A slat noise reduction device with a lower surface tip arc protrusion

Abstract

The application discloses a slat noise reduction device with a lower wing surface tip arc-shaped protrusion, comprising a leading edge slat, a main wing, a trailing edge flap and a semicircular arc-shaped protrusion device; the leading edge slat, the main wing and the trailing edge flap form a three-section wing configuration; the semicircular arc-shaped protrusion device is arranged on the leading edge slat at a position 0.5% of a wing profile chord length away from a leading edge slat 1 tip, and the diameter of the semicircular arc-shaped protrusion device is 0.3% of the wing profile chord length and is distributed along the spanwise direction. The arc-shaped protrusion of the device leading edge can make the airflow separate in advance, form a small area of back pressure zone behind the arc-shaped protrusion, weaken the vortex-vortex interference and merger phenomenon on the shear layer, and good noise reduction effect can be achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of aviation technology, and particularly relates to a slat noise reduction device with a lower wing surface tip arc-shaped protrusion. BACKGROUND

[0002] The increasingly serious aircraft noise problem is contrary to the concept of green aviation, and the International Civil Aviation Organization has proposed increasingly stringent airworthiness standards to limit civil aviation noise, so that modern civil aviation aircraft can develop in the direction of environmental protection, quietness and comfort. In combination with the lift effect and structural design, modern large civil aviation aircraft are mostly in a three-section wing configuration to achieve the purpose of lift. Figure 1 The three-section wing configuration is in a retracted state during the cruising stage, and the structural components include a leading edge slat 1, a main wing 2 and a trailing edge flap 3.

[0003] During the landing stage of the aircraft, the engine is in a low power stage, at which time the slat is in an open state, and the noise thereof is distributed along the entire wing span direction, being one of the main noise sources. Therefore, the research on slat noise reduction technology has gradually become one of the focus problems of people, and has also become one of the important breakthroughs for researchers to make key progress in aircraft noise reduction. The slat noise spectrum is divided into a low-frequency narrow-band component, a low-frequency wide-band component and a high-frequency narrow-band component. The low-frequency narrow-band component has the characteristics of high peak value and easy identification by the human ear, and is the focus of slat noise reduction research. Common slat noise reduction methods include active flow control and passive flow control methods.

[0004] Document 1, Chinese invention patent with the authorization publication number CN105857576A, discloses a noise reduction slat structure based on jet opening. The jet opening is in the form of a strip, a square or a circle, and is arranged on the upper surface or the lower surface at a distance of 1%-3% of the slat chord length from the leading edge tip. The invention can effectively reduce the noise generated by the slat, especially low-frequency noise. The jet directions of the jet openings on the upper and lower surfaces of the slat and the dimensionless jet flow coefficient are inconsistent, which undoubtedly increases the operation difficulty and reduces the engineering realizability.

[0005] Document 2, Chinese invention patent with the authorization publication number CN103010459B, discloses a method for reducing the aerodynamic noise of a leading edge slat based on a trailing edge micro-perforation. A row of small holes with a diameter of 0.8-1mm and a center distance of 3-5mm from the trailing edge are arranged on the trailing edge of the leading edge slat along the spanwise direction. The spanwise perforation rate is 2%, that is, a line segment with a length equal to the spanwise thickness of the slat is drawn through the center of the small hole along the spanwise direction of the slat, and the length of all the small holes accounts for 2% of the entire length of the line segment. By constructing the pressure difference on the upper and lower surfaces of the slat, a small amount of airflow on the lower surface flows to the upper surface through the small holes, thereby changing the airflow flow before the trailing edge and affecting the trailing edge vortex shedding behavior, so as to reduce the high-frequency narrow-band aerodynamic noise, but the aerodynamic performance is affected.

[0006] Document 3 "Chinese invention patent with publication number CN112173064A" discloses an aircraft wing noise reduction structure based on a slat cavity wave-shaped wall. At least one detachable noise reduction arc-shaped wave-shaped wall plate (a wave-shaped wall surface) is installed in the slat cavity area of the leading edge to promote the rapid evolution of low-frequency large-scale vortex pulsation into high-frequency small-scale vortex structure that is easy to dissipate, while ensuring the aerodynamic performance of the lift device is not affected. The additional effect of the fundamental frequency wave-shaped wall element weakens the vortex flow in the leading edge main sound source area and suppresses noise radiation level. Although the invention has certain noise reduction effect, the engineering operability and later maintainability are poor; at the same time, the energy near the slat cavity is mainly concentrated in the shear layer, and the noise reduction effect of controlling the vortex structure in the backflow area is not relatively significant. SUMMARY

[0007] In order to overcome the shortcomings of the prior art, the present application provides a slat noise reduction device with lower wing surface tip arc-shaped protrusion, which comprises a leading edge slat, a main wing, a trailing edge flap and a semicircular arc-shaped protrusion device.

[0008] The technical scheme adopted by the present application to solve its technical problems is as follows:

[0009] A slat noise reduction device with lower wing surface tip arc-shaped protrusion, comprising a leading edge slat, a main wing, a trailing edge flap and a semicircular arc-shaped protrusion device.

[0010] The leading edge slat, the main wing and the trailing edge flap form a three-section wing configuration.

[0011] The three-section wing configuration has a wing chord length c in the tightened state; the semicircular arc-shaped protrusion device is arranged at a distance of 0.5%c from the tip of the leading edge slat, and the diameter of the semicircular arc-shaped protrusion device is 0.3%c, which is distributed along the spanwise direction.

[0012] Preferably, 0.5%c = 2.15mm and 0.3%c = 1.5mm.

[0013] The present application has the following advantages:

[0014] The arc-shaped protrusion of the device front edge will make the airflow separate in advance, form a small area of back pressure zone behind the arc-shaped protrusion, weaken the vortex-vortex interference and merger phenomenon on the shear layer, and achieve good noise reduction effect. The device has simple structure and reliable design, can realize effective noise reduction without affecting the lift performance, does not affect the wing profile tightening, is convenient for later maintenance, and can realize efficient flow control of shear layer interference and other phenomena. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The three-section wing configuration is in a tightening state in the cruise phase.

[0016] Figure 2 The three-section wing configuration is in an open state.

[0017] Figure 3 The lower wing surface tip arc-shaped protrusion slat noise reduction model.

[0018] Figure 4 The lower wing surface tip arc-shaped protrusion slat structure is a geometric detail description schematic diagram.

[0019] Figure 5 The far-field PSD distribution of the embodiment of the present application without slat tip deformation (reference configuration) and the front edge tip arc-shaped protrusion noise reduction model; wherein the continuous curve represents the PSD distribution of the reference configuration, and the discontinuous curve represents the PSD spectrum of the noise reduction model.

[0020] Figure 6 The OASPL comparison results of the reference configuration and the front edge tip arc-shaped protrusion noise reduction model of the embodiment of the present application, wherein the continuous curve represents the OASPL value of the reference configuration, and the discontinuous curve represents the OASPL value of the noise reduction model.

[0021] BRIEF DESCRIPTION OF DRAWINGS: 1-front edge slat, 2-main wing, 3-aft edge flap, 4-semi-circular arc-shaped protrusion device. DETAILED DESCRIPTION

[0022] The present application will be further described below in conjunction with the drawings and examples.

[0023] Active flow control methods often require energy input, and flow control problems also exist; common passive flow control techniques more or less affect the lift performance, and have poor realizability and other problems. The present application hopes to design a small deformation to the existing slat main body, make the airflow separate in advance to form a turbulent shear layer, reduce the external airflow mixing effect by changing the shear layer motion trajectory, change the development and evolution law of the vortex structure on the shear layer, reduce the energy of the collision area, and effectively reduce the noise.

[0024] In order to ensure that the lift performance of the high-lift device is not affected, the present application carries out small deformation design of the slat, ingeniously combines the multiple relationship between the low-frequency discrete narrowband peak value frequencies and the summary of the small deformation technology of the slat by the predecessors, and adds a semicircular arc protrusion with a specific length to the lower wing surface in front of the slat tip to interfere with the flow separation of the slat tip and break the vortex-sound feedback loop.

[0025] As shown in Figure 2 , in order to interfere with the airflow separation and shear layer development of the slat tip, a slat noise reduction device with a lower wing surface tip arc protrusion comprises a leading edge slat 1, a main wing 2, a trailing edge flap 3 and a semicircular arc protrusion device 4.

[0026] The leading edge slat 1, the main wing 2 and the trailing edge flap 3 form a three-section wing configuration.

[0027] As shown in Figure 1 , the three-section wing configuration is in a retracted state, and the chord length c of the airfoil is provided; the semicircular arc protrusion device 4 is arranged on the leading edge slat 1 at a distance of 0.5%c from the tip of the leading edge slat 1, and the diameter of the semicircular arc protrusion device 4 is 0.3%c, which is distributed along the spanwise direction.

[0028] Figure 2 For the three-section wing configuration in an open state, the leading edge slat is designed to be deformed, and a semicircular arc protrusion is installed on the lower wing surface near the tip of the leading edge slat, and the deformed slat structure can refer to Figure 3 .

[0029] The specific details of the slat deformation can refer to Figure 4 the geometric parameters of the slat structure in the semicircular arc protrusion of the lower wing surface tip. The semicircular arc protrusion is installed at a distance of 0.5%c (0.5%c=2.15mm) from the tip of the slat in the retracted chord length c of the airfoil, and the diameter of the semicircular arc protrusion is 0.3%c (0.3%c=1.5mm) in the retracted chord length of the airfoil.

[0030] Through numerical simulation analysis, it is found that the slat noise reduction device with an arc protrusion at the tip of the lower wing surface can effectively suppress the low-frequency narrowband peak value without affecting the lift performance. There is only a first-order narrowband peak value in the entire frequency range, and the frequency is right-shifted and the amplitude is reduced by about 3dB, and the specific results are shown in Figure 5 , wherein the continuous curve is the power spectral density (PSD) distribution of the reference configuration, and the discontinuous curve is the PSD distribution of the lower wing surface arc protrusion noise reduction model. The overall sound pressure level (OASPL) in the entire range is greatly reduced, especially in the 150° and 300° directions, as shown in Figure 6 . It is shown that the arc protrusion at the tip of the lower wing surface changes the motion characteristics of the sound source, so that the main motion direction is offset.

Claims

1. A slat noise reduction device with a lower wing surface tip arc protrusion, characterized in that, The slotted leading edge wing, the main wing, the trailing edge flap and the semicircular convex device; The slotted leading edge wing, the main wing and the trailing edge flap constitute a three-section wing configuration; The three-section wing configuration is in a tightening state, and the chord length of the airfoil is c; the semicircular convex device is arranged at the tip of the lower surface of the slotted leading edge wing; at a distance of 0.5%c from the tip of the slotted leading edge wing, the diameter of the semicircular convex device is 0.3%c, and the semicircular convex device is distributed along the spanwise direction; The semicircular convex device is used for inducing airflow separation on the lower surface of the slotted leading edge wing, forming a back pressure area to suppress shear layer vortex-vortex interference and merger.

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