DE102006043462A1 - Aerodynamic component e.g. rotor blade, for use in wind turbine, has pair of surface units on high pressure side engaged between two surface units on low pressure side in main extension direction of trailing edge - Google Patents

Abstract

The component (2) has a pair of surface units (5) with an attack angle to a trailing edge (1) of more than forty five degrees, where the edge has wavelike characteristics. The pair of surface units on a high pressure side (9) is engaged between two surface units on a low pressure side (10) in a main extension direction of the trailing edge, where the surface units are engaged against each other. Profile depth of the component is constant over the pair of surface units.

Description

TECHNICAL FIELD OF THE INVENTION

The The invention relates to an aerodynamic component with a turbulently overflowed trailing edge the one overpressure side and a negative pressure side of the component abut, and the further features of the preamble of claim 1.

The aerodynamic component can z. B. an aircraft wing or form a part of it, such as a slat or a flaps. The aerodynamic component can also be used as a rotor blade for a wind turbine or used as a fan or turbo machine blade. The potential However, applications of the aerodynamic component are not finally enumerated.

STATE OF THE ART

Turbulent overflow trailing edge of aerodynamic components creates a so-called trailing edge noise. The trailing edge noise is one of the main sources of noise z. B. in the rotor blades of wind turbines and aircraft wings. Out Howe, MS: "A review of the theory of trailing edge noise", Journal of Sound and Vibration (1978) 61 (3), pp. 437-465 is an analytical solution for calculating the trailing edge noise is known, which gives indications of possible measures to reduce the trailing edge noise.

Thus, the sound radiation is dependent inter alia on the amount of perpendicular to the trailing edge component of the outflow velocity. For this reason, a noise reduction can be achieved by a serrated serially trailing edge, ie a periodic variation of the profile depth in the region of the trailing edge, as already described in US Pat DE-OS-25 27 467 is known. However, with a serrated trailing edge, the trailing edge noise can only be significantly reduced if the trailing edge of the trailing edge is exactly parallel to the adjacent surfaces of the aerodynamic component and the alignment of the serrations.

Another influencing variable resulting from the analytical consideration of the trailing edge noise is the amount of flow turbulence near the trailing edge. For local damping of the turbulent pressure fluctuations at the trailing edge, therefore, trailing edge approaches made of porous materials ( Herr, M., Dobrzynski, W .: "Experimental investigations in low-noise trailing-edge design", AIAA Journal Vol. 6, pp. 1167-1175 ) or bristles ( EP 1 314 642 B1 ) used to reduce the trailing edge noise. Although the rear edge noise reductions achievable with porous bodies or bristles attached to the trailing edge are insensitive to variations in the direction of overflow of the trailing edge, in practice they suffer from the disadvantages of contamination (closure of the pores of a porous body) or wear ( bristles).

An aerodynamic component having the features of the preamble of claim 1 is known from EP 112 928 A2 known. Here the trailing edge is thickened towards the overpressure side and, in the region of the thickening on the overpressure side, it has incisions whose free cross section is delimited by pairs of surface elements which are opposite one another and set the direction of the main trailing edge. The two surface elements of such a pair may be arranged parallel to one another, which corresponds to a slot in the overpressure side of the component, be arranged in a V-shape relative to one another, which corresponds to a V-shaped groove in the overpressure side of the component, or as a half-wave of a sine function rounded into one another pass. In any case, the cuts are laterally spaced apart by more than the maximum width of the cuts, and the cuts in its overpressure side leave unaffected the profile profile of the aerodynamic component on its negative pressure side. Whether that from the EP 1 112 928 A2 known aerodynamic component an effective reduction of the trailing edge noise is achieved, given the fact that at the trailing edge to its negative pressure side thickened profiles basically lead to an increase in the sound level of the trailing edge noise, rather questionable.

OBJECT OF THE INVENTION

Of the Invention is based on the object, an aerodynamic component to show with the features of the preamble of patent claim 1 with no sensitivity with respect to the overflow direction of the trailing edge and without any problem in practical use the trailing edge noise effectively is mitigated.

SOLUTION

The The object of the invention is achieved by an aerodynamic component the characteristics of the independent Patent claim 1 solved. Preferred embodiments of the aerodynamic component are to the dependent claims 2 to 11 defined.

DESCRIPTION OF THE INVENTION

at the new aerodynamic component, the trailing edge has a wave-shaped course. The waves of the trailing edge are perpendicular to their main extension direction and perpendicular to the direction of their overflow, so that in the main direction of extent the trailing edge in each case a pair of employees against each other interface elements on the overpressure side between two adjoining salaried surface segments engages the negative pressure side. The waveform of the trailing edge detects both the adjacent areas of the overpressure side as well as adjacent areas of the negative pressure side of the aerodynamic Component. Practice it both opposite the middle course of the trailing edge cut troughs as also the opposite of the middle course of the trailing prominent peaks one Function with regard to the reduction of the trailing edge noise, by bringing with them the local flow field and the turbulence structure at the trailing edge are affected. In this case, an accumulation of the delayed boundary layer flow in the troughs, whereby a reduction of the effective outflow velocity over a Part of the trailing edge length is reached. In addition, as a result of the displacement effect of the wave crests longitudinal vortices which leads to a transformation of the turbulence structure in the Lead the senses, that turbulent speed fluctuations predominantly in the Main extension direction of the trailing edge are generated, the for the genesis the trailing edge noise are of no material importance. Compared to the known measures to reduce the trailing edge noise is the modification of the invention the rear edge of an aerodynamic component insensitive to in the Application expected deviations from the mean overflow direction in the design case. Attachments subject to wear the aerodynamic component is not required.

Preferably is a profile depth of the component via at least one pair, preferably essentially each pair of opposing surfels constant. That is, the trailing edge of the new aerodynamic component is not additional jagged. The tread depth of the component must, however, over a pair of against each other employed interface elements not be absolutely exactly constant. It is enough, if it is essentially constant. Thus, the surface normal one of the wavy trailing edge stretched surface across from the direction of the overflow of the Trailing edge have a tilt angle, causing the velocity component the overflow perpendicular is reduced to the trailing edge. A suitable angle of inclination is typically 20 ° to 60 °, preferably 40 ° to 50 ° and is with a variation of the tread depth of the aerodynamic component over the to every employed surface segment connected to adjacent area of the trailing edge.

A Profile thickness of the new aerodynamic component is along the Trailing edge preferably also substantially constant. there is due to the waveform of the trailing edge hereby always the profile thickness meant perpendicular to the considered segment of the trailing edge. moreover The profile thickness does not have to be completely constant even with this approach but it can vary by as much as ± 50% or even more.

The described by the trailing edge of the new aerodynamic component troughs and wave mountains can be asymmetrical. Preferably, however, at least one pair the opposing surface elements mirror-symmetrical formed to a mirror plane which is normal to the main extension direction the trailing edge runs. Particularly preferred are all pairs of employees employed against each other interface elements so mirror-symmetrical.

Of the Angle of attack of each of the employed surfels to the trailing edge can be at least 60 ° with the new aerodynamic component, so that the opening angle each wave tale at most 60 °. Preferably However, the angles of attack of the employed surface elements are even larger and range from 75 to 90 °. Accordingly closes the opposing surface segments of each pair one acute angles or even parallel to each other.

The transition areas between the employed interface elements can z. B. be rounded, so that an approximately sinusoidal course the trailing edge yields. But the transitions can also be acute-angled, resulting in an approximately sawtooth-shaped course of the trailing edge results.

A Wave depth caused by the height that of a pair of opposing surface elements limited parallel to the main extension direction of the trailing edge Space is defined at the trailing edge of the new aerodynamic component preferably greater than six times the displacement thickness a turbulent boundary layer of the overflow of the trailing edge. Especially Preferably, the wave depth is greater than eight times this displacement thickness.

Since the new aerodynamic component has the waveform only in the region of its trailing edge, the wave depth decreases away from the trailing edge counter to the direction of the overflow. These Decrease is preferably continuous and most preferably strictly monotonic.

The Length of employed interface elements in the direction of the overflow of Trailing edge, d. H. the length over which the waveform of the trailing edge extends into the surface of the new aerodynamic component extends, is preferably greater than that Three times the wave depth at the trailing edge. Especially preferred is the length the employed surface elements greater than four times the wave depth at the trailing edge. A practical one Maximum value for the length the employed surface elements is at ten times the wave depth at the trailing edge. A practical one Maximum value for the wave depth at the trailing edge is approximately one third of the tread depth of the aerodynamic component.

advantageous Further developments of the invention will become apparent from the claims, the Description and the drawings. The in the introduction to the description advantages of features and combinations of several Features are merely exemplary and may be alternative or cumulative come into effect, without the benefits of mandatory embodiments of the invention must be achieved. Other features are the drawings - in particular the illustrated Geometries and the relative dimensions of several components to each other as well as their relative arrangement and operative connection - can be seen. The combination of features of different embodiments the invention or features of different claims is also different from the ones chosen The antecedents of the claims possible and is hereby stimulated. This also applies to such features as in separate drawings are shown or in their description to be named. These features can be combined with features of different claims. As well can in the claims listed Features for more embodiments the invention omitted.

BRIEF DESCRIPTION OF THE FIGURES

The Invention will be described below with reference to exemplary embodiments with reference on the attached Drawings closer explained and described.

1 shows the emission characteristics of the generated at the trailing edge of an aerodynamic component trailing edge noise with a view across the overflow of the trailing edge.

2 shows the emission characteristic of the trailing edge noise with a view towards the overflow of the trailing edge.

3 shows an inventive aerodynamic component with corrugated trailing edge in a perspective view.

4 shows a possible sinusoidal course of the trailing edge of the new aerodynamic component.

5 shows a possible sawtooth course of the trailing edge of the new aerodynamic component; and

6 shows another possible course of the trailing edge of the new aerodynamic component.

DESCRIPTION OF THE FIGURES

Trailing edge noise is caused by the spontaneous relaxation of turbulent pressure fluctuations at the trailing edge transported in a boundary layer flow 1 a turbulent overflowed aerodynamic component 2 , This relaxation is caused by the sudden elimination of the solid boundary layer boundary flow. During relaxation, part of the kinetic energy of the turbulence becomes the overflow of the aerodynamic component 2 converted into propagatable sound waves. Since the correlation lengths of the turbulent pressure fluctuations are usually much smaller than the extension of the considered trailing edge in their main extension direction, the sound level of the radiated trailing edge noise increases in proportion to the length of the trailing edge wetted by the flow 1 in their main extension direction. The emission characteristic of the trailing edge noise in the direction of the overflow is dependent on the ratio of the dimensions of the aerodynamic component to the wavelength of the trailing edge noise. For a profile depth of the aerodynamic component which is large compared with the wavelength of the trailing edge noise, the emission characteristic takes the form of a 1 reproduced cardioids 3 at. In 1 is the direction of the overflow of the trailing edge with an arrow 4 located.

The radiation characteristic perpendicular to the direction of the overflow and perpendicular to the surface normals of the overflowed aerodynamic component can, however, over all wavelengths by a dipole 4 be approximated as he is in 2 is reproduced. This results depending on the in 2 defined angle φ for all of the perpendicular to the trailing edge and the perpendicular to the surfaces of the overflow aerodynamic component 2 deviating emission directions a reduction of the sound level according to: .DELTA.L φ = 10 · log (cosφ). (1)

Therefore, if a shape of the trailing edge that is corrugated to the surface normals of the overflowed aerodynamic component is selected, as in FIG 3 is shown, according to equation (1) results in a reduction of the radiated in the direction of the surface normal sound pressure level, however, by the simultaneous extension of the length of the wetted trailing edge according to Iα = I / cos α, (2) where α is the angle of attack of a surface element forming the waveform of the trailing edge 5 of the aerodynamic component 2 is compensated.

Thus, the waveform is the trailing edge 1 with regard to the in practice significant radiation of the trailing edge noise perpendicular to the surfaces of the overflow aerodynamic component 2 and perpendicular to the direction of its overflow, ie towards the ground, effect neutral, while the noise radiation in the direction of the main extension direction of the trailing edge, that is laterally, even increased. This point is for the application z. B. in aircraft but irrelevant, since due to the long sound propagation paths, the trailing edge noise in the lateral direction is usually strongly attenuated.

For the effect of the wavy trailing edge, however, which reduces the trailing edge noise, the influence of the local flow field and its turbulence structure on the trailing edge is decisive 1 , These influences include the accumulation of the delayed boundary layer flow in the troughs 6 , thereby reducing the effective outflow velocity over part of the length of the trailing edge 1 is reached. In addition, as a result of a displacement effect of the wave crests 7 longitudinal vortices 8th generated, which lead to a transformation of the turbulence structure in the sense that turbulent velocity fluctuations are generated primarily in the main extension direction of the trailing edge, whereby they are of no importance for the noise generation.

Another effect reducing the trailing edge noise can be achieved by making the normal one through the undulating trailing edge 2 spanned plane with respect to the direction of the overflow of the aerodynamic component 2 is inclined, causing the velocity component perpendicular to the trailing edge 2 is reduced.

A wave depth h of the selected trailing edge 1 should be greater than eight times the displacement of the turbulent boundary layer at the trailing edge 1 ; and a length s over which the waveform of the trailing edge into the aerodynamic component 2 runs out, should be more than about four times the wave depth h. The profile of the aerodynamic component 2 runs in the trailing edge 1 usually at an acute angle, so that a positive pressure side 9 and a negative pressure side 10 of the component 2 at an acute angle at the trailing edge 1 collide. This basic form of the profile of the aerodynamic component 2 is about the waves of the trailing edge 1 get away. The angle of attack α, by the waveform of the trailing edge 1 trained, opposite the main extension direction 11 the trailing edge employed surface elements 5 on the overpressure side 9 and the negative pressure side 10 is preferably at least 75 °, so that an opening angle of the troughs 6 maximum 30 °.

The waveform of the trailing edge 1 normal to their main extension direction 11 may be composed of straight sections between which rounded transitions are provided. This corresponds to the embodiment of the trailing edge 1 according to 3 , The trailing edge 1 but can also be sinusoidal, as in 4 is reproduced. In this case, the fillets are between the surface segments 5 more pronounced. But it is also a sawtooth trailing edge 1 possible at the the surface segments 5 pass under sharp angles. This is in 5 outlined. 6 on the other hand shows a parallel alignment of the pairs of opposing surface segments 5 with semicircular transition elements. In this case, the angle of attack of the individual surface elements is 5 opposite the main extension direction 11 the trailing edge 1 90 °.

1

trailing edge

2

aerodynamic component

3

cardioid

4

dipole

5

interface element

6

trough

7

Wellenberg

8th

longitudinal vortices

9

Pressure side

10

Vacuum side

11

Main direction of the

trailing edge

α

angle of attack

s

length

H

wave height

l

wavelength

Claims (11)

Aerodynamic component with a turbulent overflowed trailing edge, on which an overpressure side and a negative pressure side of the component abut, wherein the component in the direction of overflow in the trailing edge expiring surface elements which are employed relative to the main extension direction of the trailing edge in pairs against each other, each of the employed surface elements an angle of attack to the trailing edge greater than 45 °, characterized in that the trailing edge ( 1 ) has a wave-shaped course, in which in the main extension direction of the trailing edge ( 1 ) each have a pair of opposing surface elements ( 5 ) on the overpressure side ( 9 ) between two adjoining employed surface elements ( 5 ) at the negative pressure side ( 10 ) intervenes. Aerodynamic component according to claim 1, characterized in that a profile depth of the component ( 2 ) via at least one pair, preferably each pair of opposing surface elements ( 5 ) is constant. Aerodynamic component according to claim 1 or 2, characterized in that a profile thickness of the component ( 2 ) along the trailing edge over at least one pair, preferably each pair of facing surface elements ( 5 ) is at least ± 50% constant. Aerodynamic component according to one of claims 1 to 3, characterized in that at least one pair, preferably each pair of opposing surface elements ( 5 ) is mirror-symmetrical to a mirror plane which is normal to the main extension direction (FIG. 11 ) of the trailing edge ( 1 ) runs. Aerodynamic component according to one of claims 1 to 4, characterized in that each of the employed surface elements ( 5 ) an angle of attack (α) to the trailing edge ( 1 ) of at least 60 °, preferably from 75 ° to 90 °. Aerodynamic component according to one of claims 1 to 5, characterized in that the course of the trailing edge ( 1 ) sinusoidal with rounded transitions between the employed surface elements ( 5 ). Aerodynamic component according to one of claims 1 to 5, characterized in that the course of the trailing edge ( 1 ) sawtooth with acute-angled transitions between the employed surface elements ( 5 ). Aerodynamic component according to one of claims 1 to 7, characterized in that a wave depth (h), determined by the height of a pair ( 5 ) of opposing surface elements ( 5 ) parallel to the main extension direction ( 11 ) of the trailing edge ( 1 ) is defined at the trailing edge ( 1 ) greater than six times, preferably greater than eight times the displacement thickness of a turbulent boundary layer of the overflow of the trailing edge ( 1 ). Aerodynamic component according to claim 9, characterized in that the wave depth (h) counter to the direction of the overflow from the trailing edge ( 1 ) steadily decreases. Aerodynamic component according to claim 9 or 10, characterized in that a length (s) of the employed surface elements ( 5 ) in the direction of the overflow greater than three times, preferably greater than four times the wave depth (h) at the trailing edge ( 1 ). Aerodynamic component according to one of claims 1 to 10, characterized in that the surface normal of one of the wavy trailing edge ( 1 ) spanned surface with respect to the direction of the overflow of the trailing edge ( 1 ) has an inclination angle of 20 ° to 60 °, preferably from 40 ° to 50 °.