WO1996001368A1

WO1996001368A1 - Wind-energy convertor with a vertical axis of rotation

Info

Publication number: WO1996001368A1
Application number: PCT/DE1994/000766
Authority: WO
Inventors: Hans Erich Gunder; Heide Gunder
Original assignee: Hans Erich Gunder; Heide Gunder
Priority date: 1993-06-11
Filing date: 1994-07-06
Publication date: 1996-01-18
Also published as: DE4319291C1

Abstract

The invention concerns a wind-energy convertor rotor (1) designed to rotate about an axis (6) running in a preferably vertical plane at right angles to the wind direction. In order to ensure high efficiency with a simple design, the invention proposes that the rotor blades (4) are disposed such that their convex surfaces (9), i.e. those facing the direction of lift, are oriented towards the axis of rotation (6) of the rotor.

Description

WIND ENERGY CONVERTER WITH VERTICAL ROTARY AXIS

State of the art

The present invention relates to a rotor for a wind energy converter of the type specified in the preamble of claim 1.

DE-PS 892 130 describes a wind motor with a vertical axis of rotation of the rotor, in which the buoyancy effect of a body with a streamlined profile that moves quickly in the air stream is used for energy generation. The streamlined shape of the profile cross section is to be understood to mean a shape in which the ratio of the thickness of the cross section to the length of the cross section behaves approximately as 1: 3 to 1:10; furthermore, one end should be more or less rounded, while the other end tapers; and finally the side lines of the cross section should be straight or slightly curved inwards or outwards. The latter means that obviously a profile is meant here. which - in relation to its longitudinal axis - is symmetrical. The declared aim of the subject matter according to DE-PS 892 130 is to significantly improve the efficiency in comparison with previously known wind motors mentioned in the introduction to the description of this document. In connection with the reference to the fact that in the event of an increase in speed during the start-up process (of the rotating motor part) to such an extent that the peripheral speed of the wind turbine blades finally becomes greater than the wind speed, this publication states that the wind turbine blades would only ever be hit in such a way by the flow velocity resulting from the wind speed and peripheral speed that the resulting blowing direction results in an air force on the wing, which in each position of the wind turbine wing causes a moment which causes the same in the direction of the Rotational movement acting sense of rotation and therefore contribute to a further increase in speed. - Experiments with wind motors of the type described above disprove this claim. Rather, in the wind motor described in DE-PS 892 130 with a symmetrical profile cross section of the wind turbine blades over a complete revolution of a wind turbine blade, there is a partial reversal of the direction of the buoyancy force acting on the wind turbine blade and thus of the torque acting on the wind turbine blade; this also happens to such an extent that such a wind motor cannot be used for the profitable generation of energy from wind power.

In order to improve the efficiency of a wind turbine with a vertical axis of rotation of the rotor, it is proposed in DE-OS 28 16 026 to use an aerofoil profile known from aircraft - that is, a profile with an asymmetrical cross section - for the blades of the wind turbine, which is above this also characterized by additional and atypical details of the course of the curvature of the profile circumferential line. When analyzing the profile described in this publication, however, it is not clearly recognizable to what extent this profile can be used by an aircraft Profile differs fundamentally. The efforts to significantly improve the achievable efficiency in a generic wind power machine with the details of the profile cross section described in DE-OS 28 16 026, so that such a wind power machine would fundamentally represent a serious alternative to those with a horizontally arranged rotor that can be adjusted in the wind direction , fail due to the reversal of torque on the vanes that occurs with this solution during one revolution of the rotor.

However, the aforementioned DE-OS 28 16 026 already shows a rotor for a wind energy converter, as specified in the preamble of claim 1, namely a rotor which - for reasons of easy and automatic startup - at least three evenly over the circumference of the rotor distributed and arranged at an angle of attack to the tangent of the orbit. Buoyant rotor blades, which have an aerodynamically asymmetrical and unchangeable profile cross section.

An attempt to improve the flow conditions on the wings of a wind energy converter with a vertical axis of rotation of its rotor in the sense of increasing the efficiency is the proposal according to DE-OS 30 18 211. According to this publication, the profile cross section of the blades of the wind turbine is to be changed over a revolution to a predetermined or predeterminable extent, which should result in an improvement in efficiency. Apart from the considerable design effort for this solution, the claimed advantages also appear to be a first rough approximation only if the flow dynamics resulting from the constant adjustment of the profile cross section, which is obviously more difficult than in the case of an unchangeable profile cross section, are neglected and can only be explained theoretically. In any case, this solution could not be implemented in practice either. task

The aim of the present invention is to improve a wind energy converter of the type mentioned at the outset to the extent that — with a consistently simple construction — a considerable improvement in efficiency can be achieved in comparison with known wind energy converters of this type.

solution

To achieve the aim outlined above, the invention specified in the characterizing part of patent claim 1 is proposed.

benefits

Surprisingly, it has been found that - contrary to all previous efforts to achieve a significant improvement in the efficiency of the wind energy converters in question by any kind of basic construction - an arrangement of the rotor blades on the rotor in such a way that the convex pointing in the direction of the lift curved surface areas of the rotor blades facing the geometric axis of rotation of the rotor leads to the desired success. According to the knowledge of the subject matter of the present invention, it is readily possible for the person skilled in the art, and in particular without additional inventive efforts, to select a suitable asymmetrical profile cross section for the rotor blades in accordance with the requirements, also with regard to the local wind speeds the buoyancy and torque on the rotor blade (wind turbine blade) during a revolution, despite the continuously changing inflow angle, maintaining their direction in the intended drive direction of the rotor - at least over the vast majority of a complete revolution of the (one) rotor blade. This With certain profile cross sections, can an angle of attack of <? of the rotor blade in the order of magnitude of 0 °. The angle of attack f is understood to mean the angle between the chord of the profile cross section and the tangent of the circumferential circle. However, especially in the case of high-lift profiles, depending on the special profile characteristics, a more or less large (positive) adjustment of the rotor blade to the tangent of the circulating circuit is appropriate to maximize the efficiency.

Moreover, when selecting a profile cross section that is suitable for the individual application, the person skilled in the art will first determine the high-speed number of the rotor, based on the performance to be achieved, for which the blade depth (for example 0.3 times the diameter of the circulating circle of the rotor blades) is an important factor Parameter is. Taking into account the bandwidth of the wind speeds to be expected, the achievable flow angles (angles between the chord of the profile cross section and the respective flow direction - in particular for the conditions on the windward side of the rotor) are determined; and finally a profile with such an asymmetrical profile cross-section is selected which always delivers positive moments, that is to say acting in the intended drive direction of the rotor, over the fluctuation range of the inflow angles - or at least over the largest part of a complete revolution.

For example, an asymmetrical profile cross section which is well suited for the purposes of the present invention has. the profile GÖ 557 of AVA Göttingen known from the relevant literature ("Results of the aerodynamic testing facility in Göttingen, 1st to 4th delivery"); the well-known Karmän-Trefftz profile, which corresponds approximately to the GÖ 387 profile of AVA Göttingen, could also (still) be used.

A further improvement in the efficiency of the wind energy converter can be achieved if one for the rotor blades - Basically known - multi-part profile is selected. Such a multi-part profile can be, for example, one that is similar to the well-known Kellner-Bechereau profile or the Handley-Page profile.

The rotor blades of the wind energy converter according to the invention can be arranged in a straight line and parallel to the geometric axis of rotation of the rotor according to the proposal according to claim 3, or, as claimed in claim 4, can also be arranged curved to this.

The advantage achieved by the invention of a significantly better efficiency compared to known wind energy converters can in principle also be achieved with asymmetrical profile cross sections in which the buoyancy and torque applied during a rotation of the rotor may possibly return to zero over a smaller angle of rotation ¬ walk or possibly turn slightly over a negligibly small part of the rotation of the rotor blade of 360 °; however, this does not change the basic mode of operation in the sense of the invention. With a view to maximizing the energy to be supplied by the wind energy converter to consumers and / or energy stores, however, the integral of the force acting in the direction of rotation of the rotor should be as large as possible over a revolution corresponding to a 360 ° angle of rotation of the rotor.

Taking into account the high speed of the rotor, the profile cross section and the angle of attack of the rotor blade are preferably selected such that the torque acting on the individual rotor blade does not change its direction over a complete revolution of the rotor. Such a specification not only allows a relatively high energy yield to be expected, but also has the effect that vibrations of the rotor blade (as a result, in particular, of the influence of more or less continuously changing buoyancy forces on the rotor blade) can be kept low. In addition, this torque should preferably be on are as high as possible and vary in strength as little as possible over one revolution of the rotor.

Explanation of the invention using exemplary embodiments

The invention is explained in more detail below with reference to FIGS. 1 to 6 of the drawing.

Show it

1 shows a rotor according to the invention

Side view of wind energy converter,

FIG. 2 shows the rotor according to FIG. 1 in a top view in section according to section line II-II in FIG. 1,

Figure 3 shows another rotor according to the invention

Wind energy converter in a top view in section similar to the illustration in FIG. 2,

Figure 4 shows another rotor according to the invention

Figure 5 shows a symmetrical profile cross section for rotor blades on rotors for wind energy converters, as they belong to the prior art, and

FIG. 6 shows a characteristic field with a comparative representation of the torque coefficients that can be achieved with the profile cross sections of the rotor blades according to FIGS. 1 to 5 as a function of the angle of rotation of the respective rotor blade over a complete revolution of the respective rotor blade. FIGS. 1 and 2 show a rotor 1 according to the invention of a wind energy converter which is not shown in any more detail and which, as is known per se, contains, for example, an electrical generator and electrical / electronic switching and / or regulating means in the region of its static part, which u. a. can also be used to influence the power consumption depending on the speed with regard to easy starting of the rotor and to limit the speed with regard to very high wind speeds.

The rotor 1 carries on a shaft 2 a concentric rotor disk 3. On the rotor disk 3, one end of the rotor blades 4 are attached, the other ends of which are attached to a rotor disk 5, which is also concentric with the shaft 2. The geometric axis of rotation of the rotor 1 formed from the rotor disks 3 and 5 with rotor blades 4 and shaft 2 is denoted by 6.

In Figure 2, the assumed wind direction is indicated by arrows 7, and the direction of rotation of the rotor 1 resulting from the arrangement of the rotor blades 4 is indicated by the arrow 8.

FIG. 2 shows corresponding rotor blades 4 with a highly asymmetrical profile cross section; Such a professional cross section has become known as GÖ 557 from the relevant literature ("Results of the Aerodynamic Research Institute in Göttingen - 1st to 4th Delivery", AVA Göttingen) as a so-called high lift profile. According to the invention, the rotor blades 4 are arranged on the surface of the geometric axis of rotation 6 of the rotor 1 with the convexly curved surface regions pointing in the direction of the buoyancy and designated by 9.

In the case of the representation according to FIG. 2, the chord of the profile cross section of the rotor blades 4, designated 10, is against the tangent of the circumferential circle, designated 11, with the radius 12 of the rotor blades 4 having a fixed one - that is, one during the Rotary movement of the rotor 1 unchanged - angle of attack of about 0 °. As a result of the different flow conditions on the windward side (windward side) of the rotor 1 on the one hand and the windward side (leeward side) of the rotor 1 on the other hand, other (positive) inflow angles for the profile cross section will result on the windward side than on the leeward side. This results from the considerably reduced wind speed on the leeward side - that is to say inside - of the rotor, generally assumed to be about 2/5 of the wind speed on the windward side. Nevertheless, in the case of an arrangement as shown in FIG. 2, a complete rotation, namely over a rotation angle of 360 ° around the geometric axis of rotation 6 of a rotor blade 4, will result in a torque on the rotor 1 which is always acting in the direction of rotation of the drive in accordance with arrow 8 ( see also corresponding characteristic of the torque coefficient assigned to the profile cross section of the rotor blade 4

C m in Fig. 6).

The - as a pure number dimensionless - "torque coefficient" (C), sometimes also referred to as "torque number", represents a measure of the torque which results from the air force acting on the rotor blade with reference to - for the arithmetical treatment - appropriately selected reference axis; in the case of blades with a profile, cross sections corresponding to the rotor blades in question are, for practical reasons, the line perpendicular to the profile plane through the intersection of the chord of the pressure side of the blade or. of the rotor blade (chord) with the perpendicular tangent to its leading edge. The angle of rotation-dependent torque coefficient is directly related to the torque acting on the shaft 2 of the rotor 1 of the wind energy converter.

By adjusting the rotor blades 4 - which can be carried out when the rotor 1 is at a standstill - with an angle of attack P of, for example, + 9 ° with respect to the tangent 11 of the circulating circle, an improvement in the course of the Torque coefficient can be achieved so that the achievable energy yield is correspondingly greater.

FIG. 3 shows a rotor 13 with rotor blades 14 in a manner of representation corresponding to FIG. 2. The rotor blades 14 are an extreme high-lift profile with a profile section divided into two parts. Such profile cross sections with subdivision are known, for example, as a Kellner-Bechereau profile or as a Handley page profile. In the case of the representation in FIG. 3, the rotor blades 14 are set at an angle j ³ of approximately + 9 ° with respect to the tangent 11 of the orbital circuit (angle between the chord of the rotor blade 14 designated by 20 and the tangent 11 of the orbital circuit); the convexly curved surface areas of the rotor blade 14 pointing in the direction of the buoyancy are collectively designated 19. Rotor blades of this type require a more or less large adjustment in the direction of higher positive angles of attack in order to utilize their possibilities with regard to the maximum energy yield of the wind energy converter. FIG. 6 shows in comparison the torque coefficients that can be achieved with the profile cross section of the rotor blade 14 according to FIG. 3 in the event that the rotor blades 14 are turned by approximately + 9 °.

FIG. 4 shows a possible limit case in the sense of the invention, a rotor 15 with rotor blades 16, the profile cross section of which is only slightly asymmetrical. As in the case of the rotor blades 4 or. 14 according to Figures 1 and 2 or. Figure 3 are in any case also the rotor blades 16 arranged in such a way to the geometric axis of rotation 6 of the rotor 15 between rotor disks 3, 5 that they face the convexly curved and designated 17 with the surface areas of the geometric axis of rotation 6 of the rotor 15 pointing in the direction of the lift this are arranged. The profile cross section of the rotor blades 16 - assuming a tangential pitch (angle between the chord of the rotor blade 16 denoted by 21 and the tangent 11 of the circumferential circle of the rotor blades is therefore approximately 0 °) is the Rotor blades 16 - assigned characteristic curve for the torque coefficient can likewise be found in the diagram according to FIG. 6.

Finally, FIG. 5 shows a symmetrical profile cross section 18 with a profile chord 22 for rotor blades on rotors for wind energy converters, which thus runs centrally through the profile cross section of the rotor blade, as they belong to the known prior art, specifically for wind energy converters with such rotor blades whose profile cross section cannot be changed is. The characteristic curve for the torque coefficient for this profile cross section can also be found in the diagram according to FIG. 6, specifically for an angle of attack Q of 0 °.

According to the above description, it is clear that it is not absolutely necessary that the characteristic curve - to be determined arithmetically or empirically - for the torque coefficient of a profile cross section over a complete revolution of the relevant rotor or. Rotor blade is always on only one side of the abscissa of the diagram; rather, in the case of a - with regard to maximizing the energy conversion unfavorable - special arrangement and design of the rotor blades, a slight change in the torque coefficient in relation to a covered rotation angle of 360 ° can be accepted without thereby reducing the scope of the invention would already leave. Of course, preference is given to an embodiment in which, on the one hand, there is no change in direction of the forces acting on the individual rotor blade, in which, moreover, the course of the characteristic curve for the torque coefficient (because the alternating forces on the rotor blade are as small as possible) is as balanced as possible and in which the integral of the torque coefficient is finally used is as large as possible over one revolution of the rotor.

REFERENCE DATE

1 rotor

2 shaft (of rotor 1)

3 rotor disc (of rotor 1)

4 rotor blade (of rotor 1)

5 rotor disc (of rotor 1)

6 axis of rotation - geometric - (of the rotors)

7 arrows (wind direction)

8 arrow (direction of rotation of the rotor)

9 surface area (of the rotor blade 4)

10 chord (of the cross section of the rotor blade 4)

11 tangent (to the orbit of the rotor blades)

12 radius (of the circulation circle of the rotor blades)

13 rotor

14 rotor blade (of the rotor 13)

15 rotor

16 rotor blade (of rotor 15)

17 surface area (of the rotor blade 16)

18 profile cross section - symmetrical -

19 surface area (of the rotor blade 14)

20 chord

21 chord

C m torque coefficient

0 ° to 360 ° - angle of rotation of the rotation of a rotor blade 4, 14, 16 or (18) about the geometric axis of rotation 6

Claims

PATENT CLAIMS

1. Rotor (1) for a wind energy converter with an axis of rotation (6) of the rotor (1) which is in a plane that is perpendicular to the direction of the wind and preferably runs vertically, which is distributed at least three evenly over its circumference and at an angle of attack P to the tangent (11) of the revolving circle arranged, buoyancy-producing rotor blades (4) with aerodynamically asymmetrical, unchangeable profile cross-section, characterized in that the rotor blades (4) with the convexly curved surface areas (9) of the geometric axis of rotation (6) pointing in the direction of the buoyancy ) of the rotor (1) are arranged facing this.

2. Rotor according to claim 1, characterized in that a multi-part profile is selected for the rotor blades (14).

3. Rotor according to claim 1, characterized in that the rotor blades (4, 14, 16) are arranged in a straight line and parallel to the geometric axis of rotation (6) of the rotor (1, 13, 15).

4. Rotor according to claim 1, characterized in that the rotor blades (4, 14, 16) curved to the geometric axis of rotation (6) of the rotor (1, 13, 15) are arranged extending. Rotor according to claim 1, characterized in that the profile cross-section and angle of attack of the rotor blades (4, 14, 16) are selected such that the torque acting on the individual rotor blade (4, 14, 16) over a complete revolution of the rotor (1, 13, 15) does not change direction.