DE8803598U1 - Device for reducing the induced drag on rotor blades of wind turbines - Google Patents

Description

Description:

Device for reducing the induced drag on rotor blades of wind turbines.

It is known from fluid dynamics that the pressure difference between the pressure and suction side of a profile at the ends of wings or rotors causes strong vortex fields, so-called edge vortices, which also cause a lot of flow noise. This flow, also known as induced drag, increases proportionally to the square of the lift coefficient.

The induced drag reduces the pressure difference between the suction and pressure sides that creates lift. In order to limit the effects of this property of wings or rotors, end plates, winglets or deflection edges are installed on the wing tips, which, however, lead to an increase in flow resistance. In order to avoid tip vortices, it is also known to arrange special flaps or slats on the leading or trailing edges of the wing, through which the flow is sucked in on the underside of the profile and fed to the upper side of the profile. This energy supply increases the flow speed on the upper side of the profile.

The invention consists in creating a device which makes it possible to reduce the induced resistance without high constructional and manufacturing expenditure.

According to the invention, the problem is solved by arranging several blades in profile form at the transition zone of a rotor blade at a certain angle of attack to each other, flow energy from the underside 14 of the individual blades is brought to the upper side 15 of the blade by flow compression between the blades 13 and expands there, which leads to a flow acceleration on the upper side of the blade (Fig. 6)

As a result, the separation point of the oriental section is raised to the wing trailing edge 16 and the pressure on the wing upper surface 15 is increased, which also leads to a splitting of the edge vortex into individual vortex braids and thus the Qs

induced drag'WProfn Keduzffert. The invention also leads to a reduction in flow noise on the wing.

Further features of the invention are explained in more detail below with reference to the rotor shown in the drawings.

It shows:

Fig. 1 a normal rotor blade in a side view with indication of the transition zone and attached slotted wing

Fig. 2 the split wing in a side view (windward side) from the transition zone

Fig. 3 the slit wing from the front (flow inlet) Fig. U the slit wing from the back (flow outlet)

Fig. 5 A to E

Top view of the wing in horizontal section plane at the transition zone section AA to &tgr;&khgr;&khgr;&khgr;&agr;. Wing end section EE.

Fig. 6 Representation of the flow pattern on the slotted wing according to the inventor.

By means of an embodiment of the invention, the device for achieving the desired pressure ratios is characterized in that, in the case of a rotor blade 11 (Fig. 1), after 70% of its wing length, 5 individual wings in profile form (Fig. 5 A) are integrated into its profile at this point (transition zone 12) and are twisted along their length in an indeterminate ratio in such a way that

a. at the transition zone 12 (Fig.1) the wings 1-5 (Fig.5A) a gap of minimal width and uneven position widens towards the wing end to a gap of maximum width and symmetrical position 6-10 (Fig.5 E)

«(•(Kl

b. at the transition zone 12 (Fig. 1) the position of the wing profile from a negative twist angle of less than 30 Orad (Fig. 5 A) towards the wing end is aligned in an indeterminate relationship to a positive twist angle of less than 10 Orad 6-10 (Fig. 5 E).

According to the inventor, the position and torsion of the individual profiles in other systems and turbomachines can also be rotatably mounted by changing the angle of attack to adapt to the ideal flow at the base point, in order to optimize or regulate the performance of various turbomachines.

The device according to the invention for reducing the induced resistance can be manufactured in a relatively economical manner using fiber composite materials and can be attached to the transition zone (12) using fitting bolts and screw connections.

The invention is particularly economical for wind turbine rotors, since the speed at the blade tip is particularly high in high-speed rotors used to generate electricity due to the rotational movement, and these represent a large part of the total effective rotor area. The invention enables approximately 15-20 % higher performance to be obtained from the same rotor area than with normal rotor blades. The relative additional costs of producing a slotted blade are paid off in a relatively short time (depending on the location) due to the higher power output3.

The invention has the positive side effect of reducing the flow noise, which is often perceived as disturbing in wind turbines.

Claims (2)

»* «· ·· It ·&Igr; ti III« ·&igr;&igr; «it« I Il I · I ■ ■ Il Il I I III«· I Il ti I II I IfI I ( I I I)II Il III! Applicant: Oerd Seel Schloßatr. 72 Walzbachtal 1 Title: Device for reducing the induced drag on rotor blades of wind turbines Protection claims 1. Device for reducing the induced drag, characterized in that in a normal rotor blade (11) of a wind turbine, from about 70% of its blade length (transition zone 12), 5 individual blades are integrated into its profile at this point (1-5) and are twisted in such a way that a. in the transition zone (12) the wings expand from a gap of minimal width and uneven position (1-5) towards the wing end to a gap of maximum width and even position (6-10). b. at the transition zone (12) the wings are aligned from a negative twist angle (1-5) of less than ?0 degrees towards the wing end in a certain ratio to a positive angle of less than 10 degrees (6-10). 2. Device according to claim 1, characterized in that the individual profiles are rotatably mounted at the base of the transition zone (12) or are arranged to be pivotable by an adjusting device in a manner known per se.