A large and medium-sized aircraft engine nacelle structure environmental simulation test method

Abstract

The application belongs to the technical field of environmental aging test, and is a large and medium-sized aircraft engine nacelle structure environmental simulation test method. The overall structure of a specific test procedure and multiple action modes of accelerated aging test are determined. Then, the material characteristics of the aircraft are analyzed to determine the specific design requirements of the accelerated aging test. Finally, the use and maintenance requirements of the aircraft, the load cycle conditions, and the environmental parameters and action time are analyzed to perform the accelerated aging test. On the one hand, the aging resistance performance of the material of the special temperature-medium environmental structure of the large aircraft engine nacelle can be accurately evaluated. On the other hand, the period of the accelerated aging test in the test process is short. Through the indoor artificial accelerated aging test, the time for evaluating the aging resistance of the large aircraft in a specific environment is shortened to 3% of the natural environment. On the other hand, the requirement for the equipment for implementing the test is low, and the existing medium-resistant and heating test equipment can be used for the accelerated aging test.

Description

Technical Field

[0001] This application belongs to the field of environmental aging testing technology, and specifically relates to an environmental simulation test method for the nacelle structure of large and medium-sized aircraft engines. Background Technology

[0002] The heat-affected zone surrounding the power system, such as the engine nacelle of a large aircraft, is classified as an internal semi-enclosed environment in aircraft structural classification. However, the actual environment differs significantly from other internal semi-enclosed environments. Local areas within the nacelle are constantly immersed in liquid media such as rainwater leaking from the top, lubricating oil, and fuel leaking from pipes and joints. Under such immersion, tiny liquid pools easily form inside non-metallic materials such as coatings. When the power system is running, the temperature can rise from room temperature to around 120°C in a short period of time. After being heated, the internal vapor pressure of the liquid pools increases rapidly, compressing the surrounding materials and causing damage to non-metallic materials. This damage mechanism is significantly different from that in other internal semi-enclosed environments, making it impossible to assess the environmental resistance of materials using accelerated spectrum analysis in internal semi-enclosed environments.

[0003] For the special temperature-medium environment regions such as engine nacelles and the surrounding areas of power systems, the actual natural environment testing cycle is too long, and there are no mature accelerated testing methods, making it difficult to meet the requirements of the model development schedule. Therefore, based on long-term observation and analysis of the application environment of large aircraft engine nacelles and other parts, it is necessary to design an accelerated aging test procedure suitable for special temperature-medium environment regions such as medium-sized aircraft engine nacelles, in order to quickly evaluate the durability of materials in such regions. Summary of the Invention

[0004] The purpose of this application is to provide an environmental simulation test method for engine nacelle structures of large and medium-sized aircraft, so as to solve the problem in the prior art that it is difficult to evaluate the environmental resistance performance of engine nacelle materials in special temperature-medium environment regions.

[0005] The technical solution of this application is: a method for environmental simulation testing of the nacelle structure of large and medium-sized aircraft engines, including:

[0006] Based on the overall structural characteristics of the corresponding engine nacelle, determine the overall structure of the specific test procedure and multiple operating modes of the accelerated aging test, and prepare the required test pieces;

[0007] By analyzing the material characteristics of the aircraft, the specific design requirements for accelerated aging tests were determined, including the composition of the liquid medium, the temperature change range and speed, vibration parameter requirements, and the duration of each action mode.

[0008] By analyzing the aircraft's usage and maintenance requirements, load cycle conditions, and various environmental parameters and exposure times, accelerated aging tests were conducted. Specifically, the test pieces underwent corresponding liquid immersion tests, rapid heating tests, and room temperature vibration tests to obtain the effect of short-term indoor aging of the test pieces in simulating long-term natural environmental aging.

[0009] Preferably, the method for determining the multiple operating modes of the engine nacelle is as follows:

[0010] By analyzing the medium and temperature action process and material damage mechanism in specific parts of the engine nacelle, the composition of the action mode and the test sequence are determined. Specifically, the test should first be a liquid immersion test, followed by rapid heating test immediately after immersion without drying, and finally a vibration test.

[0011] Preferably, the method for determining the specific design requirements of the accelerated aging test is as follows:

[0012] Based on the selection of aircraft oils and lubricants, and combined with the liquid leakage found during power system maintenance, one or more liquids are selected as test media.

[0013] Based on the calculated or measured results of the temperature field of the nacelle or APU compartment of a large aircraft engine, determine the maximum temperature of temperature change and the rate of temperature rise.

[0014] The vibration parameters are determined based on the calculated or measured results of the aircraft vibration spectrum.

[0015] The duration of each action mode is determined based on the frequency and duration of immersion in liquid media within the engine nacelle or APU compartment of a large aircraft, as well as the temperature changes and duration during typical flight processes.

[0016] Preferably, when conducting liquid immersion tests, if multiple liquids are present in a specific part of the engine nacelle, the tests should be conducted in the order of distilled water, fuel oil, hydraulic oil, and lubricating oil. The water immersion test should be heated, while the oil immersion test should be conducted at room temperature.

[0017] Preferably, in the selection of aircraft oils and lubricants, if a specific part of the engine nacelle is soaked in a mixed oil, then the mixed oil is used for an oil immersion test.

[0018] Preferably, at the highest temperature and heating rate of the temperature change, the highest test temperature is calculated based on the measured highest temperature or theoretically calculated highest temperature of the specific environment of the large aircraft, and the highest test temperature is the measured or calculated highest temperature plus 30°C; the heating time is taken as the time from engine start-up to stable operation, and the heating rate is calculated through the highest temperature and heating time.

[0019] Preferably, the specific design method of the accelerated aging test is as follows:

[0020] A liquid immersion test is conducted by introducing a liquid medium into the interior of the test material, creating a tiny liquid pool.

[0021] Test temperatures: water immersion temperature Tw = (49±2)℃, oil immersion temperature To = (23±2)℃

[0022] Test humidity: RH = 50%–70%

[0023] Experimental duration: t = (1 + type of oil used for immersion × 1) days;

[0024] Conduct rapid temperature rise test:

[0025] Test temperature: T = (measured or calculated highest temperature T1 ± 30)℃;

[0026] Heating rate: S = T / heating time

[0027] The rapid heating test process is as follows: After the test piece is removed from the immersion liquid, the surface liquid is dried with filter paper, and then it is immediately placed in a room temperature oven and heated to the test temperature T at a heating rate S, and kept at the temperature for 2 hours.

[0028] If the vibration spectrum of the part cannot be obtained, conduct a vibration test at room temperature. If the vibration frequency is f = 50 Hz and the amplitude is A = 4 mm, then conduct the test at room temperature.

[0029] Preferably, it further includes:

[0030] The number of accelerated aging test cycles is determined according to the design requirements of large aircraft. The test pieces are subjected to cyclic action in liquid immersion mode, rapid heating mode and vibration mode. Each cycle is equivalent to 3 months of natural environmental aging.

[0031] This application discloses a method for environmental simulation testing of large and medium-sized aircraft engine nacelles. It determines the overall structure of a specific test procedure and multiple operating modes for accelerated aging testing. Then, it analyzes the material characteristics of the aircraft to determine the specific design requirements for accelerated aging testing. Finally, it analyzes the aircraft's usage and maintenance requirements, load cycle conditions, and various environmental parameters and operating times before conducting accelerated aging tests. On the one hand, it can accurately evaluate the aging resistance of structural components such as large aircraft engine nacelles in special temperature-medium environments. On the other hand, the accelerated aging test cycle is short; through indoor artificial accelerated aging testing, the time for evaluating the aging resistance of large aircraft under specific environments is reduced to 3% of that in natural environments. Furthermore, it has low requirements for the equipment used in conducting the tests; existing medium resistance and heating testing equipment can be used for accelerated aging testing. Attached Figure Description

[0032] To more clearly illustrate the technical solutions provided in this application, the accompanying drawings will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application.

[0033] Figure 1 This is a schematic diagram of the overall process of this application;

[0034] Figure 2 This application provides a schematic diagram illustrating the specific process of accelerated aging tests in special areas such as the nacelles of large aircraft engines. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings.

[0036] An environmental simulation test method for the nacelle structure of large and medium-sized aircraft engines.

[0037] like Figure 1 As shown, the specific steps include the following:

[0038] Step S100: Determine the overall structure of the specific test procedure and multiple action modes of the accelerated aging test based on the overall structural characteristics of the corresponding engine nacelle, and prepare the required test specimens; the action modes include: liquid medium immersion action mode, high and low temperature cycle action mode and vibration action mode;

[0039] Preferably, based on the operational characteristics of a large aircraft, the engine nacelle in this specific area has a semi-enclosed internal structure. During rainfall, rainwater flows in through the top gaps. When the aircraft is parked and under maintenance, lubricating oil and fuel seep out from pipe joints and other parts, flowing along the inner wall of the nacelle cover and accumulating at the bottom of the nacelle. Water and mixed fuels soak the non-metallic materials such as coatings, rubber, and sealants inside the nacelle for a long time. Therefore, solution soaking is the first mode of action. When the engine starts, the ambient temperature inside the nacelle rises rapidly from room temperature to 110°C. The liquid seeping into the non-metallic materials expands due to heat, accelerating material aging. Therefore, rapid heating is the second mode of action. When the engine is running, it causes periodic vibrations in the nacelle and other parts, promoting the expansion of the aging and damage areas of the materials inside the nacelle. Therefore, vibration is the third mode of action.

[0040] Thus, the method for determining the multiple operating modes of the engine nacelle is as follows:

[0041] By analyzing the medium and temperature action process and material damage mechanism in specific parts of the engine nacelle, the composition of the action mode and the test sequence are determined. Specifically, the test should first be a liquid immersion test, followed by rapid heating test immediately after immersion without drying, and finally a vibration test.

[0042] Step S200: By analyzing the material characteristics of the aircraft, determine the specific design requirements for the accelerated aging test, including the composition of the liquid medium, the temperature change range and speed, vibration parameter requirements, and the action time of each action mode.

[0043] Preferably, the method for determining the specific design requirements of accelerated aging tests is as follows:

[0044] Step S210: Based on the selection of aircraft oil and lubricating materials, and combined with the liquid leakage found during power system maintenance, select one or more liquids as test media.

[0045] Preferably, in the selection of aircraft oils and lubricants, if a specific part of the engine nacelle is soaked in a mixed oil, then the mixed oil is used for an oil immersion test.

[0046] Step S220: Determine the highest temperature and heating rate of temperature change based on the calculated or measured results of the temperature field of the large aircraft engine nacelle or APU compartment.

[0047] Preferably, at the highest temperature and heating rate of the temperature change, the highest test temperature is calculated based on the measured highest temperature or theoretically calculated highest temperature of the specific environment of the large aircraft. The highest test temperature is the measured or calculated highest temperature plus 30°C to accelerate the aging process. The heating time is taken as the time from engine start-up to stable operation, and the heating rate is calculated using the highest temperature and heating time.

[0048] Step S230: Determine the vibration parameters based on the calculated or measured results of the aircraft vibration spectrum;

[0049] Step S240: Determine the duration of each action mode based on the frequency and duration of immersion in the liquid medium in the engine nacelle or APU compartment of a large aircraft, as well as the temperature changes and duration during typical flight processes.

[0050] Preferably, when conducting liquid immersion tests, if multiple liquids are present in a specific part of the engine nacelle, the tests should be conducted in the order of distilled water, fuel oil, hydraulic oil, and lubricating oil. The water immersion test should be heated, while the oil immersion test should be conducted at room temperature. This can effectively shorten the test time and avoid safety risks.

[0051] As a specific implementation method, sampling and analysis of the liquid composition in the engine nacelle revealed that the non-metallic materials that are long-term immersed in the bottom of the engine include HP-8B lubricating oil and RP-3 fuel. The ratio of the two is not constant, but is close to 1:1 on average. The solubility of the mixture of HP-8B lubricating oil and RP-3 fuel is higher than that of a single liquid. It is more reasonable to use a 1:1 volume ratio of HP-8B / RP-3 mixture for immersion. To avoid safety risks caused by heating, immersion should be carried out at room temperature, with each immersion cycle lasting 1 day.

[0052] During rainy days, rainwater enters the nacelle through the gaps along the hatch cover. The soaking time is mainly affected by the frequency of rainfall. A certain large aircraft operates at a southern airport with about 200 days of rainfall per year, resulting in a long soaking time. Since water and fuel are incompatible, water and fuel should be soaked separately. To accelerate the test process, soaking is carried out at 49°C, with each soaking cycle lasting 1 day.

[0053] Step S300 involves analyzing the aircraft's usage and maintenance requirements, load cycle conditions, and various environmental parameters and durations, and conducting accelerated aging tests. Specifically, this involves conducting corresponding liquid immersion tests, rapid heating tests, and room temperature vibration tests on the test pieces to obtain the effect of short-term indoor aging of the test pieces in a simulated long-term natural environment.

[0054] Preferably, the specific design method for accelerated aging tests is as follows:

[0055] Step S310: Conduct a liquid immersion test. The liquid immersion test is used to test the swelling and aging process of internal structures such as aircraft engine nacelles after immersion in liquids such as water and oil. This allows the liquid medium to enter the interior of the test material, generating tiny liquid pools.

[0056] Test temperatures: water immersion temperature Tw = (49±2)℃, oil immersion temperature To = (23±2)℃

[0057] Test humidity: RH = 50%–70%

[0058] Experimental duration: t = (1 + type of oil used for immersion × 1) days;

[0059] By conducting liquid immersion tests, rapid heating tests, and room temperature vibration tests on the test specimens with a defined duration, the effect of short-term indoor aging simulating long-term natural environmental aging of the test specimens can be accurately obtained.

[0060] Step S320: Conduct a rapid heating test. Rapid heating is used to simulate the effect of heat released during the operation of a large aircraft power system, causing the surrounding environment to heat up rapidly, which in turn causes the liquid inside the test material to vaporize and lead to aging damage to the material.

[0061] Test temperature: T = (measured or calculated highest temperature T1 ± 30)℃;

[0062] Heating rate: S = T / heating time

[0063] The rapid heating test process is as follows: After the test piece is removed from the immersion liquid, the surface liquid is dried with filter paper, and then it is immediately placed in a room temperature oven and heated to the test temperature T at a heating rate S, and kept at the temperature for 2 hours.

[0064] Step S330: Conduct a room temperature vibration test. If the vibration spectrum of the part cannot be obtained, conduct the test at a vibration frequency of f = 50 Hz and an amplitude of A = 4 mm.

[0065] As a specific implementation method, the material being tested is a coating, which is relatively thin and less affected by vibration factors. Therefore, it is vibrated at a frequency of f = 50 Hz and an amplitude of A = 4 mm according to the requirements of the aviation fire protection vibration test, for a duration of 1 hour.

[0066] After determining the action time for each action mode, accelerated aging tests can be conducted on the corresponding action modes using the determined action time, which is to perform the test in step 3 of the embodiments of the present invention. During the aging and damage process of the coating material inside the nacelle, the huge vapor pressure generated by the heating of the liquid inside the coating is the main factor. Therefore, after the solution immersion mode, the heating mode should be carried out immediately, and the test piece should not be allowed to dry.

[0067] After 20 cycles of testing, the accelerated aging test specimens were compared with the engine nacelle coating damaged by natural environmental aging. The condition of the specimens was comparable to the most severely damaged area after 5 years of installation. Therefore, it can be determined that each test cycle is equivalent to 3 months of natural aging.

[0068] Step S400: Determine the number of cycles for accelerated aging test according to the design requirements of large aircraft. Perform cyclic treatments on the test piece in liquid immersion mode, rapid heating mode and vibration mode. Each cycle is equivalent to 3 months of natural environmental aging.

[0069] Based on the test process of steps S200-S400, a large aircraft engine nacelle structure environmental simulation test procedure is formed.

[0070] It has the following characteristics:

[0071] a) Relevance. Based on the structural characteristics of large aircraft engine nacelles, this study includes the main factors and effects of aging in the actual service environment, reproducing the forms, characteristics, and composition of aging damage and aging products that occur during actual service.

[0072] b) Acceleration. It can greatly shorten the aging process time in actual environment, reduce the accelerated aging test cycle to an acceptable range, and accelerate the test time by about 30 times compared with the natural environment aging time.

[0073] c) Feasibility. The accelerated aging test procedure can be implemented in the laboratory without modifying existing general-purpose test equipment.

[0074] d) It is possible to establish the equivalent acceleration relationship between the accelerated testing procedure and the ground parking environment through reasonable criteria and methods.

[0075] This application provides a novel accelerated aging test method for large aircraft under specific environmental conditions. It is the first artificial accelerated aging test method to simulate the special temperature-medium aging environment of large aircraft engine nacelles, applicable to the aviation field. This method objectively reflects the monthly changes in environmental factors affecting aging by analyzing the structural characteristics, materials, connection methods, usage, and maintenance requirements of large aircraft. This results in a "large aircraft engine nacelle structural environmental simulation test procedure" characterized by the duration, frequency, and intensity of each environmental factor's action. On one hand, it can accurately evaluate the aging resistance of structural components such as large aircraft engine nacelles under special temperature-medium environments. On the other hand, the accelerated aging test cycle is short; through indoor artificial accelerated aging testing, the time for evaluating the aging resistance of large aircraft under specific environmental conditions is reduced to 3% of that in natural environments. Furthermore, the equipment requirements for conducting the test are low; existing medium resistance and heating test equipment can be used for accelerated aging testing.

[0076] The following is a specific example illustrating the accelerated aging test method for special temperature-medium areas such as engine nacelles: solution immersion + rapid heating + room temperature vibration. Figure 2 The diagram shown is a schematic of the accelerated aging test method for special areas such as the nacelle of a large aircraft engine provided in the embodiment of the present invention. The accelerated aging test process will be described in detail below.

[0077] a) Step 1, Solution Immersion Test: The solution immersion test is used to simulate the swelling and aging process of internal materials of aircraft structures when immersed in a medium.

[0078] The test condition control parameters include:

[0079] Test temperatures: Tw (water immersion) = 49℃, To (oil immersion) = 23℃;

[0080] Test humidity: RH = 50-70%;

[0081] Test duration: t = 1 day (water immersion) + 1 day (immersion in 50% RP-3 fuel oil + 50% HP-8B lubricating oil).

[0082] b) Step 2, rapid temperature rise test. The rapid temperature rise test is used to simulate the effect of rapid rise in ambient temperature on the coating material after immersion in liquid in the nacelle of a large aircraft engine.

[0083] The test condition control parameters include:

[0084] Initial temperature of the experiment: 23±2℃;

[0085] Maximum test temperature: 140±5℃;

[0086] Heating rate:

[0087] Insulation time: 2 hours.

[0088] c) Step 3: Room temperature vibration test. The room temperature vibration test is used to simulate the vibration of a specific structure.

[0089] Frequency = 5Hz;

[0090] Amplitude = 4mm;

[0091] Duration of action = 1 hour.

[0092] d) Determine the number of accelerated aging test cycles according to the design requirements of large aircraft, and conduct cyclic tests of liquid immersion test, rapid heating test and room temperature vibration test on the test piece. Each cycle is equivalent to 3 months of natural environmental aging. After the expiration, check the appearance of the test piece according to GB / T1766 or the test task book.

[0093] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for environmental simulation testing of the nacelle structure of large and medium-sized aircraft engines, characterized in that, include: Based on the overall structural characteristics of the corresponding engine nacelle, determine the overall structure of the specific test procedure and multiple operating modes of the accelerated aging test, and prepare the required test pieces; By analyzing the material characteristics of the aircraft, the specific design requirements for accelerated aging tests were determined, including the composition of the liquid medium, the temperature change range and speed, vibration parameter requirements, and the duration of each action mode. By analyzing the aircraft's usage and maintenance requirements, load cycle conditions, and various environmental parameters and exposure times, accelerated aging tests were conducted. Specifically, the test pieces underwent corresponding liquid immersion tests, rapid heating tests, and room temperature vibration tests to obtain the effect of the test pieces aging in a short-term indoor environment that simulates a long-term natural environment. The specific design method for the accelerated aging test is as follows: A liquid immersion test is conducted by introducing a liquid medium into the interior of the test material, creating a tiny liquid pool. Test temperatures: Water immersion temperature Tw = (49±2)℃, Oil immersion temperature To = (23±2)℃ Test humidity: RH = 50%~70% Experimental time: t = (1 + type of oil used for immersion × 1) days; Conduct rapid temperature rise test: Test temperature: T = (measured or calculated highest temperature T1 ± 30)℃; Heating rate: S = T / heating time The rapid heating test process is as follows: After the test piece is removed from the immersion liquid, the surface liquid is dried with filter paper, and then it is immediately placed in a room temperature oven and heated to the test temperature T at a heating rate S, and kept at the temperature for 2 hours. If the vibration spectrum of the part cannot be obtained, conduct a vibration test at room temperature. If the vibration frequency is f=50Hz and the amplitude is A=4mm, then conduct the test.

2. The environmental simulation test method for the nacelle structure of large and medium-sized aircraft engines as described in claim 1, characterized in that, The method for determining the multiple operating modes of the engine nacelle is as follows: By analyzing the medium and temperature action process and material damage mechanism in specific parts of the engine nacelle, the composition of the action mode and the test sequence are determined. Specifically, the test should first be a liquid immersion test, followed by rapid heating test immediately after immersion without drying, and finally a vibration test.

3. The environmental simulation test method for the nacelle structure of large and medium-sized aircraft engines as described in claim 1, characterized in that, The specific design requirements for the accelerated aging test are determined as follows: Based on the selection of aircraft oils and lubricants, and combined with the liquid leakage found during power system maintenance, one or more liquids are selected as test media. Based on the calculated or measured results of the temperature field of the nacelle or APU compartment of a large aircraft engine, determine the maximum temperature of temperature change and the rate of temperature rise. The vibration parameters are determined based on the calculated or measured results of the aircraft vibration spectrum. The duration of each action mode is determined based on the frequency and duration of immersion in liquid media within the engine nacelle or APU compartment of a large aircraft, as well as the temperature changes and duration during typical flight processes.

4. The environmental simulation test method for the nacelle structure of large and medium-sized aircraft engines as described in claim 3, characterized in that: When conducting liquid immersion tests, if multiple liquids are present in a specific part of the engine nacelle, the tests should be conducted in the following order: distilled water, fuel oil, hydraulic oil, and lubricating oil. The water immersion test should be heated, while the oil immersion test should be conducted at room temperature.

5. The environmental simulation test method for the nacelle structure of large and medium-sized aircraft engines as described in claim 3, characterized in that: When selecting aircraft oils and lubricants, if a specific part of the engine nacelle is soaked in a mixed oil, an oil immersion test is conducted using the mixed oil.

6. The environmental simulation test method for the nacelle structure of large and medium-sized aircraft engines as described in claim 3, characterized in that: At the highest temperature and heating rate of the temperature change, the highest test temperature is calculated based on the measured highest temperature or theoretically calculated highest temperature in the specific environment of the large aircraft. The highest test temperature is the measured or calculated highest temperature plus 30°C. The heating time is taken as the time from engine start-up to stable operation, and the heating rate is calculated using the highest temperature and heating time.

7. The environmental simulation test method for the nacelle structure of large and medium-sized aircraft engines as described in any one of claims 1-6, characterized in that, Also includes: The number of accelerated aging test cycles is determined according to the design requirements of large aircraft. The test pieces are subjected to cyclic action in liquid immersion mode, rapid heating mode and vibration mode. Each cycle is equivalent to 3 months of natural environmental aging.

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