An aero-engine blade and a method for machining and filling the cavity of the blade.

Abstract

This invention provides an aero-engine blade with weight-reduction cavities at both ends to meet lightweight requirements without affecting the blade's strength and stiffness, thus ensuring the blade's quality. It includes a blade body, with the blade tip and blade root at its two ends, respectively. Weight-reduction cavities extending towards the blade body are respectively located at the blade tip and blade root.

Description

Technical Field

[0001] This invention relates to the field of aero-engine blade technology, specifically to an aero-engine blade and a method for machining and filling the cavity of the blade. Background Technology

[0002] The engine is the power source and heart of an aircraft, and the engine blades are one of its key components. Their importance lies not only in their impact on the overall engine performance but also in their direct relation to the engine's reliability and durability. Fan blades are generally made of titanium alloys and composite materials. Since reducing the mass of fan blades is an effective way to reduce engine mass and improve engine efficiency, lightweighting has become a crucial aspect of engine research and development.

[0003] Traditional blades are designed with a hollow, sandwich structure to achieve lightweighting. However, this structure offers limited weight reduction. Chinese invention patent application number CN202121374917.X discloses a hollow exit guide vane assembly, an aero-engine, and an aircraft. This design increases the blade's hollowness and reduces its weight by incorporating multiple recessed areas on the blade surface. However, even with this method, since the aero-engine's exit guide vane surface primarily bears the external pressure load during operation, the multiple recessed areas on the blade surface can still affect the blade's strength and stiffness, ultimately impacting its overall quality. Summary of the Invention

[0004] Despite the existing design for lightweighting engine blades, the blade's strength and stiffness are still affected, ultimately impacting its quality. This invention provides an aero-engine blade with weight-reduction cavities at both ends, meeting the lightweighting requirements without compromising the blade's strength and stiffness, thus ensuring its quality.

[0005] The technical solution is as follows: an aero-engine blade, comprising a blade body, wherein the two ends of the blade body are a blade tip and a blade root, characterized in that: a weight-reducing cavity extending toward the blade body is provided at the blade tip and the blade root.

[0006] A further feature is that the weight-reducing cavity at the leaf tip accounts for approximately 2-5% of the volume of the leaf body, and the weight-reducing cavity at the leaf root accounts for approximately 5-8% of the volume of the leaf body.

[0007] The method for processing the blade cavity of the aero-engine blade includes the following steps:

[0008] S1. Pre-drilling: Using a five-axis linkage machining tool, select a drill bit of appropriate diameter to drill holes at equal intervals along the weight reduction cavity position at the tip of the blade to remove most of the machining allowance.

[0009] S2. Spiral milling to clear corners: The rounded corners at both ends of the weight reduction cavity are machined by a ball end mill in a spiral machining manner to remove the machining allowance of the rounded corners at both ends. During the milling of the rounded corners, the direction of the cutter axis is controlled by the cutter axis control point.

[0010] S3. Fine milling of irregular deep cavity: Using different ball end mills, the entire weight reduction cavity is finely milled in a helical manner according to the spline curve controlling the direction of the milling cutter axis. The spline curve is formed by connecting the control points of the cutter axis at the cutting section position of each milling cutter.

[0011] S4. Repeat steps S1 to S3 above to process the weight-reducing cavity at the leaf root.

[0012] In step S1, the diameter of the drill bit is selected according to the minimum groove width of its machining position and the single-sided allowance is 0.2~0.5mm. The drilling axis direction of the drill bit is parallel to the direction of the center line of the cross section of the weight reduction cavity where the drill hole is located.

[0013] In step S2, the relationship between the diameter D2 of the milling cutter and the fillet radius R at both ends of the weight reduction cavity is 1.2R≤D2≤1.6R;

[0014] In step S2, the cutter axis control point is selected by choosing the two furthest tangent points at the lowest milling position of the milling cutter in the weight reduction cavity. At this time, the intersection point formed by the intersection of the axes of the milling cutter is the cutter axis control point.

[0015] The method for filling the blade cavity of the aero-engine blade includes the following steps:

[0016] S1. Using a funnel, a measured amount of powdered epoxy foam adhesive is filled into the weight reduction cavity at the blade tip in 3 to 6 portions. After filling, a scraper is used to smooth the adhesive on the surface of the weight reduction cavity at the blade tip.

[0017] S2. Place the blade on the clamping device and clamp it in place. The clamping device will press and seal the adhesive at the tip of the blade.

[0018] S3. The clamping device is placed into a heating furnace for curing. The curing temperature is 175±5℃, the curing time is 2-3 hours, and the heating rate is 1.3-2℃ / minute. When the heating furnace is heated to 80℃ and 120℃, it is kept at the temperature for half an hour.

[0019] S4. Cooling, and disassembling the blade from the clamping device;

[0020] S5. Repeat steps S1 to S4 above to fill the weight-reducing cavity at the leaf root.

[0021] In S2, the clamping device includes a triangular bracket with a movably connected base. A blade tip clamping mechanism and a blade root clamping mechanism are respectively provided on both sides of the base. The blade tip clamping mechanism includes a hinged positioning seat and a pressing seat. The movable end of the positioning seat and the movable end of the pressing seat are connected by a pin. The positioning seat has a limiting groove that adapts to the protrusion at the blade tip. The pressing seat has a V-shaped positioning block that mates with the protrusion at the blade tip. A first mounting seat is also fixedly installed outside the positioning seat. A first tightening bolt is movably connected through the first mounting seat. The other end of the first tightening bolt is connected to a first contouring pressure block that matches the weight-reducing cavity at the blade tip.

[0022] The blade root clamping mechanism includes a positioning plate mounted on the base. The positioning plate is provided with a positioning slot that matches the shape of the blade root. The two sides of the blade root are also connected to rotatably connected pressure plates via mounting blocks. A second mounting seat is also fixedly connected to the positioning plate. A second tightening bolt is movably connected through the second mounting seat. The other end of the second tightening bolt is connected to a second contoured pressure block that matches the weight reduction cavity of the blade root.

[0023] The first positioning seat and the second positioning seat are respectively provided with through grooves on the moving paths of the first tightening bolt and the second tightening bolt. The through grooves are respectively provided with sliding blocks that are movably connected. The ends of the first tightening bolt and the second tightening bolt extend into the sliding block from one end and are respectively limited by the nuts on it. The other end of the sliding block is respectively connected to the first conforming pressure block and the second conforming pressure block.

[0024] By adopting the above structure, the weight-reducing cavities set at the top and bottom of the blade can meet the requirements for lightweighting without affecting the strength and stiffness of the blade, thus ensuring the quality of the blade.

[0025] Meanwhile, the weight-reduction cavities at the blade tip and root are machined using a five-axis linkage machining center, and precise tool axis control enables the precision machining of this irregular narrow groove.

[0026] Furthermore, the weight-reducing cavities at the blade tip and root are filled and cured with powdered epoxy foam adhesive. During curing, the cavities are sealed by clamping devices. Due to the foaming properties of the adhesive, the complex structure inside the cavity can be fully filled, providing the blade with a certain strength as structural support, thus ensuring the strength and rigidity of the blade. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of the blade of the present invention;

[0028] Figure 2 This is a schematic diagram of the leaf root portion of the blade of the present invention;

[0029] Figure 3 This is a schematic diagram of the blade tip of the present invention;

[0030] Figure 4 This is a schematic diagram showing the pre-drilling location of the weight reduction cavity in this invention;

[0031] Figure 5 This is a schematic diagram of the pre-drilled section angle of the weight reduction cavity of the present invention;

[0032] Figure 6 For the present invention Figure 4 The angle A1 between the two cross sections of the weight-reducing cavity and the vertical direction;

[0033] Figure 7 For the present invention Figure 4 The angle A2 between the two cross sections of the weight-reducing cavity and the vertical direction;

[0034] Figure 8 This is a schematic diagram showing the two rounded corner milling positions of the weight reduction cavity in this invention;

[0035] Figure 9 This is a schematic diagram of the tool axis control point used to control the tool axis direction during the milling of the weight reduction cavity of the present invention;

[0036] Figure 10 This is a schematic diagram of a spline curve formed by connecting the control points of the cutter shaft in series according to the present invention;

[0037] Figure 11 This is a schematic diagram of the clamping device of the present invention;

[0038] Figure 12 This is a schematic diagram of the base and structure of the present invention;

[0039] Figure 13 For the present invention Figure 11 Cross-sectional view of the structure at point A in the middle. Detailed Implementation

[0040] like Figures 1 to 3As shown, an aero-engine blade includes a blade body 1. The blade body 1 has a honeycomb-shaped filling structure on its surface and a cover plate on it. The two ends of the blade body 1 are the blade tip 2 and the blade root 3, respectively. The blade tip 2 and the blade root 3 are respectively provided with weight-reducing cavities 4 extending towards the blade body 1. The cross-section of the weight-reducing cavity 4 in the blade tip 2 is an arc-shaped cavity with one end larger and the other end smaller, while the cross-section of the weight-reducing cavity 4 in the blade root 3 is approximately crescent-shaped.

[0041] Furthermore, the weight-reducing cavity 4 at the tip of the leaf 2 accounts for approximately 2-5% of the volume of the leaf body 1, and the weight-reducing cavity 4 at the root of the leaf 3 accounts for approximately 5-8% of the volume of the leaf body 1. Through the design of the weight-reducing cavities at both ends of the leaf body 1, the lightweight design requirements of the blade are met.

[0042] This invention provides a method for processing the blade cavity based on the above-mentioned aero-engine blade, which includes the following steps:

[0043] S1. Pre-drilling, processed using a five-axis CNC machining center, such as... Figure 4 and Figure 5 As shown, a drill bit of suitable diameter is selected to drill at equal intervals along the weight-reducing cavity at the blade root 2, removing most of the machining allowance. The drill bit diameter is selected according to the minimum groove width at the machining location, with a single-sided allowance of 0.2~0.5mm. Figure 5 As shown, the direction of the drill bit's cutting axis is parallel to the direction of the center line of the cross section of the weight-reducing cavity where the borehole is located.

[0044] S2, spiral milling for corner clearing, such as Figure 6 As shown, a ball end mill is used to machine the fillets at both ends of the weight-reducing cavity using a helical machining method. This removes the machining allowance at the fillets, preventing problems such as poor chip removal and machining vibration at the fillet positions during finishing. Figure 7 As shown, during the milling of fillets, the direction of the cutter axis is controlled by the cutter axis control point. The cutter diameter D2 is selected such that the relationship between D2 and the fillet radius R at both ends of the weight-reducing cavity is 1.2R ≤ D2 ≤ 1.6R. Simultaneously, as... Figure 8 As shown, when the milling cutter is machining the left and right sidewalls at the bottom of the weight-reducing cavity, the center lines of the cutter at the maximum tilt angle intersect to form an intersection point. This intersection point is selected as the cutter axis control point. During the milling process, the cutter axis of the milling cutter is controlled by the selection of the cutter axis control point, ensuring that there is no overcutting of the deep cavity sidewalls at any cutting position of the milling cutter.

[0045] S3, precision milling of irregular deep cavities, such as Figure 9As shown, different ball end mills are used to perform precision milling of the weight reduction cavity in a helical manner according to the spline curve controlling the direction of the milling cutter axis. The spline curve is formed by connecting the control points of the milling cutter axis at the cutting section position of each milling cutter. During the deep cavity finishing process, the milling cutter axis always passes through this spline curve to achieve precise control of the milling cutter axis, ensuring that the side edge of the tool will not overcut the side wall of the deep cavity at any cutting position.

[0046] S4. Repeat steps S1 to S3 above to process the weight reduction cavity at the tip of the blade.

[0047] The working principle of the method of the present invention is as follows:

[0048] Because the weight-reducing cavity 4 of the engine blade in this invention is an irregular cavity, characterized by narrow groove width, deep depth, and long length, the length-to-diameter ratio of the milling tool required for machining is more than 10 times. During cutting, the tool rigidity is poor, and machining defects are easily caused by tool vibration. Simultaneously, the curvature of the sidewalls of the irregular deep cavity varies greatly, making it prone to overcutting due to tool axis oscillation during machining. Therefore, by adopting the above-described machining method, through reasonable material removal and precise tool axis control, the abnormal problems of large curvature variations in the irregular narrow groove, large tool length-to-diameter ratio, easy overcutting, and vibration are solved.

[0049] This invention provides a method for filling the cavity of an aero-engine blade, comprising the following steps:

[0050] S1. Using a funnel, fill a measured amount of powdered epoxy foam adhesive into the weight-reducing cavity at the top of the blade in 3 to 6 portions. After each filling, shake the blade to ensure it adheres fully to the inner wall of the cavity and is evenly distributed within the cavity. After filling, use a scraper to smooth the adhesive on the surface of the weight-reducing cavity at the top of the blade.

[0051] S2. Place the blade 1 on the clamping device and clamp it in place. The clamping device will press and seal the adhesive at the top of the blade 2 to prevent the adhesive from leaking.

[0052] S3. The clamping device and its upper blades are fed into a heating furnace for curing. The curing temperature is 175±5℃, the curing time is 2-3 hours, and the heating rate is 1.3-2℃ / minute. When the heating furnace is heated to 80℃ and 120℃, it is kept at the temperature for half an hour. This heat preservation process can make the adhesive foam more fully, which is beneficial to fitting the internal shape of the cavity.

[0053] S4. Cooling, and disassembling the blade from the clamping device;

[0054] S5. Repeat steps S1 to S4 above to fill the weight-reducing cavity at the leaf root.

[0055] Preferably, in S2, such as Figures 10 to 12 As shown, the clamping device includes a triangular bracket 5, on which a base 6 is movably connected. The base 6 is inserted into the triangular bracket 5 and placed vertically. Since the top of the triangular bracket 5 has a movably connected limiting block 51, and the middle of the triangular bracket 5 has a fixedly connected limiting shaft 52, the base 6 can be limited and fixed through the limiting block 51 and the limiting shaft 52. The base 6 has a blade tip clamping mechanism 7 and a blade root clamping mechanism 8 on both sides, respectively. The blades are clamped and fixed through the blade tip clamping mechanism 7 and the blade root clamping mechanism 8, while simultaneously covering and sealing the weight-reducing cavities at the blade root and blade tip. Specifically, the blade tip clamping mechanism 7 includes a positioning seat 71 and a clamping seat 72 that are hinged together. The positioning seat 71 is fixedly connected to the base 6, and the clamping seat 72 can rotate relative to the positioning seat 71. After closing, the movable end of the positioning seat 71 and the movable end of the clamping seat 72 are connected by a pin. The positioning seat 71 is also provided with a limiting groove that is adapted to the protrusion at the blade tip. The clamping seat 72 is provided with a V-shaped positioning block that cooperates with the protrusion at the blade tip. A first mounting seat 73 is also fixedly installed on the outside of the positioning seat 71. A first tightening bolt is provided through the first mounting seat 73 and is movably connected. The other end of the first tightening bolt is connected to a first contouring pressure block 74 that matches the weight reduction cavity at the blade tip.

[0056] Specifically, the blade root clamping mechanism 8 includes a positioning plate 81 mounted on the base 6. The positioning plate 81 is provided with a positioning slot that matches the shape of the blade root. The two sides of the blade root are also connected to a rotating pressure plate 82 via mounting blocks. A second mounting seat is also fixedly connected to the positioning plate 81. A second tightening bolt is provided through the second mounting seat. The other end of the second tightening bolt is connected to a second contouring pressure block 83 that matches the weight reduction cavity of the blade root.

[0057] Specifically, the first positioning seat and the second positioning seat are provided with through grooves 75 on the moving paths of the first tightening bolt and the second tightening bolt, respectively. The through grooves 75 are respectively provided with sliding blocks 76 that are movably connected. The ends of the first tightening bolt and the second tightening bolt extend into the movably connected sliding block from one end and are respectively limited by the nuts on them. The other end of the sliding block 76 is respectively connected to the first contouring block and the second contouring block. During operation, after filling the blade tip 2 or blade root 3 of the adhesive machine, the blade root and blade tip are pressed and fixed by the blade root clamping device and the blade tip clamping device respectively. By rotating the first tightening bolt or the second tightening bolt, the first conforming pressure block 74 or the second conforming pressure block 83 is driven to seal the weight-reducing cavity of the blade tip 2 or blade root 3. At the same time, in order to prevent the conforming pressure block from sticking to the adhesive machine, PI polyimide tape is pasted on the conforming pressure block to prevent the pressure block from sticking to the adhesive after curing. Several grooves with a width of 1-2mm are drawn on the tape as air guide grooves to facilitate the discharge of gas inside the cavity, making the cavity more compact after curing.

[0058] Using the filling method of the present invention, the powdered epoxy foam adhesive, before curing, is a solid substance and can conform to the arc segments and height differences on the outer surface of the cavity, unlike fluid fillers which are affected by gravity and have difficulty fixing their shape. After curing, due to its foaming properties, it can fully fill the complex structure inside the cavity, thereby meeting the requirements of high strength and lightweight blades.

[0059] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for machining the cavity of an aero-engine blade, characterized in that: The cross-section of the weight-reducing cavity at the tip of the leaf is an arc-shaped cavity with one end larger than the other, while the cross-section of the weight-reducing cavity at the root of the leaf is crescent-shaped; the weight-reducing cavity is an irregular cavity, and the curvature of the sidewall of the irregular cavity varies greatly. The processing method includes the following steps: S1. Pre-drilling: Using a five-axis linkage machining tool, select a drill bit of appropriate diameter to drill holes at equal intervals along the weight reduction cavity position at the tip of the blade to remove most of the machining allowance. S2. Spiral milling to clear corners: The rounded corners at both ends of the weight reduction cavity are machined by a ball end mill in a spiral machining manner to remove the machining allowance of the rounded corners at both ends. During the milling of the rounded corners, the direction of the cutter axis is controlled by the cutter axis control point. The length-to-diameter ratio of the cutting tools used in milling is more than 10 times; The cutter axis control point is selected from the two furthest tangent points at the milling position of the milling cutter at the lowest end of the weight reduction cavity. The intersection point formed by the intersection of the axes of the milling cutter at this time is the cutter axis control point. The method for selecting the cutter axis control point P is as follows: when the milling cutter is machining the left and right side walls at the lowest end of the weight reduction cavity, the center lines of the cutter at the maximum tilt angle intersect to form an intersection point, and this intersection point is selected as the cutter axis control point P. S3. Fine milling of irregular deep cavity: Using different ball end mills, the entire weight reduction cavity is finely milled in a helical manner according to the spline curve controlling the direction of the milling cutter axis. The spline curve is formed by connecting the control points P of the milling cutter axis at the cutting section position of each milling cutter. S4. Repeat steps S1 to S3 above to process the weight reduction cavity at the leaf root. The cavity of the blade obtained after final processing is as follows: The leaf tip and leaf root are respectively provided with weight-reducing cavities extending towards the leaf body; the weight-reducing cavity at the leaf tip occupies 2-5% of the volume of the leaf body, and the weight-reducing cavity at the leaf root occupies 5-8% of the volume of the leaf body.

2. The method for processing the blade cavity according to claim 1, characterized in that: In step S1, the diameter of the drill bit is selected according to the minimum groove width of its machining position and the single-sided allowance is 0.2~0.5mm. The drilling axis direction of the drill bit is parallel to the direction of the center line of the cross section of the weight reduction cavity where the drill hole is located.

3. The method for processing the blade cavity according to claim 1, characterized in that: In step S2, the relationship between the diameter D2 of the milling cutter and the radius R of the two ends of the weight reduction cavity is 1.2R≤D2≤1.6R.

4. A method for filling the cavity of an aero-engine blade, characterized in that, It includes the following steps: The cavity that needs to be filled is: The weight-reducing cavity at the leaf tip accounts for 2-5% of the leaf body volume, and the weight-reducing cavity at the leaf root accounts for 5-8% of the leaf body volume. The cross-section of the weight-reducing cavity at the top of the leaf is an arc-shaped cavity with one end larger than the other, while the cross-section of the weight-reducing cavity at the root of the leaf is crescent-shaped; both ends of the weight-reducing cavity are rounded. The weight-reducing cavity is an irregular cavity, and the curvature of the sidewalls of the irregular cavity varies greatly; S1. Using a funnel, a measured amount of powdered epoxy foam adhesive is filled into the weight reduction cavity at the blade tip in 3 to 6 portions. After filling, a scraper is used to smooth the adhesive on the surface of the weight reduction cavity at the blade tip. S2. Place the blade on the clamping device and clamp it in place. The clamping device will press and seal the adhesive at the tip of the blade. S3. The clamping device is placed into a heating furnace for curing. The curing temperature is 175±5℃, the curing time is 2-3 hours, and the heating rate is 1.3-2℃ / minute. When the heating furnace is heated to 80℃ and 120℃, it is kept at the temperature for half an hour each time. S4. Cooling, and disassembling the blade from the clamping device; S5. Repeat steps S1 to S4 above to fill the weight-reducing cavity at the leaf root. In S2, the clamping device includes a triangular bracket with a movably connected base. A blade tip clamping mechanism and a blade root clamping mechanism are respectively provided on both sides of the base. The blade tip clamping mechanism includes a hinged positioning seat and a pressing seat. The movable end of the positioning seat and the movable end of the pressing seat are connected by a pin. The positioning seat has a limiting groove that adapts to the protrusion at the blade tip. The pressing seat has a V-shaped positioning block that mates with the protrusion at the blade tip. A first mounting seat is also fixedly installed outside the positioning seat. A first tightening bolt is movably connected through the first mounting seat. The first tightening bolt is connected to a first contouring pressure block that matches the weight-reducing cavity at the blade tip. The blade root clamping mechanism includes a positioning plate mounted on the base. The positioning plate is provided with a positioning slot that matches the shape of the blade root. The two sides of the blade root are also connected to rotating pressure plates via mounting blocks. A second mounting seat is also fixedly connected to the positioning plate. A second tightening bolt is provided through the second mounting seat and is movably connected. The second tightening bolt is connected to a second contouring pressure block that matches the weight reduction cavity of the blade root. Polyimide tape is pasted on the two molding blocks to prevent the first and second molding blocks from sticking to the adhesive after curing. Several grooves with a width of 1-2 mm are also made on the tape as air guide grooves. The first mounting base and the second mounting base are respectively provided with through grooves on the moving paths of the first tightening bolt and the second tightening bolt. Each through groove is provided with a movable sliding block. The ends of the first tightening bolt and the second tightening bolt extend into the movable connection from one end of the sliding block and are respectively limited by the nuts on them. The other end of the sliding block is respectively connected to the first conforming pressure block and the second conforming pressure block.

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