Method and device for suppressing helicopter high-speed pulse noise, and helicopter

Abstract

The present invention discloses a method, device and helicopter for suppressing high-speed pulse noise of a helicopter, and relates to the technical field of helicopter noise control. At least one synthetic jet actuator is embedded in the upper surface of the blade tip, and the synthetic jet actuator can generate an upward jet, and the jet can interact with the main flow of the blade to form an aerodynamic shape. When high-speed pulse noise is generated, the shock wave on the blade tip is a noise shock wave. The opening state and control parameters of the synthetic jet actuator are adjusted to change the shape of the aerodynamic shape to weaken the intensity of the noise shock wave. The method, device and helicopter for suppressing high-speed pulse noise of a helicopter can effectively suppress the high-speed pulse noise of the rotor of the helicopter in various flight states, and have good applicability.

Description

Technical Field

[0001] The present invention relates to the technical field of helicopter noise control, and in particular to a method and device for suppressing helicopter high-speed pulse noise, and a helicopter. Background Art

[0002] Helicopters have advantages such as vertical take-off and landing, high maneuverability and hovering in the air, making them widely used in both military and civilian fields. However, one of the main disadvantages of helicopters is their high noise. In the civilian field, helicopter noise will seriously affect the comfort of pilots and passengers, thus directly limiting its scope of use; in the military field, noise will affect the stealth performance of helicopters and greatly reduce the survivability of helicopters. Therefore, how to reduce noise has become an increasingly important issue in helicopter design, and conducting relevant research has important economic benefits and military value.

[0003] Rotor aerodynamic noise is the main noise source of helicopters. According to the noise characteristics, it can be divided into thickness noise, load noise, high-speed pulse noise, blade-vortex interference noise and broadband noise. When the helicopter flies forward at high speed, the forward rotor blade is partially in transonic flow, and shock waves will be generated at the blade tip. When the blade tip speed increases to a certain value, the shock wave on the blade surface will diffuse to the supersonic region outside the blade tip, which is called the "delocalization" phenomenon. The shock wave interference will propagate to the far field, thereby generating high-speed pulse noise. Once a helicopter generates high-speed pulse noise, it will greatly increase the overall noise level of the helicopter.

[0004] At present, there are relatively few methods for suppressing high-speed pulse noise of helicopter rotors. The most common methods include optimizing the aerodynamic shape of the blade tip, solid bulge control and groove control. Optimizing the aerodynamic shape of the blade tip, such as using forward sweep, backward sweep, and tapering to change the blade tip shape to delay the generation of shock waves and weaken the shock wave intensity, thereby reducing the high-speed pulse noise of the rotor. The solid bulge suppression method is to add a bulge to the rotor tip to control the shock wave, change the strong shock wave at the rotor tip into a λ wave or several weak oblique shock waves, and weaken the shock wave intensity, thereby achieving the effect of suppressing high-speed pulse noise. The groove control method is to set a groove at the rotor tip, and cover the groove with a porous plate, so that the airflow after the shock wave can flow to the wave front through the groove, automatically adjust the pressure before and after the shock wave, reduce the shock wave intensity, and play a role in reducing high-speed pulse noise. However, this method introduces boundary layer backflow, and the viscous resistance is greatly increased. In most cases, the viscosity loss brought by this method is greater than or equal to the benefit of wave resistance reduction. The above methods change the shape of the rotor to a certain extent, which will affect the aerodynamic performance of the rotor, and they are all passive control methods, which only have a good control effect under the design state. When the actual situation deviates from its design state, the control effect is poor. Another way to suppress the high-speed pulse noise of the rotor is to reduce the rotor speed. However, reducing the speed may resonate with the structural frequency of the helicopter, which requires a series of measures to avoid the resonance problem in the helicopter structural design and rotor speed control, thereby greatly increasing the difficulty of helicopter design. Therefore, the technology of suppressing high-speed pulse noise of the rotor is not yet mature, and a simpler and more effective suppression method still needs to be developed.

[0005] Glezer A proposed a flow control method for synthetic jets (Glezer A, Amitay M. Synthetic jets [J]. Annual Review of Fluid Mechanics, 2003, 34 (1): 503-529). Studies have shown that the interaction between synthetic jets and lateral mainstreams will change the flow direction of the airflow, which is equivalent to changing the shape of an object and achieving a virtual aerodynamic shape. Therefore, it can be predicted that if synthetic jets are reasonably applied to the surface of the rotor tip, a "virtual bulge" can be formed on the surface of the rotor tip, thereby achieving the effect of weakening the tip shock wave and suppressing the high-speed pulse noise of the rotor. Therefore, there is great potential in using synthetic jets to suppress the high-speed pulse noise of the rotor. Summary of the invention

[0006] The present invention provides a method and device for suppressing high-speed pulse noise of a helicopter, and a helicopter, so as to solve the problems existing in the prior art, and can effectively suppress the high-speed pulse noise of a helicopter rotor in various flight states, and has good applicability.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] The present invention provides a method for suppressing high-speed pulse noise of a helicopter. At least one synthetic jet actuator is embedded in the upper surface of a blade tip. The synthetic jet actuator can generate an upward jet. The jet can interact with the main flow of the blade to form an aerodynamic shape. When high-speed pulse noise is generated, the shock wave on the blade tip is a noise shock wave. The opening state and control parameters of the synthetic jet actuator are adjusted to change the shape of the aerodynamic shape to weaken the intensity of the noise shock wave.

[0009] Furthermore, the synthetic jet actuator is arranged in a noise shock wave generating area, and the noise shock wave generating area is an area composed of positions where each noise shock wave acts on the blade.

[0010] Furthermore, the position information of the noise shock wave acting on the blade is obtained by means of computational fluid dynamics.

[0011] Furthermore, the position information of the noise shock wave acting on the blade is obtained by a wind tunnel test method.

[0012] Furthermore, the position information of the noise shock wave acting on the blade includes the maximum distance, the minimum distance and the distance from the front edge of the blade of each noise shock wave.

[0013] Furthermore, the control parameters of the synthetic jet actuator include an excitation frequency and an outlet momentum coefficient.

[0014] Furthermore, during the test phase, under different flight states of the helicopter when high-speed pulse noise can be generated, the opening state and control parameters of each of the synthetic jet actuators are adjusted to obtain the opening state and control parameters of the synthetic jet actuator when the high-speed pulse noise is reduced for the first time under various flight states of the helicopter. At this time, the opening state and control parameters of each of the synthetic jet actuators are respectively the first opening state and the first control parameters; when the helicopter is actually flying, each of the synthetic jet actuators is adjusted to the first opening state and the first control parameters.

[0015] Furthermore, when the helicopter is actually flying, it is first determined whether the flight state of the helicopter is within the condition range for generating the high-speed pulse noise. If so, each of the synthetic jet actuators is adjusted to the first opening state and the first control parameter.

[0016] The present invention also provides a device for suppressing high-speed pulse noise of a helicopter, comprising at least one synthetic jet actuator embedded in the upper surface of the blade tip, wherein the synthetic jet actuator can generate an upward jet, and the jet can interact with the mainstream of the blade to form an aerodynamic shape. Adjusting the opening state and control parameters of the synthetic jet actuator can change the shape of the aerodynamic shape to weaken the intensity of the shock wave when high-speed pulse noise is generated.

[0017] The present invention also provides a helicopter, comprising a fuselage, a rotor and the above-mentioned device for suppressing high-speed pulse noise of the helicopter, wherein the rotor is rotatably connected to the fuselage, and the device for suppressing high-speed pulse noise of the helicopter is embedded in the upper surface of the blade tip.

[0018] Compared with the prior art, the present invention has achieved the following technical effects:

[0019] The present invention provides a method, device and helicopter for suppressing high-speed pulse noise of a helicopter. Each synthetic jet actuator embedded in the upper surface of the blade tip can generate an upward jet, and the jet interacts with the main flow of the blade to form an aerodynamic shape, which is equivalent to a "virtual bulge". When the helicopter generates high-speed pulse noise during high-speed flight, the opening state and control parameters of each synthetic jet actuator are adjusted to adjust the state of the "virtual bulge", and the "virtual bulge" can weaken the intensity of the noise shock wave and reduce the "delocalization" phenomenon of the rotor blade tip shock wave, thereby achieving the effect of suppressing the high-speed pulse noise of the helicopter. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. 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 creative work.

[0021] Description of reference numerals:

[0022] Figure 1 A schematic diagram of a synthetic jet actuator provided for the invention;

[0023] Figure 2 A schematic diagram of the aerodynamic shape provided for the invention;

[0024] Figure 3 A schematic diagram of the location of the noise shock wave provided for the invention;

[0025] Figure 4 Intent of synthetic jet actuator locations provided for the invention.

[0026] Explanation of the reference numerals: 1. synthetic jet actuator; 2. aerodynamic shape; 3. noise shock wave; 4. blade. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0028] The purpose of the present invention is to provide a method, device and helicopter for suppressing the high-speed pulse noise of a helicopter, so as to solve the problems existing in the prior art, effectively suppress the high-speed pulse noise of the rotor in various flight states and have good applicability.

[0029] 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.

[0030] Example 1

[0031] This embodiment provides a method for suppressing helicopter high-speed pulse noise, such as Figure 1-4 As shown, at least one synthetic jet actuator 1 is embedded in the upper surface of the blade tip. The synthetic jet actuator 1 can generate an upward jet, and the jet can interact with the main flow of the blade to form an aerodynamic shape 2. When high-speed pulse noise is generated, the shock wave on the blade tip is a noise shock wave 3. The opening state and control parameters of the synthetic jet actuator 1 are adjusted to change the shape of the aerodynamic shape 2 to weaken the intensity of the noise shock wave 3.

[0032] The aerodynamic shape 2 is equivalent to a "virtual bulge". When the helicopter generates high-speed pulse noise during high-speed flight, the opening state and control parameters of the synthetic jet actuator 1 are adjusted to adjust the state of the "virtual bulge". The "virtual bulge" can weaken the intensity of the noise shock wave 3 and reduce the "delocalization" phenomenon of the rotor blade tip shock wave, thereby achieving the effect of suppressing the high-speed pulse noise of the helicopter.

[0033] Use computational fluid dynamics (CFD) or wind tunnel test methods to obtain the flow field state of the rotor under different flight conditions. Determine whether the blade tip shock wave meets the conditions for generating high-speed pulse noise. If yes, record the position information of the noise shock wave 3 acting on the blade 4, that is, the minimum distance L between the noise shock wave 3 and the rotor shaft. Li and the maximum distance L Ri , the distance C from the front edge of blade 4 i ,like Figure 3 As shown, the positions of the noise shock waves 3 constitute a noise shock wave generating area A, and the side lengths of the noise shock wave generating area A are L and C, respectively, L = Max (L Ri )-Min(LLi ), C=Max(C i )-Min(C i ), where Min(L Li ) and Max(L Ri ) represent the L of the noise shock wave 3 under each flight state Li The minimum value and L Ri The maximum value, Min(C i ) and Max(C i ) represent the distance C from the noise shock wave 3 to the front edge of the blade 4 in each flight state. i The minimum and maximum values ​​of .

[0034] The noise shock wave generating area A is divided into m×n grids along the radial and chord directions, and a synthetic jet actuator 1 is placed at each grid point to form a synthetic jet actuator array. In order to ensure that the jet can cover the entire noise shock wave generating area A, as shown in Figure 4 As shown, one more layer of synthetic jet actuators 1 is arranged in the outer circle of the noise shock wave generating area A, that is, the number of arranged synthetic jet actuators 1 is (m+2)×(n+2).

[0035] During the test phase, computational fluid dynamics (CFD) or wind tunnel test methods are used to obtain the flow field state of the rotor under different flight conditions. It is determined whether the rotor tip shock wave reaches the condition of generating high-speed pulse noise. If yes, the flight state of the rotor and the azimuth angle (ψ) range of blade 4 when generating high-speed pulse noise are recorded. min ~ψ max and the position information of the noise shock wave 3 acting on the blade 4, that is, the minimum distance L between each noise shock wave 3 and the rotation axis Li and the maximum distance L Ri , the distance C from the front edge of blade 4 i ,like Figure 3 As shown, save to the database.

[0036] During the test phase, under various helicopter flight states when high-speed pulse noise can be generated (obtained using computational fluid dynamics or wind tunnel test methods), the opening state and control parameters of each synthetic jet actuator 1 are adjusted. Specifically, the control parameters include the excitation frequency and the outlet momentum coefficient, and the opening state and control parameters of each synthetic jet actuator 1 are obtained when the high-speed pulse noise is reduced for the first time under various flight states of the helicopter. At this time, the opening state and control parameters of each synthetic jet actuator are the first opening state and the first control parameter, respectively. The flight state of the helicopter and the first opening state and the first control parameter of each synthetic jet shock on the blades 4 at various azimuths are saved in the database.

[0037] When the helicopter is actually flying, it is first determined whether the flight state of the helicopter is within the condition range for generating high-speed pulse noise in the database. If so, the first opening state and the first control parameter of the blades at each azimuth corresponding to the flight state of the helicopter in the database are retrieved, and each synthetic jet actuator 1 is adjusted to the first opening state and the first control parameter, and the aerodynamic shape 2 is adjusted to reduce the intensity of the noise shock wave of the helicopter, thereby reducing the high-speed pulse noise, and finally achieving the effect of reducing the overall noise of the helicopter.

[0038] Example 2

[0039] The present embodiment provides a device for suppressing high-speed pulse noise of a helicopter, including at least one synthetic jet actuator 1 embedded in the upper surface of the blade tip, the synthetic jet actuator 1 can generate an upward jet, the jet can interact with the main flow of the blade 4 to form an aerodynamic shape 2, and adjusting the opening state and control parameters of the synthetic jet actuator 1 can change the shape of the aerodynamic shape 2 to weaken the intensity of the shock wave when the high-speed pulse noise is generated.

[0040] Example 3

[0041] This embodiment provides a helicopter, including a fuselage, a rotor, and a device for suppressing high-speed impulse noise of a helicopter in Embodiment 2, wherein the rotor is rotatably connected to the fuselage, and the device for suppressing high-speed impulse noise of the helicopter is embedded in the upper surface of the blade tip. The opening state and control parameters of the synthetic jet actuator 1 are adjusted to achieve the effect of reducing the high-speed impulse noise of the helicopter.

[0042] The present specification uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for suppressing helicopter high-speed impulse noise, characterized in that: At least one synthetic jet actuator is embedded in the upper surface of the blade tip, the synthetic jet actuator can generate an upward jet, the jet can interact with the main flow of the blade to form an aerodynamic shape, and the shock wave on the blade tip is a noise shock wave when high-speed pulse noise is generated. The opening state and control parameters of the synthetic jet actuator are adjusted to change the shape of the aerodynamic shape to weaken the intensity of the noise shock wave. The synthetic jet actuator is arranged in a noise shock wave generating area, which is an area composed of positions where each noise shock wave acts on the blade, and the noise shock wave generating area is equally divided into m×n grids along the radial and chord directions, and one synthetic jet actuator is placed at each grid point to form a synthetic jet actuator array, and one more layer of the synthetic jet actuator is arranged on the outer circle of the noise shock wave generating area, that is, the number of the arranged synthetic jet actuators is (m+2)×(n+2) to ensure full coverage of the noise shock wave generating area.

2. The method for suppressing helicopter high-speed impulse noise according to claim 1, characterized in that: The position information of the noise shock wave acting on the blade is obtained by using a computational fluid dynamics method.

3. The method for suppressing helicopter high-speed impulse noise according to claim 1, characterized in that: The position information of the noise shock wave acting on the blade is obtained by a wind tunnel test method.

4. The method for suppressing helicopter high-speed impulse noise according to claim 2 or 3, characterized in that: The position information of the noise shock wave acting on the blade includes the maximum distance, the minimum distance and the distance from the front edge of the blade of each noise shock wave.

5. The method for suppressing helicopter high-speed impulse noise according to claim 1, characterized in that: The control parameters of the synthetic jet actuator include an excitation frequency and an outlet momentum coefficient.

6. The method for suppressing helicopter high-speed impulse noise according to claim 1, characterized in that: During the test phase, under different flight states of the helicopter when high-speed pulse noise can be generated, the opening state and control parameters of each synthetic jet actuator are adjusted to obtain the opening state and control parameters of each synthetic jet actuator when the high-speed pulse noise is reduced for the first time under various flight states of the helicopter, at which time the opening state and control parameters of each synthetic jet actuator are respectively the first opening state and the first control parameters; when the helicopter is actually flying, each synthetic jet actuator is adjusted to the first opening state and the first control parameters.

7. The method for suppressing helicopter high-speed impulse noise according to claim 6, characterized in that: When the helicopter is actually flying, it is first determined whether the flight state of the helicopter is within the condition range for generating the high-speed pulse noise. If so, each of the synthetic jet actuators is adjusted to the first opening state and the first control parameter.

8. A device for suppressing helicopter high-speed impulse noise, characterized in that: It includes at least one synthetic jet actuator embedded in the upper surface of the blade tip, the synthetic jet actuator can generate an upward jet, the synthetic jet actuator is arranged in the noise shock wave generating area, the noise shock wave generating area is an area composed of the positions where each noise shock wave acts on the blade, the jet can interact with the mainstream of the blade to form an aerodynamic shape, and adjusting the opening state and control parameters of the synthetic jet actuator can change the shape of the aerodynamic shape to weaken the intensity of the shock wave when high-speed pulse noise is generated.

9. A helicopter, characterized in that: The invention comprises a fuselage, a rotor and the device for suppressing high-speed pulse noise of a helicopter as claimed in claim 8, wherein the rotor is rotationally connected to the fuselage, and the device for suppressing high-speed pulse noise of a helicopter is embedded in the upper surface of the blade tip.

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