A high mach cavity noise control method

Abstract

This invention discloses a method for controlling high Mach cavity noise. A spoiler is positioned upstream of the leading edge along the airflow direction, with the leading angle of the spoiler being smaller than its trailing angle. This invention targets high Mach (3Ma) cavity flow, achieving suppression of aerodynamic noise and realizing a significant noise reduction effect (approximately 12 dB in the most severe conditions).

Description

Technical Field

[0001] This invention belongs to the field of cavity noise control, and in particular, a method for controlling high Mach cavity noise. Background Technology

[0002] Cavity flow is widespread in aircraft, with internal bomb bay flow being one of the most typical examples. Cavity flow structures are complex, and due to the interaction of shear layers, vortices, and shock waves, they generate strong pressure pulsations and aerodynamic noise.

[0003] Currently, there are two main methods for controlling cavity noise: active control and passive control. Patent application number 202210462081.1 discloses a cavity noise suppression method using a bulge-type protrusion. This method is mainly for cavity flow under conditions of 0.85 Ma. However, it has the disadvantages of high cost of flexible skin, relatively complex deformation mechanism, and low noise reduction effect (about 3dB). Summary of the Invention

[0004] The purpose of this invention is to provide a method for controlling high Mach cavity noise, which aims to suppress aerodynamic noise in high Mach (3Ma) cavity flow and achieve a significant noise reduction effect (approximately 12dB in the most severe cases).

[0005] The technical solution to achieve the purpose of this invention is as follows:

[0006] A method for controlling high Mach cavity noise involves placing a spoiler upstream of the leading edge along the airflow direction, wherein the front angle α of the spoiler is smaller than the rear angle β of the spoiler.

[0007] In a further embodiment, the geometric parameters of the spoiler satisfy: α≤30°, 30°<β≤60°, 0.8δ≤h≤1.2δ, 0.5h≤b≤h;

[0008] Where h and b are the height and top width of the spoiler, respectively, and δ is the boundary layer height.

[0009] In a preferred embodiment, the front angle α of the spoiler is 10° and the rear angle β is 45°.

[0010] In a further embodiment, the side width of the spoiler is c = W, where W is the cavity width.

[0011] In a further embodiment, the spoiler 1 is located one boundary layer height upstream of the cavity leading edge.

[0012] In a preferred embodiment, h = 0.85δ and b = 0.882h.

[0013] The significant advantages of this invention compared to existing technologies are:

[0014] This invention targets high Mach (3Ma) cavity flow, achieving suppression of aerodynamic noise and a significant noise reduction effect (approximately 12dB at the most severe locations). Attached Figure Description

[0015] Figure 1 This is a schematic diagram showing the position arrangement of the spoiler of the present invention.

[0016] Figure 2 These are front and top views of the spoiler.

[0017] Figure 3 The global sound pressure level distribution is shown on the symmetrical surface of the cavity bottom with or without an irregular spoiler.

[0018] Figure 4 The global sound pressure level distribution on the symmetrical plane of the cavity rear wall with / without irregular spoilers.

[0019] Figure 5 The pressure change curve at monitoring point Z / D = 0.95.

[0020] Figure 6 Distribution diagram of monitoring points at the bottom of the cavity.

[0021] Figure 7 Distribution diagram of monitoring points on the rear wall of the cavity.

[0022] Figure 8 The global sound pressure level distribution on the symmetrical surface of the cavity bottom with different jet intensities.

[0023] Figure 9 The global sound pressure level distribution on the symmetrical plane of the cavity rear wall for different jet intensities. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0025] like Figure 1 The diagram shown is a structural schematic of the present invention. Figure 1 The cavity structure includes a cavity with a single-sided opening, a leading edge 2, a bottom surface 3, and a trailing edge 4. Under high Mach conditions, the cavity noise originates from the vortex shedding caused by the separation of the shear layer at the leading edge 2, the pressure pulsation generated by the periodic impact of the shear layer on the trailing edge 4, and the forward propagation disturbance within the cavity.

[0026] In this embodiment, an irregular spoiler 1 structure is set upstream of the leading edge 2 along the airflow direction. The irregular spoiler 1 is located at a certain distance upstream of the cavity leading edge (approximately 1 boundary layer height). The height of the irregular spoiler 1 should be 0.8 to 1.2 times the boundary layer height. A smaller angle of 10° is used at the front of the spoiler 1, and a larger angle of 45° is used at the rear of the spoiler 1. The reasons for doing so are: 1. to increase the height of the shear layer; 2. to reduce the impact on the stability of the shear layer; 3. to reduce the loss of aerodynamic performance.

[0027] In this embodiment, the dimensional parameters of the irregular spoiler are as follows: Figure 2 As shown in mm, the top of the spoiler is parallel to the bottom. In this example, the cavity length is 4.18m, the depth is 0.597m, and the width is 0.314m. Under atmospheric conditions of Mach 3 and an altitude of 25km, numerical simulations were performed using Fluent software with a grid of 20 million. The boundary layer height of the incoming flow through the cavity was approximately 100mm.

[0028] The main parameters of an irregular spoiler include the front angle α, rear angle β, height h, top width b, and side width c. Where α ≤ 30°, 30° < β ≤ 60°, 0.8δ ≤ h ≤ 1.2δ, and 0.5h ≤ b ≤ h. Here, we choose α = 10°, β = 45°, h = 0.85δ, b = 0.882h, and c = W (W is the cavity width, i.e., the width perpendicular to the front surface of the spoiler). δ is the boundary layer height.

[0029] Numerical simulations show that this method can effectively reduce aerodynamic noise at the bottom and rear of the cavity under high Mach conditions, with an overall reduction of approximately 10 dB in global sound pressure level.

[0030] This invention features a simple structure, rapid operation, and excellent control performance. The control effect on the global sound pressure level of the symmetrical plane at the bottom of the cavity and the total sound pressure level of the rear wall of the cavity is as follows: Figure 3 and Figure 4 As shown. Figure 3 This is a line graph showing the global sound pressure level at each monitoring point on the symmetrical surface of the cavity bottom, with 10 monitoring points on the horizontal axis. Figure 6 The location distribution of monitoring points at the bottom of the cavity (direction consistent with the incoming flow direction), Figure 7 The diagram shows the distribution of monitoring points on the rear wall of the cavity. As can be seen from the diagram, a noise reduction effect of approximately 12 dB can be achieved at the Z / D = 0.95 position. Here, Z / L = 0.95 represents the monitoring point being located at 95% of the cavity depth (along the lip direction at the bottom of the cavity).

[0031] This invention employs an active flow control method to achieve the same noise reduction effect. Figure 8 For the global sound pressure level distribution of the symmetrical surface of the cavity bottom with different jet intensities, Figure 9The global sound pressure level distribution on the symmetrical plane of the cavity rear wall under different jet intensities is shown. 0.95mm, 1.9mm, and 5.7mm represent the jet slot width, respectively, and 0.1lbm represents the jet intensity, which is equal to a mass flow rate of 0.0454kg / s. Simulations show that a global sound pressure level noise reduction effect of up to 11dB can be achieved under the condition of a 0.4lbm mass jet.

Claims

1. A high Mach cavity noise control method, characterized by, A spoiler is placed upstream of the leading edge along the direction of airflow, and the front angle α of the spoiler is smaller than the rear angle β of the spoiler; The top of the spoiler is parallel to the bottom, and the length of the top is less than that of the bottom; the geometric parameters of the spoiler satisfy: α≤30°, 30°<β≤60°, 0.8δ≤h≤1.2δ, 0.5h≤b≤h; Where h and b are the height and top width of the spoiler, respectively, and δ is the boundary layer height; The side width of the spoiler is c = W, where W is the cavity width.

2. The high Mach cavity noise control method of claim 1, wherein, The front angle of the spoiler is α = 10°, and the rear angle of the spoiler is β = 45°.

3. The high Mach cavity noise control method of claim 1, wherein, The spoiler 1 is located one boundary layer height upstream of the cavity leading edge.

4. The high Mach cavity noise control method according to claim 1, characterized in that, h = 0.85δ, b = 0.882h.

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