A variable wall thickness turbine rear bearing frame structure

Abstract

The present application belongs to the field of aero-engine rear casing design, and is a variable-wall-thickness turbine rear load-bearing frame structure. In order to improve the structural bearing capacity, meet the strength requirements and reduce the weight as much as possible, the outer ring adopts a circumferential variable-wall-thickness design. The circumference of the first arc plate 5 should be greater than 180° to simultaneously increase the radial and lateral stiffness of the rear casing; the transition zone is generally designed to be between two support plates. Under the same load conditions, the more support plates there are, the smaller the circumferential arc length range of the AD arc segment; the wall thickness of the AD arc segment is generally not greater than 2.5 times the wall thickness of the BC arc segment; the setting of the AB and CD segments buffers the stress of the first arc plate and the second arc plate to prevent sudden stress changes from affecting the stiffness of the outer ring 1; the reduction in the thickness of the second arc plate reduces the structural weight while optimizing the force transmission path structure and improving the structural bearing capacity and radial stiffness.

Description

Technical Field

[0001] The present application belongs to the field of aircraft engine rear casing design, and particularly relates to a variable wall thickness turbine rear bearing frame structure. Background Art

[0002] The turbine rear bearing casing is the main load-bearing structural component at the rear of the engine. It is responsible for bearing the load and rectifying the airflow at the turbine outlet. Its main characteristics are complex geometric structure and high thermal load.

[0003] The turbine rear casing frame typically consists of an inner ring, an outer ring, and a number of support plates, and is manufactured using either integral casting or welding. The turbine gas flow path passes between the inner and outer rings, where the high-temperature gas flow generates significant thermal stress and deformation. While bearing the heavy loads of the engine rotor, these components must also meet the requirements for thermal deformation coordination and rigidity. Any localized thermal deformation inconsistency can affect the concentricity of the support points, causing vibration. In severe cases, cracks can form in the frame, severely impacting engine safety.

[0004] The turbine rear bearing frame structure is mainly divided into four types according to the differences in the support plate and outer ring structure: cylindrical straight support plate, cylindrical oblique support plate, polygonal straight support plate and polygonal oblique support plate, such as Figure 1 、 Figure 2 As shown in Figure 2, the inclined support plate structure can adjust for the relative thermal expansion difference of the turbine casing. The support plate inclination is usually determined based on thermal compatibility requirements. Given the same geometric radius and number of support plates, the polygonal casing frame is more rigid than the cylindrical rear casing.

[0005] Existing technical solutions all utilize a single profile, uniform cross-section design for the outer ring of the turbine rear support frame. The turbine rear support frame's structural form is constrained not only by the overall engine structure but also by its own weight. However, the turbine rear casing structure and load-bearing conditions are highly complex, and its structural design is closely tied to the weight and reliability of the rear casing components.

[0006] In addition to the thermal load caused by the incoordination of the connection due to temperature differences, when the engine auxiliary mounting section or main mounting section is set at a local position of the outer ring, it will also bear part of the inertia force in the lateral or vertical direction of the engine.

[0007] Therefore, how to improve the structural load-bearing capacity and rigidity while reducing the weight as much as possible is a difficult point in the design of the turbine rear load-bearing frame structure. Summary of the Invention

[0008] The purpose of this application is to provide a variable wall thickness turbine rear bearing frame structure to solve the problem in the prior art that it is difficult to simultaneously ensure weight reduction and structural bearing capacity and stiffness requirements for the turbine rear casing.

[0009] The technical solution of the present application is: a variable wall thickness turbine rear load-bearing frame structure, including an outer ring, a support plate and an inner ring, the outer ring includes a first arc plate, a second arc plate and a third arc plate, the first arc plate, the second arc plate and the third arc plate form a closed annular structure, the thickness of the first arc plate is greater than the thickness of the second arc plate, there are two groups of the third arc plate and they are respectively arranged between the two end portions of the first arc plate and the second arc plate, and the thickness of the third arc plate is between the thickness of the first arc plate and the second arc plate.

[0010] Preferably, the thickness of the third arc plate gradually decreases from the end of the first arc plate to the end of the second arc plate.

[0011] Preferably, a plurality of groups of arc-shaped inner grooves are arranged at intervals on the first arc plate, and lifting ears are integrally connected to the arc-shaped inner grooves.

[0012] Preferably, the cross-section of the arc-shaped inner groove includes a contraction section, a straight section and an expansion section, the contraction section is located at the front end of the casing, the straight section is arranged between the contraction section and the expansion section, the radial height of the contraction section gradually decreases from the side of the contraction section close to the outer ring end to the straight section, the radial height of the expansion section gradually decreases from the straight section to the side of the expansion section close to the outer ring end, and the radial highest point of the contraction section is smaller than the radial highest point of the expansion section.

[0013] Preferably, the axial cross-section of the arc-shaped inner groove is arc-shaped and concave, and the axial cross-section of the arc-shaped inner groove is symmetrically arranged from the middle.

[0014] The present application discloses a variable-wall-thickness turbine rear load-bearing frame structure. In order to improve the structural bearing capacity, meet the strength requirements while minimizing the weight, the outer ring adopts a circumferentially variable wall thickness design. The circumference of the first arc plate 5 should be greater than 180° to simultaneously increase the radial and lateral stiffness of the rear casing; the transition zone is generally designed to be located between two support plates. Under the same load conditions, the more support plates there are, the smaller the circumferential arc length range of the AD arc segment; the wall thickness of the AD arc segment is generally not greater than 2.5 times the wall thickness of the BC arc segment; the setting of the AB and CD segments buffers the stresses of the first arc plate and the second arc plate to prevent sudden stress changes from affecting the stiffness of the outer ring 1; the reduction in the thickness of the second arc plate reduces the structural weight while optimizing the force transmission path structure and improving the structural bearing capacity and radial stiffness. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions provided by this application, the following is a brief introduction to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of this application.

[0016] Figure 1 Schematic diagram of the structure of two cylindrical support plates in the background technology;

[0017] Figure 2Schematic diagram of the structure of two polygonal support plates in the background technology;

[0018] Figure 3 This is a schematic diagram of the overall structure of this application;

[0019] Figure 4 A schematic diagram highlighting the third arc plate structure for this application;

[0020] Figure 5 This is a schematic diagram of the structure of the lifting lug and the arc-shaped inner groove of this application;

[0021] Figure 6 This is a schematic diagram of the cross-sectional profile of the arc-shaped inner groove of the present application;

[0022] Figure 7 This is a schematic diagram of the axial cross-sectional profile of the arc-shaped inner groove of the present application at different nodes from front to back;

[0023] Figure 8 This is a schematic diagram of an axial cross-section of the arc-shaped inner groove of this application.

[0024] 1. Outer ring; 2. Support plate; 3. Inner ring; 4. Lifting lug; 5. First arc plate; 6. Second arc plate; 7. Third arc plate. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the implementation of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below in conjunction with the drawings in the embodiments of this application.

[0026] A variable wall thickness turbine rear bearing frame structure, such as Figure 3 、 Figure 4 As shown, it includes an outer ring 1, support plates 2 and an inner ring 3. The outer ring 1 and the inner ring 3 are coaxially arranged. There are multiple groups of support plates 2 and they are spaced between the inner ring 3 and the outer ring 1 along the circumferential direction of the inner and outer rings 1.

[0027] At different positions of the turbine rear bearing casing, on the one hand, the influence of high-temperature combustion gas at different circumferential positions is different, and the temperature conditions inside the turbine rear bearing casing are also very different at different radial positions; on the other hand, due to the different structures connected at different circumferential positions, the external loads received are also different. If the outer ring 1 is designed to be a circular ring with equal thickness, the wall thickness must be designed according to the limit load position, which not only greatly increases the weight of the rear casing, but also makes it difficult to coordinate the relative thermal expansion of each position due to the stronger rigidity, and is also prone to fatigue cracks, requiring a reasonable structural stiffness design.

[0028] In order to solve this problem, the specific design includes: the outer ring 1 includes a first arc plate 5, a second arc plate 6 and a third arc plate 7, the first arc plate 5, the second arc plate 6 and the third arc plate 7 form a closed ring structure, the thickness of the first arc plate 5 is greater than the thickness of the second arc plate 6, there are two groups of third arc plates 7 and they are respectively arranged between the two end portions of the first arc plate 5 and the second arc plate 6, and the thickness of the third arc plate 7 is between the thickness of the first arc plate 5 and the second arc plate 6.

[0029] Mark the endpoints of the first arc plate 5, the second arc plate 6 and the third arc plate 7 as points A, B, C and D respectively. The first arc plate 5 is between AD, the second arc plate 6 is between BC, and the two sections of the third arc plate 7 are between AB and CD. The thickness H2 of the AD section is greater than the thickness of the AB and CD sections and greater than the thickness H1 of the BC section.

[0030] In addition to bearing temperature loads, aerodynamic loads and loads transmitted by bearing supports, the turbine rear casing is also subjected to large maneuvering loads, such as vertical maneuvering loads and horizontal maneuvering loads, because the outer ring 1 is connected to the main mounting section at the lug 4.

[0031] In order to improve the structural bearing capacity, meet the strength requirements and reduce the weight as much as possible, the outer ring 1 adopts a circumferential variable wall thickness design, such as Figure 3 As shown, the first arc plate 5 should extend circumferentially greater than 180° to increase both the radial and lateral stiffness of the rear receiver. The transition zone is typically located between two support plates. Under the same load conditions, the greater the number of support plates 2, the smaller the circumferential arc length of the AD segment. The wall thickness of the AD segment is generally no more than 2.5 times that of the BC segment.

[0032] The arrangement of the AB and CD segments buffers the stress of the first arc plate 5 and the second arc plate 6 , thereby preventing sudden stress changes from affecting the rigidity of the outer ring 1 .

[0033] The reduction in thickness of the second arc plate reduces the weight of the structure while still meeting the strength and stiffness requirements, thereby improving the structural load-bearing efficiency.

[0034] Preferably, the thickness of the third arc plate 7 gradually decreases from the end of the first arc plate 5 to the end of the second arc plate 6. In this way, the stress between the first arc plate 5 and the second arc plate 6 changes slowly, so that the stiffness change of the entire outer ring 1 during operation is within a small range.

[0035] As the thrust-to-weight ratio requirements of engines continue to increase, the restrictions on component weight and structural space are becoming increasingly strict. This puts forward stricter requirements on the position of the lifting lug 4, requiring the outer ring 1 and the lifting lug 4 to adopt a more compact structural design, as follows:

[0036] like Figure 4 、 Figure 5As shown, preferably, multiple groups of arc-shaped inner grooves are provided at intervals on the first arc plate 5, and the arc-shaped inner grooves are integrally connected to the lifting lugs 4. By partially embedding the lifting lugs 4 into the arc-shaped inner grooves, a sunken structure is formed. In this way, the portion of the lifting lugs 4 exposed from the outer ring 1 is significantly reduced, the space occupied by the turbine rear bearing casing is reduced, the structure is compact, and the space occupied by the outer ring 1 is effectively met.

[0037] The outer ring plate at the four lifting lug positions features a locally sunken structure formed by extending the axially variable cross-section profile, avoiding sudden changes in structural stiffness. The circular casing is more susceptible to bending under radial loads from the equally spaced support plates. Compared to a circular outer ring structure, this effectively reduces local bending stress and provides a tolerance for thermal deformation, resulting in a compact structure and reduced overall size and weight.

[0038] like Figure 6 As shown, preferably, the cross-section of the arc-shaped inner groove includes a contraction section, a straight section and an expansion section. The contraction section is located at the front end of the casing, and the straight section is provided between the contraction section and the expansion section. The radial height of the contraction section gradually decreases from the side of the contraction section close to the end of the outer ring 1 to the straight section, and the radial height of the expansion section gradually decreases from the straight section to the side of the expansion section close to the end of the outer ring 1, and the radial highest point of the contraction section is smaller than the radial highest point of the expansion section.

[0039] After reaching the turbine rear support casing, the high-temperature exhaust gas first passes through the contraction section to slightly compress the airflow. The compressed airflow is maintained in the straight section for a period of time, and then is ejected through the expansion section. Through this design, some key parameters in the airflow field will not change significantly, thereby achieving the technical effect of reducing the external space occupied by the turbine rear support casing while maintaining the stability of the flow field inside the casing.

[0040] like Figure 7 、 Figure 8 As shown, preferably, for the design of the specific profile of the arc-shaped inner groove along the circumferential direction of the casing, 10 nodes (1-10) are selected from front to back for the cross section of the arc-shaped inner groove, and the axial cross section of the arc-shaped inner groove at each node is arc-shaped and concave, and the axial cross section of the arc-shaped inner groove is symmetrically arranged from the middle, forming an S-shaped structure on both sides of the symmetry. The specific parameters are determined by comprehensively considering the installation space and aerodynamic requirements. By designing the concave symmetrical structure, the continuity and stability of the airflow channel can be ensured.

[0041] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A variable wall thickness turbine rear bearing frame structure, comprising an outer ring (1), a support plate (2) and an inner ring (3), characterized in that: The outer ring (1) comprises a first arc plate (5), a second arc plate (6) and a third arc plate (7); the first arc plate (5), the second arc plate (6) and the third arc plate (7) form a closed annular structure; the thickness of the first arc plate (5) is greater than the thickness of the second arc plate (6); there are two groups of the third arc plates (7) which are respectively arranged between the two end portions of the first arc plate (5) and the second arc plate (6); the thickness of the third arc plates (7) is between the thickness of the first arc plate (5) and the second arc plate (6); The first arc plate (5) is provided with a plurality of groups of arc-shaped inner grooves at intervals, and the arc-shaped inner grooves are integrally connected with hanging ears (4); The cross section of the arc-shaped inner groove includes a contraction section, a straight section and an expansion section, the contraction section is located at the front end of the casing, the straight section is located between the contraction section and the expansion section, the radial height of the contraction section gradually decreases from the side of the contraction section close to the end of the outer ring (1) to the straight section, the radial height of the expansion section gradually decreases from the straight section to the side of the expansion section close to the end of the outer ring (1), and the radial highest point of the contraction section is smaller than the radial highest point of the expansion section.

2. The variable wall thickness turbine rear bearing frame structure according to claim 1, characterized in that: The thickness of the third arc plate (7) gradually decreases from the end of the first arc plate (5) to the end of the second arc plate (6).

3. The variable wall thickness turbine rear bearing frame structure according to claim 1, characterized in that: The axial cross section of the arc-shaped inner groove is arc-shaped and concave, and the axial cross section of the arc-shaped inner groove is symmetrically arranged from the middle.

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