A method for testing the rotating excitation of a high-pressure turbine blade of an aero-engine

Abstract

The application belongs to the field of rotating excitation test, and is a rotating excitation test method for high-pressure turbine blades of an aero-engine. A certain number of to-be-tested blades are randomly selected, then all blade assembly positions in the wheel disc circumferential direction are partitioned according to the number of the to-be-tested blades, each to-be-tested blade is assembled to the center position of a partition, and according to the frequency difference setting requirement, test blades are assembled on both sides of the to-be-tested blade. Then, the first rotating excitation test under the condition of no damping and the second rotating excitation test under the condition of damping are carried out, and the test blades are screened according to the frequency, so that resonance can be generated between the test blades and the to-be-tested blades, and the signal-to-noise ratio of the large-stiffness high-pressure turbine blade in the rotating excitation test dynamic stress test can be effectively improved. By comparing the vibration responses of the same blade in two rounds of tests under different damping states, the damping effect of the current type of damping sheet in blade vibration suppression can be effectively evaluated.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of aero-engine rotating excitation test, and particularly relates to a rotating excitation test method for a high-pressure turbine blade of an aero-engine. BACKGROUND

[0002] With the emergence of high-performance turbines and compressors, high-cycle fatigue fracture of gas turbine blades has become a major failure mode. Higher rotor speeds, closer interstage distances, smaller weights, varied struts and increasing aerodynamic work of individual blades all cause more blade resonance modes to be excited under normal operating conditions.

[0003] Due to cost issues, it is unrealistic to solve the entire high-cycle fatigue problem by means of engine whole-machine tests. Therefore, a dynamic rotating test bench with an excitation system provides a method for solving this problem. With a reliable high-cycle fatigue excitation system, the dynamic rotating test bench can simulate the static and dynamic environment of the engine flow passage in addition to the aerodynamic load. The rotational speed, temperature field and excitation factors can be simulated simultaneously to determine the rotor stage blade response and potential high-cycle fatigue failure and provide evaluation parameters for changing the design at the early stage of engine development, reduce the development cost of the engine and shorten the development cycle.

[0004] The liquid jet excitation method is to arrange a series of nozzles around the test rotor, with the nozzle tips facing the blades. In the test, the misty liquid continuously sprayed from the nozzles impacts the specified positions of the rotating blades. When the liquid contacts the rotating blades, the kinetic energy of the liquid will generate an impact force on the blades. The circumferentially uniformly distributed fixed nozzles form an excitation force of a specific frequency relative to the blades of the rotating wheel disc. By controlling the number of nozzles and the rotational speed of the rotor, the resonance response of the specific mode of the blades will be generated; by controlling the flow and pressure of the liquid at the nozzles, the amplitude of the excitation force can be adjusted, and thus the size of the resonance response can be controlled.

[0005] The high-cycle fatigue excitation system of the dynamic rotating test bench includes a driving shaft 1, an excitation test piece 2 coupled to the output end of the driving shaft 1, an excitation load applying device 3 for applying a load to the test piece, and an oil circulation system, which can simulate the excitation sources of the blades under the working condition of the engine, i.e. engine orders such as the number of leading edge working blades, the number of trailing edge working blades, the number of combustion chamber nozzles and the number of inlet struts, as shown in Figure 1 The excitation load applying device 3 currently includes an inner ring 4, an outer ring 5 and an oil nozzle sliding rod assembly 6 arranged between the inner ring 4 and the outer ring 5, which can fix the circumferential position of each oil nozzle sliding rod assembly 6 between the inner and outer rings, ensure the stable flow of the excitation oil on each oil nozzle sliding rod assembly 6, and the entire device has the ability to freely adjust the entire engine orders, and the circumferential position of the oil nozzles can be freely adjusted without disassembling the test piece, forming the target engine order excitation source, as shown in Figure 2The driving shaft assembly and the excitation test piece are coupled through flanges and a stop opening. The same excitation test piece can be switched between leading edge excitation and trailing edge excitation without changing the design of the driving shaft assembly, as shown in Figure 3

[0006] The prior art has the following disadvantages:

[0007] Technical aspects

[0008] The existing test device can realize liquid excitation vibration of the engine rotor blade, and is used for studying the damping characteristics of part of the rotor blade of an aero-engine, such as a fan rotor blade and a compressor rotor blade. The existing test method is to uniformly select a plurality of to-be-tested blades on the aero-engine wheel disc in the circumferential direction, paste strain gauges, and part of the to-be-tested blades are provided with damping structures, and the remaining to-be-tested blades are not provided with damping structures. After the to-be-tested blades are assembled into an assembly with the wheel disc, the lead wires are introduced, and the assembly is installed on a rotary excitation tester. The signal line is fixed to a slip ring power supply, and the signal is regulated to carry out formal test. After data analysis, the vibration response of the blade with the damping structure and the blade without the damping structure is obtained, and the vibration suppression effect of the damping on the vibration response of the blade is evaluated.

[0009] However, due to the assembly state of the blade and the wheel disc, the assembly state of the damping structure and the blade, the change of the matching condition in the high-speed rotation process, and the vibration response of the adjacent blades, the vibration characteristics of different measured blades often have great differences.

[0010] For a high-pressure turbine, a damping sheet is usually assembled between two adjacent high-pressure turbine blades to reduce vibration of the high-pressure turbine blades. However, the damping effect of damping sheets of different structures differs greatly, and it is not possible to screen damping structures one by one by using the whole machine test method. Compared with fan rotor blades and compressor rotor blades, the high-pressure turbine blade has large stiffness, and the vibration response under the rotary excitation condition is often very small, which is not conducive to the comparative study of damping vibration characteristics. Therefore, at present, there is still no perfect rotary excitation test method for high-pressure turbine blades.

[0011] Cost aspects

[0012] The existing test method is found through in-depth demonstration and test verification that the comparative vibration response level between different blades (blades with damping and blades without damping) cannot represent the real damping vibration suppression level. The test process from blade patching, assembly of lead wires to formal test consumes huge manpower and material resources, and cannot obtain the real damping vibration suppression level.

[0013] Efficiency aspects

[0014] ​The blades to be tested are selected so that the assembly state with the engine wheel disc and the cooperation state with the damping sheet are close to each other. Complicated evaluation criteria need to be formulated, and tedious measurement and screening are required, and the assembly process flow cannot be implemented, which affects the test efficiency.

[0015] Therefore, how to ensure the signal-to-noise ratio of the high-pressure turbine blade rotating excitation test and improve the test efficiency is a problem to be solved. SUMMARY

[0016] The purpose of the present application is to provide an aero-engine high-pressure turbine blade rotating excitation test method to solve the problem of inaccurate existing aero-engine rotor blade rotating excitation test method, in particular, low signal-to-noise ratio of dynamic stress test signal of high-pressure turbine blade and low test efficiency.

[0017] The technical solution of the present application is: an aero-engine high-pressure turbine blade rotating excitation test method, comprising:

[0018] First, test and record the bending frequency of all blades in the tested blades. According to the number of current channels and the number of test leads allowed to pass through the inner hole of the rotating excitation tester drive shaft, the number of blades to be tested is determined, and the blades to be tested are randomly selected.

[0019] According to the number of blades to be tested, the assembly positions of all blades in the circumferential direction of the wheel disc are evenly partitioned. When the circumferential position of the wheel disc cannot be evenly partitioned, the number of blades in different partitions is allowed to differ by 1 piece (including 1 piece).

[0020] The blades to be tested are assembled to the center of each partition, and the test blades are assembled on both sides of the blades to be tested. The frequency difference between the test blades and the center blades to be tested in each partition is required to be within a certain range, and the assembly position of all blades in the circumferential direction of the wheel disc is recorded after assembly. When the number of blades in a certain partition is even, the blades to be tested can be selected at any two positions closest to the center of the entire partition.

[0021] In the first assembly, all blade positions in the circumferential direction of the wheel disc are not installed with damping sheets, and after all blades in the circumferential direction of the wheel disc are installed, the assembly position of all blades in the circumferential direction of the wheel disc is recorded. The first rotating excitation test under the condition of no damping is carried out. The vibration response of each blade to be tested in its resonance speed range is obtained. After the first test is completed, the test assembly will be disassembled.

[0022] In the second assembly, all blade positions in the circumferential direction of the wheel disc are installed with damping sheets, and all blades in the circumferential direction are installed at the positions recorded in the first assembly according to the blade assembly positions recorded in the first assembly. The second rotating excitation test under the condition of damping is carried out. The vibration response of each blade to be tested in its resonance speed range is obtained.

[0023] Through comparative analysis, the vibration response change amplitude of each to-be-tested blade in the two rounds of tests is obtained, and through data statistics, the average value, maximum value and minimum value of the vibration response change amplitude of all to-be-tested blades are obtained, so that the damping effect of the current type damping sheet can be effectively evaluated.

[0024] Preferably, the frequency difference between the test blade and the center to-be-tested blade in each subzone is required to be less than 0.2%.

[0025] Preferably, in the process of assembling the to-be-tested blades, the positions of the to-be-tested blades where faults occur in the use of the engine and the root positions of the blades are determined, and then strain gauges are pasted on the fault positions and the root positions of the to-be-tested blades respectively, and after the pasting of the strain gauges is completed, dynamic stress test leads are installed on each to-be-tested blade and oil-proof protection measures are taken.

[0026] The method for the rotating excitation test of the high-pressure turbine blade of the aero-engine provided in the application comprises the following steps: firstly, a certain number of to-be-tested blades are selected according to the hardware conditions of the tester; secondly, the assembly positions of all the blades in the circumferential direction of the wheel disc are divided into subzones according to the number of the to-be-tested blades, each to-be-tested blade is assembled to the center position of each subzone, and the test blades are selected according to the frequency difference setting range requirement and assembled on both sides of the to-be-tested blades; thirdly, the first round of rotating excitation test under the condition of no damping and the second round of rotating excitation test under the condition of damping are respectively performed. In the assembly process of the two rounds of excitation tests, all the to-be-tested blades and the test blades are in the same assembly position. Through the method of assembling the blades with close frequencies in the same subzone to perform the rotating excitation test, when the excitation frequency is the same as the frequency of the to-be-tested blade in the subzone, the test rotor is stabilized near the resonance speed, the test blades adjacent to the to-be-tested blade also produce resonance, and the amplitude of the to-be-tested blade is increased. According to this method, the signal-to-noise ratio in the dynamic stress test of the rotating excitation test of the high-stiffness high-pressure turbine blade can be effectively improved, and through the comparison of the vibration responses of the same to-be-tested blade in the two rounds of tests under different damping conditions, the influence of the dispersion difference between the vibration responses of different blades caused by the different assembly tightnesses and other factors can be effectively eliminated. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions provided in the application, the following will briefly introduce the drawings. Obviously, the drawings described below are only some embodiments of the application.

[0028] Figure 1 It is a schematic diagram of the high-cycle fatigue excitation system structure of the dynamic rotating test bench in the background art;

[0029] Figure 2 It is a schematic diagram of the high-cycle fatigue excitation system structure of the dynamic rotating test bench in the background art; Figure 1 It is a schematic diagram of the high-cycle fatigue excitation system structure of the dynamic rotating test bench in the background art;

[0030] Figure 3 A schematic diagram of a variable leading / trailing edge excitation system in the background art;

[0031] Figure 4 A schematic diagram of a partition of an assembly position of the present application;

[0032] Figure 5 A schematic diagram of an assembly position of a blade in a partition of the present application;

[0033] Figure 6 A flowchart of a rotating excitation test of a high-pressure turbine blade of an aero-engine of the present application.

[0034] 1, drive shaft; 2, excitation test piece; 3, full-engine order blade disc excitation load applying device; 4, inner ring; 5, outer ring; 6, oil nozzle sliding rod assembly. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0036] A rotating excitation test method of a high-pressure turbine blade of an aero-engine, comprising the following steps:

[0037] Step S100, selection of high-pressure turbine blades

[0038] In the blades that have passed the factory inspection and are qualified, the first bending frequency of all the blades is tested and recorded, so as to facilitate the subsequent selection of test blades. Then, the number of test blades is determined according to the number of current channels and the number of test leads allowed to pass through the inner hole of the drive shaft of the rotating excitation tester. A certain number of test blades are randomly selected. In an embodiment, the number of test blades is 12, and all the assembly positions of the wheel disc in the circumferential direction are divided into 12 zones, as shown in FIG. 1. The number of test blades is an integer multiple of the number of test blades, such as 4 times or 6 times, etc. Figure 4

[0039] Step S200, assembly of high-pressure turbine blades

[0040] All the assembly positions of the blades in the circumferential direction of the wheel disc are evenly partitioned according to the number of test blades. When the circumferential positions of the wheel disc cannot be evenly partitioned, the number of blades in different partitions is allowed to differ by 1 piece (including 1 piece).

[0041] ​Each test blade is assembled to a subzone center, and test blades are assembled on both sides of the test blade, and the frequency difference between each subzone test blade and the test blade in the subzone is controlled within a set range, and the assembly position of all the blades in the circumferential direction of the wheel disc is recorded after the assembly is completed. When the number of blades in a subzone is even, the test blade can be selected at any two positions closest to the center of the entire subzone.

[0042] Preferably, the frequency difference between each subzone test blade and the center test blade is not more than 0.2%, so as to ensure that the test blades in the same subzone can resonate with the center test blade in the subzone in the rotary excitation test.

[0043] In an embodiment, the wheel disc 1 contains 7 assembly positions, and the A4 assembly position is assembled with a test blade (pasting strain gauges), and the remaining 6 blades are assembled with test blades (not pasting strain gauges), as shown in Figure 5 .

[0044] In combination Figure 6 When pasting the strain gauges, the position of the test blade that fails in engine use and the root position of the blade itself are determined, and then strain gauges are pasted at the failure position and the root position of the test blade, respectively. After the strain gauges are pasted, a dynamic stress test lead is installed for each test blade, and an oil-proof protection measure is applied. In the rotary excitation test, each test blade can obtain vibration response data of two positions, so as to obtain the relationship between the stress level at the failure position and the stress level at the root position of the blade. In the dynamic stress test process, when any position of the strain gauge fails or any channel of the electric lead fails, the overall vibration response level of the blade can be evaluated through the vibration response data of other positions of the blade, thereby improving the reliability of the dynamic stress test.

[0045] After the strain gauges of the test blade are pasted, the test rotor needs to be assembled and balanced, and then the test rotor containing the test blade and the test blade is installed to the rotary excitation tester. The leads of each dynamic stress test channel need to be welded to the slip ring electric lead through the hollow drive shaft, so as to realize the signal transmission between the rotor and the stator. Then, the test signal conditioning under the static condition of the test rotor is carried out to ensure stable transmission of the test signal and accurate calibration. After the test signal conditioning under the static condition of the test rotor is completed, the test rotor needs to be debugged and run in the full speed range specified in the test without oil excitation, to verify the balancing effect of the test rotor. When the vibration level of the test rotor is within the equipment vibration limit value range, the test rotor can be subjected to the high-pressure turbine blade rotary excitation test in the oil excitation state, and the test results are obtained through the strain gauges for subsequent test analysis.

[0046] When the excitation frequency is the same as the frequency of the blade to be tested, the test rotor is stable near the resonance speed, and the adjacent test blade will also produce resonance, thereby increasing the amplitude of the blade to be tested. Through this method, the vibration response of the large stiffness high pressure turbine blade can be effectively improved, the signal-to-noise ratio of the large stiffness high pressure turbine blade in the rotating excitation test dynamic stress test is improved, and the damping vibration reduction characteristic comparison research is beneficial.

[0047] At the same time, by using the blade frequency to be tested as the standard to select the test blade, the cumbersome blade disc size measurement and unnecessary assembly state inspection are avoided, the assembly process flow is simplified, and the test efficiency is improved.

[0048] Step S300, first round of rotating excitation test under non-damping condition

[0049] In the first assembly, no damping sheet is installed at all blade positions in the circumferential direction of the disc, and after all the blades in the circumferential direction of the disc are installed, the assembly positions of all the blades in the circumferential direction of the disc are recorded. Then, the rotating excitation test under the non-damping condition is carried out on the assembled blade to be tested, and the vibration response of each blade to be tested in the resonance speed range is obtained.

[0050] By recording the assembly positions of all the blades in the circumferential direction of the disc, when the disc is assembled again, the blades can still be assembled to the original positions, and all the blades in each partition of the disc can still be in the same assembly state regardless of the number of rotating excitation tests.

[0051] Step S400, second round of rotating excitation test under damping condition

[0052] Due to the influence of the tightness of the blade and the disc, the damping effect of the damping sheet between different blades has certain differences, and the vibration response between different blades cannot effectively evaluate the damping effect of the damping sheet, so two rounds of rotating excitation tests with different damping states are required without changing the assembly positions of the blades.

[0053] The assembly steps of the first round of rotating excitation test and the second round of rotating excitation test are designed to be exactly the same, so that the blades to be tested can be in the same assembly state under non-damping and damping conditions.

[0054] After the first round of tests, the test pieces are disassembled, all the test blades and the test blades are cleaned, the dynamic stress test leads and the oil-proof protective coating on the surface of the disc are cleaned, then the strain gauges are pasted again on all the test blades according to the strain gauge pasting position determined in the first round of rotating excitation tests, the dynamic stress test leads are installed and the oil-proof protection measures are taken. Then the damping pieces are assembled on each test blade and test blade, and the test blades and test blades are assembled on the disc again, and the second rotating excitation test under the condition of damping is carried out, the vibration response of each test blade in the resonance speed range is obtained, and the vibration response of each test blade in the first round is compared and analyzed, and the damping effect of the current type damping piece is evaluated.

[0055] In the first and second rotating excitation tests, the vibration response change amplitude of each test blade in the front and rear two tests is obtained by comparative analysis, and through data statistics, the average value, maximum value and minimum value of the vibration response change amplitude of all test blades are obtained, that is, the damping effect of the current type damping piece can be effectively evaluated.

[0056] The test blades for test result comparison and analysis are in the same position, the same working state in the front and rear two rotating excitation tests, and the working environment is basically the same except the damping piece, so that the interference factors can be effectively ruled out. By comparing the vibration responses of the same test blade in two rotating excitation tests under different damping states, the influence of the dispersion difference between different blades caused by different assembly tightness and other factors can be effectively excluded.

[0057] Through the design of rotating excitation test on blade selection, blade assembly, strain gauge pasting, test debugging and formal test, the rotating excitation test process of high-pressure turbine blade of aero-engine is formed, as shown in Figure 6 .

[0058] When selecting the corresponding test blade, since the vibration characteristics of different test blades are not compared with each other, but the vibration characteristics of the same test blade in different states are compared, when designing the rotating excitation test of high-pressure turbine blade, complex blade selection evaluation standard does not need to be formulated, and tedious assembly state measurement does not need to be carried out, the assembly state between the test blade and the disc and the assembly state between the damping piece and the test blade do not need to be adjusted, so that the test efficiency and the realizability of the rotating excitation test assembly process of high-pressure turbine blade can be effectively improved. The consistency boundary conditions such as the same assembly state and the same load state are realized, the rotating excitation test of high-pressure turbine blade is carried out, and the damping vibration reduction effect of high-pressure turbine blade can be effectively verified.

[0059] Finally should be explained a few points are: first, in the description of the present application, it should be pointed out that, unless otherwise specified and limited, the term "installation", "connected", "connection" should be broad, can be mechanical or electrical connection, but also can be two elements inside the communication, can be directly connected, "up", "down", "left", "right" and so on, only for indicating the relative position relationship, when the absolute position of the described object changes, the relative position relationship may change;

[0060] Second: the present application discloses the embodiment in the drawing, only relates to the structure involved in the present application, other structures can refer to the usual design, in the case of no conflict, the same embodiment and different embodiments of the present application can be combined with each other;

[0061] Finally: the above only for the preferred embodiment of the present application, and not for limiting the present application, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application, should be included in the protection scope of the present application.

Claims

1. A method for rotating vibration testing of high-pressure turbine blades for aero-engines, characterized in that, include: First, test and record the bending frequency of all blades among the blades that have passed the factory inspection; determine the number of blades to be tested based on the number of lead wires and the number of test leads that can pass through the inner hole of the drive shaft of the rotary vibration tester, and randomly select the blades to be tested. The assembly positions of all blades in the circumference of the wheel are evenly divided according to the number of blades to be tested; when the circumference of the wheel cannot be evenly divided, the number of blades between different sections is allowed to differ by one blade. Within each zone, the blade to be tested is assembled to the center of the zone, and the test blades are assembled on both sides of the blade to be tested. When the number of assembly positions in a certain zone is even, the blade to be tested can be selected from any two positions closest to the center of the entire zone. Within each zone, the frequency difference between the test blades and the central blade to be tested is controlled to not exceed the set range. After assembly, the assembly positions of all blades in the circumferential direction of the wheel are recorded. In the first round of assembly, no damping plates are installed at any of the blade positions along the circumference of the wheel. After all the blades along the circumference of the wheel are installed, the assembly positions of all the blades along the circumference of the wheel are recorded. The first round of rotational excitation test under undamped conditions is carried out. The vibration response of each blade under test is obtained within its resonant speed range. After the first round of test is completed, the test assembly will be disassembled. In the second round of assembly, damping plates were installed at all blade positions in the circumferential direction of the disk. According to the blade assembly positions recorded in the first round of assembly, all blades in the circumferential direction were installed at the positions in the first round of assembly. The second round of rotational excitation test under damping conditions was carried out to obtain the vibration response of each blade under test within its resonant speed range. By comparing and analyzing the vibration response changes of each blade under test in the two rounds of testing, and by statistically analyzing the data, the average, maximum and minimum values ​​of the vibration response changes of all blades under test can be obtained, and the vibration reduction effect of the current type of damping sheet can be evaluated.

2. The method for rotating vibration testing of high-pressure turbine blades for aero-engines as described in claim 1, characterized in that: Within each zone, the frequency difference between the test blade and the central test blade must not exceed 0.2%.

3. The method for rotating vibration testing of high-pressure turbine blades for aero-engines as described in claim 1, characterized in that: During the assembly of the blade under test, the location of the fault in the blade during engine use and the root position of the blade itself are determined. Then, strain gauges are attached to the fault location and the root position of the blade under test respectively. After the strain gauges are attached, dynamic stress test leads are installed on each blade under test and oil protection measures are applied. In the rotational vibration test, vibration response data of two parts can be obtained for each blade under test, and the relationship between the stress level at the fault location and the stress level at the blade root position can be obtained. During dynamic stress testing, if a strain gauge fails at any location or a channel of the actuator fails, the overall vibration response level of the blade can be assessed by using vibration response data from other locations on the blade.

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