WO1995020104A1

WO1995020104A1 - Fabrication of aerodynamic profiles

Info

Publication number: WO1995020104A1
Application number: PCT/GB1995/000101
Authority: WO
Original assignee: Torres Martinez, Manuel
Priority date: 1994-01-20
Filing date: 1995-01-19
Publication date: 1995-07-27

Abstract

A method of fabrication of aerodynamic profiles for aerogenerator or aerodyne blades and the blade thus obtained, which consists of the covering separately of moulds or mandrels (2) with composites of fibres impregnated with synthetic resins, so that later and once these mandrels (2) have been covered they may be joined together by means of transversal fixings (12), the assembly thus formed being arranged between two layers (15 and 16), also formed from a composite of fibres impregnated with synthetic resins, with the arrangement of all this between a pair of moulds (3 and 4), in order to conclude with a method of curing by which is obtained a monocoque profile determining the general body of the corresponding blade.

Description

FABRICATION OF AERODYNAMIC PROFILES

DESCRIPTION TECHNICAL FIELD

The invention relates to a method of fabricating aerodynamic profiles e.g. for aerogenerator or aerodyne blades, and to blades thus obtained.

The depletion of some sources of energy and technological progress, as well as other causes of an ecological nature, factors of dependency, etc, have caused serious consideration of the use of tradition energy sources, for example aeolian energy.

BACKGROUND ART Thus, in different parts of the world, and above all in the more developed countries, wind farms are being installed, made up from a multiplicity of towers which make use of the energy of the wind in order to generate electricity, for this reason being called aerogenerators. In the said aerogenerators, one of the principal components are the blades which are used to take advantage of the force of the wind. These blades must comply with the requisites of minimum weight, high mechanical resistance, flexibility, adequate aerodynamic coefficient, etc; characteristics which, in short, correspond to the basic conditions required by the blades of aerodyne vehicles, as in the case of helicopters, or even the wings of aeroplanes.

The ideal materials for the fabrication of these blades are fibres impregnated with synthetic resins, such as those known under the name of composites, but in the realisations existing until today an efficient solution has not been achieved, both because of the complexity of the fabrication processes, and because of the lack of precision in many cases of the final results which are obtained. Moreover, the complexity of the fabrication processes are aggravated by the actual greatly increased dimensions which these blades have and which make their handling appreciably difficult. On the other hand, the use of these materials requires a very precise compression of the fibres in order to obtain the corresponding cloths in the fabrication, and a final process of hardening in an autoclave, until which point the material has a softened composition which makes its handling even more difficult if possible, above all when dealing with the fabrication of blades of a great length.

To this effect, methods of fabrication of these elements by fibres impregnated with synthetic resins are already known in which the structure of the elements which is formed has stiffening ribs, between which are defined spaces, in which are introduced solid bodies, generally prismatic, of a material of greater coefficient of expansion than the composite, as for example aluminium. This is the case in Spanish Patent 527.745 and European Patent number 217.315.

As a result of which on heating the composite in order to cure it, the aforementioned bodies incorporated in the interior expand, giving rise to the compression of the internal faces of the spaces.

This method nevertheless has in its turn two important inconveniences, which are: - The necessity to calculate with absolute precision the expansions of the bodies in the interior, and their measurements, since deviations which are greater may lead to the bursting of the element being shaped; while deviations which are smaller will mean that the necessary compression is not produced.

- The necessity of extracting these additional bodies from the interior of the shaped element, which is very complicated, making it necessary to make each of the said bodies in a complex manner, in various parts or sections. DISCLOSURE OF INVENTION

There is now proposed a method, by means of which the fabrication of these aerodynamic profiles is achieved in a tubular monocoque form, without the indicated inconveniences. This method the object of the invention is based on the fabrication of the aforementioned profiles with the help of various moulds or mandrels in order to shape the different internal cavities according to the structural design of said profiles, and two corresponding moulds to shape the respective external faces.

The internal moulds or mandrels are provided with a covering in an elastic material which may be expanded by the action of heat, whose application is already known in methods such as those laid out in German Patent DE-30 03 552 C2, European Patent 0217315, or Spanish Patent 523.394.

On said mandrels is incorporated a composite of fibres impregnated with synthetic resins, formed by two complementary halves with chamfered edges which overlap each other. Subsequently all the mandrels are grouped together by means of guiding and gripping bars. In a later phase, two layers of a composite also formed from fibres impregnated with synthetic resins are incorporated on the faces of the assembly. The compression of the assembly is achieved by means of autoclave curing, with the incorporation of a surrounding cover, by means of which the said assembly is compressed by an internal vacuum. There results thus a method which permits the attainment of a simple method of fabrication of wind blades or other similar aerodynamic profiles for application in aerodyne vehicles, with a suitable weight and the precise composition to receive and transmit favourably the forces which they have to withstand, making the said method suitable also for the obtention of the aforementioned profiles by means of fabrication in series.

In the particular case of the application of the aforementioned profiles, such as aeroplane wings, both for the front wings and for the rear stabilizers, there is foreseen the inclusion of the longitudinal end of the profile, by means of which the fastening to the structure of the application must be established, with a front intermediate cavity between the respective constituent covers of one or the other face of the profile, for the fitting by means of the said cavity on a fixing element and the respective fitting to the same by rivetting or screwing of the parts which are superimposed on the referred element.

In this way, the fixing of the front wings of the plane may be effected on a flat element of the structural frame, within the fuselage, while the respective rear altitude and directional stabilizers may likewise be fixed onto a T shaped element of the structural frame, also within the fuselage.

BRIEF DESCRIPTION OF DRAWINGS The invention is diagrammatically illustrated, by way of example, in the accompanying drawings, in which:-

Figure 1 depicts a conventional aerogenerator, but provided with blades obtained in accordance with the present invention;

Figure 2 shows in enlarged form one of the blades of the aerogenerator in Figure 1, with the part of its fixing flange, in cross section, and various details corresponding to the transverse fixing, taken at different longitudinal points of the said blade;

Figures 3 and 4 are enlarged views of a transversal cross section of the blade and show respectively the pieces of the front and rear edges, detached and attached with respect to the constituent profile of the body of the blade; Figure 5 is a perspective of the aforementioned constituent profile of the body of the blade;

Figures 6 and 7 are views in cross section of a mandrel for the shaping of the internal cavities of the profile to be obtained. In Figure 6 the enveloping composites are in the positioning phase and in Figure 7 they are already arranged on the aforementioned mandrel;

Figure 8 is a perspective view of the mandrel, in the layout in Figure 6; Figure 9 shows the method of grouping the different mandrels for the shaping of the profile to be obtained, by means of fixing bars;

Figure 10 is a view of the grouped assembly of this set of mandrels for the shaping of the profile; Figure 11 is a perspective view corresponding to the assembly in the previous figure;

Figure 12 is a view corresponding to the layout of the grouped assembly of the mandrels on the corresponding lower mould for the positioning of a side layer of composite; Figure 13 is a view corresponding to the layout of the grouped assembly of the mandrels between the two lower and upper moulds for the positioning of the layers of composite on the sides of the said assembly;

Figure 14 is a view of the front assembly covered with a hermetically sealed layer for compression during autoclave curing; Figure 15 is a perspective view of the assembly covered in accordance with the preceding figure, for the shaping phase of curing;

Figure 16 shows the perspective of an aeroplane whose wings and rear stabilizers are made in accordance with the invention, and

Figure 17 shows a schematic cross section in front view of an aeroplane conforming to the preceding embodiment. Clarifying Details

1. Aerodynamic blades

2. Mandrels

3. Lower mould

4. Upper mould 5. Aerodynamic profile

6. Edge piece

7. Edge piece

8. Elastic covering

9 & 10. Composites of fibre impregnated with synthetic resins

11. Overlap

12. Fixing bars

13. Gripping nut

14. Fibre filling 15 & 16. Composites of fibre impregnated with synthetic resins

17. Elastic hermetic surround

18. Sealing cord 19 . Wings

20. Rear stabilizers

21. Aeroplane

22. Wing fixing element 23. Altitude rudder (Elevator?)

24. Direction rudder

25. Stabilizer fixing element

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a method of fabrication of aerodynamic profiles of the tubular monocoque type, especially for aerogenerator blades (1) such as that in Figure 1, and likewise for aerodyne blades or wings, as for example in helicopters and aeroplanes.

In Figure 2 is shown a blade (1), in accordance with an example of a practical embodiment. This blade (1) and more particularly the aerodynamic profile (5) which constitutes its general body is made with the help of moulds or mandrels (2), by means of which are shaped the different internal cavities of the said profile (5), using moreover two moulds (3) and (4) for the shaping of the external faces.

Thus and in accordance with the example shown in Figures 3 and 4, for the obtention of a profile (5), which may be joined to respective constituent pieces (6) and (7) of the aerodynamic edges of a blade, a mandrel (2) is used for each longitudinal cavity of the aforementioned profile (5). The said mandrels (2) are formed from a basic body which may be metallic with a high expansion coefficient, as for example aluminium, or even a synthetic material similar to that of the piece to be made, the choice of one material or another being dependent upon the precision and the quality required of the profile (5) to be obtained.

On the basic body of each mandrel (2) is arranged a covering (8) of an elastic material with a high expansion capacity under the effect of calorific action; on which covering, in accordance with the recognised method, are incorporated both composites (9) and (10) which, complementing each other by means of an overlap (11) of their chamfered edges, form a surround over the aforementioned outer covering (8) of the mandrel (2), as can be seen in Figures 6, 7 and 8.

The said composites (9) and (10) are shaped in an automatic process on the actual mandrels (2), an operation which may be achieved by the "Hot Forming" system already known in the composite fabrication industry, this formation of the aforementioned composites (9) and (10) being achieved from stratified layers of reinforced fibres, supplied in tapes with unidirectional fibres impregnated with synthetic resins, the direction of the fibres of the said layers being lined up in the appropriate way in order to obtain the required resistance to twisting and flexing, giving to these layers the shape of an extended sheet which covers the surface of the mandrels (2) . The set of the mandrels (2), each of them being surrounded by the corresponding composites (9) and (10), is grouped in a fixed assembly by means of guiding and fixing bars (12), the first lower mandrel (2) being arranged, as can be seen in figure 9, in order to incorporate on it the bars (12) and then in superposition the rest of the mandrels (2), which are provided for the said assembly with holes calibrated with the precision necessary in order to assure its correct positioning on the assembly. Once the associated assembly of all the mandrels (2) has been effected in this manner, the assembly is compacted by tightening the nuts (13) at the ends of the bars (12) at the precise measurement to obtain a rigidity which permits the turning and movement without alteration; this connection filling, as can be seen in figure 10, the cavities and grooves which remains between the different mandrels (2) due to the radius of the edges, with a filling (14) of threads and fine longitudinal fibres, of the same material as the composites (9) and (10) and also impregnated with synthetic resins.

Next the assembly is placed supported laterally on a lower mould (3), on which has been previously arranged a layer of composite (15), as can be seen in figure 12; the other layer of composite (16) being arranged on the other lateral face of the aforementioned associated assembly of the mandrels (2), in order then to arrange an upper mould (4), as can be seen in figure 13. The composites (15) and (16) are composed, in the same way as the composites (9) and (10) which line each of the mandrels (2), of different stratified layers of tapes with unidirectional fibres, coming from spools with impregnated fibres, the realisation of all the aforementioned composites being able to be achieved by an automatic process, as for example, as for example by means of the taping machine which is the object of Spanish patents

9302506 and 9402102 of the same proprietor as the present invention.

The number of layers of the aforementioned composites

(15) and (16), as well as the direction of the component fibres, will depend in each case on the design of the aerodynamic profile (5) to be made, and on the maximum forces that the same must withstand.

And when in their turn the composites (9), (10), (15) and (16) have a large size which does not allow manual handling, their transference and turning may be achieved by means of a system as in Spanish Patents 9302156 and 9401997 of the same proprietor as the present invention.

All the preceding assembly, formed by the block of the united mandrels (2) and the moulds (3) and (4), with the composites (15) and (16) is covered by an elastic surround (17), in a material such as silicone, which is sealed hermetically in the shape with an elastic cord (18), as can be seen in Figure 14; a vacuum being made in the inside in order to extract the air which is in contact with the fibres, with the aim of avoiding bubbles and the like. The vacuum is made from the upper face of the lower mould (3), to the upper part of the mould (4), which creates a pressure equivalent to the maximum level of the vacuum made, said pressure initiating the method of compression between all the walls which form the profile (5) to be made, which is effected in a uniform manner, helped by the elastic covering (8) of the mandrels (2).

The assembly thus formed is submitted to a method of autoclave curing, in such a way that the pressure on the composites (9), (10), (15) and (16) increases progressively in line with the increase in temperature, so that in a first phase the impregnating resin becomes more fluid and the elastic covering (8) of the mandrels (2) is expanded, with which the fibres of the composites adapt themselves with a uniformity of tension and compression, until the process of polymerisation hardens the resin, a piece being obtained without internal stresses in the fibres, with the guarantee of a high quality.

Once the process of autoclaving is finalised, it is enough to unmould, removing the surrounding cover (17) and the moulds (3) and (4), as well as the bars (12), in such a way that on cooling the assembly, the consequent contraction which the elastic material (8) of the mandrels (2) undergoes, leaves these free so that they may be extracted without any difficulty from the interior of the finished profile (5) .

In the case of this particular application of the said profiles (5), for the constitution of the wings (19) and/or of the rear stabilizers (20), in aeroplanes (21), it is foreseen that these profiles (5) are made with a front cavity defined between the two constituent layers of the faces of the profile (5) in the end intended for the fastening on the corresponding aeroplane structure (21) .

In this way, as can be seen in Figures 16 and 17, the front wings (19) of the aeroplane (21), may be incorporated by means of their coupling on a horizontal flat element (22), solidly attached to the actual structural frame of the aeroplane (21); its fastening to the extension of the faces of the profile (5) which are superimposed on the said element (22) being achieved by means of screwing or rivetting onto the actual element (22) .

Thus, said wings (19) are united to the structure of the aeroplane (21) within the fuselage of the latter, which makes a very resistant constructional arrangement suitable for the aerodynamic character which is required.

The rear stabilizers (20), which have the elevators (23) and the corresponding directional rudder (24) may be incorporated in their turn, from a profile (5) of the indicated characters, by means of fixing on an element (25) with a T section, solidly fixed in its turn to the structural frame of the aeroplane (21) ; each one of the said stabilizers (20) being incorporated by a recess on one of the branches of the aforementioned element (25), likewise beneath the fuselage, this assembly being assured in its turn by means of screwing or rivetting of the overlapping parts in the recess. INDUSTRIAL APPLICABILITY The present invention thus provides an improved method king aerodynamic profiles.

Claims

CLAIMS 1. A method of fabrication of aerodynamic profiles for blades for aerogenerators or aerodynes, in which the blade or corresponding element to be shaped is made with fibres impregnated with synthetic resin which are arranged over moulds with a high coefficient of expansion, these moulds being able to be covered with an elastic material; characterised in that such moulds are made up from elongated pieces or mandrels (2), each one of which, in a first phase, is covered with two composites (9) and (10) of fibres impregnated with synthetic resins; in that in a second phase the different mandrels (2) already covered by the composites (9 and 10) are attached solidly together, by means of transversal fixing means, by which, the whole assembly of mandrels (2) forms a single block which may be turned and handled; in that in a third phase, the block formed by the mandrels (2) and their transversal fixing means is situated between two layers (15 and 16), each one of them formed by a composite of fibres impregnated with synthetic resins, and all this between the corresponding pair of lower (3) and upper (4) moulds; in that finally all this assembly is submitted to a method of curing, from which is obtained the constituent tubular monocoque profile (5) of the general body of the corresponding blade (1) .

2. A method of fabrication of aerodynamic profiles for blades for aerogenerators or aerodynes in accordance with claim 1, characterised in that the two composites (9 and 10) which cover each mandrel (2) are made up in two complementary halves, with chamfered edges which are positioned next to each other in an overlap (11) .

3. A method of fabrication of aerodynamic profiles for blades for aerogenerators or aerodynes in accordance with claim 1 or claim 2, characterised in that the transversal fixing means which are solidly attached together to the different mandrels (2) are made up from bars (12) which pass through the mandrels (2) through existing calibrated orifices in these latter, these bars (12) having gripping means at their ends so as to make a firm attachment of the different mandrels (2).

4. A method of fabrication of aerodynamic profiles for blades for aerogenerators or aerodynes in accordance with claims 1 to 3, characterised in that the cavities defined between the contiguous edges of the different mandrels (2) once these are covered by the composites (9 and 10) and joined with the fixing means (12), are covered with a filling (14), formed from fibres of the same material as the composites (9 and 10) .

5. A blade for aerogenerators or aerodynes in accordance with any preceding claim, characterised in that in the composition of wings (19) and/or stabilizers (20), for aeroplanes (21), the monocoque profile (5) has the configuration of a front cavity defined between the two constituent layers of the larger faces of the profile, on the end intended for its fixing, with which the fixing of the wings (19) is achieved on the edges of a flat element (22) of the corresponding aeroplane structure (21), and the fixing of the stabilizers (20) on the respective branches of a T shaped element (25) of the same structure of the aeroplane (21), inside the fuselage, the fixing being achieved by engagement of the profiles (5) on the said elements (22) and (25) and fixing by means of screwing or rivetting of the superimposed parts.