SE441823B - PROCEDURE FOR THE PREPARATION OF WINDOWS - Google Patents

Description

7910561-0 'z to produce a desired band path on the core during the rotation of the core. bridging or winding of a concave surface on the core, does not occur on cylindrical constructions but can be expected to occur with a wide wind turbine blade due to rotation of the blade and its root-to-tip design, which is concave near the root. With a fiber winding angle of 30-400, the concave shape is also obtained along the desired belt path. If a section is cut along the strip web, this section is bridged if there is a cavity between the core and the fiber pulled tightly over the same. The most obvious problem with bridging is the cavities that weaken the structure. These can be filled with glass and resin to form a solid structure, but this gives increased weight at a higher cost. bridging can give weak fiber compression whereby the resin / glass ratio increases and its strength decreases. Loss of fiber control means that an unsupported band tends to form a rope or to separate.

The winding angle of the fibers is determined as required by the shape of the blade and the load thereon, and the angle may vary in the longitudinal axis direction of the block. Conventional winding technology normally involves several winding passages, whereby layers of fibers are built up to form the bearing surface. In some embodiments, some parts of the bearing surface or blade may have more fiber layers than others, in rotor blades it is e.g. It is common to apply many more fiber layers at the inner end, or hub end than at the outer end in order to improve the structural strength and absorb loads.

In many embodiments a so-called winding or adopting ring at the blade ends, the fibers being wound around the ring during manufacture and cut off at the blade ends after manufacture. This technique is also well known. In some embodiments, the fibers in different passages may be of different composition and different passages may use fibers of varying thickness or different intervals or angles. A common technique is to let one winding passage go in a right-handed spiral path and the next passage in a left-handed spiral path.

For large blades, a solid surface is normally used as the core over which the fibers are wound. The core can e.g. be a plywood frame covered with metal wires and a plaster filler or of aluminum or plastic. In some embodiments a rib section is arranged inside the rotor or bearing surface for increased strength and with core sections arranged next to the rib. during manufacture, the core can be removed from the inside of the bearing surface s 7910361-0 or left as reinforcement. Although the invention is described below in connection with glass fibers covered with resin or another epoxide matrix, it is obvious that other types of fibers and / or matrices can also be used and that single or multiple fibers are also useful. bridging can sometimes be prevented by varying the winding angle, but this is not always feasible as changing it also changes the strength of the rotor and the load-bearing capacity.

Another solution is to modify the bearing surface shape, but this has a great effect on the entire system's ability to function and does not always mean that bridging does not take place at a certain winding angle. A better solution is to determine in advance, through the shape geometry, the surfaces of the core where bridging will take place, and adapt the shape geometry and the core thereto to prevent bridging. In other words, adapting a bearing surface to prevent bridging means that the shape is changed slightly so that it is not concave with any belt path.

Carrying area changes due to bridging problems occur primarily near the trailing edge of root stations and result in a negligible impact on aerodynamic performance.

The present invention therefore aims to provide a method which prevents or reduces bridging in the production of large fiber-wound rotor blades.

Furthermore, a method is determined for determining where bridging will take place when a composite fiber is wound over a core or other profiled structure.

Furthermore, a method for minor changes in the shape of the core or structure, whereupon a fiber composite is wound, is intended to prevent bridging.

According to the invention, a method is provided for determining where bridging will occur in the manufacture of a support surface by winding a composite fibrous material around a core, and for modifying the profile of the support surface to avoid bridging. The method comprises that the shape of the bearing surface is determined thereby by a certain coordinate system, e.g. cylindrical coordinates, and that representative coordinate points are selected on the bearing surface at fixed intervals. As an example, a set of coordinate points is given by the intersection between a plurality of longitudinal planes, called stringers, each in a plane containing the winding axis, and a plurality of planes called stringers or stations, which are perpendicular to the winding axis. At each coordinate point, two straight lines are constructed coinciding with the fiber winding plane, where the first line begins at the selected coordinate point and extends _ __ .__.._._._._._...___._...... ...._._._..-.- .. .79'iÜš61-0 4 in the fiber winding direction and coincides with the fiber winding plane, and where the second line begins at the selected coordinate point and extends coincident with the fiber winding plane but opposite to the fiber winding direction, i.e. 1800 from the first line.

Both lines are extended until they intersect either the next adjacent stringer or the next adjacent station; either can be selected. The two lines then connect the selected coordinate point with the intersection points with adjacent stringers or stations.

If a third straight line is now constructed connecting the two extremes in relation to their distance from the winding axis, ie. the intersection points of the winding plane with said stringers, or the stations next to the selected coordinate point, the selected coordinate point being bridged if it is closer to the winding axis than the third line. The third line is constructed on a sketch in the winding plane. The coordinate point, if bridged, must be raised to the level of the second line to avoid bridging. The procedure is repeated for each coordinate point except for boundary points at the axial ends of the bearing surface. The procedure can be performed by hand in a known manner or automatically by means of computer technology. Said stringers and / or stations do not have to be flat or parallel to the respective perpendicular to the winding axis. The method is adapted to each coordinate system which gives the bearing surface shape or geometric description of the bearing surface and the winding web.

Figure 1 is a perspective view of a bearing surface with winding shaft, and sections. Figure 2 is a diagrammatic view of a part of the bearing surface according to Figure 1 showing the intersection between stringers and stations.

Figure 3 is a diagrammatic view taken along line 3-3 of Figure 2.

Figure 4 is a schematic drawing on a computer for the method according to the invention.

Figure 5 is a flow chart showing the steps in carrying out the process by means of the computer according to Figure 4.

When a bearing surface is designed for a special purpose, e.g. as a rotor blade for driving a wind turbine, there are certain shape limiting factors such as profile length, aerodynamic function, weight, load distribution, etc. Although the blade production is also taken into account, many shape parameters can not be changed even if the special shape causes problems in blade production .

For large wind turbine blades, conventional manufacturing technology is expensive and difficult and a fiber-wound blade gives optimal results. Linds 7910361-0 has, however, presented unexpected difficulties due to the above-mentioned bridging problem. The present invention eliminates these problems without completely reshaping the blade or modifying the core on which the fibers are wound based on test results without at the same time having a significant impact on the acrodynamic function of the blade. The specified procedure can be easily adapted to manual technology, ie. can be performed by hand in a known manner, but by the same iterative nature most suitable for a rotor. The procedure is described by the steps to manually achieve the required result, but a computer does the same work faster and more efficiently.

With turning to Figure 1, a part of a normal bearing surface is shown here, e.g. a rotor blade 10, in perspective. Since a particular curvature or profile is not shown, it is assumed that the cross-sectional shape of the blade varies in curvature and size in the axis direction, the hub end normally being thicker than the outer tip. The inventive method can be used for any conventional aerodynamic bearing surface, and not only the bearing surface but for each profiled surface.

Once the blade is formed, for winding fibers into the desired anodynamic shape, it is necessary to construct a core for winding the fibers thereon. It has been found that if the core is constructed according to the shape, the rotor blade production becomes problematic due to the bridging problem. It is of course possible to manually inspect the core after its manufacture, with e.g. a straight edge along the paths over which fibers are to be wound, and correct concave parts, but this solution is very time consuming and each correction requires a new examination to determine if the correction has given rise to another concave part when the fiber is wound in a return path. This procedure is clearly unacceptable.

The method according to the invention uses known geometric techniques to determine from shape data and before the core is manufactured whether any concave parts are present in the fiber winding paths and the shape of the core can be changed before the manufacture thereof to avoid bridging.

The leaf shape is often defined in cylindrical coordinates even if the coordinate system is irrelevant since through simple mathematics one coordinate system can be converted to another. Assuming that a cylindrical coordinate system is used, a plurality of strings are constructed geometrically, manually or by computer, normally but not necessarily in a plane also including the winding axis of the blade. Three such representative stringers are shown in Figures 1 and 7910361-0 6 are designated A, B and C and lie in plane through the winding axis; however, the actual geometric shape and number of said strings are variable.

Said stringers extend completely around the circumference of the bearing surface, and can be arranged at fixed intervals, e.g. at 50 intervals or vary e.g. 100 at relatively straight cross-sections of the blade and 1/20 at the front and rear edges where greater curvature is present.

Although each stringer normally but not necessarily lies flush with the winding axis of the blade, these at the points of disturbance with the bearing surface are not parallel to each other, see figure 2, but can actually be curved depending on the curvature of the bearing surface. A stringer along the leading edge of the bearing surface will e.g. to be curved in two dimensions as the bearing surface becomes narrower at the tip and curved in the longitudinal direction.

Also shown in Figure 1 are a plurality of sections or stations, designated 1, 2 ... 9. Each section lies in a plane which is normally but not necessarily perpendicular to the winding axis. The winding axis is denoted by 8. The number of stations varies in relation to the length and curvature of the blade; a suitable distance is approx. 5% of the blade length.

Coordinate points 12 (Figure 1) are obtained at the intersection of each stringer and each station.

The bearing surface according to Figure 1 may comprise a winding ring, also called an adapter or rotation. For example. the real rotor can stop at station 3 with stations 2 and 1 as part of a winding ring. When utilizing the invention, it is normally necessary to include the pivot ring to guarantee a bridge-free shape on both the support surface and the surface between the winding ring and the support surface.

The following procedure is repeated for each coordinate point on the bearing surface matrix except at the boundary points.

With reference to Figure 2, a coordinate point 14 has been selected at the intersection between stringer B and station 3. Furthermore, it should be noted that Figure 2 is a two-dimensional plan view of a specific part of the bearing surface, and that the bearing surface actually varies in cross-sectional shape, ie. each point in Figure 2 varies in height or depth, namely into or out of the plane of the paper, as a function of the bearing surface shape.

Through the selected coordinate point, two planes 16 and 18, so-called winding plane, with angles corresponding to the fiber winding angles. Using plane 16 as an example, draw two straight lines, designated ¿and 17 in Figure 3, which coincide with plane 16, the first line 15 beginning at the coordinate point 14 and until it intersects either station 4 or stringer A designated as points B4 and A1 respectively in Figure 2, and wherein the second line 17 begins at the coordinate point 14 and extends in the opposite direction as the line until it intersects either station 2 or stringer C, shown in Figure 2 as points B2 and C1, respectively. Adjacent station or stringer to the selected coordinate point can be selected. Since both lines 15, 17 lie in the winding plane 16, they are normally not in line with each other, as the bearing surface is a three-dimensional surface.

Furthermore, it should be noted that geometric models other than planes can be used to define the winding path, and that the invention includes all such models.

Regarding the winding plane 18, two further straight lines are drawn in opposite directions from the coordinate point 14 in the winding plane to the intersection point with adjacent stringers or stations, these points in Figure 2 being denoted by A2 or C2 for one line and D2 or D4 for the other line. Again, since all points are in the same plane, it is irrelevant which points were used. In the example, the intersection with the said stringers was used as intersection points.

The distance of the points of intersection from the winding axis must now be determined. The distance of the coordinate points is known. Assuming that the lines between adjacent coordinate points are straight, and that it is unlikely that the winding plane will intersect adjacent stringers or stations at the coordinate points, a third straight line 20 (see Figure 3) is drawn between points A1 and C1, the position of the third line relative to the coordinate point 14 determines whether the coordinate point is bridged. Thus, if the coordinate point is located at 14a as shown, the coordinate point is closer to the winding axis than the line between points A1 and C1 and is bridged. If the coordinate point is located at 14b, the coordinate point is further away from the winding axis than the line between points A1 and C1 and will not be bridged.

Each coordinate point along or above line 20 is not bridged, while each coordinate point below line 20 is bridged.

If a coordinate point is bridged, it must be raised to the level of line 20 to avoid bridging.

Points B2 or B4 can be used in Figure 3 rather than A1 or C1, since all the points are on the same line and in the winding plane.

The above procedure is repeated with points A2 or D2, and points C2 or D4 in the winding plane 18.

The above procedure is repeated for each non-boundary point on the bearing surface matrix. This completes an iteration of the procedure. 7910561-0 If the winding path is other than one plane, the line 20 must not intersect a line from the winding axis1, perpendicular thereto, through the selected coordinate point. In the method according to the invention this is irrelevant, since relevant data is the difference, if any, between the distance of the line 20 from the winding axis and the distance of the coordinate point from the winding axis.

As an alternative to examining each selected coordinate point for possible bridging along both winding planes 16, 18 and then continuing to examine the next coordinate point in the same way, for some embodiments it may be desirable to first examine each coordinate bridge in succession along a winding path, e.g. the clockwise helical winding path, and then re-examine the same coordinate points for bridging in succession along the second winding path, e.g. the left-handed spiral winding path. An advantage of examining each coordinate point in both winding paths before continuing with the next coordinate point is that under certain conditions a bridged coordinate point does not need to be changed. If e.g. a relatively small bridging occurs in the winding path of the first or lowest fiber, such bridging can be ignored in some cases, if the winding path of the subsequent fiber, in the opposite direction, does not bridge the coordinate point as it is physically forced downwards by the subsequent fiber to contact with the core, whereby the bridging problem at the coordinate point is eliminated.

If any coordinate point is raised to eliminate bridging, it is necessary to repeat the procedure to determine whether raising the coordinate point has resulted in bridging another coordinate point.

The number of stringers or stations, and thus the number of coordinate points, is a shape choice and depends on the leaf curvature, i.e. for a blade with large pitch angle changes and / or curvature, it may be desirable to use more coordinate points than with a more straight bearing surface shape.

The method has been described for cylindrical coordinates, but also applies to other coordinate systems by simple geometric and / or mathematical transformation of bearing surface shape data. In practice, südngers and stations do not have to be flat or coincident with or perpendicular to the winding axis. After elimination of bridged points, the final coordinates 7910361-0 were used to design the core for winding the bearing surface, and can be analyzed for aerodynamic and structural function.

Fig. 4 shows a typical computer for carrying out the method, with which the method is simplified and improved.

Fig. 5 shows with a flow chart the instructions programmed in the computer for the method according to the invention. It is obvious that the procedure can be completed according to the steps in the flow chart by means of any suitable numerical machine or pre-programmed analog machine or microprocessor. The actual program steps may vary depending on the computer and available computer language, and constitute only simple mathematical calculations or logical steps, the completion of which is obvious to those skilled in the art. In practice, the program used is program Fl43 in the Hamilton Standard Division of the United Technologies Corporation on an IBM 370 / l68 computer.

The steps can also be performed by means of a pocket calculator, e.g. an HP65, which can preferably count on trymxymmetric and logarithmic functions. The computer itself does not form part of the invention and is shown for illustrative purposes only as an example of an apparatus for carrying out the invention in the best way.

Referring to Fig. 4, the basic elements of a numerical machine for carrying out the invention are shown here and which comprise an input means 50, e.g. a tape or punch card reader which feeds the bearing surface shape data to a memory 52, and a calculation and control unit 54. After performing the program instructions, the data is fed to an output means 56, e.g. a printer. The memory 52 and the control unit 54 communicate with each other via a line 58. The unit 54 normally comprises a control logic circuit for the particular program, an instruction register, which receives instructions from the memory including maneuvers and addresses, an arithmetic unit in two-way connection with the memory in which maneuvers are performed, as well as an address register, which feeds data to the memory. The input and output units may include peripheral equipment for translation to and from the computer language. other components are known and are therefore not described in detail.

Fig. 5 shows in flow plan form the program steps performed in the computer according to Fig. 4. When automating the method according to the invention, it is desirable to set a limit on the numerical value for changes in the coordinate point in order to avoid bridging, i.e. if a coordinate point is bridged only slightly, e.g. 0.05 cm, the bridging can be ignored, or all coordinate points must be carefully freed from bridging. In practice, it is 7910361-0 almost impossible to construct a core with an accuracy of 0.05 cm, so less bridging can actually be ignored. Block 100 in Fig. 5 thus contains an instruction, in which a limiting numerical value for the change in the coordinate point for avoiding bridging is determined and stored in the memory of the computer. It may be that the limit value is zero, i.e. no bridging is allowed. Another purpose, not shown in Fig. 5, is to set a maximum value for the iteration of the process, count each iteration and stop the program when the maximum value has been reached. Some points can still be bridged, but most or at least most of them will have been corrected. Likewise, it may be desirable to ignore bridging through the first fiber layer if the next layer is not bridged.

After setting the numeric value for changes in the coordinate point, the program proceeds to block 102, where a storage register in the data memory is reset at the beginning of each iteration of the program for the entire sheet. As the program progresses, the numeric value of the maximum coordinate point change required to avoid bridging during an iteration is stored in the register.

Finally, the value in the storage register will be compared with the set limit value according to the instruction in block 100 to determine if the program is terminated, i.e. no bridging has taken place or the largest bridged coordinate point is less than the limit value or another iteration is necessary due to that the change in a coordinate point to avoid bridging is greater than the limit value.

The program then selects the first coordinate point, block 104, and determines in block 106 from the shape data of the sheet stored in the data memory, the numerical value of the coordinate point, i.e. the distance between the coordinate point and the winding axis. The next step, block 108, is to calculate the numerical value of the coordinate point to avoid bridging, i.e. calculate points A1 or C1 and B2 or B4 and also points A2 or C2 and D2 or D4, as in Fig. 2, and interpolate between other coordinate points if necessary and then, as in Fig. 3, calculate the distance of the coordinate point from the winding shaft to avoid bridging. The shape data for the coordinate point in block 106 is then compared by the instruction in block 110 with the value for the coordinate point to avoid bridging performed in block l08 and if the shape value is less than the calculated value, bridging takes place and the program is passed to block 112. 112 instructs the program to change ll 7910361-0 the shape value of the coordinate point to the calculated value to avoid bridging. The next instruction in block 114 compares the numerical value of the coordinate point change to avoid bridging with the value stored in the memory by the instruction in block 102. Since block 102 resets a storage register during each iteration and the first bridged coordinate point causes the numerical value of the coordinate point change to avoidance of bridging is greater than zero, this value will always be stored. For subsequent bridging coordinate points, the numerical value of the coordinate point change becomes or does not become greater than the value in the storage register. Thus, if the change in a subsequent coordinate point is greater than the value in the storage register, the program is continued in block 116, which instructs the program to store the value of the new coordinate point change. Finally, for each iteration, the storage register will contain a value equal to the largest numeric change at any coordinate point.

If the change in the coordinate point is less than the value in the storage register, the instruction in block 116 will be bypassed and the program proceeds to the instruction in block 118. Likewise, if the coordinate point is not bridged, the program proceeds from block 110 to block 118.

The instruction in block 118 requires an iteration of the instructions from block 104, so the program returns to this and the next coordinate point along the same station is selected. When all coordinate points along a station have been examined for bridging, the program proceeds to block 120, where it is instructed to repeat the whole process, for each station except the first and the last. After each coordinate point on the sheet, except those at the first and last stations, has been examined for bridging, the program proceeds to the instruction in block 112, where the value of the largest coordinate point change during the entire iteration, stored in the register, is compared to the limit value in block 110. If the largest change at any coordinate point is less than the limit value, the program ends, but if it is greater than the limit value, the program proceeds to the instruction in block 124, which requires a return to block 102 and another iteration of the procedure for the whole leaf. As previously noted, a limit can be set for the number of iterations.

Since the fiber winding web has been described as being flat, this is not the only possible geometric model for the winding web.

Claims (4)

7910361-0 1? banana. It is possible to define the winding path with other geometric constructions. The invention primarily relates to a method for determining and correcting the presence of bridges on the surface of a wound profile and is not limited to the coordinate system used here or the geometric model used here for defining the fiber winding path. Since the invention has been described in connection with a rotor blade, the same can also be used for any profile shape, where bridging should be avoided when the profile shape is wrapped with some material. Patent claim uuuuuunuuu 1. A method of making a fiber-wound wind turbine blade, characterized in that a surface representing a winding core is formed; a plurality of stringers being formed along the surface, each stringer occupying substantially the same direction as the axis about which the surface is wound; a plurality of stations being formed along the surface, the respective station being substantially perpendicular to said stringers and the intersection between the respective stringer and the station forming a plurality of coordinate points on the surface and the intersections thereby a grid system of coordinate points; that for each coordinate point its height is determined from the winding axis; that a first point on the surface is selected on the stringer or station next to the coordinate point on one side thereof and that a second point on the surface is selected on the stringer or station next to the coordinate point on its opposite side; that the presence of a concave portion on the surface is determined by comparing the height of the coordinate point from the winding axis with the height from the winding axis of a straight line connecting the two selected points, said surface being concave between the selected points_then the height of the coordinate point connecting the selected points height from the winding axis; that certain concave portions are corrected by adjusting the height of the coordinate point from the winding axis so that it is substantially equal to or greater than the height of said line from the winding axis; that a core with a surface corresponding to the corrected surface is formed; and that fibrous material is wound around said core surface to form said fiber wound sheets. 2. A method according to claim 1, characterized in that before the core is constructed, it is determined whether the height of any of the coordinate points has increased, and that if so, the first and second points for each such coordinate point are re-selected, determined for each coordinate point the presence of a concave portion on the surface and the height of each coordinate point for which a concave portion is determined is changed. Method according to claim 1 or 2, wherein several fiber winding paths occur, characterized in that for each coordinate point the presence of a concave part of the surface in the respective fiber winding path is determined and that the height of each coordinate point changes if it occurs in any fiber winding path. a concave surface. A method according to any one of claims 1 - 3, characterized in that the design of said plurality of stringers comprises forming a plurality of planes, which respectively comprise the winding axis, the cutting of the plane with said surface forming said stringers.