A high- and low-cycle combined fatigue testing device for aero-engine blades

Abstract

This invention provides a high- and low-cycle combined fatigue testing device for aero-engine blades, comprising a fan and test blades disposed between the upper and lower edges of a wind tunnel; the test blades are mounted on a test disk located outside the lower edge of the wind tunnel, and the test disk is connected to a motor; a front valve is provided between the fan and the test blades, with multiple front nozzles evenly distributed on the front valve; a rear valve is provided at the rear end of the test blades, with multiple rear nozzles evenly distributed on the rear valve. This invention can simulate the low-cycle centrifugal load and high-cycle aerodynamic load experienced by engine blades, and can simulate the effects of different preceding and following stage engine blade excitations on the test engine blades, thereby obtaining the high- and low-cycle combined fatigue life of the aero-engine blades and providing a guarantee for the safe use of aero-engine blades.

Description

Technical Field

[0001] This invention relates to a high- and low-cycle combined fatigue testing device for aero-engine blades, belonging to the field of aero-engine technology, and is applicable to the design of high- and low-cycle fatigue tests for blades. Background Technology

[0002] Fatigue is considered a deadly killer of mechanical components and is one of the main causes of failure in aero-engine parts. While the proportion of fatigue failure modes may differ between civil and military aircraft, and varies at different stages, the proportion of fatigue in aero-engine component failures cannot be underestimated. Fatigue failure of aero-engine blades is caused by repeated loading and is the result of long-term alternating cyclic stress. Aero-engine blades are subjected to two types of alternating cyclic loads throughout their lifespan: one is vibration cyclic load induced by various aerodynamic and mechanical factors. This type of vibration stress has a relatively low amplitude but a high frequency, typically causing the blade to fail within 10... 5 The high-cycle fatigue failure described above is called high-cycle fatigue, which can cause severe damage in a short period of time. Another type is the cyclic load caused by centrifugal force during aircraft takeoff and landing; this type of takeoff and landing cycle often causes the blades to undergo 10 cycles of high-cycle fatigue failure. 5 Low-cycle fatigue failure within a certain range is called low-cycle fatigue.

[0003] Aero-engine blades are subjected to both low-cycle fatigue damage from aircraft takeoff and landing cycles and high-cycle fatigue damage from aerodynamic loads during operation. Their failure mode is often a combined high- and low-cycle fatigue failure, resulting in a significantly shorter combined fatigue life compared to individual low-cycle or high-cycle fatigue lives. Previous low-cycle fatigue tests on blades involved calculating the critical section for the blade's fatigue limit, then calculating the centrifugal load at that section. The blade was then fixed to a bottom clamp, held at a specific section on its tip, and a tensile load was applied through the clamp at the tip. This tensile load was the calculated centrifugal load at the critical section. However, because the centrifugal load varies across the radial sections of the blade, this method can only apply a constant centrifugal load, thus failing to fully simulate the centrifugal load on blades under real engine conditions. Meanwhile, previous high- and low-cycle fatigue tests on blades were conducted separately, making it impossible to apply high- and low-cycle fatigue loads simultaneously on the same blade. The combined high- and low-cycle fatigue life of a blade is much lower than that of individual high- and low-cycle fatigue life. If there were a test method that could apply high- and low-cycle fatigue loads to a blade at the same time to obtain a more realistic blade fatigue life, it would be more beneficial to the safe design of the blade. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a high-low cycle composite fatigue testing device for aero-engine blades. This device can simulate the centrifugal load and aerodynamic load experienced by engine blades, and can also simulate the effects of different excitation sources.

[0005] The present invention is achieved through the following technical solutions.

[0006] The present invention provides a high- and low-cycle combined fatigue testing device for aero-engine blades, comprising a fan and a test blade disposed between the upper edge and the lower edge of a wind tunnel; the test blade is mounted on a test disk located outside the lower edge of the wind tunnel, and the test disk is connected to a motor; a front valve is provided between the fan and the test blade, and multiple front nozzles are evenly distributed on the front valve; a rear valve is provided at the rear end of the test blade, and multiple rear nozzles are evenly distributed on the rear valve.

[0007] The test wheel is connected to the motor via an adapter section.

[0008] The tenon groove of the test wheel is consistent with the tenon groove of the wheel actually used.

[0009] The strength of the test wheel is consistent with that of the wheel used in actual applications.

[0010] The front air nozzles are distributed in a circle around the center of the wind tunnel.

[0011] The rear air nozzles are distributed in a circle around the center of the wind tunnel.

[0012] The fans are distributed in a circle around the center of the wind tunnel.

[0013] The beneficial effects of this invention are: it can simulate the low-cycle centrifugal load and high-cycle aerodynamic load on engine blades, and can simulate the effects of different preceding and following stage engine blade excitations on test engine blades, thereby obtaining the high- and low-cycle combined fatigue life of aero-engine blades and providing a guarantee for the safe use of aero-engine blades. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the present invention;

[0015] Figure 2 A schematic diagram of the arrangement of the front air nozzle and front valve of the present invention;

[0016] Figure 3 This is a schematic diagram of the fan arrangement of the present invention.

[0017] In the diagram: 1-fan, 2-front valve, 3-test blade, 4-rear valve, 5-upper edge of wind tunnel, 6-lower edge of wind tunnel, 7-test wheel, 8-transfer section, 9-motor, 10-front nozzle, 11-rear nozzle. Detailed Implementation

[0018] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0019] Example 1

[0020] like Figures 1 to 3 The device shown is a high-low cycle composite fatigue test device for aero-engine blades, including a fan 1 and a test blade 3 disposed between the upper edge 5 and the lower edge 6 of the wind tunnel; the test blade 3 is mounted on a test wheel 7 located outside the lower edge 6 of the wind tunnel, and the test wheel 7 is connected to a motor 9; a front valve 2 is provided between the fan 1 and the test blade 3, and a plurality of front nozzles 10 are evenly distributed on the front valve 2; a rear valve 4 is provided at the rear end of the test blade 3, and a plurality of rear nozzles 11 are evenly distributed on the rear valve 4.

[0021] The test wheel 7 is connected to the motor 9 via the adapter section 8 (connector).

[0022] The tenon groove of the test wheel 7 is consistent with the tenon groove of the wheel actually used.

[0023] The strength of the test wheel 7 is consistent with the strength of the wheel used in actual applications.

[0024] The front air nozzle 10 is distributed in a circle around the center of the wind tunnel.

[0025] The rear air nozzle 11 is distributed in a circle around the center of the wind tunnel.

[0026] The fans 1 are distributed in a circle around the center of the wind tunnel.

[0027] Specifically, the fan 1 provides aerodynamic force to simulate high-cycle fatigue load, while the motor 9 drives the test wheel 7 and test blade 3 to rotate, providing low-cycle centrifugal load. This allows for a more accurate assessment of the combined high- and low-cycle fatigue life of the engine blades, providing guidance for the safe design of engine blades. At the same time, by changing the opening and closing of the nozzles before and after the test blade 3, this invention can simulate the wake excitation of the front and rear stage blades, and explore the degree of harm of the front and rear stage blade excitation to the resonance of the test blade.

[0028] Furthermore, based on the actual form of the engine condition wheel disk tenon, the test wheel disk 7 is designed. The test wheel disk 7 only needs to ensure that the tenon can be properly assembled with the blade and that the strength is sufficient. Then, the assembled test blade 3 and the test wheel disk 7 are installed on the tester. The test wheel disk 7 is connected to the motor 9 through the adapter section 8. During the test, the motor 9 drives the test wheel disk 7 and the test blade 3 to rotate to apply a low-cycle centrifugal load.

[0029] Example 2

[0030] The scheme of Example 1 is adopted, and:

[0031] Test blades 3 are installed between the upper edge 5 and the lower edge 6 of the wind tunnel. The test blades 3 are mounted on a test disk 7. This test disk 7 does not need to be completely identical to the actual disk; it only needs to ensure that the tenon and groove of the test disk 7 matches the tenon and groove of the actual disk, guaranteeing a consistent mounting environment for the test blades 3 and sufficient strength for the test disk 7. A fan 1 is arranged at the front end of the wind tunnel to provide aerodynamic force, simulating high-cycle aerodynamic loads under real engine conditions. A front valve 2 is set between the fan 1 and the test blades 3, with several front nozzles 10 mounted on it. The front nozzles 10 can be closed or opened as needed to meet the requirements of the number of blades in the next stage of the test blades 3 under real engine conditions. A rear valve 4 is set after the test blades 3, with several rear nozzles 11 mounted on it. Like the front nozzles 10, the rear nozzles 11 can also be closed or opened as needed to meet the requirements of the number of blades in the next stage of the test blades 3 under real engine conditions. The test wheel 7 is connected to the motor 9 via the adapter section 8. During the test, the motor 9 drives the test wheel 7 to rotate to provide a low-cycle centrifugal load.

[0032] The combined high- and low-cycle fatigue life of aero-engine blades is significantly reduced compared to the high- and low-cycle fatigue life alone. The device proposed in this invention can simultaneously apply high- and low-cycle fatigue loads to the test blade, thereby conducting combined high- and low-cycle fatigue tests on the same test blade at the same time, providing design guidance for the safe use of aero-engine blades. In addition, by changing the number of open and closed valves before and after the test blade, the influence of different numbers of blades before and after the test blade on the resonance excitation of the test blade can be simulated, providing guidance for the anti-resonance design of engine blades.

[0033] Example 3

[0034] The scheme of Example 1 is adopted, and:

[0035] The test blade 3 is set to have 24 blades in the upper stage and 32 blades in the lower stage. Then, the number of open front nozzles 10 on the front valve 2 is adjusted to 24, and the remaining nozzles are closed. The number of open rear nozzles 11 on the rear valve 4 is adjusted to 32, and the remaining nozzles are closed, in order to simulate the effect of the number of front and rear stage blades on the vibration of the test blade 3.

[0036] Gas flow is provided by fan 1 to provide high-cycle aerodynamic load. During the test, ventilation 1 and motor 9 are turned on, and high- and low-cycle combined fatigue loads are applied to the test blade 3 to obtain the true high- and low-cycle combined fatigue life of the engine blade.

[0037] In summary, this invention can consider both the centrifugal low-cycle loads on engine blades during aircraft takeoff and landing, and the high-cycle damage caused by aerodynamic loads to the blades. This allows for the implementation of combined high- and low-cycle fatigue tests on aero-engine blades on a testing facility, providing a basis for accurately assessing the fatigue life of aero-engine blades. Furthermore, by changing the number of open and closed nozzles on the front and rear valves, the influence of excitation sources from the preceding and following stages can be simulated, thereby determining the degree of harm caused by different excitation sources to blade resonance.

Claims

1. A high- and low-cycle combined fatigue testing device for aero-engine blades, comprising a fan (1) and a test blade (3) disposed between the upper edge (5) and the lower edge (6) of a wind tunnel, characterized in that: The test blade (3) is mounted on a test wheel (7) located outside the lower edge (6) of the wind tunnel, and the test wheel (7) is connected to the motor (9); a front valve (2) is provided between the fan (1) and the test blade (3), and multiple front nozzles (10) are evenly distributed on the front valve (2); a rear valve (4) is provided at the rear end of the test blade (3), and multiple rear nozzles (11) are evenly distributed on the rear valve (4). A fan (1) is used to provide aerodynamic force to simulate high-cycle fatigue load, and a motor (9) is used to drive the test wheel (7) and test blade (3) to rotate to provide low-cycle centrifugal load. This is used to evaluate the high- and low-cycle combined fatigue life of engine blades and to provide guidance for the safe use of engine blades. By changing the opening and closing of the front and rear nozzles of the test blade (3), the wake excitation of the front and rear stage blades is simulated, and the degree of harm of the front and rear stage blade excitation to the resonance of the test blade is evaluated. The front nozzle (10) can be closed or opened as needed to meet the requirements of the number of blades of the next stage of the test blade (3) under the actual engine condition; the rear nozzle (11) is the same as the front nozzle (10), and can be closed or opened as needed to meet the requirements of the number of blades of the next stage of the test blade (3) under the actual engine condition.

2. The aero-engine blade high- and low-cycle combined fatigue testing device as described in claim 1, characterized in that: The test wheel (7) is connected to the motor (9) via a transition section (8).

3. The aero-engine blade high- and low-cycle combined fatigue testing device as described in claim 1, characterized in that: The tenon groove of the test wheel (7) is consistent with the tenon groove of the wheel actually used.

4. The aero-engine blade high- and low-cycle combined fatigue testing device as described in claim 1, characterized in that: The strength of the test wheel (7) is consistent with the strength of the wheel used in actual applications.

5. The aero-engine blade high- and low-cycle combined fatigue testing device as described in claim 1, characterized in that: The front air nozzle (10) is distributed in a circle along the center of the wind tunnel.

6. The aero-engine blade high- and low-cycle combined fatigue testing device as described in claim 1, characterized in that: The rear air nozzle (11) is distributed in a circle along the center of the wind tunnel.

7. The aero-engine blade high- and low-cycle combined fatigue testing device as described in claim 1, characterized in that: The fan (1) is distributed in a circle around the center of the wind tunnel.

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