RU2487051C2 - Leading edge flap and method of its flowing - Google Patents

Abstract

FIELD: aircraft engineering.

SUBSTANCE: aircraft leading edge flap coupled with main wing and including streamlined surface comprising tail lower edge. Part of said rail lower edge is shaped with even wavy line or wavy line with angular points along wing span. Proposed method consists in using proposed aircraft leading edge flap.

EFFECT: lower aerodynamic noise in takeoff and landing.

4 cl, 7 dwg

Description

The invention relates to the field of aviation, in particular to reducing the aerodynamic noise of an aircraft generated during flow around a wing surface with slats and flaps deflected in approach and landing modes.

Recent advances in the creation of modern turbojet engines with a high degree of bypass ratio have led to a significant reduction in the noise of the power plant. As shown by flight experiments conducted by Boeing and Airbus, the noise of the power plants of modern aircraft ceases to be dominant among other sources of noise when approaching the aircraft when the engines operate in idle mode, and there is a problem of noise generated by the flow around the released landing gear and deflected elements wing mechanization (slats, flaps and spoilers). Thus, the creation of promising civilian aircraft with improved acoustic characteristics, which would satisfy the increasingly stringent ICAO standards for noise on the ground, requires a significant reduction in the noise around the airframe elements of the aircraft. Currently, modern aircraft generally do not use any measures to reduce this noise source. Therefore, increased attention has recently been given to methods that reduce the aerodynamic noise of various elements of an airframe. The present invention relates to the reduction of noise arising from the flow of air over a wing with released mechanization elements: a slat and a flap.

There is a method of reducing aerodynamic noise generated by flowing around the trailing edge of a blade, in which the reduction of aerodynamic noise is achieved by changing the shape of the surface of the trailing edge of the blade (Patent DE 102006043462, 03.27.2008, B64C 21/02). According to the method, the noise level generated by the stream flowing around the trailing edge of the blade is reduced by creating a corrugated surface near the trailing edge, initially having a flat shape. At the same time, noise reduction is achieved due to the formation of longitudinal vortices and a change in the structure of turbulence in the stream flowing around the formed zone. However, this method does not apply to the slat, because in cruise flight mode, when the slat is in the retracted position, it is impossible to ensure a tight fit of the corrugated surface of the slat 1 to the flat surface of the main element of the wing 2, which will inevitably lead to a deterioration in the aerodynamic characteristics of the wing.

Known additional structural elements of the slat (Patents US 2010084508 publ. 2010, IPC B64C 9/24, US 6457680, publ. 2002, IPC B64C 9/16), designed to reduce noise during flow in the gap between the slat and the nose part of the main wing. The main disadvantage of both the above method and the elements of the slat is the use of additional structural elements that deflect the flow, which is associated with an increase in the weight of the device, complication of its design, operation and repair and, as a result, leads to an increase in its cost and operating costs.

A chevron jet nozzle of a gas turbine engine is known (RF Patent No. 2310766, November 20, 2007), in which chevrons are used to create longitudinal vortices formed due to the appearance of a bevel of two streams: the main gas stream flowing from the nozzle and the air stream going on the outer rim of the nozzle. According to this patent, the formation of longitudinal vortices in a jet reduces noise by 1.2 dB. This method is not applicable to reduce slat noise, as when a slat flows around there are no two miscible gas flows and the presence of chevrons does not lead to the formation of longitudinal vortices.

There is a method of reducing the slat noise (RF Patent No. 22966695, November 22, 2002, B64C 9/24), which is quite simple to implement and effective from the point of view of reducing noise, which consisted of using special brushes located on the lower edge of the slat. This patent is selected as a prototype. A noise reduction effect was obtained. However, this method leads to an unacceptably large decrease in the coefficient of lift and complicate the operation of the aircraft, during which it is necessary to replace subject to wear or clogged brushes.

The objective of the invention is to provide an effective reduction in the level of aerodynamic noise generated when an air stream flows around a wing of a passenger aircraft with mechanization elements released (slat and flap) in landing modes without affecting the aerodynamic characteristics of the wing.

The technical result is to reduce the level of aerodynamic noise when flowing around the wing without a significant decrease in lift.

The technical result is achieved in that the wing slat of the aircraft, containing an aerodynamically streamlined surface including the rear lower edge, is movably connected to the main wing, and at least part of the rear lower edge of the slat is made in the form of a smooth wavy line or a wavy line with corner points along wing span.

The technical result is also achieved by the fact that at the wing slat of the aircraft, said edge has a sinusoid shape.

The technical result is also achieved by the fact that at the wing wing slat, said edge is made in the form of a lining.

The technical result is also achieved by the fact that in the method for flowing around an airplane wing slat, which consists in changing the nature of the flow around a trailing lower edge of a slat, at least a portion of a trailing lower edge of a slat is made in the form of a smooth wavy line or a wavy line with corner points along the wing span.

Figure 1. Section of a wing with deflected elements of mechanization.

Figure 2. The flow region between the slat and the main element of the wing.

Figure 3. Sound formation mechanisms in the flow region between the slat and the main wing.

Figure 4. Slat with a chevron edge of a triangular shape.

Figure 5. Different shapes of chevrons of the bottom edge of the slat.

Figa. Slat with a seat for a chevron lining.

Fig.6b. Chevron overlay.

7. Noise spectra of a wing model with conventional and modified slats.

Figure 1 shows a section of a wing with deflected elements of mechanization, consisting of a slat 1, a main wing 2, a flap 3.

The task of reducing the aerodynamic noise generated by the flow in the gap (Fig. 2) between the slat 1 and the nose of the wing 2, without significantly reducing the lift coefficient, is solved by the proposed slat and the method of flow around it.

As a result of studies regarding slat noise, it was possible to identify the main mechanisms for its generation. They are schematically represented in FIG. 3. Among the known mechanisms of noise generation, the following can be listed: secondary separation 4, vortex in cavity 5, unsteady force due to impacts of vortices 6, unsteady flow attachment 7, boundary layer turbulence 8, vortex sheet vanishing 9, piston effect 10, sharp deformation of medium coherent structures stream 11, the confluence of the vortices 12, the noise of the cavity 13, scattering at the edge 14.

The wing slat of the aircraft contains an aerodynamically streamlined surface that can be divided into upper and lower, with front and rear edges, and is movably connected to the main wing. Modification of the slat is to change the shape of the lower edge to the chevron (toothed) (figure 4). By chevron shape (chevron) we mean a wavy line in the plane of the edge, which can be either with corner points or a smooth shape.

The chevron can have any shape with corner points, both triangular, rectangular or other, as well as smooth, for example, in the form of a sinusoid (Fig. 5a). In addition, the chevron may have a non-uniform step S along the span of the slat and a non-uniform height H (Fig. 5b).

The slat may have a seat for the lining (figa), and the lower edge of the slat can be made in the form of a separate chevron lining, which is then attached to the slat (fig.6b).

Experimental studies in an acoustic silenced chamber on a wing model with mechanization showed that a noise reduction method based on changing the geometry of the lower edge of the slat reduces the narrow-band noise of the slat to 10 dB, and the chevron lower edge of the slat significantly reduces noise. The figures 7a, 7b, 7c, 7d show noise spectra, respectively, for viewing angles of 70, 90, 110, 130 degrees in the lower hemisphere under the wing. It is the propagation of sound in this direction that determines the noise of the aircraft on the ground, including during certification tests for noise. The upper curve corresponds to the rectilinear edge of the slat, the two lower curves correspond to the chevron shape of the edge with different pitch and chevron height. The noise reduction effect without a significant reduction in lift occurs for various geometrical parameters of the chevron, as follows from Fig.7.

The proposed method of reducing the aerodynamic noise of an airplane consists in changing the nature of the flow around the lower edge of the slat along the wing span due to the formation of a phase delay of the vortex coming out from the lower edge of the slat and breaking the uniformity of the noise source emitted when the air flow between the slat 1 and the nose of the main wing 2 curvature of the lower edge of the slat along the wingspan.

Turbulence, more precisely, non-stationarity, is formed at a shear (in the limit - a tangential discontinuity), descending from the lower edge. Then it develops, amplifies and falls on the wing part of the system. As a result of interaction with a solid surface, sound is generated. The main idea of the method is to reduce the scale of the correlation of the sound source (decorrelation) in the direction of the wing span and, therefore, to reduce the emitted sound energy.

Decorrelation due to the curvature of the edge of the slat is as follows. After the flow stalls from the edge, vortices arise, which propagate downstream at a speed of the order of α ~ 0.6 ÷ 0.8V, where V is the flow velocity to the edge. The speed of propagation of vortices depends on the nature of the flow in the gap. Because of this, the vortices breaking off from different sections of the curved edge, when approaching the wing surface, have different amplitudes and, most importantly, different phases. Thus, instead of a uniformly correlated sound source, a multitude of uncorrelated sources are formed, which in total emit less sound.

For curvature, the edges form, at least on a part of the surface of the slat, the lower edge of the chevron shape (figure 4).

This method has a development that allows you to optimize its use in particular cases of use.

The proposed slat and the method of flow around it provide an effective reduction in the level of aerodynamic noise created by the flow when it flows in the gap between the slat and the main wing, without a significant reduction in lift.

Claims (4)

1. The wing slat of the aircraft, movably connected to the main wing and containing an aerodynamically streamlined surface including a trailing lower edge, characterized in that at least a portion of the trailing lower edge of the slat is made in the form of a smooth wavy line or a wavy line with corner points along the span wings. 2. The wing slat of the aircraft according to claim 1, characterized in that said edge has a sinusoid shape. 3. The wing slat according to claim 1 or 2, characterized in that said edge is made in the form of a lining. 4. A method for flowing around an airplane wing slat, which consists in changing the nature of the flow around a trailing lower edge of a slat, characterized in that at least a portion of the trailing lower edge of the slat is made in the form of a smooth wavy line or a wavy line with corner points along the wing span.

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