An active control system for rotor aerodynamic noise

Abstract

The present invention discloses an active control system for rotor aerodynamic noise, relating to the technical field of rotorcraft. The blade comprises a root-cut section, a root section, a middle section, and a tip section, connected in sequence. The end of the root-cut section away from the root section is the center of the hub, and the end of the tip section away from the middle section is the blade tip. The tip section control module is installed in the tip section, and the middle section control module is installed in the middle section. The tip section control module and the middle section control module have the same structure and both include a metal frame, a shape memory alloy tube, and multiple fixing elements. The shape memory alloy tube is located in the middle of the metal frame. Multiple fixing elements are insulated and installed at different positions on the metal frame, and each fixing element is also connected to a different position of the shape memory alloy tube. The metal frame and the shape memory alloy tube both pass through the airfoil section of the blade. The fixing elements can be connected to a power supply and energize the shape memory alloy tube. The present invention can reduce or even avoid the generation of blade-vortex interference noise.

Description

Technical Field

[0001] The present invention relates to the technical field of rotorcraft, and in particular to an active control system for rotor aerodynamic noise. Background Art

[0002] Helicopters offer advantages unmatched by fixed-wing aircraft, such as vertical takeoff and landing and the ability to hover. However, their high vibration and noise levels restrict their use in many situations. Improving the acoustic stealth capabilities of military helicopters could significantly enhance their survivability. In civilian applications, helicopter flights are prohibited over some areas due to the high volume and long-range propagation of aerodynamic noise. Modern helicopter designs, both military and civilian, are increasingly demanding low noise emissions, and the International Civil Aviation Organization's noise standards for helicopters are becoming increasingly stringent. Helicopter noise levels have become a design criterion almost as important as performance, safety, and reliability.

[0003] Helicopter rotor aerodynamic noise can be categorized into three main categories: rotational noise, broadband noise, and impulse noise. BVI noise, a type of impulse noise, is a type of rotor aerodynamic noise that occurs during helicopter flight. Once BVI noise occurs during helicopter operation, it becomes the primary source of rotor aerodynamic noise detected by the human ear. This noise is primarily caused by the interference of vortices drawn by the blades with other blades or with the blades themselves. BVI noise is characterized by high sound pressure levels, long propagation distances, and intense diffusion. Summary of the Invention

[0004] The purpose of the present invention is to provide an active control system for rotor aerodynamic noise to solve the problems existing in the above-mentioned prior art and to weaken or even avoid the generation of blade-vortex interference noise.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides an active control system for rotor aerodynamic noise, comprising a blade, a tip section control module and a middle section control module. The blade comprises a root cut section, a root section, a middle section and a tip section connected in sequence, the end of the root cut section away from the root section being the center of the hub, the end of the tip section away from the middle section being the blade tip, the tip section control module being installed in the tip section, the middle section control module being installed in the middle section, the tip section control module and the middle section control module having the same structure, and both comprising a metal frame, a shape memory alloy tube and a plurality of fixing elements, the shape memory alloy tube being located in the middle of the metal frame, the plurality of fixing elements being insulated and installed at different positions of the metal frame, and each of the fixing elements being further connected to a different position of the shape memory alloy tube, the metal frame and the shape memory alloy tube both passing through the airfoil section of the blade, and the fixing elements being capable of connecting to a power supply and energizing the shape memory alloy tube.

[0007] Preferably, the metal frame is a rectangular frame, and the shape memory alloy tube is arranged parallel to the long side of the metal frame, the paddle is provided with a rectangular long hole at a position corresponding to the long side of the metal frame, and the paddle is provided with a circular long hole at a position corresponding to the shape memory alloy tube.

[0008] Preferably, an outer wall of the shape memory alloy tube is provided with an accommodating groove at a position corresponding to each of the fixing elements.

[0009] Preferably, the fixing elements are in three groups, and the three groups of fixing elements are arranged in sequence along the length direction of the shape memory alloy tube.

[0010] Preferably, each of the fixing elements includes two connecting plates, and one of the connecting plates is located on the upper end surface of the metal frame, and the other connecting plate is located on the lower end surface of the metal frame. Screw holes are provided on both connecting plates, and the positions of the screw holes on the two connecting plates correspond to each other. The connection of the two connecting plates is achieved by passing bolts through the two screw holes arranged upper and lower in sequence and fastening them with nuts. A screw hole is provided at each end of the connecting plate.

[0011] Preferably, two pin holes are provided on the connecting plate, and the positions of the pin holes on different connecting plates correspond one to one, and the two pin holes on the same connecting plate are respectively provided corresponding to the two long sides of the metal frame. The connection between the connecting plate and the metal frame is achieved by passing the positioning pin through the metal frame and the pin holes at corresponding positions on the two connecting plates.

[0012] Preferably, the connecting plate and the metal frame are isolated by an insulating gasket.

[0013] Preferably, the connecting plate arranged near the hub in the tip section control module and the connecting plate arranged near the hub in the middle section control module are both provided with power points for connecting to a power source.

[0014] Preferably, the total length of the blade is R, and the position on the blade corresponding to the hub is point 0, the dividing line between the root cutting section and the root section is point r, the dividing line between the root section and the middle section is the first dividing line, the dividing line between the middle section and the tip section is the second dividing line, and the position on the blade corresponding to the blade tip is point R. The rotor flow field calculation module of the CLORNS software is used to calculate the segmented load of the blade, and then determine the minimum fixed part length L required to maintain structural stability during rotation; if R>L>r, the position of the first dividing line can be selected within the range of [L, R]; if L<r, the position of the first dividing line can be selected within the range of [r, R]; the position of the second dividing line is between the first dividing line and the blade tip, or the second dividing line coincides with the first dividing line.

[0015] Compared with the prior art, the present invention has achieved the following technical effects:

[0016] The rotor aerodynamic noise active control system provided by the present invention can control the blade BVI noise in a targeted manner by installing a tip section control module and a mid-section control module on the blade, thereby reducing the sound pressure level in the key observation area by more than 3dB, reducing the sound propagation range of BVI, and improving the battlefield survivability of military helicopters; in addition, the rotor aerodynamic noise active control system provided by the present invention is active control, which solves the adaptability problem of different flight states existing in the passive control method. At the same time, since the present invention mainly targets BVI noise with a larger sound pressure level, the noise reduction effect of the rotor aerodynamic noise active control system provided by the present invention is more significant than that of the existing rotor active control method. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 Schematic diagram of blade twisting partition in the present invention;

[0019] Figure 2 Schematic diagram of the external structure of the tip section of the present invention;

[0020] Figure 3 Schematic diagram of the internal structure of the tip section of the present invention;

[0021] Figure 4 Schematic diagram of the external structure of the middle section of the present invention;

[0022] Figure 5It is a structural diagram of the tip section control module or the middle section control module of the present invention;

[0023] Figure 6 A top view of the connecting plate of the present invention;

[0024] Figure 7 is a side view of the shape memory alloy tube of the present invention;

[0025] Figure 8 Schematic diagram of the wing-shaped structural parameters of the tip section or the middle section of the present invention;

[0026] Figure 9 Schematic diagram of parameters of the long side of the metal frame and the insulating gasket in the present invention;

[0027] Figure 10 A schematic diagram of the torsional state of the rotor aerodynamic noise active control system provided by the present invention before and after power is applied;

[0028] Figure 11 This is a schematic diagram of the noise propagation direction of rotorcraft;

[0029] In the figure: 1-root cut section, 2-root section, 3-middle section, 4-tip section, 5-hub, 6-tip, 7-airfoil section, 8-rectangular long hole, 9-circular long hole, 10-metal frame, 11-fixing element, 12-bolt, 13-nut, 14-shape memory alloy tube, 15-power point, 16-insulating gasket, 17-connecting plate, 18-screw hole, 19-pin hole. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] The purpose of the present invention is to provide an active control system for rotor aerodynamic noise to solve the problems existing in the prior art and to weaken or even avoid the generation of blade-vortex interference noise.

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Example 1

[0034] like Figures 1-11As shown, this embodiment provides an active control system for rotor aerodynamic noise, including a blade, a tip section control module and a middle section control module. The blade includes a root section 1, a root section 2, a middle section 3 and a tip section 4 connected in sequence. The segmented design can reduce the difficulty of processing while ensuring structural strength. The end of the root section 1 away from the root section 2 is the center of the hub 5, and the end of the tip section 4 away from the middle section 3 is the blade tip 6. The tip section control module is installed in the tip section 4, and the middle section control module is installed in the middle section 3. The blade BVI noise can be controlled in a targeted manner, so that the sound pressure level in the key observation area is reduced by more than 3dB, and the sound propagation range of BVI is reduced, thereby improving the battlefield survivability of military helicopters; the tip section control module and the middle section control module have the same structure and both include a metal frame 10, a shape memory alloy tube 14 and a plurality of fixing elements 11. By embedding a shape memory alloy tube in the blade skin, a The mechanism constructed by 14, when powered on, the deformation of the shape memory alloy tube 14 adjusts the negative torsion of the blade, changes the propagation direction of the eddy current, weakens or even avoids the generation of blade-vortex interference noise, the shape memory alloy tube 14 is located in the middle of the metal frame 10, and multiple fixing elements 11 are insulated and installed at different positions of the metal frame 10, and each fixing element 11 is also connected to a different position of the shape memory alloy tube 14, the metal frame 10 and the shape memory alloy tube 14 both pass through the airfoil section 7 of the blade, the fixing element 11 can be connected to the power supply and energize the shape memory alloy tube 14, and the active control method is adopted to solve the adaptability problem of different flight states existing in the passive control method. At the same time, since this embodiment is mainly aimed at BVI noise with a larger sound pressure level, the noise reduction effect of the rotor aerodynamic noise active control system provided by this embodiment is more significant than the existing rotor active control method.

[0035] Specifically, the metal frame 10 is a rectangular frame, and the shape memory alloy tube 14 is arranged parallel to the long side of the metal frame 10. The blade has a rectangular slot 8 at a position corresponding to the long side of the metal frame 10, and a circular slot 9 at a position corresponding to the shape memory alloy tube 14. Assuming the airfoil chord length is C and the airfoil thickness is h, the center of the circular slot 9 and the midline of the rectangular slot 8 must both lie on the line connecting the leading and trailing edges of the airfoil. Furthermore, the center of the circle must be at x*C, which is the specified collective axis of the helicopter rotor. d1 is the thickness of the metal frame 10, and d2 is the combined thickness of the metal frame 10 and the two insulating gaskets 16 arranged above and below. The width of the processed shape memory alloy tube 14 must be equal to d2. The widths of the two rectangular slots 8 should both be equal to d1 and located on either side of the circular slot 9.

[0036] The outer wall of the shape memory alloy tube 14 is provided with accommodating grooves at positions corresponding to the fixing elements 11 .

[0037] There are three groups of fixing elements 11, which are arranged in sequence along the length direction of the shape memory alloy tube 14. The fixing elements 11 are used to amplify the deformation of the shape memory alloy tube 14 and drive the metal frame 10 to deform, and the metal frame 10 drives the airfoil section 7 to rotate.

[0038] Each fixing element 11 includes two connecting plates 17, one of which is located on the upper end surface of the metal frame 10, and the other is located on the lower end surface of the metal frame 10. Screw holes 18 are provided on both connecting plates 17, and the positions of the screw holes 18 on the two connecting plates 17 correspond. The bolts 12 pass through the two screw holes 18 arranged in an upper and lower manner in sequence and are fastened by nuts 13 to achieve the connection of the two connecting plates 17. A screw hole 18 is provided at each end of the connecting plate 17.

[0039] The width of the connecting plate 17 is limited by the thickness and width of the airfoil, and it is necessary to ensure that the upper and lower ends of the bolt 12 do not contact the skin and have enough space for movement during rotation.

[0040] The connecting plate 17 is isolated from the metal frame 10 by an insulating gasket 16 .

[0041] Two pin holes 19 are also provided on the connecting plate 17. The positions of the pin holes 19 on different connecting plates 17 correspond one to one, and the two pin holes 19 on the same connecting plate 17 are respectively provided corresponding to the two long sides of the metal frame 10. The connection between the connecting plate 17 and the metal frame 10 is achieved by passing the positioning pin through the metal frame 10 and the corresponding pin holes 19 on the two connecting plates 17. At the same time, it can also play the role of fixing the insulating gasket 16, so that the metal frame 10 is not electrified.

[0042] A connection plate 17 provided near the hub 5 in the tip section control module and a connection plate 17 provided near the hub 5 in the middle section control module are both provided with power points 15 for connecting to a power source, which facilitates wiring.

[0043] The total length of the blade is R, and the position on the blade corresponding to the hub 5 is point 0, the dividing line between the root cut section 1 and the root section 2 is point r, the dividing line between the root section 2 and the middle section 3 is the first dividing line, the dividing line between the middle section 3 and the tip section 4 is the second dividing line, and the position on the blade corresponding to the blade tip 6 is point R. The rotor flow field calculation module of the CLORNS software is used to calculate the segmented load of the blade, and then determine the minimum fixed part length L required to maintain structural stability during high-speed rotation. The position of the first dividing line is determined by the load calculation and size constraint: if R>L>r, the position of the first dividing line can be selected within the range of [L, R]; if L<r, the position of the first dividing line can be selected within the range of [r, R]; the position of the second dividing line is between the first dividing line and the blade tip 6, or the second dividing line coincides with the first dividing line. Among them, the minimum fixed part refers to the part with a length of L, starting from the dividing line between the root cut section 1 and the root section 2, extending in the direction of the blade tip 6. Since the blade will be subjected to radial centrifugal force and tension perpendicular to the disc plane during actual operation, the radial force of the non-fixed part (i.e., the RL part) will be concentrated here. Based on this, it is necessary to consider whether the load introduced by the length of the non-fixed part of the blade (i.e., the RL part) can be borne by the blade. When other parameters remain unchanged, the larger the (RL), the greater the radial centrifugal force, and the tension perpendicular to the disc plane (i.e., lift) generates shear force and bending moment here; when other parameters remain unchanged, the larger the (RL), the greater the bending moment.

[0044] The difference between the tip section control module and the middle section control module is only the size of the metal frame 10 and the degree of deformation of the shape memory alloy tube 14:

[0045] The material selection of the metal frame 10 is subject to two conditions. First, the Young's modulus of the metal material must be greater than that of the skin material to ensure that it can drive the airfoil section 7 to deform. Second, the total weight of the metal material should not exceed the supportable weight of the airfoil section 7. In principle, any material that meets the above two conditions can be selected; the length and width of the metal frame 10 are determined by the size of the rotor; the external width of the metal frame 10 should be smaller than the width of the installation and fixing structure, and the internal width should be larger than the diameter of the shape memory alloy tube 14. The external length ensures that it can cover each airfoil section 7 that needs to rotate and does not exceed the length of the segment. For example, for a structure installed in the tip section 4 of the blade, the external length of the metal frame 10 should not be greater than the packaging length of the tip section 4 of the blade, and the internal length should not be less than the length of the shape memory alloy tube 14.

[0046] The undercut serves to secure the blades; it lacks the blade's outer shape, eliminating the need for an embedded control module. Furthermore, because the blade root bears significant centrifugal force, it serves to secure the entire structure. In this embodiment, to ensure structural strength, a control module is not embedded within the root section 2. The middle section 3 acts as a transition, bearing only minor deformations, while the tip section 4 bears the bulk of the deformation. This segmented approach helps control costs, as repeated, large-scale deformations can easily lead to metal fatigue, requiring frequent inspection, maintenance, and replacement of the skin and other metals involved in deformation.

[0047] Taking the tip section 4 of the blade as an example, the tip section control module is explained. Figure 3 The airfoil section 7 in the figure is the airfoil-shaped support structure (i.e., airfoil section 7) seen after the blade is cut along the chord direction. The material, support method, and distribution distance of this support structure are determined after the helicopter model is selected. Taking the Z-10 helicopter as an example, when it is determined that this solution will be used on the Z-10 rotor, the distribution distance, support method, and support material inside the blade are all determined to be the support material and support structure of the Z-10.

[0048] The method of the rotor aerodynamic noise active control system in this embodiment to control rotor noise is as follows:

[0049] Step 1: Determine whether the current operating state of the helicopter requires noise control. When determining the helicopter model and flight information, use the aerodynamic noise solution module of the CLORNS software to evaluate the rotor aerodynamic noise state. If BVI noise occurs, the rotor aerodynamic noise active control system of this embodiment can be used to control noise during flight.

[0050] Step 2: When it is determined that the helicopter needs to be noise-controlled in this state, the rotor aerodynamic noise active control system is activated and power is supplied to the power point 15. After power is supplied, the shape memory alloy tube 14 begins to twist. At the same time, the deformation of the shape memory alloy tube 14 is amplified by the fixing element 11, causing the metal frame 10 to deform. The metal frame 10 drives the airfoil structure to rotate. Figure 10 As shown, at this time, the outer skin of the blade is deformed and negative torsion is achieved.

[0051] Step 3: After the rotor aerodynamic noise active control system in this embodiment is reduced to a limit value, this state is maintained unchanged as the helicopter operates.

[0052] Step 4: When the helicopter no longer needs noise control, the power is turned off, and the rotor aerodynamic noise active control system in this embodiment runs in reverse to restore the rotor to a normal state.

[0053] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. An active control system for rotor aerodynamic noise, characterized by: The blade comprises a root-cut section, a root section, a middle section and a tip section, wherein the end of the root-cut section away from the root section is the center of the hub, and the end of the tip section away from the middle section is the blade tip. The tip section control module is installed in the tip section, and the middle section control module is installed in the middle section. The tip section control module and the middle section control module have the same structure and both comprise a metal frame, a shape memory alloy tube and a plurality of fixing elements. The shape memory alloy tube is located in the middle of the metal frame. The plurality of fixing elements are insulated and installed at different positions of the metal frame, and each fixing element is also connected to a different position of the shape memory alloy tube. The metal frame and the shape memory alloy tube both pass through the airfoil section of the blade. The fixing element can be connected to a power supply and energize the shape memory alloy tube, causing the shape memory alloy tube to begin to twist. At the same time, the deformation of the shape memory alloy tube is amplified by the fixing element, causing the metal frame to deform and the metal frame to drive the airfoil structure to rotate.

2. The active rotor aerodynamic noise control system according to claim 1, characterized in that: The metal frame is a rectangular frame, and the shape memory alloy tube is arranged parallel to the long side of the metal frame. The paddle is provided with a rectangular long hole at a position corresponding to the long side of the metal frame, and the paddle is provided with a circular long hole at a position corresponding to the shape memory alloy tube.

3. The active rotor aerodynamic noise control system according to claim 2, characterized in that: The outer wall of the shape memory alloy tube is provided with accommodating grooves corresponding to the positions of the fixing elements.

4. The active rotor aerodynamic noise control system according to claim 2, characterized in that: There are three groups of fixing elements, and the three groups of fixing elements are arranged in sequence along the length direction of the shape memory alloy tube.

5. The active rotor aerodynamic noise control system according to claim 4, characterized in that: Each of the fixing elements includes two connecting plates, and one of the connecting plates is located on the upper end surface of the metal frame, and the other connecting plate is located on the lower end surface of the metal frame. Screw holes are provided on both connecting plates, and the positions of the screw holes on the two connecting plates correspond. The connection of the two connecting plates is achieved by passing bolts through the two screw holes arranged up and down in sequence and fastening them with nuts. A screw hole is provided at each end of the connecting plate.

6. The active rotor aerodynamic noise control system according to claim 5, characterized in that: Two pin holes are also provided on the connecting plate. The positions of the pin holes on different connecting plates correspond one to one, and the two pin holes on the same connecting plate are respectively arranged corresponding to the two long sides of the metal frame. The connection between the connecting plate and the metal frame is achieved by passing the positioning pin through the metal frame and the corresponding pin holes on the two connecting plates.

7. The active rotor aerodynamic noise control system according to claim 6, characterized in that: The connecting plate and the metal frame are isolated by an insulating gasket.

8. The active rotor aerodynamic noise control system according to claim 5, characterized in that: The connecting plate arranged near the hub in the tip section control module and the connecting plate arranged near the hub in the middle section control module are both provided with power points for connecting to a power source.

9. The active rotor aerodynamic noise control system according to claim 1, characterized in that: The total length of the blade is R, and the position on the blade corresponding to the hub is point 0, the dividing line between the root cut section and the root section is point r, the dividing line between the root section and the middle section is the first dividing line, the dividing line between the middle section and the tip section is the second dividing line, and the position on the blade corresponding to the blade tip is point R. The rotor flow field calculation module of the CLORNS software is used to calculate the segmented load of the blade, and then determine the minimum length L of the fixed part required to maintain structural stability during rotation; if R>L>r, the position of the first dividing line can be selected within the range of [L, R]; if L<r, the position of the first dividing line can be selected within the range of [r, R]; the position of the second dividing line is between the first dividing line and the blade tip, or the second dividing line coincides with the first dividing line.

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