Sawtooth-shaped blade crown blade vibration characteristic test device capable of adjusting pre-torsion angle

Abstract

The invention discloses a sawtooth-shaped blade crown blade vibration characteristic test device with an adjustable pre-torsion angle, which belongs to a test device in the technical field of aviation systems and can apply a torsion angle to generate vibration characteristics of a blade with a sawtooth crown at different pre-torsion angles. Namely, the average contact pressure between the working surfaces of the sawtooth crown and the frequency and the vibration mode of each order of the blade of the sawtooth crown meet the test requirements for verifying the applicability of the selected contact stiffness model between the working surfaces of the sawtooth crown. The device comprises a blade with a sawtooth crown, a clamping mechanism and a loading mechanism, wherein the blade with the sawtooth crown is a simplified blade, and a blade body is perpendicular to the blade crown and the blade base. The loading mechanism is composed of a pushing piece assembly and a torsion disc. Wherein the pushing piece assembly is divided into a first pushing piece 3-1 (a) and a second pushing piece 3-1 (b) which are located on the two sides of the working face of the sawtooth crown respectively, abut against and make contact with the working face and are installed and fixed to the surface of the torsion disc. The pre-twisting device has the advantages that the structure is simple and reasonable, and different pre-twisting angles can be applied to the shrouded blade.

Description

Technical Field

[0001] The invention relates to the technical field of aviation systems, and in particular to a vibration characteristic test device for a sawtooth shroud blade with an adjustable pre-twist angle. Background Art

[0002] In aircraft engines, turbine blades are one of the important parts. They work in harsh conditions and harsh working environments. They often bear the periodic impact of high-temperature and high-pressure gas under high-speed rotation, causing high-cycle fatigue vibration. In order to improve the overall stiffness of the turbine rotor, enhance the vibration resistance, reduce the maximum vibration stress of the turbine rotor blades, and extend the service life, the blades are often designed with a serrated crown structure. In this way, the mutual contact and friction between adjacent serrated crowns can be used to reduce the torsional deformation and bending deformation of the blades, increase the rigidity of the blades, increase the natural frequency of the blades, absorb vibration energy, and achieve the purpose of vibration reduction.

[0003] The vibration characteristic analysis of blades with serrated crowns is the main content of blade design with serrated crowns, and it is also an important prerequisite for the vibration reduction characteristic analysis of blades with serrated crowns. The accuracy of the results directly affects the accuracy of the vibration reduction characteristic analysis results of blades with serrated crowns. When analyzing the vibration characteristics of blades with serrated crowns, the contact stiffness directly affects the friction between the working surfaces of the serrated crowns and the change of the contact state, which in turn affects the natural frequency and response of the blades with serrated crowns, thereby affecting the vibration reduction effect of the serrated crowns and the dynamic characteristics of the blades. Many scholars at home and abroad have studied the contact stiffness model, including the Coulomb friction model, the "hysteresis" spring friction model, and the overall or local unified sliding friction model. However, these contact stiffness models only focus on solving the tangential contact stiffness and friction damping between the working surfaces of the serrated crowns, and the normal contact stiffness is often replaced by empirical values, ignoring the influence of the normal contact stiffness on the vibration characteristics of the serrated crowns. For research purposes, a contact stiffness model between the working surfaces of serrated crowns derived from the MB fractal contact model was selected. However, the application of this contact stiffness model on the working surface of serrated crowns is the first case, and there is a lack of experimental data to verify the applicability of this contact stiffness model in the analysis of vibration characteristics of serrated crowns. In addition, in the influence law of parameters on vibration characteristics, although some scholars have obtained some theoretical analysis and experimental verification and achieved certain results, most of them are theoretical and mechanism research, lacking the influence analysis of the influence law of torsion angle on the vibration characteristics of serrated crowns under actual experimental conditions and the influence analysis of different torsion angles on the contact stress between the working surfaces of serrated crowns.

[0004] The "A Sawtooth Triple-mounted Shrouded Blade Vibration Reduction Characteristics Experimental Device" disclosed in Chinese Patent Application No. 201310159983.9 realizes the research on the vibration reduction characteristics of shrouded blades under different contact angles, pre-twist angles, and contact positive pressures. However, when conducting experiments on the influence of the key parameters of the pre-twist angle, it is necessary to adjust the device to ensure that the contact angle of the blade shroud remains unchanged. The experimental steps are cumbersome and the device structure is complex. The "A Shrouded Blade Experimental Fixture and Shrouded Blade Experimental Device" disclosed in Chinese Patent Application No. 202321589383.1 adjusts the pre-twist angle of the shrouded blade by rotating the blade root, and at the same time changes the contact positive pressure of the blade, meeting the experimental requirements for measuring the vibration characteristics of shroud blades with different pre-twist angles. However, when changing the pre-twist angle, it is necessary to adjust the four sets of bolts at the root of the blade at the same time, and the process of adjusting the pre-twist angle is relatively complicated. In addition, both patents require three sets of shroud blades to conduct experiments when in use, which cannot meet the experimental requirements for measuring the vibration characteristics of a single set of shroud blades. In addition, it does not explain how to use the device for modal experiments, and does not explain the specific experimental methods and measuring instruments. The operation scheme of this design is more convenient and the experimental device is simpler. It only needs to control the pre-twist angle parameters and adjust the hexagonal flange bolts to change the pre-twist angle. The patented measuring instruments and experimental methods can be used to measure the contact stress, frequency and formation of a single set of blade crowns. Summary of the invention

[0005] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the problems existing in the above-mentioned existing sawtooth shroud blade vibration characteristic test device with adjustable pre-twist angle, the present invention is proposed.

[0007] Therefore, the purpose of the present invention is to provide a vibration characteristic test device for a serrated crown blade with an adjustable pre-twist angle, which can measure the natural frequency and vibration mode of a blade with a serrated crown at different torsion angles, obtain the influence law of vibration characteristics at different torsion angles, and cooperate with corresponding measuring instruments to obtain the contact stress changes between the working surfaces of the serrated crown at different torsion angles, so as to verify the applicability of the selected contact stiffness model between the working surfaces of the serrated crown. The torsion angle can be adjusted, the extrusion pressure, frequency, and formation can be measured, and the test accuracy is high.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions: a vibration characteristic test device of a sawtooth shroud blade with adjustable pre-twist angle, comprising:

[0009] Sawtooth crown blades, clamping mechanism and loading mechanism;

[0010] The serrated crown blade is a simplified blade, with the blade body perpendicular to the crown and the base of the blade;

[0011] The loading mechanism is composed of a push piece assembly and a torsion disk. The push piece assembly is divided into a first push piece and a second push piece, which are respectively located on both sides of the working surface of the sawtooth crown and are in close contact with the working surface. They are installed and fixed on the surface of the torsion disk. An annular groove is provided on the surface of the torsion disk, which can only be twisted after cooperating with the clamping mechanism. A sliding groove is provided on the side for the push piece to slide and press against the working surface of the sawtooth crown.

[0012] The clamping mechanism includes a base, a blade clamping end and a torsion disk clamping end;

[0013] Among them, the blade clamping end has the function of fixing the serrated crown blade, and the torsion disk clamping end has the function of fixing the loading mechanism; the base is provided with a sliding groove for the blade clamping end assembly and the torsion disk clamping end assembly to adjust the distance so that the working surface of the serrated crown is aligned with the working surfaces of the first push plate and the second push plate.

[0014] As a preferred solution of the vibration characteristic test device of the serrated crown blade with adjustable pre-twist angle described in the present invention, symmetrical bolt holes are opened at the root base of the blade body of the serrated crown blade, and the serrated crown blade is fixedly installed on the side of the blade clamping end by tightening the external hexagonal bolts.

[0015] As a preferred solution of the vibration characteristic test device of the sawtooth crown blade with adjustable pre-twist angle described in the present invention, wherein: symmetrical bolt holes are opened on the bottom surface of the blade clamping end, and the blade clamping end is fixedly installed on the base by tightening the T-shaped bolt-M12, and symmetrical bolt holes are opened on the side to install and fix the sawtooth crown blade; symmetrical bolt holes are opened on the bottom surface of the torsion disk clamping end, and the torsion disk clamping end is fixed to the base by tightening the T-shaped bolt.

[0016] As a preferred solution of the vibration characteristic test device of the serrated blade crown with adjustable pre-twist angle described in the present invention, symmetrical bolt holes are opened on the side of the torsion disk clamping end, which are aligned with the annular symmetrical grooves of the torsion disk, and the torsion disk is fixed to the torsion disk clamping end by tightening the hexagonal flange bolt and nut assembly.

[0017] As a preferred solution of the sawtooth crown blade vibration characteristic test device with adjustable pre-twist angle described in the present invention, the loading mechanism includes a torsion disk and a push plate assembly; the torsion disk is provided with a circular hole for the external steel wire rope to be wound and tightened to apply tension; annular grooves are provided on both sides to prevent the torsion disk from moving up, down, left and right, and after cooperating with the clamping end of the torsion disk, it can only rotate around the center of the torsion disk; an L-shaped groove is provided on the top for the installation of an angle measuring instrument.

[0018] As a preferred solution of the sawtooth crown blade vibration characteristics test device with adjustable pre-twist angle described in the present invention, the push plate assembly in the loading mechanism includes two push plates, which are divided into a first push plate and a second push plate. The first push plate and the second push plate respectively have two bolt holes for fixing the push plates on the torsion disk.

[0019] As a preferred solution of the serrated crown blade vibration characteristic test device with adjustable pre-twist angle described in the present invention, T-shaped grooves are opened on both sides of the torsion disk, and the push plates can be allowed to slide normally on the working surface of the serrated crown by inserting T-shaped bolts-M63-2 and cooperating with the bolt holes of the first push plate and the second push plate. The positions of the first push plate and the second push plate are adjusted so that the working surfaces of the first push plate and the second push plate are pressed against the working surface of the serrated crown, and the push plates are fixed to the torsion disk by tightening the T-shaped bolt-M63-2 nut assembly.

[0020] As a preferred solution of the serrated crown blade vibration characteristic test device with adjustable pre-twist angle described in the present invention, the base is provided with a T-shaped slot for adjusting the distance between the blade clamping end assembly and the torsion disk clamping end assembly so that the working surface of the serrated crown is aligned with the working surfaces of the first push plate and the second push plate, and the blade clamping end assembly and the torsion clamping end assembly are fixed to the base by tightening the T-shaped bolt and nut assembly.

[0021] As a preferred solution of the vibration characteristic test device of the sawtooth shroud blade with adjustable pre-twist angle of the present invention, the test method of the vibration characteristic test device of the sawtooth shroud blade with adjustable pre-twist angle comprises the following steps:

[0022] S1. Place the basic stand on the basic platform, and install the Jingyan dual-axis electronic level on the "L"-shaped groove above the torsion disk. The internal magnetic sheet can be adsorbed on the "L"-shaped groove to measure the torsion angle;

[0023] S2. Install Fuji pressure-sensitive test paper on the working surface of the serrated crown between the first push piece and the second push piece to collect the average contact pressure of the working surface of the serrated crown. The pressure-sensitive test paper has different ranges when measuring different pressures. In actual tests, finite element simulation calculations are performed on the pre-twisted serrated crown blades in advance. According to the simulation calculation results of the average contact pressure between the working surfaces of the serrated crowns, pressure-sensitive test papers with different ranges are selected.

[0024] S3. Use the hexagonal flange bolts and T-bolts-M12 to fix the torsion plate clamping end and the torsion plate at the specified position on the base in advance; then slide the first push plate and the second push plate along the torsion plate slide groove until they are pressed against the working surface of the serrated crown blade, and tighten the T-bolt-M6 assembly; loosen the hexagonal flange bolts, and fix the loading device to the test benches on both sides through the through holes on the left and right sides of the torsion plate;

[0025] S4, attaching an acceleration sensor for monitoring to the back of the blade to monitor the acceleration change in the direction perpendicular to the blade;

[0026] S5. The left and right loading devices apply tension at the same time. At this time, the torsion disk is subjected to clockwise torque, which drives the pusher and the blade crown of the serrated crown blade to twist around the center of the torsion disk. Observe the angle measuring instrument above the torsion disk. When the torsion angle required by the test is reached, stop applying tension, tighten the hexagonal flange bolts, and finally remove the angle measuring instrument and the loading device.

[0027] S6. Connect and install the signal acquisition instrument and calibrate the DASP vibration test and analysis system. The internal debugging process of the DASP system is to establish a blade geometry model, set the test frequency range, boundary constraints and sampling frequency control;

[0028] S7. According to the actual size of the blade, select the appropriate number of points on the blade body for force hammer excitation. According to the excitation point number, hit each point 4 times. Use modal analysis software to collect 4 responses and take the average to obtain the response curve and calculate the frequency response function.

[0029] S8, performing curve fitting, measurement direction processing, constraint equation processing and vibration mode normalization processing based on the frequency response function obtained at each point, obtaining the modal results of each order of the simplified blade, and generating vibration mode animation;

[0030] S9. Repeat the operations from step S6 to step S8 for three times, and record the test data each time. Finally, take the group with better frequency correlation test as the test data under the current test conditions.

[0031] Beneficial effects of the present invention:

[0032] 1. The vibration characteristic test device of the serrated crown blade with adjustable pre-twist angle of the present invention can realize the vibration characteristic measurement of the serrated crown blade at different torsion angles, and can provide a basis for verification and improvement of theoretical analysis results; if the size of the test blade is slightly adjusted, the vibration characteristic measurement of the serrated crown blade by other key parameters can also be realized, and the flexibility and variability are very high.

[0033] 2. The vibration characteristic test device of the sawtooth crown blade with adjustable pre-twist angle of the present invention is mainly designed in a horizontal direction, which brings convenience to the vibration characteristic measurement of the blade with sawtooth crown. The sawtooth push piece design can truly simulate the actual assembly of the sawtooth crown. The whole test device has a reasonable structure and high precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0035] Figure 1 It is a schematic diagram of the structure of the present invention;

[0036] Figure 2 Schematic diagram of the loading process of the sawtooth crown blade of the present invention;

[0037] Figure 3 It is a comparison diagram between the test results and the simulation results of each vibration mode of the straight blade tested at a torsion angle of 1° in the present invention;

[0038] Figure 4 It is a comparison chart of the test results and simulation results of each order frequency of the straight blade tested at a twist angle of 0.05°-2° of the present invention;

[0039] Figure 5 It is a comparison chart between the simulation results and the test results of the average pressure on the working surface of the serrated crown at a torsion angle of 0.3°-2° of the present invention. DETAILED DESCRIPTION

[0040] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0041] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0042] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0043] Secondly, the present invention is described in detail with reference to the schematic diagram. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0044] Reference Figure 1-Figure 5, a vibration characteristic test device for a sawtooth shroud blade with an adjustable pre-twist angle is provided, comprising:

[0045] Sawtooth crown blade 1, clamping mechanism 2 and loading mechanism 3;

[0046] The serrated crown blade 1-1 is a simplified blade, and the blade body is perpendicular to the blade crown and the blade base 2-1;

[0047] The loading mechanism is composed of a push piece 3-1 assembly and a torsion disk 3-3. The push piece 3-1 assembly is divided into a first push piece 3-1 (a) and a second push piece 3-1 (b), which are respectively located on both sides of the working surface of the sawtooth crown and are in close contact with the working surface and are fixed on the surface of the torsion disk 3-3. The surface of the torsion disk 3-3 is provided with an annular groove, which can only be twisted after cooperating with the clamping mechanism. A sliding groove is provided on the side for the push piece 3-1 to slide and press against the working surface of the sawtooth crown.

[0048] The clamping mechanism includes a base 2-1, a blade clamping end 2-4 and a torsion disk clamping end 2-6;

[0049] Among them, the blade clamping end 2-4 has the function of fixing the serrated crown blade, and the torsion disk clamping end 2-6 has the function of fixing the loading mechanism; the base 2-1 is provided with a slide groove for the blade clamping end assembly and the torsion disk clamping end assembly to adjust the distance so that the working surface of the serrated crown is aligned with the working surface of the first push plate (3-1(a)) and the second push plate (3-1(b)).

[0050] Among them, the root base of the blade body in the serrated crown blade 1-1 is provided with symmetrical bolt holes, and the serrated crown blade 1-1 is fixedly installed on the side of the blade clamping end 2-4 by tightening the external hexagonal bolt 2-3. Furthermore, the bottom surface of the blade clamping end 2-4 is provided with symmetrical bolt holes, and the blade clamping end 2-4 is fixedly installed on the base 2-1 by tightening the T-shaped bolt-M122-2. The side surface is provided with symmetrical bolt holes, which can install and fix the serrated crown blade 1-1; the bottom surface of the torsion disk clamping end is provided with symmetrical bolt holes, and the torsion disk clamping end 2-6 is fixed to the base 2-1 by tightening the bolt T-shaped bolt. Specifically, the side surface of the torsion disk clamping end 2-6 is provided with symmetrical bolt holes, which are aligned with the annular symmetrical groove of the torsion disk, and the torsion disk 3-3 is fixed on the torsion disk clamping end 2-6 by tightening the hexagonal flange bolt 2-5 nut assembly.

[0051] The loading mechanism includes a torsion disk 3-3 and a push plate 3-1 assembly; the torsion disk 3-3 is provided with a circular hole for the external steel wire rope to be wound and tightened to apply tension; annular grooves are provided on both sides to prevent the torsion disk 3-3 from moving up, down, left and right, and after cooperating with the torsion disk clamping end 2-6, it can only rotate around the center of the torsion disk; an L-shaped groove is provided on the top for the installation of an angle measuring instrument.

[0052] Specifically, the push plate assembly in the loading mechanism includes two push plates, which are divided into a first push plate 3-1 (a) and a second push plate 3-1 (b). The first push plate 3-1 (a) and the second push plate 3-1 (b) are respectively provided with two bolt holes for the push plate 3-1 to be fixed on the torsion plate 3-3. More specifically, T-shaped grooves are provided on both sides of the torsion plate 3-3. By inserting T-shaped bolts-M63-2 and cooperating with the bolt holes of the first push plate 3-1 (a) and the second push plate 3-1 (b), the push plate 3-1 can slide normally on the working surface of the serrated crown. The positions of the first push plate 3-1 (a) and the second push plate 3-1 (b) are adjusted so that the working surfaces of the first push plate 3-1 (a) and the second push plate 3-1 (b) are pressed against the working surface of the serrated crown. The push plate 3-1 is fixed on the torsion plate 3-3 by tightening the T-shaped bolt-M63-2 nut assembly.

[0053] The base 2-1 is provided with a T-shaped groove for adjusting the distance between the blade clamping end assembly and the torsion disk clamping end assembly so that the working surface of the serrated crown is aligned with the working surface of the first push plate 3-1 (a) and the second push plate 3-1 (b). By tightening the T-shaped bolt and nut assembly, the blade clamping end assembly and the torsion clamping end assembly are fixed to the base 2-1.

[0054] An experimental device and method for vibration characteristics of a sawtooth shroud blade based on an adjustable pre-twist angle, comprising the following steps:

[0055] S1. Place the base frame on the base platform, and install the Jingyan dual-axis electronic level on the "L"-shaped groove above the torsion disk. The internal magnetic sheet can be adsorbed on the "L"-shaped groove to measure the torsion angle.

[0056] S2. Install Fuji pressure-sensitive test paper on the working surface of the serrated crown between the first push piece 3-1 (a) and the second push piece 3-1 (b) to collect the average contact pressure of the working surface of the serrated crown. The pressure-sensitive test paper has different ranges when measuring different pressures. In actual tests, finite element simulation calculations can be performed on the pre-twisted serrated crown blades in advance, and pressure-sensitive test papers of different ranges can be selected based on the simulation calculation results of the average contact pressure between the working surfaces of the serrated crowns;

[0057] S3. Pre-fix the torsion plate clamping end 2-6 and the torsion plate 3-3 at the specified position on the base 2-1 using the hexagonal flange bolts 2-5 and T-bolts-M122-2; then slide the first push piece 3-1(a) and the second push piece 3-1(b) along the torsion plate slide groove until they are pressed against the working surface of the serrated crown blade, and tighten the T-bolt-M63-2 assembly; loosen the hexagonal flange bolts 2-5, and fix the loading device to the test benches on both sides through the through holes on the left and right sides of the torsion plate 3-3.

[0058] S4, attaching an acceleration sensor for monitoring to the back of blade 1-1 to monitor the acceleration change in the direction perpendicular to the blade;

[0059] S5. The left and right loading devices apply tension at the same time. At this time, the torsion disk 3-3 is subjected to clockwise torque, driving the push piece 3-1 and the blade crown of the serrated crown blade 1-1 to twist around the center of the torsion disk; observe the angle measuring instrument above the torsion disk. When the torsion angle required by the test is reached, stop applying tension and tighten the hexagonal flange bolt 2-5; finally, remove the angle measuring instrument and the loading device. The schematic diagram of the loading process of the serrated crown blade is shown in Figure 1. Figure 4 shown.

[0060] S6. Connect and install the signal acquisition instrument and calibrate the DASP vibration test and analysis system. The internal debugging process of the DASP system is to establish the blade geometry model, set the test frequency range, boundary constraints and sampling frequency control, etc.

[0061] S7. According to the actual size of the blade, select the appropriate number of points on the blade body for force hammer excitation. According to the excitation point number, hit each point 4 times. Use modal analysis software to collect 4 responses and take the average to obtain the response curve and calculate the frequency response function.

[0062] S8, performing curve fitting, measurement direction processing, constraint equation processing and vibration mode normalization processing based on the frequency response function obtained at each point, obtaining the modal results of each order of the simplified blade, and generating vibration mode animation;

[0063] S9. Repeat the operations from step S6 to step S8 for three times, and record the test data each time. Finally, take the group with better frequency correlation test as the test data under the current test conditions.

[0064] Figure 3 The figure is a comparison of the test results and simulation results of each order vibration mode of the straight blade under the 1° torsion angle of the present invention, where the right side is the experimental result and the left side is the simulation result. The test vibration mode of the straight blade under the 1° torsion angle is very similar to the simulation vibration mode, and the simulation vibration mode is easier to identify the vibration mode at each order frequency.

[0065] Figure 4 This is a comparison chart of the test results and simulation results of each order frequency of the straight blade tested at a torsion angle of 0.05°-2° in the present invention. The maximum error between the simulation frequency and the test frequency of each order frequency of the straight blade tested at a torsion angle of 0.05°-2° is 7.1%, and the overall error of the first bend frequency and the second bend frequency does not exceed 5%.

[0066] Figure 5The figure is a comparison chart of the simulation results and the test results of the average pressure on the working surface of the serrated crown at a torsion angle of 0.3°-2° of the present invention. As the torsion angle increases, the test average pressure and the simulation average pressure on the working surface of the serrated crown increase. The maximum error between the simulation average pressure and the test average pressure on the working surface of the serrated crown is 8.71%, which does not exceed the engineering experience error allowance of 10%, indicating that stress calculation of the test blade can accurately predict the average contact pressure on the working surface of the serrated crown.

[0067] The above experimental results show that the experimental device of the present invention has a reasonable structure. The experimental device of the present invention is used to conduct vibration characteristic tests on serrated crown blades, which can accurately predict the average contact pressure between the working surfaces of the serrated crowns under the torsion angle and the various frequencies and vibration modes of the serrated crown blades with high accuracy, and can be applied to the vibration characteristic analysis of other blades with serrated crowns.

[0068] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A vibration characteristic test device for sawtooth shroud blades with adjustable pre-twist angle, characterized in that: include: Sawtooth crown blade 1, clamping mechanism 2 and loading mechanism 3; The serrated crown blade (1-1) is a simplified blade, and the blade body is perpendicular to the crown and the blade base (2-1); The loading mechanism is composed of a push piece (3-1) component and a torsion disk (3-3). The push piece (3-1) component is divided into a first push piece (3-1(a)) and a second push piece (3-1(b)), which are respectively located on both sides of the working surface of the sawtooth crown and are in close contact with the working surface and are fixed on the surface of the torsion disk (3-3). The surface of the torsion disk (3-3) is provided with an annular groove, which can only be twisted after cooperating with the clamping mechanism. The side surface is provided with a sliding groove for the push piece (3-1) to slide and press against the working surface of the sawtooth crown. The clamping mechanism comprises a base (2-1), a blade clamping end (2-4) and a torsion disk clamping end (2-6); The blade clamping end (2-4) has the function of fixing the sawtooth crown blade, and the torsion disk clamping end (2-6) has the function of fixing the loading mechanism; the base (2-1) is provided with a slide groove for adjusting the distance between the blade clamping end assembly and the torsion disk clamping end assembly, so that the working surface of the sawtooth crown is aligned with the working surfaces of the first push piece (3-1(a)) and the second push piece (3-1(b)).

2. The vibration characteristic test device of sawtooth shroud blade with adjustable pre-twist angle according to claim 1 is characterized in that: Symmetrical bolt holes are provided at the root base of the blade body of the sawtooth crown blade (1-1), and the sawtooth crown blade (1-1) is fixedly mounted on the side of the blade clamping end (2-4) by tightening the external hexagonal bolts (2-3).

3. The vibration characteristic test device of sawtooth shroud blade with adjustable pre-twist angle according to claim 1, characterized in that: The bottom surface of the blade clamping end (2-4) is provided with symmetrical bolt holes, and the blade clamping end (2-4) is fixedly mounted on the base (2-1) by tightening the T-shaped bolt-M12 (2-2); the side surface is provided with symmetrical bolt holes, and the sawtooth crown blade (1-1) can be installed and fixed; the bottom surface of the torsion disk clamping end is provided with symmetrical bolt holes, and the torsion disk clamping end (2-6) is fixed on the base (2-1) by tightening the T-shaped bolt.

4. The vibration characteristic test device of sawtooth shroud blade with adjustable pre-twist angle according to claim 3 is characterized in that: The side of the torsion disk clamping end (2-6) is provided with symmetrical bolt holes which are aligned with the annular symmetrical grooves of the torsion disk. The torsion disk (3-3) is fixed to the torsion disk clamping end (2-6) by tightening the hexagonal flange bolt (2-5) nut assembly.

5. The vibration characteristic test device of sawtooth shroud blade with adjustable pre-twist angle according to claim 1, characterized in that: The loading mechanism comprises a torsion disk (3-3) and a push plate (3-1) assembly; wherein the torsion disk (3-3) is provided with a circular hole for an external steel wire rope to be wound and tied to apply tension; annular grooves are provided on both sides to prevent the torsion disk (3-3) from moving up, down, left, and right, and after cooperating with the torsion disk clamping end (2-6), the torsion disk can only rotate around the center of the torsion disk; and an L-shaped groove is provided on the top for the installation of an angle measuring instrument.

6. The vibration characteristic test device of sawtooth shroud blade with adjustable pre-twist angle according to claim 1, characterized in that: The push plate assembly in the loading mechanism includes two push plates, which are divided into a first push plate (3-1(a)) and a second push plate (3-1(b)). The first push plate (3-1(a)) and the second push plate (3-1(b)) are respectively provided with two bolt holes for the push plate (3-1) to be fixed on the torsion plate (3-3).

7. The vibration characteristic test device of sawtooth shroud blade with adjustable pre-twist angle according to claim 6, characterized in that: The torsion plate (3-3) is provided with T-shaped grooves on both sides, and the T-shaped bolts-M6 (3-2) are inserted to cooperate with the bolt holes of the first push piece (3-1 (a)) and the second push piece (3-1 (b)) so that the push piece (3-1) can slide normally on the working surface of the sawtooth crown. The positions of the first push piece (3-1 (a)) and the second push piece (3-1 (b)) are adjusted so that the working surfaces of the first push piece (3-1 (a)) and the second push piece (3-1 (b)) are pressed against the working surface of the sawtooth crown, and the push piece (3-1) is fixed to the torsion plate (3-3) by tightening the T-shaped bolt-M6 (3-2) nut assembly.

8. The vibration characteristic test device of sawtooth shroud blade with adjustable pre-twist angle according to claim 1, characterized in that: The base (2-1) is provided with a T-shaped groove for adjusting the distance between the blade clamping end assembly and the torsion disk clamping end assembly so that the working surface of the serrated crown is aligned with the working surfaces of the first push plate (3-1(a)) and the second push plate (3-1(b)). The blade clamping end assembly and the torsion clamping end assembly are fixed to the base (2-1) by tightening the T-shaped bolt and nut assembly.

9. The vibration characteristic test device of sawtooth shroud blade with adjustable pre-twist angle according to claim 1, characterized in that: The test method of the vibration characteristic test device of the sawtooth shroud blade based on the adjustable pre-twist angle comprises the following steps: S1. Place the basic stand on the basic platform, and install the Jingyan dual-axis electronic level on the "L"-shaped groove above the torsion disk. The magnetic sheet inside can be adsorbed on the "L"-shaped groove to measure the torsion angle; S2. Install Fuji pressure-sensitive test paper on the working surface of the serrated crown between the first push piece (3-1(a)) and the second push piece (3-1(b)) to collect the average contact pressure of the working surface of the serrated crown. The pressure-sensitive test paper has different ranges when measuring different pressures. During the actual test, finite element simulation calculations are performed on the pre-twisted serrated crown blades in advance. According to the simulation calculation results of the average contact pressure between the working surfaces of the serrated crowns, pressure-sensitive test papers with different ranges are selected. S3. Pre-fix the torsion plate clamping end (2-6) and the torsion plate (3-3) at the designated position on the base (2-1) using the hexagonal flange bolts (2-5) and the T-bolts-M12 (2-2); then slide the first push piece 3-1 (a) and the second push piece 3-1 (b) along the torsion plate slide groove until they are pressed against the working surface of the sawtooth crown blade, and tighten the T-bolt-M6 (3-2) assembly; loosen the hexagonal flange bolts (2-5), and fix the loading device on the test benches on both sides through the through holes on the left and right sides of the torsion plate (3-3); S4, attaching an acceleration sensor for monitoring to the back of the blade (1-1) to monitor the acceleration change in the direction perpendicular to the blade; S5. The left and right loading devices simultaneously apply tension, and the torsion disk (3-3) is subjected to a clockwise torque, driving the push piece (3-1) and the blade crown of the sawtooth crown blade (1-1) to twist around the center of the torsion disk; observe the angle measuring instrument above the torsion disk, and when the torsion angle required by the test is reached, stop applying tension, tighten the hexagonal flange bolt (2-5), and finally remove the angle measuring instrument and the loading device; S6. Connect and install the signal acquisition instrument and calibrate the DASP vibration test and analysis system. The internal debugging process of the DASP system is to establish a blade geometry model, set the test frequency range, boundary constraints and sampling frequency control; S7. According to the actual size of the blade, select the appropriate number of points on the blade body for force hammer excitation. According to the excitation point number, hit each point 4 times. Use modal analysis software to collect 4 responses and take the average to obtain the response curve and calculate the frequency response function. S8, performing curve fitting, measurement direction processing, constraint equation processing and vibration mode normalization processing based on the frequency response function obtained at each point, obtaining the modal results of each order of the simplified blade, and generating vibration mode animation; S9. Repeat the operations from step S6 to step S8 for three times, and record the test data each time. Finally, take the group with better frequency correlation test as the test data under the current test conditions.

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