A turboprop aircraft engine fairing lip and a flexible integral forming method thereof

Abstract

A turboprop aircraft engine fairing lip and a flexible integral forming method thereof. The fairing lip is an integrally formed metal sheet metal shell structure, provided with three independent air inlets, the inner side walls of the three air inlets being independent of each other, and the outer side walls of the three air inlets being connected and integrated. The flexible integral forming method comprises constructing multiple process models, and gradually forming the unfolded sheet material into a finished fairing lip according to the process models.

Description

Technical Field

[0001] The present application relates to a sheet metal plastic forming technology in the field of aircraft manufacturing, specifically a method for integrally forming a turboprop aircraft engine fairing lip and a multi-pass regional gradient flexible forming method thereof. Background Art

[0002] The lip of an aircraft engine is a critical component that interfaces with the nacelle to achieve aerodynamic functions and ensure proper engine operation under ultra-high frequency, ultra-high intensity, and alternating hot and cold loads. From an aerodynamic perspective, the more streamlined the lip, the less drag and turbulence the aircraft experiences, the less destructive forces acting on the lip, and the longer its service life. From a functional perspective, the lip must be lightweight, tough, heat-resistant, and have good thermal conductivity. Currently, sheet metal forming of turboprop engine lip lip is not yet feasible internationally. Potential technologies include composites and 3D printing, but neither has been installed in an aircraft. This is because composites have poor thermal conductivity and cannot meet the requirements for heat dissipation and de-icing, while 3D-printed products have a cast structure and cannot meet the long-term high-frequency, high-intensity, and seismic toughness requirements of operating environments. Sheet metal, with its high density and toughness, has been widely used for thousands of years, from the era of cold weapons to modern aviation, aerospace, and automotive fields. Therefore, as a key component in aircraft aerodynamics, sheet metal processing of lip lip lip remains internationally recognized as the most reliable technology. The use of sheet metal plastic processing of an integral, streamlined rectifier lip not only reduces the structure but also significantly improves aerodynamic efficiency and service life.

[0003] It's well known that the purpose of a spar lip is to protect the proper functioning of the engine's internal fuel lines, precision control systems, and other components. However, due to the internal structure of a turboprop engine, the spar lip's structural shape differs fundamentally from that of a turbofan engine. The aerodynamic design and overall manufacturing feasibility have always been major challenges restricting flight performance and service life. Currently, most turboprop engine lip designs internationally consist of two or three independent, three-dimensional, annular air inlets of varying sizes and heights, forming a multi-step shell structure. Key drawbacks include: First, the transition area between the independent air inlets suffers from poor streamlines, with gaps perpendicular to the heading and even large turbulence planes. This results in both power loss and flight-impairing turbulence at high speeds. Second, the sharp edges and corners of the transition area between the independent air inlets hinder overall formation, necessitating multi-stage machining, resulting in poor precision after assembly onto the engine. Third, the welding and riveting process can lead to deformation, weight gain, and compromised aesthetics and structural strength. In addition, to address the shortcomings of existing split-body lip fairings, such as poor assembly accuracy due to segmented manufacturing, domestic patent publications CN110434216A, CN110899501A, and CN114160700A, among others, disclose methods for integrally forming engine lips. These existing technologies are only focused on integrally forming single inlet fairing lips with a structure approximating a circular ring and a relatively simple deformation principle. For turboprop engine fairing lips with complex shapes, a split riveted and welded composite structure has long been necessary, and achieving integral forming has long been an extremely difficult problem in the international plastic forming field. Summary of the Invention

[0004] In order to overcome the poor streamline of the existing turboprop engine fairing lip structure, the overall forming faces the two extreme contradictions of dead wrinkles and cracks due to its overly complex shape, which affects aerodynamic efficiency and restricts overall forming and service performance. One purpose of this application is to provide a turboprop engine fairing lip with a streamlined appearance; the second purpose of this application is to provide a method for the overall flexible forming of a turboprop engine fairing lip.

[0005] A turboprop aircraft engine fairing lip, characterized in that: the turboprop aircraft engine fairing lip is an integrally formed metal sheet metal shell structure, on which three independent air inlets are provided, the first air inlet is located in the upper part of the shell structure and is an approximately circular fairing shell, the second air inlet is located in the middle part of the shell structure and is an approximately square fairing shell, and the third air inlet is located in the lower part of the shell structure and is an approximately elliptical fairing shell, each air inlet includes an inner wall and an outer wall, the inner wall and the outer wall are connected at the top to form a parabola shape, the inner walls of the three air inlets are independent of each other, and the outer walls of the three air inlets are connected to form a whole.

[0006] Furthermore, the height and width of the outer side wall of the second air inlet of the turboprop aircraft engine fairing lip are both smaller than the height and width of the first air inlet and the third air inlet, and the outer side wall of the second air inlet connects the outer side walls of the first air inlet and the third air inlet through an inverted saddle curved surface streamline.

[0007] The method for integrally forming the turboprop aircraft engine fairing lip is based on a known design model of the fairing lip, which is characterized by comprising the following steps and contents:

[0008] 1) Based on the design digital model of the rectifying lip, a first process model is constructed. The first process model includes a basin and a first flange. The sidewall of the basin includes the inner sidewall of the first air inlet. The bottom of the basin is a process-supplemented circular bottom surface. The first flange is coplanar with the top surface of the first air inlet, and its contour matches the planar unfolded contour of the outer sidewall of the rectifying lip.

[0009] 2) Based on the design digital model of the rectifying lip and the first process model, a second process model is constructed. In the second process model, the first flange edge on the outer side of the basin of the first process model is formed into the outer side wall of the first air inlet and the first transition shape and second flange edge of the second and third air inlets. The first transition shape is a raised shell-like body. The edge of the first transition shape matches the edge of the outer side wall of the second and third air inlets. The height of the first transition shape is less than the corresponding height of the outer side wall of the second and third air inlets. The second flange edge surrounds the outer side wall of the first air inlet and the edge of the first transition shape.

[0010] 3) constructing a third process model based on the design digital model of the rectifying lip and the second process model. In the third process model, the first transitional profiles of the second and third air inlets are formed into second transitional profiles of the second and third air inlets, and the second flange edge of the second process model is formed into a third flange edge. The outer wall of the second transitional profile includes the outer walls of the second and third air inlets, and the third flange edge surrounds the outer wall edge of the rectifying lip.

[0011] 4) Constructing a fourth process model based on the design digital model of the rectifying lip and the third process model. The fourth process model includes a first annular groove and a second annular groove corresponding to the second and third air inlets. The outer wall of the first annular groove matches the inner wall of the second air inlet, and the top of the inner wall of the first annular groove forms a first supplementary surface. The outer wall of the second annular groove matches the inner wall of the third air inlet, and the top of the inner wall of the second annular groove forms a second supplementary surface.

[0012] 5) Passively filling and deep drawing the unfolded sheet material according to the first process model to form a basin cavity and a first flange edge corresponding to the first air inlet of the rectifying lip, thereby forming a first semi-finished product matching the first process model;

[0013] 6) performing passive liquid-filling deep drawing on the first semi-finished product according to the second process model to form the outer wall of the first air inlet, the second flange edge, and the first transitional shapes of the second air inlet and the third air inlet, thereby forming a second semi-finished product matching the second process model;

[0014] 7) Actively liquid-filling and deep-drawing the second semi-finished product according to the third process model so that the first transitional shape at its lower portion expands and forms into a second transitional shape, and the outer wall of the second transitional shape includes the outer wall profiles of the second and third air inlets, thereby forming a third semi-finished product matching the third process model;

[0015] 8) forming the third semi-finished rubber product according to the fourth process model, partially forming the second transition profiles of the second air inlet and the third air inlet, forming first and second annular ribs on the second transition profile corresponding to the positions of the first and second annular grooves, respectively, to form a fourth semi-finished product, wherein the depths of the first and second annular ribs of the fourth semi-finished product are respectively less than the heights of the first and second annular grooves;

[0016] 9) After cutting and removing the bottom of the pelvic cavity corresponding to the first air inlet, the bottom of the first annular rib corresponding to the second air inlet, and the bottom of the second annular rib corresponding to the third air inlet in the fourth semi-finished product, the fourth semi-finished product is rubber-formed according to the fourth process model of the rectifying lip to complete the complete forming of the inner and outer walls of the first air inlet, the second air inlet, and the third air inlet, thereby forming a rectifying lip finished product that matches the fourth process model.

[0017] Furthermore, in step 1), the projected edge spacing between the first flange edge of the first process model and the outer wall of the rectifying lip on the first flange edge is a streamline variable width structure, and the projected edge spacing is widest on both sides of the minimum cross-section of the saddle surface.

[0018] Furthermore, in step 2), the second flange edge contour of the second process model is generally smaller than the first flange edge contour of the first process model. The second flange edge is a streamlined variable width structure, and its width is narrowest in the outer wall area of the first air inlet and widest on both sides of the minimum cross-section of the saddle surface of the second air inlet.

[0019] Furthermore, the third flange edge of the third process model described in step 3) is in the same height plane as the second flange edge of the second process model, and the third flange edge is also a streamlined variable width structure. The third flange edge matches the contour of the second flange edge of the second process model in the minimum cross-sectional area of the saddle curve from the first air inlet to the second air inlet. The third flange edge is narrowest in the outer wall area of the third air inlet and widest on both sides of the minimum cross-sectional area of the saddle curve of the second air inlet.

[0020] Furthermore, the width of the first annular groove and the second annular groove of the fourth process model in step 4) is 15-20 times the thickness of the sheet to be formed, and the height difference from the first supplementary surface of the first annular groove and the second supplementary surface of the second annular groove to the top surface of the first annular groove and the second annular groove is 0.10-0.15 times the width of the inner side wall of the second air inlet and the third air inlet respectively.

[0021] Furthermore, in step 5), the passive liquid filling and deep drawing deformation of the first semi-finished product is divided into two stages. In the first stage, the unfolded sheet is pre-expanded upward so that the first process model supplements the circular bottom surface to form a shallow spherical bulge. In the second stage, the spherical bulge is flattened and the liquid pressure is continuously increased as the depth of the pelvic cavity increases until the pelvic cavity of the first semi-finished product is completely formed.

[0022] Furthermore, in step 6), the passive liquid filling deep drawing of the second semi-finished product is divided into three stages. In the first stage, the liquid pressure on the lower surface of the first semi-finished product is increased as the forming depth increases, and suction wrinkles and bulges are formed on both sides of the saddle surface of the second air inlet; in the second stage, the liquid pressure on the lower surface of the first semi-finished product is reduced as the forming depth increases, so that the suction wrinkles and bulges on both sides of the saddle surface of the second air inlet gradually disappear, and beneficial wrinkles are formed on the top surface of the second air inlet; in the third stage, rigid mold closing automatically eliminates the beneficial wrinkles.

[0023] Furthermore, the active liquid filling and deep drawing of the third semi-finished product in step 7) is carried out in two steps. First, pre-bulging is performed to pre-expand the first transition shape at its lower part along the length direction of the third air inlet, and a material storage bulge is formed in the third air inlet after the pre-expansion; and then final bulging is performed to expand the first transition shape along the depth direction of the third air inlet after the pre-expansion, and the first transition shape surfaces on both sides of the third air inlet first produce suspended deformation, and then gradually complete the mold sticking as the liquid increases.

[0024] Furthermore, in step 7), the soft solid mixture is filled on the lower surface of the first transition shape of the third air inlet of the second semi-finished product during pre-bulging, and the soft solid mixture is cleaned on the lower surface of the first transition shape after pre-bulging during final bulging.

[0025] Furthermore, the solid mixture used in step 7) has the characteristics of being compressible in volume, agglomerated under high pressure, dispersible under force in a natural state, and recyclable.

[0026] Furthermore, before the fourth semi-finished rubber is preformed in step 8), the first annular groove of the second air inlet, the second annular groove of the third air inlet, the first supplementary surface of the first annular groove, and the second supplementary surface of the second annular groove are lubricated with oil.

[0027] Beneficial effects

[0028] 1) The fairing lip of the present application adopts a saddle-shaped curved surface with both ends connected to the outer wall, so that the overall appearance of the fairing lip is smooth, without a vertical heading spoiler plane, and it is easy to achieve direct streamline connection between the fairing lip and the engine nacelle skin. The airflow acts on the fairing lip to produce diversion, which can not only reduce flight resistance, but also reduce the damage of ultra-high-speed airflow to the fairing lip. At the same time, the airflow can provide sufficient air for the engine through the air intake for combustion or internal cooling, thereby improving the engine fuel efficiency.

[0029] 2) This application addresses the problem of dead wrinkles and cracks coexisting in the rectifier due to the existence of different forming depths, sudden changes in cross-section, and complex shapes. A flexible zone-by-zone gradual process solution is adopted. By distributing the deformation amount over multiple passes and fully thinning the non-effective mold surface, it is beneficial to reduce the deformation damage of the effective mold surface and improve the service life.

[0030] 3) The first semi-finished product of the present application adopts a method combining pre-expansion and passive liquid filling deep drawing, and uses the process to supplement the circular bottom to fully thin the storage material, which is beneficial to reduce the flange flow to maintain the deformation process, and avoid the flange from breaking due to excessive resistance in the ultra-wide area, thereby improving the forming limit of the first semi-finished product and the quality of the flange edge.

[0031] 4) The second semi-finished product of the present application adopts a method combining passive liquid filling with traditional rigid deep drawing and clamping, which is beneficial for transferring the top surface material of the saddle curve to both sides through reverse expansion during the liquid pressure boosting stage, while achieving the purpose of suppressing wrinkling on the top surface and alleviating cracks on both sides, and is also beneficial for maximizing the transition shape of the second semi-finished product after forming, and reducing the risk of excessive deformation of the transition shape when the third semi-finished product is actively filled with liquid.

[0032] 5) The third semi-finished product of the present application is actively filled with liquid to control the deformation direction and mold-sticking order through continuous bidirectional support, which greatly increases the area of the last mold-sticking area participating in the deformation. It can avoid the rupture of the two sides of the outer wall of the third air inlet due to the increase in friction caused by the increase in liquid pressure when the film is first stuck in the large suspended area, and can also avoid wrinkling in the middle and both sides of the formed saddle surface.

[0033] 6) When the fourth semi-finished rubber of the present application is formed, the material is pre-deformed by double-tension stress, which can promote the full thinning of the first supplementary surface and the second supplementary surface in the middle, and achieve a large pre-forming amount, which is beneficial to reduce the thinning amount of the inner wall edge of the second air inlet and the third air inlet.

[0034] Therefore, the multi-pass flexible integral forming method adopted in this application can not only break through the material forming limit of traditional methods, but also produce complex integral rectifying lips with more uniform wall thickness and low fatigue damage.

[0035] The present application is further described in detail below with reference to the accompanying drawings: BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1This is a schematic diagram of the rectifying lip structure of this application.

[0037] Figure 2 This is a schematic diagram of the first process model structure of the rectifying lip of this application.

[0038] Figure 3 This is a schematic diagram of the second process model structure of the rectifying lip of this application.

[0039] Figure 4 This is a schematic diagram of the third process model structure of the rectifying lip of this application.

[0040] Figure 5 This is a schematic diagram of the fourth process model structure of the rectifying lip of this application.

[0041] Figure 6 This is a schematic diagram of the principle of the forming process of the first semi-finished product of the rectifying lip of this application.

[0042] Figure 7 This is a schematic diagram of the principle of the forming process of the second semi-finished saddle surface of the rectifying lip of this application.

[0043] Figure 8 This is a schematic diagram of the pre-bulging principle of the second transition shape of the third semi-finished product of the rectifying lip of this application.

[0044] Figure 9 This is a schematic diagram of the final bulging principle of the second transition shape of the third semi-finished product of the rectifying lip of this application.

[0045] Figure 10 This is a schematic diagram of the principle of local forming of the fourth semi-finished rubber product of the rectifying lip of this application.

[0046] Figure 11 This is a schematic diagram of the complete forming principle of the inner and outer walls of the rectifying lip of the present application.

[0047] Explanation of numbers in the figure: 1. Rectification lip, 2. First air inlet, 3. Second air inlet, 4. Third air inlet, 5. Inner wall, 6. Outer wall, 7. Saddle surface, 8. First process model, 9. Pelvic cavity, 10. First flange edge, 11. Circular bottom surface, 12. Second process model, 13. First transition shape, 14. Second flange edge, 15. Third process model, 16. Second transition shape, 17. Third flange edge, 18. Fourth process model, 19. First annular groove, 20. Second annular groove, 21. First supplementary surface, 22. Second supplementary surface, 23. Projected edge, 24. Minimum cross section, 25. First semi-finished product, 26. Second semi-finished product, 27. Third semi-finished product, 28. Fourth semi-finished product, 29. First annular rib, 30. Second annular rib, 31. Spherical bulge, 32. Suction bulge, 33. Beneficial wrinkling, 34. Solid mixture, 35. Storage bulge. DETAILED DESCRIPTION

[0048] First, the rectifying lip structure of the present application and its aerodynamic characteristics advantages are introduced.

[0049] Refer to the attached Figure 1 The turboprop aircraft engine fairing lip 1 of the present application is an integrally formed metal sheet metal shell structure, on which three independent air inlets are provided. The first air inlet 2 is located at the upper portion of the shell structure and is an approximately circular fairing shell. The second air inlet 3 is located in the middle portion of the shell structure and is an approximately square fairing shell. The third air inlet 4 is located at the lower portion of the shell structure and is an approximately elliptical fairing shell. Each air inlet comprises an inner sidewall 5 and an outer sidewall 6. The inner sidewall and the outer sidewall are connected at the top in a parabolic shape. The inner sidewalls 5 of the three air inlets are independent of each other, while the outer sidewalls 6 of the three air inlets are connected and integrated. It should be emphasized that the height and width of the second air inlet 3 of the turboprop aircraft engine fairing lip are both smaller than the height and width of the first air inlet 2 and the third air inlet 4. The outer sidewalls 6 of the first and third air inlets are connected by a streamlined inverted saddle surface 7 at both ends of the second air inlet. The following three aspects of this lip structure require explanation: First, during operation, airflow is split through the parabolic inner and outer walls 5 and 6 of the lip 1. Part of the airflow enters the engine to provide the necessary air for combustion and cooling, significantly reducing flight turbulence and headwind drag while improving the engine's fuel efficiency. Second, in terms of plastic forming processability, the more streamlined the lip 1, the more conducive it is to improving the manufacturability of the integral forming process. This reduces the assembly difficulty associated with complex multi-segment surfaces and avoids structural strength defects at the joints of split lip 1, significantly improving service life. Third, the integral forming of the lip 1 not only avoids the poor assembly precision and welding and riveting deformation problems of traditional split structures, but also facilitates direct streamlined connection between the lip 1 and the irregular figure-eight nacelle skin during assembly, improving the overall assembly precision of the engine's aerodynamic zone. Therefore, compared with traditional split turboprop engine lips, the lip 1 of this application offers significant advantages, including reduced flight drag, high fuel efficiency, simple assembly, and extended service life.

[0050] Secondly, the process method for achieving integral forming of the rectifying lip of the present application is introduced.

[0051] Refer to the attached Figure 1 To the attached Figure 11 According to the design model of the rectifier lip, the main steps and contents of its overall forming are as follows:

[0052] Step 1) Refer to the attached Figure 1 , Attachment Figure 2Based on the design digital model of the rectifier lip 1, a first process model 8 is constructed. The first process model 8 contains a basin 9 and a first flange 10. The sidewalls of the basin 9 include the inner wall 5 of the first air inlet 2, and the bottom of the basin is a process-supplemented circular bottom surface 11. The first flange 10 is at the same height plane as the top surface of the first air inlet 2, and its contour matches the planar unfolded contour of the outer wall 6 of the rectifier lip. Two points need to be explained: First, the basin height of the first process model 8 is slightly greater than the height of the inner wall 5 of the first air inlet. The main purpose of increasing the height is to construct a supplementary fillet to meet the forming requirements. Second, the distance between the edge of the first flange 10 of the first process model 8 and the projected edge 23 of the outer wall 6 of the rectifier lip on the first flange is a streamlined variable width structure. The distance between the projected edges 23 is widest on both sides of the minimum cross-section 24 of the saddle surface. The reason for increasing the flange size here is that this area will be subjected to greater shear stress during the subsequent forming process. The purpose is to improve the flange's shear load resistance during subsequent forming.

[0053] Step 2) Refer to the attached Figure 2 , Attachment Figure 3 , according to the design digital model of the rectifying lip 1 and the first process model 8, a second process model 12 is constructed. The second process model 12 forms the first flange edge 10 on the outside of the basin of the first process model 8 into the outer wall 6 of the first air inlet 2 and the first transition shape 13 and the second flange edge 14 of the second air inlet 3 and the third air inlet 4. The first transition shape 13 is a raised shell-shaped body. The edge of the first transition shape 13 matches the edge of the outer wall 6 of the second air inlet 3 and the third air inlet 4. The height of the first transition shape 13 is less than the height of the corresponding outer wall 6 of the second air inlet 2 and the third air inlet 4. The second flange edge 14 surrounds the outer wall 6 of the first air inlet and the edge of the first transition shape 13. Two points need to be explained: First, the height of the outer wall 6 of the first air inlet of the second process model is slightly greater than the height of the outer wall 6 of the first air inlet of the rectifying lip; the main purpose of increasing the height is also to construct a supplementary fillet to meet the forming requirements. Second, the outline of the second flange edge 14 of the second process model 12 is generally smaller than the outline of the first flange edge 10 of the first process model 8, and the second flange edge 14 is a streamlined variable width structure; its width is narrowest in the outer wall 6 area of the first air inlet and widest on both sides of the minimum cross-section 24 of the saddle surface of the second air inlet. The reason is that this area is subjected to shear stress during the forming process according to the second process model 12 and the subsequent forming process, and the purpose is also to improve the shear load resistance of the subsequent formed flange.

[0054] Step 3) Refer to the attached Figure 3 , Attachment Figure 4, based on the design digital model of the rectifying lip 1 and the second process model 12, a third process model 15 is constructed. The third process model 15 forms the first transition shape 13 of the second air inlet 3 and the third air inlet 4 into the second transition shape 16 of the second air inlet 3 and the third air inlet 4, and forms the second flange 14 of the second process model 12 into the third flange 17. The outer wall 6 of the second transition shape includes the outer wall 6 of the second air inlet and the third air inlet; the third flange 17 is wrapped around the edge of the outer wall 6 of the rectifying lip. Two points need to be explained: the third flange 17 and the second flange 14 of the second process model are in the same height plane, and the third flange is also a streamlined variable width structure; this is because when forming according to the third process model 15, only the first transition shape 13 needs to be partially expanded to form the second transition shape 16. Therefore, the contours of the third flange 17 and the second flange 14 remain almost unchanged in the minimum cross-section 24 area of the saddle surface from the first air inlet to the second air inlet. Second, the third flange edge 17 is narrowest in the outer wall 6 area of the third air inlet 4 and widest on both sides of the minimum cross-section 24 of the saddle surface of the second air inlet; reducing the flange of the outer wall 6 of the third air inlet is to reduce the flow resistance and reduce the thinning of the second transition profile 16; and increasing the flanges on both sides of the minimum cross-section 24 of the saddle surface is to improve the subsequent deformation shear load resistance.

[0055] Step 4) Refer to the attached Figure 4 , Attachment Figure 5 Based on the design digital model of the rectifying lip 1 and the third process model 15, a fourth process model 18 is constructed. The fourth process model contains a first annular groove 19 and a second annular groove 20 corresponding to the second air inlet 3 and the third air inlet 4. The outer wall of the first annular groove 19 matches the inner wall of the second air inlet 3, and the top of the inner wall of the first annular groove forms a first supplementary surface 21. The outer wall of the second annular groove 20 matches the inner wall of the third air inlet 4, and the top of the inner wall of the second annular groove forms a second supplementary surface 22. Two points need to be explained: First, the width of the first annular groove 19 and the second annular groove 20 of the fourth process model is 15-20 times the thickness of the sheet to be formed. The height difference between the first supplementary surface 21 and the second supplementary surface 22 and the top surface of the first annular groove and the second annular groove is 0.10-0.15 times the width of the inner wall of the second air inlet 3 and the third air inlet 4 respectively; the purpose is to increase the process supplementary surface and reduce the thickness when forming the rubber, but to avoid excessive deformation and cracking. The second is to retain the state of the supplementary surface for forming, and the material is subjected to double tension, and the thinning limit is much higher than that of single tension. This measure can utilize the non-effective surface to fully thin and maintain the deformation process, so that the deformation and thinning of the inner wall of the second air inlet 3 and the third air inlet 4 after forming are significantly reduced, thereby improving the service life of the weak area after deformation.

[0056] Step 5) Refer to the attached Figure 2 , Attachment Figure 6According to the first process model 8, the expanded sheet material is passively filled with liquid and deep-drawn to form the basin cavity 9 and the first flange edge 10 corresponding to the first air inlet 2 of the rectifier lip, forming a first semi-finished product 25 that matches the first process model 8. Two points need to be explained: First, the passive filling and deep-drawing of the first semi-finished product 25 is divided into two stages. Figure 6 In the left side, the first stage is to pre-bulge the expanded sheet upwards so that the first process model 8 supplements the circular bottom surface 11 to form a shallow spherical bulge 31. Figure 6 In the middle right side, in the second stage, after the spherical bulge is flattened, the liquid pressure continues to increase as the depth of the pelvic cavity 9 increases until the pelvic cavity of the first semi-finished product 25 is fully formed. Secondly, it is important to emphasize that the purpose of pre-bulging is to increase the thinning of the central area of the circular bottom surface 11, making full use of the thinning of the non-effective surface for material storage; transferring and replenishing the material of the circular bottom surface 11 to the inner side wall 5, both reducing the thinning of the wider area of the first flange 10 and improving the surface quality and thickness uniformity of the first flange 10.

[0057] Step 6) Refer to the attached Figure 3 , Attachment Figure 7 According to the second process model 12, the first semi-finished product 25 is subjected to passive liquid filling deep drawing to form the outer wall 6 of the first air inlet, the second flange edge 14, and the first transition shape 13 of the second air inlet and the third air inlet, forming a second semi-finished product 26 that matches the second process model. It should be emphasized that the passive liquid filling deep drawing deformation of the second semi-finished product 26 is divided into three stages. Figure 7 In the left side, in the first stage, the liquid pressure on the lower surface of the first semi-finished product 25 increases with the increasing forming depth, forming a suction bulge 32 on both sides of the saddle surface 7 of the second air inlet. Figure 7 In the right side, in the second stage, as the forming depth increases, the liquid pressure on the lower surface of the first semi-finished product 25 is reduced, so that the wrinkles 32 on both sides of the saddle surface of the second air inlet gradually disappear, and beneficial wrinkles 33 are formed on the top surface of the second air inlet. Figure 7On the right side, the beneficial wrinkles 33 are automatically eliminated after the third stage of rigid mold closing. The following three points need to be explained: First, the shape of the first transition shape 13 has a great influence on the overall forming processability. If the first transition shape 13 is too small, the second transition shape 16 of the formed third semi-finished product 27 is easy to break; and if the first transition shape 13 is too large, it will face the contradictory problem of wrinkling in the middle of the second air inlet 3 and breaking on both sides of the third air inlet 4. Second, during the liquid pressure increase stage, the two sides of the saddle surface 7 of the second air inlet are deformed in the air like a balloon, forming suction wrinkles 32, the purpose of which is to prevent serious wrinkling of the saddle surface; and the pressure reduction stage is actually closer to traditional rigid deep drawing, the purpose of which is to prevent rupture due to excessive reverse expansion pressure. Therefore, after the liquid pressure is reduced, the suction wrinkles 32 on both sides of the saddle surface 7 of the second air inlet will gradually disappear, and beneficial wrinkles 33 will be formed on the top surface of the second air inlet. Third, in order to solve the problem of the contradiction between increasing and decreasing pressure, the forming method is a combination of passive liquid filling and rigid deep drawing. The purpose is to automatically eliminate beneficial wrinkles 33 through rigid mold closing when wrinkles are not obvious or even too late to form. The purpose of taking the above measures is to increase the shape of the first transition shape 13 as much as possible while avoiding dead wrinkles.

[0058] Step 7) Refer to the attached Figure 4 , Attachment Figure 8 , Attachment Figure 9According to the third process model 15, the second semi-finished product 26 is actively liquid-filled and deep-drawn, so that the first transitional shape 13 at its lower portion expands and forms into the second transitional shape 16. The outer wall of the second transitional shape includes the outer walls of the second air inlet 3 and the third air inlet 4, forming a third semi-finished product 27 that matches the third process model 15. It should be emphasized that the active liquid-filled deep-drawing and bulging of the third semi-finished product 27 is performed in two steps. During the pre-bulging process, a solid mixture 34 is filled on the lower surface of the first transitional shape 13 at the third air inlet of the second semi-finished product 26; the purpose is to pre-bulge the first transitional shape 13 along the length of the third air inlet 4. After the pre-bulging, the first transitional shape 13 also forms a material storage bulge 35 in the third air inlet. During the final bulging process, the solid mixture 34 is cleared, so that the pre-bulged first transitional shape 13 expands and forms along the depth direction of the third air inlet 4. The first transitional shapes 13 on both sides of the third air inlet first undergo suspended deformation, and then gradually complete mold attachment as the liquid increases. The following three points require explanation: First, the disadvantages of traditional active liquid filling are large overhangs and the tendency for flat areas to adhere to the mold first. As the liquid pressure increases, the frictional resistance between the mold and the material increases, and the relatively small fillet areas on both sides of the third air inlet 4 are the last to adhere to the mold, which can easily break. Furthermore, the mold surfaces on both sides of the saddle area of the second air inlet 2 are prone to wrinkling due to uneven deformation. Second, the purpose of filling the soft solid mixture 34 during pre-bulging is as follows: one purpose is to induce the mold surface of the first transition profile 13 at the third air inlet to expand preferentially along the length of the third air inlet 4; the second purpose is to reduce friction between the second transition profile 16 and the mold, shifting the deformation-maintaining force transmission area to the inner root area of the flange edge with the greatest thickness, forcing more material to flow into the third flange edge 17; the third purpose is to form a material storage bulge 35 in the middle of the third air inlet 4 to alleviate the thinning on both sides of the third air inlet 4; and the fourth purpose is to increase the initial pressure at the beginning of deformation of the first transition profile 13, causing its inner and outer surfaces to deform under bidirectional high pressure, thereby preventing insufficient support force and wrinkling of the mold surface in the saddle area of the second air inlet 2. Third, the solid mixture 34 is required to consist of a loose mixture of fine particles composed of moist soil, fine sand, sawn wood, and plastic. Its purpose is to ensure a certain degree of compressibility, agglomerate under high pressure for easy cleaning, and disperse under stress in its natural state for recyclability. The ultimate goal of these measures is not only to prevent bulging and cracking during this step, but also to maintain sufficient thickness to allow for increased deformation of the supplementary surface during the rubber forming of the fourth semi-finished product 28.

[0059] Step 8) Refer to the attached Figure 10The third semi-finished product 27 is rubber-formed according to the fourth process model 18, partially forming the second transition profile 16 of the second and third air inlets 3 and 4. First and second annular ribs 29 and 30 are formed on the second transition profile 16, corresponding to the positions of the first and second annular grooves 19 and 20, respectively, to form a fourth semi-finished product 28. The depth of the first and second annular ribs 29 and 30 in the fourth semi-finished product is less than the height of the first and second annular grooves 19 and 20, respectively. Two points are important to emphasize: First, the purpose of the rubber is to utilize the non-effective surface to fully thin the material to maintain the deformation process, fully utilizing the material's high double-tension thinning limit, significantly reducing the thinning of the inner sidewall edges of the second and third air inlets 3 and 4 after forming. Second, before the fourth semi-finished product is rubber-formed, the first annular groove 19 of the second air inlet, the second annular groove 20 of the third air inlet, the first supplementary surface 21 of the first annular groove, and the second supplementary surface 22 of the second annular groove are lubricated to further improve the uniformity of the supplementary surface thinning.

[0060] Step 9) Refer to the attached Figure 11 , after cutting and removing the bottom of the pelvic cavity 9 corresponding to the first air inlet, the bottom of the first annular rib 29 corresponding to the second air inlet, and the bottom of the second annular rib 30 corresponding to the third air inlet in the fourth semi-finished product 28. Then, rubber forming is performed on the cut fourth semi-finished product 28 according to the fourth process model to complete the complete forming of the inner wall 5 and the outer wall 6 of the first air inlet, the second air inlet, and the third air inlet; forming a finished product of the rectifier lip 1 that matches the surface of the fourth process model 18. It should be explained that the fourth semi-finished product 28 will be deformed due to stress release or force during the cutting process, so the rubber forming has two purposes: one is to finally form the inner wall of the second air inlet 3 and the third air inlet 4; the other is to perform overall correction on the cutting deformation of the fourth semi-finished product 28.

[0061] Finally, in order to facilitate those skilled in the art to correctly understand the technical connotation of this application, further supplementary explanation is required:

[0062] First, the integral forming of the turboprop engine fairing lip involved in this application is the two contradictory extremes of wrinkling and cracking in the traditional sheet metal plastic field. It is an extremely difficult product that pursues the ultimate in forming process design and implementation skills. It is recommended that people who are not professional enough in this field should not imitate it at will. Each link of the technical solution involved in this application strives to maximize the formability of metal materials. Therefore, the technical solutions listed in this application specification are as optimal implementation plans as possible, but it should be emphasized that this technical method is not the only implementation plan for all similar products. If the implementer appropriately adjusts the technical solution to achieve similar overall forming purposes based on the shape differences of similar products, the formability of the material, etc., it should be within the scope of protection of this application.

[0063] Second, the key areas of protection for this application are as follows: First, the design structure of the turboprop aircraft engine fairing lip, primarily the structural feature of the lip's inner side walls being independent of each other and the outer side walls being streamlined and connected as a whole. This is unrelated to the specific shape, size, or number of the lip's air inlets, or whether or not they are machined as a whole. Therefore, similarly shaped fairing lips, even if artificially machined separately, fall within the scope of protection for this application. Second, the design scheme and implementation method for the integral forming process of the turboprop aircraft engine fairing lip, primarily including: a deformation sequence that forms the inner side first and then the outer side for similar products; a process concept for gradually increasing the transition model's profile from small to large and from shallow to deep; and key implementation points for achieving optimal results, including forming methods, deformation distribution, and material transfer from ineffective surfaces to compensate for effective surfaces. This is unrelated to whether rigid or flexible drawing methods are used, the number of gradients, or the specific shape of the gradient transition model. For similar products with relatively simple shapes or relatively small deformation, similar effects can be achieved by simply borrowing the process model concept or intentionally replacing the operating methods of each implementation link, such as changing flexible drawing to rigid drawing, or appropriately increasing or reducing specific steps. Therefore, borrowing some of the technologies in this application for the formation of similar products should also fall within the scope of protection of this application.

Claims

1. A turboprop aircraft engine fairing lip, characterized by: The turboprop aircraft engine fairing lip is an integrally formed metal sheet metal shell structure, on which three independent air inlets are provided. The first air inlet is located at the upper part of the shell structure and is an approximately circular fairing shell. The second air inlet is located in the middle part of the shell structure and is an approximately square fairing shell. The third air inlet is located at the lower part of the shell structure and is an approximately elliptical fairing shell. Each air inlet includes an inner wall and an outer wall. The tops of the inner wall and the outer wall are connected in a parabolic shape. The inner walls of the three air inlets are independent of each other, and the outer walls of the three air inlets are connected as a whole.

2. The turboprop aircraft engine fairing lip according to claim 1, characterized in that: The height and width of the outer side wall of the second air inlet of the turboprop aircraft engine fairing lip are both smaller than the height and width of the first air inlet and the third air inlet, and the outer side wall of the second air inlet connects the outer side walls of the first air inlet and the third air inlet through an inverted saddle curved surface streamline.

3. The flexible integral forming method of the turboprop aircraft engine fairing lip according to claim 1 or 2, wherein the design digital model of the fairing lip is known, characterized in that Contains the following: 1) Based on the design digital model of the rectifying lip, a first process model is constructed. The first process model includes a basin and a first flange. The sidewall of the basin includes the inner sidewall of the first air inlet. The bottom of the basin is a process-supplemented circular bottom surface. The first flange is coplanar with the top surface of the first air inlet, and its contour matches the planar unfolded contour of the outer sidewall of the rectifying lip. 2) Based on the design digital model of the rectifying lip and the first process model, a second process model is constructed. In the second process model, the first flange edge on the outer side of the basin of the first process model is formed into the outer side wall of the first air inlet and the first transition shape and second flange edge of the second and third air inlets. The first transition shape is a raised shell-like body. The edge of the first transition shape matches the edge of the outer side wall of the second and third air inlets. The height of the first transition shape is less than the corresponding height of the outer side wall of the second and third air inlets. The second flange edge surrounds the outer side wall of the first air inlet and the edge of the first transition shape. 3) constructing a third process model based on the design digital model of the rectifying lip and the second process model. In the third process model, the first transitional profiles of the second and third air inlets are formed into second transitional profiles of the second and third air inlets, and the second flange edge of the second process model is formed into a third flange edge. The outer wall of the second transitional profile includes the outer walls of the second and third air inlets, and the third flange edge surrounds the outer wall edge of the rectifying lip. 4) Constructing a fourth process model based on the design digital model of the rectifying lip and the third process model. The fourth process model includes a first annular groove and a second annular groove corresponding to the second and third air inlets. The outer wall of the first annular groove matches the inner wall of the second air inlet, and the top of the inner wall of the first annular groove forms a first supplementary surface. The outer wall of the second annular groove matches the inner wall of the third air inlet, and the top of the inner wall of the second annular groove forms a second supplementary surface. 5) Passively filling and deep drawing the unfolded sheet material according to the first process model to form a basin cavity and a first flange edge corresponding to the first air inlet of the rectifying lip, thereby forming a first semi-finished product matching the first process model; 6) performing passive liquid-filling deep drawing on the first semi-finished product according to the second process model to form the outer wall of the first air inlet, the second flange edge, and the first transitional shapes of the second air inlet and the third air inlet, thereby forming a second semi-finished product matching the second process model; 7) Actively filling and deep-drawing the second semi-finished product according to the third process model so that the first transitional shape at its lower portion expands and forms into the second transitional shape, the outer wall of the second transitional shape including the outer walls of the second and third air inlets, thereby forming a third semi-finished product matching the third process model; 8) forming the third semi-finished rubber product according to the fourth process model, partially forming the second transition profiles of the second air inlet and the third air inlet, forming first and second annular ribs on the second transition profile corresponding to the positions of the first and second annular grooves, respectively, to form a fourth semi-finished product, wherein the depths of the first and second annular ribs of the fourth semi-finished product are respectively less than the heights of the first and second annular grooves; 9) After cutting and removing the bottom of the pelvic cavity corresponding to the first air inlet, the bottom of the first annular rib corresponding to the second air inlet, and the bottom of the second annular rib corresponding to the third air inlet in the fourth semi-finished product, the fourth semi-finished product is rubber-formed according to the fourth process model of the rectifying lip to complete the complete forming of the inner and outer walls of the first air inlet, the second air inlet, and the third air inlet, thereby forming a rectifying lip finished product that matches the fourth process model.

4. The flexible integral forming method of the turboprop aircraft engine fairing lip according to claim 3, characterized in that : In step 1), the projected edge spacing of the first flange edge of the first process model from the outer wall of the rectifying lip on the first flange edge is a streamline variable width structure, and the projected edge spacing is widest on both sides of the minimum cross-section of the saddle surface.

5. The flexible integral forming method of the turboprop aircraft engine fairing lip according to claim 3, characterized in that : In step 2), the second flange edge contour of the second process model is generally smaller than the first flange edge contour of the first process model. The second flange edge is a streamlined variable width structure, and its width is narrowest in the outer wall area of the first air inlet and widest on both sides of the minimum cross-section of the saddle surface of the second air inlet.

6. The flexible integral forming method of the turboprop aircraft engine fairing lip according to claim 3, characterized in that : The third flange edge of the third process model described in step 3) is in the same height plane as the second flange edge of the second process model. The third flange edge is also a streamlined variable width structure. The third flange edge matches the contour of the second flange edge of the second process model in the minimum cross-sectional area of the saddle surface from the first air inlet to the second air inlet. The third flange edge is narrowest in the outer wall area of the third air inlet and widest on both sides of the minimum cross-sectional area of the saddle surface of the second air inlet.

7. The flexible integral forming method of the turboprop aircraft engine fairing lip according to claim 3, characterized in that : In step 4), the width of the first annular groove and the second annular groove of the fourth process model is 15-20 times the thickness of the sheet to be formed, and the height difference from the first supplementary surface of the first annular groove and the second supplementary surface of the second annular groove to the top surface of the first annular groove and the second annular groove is 0.10-0.15 times the width of the inner side wall of the second air inlet and the third air inlet respectively.

8. The flexible integral forming method of the turboprop aircraft engine fairing lip according to claim 3, characterized in that : In step 5), the passive liquid filling and deep drawing deformation of the first semi-finished product is divided into two stages. In the first stage, the unfolded sheet is pre-expanded upward so that the first process model supplements the circular bottom surface to form a shallow spherical bulge. In the second stage, the spherical bulge is flattened and the liquid pressure is continuously increased as the depth of the pelvic cavity increases until the pelvic cavity of the first semi-finished product is completely formed.

9. The flexible integral forming method of the turboprop aircraft engine fairing lip according to claim 3, characterized in that : In step 6), the passive liquid filling deep drawing of the second semi-finished product is divided into three stages. In the first stage, the liquid pressure on the lower surface of the first semi-finished product is increased as the forming depth increases, and suction wrinkles and bulges are formed on both sides of the saddle surface of the second air inlet; in the second stage, the liquid pressure on the lower surface of the first semi-finished product is reduced as the forming depth increases, so that the suction wrinkles and bulges on both sides of the saddle surface of the second air inlet gradually disappear, and beneficial wrinkles are formed on the top surface of the second air inlet; in the third stage, rigid mold closing automatically eliminates the beneficial wrinkles.

10. The flexible integral forming method of the turboprop aircraft engine fairing lip according to claim 3, characterized in that : The active liquid filling deep drawing and bulging of the third semi-finished product described in step 7) is carried out in two steps. First, the pre-bulging is performed to pre-expand the first transition shape at its lower part along the length direction of the third air inlet, and a material storage bulge is formed in the third air inlet after the pre-expansion; then the final bulging is performed to expand the first transition shape along the depth direction of the third air inlet after the pre-expansion, and the first transition shape surfaces on both sides of the third air inlet first produce suspended deformation, and then gradually complete the mold attachment as the liquid increases.

11. The method for flexible integral forming of a turboprop aircraft engine fairing lip according to claim 10, characterized in that : In step 7), during pre-bulging, the soft solid mixture is filled on the lower surface of the first transition shape of the third air inlet of the second semi-finished product, and during final bulging, the soft solid mixture is cleaned from the lower surface of the first transition shape after pre-bulging.

12. The flexible integral forming method of the turboprop aircraft engine fairing lip according to claim 10 or 11, characterized in that : The solid mixture used in step 7) has the characteristics of being compressible in volume, agglomerated under high pressure, dispersible under force in a natural state, and recyclable.

13. The flexible integral forming method of the turboprop aircraft engine fairing lip according to claim 3, characterized in that : Before the fourth semi-finished rubber is formed in step 8), the first annular groove of the second air inlet, the second annular groove of the third air inlet, the first supplementary surface of the first annular groove, and the second supplementary surface of the second annular groove are lubricated with oil.

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