Turbofan engine fan shaft and design method thereof

Abstract

The invention provides a turbofan engine fan shaft and a design method thereof. The design method of the turbofan engine fan shaft comprises the steps that an initial fan shaft model with an initial configuration is obtained; wherein the initial configuration comprises a boundary dimension structure of the fan shaft model; the initial fan shaft model is adopted to conduct static simulation on the whole turbofan engine, so that the load borne by the initial fan shaft model is obtained; performing statics topology optimization according to the initial fan shaft model and the load, and obtaining an optimization result; determining the density requirement of each axial section in the initial fan shaft model according to the optimization result, and determining the cavity size of each section according to the density requirement to obtain an optimized fan shaft configuration; wherein the cavity size of the part with the high density requirement is smaller than that of the part with the low density requirement; optimized fan shaft configurations include an initial configuration and cavity dimensions.

Description

Technical Field

[0001] This invention relates to the field of turbofan engine technology, and more specifically, to a turbofan engine fan shaft and its design method. Background Technology

[0002] Turbofan engine: A gas turbine engine in which the combined reaction thrust of the exhaust gas ejected from the nozzle and the air exhausted by the fan generates thrust. It consists of a compressor, combustion chamber, high-pressure turbine (driving the compressor), low-pressure turbine (driving the fan), and exhaust system. The first three parts are called the "core engine." The usable energy in the exhaust gas flowing out of the core engine is used partly to drive the low-pressure turbine to drive the fan, and partly to accelerate the exhaust gas in the nozzle.

[0003] Currently, turbofan engines are used as aero engines. The turbofan engine fan shaft, as the component connecting the fan rotor and the low-pressure shaft, is bolted to the fan disk at the front end and splined to the low-pressure shaft at the rear end. Since the fan rotor is typically designed as a cantilever structure, the fan shaft needs to withstand significant bending loads. During takeoff, landing, or other transitions, the turbofan engine rotor experiences acceleration / deceleration. Due to air resistance, the rotor speed is out of sync with the low-pressure shaft, resulting in very large torque loads on the fan shaft. As a critical component of the turbofan engine, the fan shaft is usually designed conservatively under the combined bending and torsional forces, leading to a relatively large weight. Furthermore, the fan shaft is a key component in the transmission path of high-energy impact loads under conditions of fan blade shedding and bird strikes, requiring it to withstand sufficiently large transient impact loads. This is also a crucial factor to consider in the design of the fan shaft structure. Therefore, how to reduce the weight of the turbofan engine fan shaft while ensuring its reliability has become a technical problem that needs to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a design method for a turbofan engine fan shaft that can reduce the weight of the turbofan engine fan shaft while ensuring its reliability.

[0005] Another objective of this invention is to provide a turbofan engine fan shaft that can reduce the weight of the turbofan engine fan shaft while ensuring its reliability.

[0006] Embodiments of the present invention can be implemented in the following ways:

[0007] A method for designing a turbofan engine fan shaft, the method comprising:

[0008] Obtain an initial fan shaft model with an initial configuration; wherein, the initial configuration includes the external dimensions and structure of the initial fan shaft model;

[0009] The initial fan shaft model was used to perform static simulation of the entire turbofan engine to obtain the load borne by the initial fan shaft model;

[0010] Static topology optimization was performed based on the initial fan shaft model and the load, and the optimization results were obtained.

[0011] Based on the optimization results, the density requirements of each axial segment in the initial fan shaft model are determined, and the cavity size of each segment is determined based on the density requirements to obtain an optimized fan shaft configuration; wherein, the cavity size of the part with high density requirements is smaller than the cavity size of the part with low density requirements; the optimized fan shaft configuration includes the initial configuration and the cavity size.

[0012] Optionally, the fan shaft configuration further includes the structural dimensions of the filling structure in the cavity; the turbofan engine fan shaft design method further includes: designing the structural dimensions of the filling structure;

[0013] The steps for designing the structural dimensions of the filling structure include: designing the structural dimensions of the filling structure based on the cavity dimensions and the load.

[0014] Optionally, the filling structure includes spiral reinforcing ribs;

[0015] The step of performing static simulation of the entire turbofan engine using the initial fan shaft model to obtain the load borne by the initial fan shaft model includes:

[0016] The initial fan shaft model was used to perform static simulation of the entire turbofan engine under acceleration and deceleration conditions in order to obtain the torsional load borne by the initial fan shaft model.

[0017] The steps for obtaining the structural dimensions of the filling structure based on the cavity dimensions and the load design include:

[0018] The structural dimensions of the helical reinforcing rib are obtained based on the cavity dimensions and the torsional load.

[0019] Optionally, the filling structure includes axial stiffeners;

[0020] The step of performing static simulation of the entire turbofan engine using the initial fan shaft model to obtain the load borne by the initial fan shaft model includes:

[0021] The initial fan shaft model was used to perform static simulation of the entire turbofan engine under normal operating conditions in order to obtain the bending load borne by the initial fan shaft model.

[0022] The steps for obtaining the structural dimensions of the filling structure based on the cavity dimensions and the load design include:

[0023] The structural dimensions of the axial stiffener are obtained based on the cavity dimensions and the bending load.

[0024] Optionally, after obtaining the optimized fan shaft configuration, the turbofan engine fan shaft design method further includes:

[0025] Obtain an optimized fan shaft model with the optimized fan shaft configuration;

[0026] Based on the optimized fan shaft model, the ultimate load impact dynamics simulation of the turbofan engine was performed.

[0027] If the simulation results of the ultimate load impact dynamics of the turbofan engine meet the requirements, the optimized fan shaft configuration is output as the design configuration of the turbofan engine fan shaft; if the simulation results of the ultimate load impact dynamics of the turbofan engine do not meet the requirements, the cavity dimensions of each section are iteratively designed until the simulation results meet the requirements.

[0028] A turbofan engine fan shaft is designed using the aforementioned turbofan engine fan shaft design method.

[0029] A turbofan engine fan shaft includes a shaft body, which is a cylindrical component that is circumferentially closed and has openings at both ends in the axial direction. The shaft body includes a plurality of segments distributed along the axial direction, and at least a portion of the segments has cavities between its inner and outer walls. The size of the cavity in the segment with a high density requirement is larger than the size of the cavity in the segment with a low density requirement.

[0030] Optionally, the turbofan engine fan shaft further includes a helical reinforcing rib disposed in the cavity, the helical reinforcing rib extending helically around the shaft body.

[0031] Optionally, the spiral reinforcing ribs include positive spiral ribs and negative spiral ribs, wherein the spiral direction of the positive spiral ribs is opposite to that of the negative spiral ribs; a plurality of positive spiral ribs and a plurality of negative spiral ribs are arranged in an alternating mesh pattern in the cavity.

[0032] Optionally, the cross-section of the spiral reinforcing rib is square, the square having a length direction and a thickness direction, the spiral reinforcing rib having a first spiral surface and a second spiral surface along the thickness direction, the first spiral surface and the second spiral surface being used to contact the inner wall and outer wall of the shaft body, respectively; the square has a length dimension along the length direction, the length dimension of the spiral reinforcing rib located in the cavity of the section with high density requirement is greater than the length dimension of the spiral reinforcing rib located in the cavity of the section with low density requirement, or the length dimension of the spiral reinforcing rib is the same at all locations.

[0033] Optionally, the turbofan engine fan shaft further includes axial reinforcing ribs disposed in the cavity, the axial reinforcing ribs including a first axial reinforcing rib and a second axial reinforcing rib, the first axial reinforcing rib and the second axial reinforcing rib being disposed opposite each other on the upper and lower sides of the shaft body.

[0034] The beneficial effects of the turbofan engine fan shaft and its design method provided by the embodiments of the present invention include:

[0035] This invention provides a method for designing a turbofan engine fan shaft, comprising: obtaining an initial fan shaft model with an initial configuration; wherein the initial configuration includes the external dimensions and structure of the fan shaft model; performing static simulation of the entire turbofan engine using the initial fan shaft model to obtain the load borne by the initial fan shaft model; performing static topology optimization based on the initial fan shaft model and the load, and obtaining the optimization result; determining the density requirements of each axial segment in the initial fan shaft model based on the optimization result, and determining the cavity size of each segment based on the density requirements to obtain an optimized fan shaft configuration; wherein the cavity size of the part with high density requirements is smaller than the cavity size of the part with low density requirements; the optimized fan shaft configuration includes the initial configuration and the cavity size. This design method performs static topology optimization based on the applied load, and designs the cavity size based on the density requirements of each segment obtained from the optimization result, so that the designed turbofan engine fan shaft can reduce weight through the cavity, while ensuring that the reliability of the turbofan engine fan shaft after the cavity design meets the requirements.

[0036] The embodiments of the present invention also provide a turbofan engine fan shaft, which is designed according to the above-described turbofan engine fan shaft design method. Therefore, it also has the beneficial effect of reducing weight through the cavity, while ensuring that the reliability of the turbofan engine fan shaft after the cavity design meets the requirements.

[0037] Embodiments of the present invention also provide a turbofan engine fan shaft, comprising a shaft body that is circumferentially closed and has openings at both axial ends; the shaft body includes multiple segments distributed along the axial direction, at least a portion of which has a cavity between its inner and outer walls, and the size of the cavity in the segment with a high density requirement is larger than the size of the cavity in the segment with a low density requirement. This turbofan engine fan shaft reduces weight by incorporating cavities. Furthermore, because the size of the cavity in the segment with a high density requirement is larger than the size of the cavity in the segment with a low density requirement, it helps ensure that the reliability of the turbofan engine fan shaft after incorporating cavities meets the requirements. Attached Figure Description

[0038] The above-described features and advantages of the present invention will be better understood after reading the following detailed description of embodiments of the present disclosure in conjunction with the accompanying drawings. In the drawings, components are not necessarily drawn to scale, and components having similar related characteristics or features may have the same or similar reference numerals.

[0039] Figure 1 A partial structural schematic diagram of a turbofan engine according to one aspect of the present invention is shown;

[0040] Figure 2 A cross-sectional structural schematic diagram of the main body of the fan shaft of a turbofan engine according to one aspect of the present invention is shown;

[0041] Figure 3 A schematic diagram of a filling structure in a turbofan engine fan shaft according to an aspect of the present invention is shown.

[0042] Figure 4 A schematic diagram of the structure of a spiral ultra-strong rib provided according to one aspect of the present invention is shown;

[0043] Figure 5 A flowchart of a turbofan engine fan shaft design method according to one aspect of the present invention is shown;

[0044] Figure 6 A schematic diagram of the optimization results of static topology optimization according to one aspect of the present invention is shown.

[0045] Figure label:

[0046] 11-Fan rotor; 12-Bending load; 13-Torsion load; 14-Ultimate load;

[0047] 100-Turbofan engine fan shaft; 110-Shaft body; 111-Inner wall; 112-Outer wall; 113-Cavity; 114-First section; 115-Second section; 116-Third section; 117-Fourth section; 118-Fifth section; 119-Sixth section; 120-Filling structure; 121-Helical reinforcing rib; 122-Positive helical rib; 123-Reverse helical rib; 124-First helical surface; 125-Second helical surface; 126-Axial reinforcing rib; 127-First axial reinforcing rib;

[0048] 200 - Initial fan shaft model; 211 - Part 1; 212 - Part 2; 213 - Part 3; 214 - Part 4; 215 - Part 5; 216 - Part 6. Detailed Implementation

[0049] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should be noted that the aspects described below with reference to the accompanying drawings and specific embodiments are merely exemplary and should not be construed as limiting the scope of protection of the present invention in any way.

[0050] In the description of this invention, it should be noted that if terms such as "upper," "lower," "inner," "outer," or "vertical" appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed when in use, and does not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0051] At the same time, it should be noted that the terms "first" and "second" are used only for distinguishing descriptions and should not be interpreted as indicating or implying relative importance.

[0052] In the description of this invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an integral connection, or a detachable connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or a connection within two components, etc. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0053] The following definitions apply to terms that may appear in the description of this invention:

[0054] Fan shaft: The component in a turbofan engine that connects the fan rotor and the low-pressure shaft. The front end is connected to the fan disc by bolts, and the rear end is connected to the low-pressure shaft by splines. Since the fan rotor is usually designed as a cantilever structure, the fan shaft needs to withstand a large bending load.

[0055] Static optimization: an optimization method that uses static force, static pressure, etc. as load inputs, and usually requires the integration of static simulation software for calculation.

[0056] Topology optimization: a mathematical method for optimizing the distribution of materials within a given region based on given load conditions, constraints, and performance indicators; it is a type of structural optimization.

[0057] Impact dynamics simulation: a method and tool for numerically simulating the dynamic response process of a structure under transient and dynamic loads. This patent proposal is for simulating the dynamic response of a turbofan engine under fan blade loss or bird strike load.

[0058] Figure 1 This diagram shows a partial structural schematic of the turbofan engine provided in this embodiment. Figure 2 This diagram shows a cross-sectional view of the shaft body 110 of the turbofan engine fan shaft 100 provided in this embodiment. Please refer to the diagram for further details. Figure 1 and Figure 2 This embodiment provides a turbofan engine fan shaft 100, which is applied to a turbofan engine to mount the fan rotor 11.

[0059] The turbofan engine fan shaft 100 includes a shaft body 110, which is a cylindrical component that is circumferentially closed and has openings at both axial ends. The shaft body 110 includes multiple segments distributed along the axial direction. At least a portion of the inner wall 111 and outer wall 112 of the multiple segments have cavities 113, and the size of the cavity 113 in the segment with a high density requirement is larger than the size of the cavity 113 in the segment with a low density requirement. By designing the size of the cavity 113 in the segment with a high density requirement to be larger than the size of the cavity 113 in the segment with a low density requirement, the reliability of the turbofan engine fan shaft 100 can be ensured, helping it to withstand sufficiently large transient impact loads, while also maximizing weight reduction.

[0060] Specifically, the shaft body 110 is a single-piece structure, and its multiple segments are divided according to density requirements, resulting in different density requirements between adjacent segments. The density requirements of different segments on the shaft body 110 are obtained based on the results of static topology optimization. After obtaining the density requirements, the size of the cavity 113 at different segments can be set according to the density requirements. The size of the cavity 113 at the segment with a higher density requirement is larger than the size of the cavity 113 at the segment with a lower density requirement. This setting process will be described in the turbofan engine fan shaft design method provided later. In other words, the turbofan engine fan shaft 100 can be regarded as being designed according to the turbofan engine fan shaft design method provided below.

[0061] Furthermore, in this embodiment, the cavities 113 in multiple segments are interconnected. Specifically, in this embodiment, each segment has a cavity 113, which facilitates the manufacture of the shaft body 110 using additive manufacturing. It is understood that in some other embodiments, in order to ensure the reliability of the shaft body 110 or when the shaft body 110 is manufactured by other methods, cavities 113 may be designed only in some segments.

[0062] Figure 3 A schematic diagram of the filling structure 120 in the turbofan engine fan shaft 100 provided in this embodiment is shown. Please refer to... Figures 1-3 In this embodiment, a filling structure 120 is also provided in the cavity 113 of the turbofan engine fan shaft 100. The filling structure 120 improves the reliability of the turbofan engine fan shaft 100, which helps to ensure that the turbofan engine fan shaft 100 has sufficient strength to withstand transient impact loads even when the size of the cavity 113 is further increased.

[0063] Figure 4 A schematic diagram of the spiral ultra-strong rib provided in this embodiment is shown. Please refer to the diagram for further details. Figures 1-4 Optionally, the filling structure 120 includes a helical reinforcing rib 121 disposed in the cavity 113, the helical reinforcing rib 121 extending helically around the shaft body 110. The helical reinforcing rib 121 helps to improve the ability of the turbofan engine fan shaft 100 to withstand torsional loads 13.

[0064] Optionally, the cross-section of the helical reinforcing rib 121 is square, with a length direction and a thickness direction. The square has a thickness dimension 'a' in the thickness direction, which is determined by the radial dimension of the cavity 113. Specifically, the helical reinforcing rib 121 has a first helical surface 124 and a second helical surface 125 along the thickness direction. The first helical surface 124 and the second helical surface 125 are respectively used for contact and engagement with the inner wall 111 and the outer wall 112 of the shaft body 110. Specifically, in this embodiment, the first helical surface 124 contacts and engages with the outer wall 112 of the shaft body 110, and the second helical surface 125 contacts and engages with the inner wall 111 of the shaft body 110.

[0065] The square has a length dimension b in the longitudinal direction, which needs to be designed according to density requirements. Optionally, the length dimension b can be set such that the length dimension b of the spiral reinforcing rib 121 in the cavity 113 of the section with high density requirements is greater than the length dimension b of the spiral reinforcing rib 121 in the cavity 113 of the section with low density requirements. Alternatively, considering manufacturing difficulty, the length dimension b of the spiral reinforcing rib 121 can be set to be the same at all locations. In this case, the selection of the length dimension b of the spiral reinforcing rib 121 needs to take into account the density requirements of each part of the turbofan engine fan shaft 100. For example, the length dimension can be preset according to the density requirements of each section of the turbofan engine fan shaft 100, and then the average value of the multiple preset length dimensions can be calculated and used as the length dimension b of the spiral reinforcing rib 121. Furthermore, the specific value of the length dimension b needs to be set according to the size of the turbofan engine and the spiral axial spacing of the spiral reinforcing rib 121, etc., to ensure that the structural design and strength simulation requirements are met.

[0066] Furthermore, the spiral reinforcing rib 121 includes a positive spiral rib 122 and a negative spiral rib 123, with the spiral direction of the positive spiral rib 122 being opposite to that of the negative spiral rib 123. Multiple positive spiral ribs 122 and multiple negative spiral ribs 123 are arranged in a staggered, mesh-like configuration within the cavity 113. Specifically, the positive spiral ribs 122 extend spirally clockwise around the axial direction of the shaft body 110, while the negative spiral ribs 123 extend spirally counterclockwise around the axial direction of the shaft body 110. Because the spiral directions of the positive spiral ribs 122 and the negative spiral ribs 123 are opposite, therefore... Figure 3 As shown, multiple positive spiral ribs 122 and multiple negative spiral ribs 123 arranged in the cavity 113 are interwoven into a mesh.

[0067] Optionally, the filling structure 120 further includes axial reinforcing ribs 126 disposed in the cavity 113. It should be noted that, in the description of this embodiment, the "axial reinforcing rib 126" refers to a reinforcing rib that does not deflect around the axial direction and is not necessarily parallel to the axial direction. Specifically, in this embodiment, the shaft body 110 has a tapered structure with one axial end larger than the other, therefore the axial reinforcing ribs 126 disposed in the cavity 113 are arranged along... Figure 2 The direction shown from left to right tends to be closer to the axis.

[0068] Optionally, the axial stiffener 126 includes a first axial stiffener 127 and a second axial stiffener, which are disposed opposite to each other on the upper and lower sides of the shaft body 110. It should be noted that... Figure 3Only the first axial stiffener 127 is shown in the diagram. The axial stiffener 126 helps improve the ability of the turbofan engine fan shaft 100 to withstand bending load 12. Since the fan shaft in a turbofan engine often employs a cantilever structure, which causes the fan shaft to primarily bear the bending load 12 from gravity, the axial stiffener 126 is mainly positioned in the direction of gravity of the turbofan engine fan shaft 100. It is understood that in other embodiments, the number and position of the axial stiffener 126 can be set as needed.

[0069] The embodiments of the present invention also provide a design method for a turbofan engine fan shaft, which is used to confirm the design configuration of a turbofan engine fan shaft 100. Accordingly, the embodiments of the present invention also provide a turbofan engine fan shaft 100 designed by the turbofan engine fan shaft design method.

[0070] Figure 5 A flowchart illustrating the turbofan engine fan shaft design method provided in this embodiment is shown. Please refer to the attached diagram. Figures 1-5 The turbofan engine fan shaft design method provided in this embodiment specifically includes the following steps:

[0071] S01: Obtain the initial fan shaft model 200 with the initial configuration.

[0072] The initial configuration includes the external dimensions and structure of the initial fan shaft model 200. This fan shaft model is a cylindrical component that is axially closed and has openings at both ends. Specifically, the initial fan shaft model 200 with this initial configuration can be considered as... Figure 2 The structural model shown is when the shaft body 110 does not have a cavity 113.

[0073] Before obtaining the initial fan shaft model 200 with the initial configuration, the turbofan engine fan shaft design method may also include a step of performing an initial configuration design, which includes: performing an initial configuration design of the fan shaft with fan shaft engineering requirements as input, including: size requirements, weight requirements, installation requirements, economic requirements, etc.

[0074] S02: The initial fan shaft model 200 is used to perform static simulation of the entire turbofan engine in order to obtain the load borne by the initial fan shaft model 200.

[0075] Since the initial fan shaft model 200 is a structure with only an initial configuration and no cavity 113 is set inside, the load borne by the fan shaft during the operation of the entire turbofan engine can be obtained by using this initial fan model to perform static simulation of the entire turbofan engine.

[0076] Specifically, the main loads borne by the fan shaft during the operation of the entire machine include bending load 12, torsional load 13, and ultimate load 14. Among them, bending load 12 is mainly generated by the gravity of the cantilevered fan rotor 11; torsional load 13 is mainly due to the acceleration and deceleration of the turbofan engine rotor during takeoff, landing, or other state transitions. Under the action of air resistance, the rotational speed of the fan rotor 11 is not synchronized with that of the low-pressure shaft (not shown in the figure), thus generating a very large torsional load 13 on the fan shaft; ultimate load 14 is the transient impact load borne by the fan shaft as a key component in the force transmission path of the above-mentioned high-energy impact loads under the action of fan blade shedding and bird strike loads. Therefore, ultimate load 14 can be regarded as the load borne by the fan shaft under unconventional operating conditions.

[0077] Step S02 mainly includes the following processes:

[0078] S21: Static simulation of the entire turbofan engine under normal operating conditions is performed using the initial fan shaft model 200 to obtain the bending load 12 borne by the initial fan shaft model 200.

[0079] It should be noted that, in the description of this embodiment, "normal operating state" refers to the operating state when the turbofan engine is running smoothly and the acceleration has no change or a small change.

[0080] S22: Static simulation of the entire turbofan engine under acceleration and deceleration conditions is performed using the initial fan shaft model 200 to obtain the torsional load 13 borne by the initial fan shaft model 200.

[0081] Therefore, in this embodiment, the load obtained by performing step S02 includes bending load 12 and torsional load 13.

[0082] S03: Static topology optimization is performed based on the initial fan shaft model 200 and the load, and the optimization results are obtained.

[0083] Using bending load 12 and torsional load 13 as inputs, static topology optimization is performed on the initial fan shaft model 200 to obtain the most reasonable density distribution of each part of the fan shaft. Figure 6 The optimization results of the static topology optimization provided in this embodiment are shown, such as... Figure 6 In the optimization results shown, the density of the red material is set to 1, the density of the blue area is set to 0, and the material densities of other colored areas are considered intermediate densities. This embodiment provides a method based on the following... Figure 6The optimization results of the topology optimization shown divide the initial fan shaft model 200 into six parts: part 211, part 212, part 213, part 214, part 215, and part 216. Part 213 has a red area, therefore its density requirement is the highest. Part 216 has a blue area, therefore its density requirement is the lowest. Accordingly, a smaller cavity 113 or even no cavity 113 can be set in part 213, while a larger cavity 113 can be set in part 216, thus resulting in greater weight reduction potential.

[0084] Accordingly, the final designed turbofan engine fan shaft 100 also includes six corresponding segments in its shaft body 110. These six segments are: first segment 114, second segment 115, third segment 116, fourth segment 117, fifth segment 118, and sixth segment 119. The first segment 114 corresponds to the first part 211, the second segment 115 corresponds to the second part 212, the third segment 116 corresponds to the third part 213, the fourth segment 117 corresponds to the fourth part 214, the fifth segment 118 corresponds to the fifth part 215, and the sixth segment 119 corresponds to the sixth part 216. Figure 2 As can be seen, the cavity 113 of the second segment 115, the fourth segment 117 and the sixth segment 119 is larger in size, while the cavity 113 of the first segment 114, the third segment 116 and the fifth segment 118 is smaller in size.

[0085] It needs to be explained, such as Figure 6 As shown in the optimization results, the initial fan model 200 has different density requirements at the same axial position but different circumferential locations, i.e. Figure 6 When designing cavities, the cavity dimensions can be set to be the same at a uniform axial position but different circumferential positions, and the cavity dimensions can be set based on the maximum density requirement at that axial position.

[0086] The initial configuration and cavity 113 dimensions were used as the basis for optimizing the fan shaft configuration, thus realizing the structural design of the shaft body 110.

[0087] To further improve the reliability of the designed turbofan engine fan shaft 100 and reduce its weight, a filling structure 120 can be provided in the cavity 113. Optimizing the fan shaft configuration also includes the structural dimensions of the filling structure 120 filling the cavity 113. Therefore, this turbofan engine fan shaft design method also includes:

[0088] S04: Design the structural dimensions of the infill structure 120.

[0089] The structural dimensions of the filling structure 120 are obtained based on the dimensions of the cavity 113 and the load design.

[0090] In this embodiment, the filling structure 120 includes spiral reinforcing ribs 121. Therefore, the step of designing the structural dimensions of the filling structure 120 based on the dimensions of the cavity 113 and the load includes:

[0091] S41: The structural dimensions of the helical reinforcing rib 121 are obtained based on the dimensions of the cavity 113 and the torsional load 13.

[0092] Specifically, the cross-section of the spiral reinforcing rib 121 is square, and it has a length dimension and a thickness dimension. The thickness dimension is designed according to the size of the cavity 113, and is the size at which the spiral surfaces on both sides fit with the inner wall 111 and the outer wall 112. The length dimension is designed according to the density requirements, the initial configuration and the spiral axial spacing, and the specific value is finally determined through iterative verification based on structural design and strength simulation.

[0093] S42: The structural dimensions of the axial stiffener 126 are obtained based on the dimensions of the cavity 113 and the bending load 12.

[0094] Since the turbofan engine fan shaft 100 may be subjected to an ultimate load 14 during turbofan engine operation, in order to ensure that the designed turbofan engine fan shaft 100 can withstand this ultimate load 14, the turbofan engine fan shaft design method further includes the following steps after optimizing the fan configuration:

[0095] S05: Perform ultimate load simulation test on the fan shaft with optimized fan shaft configuration.

[0096] S51: Obtain the optimized fan shaft model with the optimized fan shaft configuration.

[0097] An impact mechanics simulation model of the fan shaft is established based on the optimized fan shaft configuration, and this model is used as the optimized fan shaft model.

[0098] S52: Based on the optimized fan shaft model, perform impact dynamics simulation of the turbofan engine's overall ultimate load 14.

[0099] Using the load time-mileage at the connection interface between the fan shaft, fan disk, and low-pressure shaft obtained through whole-engine FBO simulation as input, the fan shaft model is optimized to perform impact dynamics simulation of the ultimate load of the turbofan engine.

[0100] If the simulation results of the impact dynamics of the turbofan engine's overall ultimate load 14 meet the requirements, the optimized fan shaft configuration will be output as the design configuration of the turbofan engine's fan shaft 100. If the simulation results of the impact dynamics of the turbofan engine's overall ultimate load 14 do not meet the requirements, the dimensions of the cavities 113 in each section will be iteratively designed until the simulation results meet the requirements.

[0101] Specifically, in this embodiment, the above requirements are engine strength design criteria. Meanwhile, since the optimized fan configuration also includes the structural dimensions of the filling structure 120 within the cavity 113, if the simulation results of the impact dynamics of the turbofan engine's overall ultimate load 14 do not meet the requirements, the dimensions of the cavity 113 and the structural dimensions of the filling structure 120 in each section can be iteratively designed until the simulation results meet the requirements.

[0102] The turbofan engine fan shaft 100 and its design method provided in the embodiments of the present invention effectively reduce weight by setting a cavity 113 within the shaft body 110. Furthermore, compared with traditional fan shaft configurations, the fan shaft configuration designed using the topology optimization method is more in line with the equal stress design concept and makes more rational use of materials. Moreover, the design fully considers the influence of rotor gravity load, acceleration / deceleration torsional load 13, and ultimate load 14 on the fan shaft structure, thus fully meeting the requirements of engine strength design criteria.

[0103] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of designing a fan shaft for a turbofan engine, the method comprising: The turbofan engine fan shaft design method comprises: an initial fan shaft model with an initial configuration is obtained; wherein the initial configuration comprises the outer dimension structure of the initial fan shaft model; statics simulation of the turbofan engine is performed by using the initial fan shaft model to obtain the load borne by the initial fan shaft model; statics topology optimization is performed according to the initial fan shaft model and the load, and an optimization result is obtained; the density requirement of each axial section of the initial fan shaft model is determined according to the optimization result, and the cavity size of each section is determined according to the density requirement to obtain an optimized fan shaft configuration; wherein the cavity size of a section with high density requirement is smaller than the cavity size of a section with low density requirement; the optimized fan shaft configuration comprises the initial configuration and the cavity size.

2. The method of designing a fan shaft for a turbofan engine according to Claim 1, wherein, the fan shaft configuration further comprises the structure size of a filling structure filled in the cavity; the turbofan engine fan shaft design method further comprises: designing the structure size of the filling structure; the step of designing the structure size of the filling structure comprises: designing the structure size of the filling structure according to the cavity size and the load.

3. The method of designing a fan shaft for a turbofan engine according to Claim 2, wherein, the filling structure comprises a helical reinforcing rib; the step of performing the statics simulation of the turbofan engine by using the initial fan shaft model to obtain the load borne by the initial fan shaft model comprises: the statics simulation of the turbofan engine under acceleration and deceleration is performed by using the initial fan shaft model to obtain the torsional load borne by the initial fan shaft model; the step of designing the structure size of the filling structure according to the cavity size and the load comprises: the structure size of the helical reinforcing rib is obtained according to the cavity size and the torsional load.

4. The turbofan engine fan shaft design method according to claim 2, wherein the filling structure comprises an axial reinforcing rib; the step of performing the statics simulation of the turbofan engine by using the initial fan shaft model to obtain the load borne by the initial fan shaft model comprises: the statics simulation of the turbofan engine under normal working condition is performed by using the initial fan shaft model to obtain the bending load borne by the initial fan shaft model; the step of designing the structure size of the filling structure according to the cavity size and the load comprises: the structure size of the axial reinforcing rib is obtained according to the cavity size and the bending load.

5. The turbofan engine fan shaft design method according to claim 1, wherein after the step of obtaining the optimized fan shaft configuration, the turbofan engine fan shaft design method further comprises: an optimized fan shaft model with the optimized fan shaft configuration is obtained; the limit load impact dynamics simulation of the turbofan engine is performed according to the optimized fan shaft model; if the limit load impact dynamics simulation result of the turbofan engine meets the requirement, the optimized fan shaft configuration is output as the design configuration of the turbofan engine fan shaft; if the limit load impact dynamics simulation result of the turbofan engine does not meet the requirement, the cavity size of each section is iteratively designed until the simulation result meets the requirement.

6. A fan shaft of a turbofan engine, characterized in that, the fan shaft of the turbofan engine is designed by the method for designing a fan shaft of a turbofan engine according to any one of claims 1-5.

7. A fan shaft for a turbofan engine, the fan shaft comprising a shaft body, the shaft body being a cylindrical member that is circumferentially closed and has openings at axial ends thereof; characterized in that, the shaft body comprises a plurality of sections distributed along the axial direction, and the inner wall and the outer wall of at least some of the plurality of sections have a cavity therebetween, and the size of the cavity at the section with a large density requirement is larger than the size of the cavity at the section with a small density requirement.

8. The fan shaft of the turbofan engine according to claim 7, characterized in that, the fan shaft of the turbofan engine further comprises helical reinforcing ribs arranged in the cavity, and the helical reinforcing ribs extend helically around the shaft body in the axial direction.

9. The fan shaft of the turbofan engine according to claim 8, characterized in that, the helical reinforcing ribs comprise positive helical ribs and negative helical ribs, the helical direction of the positive helical ribs is opposite to the helical direction of the negative helical ribs; and a plurality of the positive helical ribs and a plurality of the negative helical ribs are arranged in a meshed manner in the cavity.

10. The fan shaft of the turbofan engine according to claim 8, characterized in that, the cross section of the helical reinforcing rib is square, the square has a length direction and a thickness direction, the helical reinforcing rib has a first helical surface and a second helical surface along the thickness direction, and the first helical surface and the second helical surface are respectively used to contact the inner wall and the outer wall of the shaft body; the square has a length dimension along the length direction, the length dimension of the helical reinforcing rib in the cavity at the section with a large density requirement is larger than the length dimension of the helical reinforcing rib in the cavity at the section with a small density requirement, or the length dimension of the helical reinforcing rib is the same everywhere.

11. The fan shaft of the turbofan engine according to claim 7, characterized in that, the fan shaft of the turbofan engine further comprises axial reinforcing ribs arranged in the cavity, and the axial reinforcing ribs comprise first axial reinforcing ribs and second axial reinforcing ribs, and the first axial reinforcing ribs and the second axial reinforcing ribs are arranged on the upper and lower sides of the shaft body.

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