Method for determining structure of composite material special-shaped air entraining pipe and special-shaped air entraining pipe

Abstract

A method for determining a composite material special-shaped air entraining pipe structure comprises the following steps that a metal air entraining pipe is provided, the service working condition, a structure inheritance area and a structure optimization area of the metal air entraining pipe are determined, an inspection model is established, material performance conditions and structure performance conditions are determined according to the service working condition, and then allowable materials are determined; performing iterative optimization on the structure optimization area of the air entraining pipe made of the allowable material in the test model to obtain an iterative model; carrying out weight inspection and strength inspection on the iterative model, and carrying out further iteration to obtain an optimization model; and carrying out formability test on the optimization model, and carrying out iterative optimization to obtain the finally determined composite material special-shaped air entraining pipe. By means of the method, the composite material special-shaped air entraining pipe used for replacing a metal air entraining pipe can be designed, the design period is shortened, the part structure is optimized, and the overall weight of an engine is reduced. The invention further provides the special-shaped air entraining pipe.

Description

Technical Field

[0001] The invention belongs to the field of aeroengines, and in particular relates to a method for determining the structure of a composite material special-shaped air duct and the special-shaped air duct. Background Art

[0002] At present, most of the special-shaped air ducts in the air system of traditional aircraft engines are made of steel or various high-temperature alloys, and are formed by integral machining or casting first and then machining. On the one hand, metal materials have high density and heavy weight, which is not conducive to the lightweight design of aircraft engines and the energy-saving and emission reduction requirements of the industry; on the other hand, metal processing has a long cycle, complex process, and high cost, which is not conducive to the optimization of the economic efficiency of engine materials. Therefore, replacing the special-shaped air duct with a composite material from a metal material has good prospects in terms of economy. However, compared with metal materials, composite materials have very different mechanical properties and manufacturing methods. Simply replacing the material of the special-shaped air duct from metal to composite materials cannot meet the design requirements, and it is also necessary to optimize the structure of the special-shaped air duct in a targeted manner. Designing a new special-shaped air duct structure for composite materials is labor-intensive and has a long development cycle. Therefore, providing a method for quickly determining the structure of a composite air duct based on an existing metal air duct has high practical value for improving the design efficiency of aircraft engines. Summary of the invention

[0003] The purpose of the present invention is to provide a method for determining the structure of a composite material special-shaped air duct, and to provide a solution for obtaining the structural design of a composite material air duct based on an existing metal air duct. The present invention also provides a special-shaped air duct.

[0004] According to an embodiment of one aspect of the present invention, there is provided a method for determining the structure of a composite material special-shaped air duct, which is used for manufacturing a composite material special-shaped air duct that replaces a metal air duct, and comprises the following steps: determining the service conditions, structural inheritance area and structural optimization area of ​​the metal air duct, and establishing a verification model; determining the material performance conditions and structural performance conditions of the composite material according to the service conditions; determining the allowable materials used for manufacturing the special-shaped air duct according to the material performance conditions, substituting the allowable materials into the verification model, and performing structural optimization on the structural optimization area according to the structural performance conditions to obtain an iterative model; performing weight inspection and strength inspection on the iterative model, and performing iterative optimization to obtain an optimized model; performing formability inspection on the optimized model, and performing iterative optimization to obtain the final determined structure of the composite material special-shaped air duct.

[0005] Through the above method, the rapid design of the composite material special-shaped air duct structure can be achieved on the basis of the existing structure, reducing the workload of the engine part structure design, and reducing the workload caused by part changes while reducing the overall weight of the engine.

[0006] Furthermore, in some embodiments, the service conditions include service temperature, service pressure and / or service air flow and service connection stress; the structural inheritance area includes the connection interface of the special-shaped air duct, the fixing hole and the outer contour surface that reaches the minimum allowable gap with adjacent parts.

[0007] Furthermore, in some embodiments, the material performance conditions include the maximum operating temperature, tensile strength, shear strength and fatigue strength of the material, and the structural performance conditions include the air bleed area, tube wall thickness and bending radius of the special-shaped air bleed tube under service conditions.

[0008] Furthermore, in some embodiments, the method for structurally optimizing the structural optimization area includes: changing the wall thickness of the special-shaped air duct, adjusting the fillet radius, changing the area and thickness of the flange at the end of the special-shaped air duct, and adjusting the inner and outer contour surfaces.

[0009] Furthermore, in some embodiments, the strength test includes a static strength test and a vibration strength test.

[0010] Furthermore, in some embodiments, the vibration strength test includes frequency response analysis and maximum tensile, compressive and shear strain tests at the resonant frequency.

[0011] Furthermore, in some embodiments, the moldability test includes a feasibility test of fiber laying in the process of manufacturing the special-shaped air duct using the allowable material and a test of demoulding performance after curing.

[0012] Furthermore, in some embodiments, the formability test is performed based on an autoclave molding process.

[0013] Furthermore, in some embodiments, the condition for the weight inspection is that the weight of the optimized model is not higher than 55% of the metal air duct.

[0014] According to another embodiment of the present invention, there is provided a special-shaped air duct, which is made of a composite material and has the composite material special-shaped air duct structure provided in any of the aforementioned embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A structural model of a metal air duct to be replaced in an embodiment;

[0016] Figure 2 A composite material special-shaped air duct structure model provided in an embodiment;

[0017] Figure 3a A tensile strain cloud diagram of a composite material special-shaped air duct structure model in an embodiment;

[0018] Figure 3b A compression strain cloud diagram of a composite material special-shaped air duct structure model in an embodiment;

[0019] Figure 3c This is a shear strain cloud diagram of a composite material special-shaped air duct structure model in an embodiment;

[0020] Figure 4a This is a first-order 213 Hz analysis vibration shape diagram of a composite material special-shaped air duct structure model in an embodiment;

[0021] Figure 4b It is a second-order 412Hz analysis vibration shape diagram of the composite material special-shaped air duct structure model in one embodiment;

[0022] Figure 4c The third-order 608 Hz analysis vibration shape diagram of the composite material special-shaped air duct structure model in one embodiment;

[0023] Figure 4d It is a fourth-order 638Hz analysis vibration shape diagram of the composite material special-shaped air duct structure model in one embodiment;

[0024] Figure 4e The fifth-order 940 Hz analysis vibration shape diagram of the composite material special-shaped air duct structure model in one embodiment;

[0025] Figure 4f : This is a sixth-order 979 Hz analysis vibration shape diagram of a composite material special-shaped air duct structure model in an embodiment;

[0026] Figure 5 Schematic diagram of the composite material special-shaped air duct composite mold structure in one embodiment.

[0027] The purpose of the above drawings is to explain the present invention in detail so that those skilled in the art can understand the technical concept of the present invention, but it is not intended to limit the present invention. For the sake of brevity, the above drawings only schematically show the contents related to the technical features of the present invention, and do not provide the complete structure and all details strictly in accordance with the actual proportion. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0029] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The phrase appearing in various locations in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive independent or alternative embodiments. Those skilled in the art should be able to understand that the embodiments herein may be combined with other embodiments without causing structural conflicts.

[0030] In the description of this article, unless otherwise clearly specified and limited, the technical terms "install", "connect", "connect", etc. should be understood in a broad sense. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of this application can be understood according to specific circumstances.

[0031] In the description of this document, terms indicating orientation or positional relationships, such as "up", "down", "left", "right", "horizontal", "vertical", "height", "length", and "width", are intended to accurately describe the embodiments and simplify the description, but are not intended to limit the parts or structures involved to have a specific orientation, be installed or operate in a specific orientation, and should not be construed as a limitation on the embodiments in this document.

[0032] In the description of this article, the terms "first", "second" and the like are only used to distinguish different objects, and cannot be understood as indicating relative importance or limiting the quantity, specific order or primary and secondary relationship of the described technical features. In the description of this article, the meaning of "plurality" is at least two.

[0033] With the requirements of lightweight and low-cost aircraft engines, new requirements are put forward for the selection of special-shaped air ducts in the air system. As a new type of material with high specific strength and low density, high-performance thermosetting composite materials have received widespread attention in the aerospace field and have become a new development direction for the application of composite materials in commercial aircraft engines. How to reasonably design the structure of composite special-shaped air ducts to meet the performance and strength requirements while minimizing the design changes to surrounding parts and replacing metal special-shaped air ducts to perform their functions and roles is an important problem that needs to be overcome in the promotion of composite special-shaped air duct technology.

[0034] In order to solve the above problems, an embodiment of one aspect of the present invention provides a method for determining the structure of a composite material special-shaped air duct, which is used to manufacture a composite material special-shaped air duct that replaces the existing metal air duct, and the following steps are adopted:

[0035] Working condition input: Considering the service environment, service temperature and load conditions of the special-shaped air duct, the worst load state is selected as the main working condition input. According to the working characteristics, installation and assembly status and stress state of the special-shaped air duct, the structural inheritance area and structural optimization area in the original structure of the metal air duct are determined, and three-dimensional modeling is performed as a test model for subsequent simulation optimization. The structure of the structural inheritance area remains unchanged, and the structural optimization area needs to be iteratively optimized. According to the main working condition input, determine the material performance conditions and structural performance conditions that the special-shaped air duct parts need to meet.

[0036] Material selection: The selection of thermosetting resin is mainly based on the working environment temperature, and the optional types include epoxy resin, bismaleimide resin and polyimide resin, etc. For fiber materials, various types of glass fiber or carbon fiber materials can be selected. When selecting materials, mechanical properties and costs are taken into consideration. The material performance conditions are determined by referring to the service conditions to determine the range of allowable materials. Considering the general service conditions of the special-shaped air duct, epoxy resin-based T300-grade carbon fiber reinforced high-performance prepreg fabric can be selected in some optional embodiments.

[0037] Structural optimization: Considering the performance characteristics and molding requirements of thermosetting composite materials, the allowable materials are substituted into the inspection model, and the structure of the structural optimization area is iterated according to the structural performance conditions to obtain an iterative model.

[0038] Verification and inspection: Perform corresponding static analysis and vibration analysis such as modal analysis and frequency response analysis on the iterative model to ensure that the maximum strain is less than the allowable value of the material; calculate the weight of the iterative model to determine the weight reduction ratio relative to the original metal special-shaped air duct. Perform iterative optimization based on the verification and inspection results to obtain the model to be optimized.

[0039] Formability test: Considering the complex structure of special-shaped air duct parts and the difficulty in demolding, the split combination mold is analyzed and designed to assist in molding. At the same time, the optimization model is adjusted according to the mold demolding requirements. After iterative formability optimization, the final composite material special-shaped air duct structure is obtained.

[0040] In a preferred embodiment, the metal profiled air duct structure to be replaced is as follows: Figure 1As shown, the bleed pipe is machined by casting titanium alloy. The upper end interface 1 of the bleed pipe is circular, the wall thickness of the bleed pipe body 6 is 2mm, the lower end interface 2 of the bleed pipe is on the same curved surface as the arc flange 4, the thickness of the flange 4 is 4mm, and nine bolt through holes 5 are arranged on the peripheral edge of the flange 4. When in use, the bleed pipe is fixed to the mounting seat of the casing through the bolt holes 5 in conjunction with the connecting bolts. The lower end interface 2 of the bleed pipe introduces the external flow channel gas into the pipe. The annular protrusion 3 on the upper end interface 1 of the bleed pipe cooperates with the clamp to connect with another section of flexible pipeline to guide the introduced gas to the designated position. Its service temperature is 274k-355k, the contact medium is air, the pressure caused by the inner cavity of the pipeline does not exceed 150kPa, and it bears the vibration load of the engine. The inspection model of the special-shaped bleed pipe is established in the simulation analysis software, and the principle of determining the structural inheritance area is to maintain the current installation interface, maintain the current pipeline bleed area, maintain the current connector position, avoid interference with other parts, and meet the strength requirements of the parts. Furthermore, it is determined that the structural inheritance area includes: the upper end interface 1 of the air duct, the annular protrusion 3, the lower end interface 2 of the air duct, and the bolt through holes 5 (the number, position and size remain unchanged). At the same time, the cross-sectional area of ​​the air duct body remains unchanged to ensure that the air flow rate does not change under service conditions; the remaining areas are structural optimization areas.

[0041] In a preferred embodiment, the composite material special-shaped air duct adopts the autoclave molding process, and uses epoxy resin-based T300 grade carbon fiber reinforced high-performance prepreg fabric and CYCOM 970 / PWC T300 3K grade thermosetting composite materials that meet the material performance conditions as allowable materials to manufacture the special-shaped air duct. The performance parameters of the allowable materials are substituted into the test model, the structural performance conditions are substituted and finite element analysis is performed, and the structural optimization area is iteratively optimized. According to the simulation analysis results, for the area near the bolt through hole 5 where stress is concentrated, it is necessary to increase the diameter of the flange 4 so that the distance between the bolt through hole 5 and the edge of the flange 4 is increased from 3mm to 6mm, and the pipe wall thickness is increased to 3mm to improve the pipe wall strength, and the optimized model is obtained. At the same time, it is checked that the minimum gap between the pipe body 6 and the surrounding parts after the pipe wall thickness is increased still meets the structural design requirements. According to the weight test calculation, the weight of the optimized model is about 50% of the original metal air duct.

[0042] Next, the optimized model was tested for formability in combination with the manufacturing process and formability characteristics of fiber-reinforced resin-based composite materials. To avoid a thick transition zone during laying, the thickness of the flange 4 was set to 3 mm, the same as the optimized pipe wall, and the radius of the fillet 7 between the pipe body 6 and the flange 4 was increased to 10 mm to avoid defects such as bridging and fiber breakage caused by a small bending radius during laying, thereby improving laying efficiency; the outer contour of the flange 4 was simplified to eliminate Figure 1The protruding area A in the middle reduces the subsequent processing steps, and only machining chamfering is required to complete the processing. At the same time, considering the molding and demoulding process of the composite material special-shaped air duct, the design is as follows Figure 5 The composite mold shown is made of metal and includes an inner mold consisting of a first core mold 8 and a second core mold 9 and an outer mold consisting of a first outer mold 10, a second outer mold 11, and a third outer mold 12. The inner mold is used to form the inner cavity of the air duct, and the outer mold forms the outer contour of the air duct. According to the combination of the molds and the demoulding method, the optimized model structure of the air duct is further optimized to facilitate demoulding.

[0043] Finally, strength test and weight test are carried out here, and iteration is repeated to finally determine the composite material special-shaped air duct structure. Static strength analysis is carried out on the final composite material special-shaped air duct structure, and its tensile strain cloud diagram is shown as follows: Figure 3a As shown, the maximum strain (1 times) is 2690, the maximum strain (2 times) is 5380, and the allowable value is 5924; the compression strain cloud diagram is as follows Figure 3b As shown, the maximum strain (1 times) is 2380, the maximum strain (2 times) is 4760, and the allowable value is 4983; the shear strain cloud diagram is as follows Figure 3c As shown in the figure, the maximum strain (1 times) is 1370, the maximum strain (2 times) is 2740, and the allowable value is 33161. It can be seen that its static strength meets the requirements. Figures 4a to 4f As shown, the frequency response analysis was carried out in the XYZ directions respectively. The maximum tensile, compressive and shear strains at the first six resonant frequencies were all less than their allowable values, meeting the strength requirements.

[0044] Before optimization, the original metal air duct weighed 1.844kg, and the final composite material special-shaped air duct weighed 0.896kg, with an actual weight reduction of 51.4%.

[0045] It should be understood that the order of the steps in the above embodiments is not unique. According to the actual structure of the parts and the specific simulation optimization process, one or more steps may undergo multiple optimization iterations, and the order of different steps may also be adaptively adjusted.

[0046] Another embodiment of the present invention provides a composite material special-shaped air duct, which is designed and manufactured using the method for determining the structure of a composite material special-shaped air duct provided in any of the above embodiments. The special-shaped air duct has a light structure and high strength, can replace the original metal air duct and meet the performance requirements of the service condition, and reduce the weight and manufacturing cost of the aircraft engine.

[0047] The purpose of the above embodiments is to further explain the present invention in detail in conjunction with the accompanying drawings so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, the optimization or equivalent replacement of the methods or structures involved, as well as the combination of implementation methods in different embodiments without conflict between the structure and the principle, all fall within the protection scope of the present invention.

Claims

1. A method for determining the structure of a composite material special-shaped air duct, characterized in that: The method for manufacturing a composite material special-shaped air duct replacing a metal air duct comprises the following steps: Determine the service conditions, structural inheritance areas and structural optimization areas of the metal air duct, and establish a test model; Determining material performance conditions and structural performance conditions of the composite material according to the service conditions; Determining the allowable material used for manufacturing the special-shaped air duct according to the material performance conditions, substituting the allowable material into the inspection model, and optimizing the structure optimization area according to the structural performance conditions to obtain an iterative model; Performing strength test and weight test on the iterative model, and performing iterative optimization to obtain an optimized model; The optimized model is subjected to a formability test and iterative optimization is performed to obtain the final composite material special-shaped air duct structure.

2. The method for determining the structure of a composite material special-shaped air duct according to claim 1, characterized in that: The service conditions include service temperature, service pressure and / or service air flow and service connection stress; the structural inheritance area includes the connection interface of the special-shaped air duct, the fixing hole and the outer contour surface that reaches the minimum allowable gap with adjacent parts.

3. The method for determining the structure of a composite material special-shaped air duct according to claim 1 or 2, characterized in that: The material performance conditions include the maximum operating temperature, tensile strength, shear strength and fatigue strength of the material, and the structural performance conditions include the air bleed area, tube wall thickness and bending radius of the special-shaped air bleed pipe under service conditions.

4. The method for determining the structure of a composite material special-shaped air duct according to claim 1 or 2, characterized in that: The method for structural optimization of the structural optimization area includes: changing the wall thickness of the special-shaped air duct, adjusting the fillet radius, changing the area and thickness of the flange at the end of the special-shaped air duct, and adjusting the inner and outer contour surfaces.

5. The method for determining the structure of a composite material special-shaped air duct according to claim 1 or 2, characterized in that: The strength test includes a static strength test and a vibration strength test.

6. The method for determining the structure of a composite material special-shaped air duct according to claim 5, characterized in that: The vibration strength test includes frequency response analysis and maximum tension, compression and shear strain tests at resonant frequencies.

7. The method for determining the structure of a composite material special-shaped air duct according to claim 1 or 2, characterized in that: The formability test includes a feasibility test of fiber laying in the process of manufacturing the special-shaped air duct using the allowable material and a test of demoulding performance after curing.

8. The method for determining the structure of a composite material special-shaped air duct according to claim 7, characterized in that: The formability test is conducted based on an autoclave molding process.

9. The method for determining the structure of a composite material special-shaped air duct according to claim 1 or 2, characterized in that: The condition for the weight inspection is that the weight of the optimized model is not higher than 55% of the metal air duct.

10. A special-shaped air duct, characterized in that: The special-shaped air duct is made of composite material and has the special-shaped air duct structure provided by the method for determining the structure of a special-shaped air duct of a composite material according to any one of claims 1 to 9.

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