A connection structure and method for variable pitch wind tunnel blades and hub

Abstract

The present invention relates to a connection structure between a variable pitch wind tunnel blade and a hub, comprising a flange, a carbon beam, a left preform, a right preform, a foam core and a wedge; a through channel is opened in the center of the flange, the channel has opposing channel walls, one end of the channel is a straight channel, and the other end is an outward expansion channel from the inside to the outside; the equal thickness parts and the carbon beam of the left preform and the right preform are squeezed by the straight channel of the wedge and the flange, and the thickened parts and the carbon beam of the left preform and the right preform are squeezed by the outward expansion channel of the wedge and the flange, forming a continuous fiber extrusion structure. The carbon beam of the present invention is continuous inside the flange, ensuring fiber continuity, and fully exerting the material characteristics of carbon fiber with high specific strength and specific stiffness.

Description

Technical Field

[0001] The invention relates to the field of wind tunnel blade connection structure design, and in particular to a connection structure and method for a variable pitch wind tunnel blade and a hub. Background Art

[0002] As the country's economic strength increases, it is striving to develop into high-tech fields such as aviation and aerospace. The development of various types of aerospace and aviation vehicles requires a large amount of wind tunnel testing. Therefore, low-speed, transonic, supersonic, and hypersonic wind tunnels have developed rapidly. So far, my country already has low-speed, high-speed, ultra-high-speed, shock wave, arc and other wind tunnels, but there is still a blank for continuous transonic wind tunnels. Continuous transonic wind tunnels can realize the functions of quickly establishing supersonic flow fields, continuously and accurately controlling Mach numbers, and replacing test pieces when the compressor is not completely stopped.

[0003] A continuous transonic wind tunnel requires the blades to adjust their angles without stopping the machine. The blades are driven to rotate together through a pitch shaft to achieve adjustable pitch of the moving blades. It must also meet the performance requirements of different working conditions. Due to the limitations of the hub, pitch shaft and working conditions, there are huge challenges in the design of the pitch structure and carbon fiber blade structure.

[0004] Inquiring about the overall structural data of similar wind tunnel fans at home and abroad, the connection methods of the main blades and hubs of foreign wind tunnels include the latch structure and the carbon fiber winding method. The latch structure connection destroys the continuity of the carbon fiber, and the carbon fiber winding method is easy to damage the exposed carbon fiber during installation and maintenance; the carbon fiber tow (bearing beam) of the load-bearing beam and the blade part is not parallel to the direction of centrifugal force, which will cause the carbon fiber cloth layers to delaminate during operation, reducing the blade strength. The above two structures cannot give full play to the excellent characteristics of carbon fiber materials. Summary of the invention

[0005] Purpose of the invention: To provide a solution to the above-mentioned connection problem between the blade and the hub, and to overcome the inability to give full play to the excellent characteristics of carbon fiber materials, while solving the problem of parts detachment caused by inconsistent thermal expansion coefficients of metal materials and carbon fiber composite materials under high temperature conditions, and to provide a connection structure, in which the blade is connected to the pitch shaft through a flange, and the carbon beam extends from the tip of the blade to the inside of the aluminum alloy flange at the root of the blade, and the wedge block squeezes the carbon beam and the inner cavity of the aluminum flange to form a tight and effective connection structure.

[0006] Technical solution: Provide a connection structure between a variable pitch wind tunnel blade and a hub, including a flange, a carbon beam, a left preform, a right preform, a foam core and a wedge;

[0007] The left preform and the right preform are rigid plates, and one end of the rigid plate is a uniform thickness portion, and the other end is a thickened portion with gradually increasing thickness from the inside to the outside;

[0008] A through channel is opened in the center of the flange, the channel has opposing channel walls, one end of the channel is a straight channel, and the other end is an outward expansion channel from the inside to the outside;

[0009] The carbon beam is formed by solidifying a carbon fiber prepreg sandwiched with a foam core, and the end of the carbon beam is formed by first overlapping the carbon fiber prepreg and then concavely forming two protrusions, and the two protrusions both have an inner cavity, the left preform and the right preform are respectively sandwiched in the two inner cavities, and the two protrusions are both inserted into the channel of the flange, and the wedge is inserted between the two protrusions;

[0010] The equal thickness parts and carbon beams of the left and right preforms are squeezed by the straight channels of the wedges and flanges, and the thickened parts and carbon beams of the left and right preforms are squeezed by the outward expansion channels of the wedges and flanges to form a continuous fiber extrusion structure.

[0011] Furthermore, the outward expansion angle of the outward expansion channel is not higher than the thickening angle of the thickened portion.

[0012] Furthermore, the outward expansion angle of the outward expansion channel is 10° to 25°.

[0013] Furthermore, the thickening angle of the thickened portion is 10° to 25°.

[0014] Furthermore, an outward expansion angle of the outward expansion channel is smaller than a thickening angle of the thickened portion.

[0015] Furthermore, the left preform, the right preform, the two protruding wedges and the wedges are all blade-shaped and adapted to the blade shape.

[0016] Furthermore, the lengths of the cross-sectional contour lines of the wedge blocks cut by a plane perpendicular to the center arc line of the blade are all equal.

[0017] Furthermore, the left preform and the right preform are also provided with limiting protrusions, and the limiting protrusions are locked with the flange to prevent the preform from slipping out through the straight channel of the flange.

[0018] A method for connecting a variable pitch wind tunnel blade to a hub is also provided, and the steps are as follows:

[0019] Step 1, laying the carbon beam and foam inside the mold, and laying them in the order of non-working surface carbon beam prepreg, foam, and working surface carbon beam prepreg. The non-working surface carbon beam prepreg and the working surface carbon beam prepreg are integral carbon fiber prepregs, and a continuous U-shaped bend is reserved in the blade root direction. There is no foam core in the U-shaped bend. The upper and lower molds are molded together, and the prepreg U-shaped bend is exposed outside the mold;

[0020] Step 2: The above-mentioned prepreg U-shaped bend passes through the straight channel and the outward expansion channel of the flange in sequence, and the flange is fixed on the mold, and the left and right preforms are inserted into the prepreg U-shaped bend and into the flange at the same time;

[0021] Step 3, recessing the part of the prepreg U-bend that passes through the flange between the left and right preforms in the flange to form the two protruding parts;

[0022] Step 4, inserting a wedge block between the two protruding parts, so that the wedge block, the prepreg, the left and right preforms and the flange are squeezed into one body;

[0023] Step 5: Heat and pressurize the mold, and after curing, obtain a structure in which the blade and the hub are connected as one.

[0024] Technical effects: 1. The carbon beam is continuous inside the flange, ensuring the continuity of the fiber, and fully utilizing the material properties of carbon fiber with high specific strength and specific stiffness;

[0025] 2. The blade root uses wedges and flanges to extrude the carbon beam to form a sandwich structure. When the working temperature changes, the structure will not become loose or the flange and carbon beam will not be pushed apart due to the inconsistent thermal expansion coefficients of metal and carbon fiber.

[0026] 3. Due to the expansion angle inside the flange, the blade root structure will become tighter and tighter under the action of centrifugal force, which can improve the structural performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the present invention;

[0028] Figure 2 is a cross-sectional view of the present invention;

[0029] Figure 3 This is a schematic diagram of the structure after the flange and carbon beam are installed;

[0030] Figure 4 It is a schematic diagram of the structure of the flange;

[0031] Figure 5 is a cross-sectional view of the flange;

[0032] Figure 6 It is the structural schematic diagram of the carbon beam;

[0033] Figure 7 It is the main view of the carbon beam;

[0034] Figure 8 is a schematic diagram of the structure of the wedge;

[0035] Fig. 9 is a cross-sectional view of the wedge;

[0036] Fig.10It is a structural schematic diagram of one of the left and right preforms;

[0037] Fig.11 It is a schematic diagram of the structure after the left and right prefabricated bodies, flanges and carbon beams are installed;

[0038] Fig.12 It is a schematic diagram of the structure of an inverted flange;

[0039] Among them: 1-flange, 2-carbon beam, 3-left preform, 4-right preform, 5-foam core, 6-wedge, 7-equal thickness part, 8-thickening part, 9-straight channel, 10-outward expansion channel, 11-center arc line, 12-section, 13-section contour line, 14-protrusion, 15-inner cavity. DETAILED DESCRIPTION

[0040] In conjunction with the accompanying drawings, a connection structure between a variable pitch wind tunnel blade and a hub is specifically provided, comprising a flange, a carbon beam, a left preform, a right preform, a foam core and a wedge;

[0041] The left preform and the right preform are rigid plates, and one end of the rigid plate is a uniform thickness portion, and the other end is a thickened portion with gradually increasing thickness from the inside to the outside;

[0042] A through channel is opened in the center of the flange, the channel has opposing channel walls, one end of the channel is a straight channel, and the other end is an outward expansion channel from the inside to the outside;

[0043] The carbon beam is formed by solidifying a carbon fiber prepreg sandwiched with a foam core, and the end of the carbon beam is formed by first overlapping the carbon fiber prepreg and then concavely forming two protrusions, and the two protrusions both have an inner cavity, the left preform and the right preform are respectively sandwiched in the two inner cavities, and the two protrusions are both inserted into the channel of the flange, and the wedge is inserted between the two protrusions;

[0044] The equal thickness parts and carbon beams of the left and right preforms are squeezed by the straight channels of the wedges and flanges, and the thickened parts and carbon beams of the left and right preforms are squeezed by the outward expansion channels of the wedges and flanges to form a continuous fiber extrusion structure.

[0045] Furthermore, the outward expansion angle of the outward expansion channel is not higher than the thickening angle of the thickened portion.

[0046] The outward expansion angle of the outward expansion channel is 10°.

[0047] The thickening angle of the thickened portion is 12°.

[0048] The left preform, the right preform, the two protruding wedges and the wedges are all leaf-shaped and adapted to the leaf shape of the blade.

[0049] The lengths of the cross-sectional contour lines of the wedge blocks cut by a plane perpendicular to the center arc line of the blade are all equal.

[0050] A method for connecting a variable pitch wind tunnel blade to a hub is also provided, and the steps are as follows:

[0051] Step 1, laying the carbon beam and foam inside the mold, and laying them in the order of non-working surface carbon beam prepreg, foam, and working surface carbon beam prepreg. The non-working surface carbon beam prepreg and the working surface carbon beam prepreg are integral carbon fiber prepregs, and a continuous U-shaped bend is reserved in the blade root direction. There is no foam core in the U-shaped bend. The upper and lower molds are molded together, and the prepreg U-shaped bend is exposed outside the mold;

[0052] Step 2: The above-mentioned prepreg U-shaped bend passes through the straight channel and the outward expansion channel of the flange in sequence, and the flange is fixed on the mold, and the left and right preforms are inserted into the prepreg U-shaped bend and into the flange at the same time;

[0053] Step 3, recessing the part of the prepreg U-bend that passes through the flange between the left and right preforms in the flange to form the two protruding parts;

[0054] Step 4, inserting a wedge block between the two protruding parts, so that the wedge block, the prepreg, the left and right preforms and the flange are squeezed into one body;

[0055] Step 5: Heat and pressurize the mold, and after curing, obtain a structure in which the blade and the hub are connected as one.

Claims

1. A connection structure between a variable pitch wind tunnel blade and a hub, characterized in that: It includes flange, carbon beam, left preform, right preform, foam core and wedge; The left preform and the right preform are rigid plates, and one end of the rigid plate is a uniform thickness portion, and the other end is a thickened portion with gradually increasing thickness from the inside to the outside; A through channel is opened in the center of the flange, the channel has opposing channel walls, one end of the channel is a straight channel, and the other end is an outward expansion channel from the inside to the outside; The carbon beam is formed by solidifying a carbon fiber prepreg sandwiched with a foam core, and the end of the carbon beam is formed by first overlapping the carbon fiber prepreg and then concavely forming two protrusions, and the two protrusions both have an inner cavity, the left preform and the right preform are respectively sandwiched in the two inner cavities, and the two protrusions are both inserted into the channel of the flange, and the wedge is inserted between the two protrusions; The equal thickness parts and carbon beams of the left and right preforms are squeezed by the straight channels of the wedges and flanges, and the thickened parts and carbon beams of the left and right preforms are squeezed by the outward expansion channels of the wedges and flanges to form a continuous fiber extrusion structure; The outward expansion angle of the outward expansion channel is not higher than the thickening angle of the thickened portion; The left preform, the right preform, the two protruding wedges and the wedges are all leaf-shaped and adapted to the leaf shape of the blade; The lengths of the cross-sectional contour lines of the wedge blocks cut by a plane perpendicular to the center arc line of the blade are all equal; The left preform and the right preform are further provided with limiting protrusions, and the limiting protrusions are locked with the flange to prevent the preform from passing through the straight channel of the flange and escaping.

2. The connection structure between a variable pitch wind tunnel blade and a hub according to claim 1, characterized in that: The outward expansion angle of the outward expansion channel is 10° to 25°.

3. A variable pitch wind tunnel blade and hub connection structure as claimed in claim 1 or 2, characterized in that: The thickening angle of the thickened portion is 10° to 25°.

4. A variable pitch wind tunnel blade and hub connection structure as claimed in claim 1 or 2, characterized in that: The outward expansion angle of the outward expansion channel is smaller than the thickening angle of the thickened portion.

5. A method for connecting the connection structure according to any one of claims 1 to 4, comprising the following steps: Step 1, laying the carbon beam and foam inside the mold, and laying them in the order of non-working surface carbon beam prepreg, foam, and working surface carbon beam prepreg. The non-working surface carbon beam prepreg and the working surface carbon beam prepreg are integral carbon fiber prepregs, and a continuous U-shaped bend is reserved in the blade root direction. There is no foam core in the U-shaped bend. The upper and lower molds are molded together, and the U-shaped bend is exposed outside the mold; Step 2: The U-shaped bend is passed through the straight channel and the outward expansion channel of the flange in sequence, and the flange is fixed on the mold, and the left and right preforms are inserted into the U-shaped bend and into the flange at the same time; Step 3, recessing the portion of the U-shaped bend protruding from the flange between the left and right preforms in the flange to form the two protruding portions; Step 4, inserting a wedge block between the two protruding parts, so that the wedge block, the prepreg, the left and right preforms and the flange are squeezed into one body; Step 5: Heat and pressurize the mold, and after curing, obtain a structure in which the blade and the hub are connected as one.

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