CA1141668A

CA1141668A - Wind turbine of cross-flow type

Info

Publication number: CA1141668A
Application number: CA000337120A
Authority: CA
Inventors: Olle Ljungstrom
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-10-06
Filing date: 1979-10-05
Publication date: 1983-02-22
Also published as: DK414679A; SE7810504L; SE414073B; US4329116A

Abstract

ABSTRACT

Wind turbine of cross-flow type with constant or cyclically adjustable blade angle. The vanes (2) consist of one or more sets o-f blades with arched or, in sections, straight extension in longitudinal direction, comprising several substantially parallelly extending blades (3, 4, 8), the spacing of which from one another is fixed by means of a number of spacing elements (5, 9) having aerodynamic profiling and providing a spacing of the order of magnitude of between 1/2 and 3 times the blade chord.

Description

l The presen-t invention relates to a wind turbine of cross-flow type with fixed vane angle or in known manner cyclically adjustable vane angle.
An object of the invention is to improve such a wind turbine so as to augment the capacity of the vanes in absorbing load in order firstly to obtain increase of efficiency when operated at high wind velocities and in gusts (region of risk of blade stabling) and secondly to protect the vanes with stopped turbine with inoperative vanes in hurricane wind (risk of breaking of vanes by denting).

In the prior devices such as disclosed in United States Patent 4,115,032 issued September 1978 to Lange, the vanes consist of an integral single blade. Single blades are delicate and relatively inefficient at high wind speeds.
In accordance with the present invention there is provided a wind turbine of cross-flow type with fixed vane angle or in known manner cyclically adjustable vane angle, characterized in that the vanes rotating peripherally about the rotor shaft consist of one or more vanes or sets of blades with curved or, in sections, straight extension in longitudinal direction, comprising several substantially parallelly extending blades, the spacing of which from one another is fixed by means of a plurality of spacing elements having aerodynamic profiling and providing a spacing of the order of magnitude between l/2 and 3 times the blade chord.
The invention is illustrated by way of example with reference to the accompanying drawings wherein, Figure 1 shows in Fig. la a side view of a wind turbine according to the invention, whereas Figures lb - ld are ~t~ ' ' 1 cross-sections as for e~ample essentially along line 1-1 of Fig. 1 illustrating three different shapes of vanesO
Figure 2 shows in Fig. 2a a side view of an embodiment with triple vanes, Figures 2b and 2c being cross-sections through dif~erent shapes of vanes and taken essentially along line 2-2 of Fig. 2.
Figure 3 shows in FigO 3a a side view, 3b an end view and 3c a plan of a wind turbine according to the invention with balance weights.
Figures 4 and 5 show cross-sections through turbine vanes.
In the embodiment of Figure la a rotatable rotor shaft 1 is mounted in conventional manner in a stand not denoted specifically. At least one vane having an arched or in sections straight extension in longitudinal direction is arranged rotatably with or about the rotor shaft. The vane or set of blades 2 is, according to the invention, sub-divided into a plurality of substantially parallelly extending blades 3, 4 the spacing of which from one another is ~ixed by means of a number of spacing elements 5 having an aerodynamic profile and providing a spacing of the order of magnitude of 1/2 to 3 times the blade chord. Bxamples of various blade types are shown in Figures lb-lc, it being possible also to arrange the blades in each vane with a minor angular displacement 5a between the chord planes, as is shown in Figure lc. Figure ld shows how the blades have been imparted a displacement 7 also in the direction of the chords. In the embodiment shown in Figure la, the securing of the vanes onto the tower or rotor shaft 1 is effected by means of several radial braces or stays, in the illustrated case three such braces 12, 13, 14.

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1 Figure 2 shows an arrangement similar to that shown in Figure 1 with a rotor shaft 1 and a vane or set of blades 2 rotating about said s~aft and secured to the rotor shaft 1 by several braces 15, 16, 17. The set of blades 2 consists in the embodiment of Figure 2a of three blades 3, ~, 8 which are shown in Figures 2b and 2c. In Figure 2b, reference numeral 9 denotes the spacing element for fixing the blades, and the blades have been given also a displacement 10 in the direction of the chord. This displacement has been denoted 11 in Figure 2c.
The shape shown in Figures 1 and 2 of the wind turbine vanes according to the invention results in an improvement of the load absorption by the set of blades, both when in operation in strong wind and in gusts and also when the turbine is stopped with inoperative blades in a hurricane.
The specific embodiments with angular differences between the blad~s and/or a displacement in the chord direction renders possible to trim the blades to the best possible gliding ratio (L/D ratio) within a large range of wash in, minimum drag and high dynamic rising and therewith high driving power component for the biplane vane, the triplane vane, as well as an additional improvement of the load absorption by the set of blades when exposed to high wind velocities (low numbers of revolutions of the turbine) and on strong gusts, while at the same time avoiding stalling and thereby improving the transfer of power to the turbine shaft.
The arrangements of biplanes and triplanes with spacing elements are suited for a predetermined total blade area

- 3 -1 of the turbine -to reduce the exposed blade surface which acts as load on the set of blades when the turbine has been stopped during a hurricane, as well as by the spacing braces substantially to reduce the risk of buckling of blades in a hurricane, thereby rendering possible considerably to reduce the total weight of the vane or set of blades. The securing of the blades onto the tower which is designed to be effected with three or more radial braces in both upward and downward directions such as the braces 12, 13, 14 and 15, 16, 17, may be devised as a rigid lattice work. As is evident from Figure 3, the set of blades 2 which by means of the braces 12, 13, 14 is secured to the tower 1 can be balanced by balance weights 18 suspended on brackets 19, 20, 21. The set of blades may also in known manner be devised for function as pendulum and equipped with dampers and springs, as, for example, shown in applicant's co-pending Canadian application, Serial No. 337,119, filed October 5, 1979.
Figure 4 shows that each blade 3, 4, 8 in a set of blades 2 can be subdidivided into two segments 22, 23 which at the outset had been manufactured straight with constant cross-section and were joined together to curved vane shape in the mounting operation and held together by assembling elements 24. In Figure 5 the blade is composed of three segments having constant cross section and denoted 25, 26, 27, which in the same manner have been assembled to curved vane shape when joined together to the final shape of the set of blades. Of course, the vane may also be composed of more segments than three.

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1 It is obvious tha-t the shown and described embodiments are examples only of realisation of the inventive idea and that the same can be varied within the scope of the subsequent claims.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Wind turbine of cross-flow type with fixed vane angle or in known manner cyclically adjustable vane angle, c h a r a c t e r i z e d in that the vanes (2) rotating peripherally about the rotor shaft (1) consist of one or more vanes or sets of blades with curved or, in sections, straight extension in longitudinal direction, comprising several substantially parallelly extending blades (3, 4, 8), the spacing of which from one another is fixed by means of a plurality of spacing elements (5, 9) having aerodynamic profiling and providing a spacing of the order of magnitude between 1/2 and 3 times the blade chord.

2. Wind turbine according to claim 1, c h a r a c t -e r i z e d in that each of the vanes or sets of blades (2) with two or more blades (3, 4, 8) is designed with a minor angular difference between the chord planes and/or a dis-placement in the chord direction (7, 10, 11).

3. Wind turbine according to claims 1 or 2, c h a r a c t e r i z e d in that the securing of the blades onto the rotor shaft (1) is devised with three or more radial braces in upward and downward direction, res-pectively (12, 13, 14 in biplane set of vanes 15, 16, 17 in a triplane set of vanes) arranged as a rigid lattice work.

4. Wind turbine according to claims 1 or 2 c h a r a c t e r i z e d in that each of the sets of blades is balanced by means of balance weights (18) sus-pended from brackets and otherwise devised for function as pendulum, and equipped with dampers and springs.

5. Wind turbine according to claims 1 or 2 c h a r a c t e r i z e d in that each of the blades (3, 4, 8) in a vane or set of blades (2) is devised subdivided either into two segments (22, 23) at the outset manufactured straight with constant cross-section and joined together to curved vane shape in the mounting operation and held together by assembling elements (24) or into three or more segments with constant cross-section (25, 26, 27) joined together in the same manner to curved vane shape by being assembled to the final shape of the vane in the mounting operation.