Method of designing a rear pressure frame

Abstract

The application relates to the technical field of aircrafts, and particularly discloses a design method of a rear pressure frame, which comprises the following steps: firstly, determining the fuselage contour; then, determining the top frame high point A and the bottom frame high point B according to the minimum rigidity requirement of the rear pressure frame; then, determining the left side frame high point C and the right side frame high point D through the perpendicular line method; then, fitting the top frame high point A, the bottom frame high point B, the left side frame high point C and the right side frame high point D into a smooth circular or elliptical frame inner edge contour; then, forming a bottom circle contour according to the parallel offset of the frame inner edge contour or redesigning a regular bottom circle contour at the second station plane of the rear pressure; then, designing a spherical skin structure with a regular and smooth spherical surface shape or ellipsoidal shape according to the bottom circle contour as a reference; and finally, designing Y-shaped pieces and an intermediate frame, and connecting the intermediate frame and the rear fuselage wall plate through longitudinal connecting pieces. The above method can make the spherical skin structure have a regular shape, improve the quality of the spherical skin structure shape, and reduce the manufacturing difficulty of the spherical skin structure.

Description

Technical Field

[0001] This invention relates to the field of aircraft technology, and more particularly to a design method for a rear pressure frame. Background Technology

[0002] The aft pressure frame structure is a fully enclosed, airtight frame that functions as the airtight end frame of the fuselage's passenger and cargo compartments. It is a crucial fatigue-resistant load-bearing component of the fuselage, primarily maintaining the fuselage's cross-sectional shape and participating in load transfer. It also serves as the docking frame between the mid-fuselage and the aft fuselage, representing the process separation surface between them. The aft pressure frame structure mainly includes a spherical skin, Y-shaped components, and an intermediate frame. The spherical skin structure is connected in two main ways: internal spherical skin connection and external spherical skin connection.

[0003] When the rear pressure frame structure adopts the spherical skin external connection scheme, the Y-shaped part has two hyperboloids, which makes it difficult to manufacture. Due to the fuselage contour, it is difficult to fit the spherical skin into a regular and smooth curved surface, which affects the design, weight and manufacturing quality of the spherical skin structure. Moreover, when the middle and rear fuselage are connected to the rear fuselage, the assembly space between the Y-shaped part and the rear fuselage is narrow, which affects the assembly efficiency and quality.

[0004] When the rear pressure frame structure adopts the spherical inner connection scheme, there are two hyperboloids in the Y-shaped part, which makes manufacturing more difficult; the frame design is difficult, the frame weight is large, and the manufacturing is difficult; in order to balance the yaw component of the airtight load of the rear pressure frame structure, more longitudinal stiffeners are needed to connect the inner edge of the frame and the web, which leads to an increase in weight.

[0005] Therefore, it is urgent to study the design method of the rear pressure frame, improve the surface quality of the spherical skin structure, and reduce the manufacturing difficulty of the spherical skin structure. Summary of the Invention

[0006] The purpose of this invention is to provide a design method for the rear pressure frame to improve the surface quality of the spherical skin structure and reduce the manufacturing difficulty of the spherical skin structure.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention provides a design method for a rear pressure frame, which includes the following steps:

[0009] S01. By intersecting the first station plane of the rear pressure frame with the theoretical shape of the fuselage, the station fuselage outline of the rear pressure frame is obtained.

[0010] S02. Based on the stiffness requirements of the rear pressure frame, determine the minimum frame height H of the rear pressure frame. In the first station plane of the rear pressure frame, determine the top frame height point A and the bottom frame height point B. The distance between the top frame height point A and the top point A1 of the station fuselage outline is H1, and the distance between the bottom frame height point B and the bottom point B1 of the station fuselage outline is H2. H1≥H, H2≥H.

[0011] S03. Connect the top frame height point A and the bottom frame height point B to form a vertical line segment L1. Draw a horizontal straight line L2 through the midpoint of line segment L1. The straight line L2 intersects the outline of the station body to form the left point C1 and the right point D1. Determine the left frame height point C and the right frame height point D in the first station plane of the rear pressure frame. The distance between the left frame height point A and the left point C1 is H3, and the distance between the right frame height point D and the right point D1 is H4. H3≥H, H4≥H, H4=H3;

[0012] S04. Based on the top frame height point A, bottom frame height point B, left frame height point C, and right frame height point D, fit a smooth circular or elliptical inner edge contour.

[0013] S05. In the first station plane of the rear pressure frame, based on the design requirements of structure and strength, the inner edge contour of the offset frame is parallel to form a bottom circle contour; or a regular bottom circle contour is redesigned in the second station plane of the rear pressure frame, with the first station plane and the second station plane being coplanar or parallel.

[0014] S06. Based on the design requirements of structure and strength, design a regular and smooth spherical or ellipsoidal spherical skin structure with the bottom circle outline as the reference.

[0015] S07, Design the Y-shaped component and the middle frame;

[0016] S08. Design longitudinal connectors to connect the middle frame and the middle and rear fuselage panels.

[0017] As a preferred embodiment, in S04, check that all frame heights within the first station plane of the pressure frame are ≥H. If the requirements are not met, adjust the positions of the top frame height point A, bottom frame height point B, left frame height point C, and right frame height point D to meet the requirements, and refit the inner edge contour of the frame.

[0018] Preferably, in S05, the inner edge profile of the frame is refitted by parallel offset or the closed profile is refitted to form a bottom circle profile.

[0019] Preferably, in S07, the Y-shaped component includes a first annular plate and a hyperbolic panel disposed on one side of the first annular plate, the shape of which is designed according to the spherical skin structure.

[0020] Preferably, in S07, the intermediate frame includes a second annular plate and a first support plate and a second support plate disposed at both ends of the second annular plate, the outline of the first support plate being designed according to the outline of the mid-rear fuselage wall panel.

[0021] As a preferred option, in S07, a ring-shaped reinforcing rib is designed for the middle frame.

[0022] Preferably, the projection of the annular reinforcing rib on the second annular plate is parallel to or coincides with the projection of the bottom circle contour on the second annular plate.

[0023] Preferably, in S08, the longitudinal connector is located between the first support plate and the annular reinforcing rib, or the longitudinal connector is located between the first support plate and the second support plate.

[0024] As a preferred embodiment, in S07, several longitudinal reinforcing ribs are designed for the middle frame, and these longitudinal reinforcing ribs are spaced apart between the first support plate and the second support plate.

[0025] Preferably, the middle frame is made of the same material as the middle and rear fuselage panels.

[0026] The beneficial effects of this invention are as follows:

[0027] This invention provides a design method for a rear pressure frame. This method involves first determining the fuselage outline, then determining the top frame height point A and the bottom frame height point B based on the stiffness requirements of the rear pressure frame. Next, the left frame height point C and the right frame height point D are determined using the perpendicular line method. Based on these three points, a smooth circular or elliptical inner edge contour is fitted. A regular bottom circle contour is then redesigned based on the parallel offset inner edge contour or on the second rear pressure frame station plane. Using this bottom circle contour as a reference, a regular and smooth spherical or ellipsoidal spherical skin structure is designed. Finally, a Y-shaped component, an intermediate frame, and longitudinal connecting components are designed to connect the intermediate frame and the mid-rear fuselage panel. This method, on the one hand, ensures a regular shape for the spherical skin structure, improving the surface quality of the spherical skin structure and reducing its manufacturing difficulty; on the other hand, the regular shape of the spherical skin structure also ensures a regular shape for the Y-shaped component, reducing its manufacturing difficulty. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating the design method of the rear pressure frame in an embodiment of the present invention;

[0029] Figure 2 This is a structural diagram illustrating the determination of the top frame height, bottom frame height, left frame height, and right frame height in the design method of the rear pressure frame in an embodiment of the present invention.

[0030] Figure 3This is a schematic diagram of the structure for determining the inner edge contour of the frame in the design method of the rear pressure frame in an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of the structure for determining the bottom circle profile in the design method of the rear pressure frame in an embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of the structure of the rear pressure frame assembly in an embodiment of the present invention, with the longitudinal connecting member located between the first support plate and the annular reinforcing rib;

[0033] Figure 6 This is a schematic diagram of the structure of the rear pressure frame assembly in an embodiment of the present invention, with the longitudinal connecting member located between the first support plate and the second support plate.

[0034] In the picture:

[0035] 100. Spherical skin structure; 200. Rear fuselage panel; 300. Connecting ring; 400. Mid-rear fuselage panel;

[0036] 1. Standout fuselage outline;

[0037] 2. The inner edge outline of the frame;

[0038] 3. Bottom circle outline;

[0039] 4. Y-shaped component; 41. First annular plate; 42. Hyperbolic panel;

[0040] 5. Middle frame; 51. Second annular plate; 52. First support plate; 53. Second support plate; 54. Annular reinforcing rib; 55. Longitudinal reinforcing rib;

[0041] 6. Longitudinal connecting parts. Detailed Implementation

[0042] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do 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. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions. Furthermore, "above," "on top of," and "over" the first feature in relation to the second feature includes the first feature directly above and diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "under," and "below" the first feature in relation to the second feature includes the first feature directly below and diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0044] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0045] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0046] like Figure 1-6 As shown, this embodiment provides a design method for a rear pressure frame, which includes:

[0047] Step 1: Using the intersection of the first station plane of the aft pressure frame and the theoretical shape of the fuselage at that location, the fuselage outline 1 of the station of the aft pressure frame is obtained, as shown in the attached figure. Figure 2 As shown, the first station plane can be the mating surface of the first annular plate 41 and the second annular plate 51.

[0048] Step 2: Based on the minimum stiffness requirement of the rear pressure frame, determine the minimum frame height H of the rear pressure frame. Within the first station plane of the rear pressure frame, determine the top frame height point A and the bottom frame height point B. The distance between the top frame height point A and the top point A1 of the station fuselage outline 1 is H1, and the distance between the bottom frame height point B and the bottom point B1 of the station fuselage outline 1 is H2, where H1 ≥ H and H2 ≥ H. (See attached diagram) Figure 2 As shown, line segment AB is collinear with line segment A1B1. The top frame height point A and the bottom frame height point B are determined within the outline 1 of the station body. Preferably, H can be 150mm.

[0049] Step 3: Connect the top frame height point A and the bottom frame height point B to form a vertical line segment L1. Draw a horizontal line L2 through the midpoint of line segment L1. Line L2 intersects the fuselage outline 1 at the station location to form left point C1 and right point D1. Determine the left frame height point C and right frame height point D within the first station plane of the rear pressure frame. The distance between left frame height point A and left point C1 is H3, and the distance between right frame height point D and right point D1 is H4, where H3 ≥ H, H4 ≥ H, and H4 = H3. (See attached diagram) Figure 2 As shown; line segment CD is collinear with line segment C1D1. Within the fuselage outline 1 at the station location, determine the left frame height point C and the right frame height point D.

[0050] Step 4: Based on the top frame height point A, bottom frame height point B, left frame height point C, and right frame height point D, fit a smooth circular or elliptical inner edge contour 2, as shown in the attached figure. Figure 3 As shown.

[0051] Step 5: Within the first station plane of the rear pressure frame, based on structural and strength design requirements, parallel offset inner edge contour 2 is used to form a bottom circular contour 3; or a regular bottom circular contour 3 is redesigned within the second station plane of the rear pressure frame, with the first and second station planes coplanar or parallel. This bottom circular contour 3 is smooth (circular or elliptical) and symmetrical from left to right, as shown in the attached figure. Figure 4 As shown. When forming the bottom circular contour 3, design requirements for assembly and maintenance must also be met. The second station plane and the first station plane can be coplanar or parallel. When they are parallel, the second station plane can be the side of the second annular plate 51 away from the first annular plate 41. The method for redesigning the bottom circular contour 3 within the second station plane is the same as the method for designing the inner edge contour 2 of the frame, the difference being the specific numerical values.

[0052] Step Six: Based on the structural and strength design requirements, design a regular and smooth spherical or ellipsoidal skin structure 100 using the bottom circular contour 3 as a reference. It should be noted that the spherical skin structure 100 can be designed based on the bottom circular contour 3; the specific design method is well known to those skilled in the art and will not be elaborated upon here.

[0053] Step 7: Design Y-shaped component 4 and middle frame 5.

[0054] Step 8: Design the longitudinal connecting piece 6 to connect the intermediate frame 5 and the middle and rear fuselage wall panel 400.

[0055] The above method can make the spherical skin structure 100 a regular shape, improve the surface quality of the spherical skin structure 100, and reduce the manufacturing difficulty of the spherical skin structure 100. On the other hand, since the spherical skin structure 100 is a regular shape, the shape of the Y-shaped part 4 is also a regular shape, which reduces the manufacturing difficulty of the Y-shaped part 4.

[0056] Furthermore, in step four, it is checked that all frame heights within the first station plane of the rear pressure frame are ≥H. If the requirement is not met, the positions of the top frame height point A, bottom frame height point B, left frame height point C, and right frame height point D are adjusted to meet the requirements, and the inner edge contour 2 of the frame is refitted. The above method ensures that the position of the inner edge of the pressure frame will not result in a frame height less than H at some locations due to fitting issues, thus ensuring the strength of the final rear pressure frame.

[0057] In step five, the inner edge contour 2 of the frame is refitted with parallel offset, or the closed contour is refitted to form the bottom circle contour 3. In this step, it is necessary to avoid interference with other components such as cables passing through the Y-shaped component 4, according to the coordination requirements of each system.

[0058] In step seven, the Y-shaped component 4 includes a first annular plate 41 and a hyperboloidal panel 42 disposed on one side of the first annular plate 41. The shape of the hyperboloidal panel 42 is designed according to the spherical skin structure 100. The above method ensures that the Y-shaped component 4 has only one hyperboloidal surface structure, reducing the design and manufacturing difficulty of the Y-shaped component 4 and reducing the production cost of the equipment.

[0059] In addition, in step seven, the intermediate frame 5 includes a second annular plate 51 and a first support plate 52 and a second support plate 53 disposed at both ends of the second annular plate 51. The outline of the first support plate 52 is designed according to the outline of the mid-rear fuselage panel 400. This method simplifies the design process of the first support plate 52 and helps improve the design efficiency of the intermediate frame 5. Preferably, the second support plate 53 is parallel to the first support plate 52; in other words, the second support plate 53 can be formed by offsetting the first support plate 52 inward.

[0060] To increase the strength of the intermediate frame 5, in step seven, an annular reinforcing rib 54 is designed for the intermediate frame 5. The projection of the annular reinforcing rib 54 on the second annular plate 51 is parallel to or coincides with the projection of the bottom circular contour 3 on the second annular plate 51. In the above design method, the shape of the annular reinforcing rib 54 is the same as the shape of the bottom circular contour 3. In particular, when the projection of the annular reinforcing rib 54 on the second annular plate 51 coincides with the projection of the bottom circular contour 3 on the second annular plate 51, the force of the spherical skin structure 100 can be better transmitted.

[0061] In step seven, a number of longitudinal reinforcing ribs 55 are designed for the intermediate frame 5, and these longitudinal reinforcing ribs 55 are spaced apart between the first support plate 52 and the second support plate 53. The design of the longitudinal reinforcing ribs 55 can further increase the strength of the intermediate frame 5.

[0062] Regarding the position of the longitudinal connector 6, in this embodiment, it can be designed as follows: in step eight, the longitudinal connector 6 is located between the first support plate 52 and the annular reinforcing rib 54, or between the first support plate 52 and the second support plate 53. Both of these design methods have advantages. Positioning the longitudinal connector 6 between the first support plate 52 and the second annular plate 51 can minimize the size of the longitudinal connector 6, thereby reducing its weight. In this embodiment, optionally, the lower edge of the longitudinal connector 6 has a downward flange, and the downward flange of the longitudinal connector 6 is fixed to the rear fuselage wall panel 400 by bolts. The longitudinal connector 6 is located between the first support plate 52 and the second support plate 53, which can increase the strength of the intermediate frame 5 as much as possible based on the existing size of the intermediate frame 5. In this embodiment, optionally, the lower edge of the longitudinal connector 6 is provided with a downward flange and a side flange is provided on the side near the second annular plate 51. The downward flange is fixed to the middle and rear fuselage wall panel 400 by bolts and the downward flange is fixed to the second annular plate 51 by bolts.

[0063] Preferably, the first annular plate 41 and the second annular plate 51 are fixedly connected by bolts. This installation method provides a larger installation space for the Y-shaped component 4, effectively improving the assembly efficiency of the Y-shaped component 4.

[0064] Preferably, the intermediate frame 5 and the mid-rear fuselage panel 400 are made of the same material. Further, the first support plate 52 extends across the gap between the mid-rear fuselage panel 400 and the rear fuselage panel 200, and the intermediate frame 5, mid-rear fuselage panel 400, and rear fuselage panel 200 are made of the same material. Preferably, the intermediate frame 5, mid-rear fuselage panel 400, and rear fuselage panel 200 are all made of metal or composite materials. This design of identical materials ensures that the thermal expansion of the materials of the mid-rear fuselage panel 400, rear fuselage panel 200, and intermediate frame 5 is the same, resulting in synchronous changes. This avoids shear stress on the bolts between the first annular plate 41 and the second annular plate 51 due to inconsistent changes between the two materials.

[0065] To connect the mid-rear fuselage panel 400 and the rear fuselage panel 200, optionally, after step eight, a connecting ring 300 is designed for connecting the mid-rear fuselage panel 400 and the rear fuselage panel 200. The mid-rear fuselage panel 400 and the rear fuselage panel 200 are fixedly connected by bolts.

[0066] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A design method for a rear pressure frame, characterized in that, Includes the following steps: S01. By intersecting the first station plane of the rear pressure frame with the theoretical shape of the fuselage, the station fuselage outline of the rear pressure frame is obtained (1); S02. Based on the stiffness requirements of the rear pressure frame, determine the minimum frame height H of the rear pressure frame. In the first station plane of the rear pressure frame, determine the top frame height point A and the bottom frame height point B. The distance between the top frame height point A and the top point A1 of the station body outline (1) is H1, and the distance between the bottom frame height point B and the bottom point B1 of the station body outline (1) is H2. H1≥H, H2≥H; S03. Connect the top frame high point A and the bottom frame high point B to form a vertical line segment L1. Draw a horizontal straight line L2 through the midpoint of line segment L1. The straight line L2 intersects with the body outline (1) of the station to form the left point C1 and the right point D1. Determine the left frame high point C and the right frame high point D in the first station plane of the rear pressure frame. The distance between the left frame high point A and the left point C1 is H3, and the distance between the right frame high point D and the right point D1 is H4. H3≥H, H4≥H, H4=H3; S04. Based on the top frame height point A, bottom frame height point B, left frame height point C and right frame height point D, fit a smooth circular or elliptical inner edge contour (2). S05. In the first station plane of the rear pressure frame, based on the design requirements of structure and strength, the inner edge contour (2) of the offset frame is parallel to form the bottom circle contour (3); or the regular bottom circle contour (3) is redesigned in the second station plane of the rear pressure frame, and the first station plane and the second station plane are coplanar or parallel. S06. Based on the design requirements of structure and strength, a regular and smooth spherical or ellipsoidal spherical skin structure (100) is designed with the bottom circle contour (3) as the reference. S07, Design the Y-shaped component (4) and the middle frame (5); S08. Design longitudinal connecting piece (6) to connect the intermediate frame (5) and the middle and rear fuselage wall panel (400).

2. The design method of the rear pressure frame according to claim 1, characterized in that, In S04, check all frame heights ≥ H in the first station plane of the pressure frame. If the requirements are not met, adjust the positions of the top frame height point A, bottom frame height point B, left frame height point C and right frame height point D to meet the requirements, and refit the inner edge contour of the frame (2).

3. The design method of the rear pressure frame according to claim 2, characterized in that, In S05, the inner edge profile of the box is refitted by parallel offset (2) or the closed profile is refitted to form the bottom circle profile (3).

4. The design method of the rear pressure frame according to claim 1, characterized in that, In S07, the Y-shaped component (4) includes a first annular plate (41) and a hyperbolic panel (42) disposed on one side of the first annular plate (41), the shape of which is designed according to the spherical skin structure (100).

5. The design method of the rear pressure frame according to claim 1, characterized in that, In S07, the middle frame (5) includes a second annular plate (51) and a first support plate (52) and a second support plate (53) located at both ends of the second annular plate (51). The outline of the first support plate (52) is designed according to the outline of the middle and rear fuselage wall panel (400).

6. The design method of the rear pressure frame according to claim 5, characterized in that, In S07, a ring-shaped reinforcing rib (54) is designed for the middle frame (5).

7. The design method of the rear pressure frame according to claim 6, characterized in that, The projection of the annular reinforcing rib (54) on the second annular plate (51) is parallel or coincident with the projection of the bottom circle contour (3) on the second annular plate (51).

8. The design method of the rear pressure frame according to claim 6, characterized in that, In S08, the longitudinal connector (6) is located between the first support plate (52) and the annular reinforcing rib (54) or between the first support plate (52) and the second support plate (53).

9. The design method of the rear pressure frame according to claim 5, characterized in that, In S07, several longitudinal reinforcing ribs (55) are designed for the middle frame (5), and the several longitudinal reinforcing ribs (55) are spaced apart between the first support plate (52) and the second support plate (53).

10. The design method of the rear pressure frame according to claim 1, characterized in that, The middle frame (5) is made of the same material as the middle and rear fuselage panel (400).

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