experimental repeatability. By defining the motion path of the laser rangefinder, distributed measurement of the deformation displacement of complex-shaped blades can be achieved, determining their sectional characteristics in the flapping, oscillating, and torsional directions. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A schematic diagram of a test system for the cross-sectional characteristics of a complex-shaped propeller blade;

[0026] Figure 2 This is a schematic diagram of the measuring device;

[0027] Figure 3 This is a schematic diagram of a lead screw slide device;

[0028] Figure 4 Schematic diagram of the paddle root clamping device;

[0029] Figure 5 This is a schematic diagram of the loading device;

[0030] Figure 6 This is a schematic diagram of the framework;

[0031] Among them, 1-measuring device, 2-lead screw slide device, 3-blade root clamping device, 4-loading device, 5-frame, 6-laser Doppler vibration meter, 7-fixed box, 8-vertical lead screw bearing seat, 9-vertical lead screw fixing plate, 10-vertical lead screw, 11-vertical lead screw slider, 12-vertical lead screw coupling, 13-vertical lead screw stepper motor, 14-transverse lead screw bearing seat, 15-transverse lead screw fixing plate, 16-transverse lead screw, 17-transverse lead screw coupling, 18-transverse lead screw stepper motor, 19-transverse lead screw slider, 20-blade root clamp, 21-scale dial, 22-blade clamp, 23-pulley, 24-weight, 25-support frame, 26-short pulley rod, 27-long pulley rod, 28-second long pulley rod, 29-second short pulley rod. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1

[0034] This embodiment provides a test system for the cross-sectional characteristics of complex-shaped blades, such as... Figures 1 to 6As shown, it includes a measuring device 1, a lead screw slide device 2, a propeller root clamping device 3, a loading device 4, and a frame 5.

[0035] The measuring device includes a laser Doppler vibration meter 6 and a fixed box 7. The fixed box 7 is bolted to the transverse lead screw slider 19 through two holes at the top.

[0036] The lead screw slide assembly includes two vertical lead screw slide assemblies and a horizontal lead screw slide assembly. The vertical lead screw slide assembly includes a vertical lead screw bearing seat 8, a vertical lead screw fixing plate 9, a vertical lead screw 10, a vertical lead screw slider 11, a vertical lead screw coupling 12, and a vertical lead screw stepper motor 13. The horizontal lead screw slide assembly includes a horizontal lead screw bearing seat 14, a horizontal lead screw fixing plate 15, a horizontal lead screw 16, a horizontal lead screw coupling 17, a horizontal lead screw stepper motor 18, and a horizontal lead screw slider 19. The vertical lead screw slide assemblies are fixed to the support frame 25 by the vertical lead screw fixing plates 9, while the horizontal lead screw slide assemblies are fixed to the vertical lead screw slider 11 by the horizontal lead screw fixing plates 15.

[0037] The propeller root clamping device includes a propeller root clamp 20 and a scale 21. The scale 21 is fixed to the support frame 25 through its four through holes for confirming the installation angle.

[0038] The loading device includes a blade clamp 22, a pulley 23, and a weight 24. The blade clamp 23 is fixed to the tip of the blade to be tested, and the blade clamp 22, the pulley 23, and the weight 24 are connected by a thin wire.

[0039] The frame includes a support frame 25, a short pulley rod 26 and a second short pulley rod 29, a long pulley rod 27 and a second long pulley rod 28. The support frame 25 and the paddle root clamping device are connected in the center of the support frame by bolts. The short pulley rod 26 and the second short pulley rod 29, along with the long pulley rod 27 and the second long pulley rod 28, are used to fix the pulleys.

[0040] Furthermore, the lead screw of the vertical and horizontal lead screw slide device is fixed to the bearing seat within the bearing seat. The lead screw is connected to the stepper motor through a coupling. The rotation of the stepper motor will drive the lead screw to rotate. The stepper motors of the horizontal lead screw slide device and the two vertical lead screw slide devices cooperate with each other to realize the horizontal and vertical movement of the measuring point of the laser Doppler vibration meter 6 fixed on the horizontal lead screw slider 19.

[0041] Furthermore, the blade root clamp 20 in the blade root clamping device is fixed to the blade through two holes at the bottom, and has a groove at the top that is parallel to the blade chord line when clamping the blade, which is used to confirm the scale reading.

[0042] Furthermore, the pulley 23 can be connected to the short pulley rod 26 and the second short pulley rod 29 of the support frame 25, as well as the long pulley rod 27 and the second long pulley rod 28, respectively, in conjunction with the blade root clamping device 3, to realize the loading of the blade flapping, oscillating and torsional directions.

[0043] Example 2

[0044] This embodiment provides a specific method for measuring the bending stiffness distribution in the flapping and oscillation directions of a blade using a complex-shaped blade profile characteristic testing system. The blade flapping bending stiffness is measured according to the following steps.

[0045] Step 1: Align the mounting hole at the root of the blade to be tested with the mounting hole of the blade root clamp, fix it with bolts, and fix it on the support frame, so that the scale of the blade root clamping device is at 0 degrees, that is, the upper surface of the blade faces the laser Doppler vibration meter.

[0046] Step 2: Start the stepper motors on the vertical and horizontal lead screw slides, so that the horizontal lead screw slider drives the laser Doppler vibration meter to move, so that the laser emitted by the laser Doppler vibration meter is aligned with the variable pitch axis position of the blade root section.

[0047] Step 3: With the blade unloaded, start the laser Doppler vibration meter to record data. Control the laser Doppler vibration meter to move along the blade pitch axis at a certain speed towards the blade tip using a stepper motor, and record the distance between the blade pitch axis and the laser Doppler vibration meter when unloaded.

[0048] Step 4: Use a stepper motor to return the laser Doppler vibration meter to the starting point of Step 2, place the pulley on the short pulley rod 26, add weights to the loading device to make the helicopter blades bend in the direction of flapping.

[0049] Step 5: Control the laser Doppler vibration meter to move downwards at a certain speed along the blade pitch axis under load using a stepper motor, and record the distance between the blade pitch axis and the laser Doppler vibration meter under load.

[0050] Step Six: Repeat Steps Four and Five to record the distance between the blade pitch axis and the laser Doppler vibration meter under different weights;

[0051] Step 7: Remove the rotor blade clamps and detach the helicopter rotor blades for data processing.

[0052] Since the blade is a slender beam structure, the displacement in the flapping direction is much greater than the displacement in the tensile direction. Therefore, the deformation displacement in the tensile direction of the blade profile under loading is ignored. Subtracting the result measured in step three (unloaded state) from the distance between the laser Doppler vibration meter and the blade's pitch axis under loading (measured in step five) yields the bending deflection distribution function w(x) of the blade's pitch axis under flapping direction bending load. Assuming the blade is a cantilever beam with bending stiffness varying along its span, according to the principles of mechanics of materials, the bending moment M and deflection w under bending conditions have the following relationship:

[0053]

[0054] Among them, EI y Let F be the flapping bending stiffness of the blade. When a concentrated load F is applied at the end of the beam at x = L, the bending moment is distributed along the spanwise direction as M(x) = F(Lx). Taking a small segment with spanwise positions x1 and x2 at its two ends, assuming that the flapping bending stiffness of this segment does not change, the deflection increment of this small segment can be obtained by performing a quadratic integration of w” over the interval [x1, x2].

[0055]

[0056] Therefore, the flapping bending stiffness of this blade segment is:

[0057]

[0058] The blade is divided into multiple micro-segments (more than 10). Starting from the blade root, the distribution of blade flapping bending stiffness is calculated using the measured deflection on both sides of each micro-segment according to the above formula. The blade flapping bending stiffness is calculated under different loads, and the average value is taken to obtain the distribution of blade flapping bending stiffness.

[0059] When measuring the directional stiffness distribution of a blade's teeter vibration using a complex-shaped blade profile characteristic testing system, adjustments to the blade's mounting position are necessary. Step one is adjusted so that when the blade is fixed to the support frame using the blade root clamp, the scale of the blade root clamping device is at 90 degrees, meaning the blade's leading edge faces the laser Doppler vibrometer. During the measurement process, the laser Doppler vibrometer measures the spatial position of the leading edge line at different profile locations. The remaining steps are the same, ultimately determining the distribution of the blade's teeter vibration bending stiffness.

[0060] Example 3:

[0061] This embodiment provides a specific method for measuring the torsional stiffness distribution of a blade using a complex-shaped blade profile characteristic testing system. The method for measuring the torsional stiffness distribution of a blade using a complex-shaped blade profile characteristic testing system based on a laser Doppler vibrometer differs significantly from the methods for measuring the stiffness in the flapping and oscillating bending directions. The measurement is performed according to the following steps.

[0062] Step 1: Align the mounting hole at the root of the blade to be tested with the mounting hole of the blade root clamp, fix it with bolts, and fix it on the support frame, so that the scale of the blade root clamping device is at 0 degrees, that is, the upper surface of the blade faces the laser Doppler vibration meter.

[0063] Step 2: Start the stepper motors on the vertical and horizontal lead screw slides, so that the horizontal lead screw slider drives the laser Doppler vibration meter to move, so that the laser emitted by the laser Doppler vibration meter is aligned with the leading edge line of the blade root section.

[0064] Step 3: With the blade unloaded, start the laser Doppler vibration meter to record data. Control the laser Doppler vibration meter to move along the blade leading edge line towards the blade tip at a certain speed using a stepper motor, and record the distance between the blade leading edge line and the laser Doppler vibration meter when unloaded.

[0065] Step 4: Start the stepper motors of the vertical and horizontal lead screw slides, so that the horizontal lead screw slider drives the laser Doppler vibration meter to move, so that the laser emitted by the laser Doppler vibration meter is aligned with the trailing edge line of the blade root section.

[0066] Step 5: With the blade unloaded, start the laser Doppler vibration meter to begin recording data. Use a stepper motor to control the laser Doppler vibration meter to move along the trailing edge of the blade towards the blade tip at a certain speed, and record the distance between the trailing edge of the blade and the laser Doppler vibration meter when unloaded.

[0067] Step 6: Use a stepper motor to return the laser Doppler vibration meter to the starting point of Step 2. Place the two pulleys on short pulley rods 26 and 27 respectively. Add weights of m to the loading device to cause the helicopter blades to bend in the torsional direction.

[0068] Step 7: Control the laser Doppler vibration meter to move downwards at a certain speed along the leading edge and trailing edge of the blade under load using a stepper motor, and record the distances from the leading edge and trailing edge of the blade to the laser Doppler vibration meter under load.

[0069] Step 8: Repeat steps 6 and 7 to record the distribution of the distances from the leading and trailing edges to the laser Doppler vibrometer after the blades deform in the torsional direction under different weights.

[0070] Step Nine: Remove the rotor blade clamps and detach the helicopter rotor blades for data processing.

[0071] Since the blade is a slender beam structure, the distance distribution between the leading and trailing edges of the blade and the laser Doppler vibration meter under loaded conditions, as measured by the laser Doppler vibration meter in step seven, is denoted as z. L (x) and z T (x) represents the distance distribution between the leading and trailing edges in the unloaded states of steps three and five. and The distribution function φ(x) of the blade torsional deformation can be obtained by the following formula:

[0072]

[0073] Where c is the blade chord length.

[0074] Assuming the blade is a cantilever beam with torsional stiffness varying along its span, according to the principles of mechanics of materials, the torque T and torsional deformation φ(x) under torsional conditions have the following relationship:

[0075]

[0076] Where GJ is the torsional stiffness of the blade. When a torque T is applied at the end x = L of the beam, a small segment is taken out, with its two ends at spanwise positions x1 and x2 respectively. Assuming that the torsional stiffness of this segment does not change, the increment of the torsional angle of this small segment can be obtained by integrating φ' over the interval [x1, x2].

[0077]

[0078] Furthermore, the torque T = mc, thus the torsional stiffness of this blade section is:

[0079]

[0080] The blade is divided into multiple micro-segments (more than 10). Starting from the blade root, the distribution of the blade's torsional stiffness is calculated using the measured torsion angles on both sides of each micro-segment according to the above formula. The distribution of the blade's torsional stiffness is obtained by calculating the blade's torsional stiffness under different torsional loads and taking the average value.

[0081] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0082] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. In particular, for the device embodiments, the above descriptions are merely preferred embodiments of the present invention. Since they are fundamentally similar to the method embodiments, the descriptions are relatively simple, and relevant parts can be referred to the descriptions of the method embodiments. The above descriptions are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention, without departing from the principle of the present invention, should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A test system for the profile characteristics of a complex-shaped propeller blade, characterized in that: It includes a measuring device, a screw slide device, a blade root clamping device, a loading device, and a frame. One end of the blade to be measured is mounted on the top of the frame via the blade root clamping device, and the other end is connected to the loading device. The measuring device is mounted on the side of the frame via the screw slide device. The measuring device includes a laser Doppler vibration meter and a fixed box. The fixed box is connected to a lead screw slide device and achieves vertical and lateral sliding and alignment with the loading device through the transverse lead screw slide device. The frame includes columns and a support frame located on top of the columns, and the blade root clamping device is fixed to the support frame; short pulley rods and long pulley rods are arranged between the columns, and the loading device includes blade clamps, pulleys and weights. The pulleys are respectively connected to the short pulley rods and long pulley rods of the frame, and the blade clamps, pulleys and weights are connected by thin lines.

2. The complex-shaped blade profile characteristic testing system according to claim 1, characterized in that: The lead screw slide device includes a transverse lead screw slide device and two vertical lead screw slide devices. The vertical lead screw slide devices are fixed to the frame by a fixing plate. The transverse lead screw slide devices are connected to the vertical lead screw slide devices and slide vertically along the vertical lead screw slide devices. The measuring device is connected to the transverse lead screw slide device and slides laterally along the transverse lead screw slide device.

3. The complex-shaped blade profile characteristic testing system according to claim 2, characterized in that: Both the transverse lead screw slide device and the vertical lead screw slide device include a bearing seat, a fixing plate, a lead screw, a lead screw slider, a coupling, and a stepper motor. The vertical lead screw slide device is fixed to the frame by the fixing plate, while the transverse lead screw slide device is fixed to the lead screw slider of the vertical lead screw slide device by the fixing plate.

4. The complex-shaped blade profile characteristic testing system according to claim 1, characterized in that: The rotor root clamping device includes a rotor root clamp, with a hole at the bottom for fixing to the helicopter rotor blade, and a groove at the top of the rotor root clamp that is parallel to the rotor blade chord when clamping the rotor blade, for confirming the scale reading.

5. A test method for a complex-shaped blade profile characteristic test system, employing the complex-shaped blade profile characteristic test system described in any one of claims 1-4, characterized in that: It includes three testing methods: measuring the blade flapping bending stiffness distribution, measuring the blade oscillation bending stiffness distribution, and measuring the blade torsional stiffness distribution. When measuring the flapping bending stiffness distribution of the blade, the scale in the blade root clamping device is used to align the upper surface of the blade with the laser Doppler vibrometer. With and without a flapping load, the stepper motor is controlled to move the measuring point of the laser Doppler vibrometer along the blade pitch axis from the blade root to the blade tip. The distance between the blade pitch axis and the laser Doppler vibrometer is measured along the blade spanwise before and after loading to determine the deflection distribution in the flapping direction. The flapping stiffness of different blade profiles is then calculated using the following formula: In the formula, F is the concentrated load in the flapping direction, L is the spanwise position of the concentrated load applied to the blade, w1 is the flapping direction deflection of the micro-segment with endpoint position x1, and w2 is the flapping direction deflection of the micro-segment with endpoint position x2. When measuring the distribution of blade oscillation bending stiffness, the scale in the blade root clamping device is used to align the blade leading edge with the laser Doppler vibration meter. Under no load and with oscillation load, the stepper motor is controlled to measure the distribution of the distance between the blade leading edge and the laser Doppler vibration meter along the blade span before and after loading, to determine the deflection distribution in the blade oscillation direction. The above formula is used to determine the oscillation stiffness of different blade sections. When measuring the torsional stiffness distribution of the blade, the scale in the blade root clamping device is used to align the upper surface of the blade with the laser Doppler vibration meter. With and without torque load, a stepper motor is controlled to move the measurement points of the laser Doppler vibration meter from the blade root to the blade tip along the leading and trailing edges, respectively. The distances from the leading and trailing edges of the blade to the laser Doppler vibration meter are measured along the blade span before and after loading. The distribution of the blade torsion angle along the span is determined by the following formula: In the formula, and z L (x), z T (x) represents the distances from the leading and trailing edges of the blade to the laser Doppler vibration meter before and after loading, respectively; c is the blade chord length; and the torsional stiffness of different blade profiles is calculated using the following formula: In the formula, m is the weight of a single weight to which the torque is applied, φ1 is the torsion angle of the micro-segment with endpoint position x1, and φ2 is the torsion angle of the micro-segment with endpoint position x2.

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