Design method for characteristic simulation part of flame tube of periodically arranged porous thin-wall combustion chamber

Abstract

The invention discloses a design method of a periodically-arranged porous thin-wall combustion chamber flame tube characteristic simulation piece, which comprises the following steps: carrying out fluid-thermal-solid coupling analysis in a real structure service environment, obtaining the temperature field distribution of a combustion chamber flame tube and the size and direction of a first principal stress, and determining a part with the maximum first principal stress as a dangerous part; inserting an initial crack into a dangerous part of a real component, carrying out crack propagation numerical simulation, and extracting a stress intensity factor change rule on a crack propagation path; on the basis of keeping key geometric characteristics of a periodically arranged porous structure, a simulation piece is configured and designed into a biaxial flat plate stretching piece, and stress gradient distribution of a real component is matched through porous array parameter optimization; a biaxial tensile testing machine is adopted to apply a multi-axial load to the simulation part, and it is ensured that the stress intensity factor amplitude under different crack lengths is kept consistent with that of a real component. The method has important engineering value for damage tolerance evaluation and life prediction of the aero-engine combustion chamber.

Description

Technical Field

[0001] The present invention belongs to the field of aerospace engines, and in particular relates to a design method for a characteristic simulation part of a periodically arranged porous thin-walled combustion chamber flame tube. Background Art

[0002] The combustion liner is a critical component of an aircraft engine. During operation, it must withstand complex loads and extreme operating conditions, significantly different from those experienced by conventional stators or rotors. In addition to bearing conventional gas pressure, the liner is also subject to significant axial loads. Therefore, biaxial tensile testing is crucial in the design of components simulating the structural characteristics of the combustion liner.

[0003] As a key component of an aircraft engine, the combustion chamber flame tube faces huge challenges in design and life assessment due to its structural complexity and diverse load environments. Compared with the aircraft engine wheel structure, the flame tube and other typical hot end stators are also prone to fracture and damage. Therefore, it is crucial to accurately assess its crack propagation life to ensure the reliability and service life of the structure. In this context, the biaxial tensile test provides an effective experimental means. By applying different loads in two perpendicular directions, it can simulate the multi-dimensional stress field distribution and deformation characteristics of the flame tube under actual working conditions, ensuring that the first principal stress distribution of the simulated component is consistent with the real structure.

[0004] Furthermore, due to the influence of the periodically arranged porous structure, the crack propagation path is not necessarily along the direction of the maximum principal stress gradient. Therefore, the design of this test piece considers the influence of the periodically arranged porous structure on the flame tube. After ensuring that the first principal stress distribution of the simulated part is consistent with the real structure, the periodic arrangement of the test section holes of the simulated part is adjusted to control the crack propagation path of the simulated part and the stress intensity factor at different crack lengths to be consistent with the real part.

[0005] This test piece provides a more realistic representation of the mechanical behavior of the flame tube under complex loading conditions, revealing crack growth patterns under varying stress ratios and load paths. This data and information plays a crucial role in optimizing the structural design of the flame tube and improving its durability and safety. Therefore, this test piece not only enhances the scientific nature and accuracy of the design but also provides reliable experimental support for damage tolerance design, making it a crucial technical tool for studying the reliable lifespan of combustion chamber flame tubes.

[0006] With the continuous development of structural strength design technology, some initial achievements have been made in the field of aircraft engine simulation component design. However, the following issues remain: 1) Most of these efforts focus on the design of conventional stators or rotors, while few simulations of combustion chamber liner components that consider fluid-thermal-solid coupled loading are considered. 2) Most simulations utilize uniaxial tension, which cannot accurately reflect the actual loading conditions of the liner and combustion chamber.

[0007] The existing Chinese invention patent application CN 202111053011.2 "A method for designing a simulation specimen of the hole structure characteristics of a combustion chamber casing" discloses a method for designing a simulation specimen of the hole structure characteristics of a combustion chamber casing. For periodically arranged hole structures, this method ignores the influence of adjacent hole structures on the crack propagation path, and incompletely simulates the crack propagation behavior of the actual structure of the combustion chamber flame tube.

[0008] The existing Chinese invention patent application CN 202410373381.1 "A thermal fatigue simulation part and thermal fatigue test method for a reflow combustion chamber flame tube" discloses a thermal fatigue simulation part and a thermal fatigue test method for a reflow combustion chamber flame tube. The thermal fatigue simulation part of this patent can only simulate the performance of the reflow combustion chamber flame tube under thermal fatigue conditions, and the simulation of the actual load conditions of the combustion chamber flame tube is incomplete. The design and processing are relatively complex, and require higher cost and processing accuracy than flat parts. Summary of the Invention

[0009] To address these technical issues, the present invention provides a design method for a simulated component featuring periodically arranged porous thin-walled combustion liner. Using a biaxially stretched flat plate as the basic configuration, the simulated component fully reflects the actual loading conditions of potential failure locations (cooling holes) in the combustion liner, while maintaining the same design principles across failure modes such as low-cycle fatigue and creep-fatigue. This method provides experimental support for subsequent evaluation of crack growth life and verification of critical crack size in combustion liner models.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] A method for designing a characteristic simulation component of a periodically arranged porous thin-walled combustion chamber flame tube comprises the following steps:

[0012] Step (1): Obtain the geometric model, material performance parameters, and typical operating conditions of the combustion chamber flame tube, conduct a real structural static strength analysis based on the fluid-thermal-solid coupled load characteristics in the actual operating conditions of the combustion chamber flame tube, obtain the magnitude and direction of the first principal stress of the structure, determine the location with the maximum first principal stress as the dangerous location, and use the plane perpendicular to the first principal stress as the initial crack plane;

[0013] Step (2): Use crack propagation analysis software to simulate the real structure, assume that there is an initial crack at the dangerous point, set the required material parameters and crack propagation model parameters, calculate the critical crack size of the dangerous point, and focus on the influence of the periodically arranged porous structure on the crack propagation path based on the analysis results. Obtain the crack propagation path of the real structure, extract the change law of the stress intensity factor on the path, determine the geometric dimensions that have a major impact on the stress intensity factor on the crack propagation path, and preliminarily design the geometric shape of the simulation component assessment part under the premise of ensuring that the key geometric dimensions remain unchanged;

[0014] Step (3): Considering that the combustion chamber flame tube is subjected to a large circumferential load as well as an axial load, a biaxially loaded flat plate simulation part is designed, and the holding section is wedge-shaped. A biaxial tensile testing machine is used to apply mutually perpendicular biaxial tensile loads in the plane of the simulation part. The strength is checked with reference to the actual working conditions of the real structure, and the simulation part is subjected to displacement loading. By adjusting the load and the biaxial load ratio, the first principal stress distribution of the simulation part is ensured to be consistent with the real structure, and the clamping section should have sufficient strength reserve relative to the test section;

[0015] Step (4): Use crack propagation analysis software to simulate the simulated part, insert an initial crack in the first principal stress plane of the simulated part, and adjust the width of the simulated part and the periodic arrangement of the porous structure so that the stress intensity factor under different crack lengths is consistent with the real structure;

[0016] Furthermore, the material performance parameters in step (1) include the material's density, elastic modulus, Poisson's ratio, linear expansion coefficient, and thermal conductivity.

[0017] Furthermore, the key geometric dimensions in step (2) include the aperture size of the cooling hole of the combustion chamber flame tube, the angle between the hole centerline and the surface normal, the thickness of the flame tube, and the spatial arrangement of the inclined holes of the porous part, which must be consistent with the actual component. According to the engineering detectable crack length standard, the line crack length is 0.76 mm and the corner crack length is 0.38 mm.

[0018] Furthermore, the load adjustment in step (3) is specifically achieved by a servo mechanism to adjust the load ratio (σ x :σ y ) is precisely controlled to make the first principal stress distribution of the simulated part consistent with the real structure.

[0019] Furthermore, the specific steps of step (4) include: selecting a crack propagation model, and ensuring that the stress intensity factor of the characteristic simulation part at different crack lengths is consistent with that of the real component by adjusting the arrangement of the test section holes and the width of the simulation part along the crack propagation direction, mainly considering the influence of adjacent holes. The same large first principal stress on the adjacent hole structure may cause a change in the crack propagation path, and adjusting the arrangement of the porous structure so that the crack propagation path of the simulation part and the stress intensity factor at different crack lengths are consistent with the real structure.

[0020] The beneficial effects of the present invention compared with the prior art are:

[0021] Chinese invention patent application CN 202111053011.2, CN 202410373381.1 proposed a simulation part for the hole structure characteristics of the combustion chamber casing, as well as a design method for a thermal fatigue simulation part and a thermal fatigue test. While ensuring the geometric shape, it basically simulated the load conditions of the hot end stator. However, it can often only simulate stress in a single direction or cannot fully consider the fluid-thermal-solid coupling load characteristics of the hot end stator in the aircraft engine. At the same time, it does not consider the influence of the periodically arranged porous structure on the crack propagation path of the component, and the fatigue behavior simulation of the combustion chamber is incomplete. Starting from the actual load conditions of the combustion chamber flame tube, the present invention proposes and designs a biaxial tensile simulation part, integrates a high-temperature environment module, simulates the actual working conditions of the combustion chamber flame tube, and covers the extreme service conditions of the flame tube. By changing the hole structure arrangement of the simulation part test section and changing the width of the simulation part in the crack propagation direction, it can better simulate the crack propagation path of the real structure and the stress intensity factor under different crack lengths. At the same time, the flat simulation part greatly reduces the processing difficulty and processing cost, significantly shortens the iterative optimization cycle, and provides strong support for in-depth research on the combustion chamber flame tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a flow chart of a method for designing a periodically arranged porous thin-walled combustion chamber flame tube characteristic simulation component of the present invention;

[0023] Figure 2 Schematic diagram of the circumferential stress and axial stress gradient of a real component;

[0024] Figure 3 This is a schematic diagram of the variable amplitude displacement loading method of the simulation component;

[0025] Figure 4 Schematic diagram of the variation of stress intensity factors of the real structure and the simulated component with crack propagation under variable amplitude displacement loading;

[0026] Figure 5 Design drawing for simulation parts. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0028] The following further illustrates the technical solution of a method for designing a characteristic simulation component of a periodically arranged porous thin-walled combustion chamber flame tube through embodiments in conjunction with the accompanying drawings.

[0029] The crack propagation behavior of thin-walled components such as flame tubes is affected by the stress concentration effect caused by the porous structure and the complex thermal load. The prediction of the crack propagation path and the evaluation of the critical size under the multi-axial stress state are the design difficulties of the simulation parts. Therefore, the present invention proposes a design method for a characteristic simulation part of a periodically arranged porous thin-walled combustion chamber flame tube, including: conducting a fluid-thermal-solid coupling analysis under the actual structural service environment, obtaining the temperature field distribution and the magnitude and direction of the first principal stress of the combustion chamber flame tube, and determining the location with the maximum first principal stress as the dangerous location; inserting an initial crack in the dangerous location of the real component and conducting a numerical simulation of crack propagation to extract the variation law of the stress intensity factor along the crack propagation path; on the basis of maintaining the key geometric features of the periodically arranged porous structure, designing the simulation part configuration as a biaxial flat plate tensile part, and matching the stress gradient distribution of the real component through the optimization of the porous array parameters; using a biaxial tensile testing machine to apply multiaxial loads to the simulation part, and controlling the crack propagation path by coordinating the biaxial load ratio to ensure that the stress intensity factor amplitude under different crack lengths is consistent with that of the real component. Compared with existing uniaxial loading simulation parts, the present invention achieves innovative breakthroughs in the parametric modeling of periodic porous structures and coordinated control of multi-axial loads. It can more realistically reflect the stress redistribution characteristics of the porous thin-walled structure of the flame tube, and provide an effective experimental means to obtain the crack propagation law and critical crack size of key parts. It has important engineering value for the damage tolerance assessment and life prediction of aircraft engine combustion chambers.

[0030] Specifically, if Figure 1 As shown, the present invention includes the following steps:

[0031] Step (1) obtains the geometric model, material performance parameters, typical operating conditions and failure modes of the combustion chamber flame tube, conducts a real structural static strength analysis based on the fluid-thermal-solid coupling load characteristics in the actual operating conditions of the combustion chamber flame tube, determines the maximum first principal stress position as the dangerous position, and uses the plane perpendicular to the first principal stress as the initial crack plane, and extracts the temperature distribution characteristics of the assessment area;

[0032] Step (2) uses the crack propagation analysis software FRANC3D, assumes that there is an initial crack at the dangerous point, and gives the crack propagation model parameters of the material. Combined with the analysis results, the focus is on the influence of the periodically arranged porous structure on the crack propagation path, the stress intensity factor variation law on the crack propagation path is extracted, and the geometric dimensions that have a major impact on the stress intensity factor on the crack propagation path are determined. Under the premise of ensuring that the key geometric dimensions remain unchanged, the geometric shape of the simulation component assessment part is preliminarily designed. The key geometric dimensions focus on the porous arrangement structure, and refer to the combustion chamber flame tube cooling hole. The key dimensions include the aperture size of the cooling hole, the angle between the hole center line and the surface normal, the flame tube thickness, and the spatial arrangement law of the inclined holes of the porous component. The crack propagation model selected is the Paris formula:

[0033] (1)

[0034] Where a is the crack length, N is the number of cycles, It indicates the expansion of crack length a after each load cycle. C and n are material constants. Define the difference between the maximum and minimum stress intensity factors for the stress intensity factor range ( ), C reflects the material's ability to resist fatigue crack growth, and n represents the sensitivity of the crack growth rate to the range of stress intensity factors;

[0035] Step (3): Considering that the combustion chamber flame tube is subjected to large circumferential loads as well as axial loads, a biaxially loaded flat plate simulation is designed, with the support section being wedge-shaped. A biaxial tensile testing machine is used to apply mutually perpendicular biaxial tensile loads in the plane of the simulation, and strength verification is performed with reference to the actual working conditions of the real structure. The simulation is subjected to displacement loading, and the load is adjusted through the servo mechanism to achieve load ratio (σ x : σ y )( σ x represents the horizontal load applied by the biaxial tensile testing machine, σ y The vertical load (representing the vertical load applied by the biaxial tensile testing machine) is precisely controlled to ensure that the primary principal stress distribution of the simulated part is consistent with the actual structure. The clamping section should have sufficient strength reserve relative to the test section to ensure that the simulated part does not break at the clamping section during the test.

[0036] Step (4) is to carry out a simulation of crack propagation of the simulated component. The given initial crack size and crack propagation model are consistent with those in step (2). By adjusting the arrangement of the test section holes and the width of the simulated component along the crack propagation direction, the crack propagation path is controlled to be consistent with the real structure, and the stress intensity factor under different crack lengths is controlled to be consistent with the real structure. The arrangement of the porous structure of the inclined holes mainly considers the influence of adjacent holes. The hole center lines of different rows of hole structures form a certain angle with the surface normal. For the crack propagation of a certain hole, it generally starts to propagate from the position where the hole center line forms an acute angle with the surface normal. In the process of crack propagation, the first principal stress is much smaller than the danger point because the hole center line of the next row forms an obtuse angle with the surface normal. Therefore, the different rows of hole structures have little effect on the crack propagation path, while the same large first principal stress on the adjacent hole structures in the same row may cause the change of the crack propagation path.

[0037] Figure 2 The figure shows the schematic diagram of the circumferential stress and axial stress gradient of a real component; Figure 3 Shown is a schematic diagram of the variable amplitude displacement loading method of the simulation component. Figure 4 The test results show that the stress intensity factor of the simulated component changes with crack extension under constant load, the stress intensity factor changes with crack extension under variable amplitude load, and the stress intensity factor of the real structure changes with crack extension. The analysis results show that the loading method of variable amplitude load can ensure that the stress intensity factor of the simulated component is within the range of ±10% of the stress intensity factor of the real structure. Figure 5 A drawing of a simulation part with structural characteristics of a periodically arranged porous thin-walled combustion chamber flame tube designed for the present invention. The main structure is two mutually perpendicular flat plate structures. The overlapping part of the two plates is the test section. The test section has a periodically arranged porous structure consistent with the actual structure. The clamping section of the simulation part is wedge-shaped and is connected to the testing machine through the clamping section.

[0038] The above embodiments are merely provided to describe specific embodiments of the present invention and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. Various equivalent substitutions and modifications made without departing from the spirit and principles of the present invention are intended to be encompassed within the scope of the present invention.

Claims

1. A method for designing a characteristic simulation component of a periodically arranged porous thin-walled combustion chamber flame tube, characterized in that: The steps include: Step (1): Obtain the geometric model, material performance parameters, and typical operating conditions of the combustion chamber flame tube, conduct a real structural static strength analysis based on the fluid-thermal-solid coupling load characteristics in the actual operating conditions of the combustion chamber flame tube, and determine the dangerous points; Step (2): Simulate the real structure to determine the geometric dimensions that have a major impact on the stress intensity factor on the crack propagation path, and preliminarily design the geometric shape of the simulation component under the premise of ensuring that the key geometric dimensions remain unchanged; Step (3): Considering that the combustion chamber flame tube is subjected to a large circumferential load as well as an axial load, a biaxially loaded flat plate simulation part is designed, with the support section being wedge-shaped; a biaxial tensile testing machine is used to apply mutually perpendicular biaxial tensile loads in the plane of the simulation part; strength verification is performed with reference to the actual working conditions of the real structure, and displacement loading is performed on the simulation part. By adjusting the load and the biaxial load ratio, the first principal stress distribution of the simulation part is ensured to be consistent with the real structure; Step (4): simulate the simulated part, insert an initial crack in the first principal stress plane of the simulated part, and adjust the width of the simulated part and the periodic arrangement of the porous structure so that the stress intensity factor under different crack lengths is consistent with the real structure.

2. The method for designing a periodically arranged porous thin-walled combustion chamber flame liner characteristic simulation component according to claim 1, characterized in that: The step (1) comprises: obtaining the magnitude and direction of the first principal stress of the structure, determining the location of the maximum first principal stress as the dangerous location, and taking the plane perpendicular to the first principal stress as the initial crack plane.

3. The method for designing a periodically arranged porous thin-walled combustion chamber flame liner characteristic simulation component according to claim 1, characterized in that: The step (2) comprises: assuming that an initial crack exists at the dangerous point determined in step 1, setting the required material parameters and crack propagation model parameters, calculating the critical crack size of the dangerous point, focusing on the influence of the periodically arranged porous structure on the crack propagation path in combination with the analysis results, obtaining the crack propagation path of the real structure, and extracting the variation law of the stress intensity factor on the path, thereby determining the geometric dimensions that have a major influence on the stress intensity factor on the crack propagation path.

4. The method for designing a characteristic simulation component of a periodically arranged porous thin-walled combustion chamber flame liner according to claim 1, characterized in that: In the step (3), the clamping section has sufficient strength reserve relative to the testing section.

5. The method for designing a characteristic simulation component of a periodically arranged porous thin-walled combustion chamber flame liner according to claim 1, characterized in that: The material performance parameters in step (1) include the material's density, elastic modulus, Poisson's ratio, linear expansion coefficient, and thermal conductivity.

6. The method for designing a characteristic simulation component of a periodically arranged porous thin-walled combustion chamber flame liner according to claim 1, characterized in that: The key geometric dimensions in step (2) include the diameter of the cooling holes of the combustion chamber flame tube, the angle between the hole centerline and the surface normal, the thickness of the flame tube, and the spatial arrangement of the inclined holes of the porous part, all of which are consistent with the real component.

7. The method for designing a characteristic simulation component of a periodically arranged porous thin-walled combustion chamber flame liner according to claim 6, characterized in that: According to the engineering detectable crack length standard, the length of the linear crack is 0.76mm and the length of the corner crack is 0.38mm.

8. The method for designing a characteristic simulation component of a periodically arranged porous thin-walled combustion chamber flame liner according to claim 1, characterized in that: The load adjustment in step (3) is specifically achieved by the servo mechanism to adjust the load ratio (σ x : σ y ) is precisely controlled to make the first principal stress distribution of the simulated part consistent with the real structure; σ x represents the horizontal load applied by the biaxial tensile testing machine, σ y Represents the vertical load applied by the biaxial tensile testing machine.

9. The method for designing a characteristic simulation component of a periodically arranged porous thin-walled combustion chamber flame liner according to claim 1, characterized in that: The step (4) includes: selecting a crack propagation model, and adjusting the arrangement of the test section holes and the width of the simulation component along the crack propagation direction to ensure that the stress intensity factor of the characteristic simulation component at different crack lengths is consistent with that of the real component.

10. The method for designing a characteristic simulation component of a periodically arranged porous thin-walled combustion chamber flame liner according to claim 9, characterized in that: The arrangement of the porous structure is adjusted so that the crack propagation path of the simulated part and the stress intensity factor at different crack lengths are consistent with the real structure.

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