DE102013006203A1 - Rotor blade for wind turbine, comprises profile, which has suction side that is convexly curved in central portion having fixed radius, where central portion of suction side has length, whose projection extends to chord from leading edge - Google Patents

Abstract

The rotor blade comprises a profile (1), which has a suction side (2), a pressure side (3), a leading edge (4), a trailing edge (5) and a chord (6) with a profile depth (T). The pressure side is convexly curved with a fixed radius (R-d). The suction side is convexly curved in a central portion (Z-b) having a fixed radius (R-s). The central portion of the suction side has a length, whose projection extends to the chord over a range of 10 percentage to 90 percentage of the profile depth (T) from the leading edge.

Description

The present invention relates to a rotor blade having the features of the preamble of claim 1.

Wind turbines are characterized by a particularly complex rotor aerodynamics. In addition to the blade rotation, the rotor is additionally exposed to external influences, such as atmospheric turbulence, as well as temporal and spatial variations in the flow velocity. Many of these fluid mechanical problems in wind turbines are closely related to those of helicopter rotors and thus directly transferable.

So that the buoyancy force can fully develop with an aerodynamic buoyancy of a rotor blade, the flow of the wind must rest as long as possible on the profile of the rotor blade. Due to the longer concern of the flow is also reduced, emanating from the rotor tip noise emission.

From the DE 10 2008 052 858 A1 is a family of aerodynamic profiles known that are designed to optimize the performance of wind turbines. These profiles are characterized in that the skeleton line runs at least in sections below the chord in the direction of the pressure side.

It is an object of the present invention to provide a rotor blade which has good aerodynamic properties and reduces the emanating from the rotor tip acoustic emission.

This object is achieved by a rotor blade having the features of claim 1.

Thereafter, a rotor blade with a profile having a suction side, a pressure side, a profile nose, a trailing edge profile and a chord with a tread depth, wherein the pressure side is convexly curved with a fixed radius, provided in which the suction side in a central portion with is convexly curved at a fixed radius. The circular impact-like shape of the suction side causes a long concern of the air mass.

In the inventive embodiment it is advantageous if the central portion of the suction side has at least one length whose projection on the chord extends over a range of 10% to 90% of the tread depth of the profile nose. As a result, the flow is particularly long and up to 90% of the tread depth of the profile nose on.

Furthermore, it is preferably provided that the radius of the pressure side is equivalent to twice the tread depth.

It is advantageous if the radius of the suction side is equivalent to the tread depth.

In addition, it is advantageous if the front and rear portions of the suction side are connected to the circular impact-like central portion of the suction side so that the mathematical function of the course is differentiable.

In the inventive embodiment also has the rotation and taper of the profile on a linear course, which is adapted to the diameter of the rotor. Thus, a constantly applied flow velocity of the wind on the rotor blade from the blade root to the blade tip can be achieved, which ensures optimum energy yield and low-noise operation.

A preferred embodiment of the invention will be explained in more detail with reference to the drawing. It shows:

1 : a cross-section of a rotor blade,

2 : schematic representation of a wind turbine,

3 : Profile view of a linear profile twist, as well

4 : Construction sketch of the linear profile twist.

In the 1 is a profile according to the invention 1 a rotor blade shown. The profile 1 is defined by its suction and pressure side 2 . 3 and a profile depth T. The profile depth T is defined as the straight connection of profile nose 4 after profile trailing edge 5 , The curvature of the pressure side 3 is constant with a radius R _D. The radius R _{D of} the tread depth T is equivalent.

The course of the suction side 2 however, it can be divided into three sections: a front, a middle and a rear section Z _a , Z _b , Z _c . For the description of the sections Z _a , Z _b , Z _c are two points A, B on the chord 6 defined: the first point A lies from the profile nose 4 starting at a depth of 10% of the tread depth T, the second point B is from the profile nose 4 at a depth of 90% of the tread depth T. The front section Z _{a of} the suction side 2 is then defined as the piece of the profile nose 4 up to the first point of intersection where the solder from the first point A of the chord 6 the suction side 2 cuts. The section of from this first point of intersection to the second point of intersection at which the perpendicular from the second point B of the chord 6 the suction side 2 is referred to as the middle section Z _b . Furthermore, the rear portion Z _{c is} given as the portion between the second intersection and the trailing edge of the profile 5 , In this case, the course of the central portion Z _{b has} a constant curvature with a radius R _S , which is equivalent to the double tread depth T. The front and rear portions Z _a , Z _c connect the central portion Z _{b of} the suction side 2 with the profile nose 4 and profile backside 5 such that the descriptive mathematical function is differentiable at each point and a convex course of the suction side 2 is maintained.

By the circular impact-like course of the central portion Z _{b of} the suction side 2 a longer concern of the flow is effected and thus largely reduces the noise emission.

The illustrated setting angle between rotor plane and chord 6 has the position at the leaf root. The twisting and tapering of the profile is linear and depends on the diameter of the rotor. Preferably, the profile has a taper from the blade root to the blade tip in the tread depth and perpendicular thereto profile height by half.

2 shows a wind turbine, which is a rotation axis d of the rotor, a scar 7 and from the scar 7 outgoing rotor blades 8th with leaf root 9 and blade tip 10 having. Here, r _{s is} the distance between the axis of rotation d of the rotor and the blade tip 10 , r _{m is} the distance between the axis of rotation d of the rotor and the rotor blade center, and r _{w is} the distance between the axis of rotation d of the rotor and the blade root 9 ,

3 shows a rotor blade twist. Because the blade tip 9 a higher speed compared to the blade root 10 has, must the profile 1 of the rotor blade become flatter from the blade root to the blade tip. This is preferably generated by rotation of the profile, wherein a twist angle α (r), the angle of the chord of the profile at a distance r from the axis of rotation d of the rotor to the chord on the blade root 61 describes, linear changes.

3 shows the profile 1 at the leaf root with chord 61 and the profile at the blade tip with chord 62 , For the sake of completeness, the wind direction of the wind is denoted by W and D indicates the direction of rotation of the rotor. The diameter of the rotor in this particular embodiment is 5 m. The slope S, the distance of the wind along the rotor, which is needed for one revolution of the rotor, is 2.50 m. The greater the slope S, the more wind flow through the rotor, a greater torque, easier starting of the rotor and lower speed with less noise. The desired revolution per minute of the rotor can be achieved by adjusting the slope S to the wind speed. Since preferably the pitch S along the rotor is constant from the blade root to the blade tip, the twist angle α between blade root and blade tip in this particular example is 38.84 °.

In general, the angle of rotation α (r) at a constant pitch S is given by the following equation:

4 shows the geometric construction of the angle of rotation α (r) for the embodiment of 3 , On the vertical axis the slope is S and on the horizontal axis the circumference of the rotor is applied to the blade tip. These two axes form the catheters of a right-angled triangle, the angle α (r _s ) between the hypotenuse and the adjacent leg being the sum of the angle of rotation α _s to be determined and the angle α (r _w ) = α _w , and the angle α _w is determined by applying the circumference of the rotor to the blade root on the horizontal axis and reads the angle between new hypotenuse and new Ankathete at a constant slope S. To further determine the angle of rotation α _{m of} the rotor blade center, one carries on the horizontal axis of the circumference of the rotor at the rotor blade center and reads the angle α (r _m ) between new hypotenuse and new Ankathete at a constant slope S and subtracts α _w .

The twist angle α (r) thus indicates the rotation of the profile starting from the blade root of the rotor blade.

For power control, a so-called angle of attack of the rotor, the angle between the direction of the inflowing air and the chord, is changed. In this case, the angle of attack is set at the blade root, so that this angle rotates the entire rotor blade against the incoming air. Due to the rotation of the rotor blade, the angle of attack always flattens linearly from the blade root to the blade tip.

By means of the profile twist according to the invention, the twist angle α (r) can be calculated for any point of the rotor blade. The linear profile twist and its construction are applicable to all sizes of wind turbines, all gradients and all angles of attack. By the rotation of the rotor blade profile according to the invention a constant pitch from the blade root to the blade tip can be achieved, making the rotor rotate quietly and energy efficiently.

LIST OF REFERENCE NUMBERS

1

profile

2

suction

3

pressure side

4

profile nose

5

Trailing edge

6

chord

61

chord

62

chord

7

scar

8th

rotor blade

9

blade root

10

blade tip

T

tread depth

R _D

Radius pressure side

R _S

Radius suction side

Z _a

front section

Z _b

middle section

Z _c

rear section

d

Rotary axis rotor

r _s

Distance d-10

_m

Distance d-8

r _w

Distance d-9

D

Direction of rotation of the rotor

W

Flow direction of the wind

α _s

Angle of rotation between the profile root of the blade root and the chord of the blade tip

α _w

Angle between the axis of rotation and chord of the blade root

α _m

Angle of rotation between chord root and chord of the blade center

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008052858 A1 [0004]

Claims (8)

Rotor blade with a profile ( 1 ), which has a suction side ( 2 ), a printed page ( 3 ), a profile nose ( 4 ), a profile trailing edge ( 5 ) and a chord ( 6 ) with a tread depth (T), wherein the pressure side ( 3 ) is convexly curved with a fixed radius (R _D ), characterized in that the suction side ( 2 ) is convexly curved in a central portion (Z _b ) having a fixed radius (R _S ). Rotor blade according to claim 1, characterized in that the central portion of the suction side (Z _b ) has at least one length whose projection on the chord over a range of 10% to 90% of the tread depth (T) of the profile nose ( 4 ) extends. Rotor blade according to at least one of the preceding claims, characterized in that the radius (R _D ) of the pressure side ( 3 ) is equivalent to twice the profile depth (T). Rotor blade according to at least one of the preceding claims, characterized in that the radius (R _s ) of the suction side ( 2 ) is equivalent to the tread depth (T). Rotor blade according to at least one of the preceding claims, characterized in that the front and rear portions of the suction side (Z _a , Z _c ) with the circular impact-like central portion of the suction side (Z _b ) are connected so that the mathematical function of the course is differentiable. Rotor blade according to at least one of the preceding claims, characterized in that a twist and a taper of the profile of a blade root ( 9 ) to a blade tip ( 10 ) have a linear course, which is adapted to the diameter of the rotor. Rotor blade according to claim 6, characterized in that the rotation of the profile of a pitch (S) and the diameter of the rotor is dependent, so that the slope (S) of the blade root ( 9 ) to the tip of the blade ( 10 ) is constant. Rotor blade according to claim 7, characterized in that the rotation with a twist angle (α (r)), which indicates the angle between a chord on the blade root and a chord at a distance (r) from a rotational axis (d) of the rotor, and a Distance (r _w ) from a rotation axis (d) of the rotor to the blade root ( 9 ) by

given is.

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