Method for designing low cycle fatigue test load spectrum of combustion chamber casing

Abstract

The combustion chamber case low cycle fatigue test load spectrum design method of the present application belongs to the field of aero-engines, including combustion chamber case low cycle fatigue life design requirement analysis, and determining the corresponding working load of each life design cycle of the combustion chamber case; developing low cycle fatigue damage analysis under each life design cycle of the combustion chamber case, and performing equivalent conversion on the life design cycles by types to obtain equivalent cycles of each type and the number of times; determining the test load block spectrum and the number thereof according to the equivalent cycles of each type after conversion; and finally determining the test load spectrum capable of representing all required life design cycles. The obtained combustion chamber case low cycle fatigue test load spectrum is closer to the actual use of the engine, can comprehensively and completely achieve the test examination requirements of the case under different types of cyclic loads, the test examination is more reasonable, meets the fine design requirements, and has good engineering application significance.

Description

Technical Field

[0001] This invention belongs to the technical field of aero-engines, and particularly relates to a method for designing the load spectrum of a combustion chamber casing for low-cycle fatigue testing. Background Technology

[0002] The combustion chamber casing is a crucial load-bearing component in an aero-engine, operating under harsh environments such as high temperature and high pressure. Statistics show that the main failures of the combustion chamber casing include cracks, deformation, and instability, with fatigue-induced cracks in the outer casing being the most serious and accounting for the largest proportion. If a crack in the combustion chamber casing extends to significant leakage or even casing explosion, the consequences are extremely severe, having resulted in first-class accidents involving engine destruction and loss of life. Therefore, it is required that the combustion chamber casing undergo low-cycle fatigue testing (GJB-241, GJB-242) before design finalization.

[0003] In aero-engine type certification tests, engineering practice typically uses a "0-maximum state point-0" cycle as the equivalent cycle for the test. Then, using the damage equivalence principle, all heavy, medium, and light-duty life design cycles are converted into equivalent cycles. Finally, based on the linear damage superposition principle, the number of equivalent cycles is determined, and a low-cycle fatigue test load spectrum is established. Figure 1 As shown.

[0004] This test load spectrum design method can assess the total cyclic damage of the engine combustion chamber casing during operation and meet the requirements for low-cycle fatigue life assessment of the casing, but it also has the following shortcomings:

[0005] Using a single equivalent cyclic test load spectrum can only assess the damage / failure modes of the same type of cyclic load, and cannot fully assess the damage / failure modes caused by other types of cyclic loads during engine operation. Summary of the Invention

[0006] In view of this, the combustion chamber casing low-cycle fatigue test load spectrum design method provided by the present invention solves the problem of the existing technology's coarse test load spectrum design, which cannot fully assess the damage / failure modes caused by other types of cyclic loads during engine operation, resulting in low test accuracy.

[0007] A method for designing the load spectrum of a combustion chamber casing for low-cycle fatigue testing is provided, the method comprising:

[0008] S101: Analyze the life design requirements of the combustion chamber casing, and clarify the life design cycles and their number of cycles specified in the life design requirements;

[0009] S102: Determine the casing working load for the combustion chamber casing life design cycle according to the aforementioned life design requirements;

[0010] S103: Based on the casing working load corresponding to all life design cycles, conduct combustion chamber casing damage analysis, analyze the damage value of each life design cycle, and combine the number of life design cycles, according to the damage equivalence principle, convert the equivalent of all life design cycles of the same type into a certain equivalent cycle, and determine the number of equivalent cycles.

[0011] S104: Based on the determined types of equivalent cycles and their number, determine the test load block spectrum containing the types of equivalent cycles and its number;

[0012] S105: Linearly organize the number of cycles for each type of equivalent loop, and then store or output the data.

[0013] The beneficial effects of this invention are:

[0014] The method of this invention includes analyzing the low-cycle fatigue life design requirements of the combustion chamber casing, clarifying the corresponding working loads for each life design cycle of the combustion chamber casing; conducting low-cycle fatigue damage analysis of the combustion chamber casing under each life design cycle, and performing equivalent conversion of the life design cycles by type to obtain the equivalent cycles and their number for each type; determining the test load spectrum and its number based on the converted equivalent cycles; and finally determining the test load spectrum that can represent all required life design cycles. The obtained low-cycle fatigue test load spectrum of the combustion chamber casing is closer to the actual use of the engine, and can comprehensively and completely simulate the working conditions of the casing under different types of cyclic loads. The test evaluation is more reasonable, meets the requirements of refined design, and has engineering application significance. Furthermore, this method can simultaneously evaluate the damage / failure modes caused by various types of cyclic loads during the operation of the combustion chamber casing. The evaluation method is more comprehensive and reliable than current engineering application methods, and is applicable to the fatigue test load spectrum design of combustion chamber casings for different types of aero-engines, possessing good engineering applicability. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A schematic diagram of the load spectrum for low-cycle fatigue testing of the combustion chamber casing in the prior art;

[0017] Figure 2 Flowchart of this invention;

[0018] Figure 3 A schematic diagram of the test load spectrum of this invention. Detailed Implementation

[0019] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0020] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this invention, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using other structures and / or functionalities besides one or more of the aspects set forth herein.

[0022] like Figure 2 As shown, the method for designing the load spectrum of the combustion chamber casing for low-cycle fatigue testing includes:

[0023] S101: Analyze the life design requirements of the combustion chamber casing, clarifying each life design cycle and its number of cycles specified in the life design requirements. For details, please refer to Table 1.

[0024]

[0025] Table 1

[0026] The life design requirements include three categories of cycles: heavy, medium, and light. Each of the three categories includes multiple cyclic loads.

[0027] S102: Determine the casing working load for the combustion chamber casing life design cycle according to the life design requirements. Specifically, the casing working load includes at least pressure, temperature field, axial force on the mounting edge, and torque on the mounting edge.

[0028] S103: Based on the casing working load corresponding to all life design cycles, conduct combustion chamber casing damage analysis, analyze the damage value of each life design cycle, and combine the life design cycle count with the damage equivalence principle to convert the equivalent of all life design cycles of the same type into a certain equivalent cycle, and determine the number of that equivalent cycle. Specifically: According to the damage equivalence principle, convert the life design cycles and cycle counts of the same type in all life design cycles into equivalent cycles. The conversion steps include:

[0029] a) Analyze and calculate the life design cycle damage value of the combustion chamber casing under all cyclic loads in heavy, medium, and light cycle types;

[0030] b) Determine the peak point state of the equivalent cyclic load to be converted, and determine the peak point of the load with the maximum load point or the minimum number of cycles as the peak point of the equivalent cyclic load, and determine the parking, slow, and cruise states as the valley points of the heavy, medium, and light cyclic equivalent cyclic loads.

[0031] c) Calculate the equivalent cycle damage value of the combustion chamber casing under heavy, medium, and light equivalent cycle loads based on the equivalent cycle peak and valley points;

[0032] d) Based on the life design cycle damage value and the equivalent cycle damage value, calculate the damage equivalence conversion coefficients for different types of damage using the damage equivalence method;

[0033] e) Based on the life design cycle number of the combustion chamber casing and the damage equivalent conversion factor, the test cycle number of the equivalent cyclic load is calculated by superposition.

[0034] Furthermore, the number of cycles for various equivalent quantities, including the number of cycles for heavy equivalent quantities N, is also considered. I Medium equivalent cycle number N II and light equivalent cycle number N III Determine the number of heavy equivalent cycles N. I The basis is the equivalence of heavy-cycle total damage and heavy-cycle equivalent total damage based on engine life design requirements;

[0035] Medium equivalent cycle number N II and light equivalent cycle number N III Determination principles and the number of heavy equivalent cycles N I The principle is the same, based on the fact that the total cyclic damage corresponding to the engine life design requirements is equivalent to the corresponding equivalent total cyclic damage.

[0036] S104: Based on the determined types of equivalent cycles and their number, determine the test load block spectrum containing each type of equivalent cycle and its number, specifically:

[0037] Determine the number of heavy cycles n IMedium-sized loop number n II and the number of light cycles n III And satisfy:

[0038] Number of heavy-duty equivalent cycle "stop - equivalent cycle load peak point - stop": n I =N I / N I =1;

[0039] Number of medium-sized equivalent cycle "slow start - equivalent cycle load peak point - slow start": n II =N II / N I ;

[0040] Number of light-duty equivalent cycle "cruise-equivalent cycle load peak point-cruise" cycles: n III =N III / N I .

[0041] Furthermore, the number of equivalent load cycles must be an integer. If the number is not divisible and remains a decimal, it must be rounded up to ensure that the test meets the combustion chamber casing life assessment requirements.

[0042] S105: Linearly organize the number of iterations for various equivalent loops, and then store or output the data. Specifically:

[0043] As shown in Table 2, the number of loops for each type of loop is linearly adjusted, and then the data is stored or output.

[0044]

[0045] Table 2

[0046] Table 2 lists the number of cycles of each type included in the test load spectrum and the number of times the test load spectrum should be carried out. A schematic diagram of the test load spectrum is provided, and the data is stored or output. This method categorizes the life cycles in the engine mission profile into heavy, medium, and light cycles according to load type and load magnitude, thereby assessing the damage impact of different types of cyclic loads on different dangerous locations of the combustion chamber casing. The test assessment is close to actual use, more reasonable, meets the requirements of refined design, and has engineering application significance.

[0047] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for designing the load spectrum for low-cycle fatigue testing of a combustion chamber casing, characterized in that, The method includes: S101: Analyze the life design requirements of the combustion chamber casing, clarify the life design cycles and their number of cycles specified in the life design requirements. The life design requirements include three types of cycles: heavy, medium and light. Each of the three types of cycles includes multiple cyclic loads. S102: Determine the casing working load for the combustion chamber casing life design cycle according to the aforementioned life design requirements; S103: Based on the casing working load corresponding to all life design cycles, conduct a combustion chamber casing damage analysis, analyze the damage value for each life design cycle, and, in conjunction with the number of life design cycles, convert the equivalent of all life design cycles of the same type into a certain equivalent cycle according to the damage equivalence principle, and determine the number of that equivalent cycle. Based on the damage equivalence principle, the lifetime design cycles and cycle counts of the same type in all lifetime design cycles are equivalently converted. The conversion steps include: a) Analyze and calculate the life design cycle damage value of the combustion chamber casing under all cyclic loads in heavy, medium, and light cycle types; b) Determine the peak point state of the equivalent cyclic load to be converted, and determine the peak point of the load with the maximum load point or the minimum number of cycles as the peak point of the equivalent cyclic load, and determine the parking, slow, and cruise states as the valley points of the heavy, medium, and light cyclic equivalent cyclic loads. c) Calculate the equivalent cycle damage value of the combustion chamber casing under heavy, medium, and light equivalent cycle loads based on the equivalent cycle peak and valley points; d) Based on the life design cycle damage value and the equivalent cycle damage value, calculate the damage equivalence conversion coefficients for different types of damage using the damage equivalence method; e) Based on the life design cycle number of the combustion chamber casing and the damage equivalent conversion factor, the test cycle number of the equivalent cyclic load is calculated by superposition. Cycle counts for various equivalents, including heavy equivalent cycles Medium equivalent cycle number and light equivalent cycle number Determine the number of heavy equivalent cycles. The basis is the equivalence of heavy-cycle total damage and heavy-cycle equivalent total damage based on engine life design requirements; Medium equivalent cycle number and light equivalent cycle number Determination principles and number of cycles for heavy equivalent The principles are the same; S104: Based on the determined equivalent cycles and their number, determine the test load block spectrum containing each type of equivalent cycle and its number, including determining the number of heavy cycles in a single load block spectrum. Medium-sized cycle number and light cycle number And satisfy: ； S105: Linearly organize the number of cycles for each type of equivalent loop, and then store or output the data.

2. The design method according to claim 1, characterized in that, S102 includes: The casing working load for the determined combustion chamber casing life design cycle includes at least pressure, temperature field, mounting side axial force, and mounting side torque.

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