Curved swept blade and design method thereof

Abstract

The curved-swept blade design method comprises the following steps that a blade in the area above the gravity center of a blade tenon rotates around the axis of an engine, the blade in the area from the gravity center of the tenon to 30% of the blade height position rotates around the axis of the engine to the blade back direction, and the blade in the area above the gravity center of the tenon to the blade back direction; and an included angle is formed between the element-level gravity center of the runner hub and the connecting line of the axis of the engine and the gravity center of the blade tenon. The invention further provides a swept-curved blade. According to the method and the swept-curved blade, smooth transition between the root end area and the middle upper part of the blade can be achieved, the problem of stress concentration is avoided, and smooth transition from the end area in the blade runner to the tenon is achieved.

Description

Technical Field

[0001] This invention relates to the field of aero-engines, and more specifically to the field of swept blade design methods. Background Technology

[0002] To achieve economic efficiency and reduce fuel consumption, the bypass ratio of fan blades is increased, while the hub ratio is decreased. On the other hand, to meet low noise requirements, the tangential velocity at the fan blade tip also tends to decrease. Consequently, both the decrease in hub ratio and the decrease in tip tangential velocity lead to a decrease in the tangential velocity at the fan blade root.

[0003] In the blade tip region, due to the reduced tangential velocity at the blade root and to ensure the boost ratio at the fan root, the blade profile at the root has a large twist angle, with the exit metal angle even bending beyond the axial direction. However, fan tenons, especially those for composite fan blades, tend to use straight tenons to improve forming and processing capabilities. Therefore, the transition from the large bend angle blade profile at the blade root to a straight tenon within a very small radial space easily leads to localized twisting, especially in the leading edge region of the blade. This localized twisting of the blade profile is detrimental to prototyping and manufacturing processes, and creates high-stress areas, causing stress concentration and resulting in insufficient local static or fatigue strength to meet strength requirements, thus reducing blade life. Summary of the Invention

[0004] One object of the present invention is to provide a swept blade design method to achieve a smooth transition from the end area to the tenon in the blade flow channel.

[0005] The sweep blade design method to achieve the above objectives includes the following steps: rotating the blade above the tenon center of gravity around the engine axis, wherein the blade from the tenon center of gravity to the 30% blade height position is rotated around the engine axis toward the blade back, so that the basic-level center of gravity at the flow channel hub forms an angle with the line connecting the engine axis and the blade tenon center of gravity, and 100% blade height is the height from the flow channel hub to the blade tip.

[0006] In one or more embodiments, the line connecting the centers of gravity of each blade in the region from the center of gravity of the tenon to the position of 30% of the blade height is shifted toward the suction surface.

[0007] In one or more embodiments, the method further includes the following steps: the region of the blade from the flow channel hub to the blade tip includes a blade root portion, a blade middle portion, and a blade tip portion; a portion of the blade root portion within the blade flow channel is configured to be swept forward, the blade middle portion is configured to be swept backward, and the blade tip portion is configured to be swept forward, wherein the boundary between the swept-back portion and the swept-forward portion of the blade middle portion is located at 30% to 60% of the blade height, and the boundary between the swept-forward portion and the swept-back portion of the blade tip portion is located at 70% to 90% of the blade height.

[0008] In one or more embodiments, the relationship between the bend and the sweep is made to satisfy the equation δ = σ·tanβ, or the calculated deviation from δ = σ·tanβ is less than ±10%, where δ is the bend angle, σ is the sweep angle, and β is the blade mounting angle.

[0009] In one or more embodiments, the center of gravity of the elementary element at the flow channel hub forms an angle of 5° to 15° with the line connecting the engine axis and the center of gravity of the blade tenon.

[0010] In one or more embodiments, the line connecting the centers of gravity of each blade type in the region from the center of gravity of the tenon to the position of 30% of the blade height is offset towards the suction surface by an angle of 0° to 20°.

[0011] Another object of the present invention is to provide a swept blade, which is designed by the above method.

[0012] The above method solves the problem of stress concentration at the blade root. By rotating part of the fan blade in the flow channel around the engine axis towards the blade back at a certain angle, the center of gravity of the end unit moves relative to the tenon towards the blade back. The circumferential offset of the leading edge and tenon of the unit in the flow channel is significantly reduced, which can greatly improve the twisting phenomenon of the leading edge of the root extension section. The center of gravity of the blade profile is adjusted in the area from the center of gravity of the tenon to 30% of the blade height. The center of gravity of the blade profile between the two sections is shifted towards the suction surface, which facilitates the connection with the root extension section and also allows the leading edge of the blade to transition to the pressure surface more quickly, so as to meet the requirements of aerodynamic blade profile torsion. Attached Figure Description

[0013] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, wherein:

[0014] Figure 1A This is an axial diagram showing the installation position of the fan blades;

[0015] Figure 1B This is an overall diagram of the fan blade installation location;

[0016] Figure 2 This is a schematic diagram of the fan blade structure;

[0017] Figure 3A This is a schematic diagram of the terminal region near the root;

[0018] Figure 3B This is a top view of the near-root end region;

[0019] Figure 3C This is a schematic diagram showing that, in the traditional method, the center of gravity of the engine axis, the tenon, and the center of gravity of the elementary element at the hub in the flow channel are located in the same circumferential position.

[0020] Figure 4 This is a schematic diagram showing the offset of the center of gravity at the hub level within the flow channel;

[0021] Figure 5A This is a diagram showing the height of 30% of the leaves;

[0022] Figure 5B This is a schematic diagram showing the offset of the line connecting the centers of gravity;

[0023] Figure 6A This is a schematic diagram of the upper part of the blade;

[0024] Figure 6B This is a schematic diagram of the sweep angle;

[0025] Figure 7 This is a schematic diagram of the stacking pattern of the swept blades.

[0026] Symbol marking explanation

[0027] 1. Airflow

[0028] 2. Casing

[0029] 3. Leaf blade

[0030] 4-wheel hub

[0031] 5. Root extension segment

[0032] 6-blade disk

[0033] 7 flow channels

[0034] 8. Tenon

[0035] 9. Leaf tip

[0036] 51. Leading edge of the root extension segment

[0037] 201 Engine shaft

[0038] 202 Tenon center of gravity

[0039] 204-channel inner hub elementary center of gravity

[0040] 206 20% Leaf height, center of gravity of leaf shape

[0041] 207 straight tenon

[0042] 208 30% of the leaf height, leaf shape center of gravity

[0043] 209 60% of the leaf height, leaf shape center of gravity

[0044] 404 flow channel inner hub primary stage airfoil

[0045] 408 30% Leaf height leaf shape

[0046] 409 60% Leaf height leaf shape Detailed Implementation

[0047] The present invention will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0048] It should be noted that these and other accompanying drawings are merely examples and are not drawn to scale, and should not be construed as limiting the scope of protection of the present invention.

[0049] like Figures 1A to 2 As shown, the fan blades rotate circumferentially around the engine axis 201. The portion of the fan blade located within the flow channel is the blade body 3, which includes the area from the hub 4 to the blade tip 9. The tenon 8 is the structure that mates with the fan disc. The fan blades drive the airflow 1 into the flow channel 3 defined by the casing 2 and the hub 4. The blade body 3 is mounted onto the blade disc 6 via the tenon 8. The area from the blade tenon to the flow channel hub is the root extension section 5, which is not within the flow channel 7.

[0050] The design of aero-engine blades generally needs to balance performance and economic requirements. To meet economic requirements and reduce fuel consumption, blades typically require an increased bypass ratio and a reduced fan hub ratio.

[0051] Bypass ratio refers to the ratio of airflow through the outer bypass duct to airflow through the inner bypass duct of an engine. A high bypass ratio means more air passes through the outer bypass duct rather than the combustion chamber, which helps reduce fuel consumption and noise levels. Pressure ratio refers to the ratio of compressor outlet pressure to compressor inlet pressure. Hub ratio refers to the ratio of fan hub diameter to fan diameter. A lower hub ratio means a relatively smaller hub, which helps improve aerodynamic performance.

[0052] To meet the requirements of low noise, the tangential velocity at the tip of the fan blades also tends to decrease. Due to the reduction in hub ratio and tip tangential velocity, the tangential velocity at the root of the fan blades also decreases accordingly.

[0053] In the root region of the blade, due to the reduced tangential velocity, the blade profile design incorporates a significant twist angle to ensure the pressure ratio at the root. However, the blade tenons typically employ a straight tenon structure, lacking a twisting connection. This makes it easy for localized twisting to occur in the leading edge region of the blade when transitioning from the large bend at the blade root to the straight tenon. This localized twisting is detrimental to prototyping and manufacturing processes, and creates high-stress zones, leading to stress concentration problems. Consequently, the localized static strength or fatigue strength may fail to meet requirements, reducing the blade's service life.

[0054] Figures 3A-3C This illustrates a traditional design approach where the fan blade transitions from the elementary blade profile 406 at the hub within the flow channel in the root region to the straight tenon 207 within a narrow radial space at the leading edge, especially at the leading edge. Composite fan blades generally use straight tenons, but designing the transition from the elementary blade profile 404 at the hub within the flow channel to the straight tenon 207 in the root section is challenging. In general modeling, the engine axis 201, the tenon center of gravity 202, and the elementary center of gravity 204 at the hub within the flow channel are placed at the same circumferential position N, such as... Figure 3C As shown, this can easily cause the root extension segment to transition in a compact space, making it easier for the leading edge 203 of the root extension segment to twist, which in turn can lead to local stress concentration.

[0055] Furthermore, due to the upward slope of the fan hub along the flow direction, the trailing edge of the blade extension section is longer than the leading edge. The radial space for the transition from the blade profile within the flow channel to the tenon is more compact than that for the trailing edge. The upward slope of the hub necessitates a longer trailing edge, while the transition of the leading edge is more difficult due to the limited radial space. Therefore, the transition of the leading edge of the extension section is more challenging than that of the trailing edge.

[0056] In view of this, the present invention proposes a swept blade design method, which makes the tenon smoothly transition to the flow channel surface without twisting, thus avoiding the problems of local stress concentration and difficult process forming.

[0057] In the following description, the "bending" of a blade refers to the circumferential deformation of its accumulation line. If the bending direction of the blade is the same as the impeller's rotation direction, it is called forward bending; if the bending direction is opposite to the impeller's rotation direction, it is called backward bending. The "sweep" of a blade refers to the axial deformation of its accumulation line. A forward tilting of the leading or trailing edge of the blade is called forward sweep, and a backward tilting of the leading or trailing edge is called backward sweep. The suction surface of a blade refers to its convex surface, and the pressure surface refers to its concave surface.

[0058] The blade height is the blade height of the flow channel 7 region, that is, the region from the flow channel hub 4 to the blade tip 9. The position of the flow channel hub 4 is 0% blade height, and the position of the blade tip 9 is 100% blade height.

[0059] Figures 4 to 5B The diagram shows a primary blade profile 404 at the hub within the flow channel, whose center of gravity is the primary center of gravity 204 at the hub within the flow channel; above this is a blade profile 408 at 30% blade height, which has a center of gravity 208 at 30% blade height; the diagram also shows a tenon center of gravity 202.

[0060] This method rotates the blades in the region above the tenon center of gravity 202 around the engine axis 201. Specifically, the blades in the region between the tenon center of gravity 202 and the 30% blade height position are rotated around the engine axis toward the blade back, so that the line connecting the elementary-level center of gravity at the flow channel hub and the engine axis and the blade tenon center of gravity forms an angle α.

[0061] Combination Figure 4 and Figure 5B Understanding the concept, the first region I below the tenon's center of gravity remains unchanged. The blade in the second region II, from the tenon's center of gravity 202 to 30% of the blade height, is rotated around the engine axis 201 towards the blade back. This causes the center of gravity 204 of the elementary-level blade profile 404 at the hub within the flow channel to form an angle α with the line connecting the engine axis 201 and the tenon's center of gravity 202. This reduces the circumferential offset of the leading edge region at the root of the blade relative to the tenon, resulting in a more vertical shape. This relatively vertical leading edge of the root section is beneficial for the design of the root section, avoiding local twisting and significantly improving the twisting phenomenon at the leading edge. Since the blade body within the flow channel rotates around the engine axis 201, the aerodynamics of the blade is unaffected.

[0062] Preferably, the line N connecting the center of gravity 204 of the basic element level at the hub in the flow channel and the line connecting the engine axis 201 and the center of gravity 202 of the tenon forms an angle α of 5° to 15°.

[0063] More specifically, the line C connecting the centroids of the blade profiles between the center of gravity 204 at the hub and the center of gravity 208 at 30% blade height is shifted towards the suction surface by a certain angle. Figure 5B The image shows two different blade height positions of the blade centroids: the elementary centroid 204 at the hub inside the flow channel and the blade centroid 206 at 30% blade height. The line C connecting the blade centroids in this region is shifted toward the suction surface.

[0064] By adjusting the centroid of the blade stack in this region to shift towards the suction surface, the leading edge of the blade transitions slowly towards the pressure surface. This reduces the circumferential offset of the leading edge relative to the blade root element level below 30% of the blade height, resulting in a more vertical shape that facilitates connection with the root extension section. This vertical leading edge feature in the end region solves the difficulties in the manufacturing process of blades, especially composite blades, and avoids local twisting in the blade end region. Simultaneously, from 30% of the blade height upwards, the centroid transitions rapidly towards the pressure surface, fulfilling the requirements of aerodynamic blade twisting design.

[0065] Preferably, the line connecting the center of gravity of the basic element at the hub in the flow channel and the center of gravity of the blade at 30% blade height 208 is shifted 0° to 20° toward the suction surface.

[0066] The area from 30% of the leaf height to the leaf tip is Figure 5B The third region III shown can be configured to rotate around the engine axis in the direction of the blade back, or it can be configured to rotate around the engine axis in a direction other than the blade back; there is no limitation on this. For example, in... Figure 5B and Figure 6AIn the embodiment shown, the center of gravity 209 of the leaf shape 409 at the 60% leaf height, which is located at any position above 30% leaf height, such as 60% leaf height, is not rotated.

[0067] By smoothly connecting the leaf regions of each area, a shape is formed. Figure 7 The diagram shows the circumferential accumulation pattern. A represents the leaf basin region, also known as the pressure surface, and B represents the leaf underside region, also known as the suction surface.

[0068] In some embodiments, the method further defines the sweeping relationship of the blade. The region of the blade from the flow channel hub to the blade tip includes a root portion, a middle portion, and a tip portion; the root portion within the blade flow channel is configured to be swept forward, the middle portion to be swept backward, and the tip portion to be swept forward. The boundary between the swept-back portion and the swept-forward portion of the middle portion is located at 30%–60% of the blade height, and the boundary between the swept-forward portion and the swept-back portion of the tip portion is located at 70%–90% of the blade height.

[0069] The forward-sweeping portion bends circumferentially towards the pressure surface, and the backward-sweeping portion bends circumferentially towards the suction surface. Preferably, the chordal sweep and circumferential bend of the blade are matched. The relationship between the bend and the sweep satisfies the equation δ=σ·tanβ, or the calculation deviation from δ=σ·tanβ is less than ±10%, where δ is the bend angle, σ is the sweep angle, and β is the blade's installation angle.

[0070] like Figure 6B The image shows a blade type 409 at 60% of the blade height, with the blade swept back and the tip swept forward. The circumferential curvature matches the sweep, and the sweep approximately satisfies the relationship δ=σ·tanβ, where β is the installation angle of the blade type 409 at 60% of the blade height.

[0071] Through the above design, the blade transitions smoothly from the tenon to the flow channel surface without twisting, avoiding twisting of the blade root section, especially the root section of the straight tenon blade, thus solving the problems of local stress concentration and difficult manufacturing process; within the flow channel area, the leading edge is relatively vertical near the end area, avoiding twisting of the blade end area within the flow channel, thus solving the problems of local stress concentration and difficult manufacturing process in the blade end area within the flow channel; the matching design of bending and sweeping in the upper and middle parts achieves the aerodynamic bending and sweeping design requirements while meeting the structural strength design requirements.

[0072] It should be noted that the use of terms such as "first," "second," and "third" to define the components in the above content is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this application.

[0073] Furthermore, this application uses specific terms to describe embodiments of the application. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0074] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any variations and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for designing swept blades, characterized in that, Includes the following steps: The blades above the tenon center of gravity are rotated around the engine axis. The blades from the tenon center of gravity to the 30% blade height position are rotated around the engine axis toward the blade back, so that the center of gravity of the elementary level at the flow channel hub forms an angle with the line connecting the engine axis and the center of gravity of the blade tenon. 100% blade height is the height from the flow channel hub to the blade tip.

2. The sweeping blade design method as described in claim 1, characterized in that, The line connecting the centers of gravity of each blade type within the area from the center of gravity of the tenon to 30% of the blade height is shifted toward the suction surface.

3. The sweeping blade design method as described in claim 1, characterized in that, The method further includes the following steps: the region of the blade from the flow channel hub to the blade tip includes the root portion, the middle portion, and the tip portion; The leaf root portion within the blade flow channel is configured to sweep forward, the middle portion to sweep backward, and the tip portion to sweep forward. The boundary between the swept-back portion of the middle part of the leaf and the swept-forward portion of the middle part of the leaf is located at 30% to 60% of the leaf height, and the boundary between the swept-forward portion of the leaf tip and the swept-back portion of the middle part of the leaf is located at 70% to 90% of the leaf height.

4. The sweep blade design method as described in claim 2, characterized in that, The relationship between bend and sweep should satisfy the equation δ=σ·tanβ, or the calculation deviation from δ=σ·tanβ should be less than ±10%, where δ is the bend angle, σ is the sweep angle, and β is the blade installation angle.

5. The sweep blade design method as described in claim 1, characterized in that, The center of gravity of the basic element at the hub of the flow channel forms an angle of 5° to 15° with the line connecting the engine axis and the center of gravity of the blade tenon.

6. The sweeping blade design method as described in claim 2, characterized in that, Offset the line connecting the centers of gravity of each blade type within the area from the center of gravity of the tenon to 30% of the blade height towards the suction surface by an angle of 0° to 20°.

7. A sweeping blade, characterized in that, It is designed by the method described in any one of claims 1-6.

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