Turbofan engine air inlet bird impact simulation analysis method

Abstract

The invention aims to provide a simulated analysis method for bird impact of an air inlet of a turbofan engine, which can reduce the test cost and shorten the test period, and meanwhile, the test has good reliability. In order to achieve the purpose, the bird impact resistance design requirement of the air inlet channel is clarified by interpreting airworthiness terms, an air inlet channel bird impact simulation analysis working process is established, a bird body is simulated by adopting an SPH method, connecting pieces such as rivets and bolts are simulated by adopting an SPOTWELD unit, and a bird impact simulation model reflecting the real structure of the air inlet channel is established. Information such as deformation and damage of components in the impact process is obtained through turbofan aero-engine air inlet bird impact simulation analysis, and air inlet structure optimization design is guided.

Description

Technical Field

[0001] The invention relates to the field of turbofan engine design, and in particular to a turbofan engine inlet bird strike simulation analysis method. Background Art

[0002] The main function of the turbofan aircraft engine inlet is to provide the engine with a stable and uniform intake airflow and to decelerate and increase the pressure to ensure that the engine works stably and reliably during the flight of the aircraft. The inlet has functional design requirements such as anti-bird strike, noise reduction, anti-icing, fire prevention, ventilation and heat exchange.

[0003] like Figure 1 as well as Figure 2 The schematic diagram of the existing air inlet is shown. The air inlet is mainly composed of six parts: lip 91, front bulkhead 92, rear bulkhead 93, outer wall plate 94, inner wall plate 95, and docking ring 96. Among them, lip 91, front bulkhead 92, and rear bulkhead 93 are the main areas of the air inlet to resist bird strikes. The various parts of the air inlet are assembled and connected by rivets and bolts: lip 91 is connected to front bulkhead 92 by countersunk rivets, outer wall plate 94 is connected to front bulkhead 92 and rear bulkhead 93 by countersunk rivets, inner wall plate 95 is connected to lip 91 by countersunk high-locking bolts, inner wall plate 95 is connected to docking ring 96 by countersunk high-locking bolts, rear bulkhead 93 is connected to docking ring 96 by rivets, and docking ring 96 is connected to the front mounting flange of the fan casing by bolts.

[0004] In such Figure 1 to Figure 2 When the turbofan aircraft engine inlet shown in the figure hits a bird 97, the lip and the outer wall panel will be greatly deformed or damaged, and the entire inlet may even fall off the engine. Some important accessories of civil aircraft engines, such as anti-icing pipes, EEC, and lubricating oil pipes, are installed inside the fan compartment behind the rear bulkhead of the inlet. If these accessories are damaged when a bird hits the inlet, it will seriously affect the normal operation of the engine or engine fire, and may even cause serious consequences such as aircraft destruction and death. Although necessary measures have been taken during the operation of the aircraft (such as arranging bird repellent devices at the airport) to prevent bird strikes, bird strikes cannot be completely avoided during the flight. In the airworthiness clauses CCAR25.571(e) and FAR25.751(e), clear requirements are put forward for the anti-bird strike performance of the aircraft: the aircraft must be able to successfully complete the flight after being hit by a bird and causing structural damage. For this reason, it is necessary to carry out an inlet anti-bird strike performance test in the airworthiness of turbofan aircraft engines to verify its compliance with the clauses.

[0005] On the one hand, the bird strike test for airworthiness certification of the air inlet must be carried out using a complete air inlet; on the other hand, the bird strike test is a high-speed impact destructive test, which is expensive and has a long test cycle. Therefore, it is necessary to establish an accurate and reliable simulation and analysis method for bird strikes on the air inlet of a turbofan aircraft engine, and use numerical simulation analysis to perform anti-bird strike design during the product development of the turbofan aircraft engine inlet, which can greatly reduce the test cost and shorten the test cycle. Summary of the invention

[0006] The purpose of the present invention is to provide a turbofan engine inlet bird strike simulation analysis method, which can reduce the test cost, shorten the test cycle, and at the same time the test has good reliability.

[0007] A turbofan engine inlet bird strike simulation analysis method for achieving the above-mentioned purpose comprises the following steps:

[0008] a. Obtaining the design requirements of the air inlet;

[0009] b. Obtaining the design input of the air inlet;

[0010] c. Performing finite element modeling on the air intake duct, including performing finite element meshing on each component of the air intake duct and defining material models of each component of the air intake duct;

[0011] d. Check the established model, including unit type check, mesh quality check, material model and parameter check, and determine whether the parameters are consistent with the analysis input. If not, return to step c to modify the finite element model;

[0012] e. Perform finite element modeling on the bird body, including finite element meshing of the bird body and defining a material model for the bird body;

[0013] f. Definition of simulation calculation parameters, including definition of contact pairs, definition of flight speed, definition of boundary conditions, definition of hourglass energy control parameters, definition of calculation output parameters and definition of solution control parameters; wherein, the definition of contact pairs includes: point-to-surface contact is adopted between the bird body and the various parts of the air inlet structure, the bird body is defined as the slave surface, and the parts of the air inlet structure are defined as the master surface; surface-to-surface contact is adopted between the various parts of the air inlet, the one with smaller stiffness is used as the slave surface, and the one with larger stiffness is used as the master surface, or the one with larger speed is used as the slave surface, and the one with smaller speed is used as the master surface, or the one with smaller mesh size is used as the slave surface, and the one with larger mesh size is used as the master surface;

[0014] g. Calculate the files generated in the previous steps;

[0015] h. Post-process the calculation results;

[0016] i. Perform design compliance check based on the post-processing results of step h;

[0017] j. Based on step i, give a conclusion on whether the current bird strike resistance design of the air inlet structure meets the strength design requirements;

[0018] k. If the conclusion of step j is that the current air inlet does not meet the design requirements for bird strike resistance, perform the air inlet structure optimization design based on the calculation results of step h, and repeat steps c to j until the air inlet meets the design requirements for bird strike resistance strength.

[0019] In one or more embodiments, the design requirements obtained in step a include:

[0020] The air intake does not become detached from the engine; and

[0021] The rear bulkhead of the air inlet is not penetrated by the bird body and the deformation of the rear bulkhead cannot squeeze the accessories installed in the fan compartment and affect the normal operation of the engine.

[0022] In one or more embodiments, the design requirement for the air inlet to prevent it from falling off the engine is that the damage area of ​​the connecting bolts between the docking ring and the front mounting flange of the fan casing after the air inlet is hit by a bird is no more than 30° in the circumferential direction.

[0023] In one or more embodiments, the design input includes the air inlet geometry model, air inlet material parameters, and a bird body model.

[0024] In one or more embodiments, the method further includes the following steps after step b:

[0025] Design input checks.

[0026] In one or more embodiments, in step c, finite element mesh division is performed on the components of the air inlet duct, including simulating the panel skin in the lip, front bulkhead, rear bulkhead, outer wall panel and inner wall panel of the air inlet duct by using shell units, simulating the honeycomb in the parts by using solid units, and simulating the rivets and bolt connections by using SPOTWELD spot welding units; defining the material model of the components of the air inlet duct includes: defining the high strain rate parameters and unit failure parameters of the air inlet structural material, using equivalent failure plastic strain to characterize material failure for metal materials, and using maximum tensile / compressive strain to characterize material failure for composite materials.

[0027] In one or more embodiments, in step d, the element type check includes whether a 4-node shell element is used for the shell element, and whether an 8-node hexahedral element is used for the solid element.

[0028] In one or more embodiments, in step e, the bird body is simulated by smooth particles, the material model of the bird body is a uniform fluid mechanics material model, and the state equation is a Grüneisen state equation.

[0029] In one or more embodiments, after step e, the method further comprises the following steps:

[0030] Bird body model quality inspection.

[0031] In one or more embodiments, after step k, the following steps are further included:

[0032] Summarize steps a to k to prepare an inlet bird strike simulation analysis report.

[0033] The beneficial effects of the present invention are:

[0034] By interpreting the airworthiness clauses, the anti-bird strike design requirements for the turbofan aircraft engine inlet are clarified. At the same time, a turbofan aircraft engine inlet bird strike simulation analysis workflow is established to standardize the simulation analysis work. Through the turbofan aircraft engine inlet bird strike simulation analysis, the deformation, damage and other information of components during the impact process are obtained to guide the optimization design of the inlet structure. At the same time, by establishing a connection unit model, the force, damage and other information of connecting parts such as rivets and bolts during the impact process can be obtained to guide the optimization design of the inlet structure, so that the parts with excessive deformation or serious damage can be enhanced to achieve the optimization design of the inlet structure and ensure that the weight of the inlet is reduced as much as possible to improve the engine thrust ratio while meeting the anti-bird strike design requirements.

[0035] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0037] Figure 1 A schematic diagram of an existing turbofan aircraft engine air inlet is shown;

[0038] Figure 2 A schematic side view of an existing turbofan aircraft engine air inlet is shown;

[0039] Figure 3 A schematic diagram of a process flow of a turbofan engine inlet bird strike simulation analysis method according to some embodiments of the present application is shown;

[0040] Figure 4A front view schematic diagram of a smooth particle physics (SPH) bird body simulation model of a flying bird is shown;

[0041] Figure 5 A side schematic diagram of a smoothed particle physics (SPH) bird body simulation model of a flying bird is shown;

[0042] Figure 6 A schematic diagram of the bird strike simulation analysis results for a turbofan aircraft engine inlet is shown. DETAILED DESCRIPTION

[0043] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0045] At present, the traditional bird strike resistance design of current aircraft structures usually refers to the empirical formula provided in the Aircraft Design Manual Volume 9 - Loads, Strength and Stiffness to evaluate whether the aircraft structure is penetrated by a bird. However, the inventors have found in practice that the formula can only obtain the critical speed of the structure being penetrated by a bird when conducting bird strike resistance design of aircraft structures. By comparing the bird strike impact speed with the critical penetration speed, it is determined whether the structure is penetrated, but it is impossible to obtain information such as the deformation and damage form of each component during the bird strike process. In addition, the empirical formula is not suitable for bird strike resistance evaluation of connection feature areas such as splicing.

[0046] With the rapid development of computer technology, the finite element method is gradually being used to simulate and analyze the anti-bird strike of aircraft structures, but the simulation analysis method for bird strikes in the air inlet of turbofan aircraft engines is not yet mature. When modeling, the existing simulation analysis methods usually use common nodes or binding methods to simulate the connections between components such as rivets and bolts, but the inventors found that this cannot characterize the impact of the failure of the connector on the anti-bird strike performance of the structure. In addition, the current airworthiness terms only require that the aircraft structure can successfully complete the flight after being hit by a bird, and the anti-bird strike design requirements specifically for the air inlet of turbofan aircraft engines are not very clear.

[0047] In order to address the deficiencies of the prior art in solving the above-mentioned problems, the present application provides a turbofan engine inlet bird strike simulation analysis method, which can effectively implement the inlet bird strike simulation analysis, provide reliable analysis conclusions, and at the same time reduce the cost and cycle of the test.

[0048] like Figure 3 A schematic flow chart of a turbofan engine inlet bird strike simulation analysis method according to some embodiments of the present application is shown. Combined with the diagram, the turbofan engine inlet bird strike simulation analysis method includes the following steps:

[0049] Step S1: Obtaining the design requirements of the air intake duct.

[0050] Specifically, based on the requirements for the anti-bird strike performance of the aircraft in the airworthiness clauses CCAR25.571(e) and FAR25.571(e): the aircraft must be able to successfully complete the flight after being hit by a bird and causing structural damage. Through analysis, it can be seen that for the turbofan engine inlet, the inlet is a thin-walled structure and is only connected to the front mounting flange of the fan casing through a docking ring. In addition, the main function of the inlet is to provide the engine with a stable and uniform intake airflow and decelerate and increase the pressure of the intake airflow to ensure that the engine works stably and reliably during the flight of the aircraft. Based on the above characteristics, in order to ensure that the turbofan aircraft engine inlet can successfully complete the flight after being hit by a bird, in a specific embodiment, starting from the structural characteristics and main functions of the inlet, the design requirements obtained in step S1 include: 1) the inlet does not fall off the engine; and 2) the rear bulkhead of the inlet is not penetrated by the bird and the deformation of the rear bulkhead cannot squeeze the accessories installed in the fan compartment that affect the normal operation of the engine, thereby avoiding the occurrence of engine shutdown and other hazards that affect the safe flight of the aircraft.

[0051] Furthermore, in a specific embodiment, the design requirement for the air inlet to not fall off the engine is that after the air inlet is hit by a bird, the damage area of ​​the connecting bolts between the docking ring and the front mounting flange of the fan casing is no more than 30° in the circumferential direction. It has been verified that this quantitative parameter can effectively characterize the design requirement for the air inlet to not fall off the engine.

[0052] Step S2: Obtaining the design input of the air intake duct.

[0053] In a specific embodiment, the design input includes: an air inlet geometry model, air inlet material parameters and a bird model. Specifically, the bird model also includes the shape of the bird, the mass of the bird, the speed of the bird and the constitutive model parameters of the bird.

[0054] Optionally, the turbofan engine inlet bird strike simulation analysis method also includes step S3: design input check, and step S3 is used to check whether the input data is complete and accurate. In a specific embodiment, the input check items include units, reference coordinate systems, geometric mathematical models, material parameters, etc. Step S3 can further ensure the reliability of the turbofan engine inlet bird strike simulation analysis method.

[0055] Step S4: performing finite element modeling on the air intake duct, including performing finite element meshing on various components of the air intake duct and defining material models of various components of the air intake duct.

[0056] Specifically, the finite element mesh division of each component of the air inlet includes the use of shell units to simulate the panel skin of the air inlet lip, front bulkhead, rear bulkhead, outer wall plate, and inner wall plate, the use of solid units to simulate the honeycomb in the parts, and the use of SPOTWELD spot welding units to simulate the rivets and bolted joints. The material model for defining each component of the air inlet includes: defining the high strain rate parameters and unit failure parameters of the air inlet structural material, using equivalent failure plastic strain to characterize material failure for metal materials, and using maximum tension / compression strain to characterize material failure for composite materials.

[0057] Step S5: Model quality check, including unit type check, mesh quality check, and material model and parameter check, and determine whether the parameters are consistent with the analysis input. If not, return to step S4 to modify the finite element model.

[0058] In some specific embodiments, in step S5, the unit type check items include using 4-node shell elements for shell elements and 8-node hexahedral elements for solid elements. Among them, shell elements refer to: *ELEMENT_SHELL, and solid elements refer to: *ELEMENT_SOLID. Mesh quality check items include: there must be no less than 3 layers of solid elements in the thickness direction of the inner wall plate, the Jacobian determinant of the hexahedral element must be positive; the Jacobian determinant value of the shell element is not less than 0.5. Corresponding SPOTWELD spot welding unit simulations should be established for the rivet and bolt positions. In one embodiment, if the rivet and bolt positions cannot correspond to the SPOTWELD spot welding units one by one, then from a conservative point of view, under the premise that the force transmission path between the various parts of the air intake duct does not change significantly, the number of SPOTWELD spot welding units can be slightly less than the actual number of rivets and bolts, but should not be less than 95% of the actual number. By establishing BEAM units at rivets and bolts and assigning SPOTWELD spot welding unit properties to simulate the tensile-shear composite failure of rivets and bolts, the influence of connector failure on the bird strike resistance performance of the turbofan aircraft engine inlet can be effectively characterized.

[0059] In other embodiments, the element type check may be to use no more than 2% of the 3-node shell elements and no more than 2% of the 6-node prismatic elements.

[0060] Step S6: performing finite element modeling on the bird body, including performing finite element meshing on the bird body and defining a material model for the bird body.

[0061] In a specific embodiment, a smooth particle physics (SPH) simulation is used for the bird body, so that the flow and dispersion process of the bird body when it hits the inlet of a turbofan aircraft engine can be better simulated to avoid grid distortion and calculation interruption. When defining the material model for the bird body, since the bird body presents a flow state during the high-speed impact process, the material model of the bird body uses the uniform fluid mechanics material model, and the state equation uses the Grüneisen state equation.

[0062] In a specific embodiment, the bird body is simplified to a cylinder with a length-to-diameter ratio of 2:1 for simulation. Figure 4 as well as Figure 5 A smoothed particle 100 (SPH) bird body simulation model of a flying bird is shown.

[0063] Optionally, the turbofan engine inlet bird strike simulation analysis method further includes step S7: bird model quality check, including checking whether the number of bird SPH model particles is correct, whether there is repeated definition of the bird, checking whether the shape is a cylinder with an aspect ratio of 2:1, and checking whether the material model, state equation and parameters of the bird are consistent with the analysis input. If any check result is wrong, return to step S6 to modify the finite element model.

[0064] Step S8: Simulation calculation parameter definition, including:

[0065] The definition of contact pairs includes: point-to-surface contact between the bird body and the various parts of the air intake structure, defining the bird body as the slave surface and the air intake structure parts as the master surface; surface-to-surface contact between the various parts of the air intake, with the smaller stiffness as the slave surface and the larger stiffness as the master surface, or the larger speed as the slave surface and the smaller speed as the master surface, or the smaller mesh size as the slave surface and the larger mesh size as the master surface. There should be no initial penetration between the master and slave surfaces before the analysis begins.

[0066] Definition of flight speed: The larger of the sea level design cruising speed in level flight in the aircraft's flight envelope and the design cruising speed at an altitude of 2450m is selected as the bird impact speed.

[0067] Definition of boundary conditions: Establish a partial fan case model, simulate the connecting bolts between the air inlet and the fan case using spot welding units, establish contact pairs at the interface between the air inlet and the fan case, and apply simple support on the fan case side.

[0068] Hourglass energy control parameter definition: The hourglass energy generated during the calculation process is set by the hourglass control keyword. The hourglass energy should not exceed 10% of the total internal energy. Hourglass energy refers to the high-frequency oscillation energy of shell elements and solid elements. This oscillation does not exist in physics but is caused by mathematical calculations.

[0069] Calculation output parameter definition: Define the output of displacement, stress, strain and other calculation results according to the simulation analysis purpose and requirements. And;

[0070] Solution control parameter definition: Specifically, the solution control parameters include: calculation termination time, time step, number of parallel computing CPU cores, calculation accuracy control, and energy dissipation option control. When setting the solution control options, the analysis time and number of solution CPU cores should be reasonably selected according to the calculation needs and solution resources.

[0071] Step S9: Calculate the file generated in the previous step, for example, solve and calculate the file generated in the previous step by a computer.

[0072] Step S10: Post-processing the calculation results. The post-processing mainly outputs the strain of the structure, the displacement time history curve of the key position, and the displacement cloud map, plastic strain cloud map, stress cloud map, structural damage, etc. of the intake duct structure.

[0073] Step S11: Design compliance check: post-processing based on the calculation results of step S10, including: 1) checking whether the damage range of the connecting bolts between the air inlet docking ring and the front mounting flange of the fan casing is less than the circumferential range of 30°. If it is less, the inspection is passed, and if it is greater, the inspection is failed; 2) checking whether the rear bulkhead of the air inlet is penetrated by the bird body. If not, check whether the deformation of the rear bulkhead squeezes the accessories installed in the fan compartment and affects the normal operation of the engine. If there is no penetration and no squeezing, the inspection is passed, otherwise it fails.

[0074] Step S12: Based on the design conformity check items in step S11, the conclusion on whether the bird strike resistance design of the current air inlet structure meets the strength design requirements is given. The judgment principles include: 1) If both design conformity checks are passed, the strength design requirements are met; 2) If any one of the design conformity check items fails, the strength design requirements are not met.

[0075] Step S13: Intake duct structure optimization:

[0076] According to the conclusion of step S12, the current air inlet does not meet the anti-bird strike design requirements, and the air inlet structure optimization design is carried out according to the calculation result of step S10. Steps S4 to S12 are repeated until the air inlet meets the anti-bird strike strength design requirements, and then step S14 is entered.

[0077] Step S14: Generate analysis report:

[0078] Combining the above steps S1 to S13, a bird strike simulation analysis report for the air inlet is compiled.

[0079] According to the turbofan engine inlet bird strike simulation analysis method recorded in one or more of the aforementioned embodiments, it is achieved by interpreting the airworthiness clauses to clarify the anti-bird strike design requirements for the turbofan aircraft engine inlet, and at the same time, a turbofan aircraft engine inlet bird strike simulation analysis workflow is established to standardize the simulation analysis work. Through the turbofan aircraft engine inlet bird strike simulation analysis, the deformation, damage and other information of components during the impact process is obtained to guide the optimization design of the inlet structure. At the same time, by establishing a connection unit model, the force, damage and other information of connecting parts such as rivets and bolts during the impact process can be obtained to guide the optimization design of the inlet structure, so that the parts with excessive deformation or serious damage can be strengthened, and the optimization design of the inlet structure can be achieved to ensure that the weight of the inlet is reduced as much as possible while meeting the anti-bird strike design requirements to improve the engine thrust ratio.

[0080] The simulation analysis results of bird strike on turbofan aircraft engine inlet are as follows: Figure 6 As shown, 4 flying birds turned into fragments and scattered after the impact, indicating that the SPH method can better simulate the flow dispersion during the impact process; 1 lip and 5 front bulkhead were penetrated by the bird body; 2 outer wall panels in the impact area were broken under the impact impact load; 6 rear bulkhead was not penetrated.

[0081] 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 application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0082] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A turbofan engine inlet bird strike simulation analysis method, characterized in that: The steps include: a. Obtaining the design requirements of the air inlet; b. Obtaining the design input of the air inlet; c. Performing finite element modeling on the air intake duct, including performing finite element meshing on each component of the air intake duct and defining material models of each component of the air intake duct; d. Check the established model, including unit type check, mesh quality check, material model and parameter check, and determine whether the parameters are consistent with the analysis input. If not, return to step c to modify the finite element model; e. Perform finite element modeling on the bird body, including finite element meshing of the bird body and defining a material model for the bird body; f. Definition of simulation calculation parameters, including definition of contact pairs, definition of flight speed, definition of boundary conditions, definition of hourglass energy control parameters, definition of calculation output parameters and definition of solution control parameters; wherein, the definition of contact pairs includes: point-to-surface contact is adopted between the bird body and the various parts of the air inlet structure, the bird body is defined as the slave surface, and the parts of the air inlet structure are defined as the master surface; surface-to-surface contact is adopted between the various parts of the air inlet, the one with smaller stiffness is used as the slave surface, and the one with larger stiffness is used as the master surface, or the one with larger speed is used as the slave surface, and the one with smaller speed is used as the master surface, or the one with smaller mesh size is used as the slave surface, and the one with larger mesh size is used as the master surface; g. Calculate the files generated in the previous steps; h. Post-process the calculation results; i. Perform design compliance check based on the post-processing results of step h; j. Based on step i, give a conclusion on whether the current bird strike resistance design of the air inlet structure meets the strength design requirements; k. If the conclusion of step j is that the current air inlet does not meet the design requirements for bird strike resistance, perform the air inlet structure optimization design based on the calculation results of step h, and repeat steps c to j until the air inlet meets the design requirements for bird strike resistance strength.

2. The turbofan engine inlet bird strike simulation analysis method according to claim 1, characterized in that: The design requirements obtained in step a include: The air intake does not become detached from the engine; and The rear bulkhead of the air inlet is not penetrated by the bird body and the deformation of the rear bulkhead cannot squeeze the accessories installed in the fan compartment and affect the normal operation of the engine.

3. The turbofan engine inlet bird strike simulation analysis method according to claim 2, characterized in that: The design requirement for the air inlet to prevent it from falling off the engine is that the damage area of ​​the connecting bolts between the docking ring and the front mounting flange of the fan casing after the air inlet is hit by a bird is not greater than 30° in the circumferential direction.

4. The turbofan engine inlet bird strike simulation analysis method according to claim 1, characterized in that: The design input includes the air inlet geometric model, air inlet material parameters and a bird body model.

5. The turbofan engine inlet bird strike simulation analysis method according to claim 1, characterized in that: After step b, the method further comprises the following steps: Design input checks.

6. The turbofan engine inlet bird strike simulation analysis method according to claim 1, characterized in that: In step c, finite element mesh division is performed on the components of the air inlet duct, including simulating the panel skin in the lip, front bulkhead, rear bulkhead, outer wall plate and inner wall plate of the air inlet duct by using shell units, simulating the honeycomb in the parts by using solid units, and simulating the rivets and bolt connections by using SPOTWELD spot welding units; defining the material model of the components of the air inlet duct includes: defining the high strain rate parameters and unit failure parameters of the air inlet structure material, using equivalent failure plastic strain to characterize material failure for metal materials, and using maximum tension / compression strain to characterize material failure for composite materials.

7. The turbofan engine inlet bird strike simulation analysis method according to claim 1, characterized in that: In step d, the element type check includes whether a 4-node shell element is used for the shell element, and whether an 8-node hexahedral element is used for the solid element.

8. The turbofan engine inlet bird strike simulation analysis method according to claim 1, characterized in that: In step e, the bird body is simulated by smooth particles, the material model of the bird body is the uniform fluid mechanics material model, and the state equation is the Grüneisen state equation.

9. The turbofan engine inlet bird strike simulation analysis method according to claim 1, characterized in that: After step e, the method further comprises the following steps: Bird body model quality inspection.

10. The turbofan engine inlet bird strike simulation analysis method according to claim 1, characterized in that: After step k, the following steps are also included: Summarize steps a to k to prepare an inlet bird strike simulation analysis report.

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