JP2009197700A - Vertical wind mill blade - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that a lift airfoil is often used in a vertical wind mill such as a gyro mill; this is because the power coefficient indicated by the output power to the wind power as the total efficiency is high compared with that of a drag type wind mill such as the paddle type and Saponius type one during the high-speed operation in the medium-to-high wind velocity range of equal to or more than several m/sec, while the lift during the stop and the low-speed operation is considerably small; the cut-in wind velocity is high and hardly raised, and it takes time to increase the rotational speed to meet the wind velocity even when the cut-in wind velocity is raised; the average power coefficient is considerably reduced, and the advantage of the lift airfoil is not realized. <P>SOLUTION: A lift airfoil is divided into a preceding portion and a succeeding portion, and a divided portion forms a passage through which air passes in a bending manner. The air coming from one side pushes the preceding portion from the inner side and discharged backwardly in the diagonal direction to generate a new propulsive force. The output power as the lift airfoil is substantially maintained, the cut-in wind velocity is reduced, and the rapid rise of the cut-in wind velocity is realized. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a blade of a vertical axis wind turbine used for wind power generation and the like, and more particularly to a wind turbine blade that can reduce the cut-in wind speed, which is the lowest wind speed that starts to rotate, and can generally maintain the output power as a lift blade while realizing a quick rise.

  In vertical axis wind turbines such as the gyromill type, lift wings similar to airplane wings are used. As is generally known, lift is proportional to the square of the relative velocity of fluid such as airfoil and air, as compared to drag type wind turbines such as paddle type and Saponius type in the middle and high wind speed range of several m / s or higher. Although the power coefficient expressed by the output power relative to the wind power, which is the overall efficiency, is high, the lift at low speed rotation is extremely small, so the cut-in wind speed is high and it is difficult to start up, even if it rises up to the rotation speed that matches the wind speed It took time to go up.

If the cause of the slow start is due to the moment of inertia of the windmill, it will be accumulated as energy, so there are few problems.However, if the rotational speed does not increase, the lift is small, Therefore, the average output is greatly reduced due to the delay in the conversion of this.Therefore, it is unavoidable to connect a motor or use a generator as a motor to rotate using an external power source such as a battery even when there is no wind or light wind. Some devices do not stop the operation, and others take measures to consume extra power, such as starting with a motor by detecting the wind speed, but this does not cover the poor rise from low-speed rotation.

In this way, the lift wing alone has a relatively low average wind speed, such as in an urban area, and it is difficult to put it to practical use in areas where it blows or stops and the wind speed changes greatly.
In order to improve this, there are proposals such as a compound wind turbine with a small drag type wind turbine, or a method of obtaining a drag force by opening a part of the lower surface of the wing (Patent Document 1). Although there is an improvement effect, it is basically an effect of adding a small drag type wind turbine blade, and not only a large drag cannot be obtained, but also the performance as a lift blade is impaired due to increased resistance.
Patent Publication 2004-60506

  A blade for a vertical axis wind turbine that can quickly stand up with a propulsive force according to the wind speed even when stopped or rotated at low speeds, and therefore does not require a starting operation by a motor, etc., and can generally maintain the output power as a lift blade even at high wind speeds. obtain.

  The present invention is a blade of a vertical axis windmill, and is a cross section representing an airfoil shape along a chord of a lift wing, and is approximately 1/6 to 1/2 of the chord length from the leading edge of the basic wing (1). The leading part (3) of the cavity cut between the trailing part (3) and the trailing part (4) starting from substantially the center of the blade thickness at the cutting position and extending to the trailing edge with a thickness within the blade thickness of the basic blade. ) And divided blades.

Even when stopped, the leading part (3) is pushed in the moving direction of the blades from the inside by the wind entering from one of the cutting positions of the divided blades, and the driving force is generated in the moving direction by the wind discharged to the other side. Achieving a quick start-up without the help of start-up, and this operation remains even if the peripheral speed ratio exceeds 1, so that the rotational speed is slightly lower than that of the basic lift wing during high-speed rotation, but the torque increases. Therefore, output power comparable to that of the basic type can be obtained.

A number of airfoils have been proposed for lift wings due to differences in their characteristics, and many of the data have been published, but the present invention can be applied to any lift wing including these. it can. Further, in the claims, the range of the length (Lf) of the leading portion (3) is recognized as a range in which the rise characteristic is significantly improved and the output power is not significantly reduced, from 1/6 to 1/2 of the chord length. However, as the best mode, it is generally set to a position near 1/3 from the leading edge, which is the position that gives the maximum blade thickness of the lift wing, to achieve both a significant improvement in rising characteristics and maintenance of output power. Estimated form.
Also, if the trailing part (4) is made thinner, the rise characteristics and output power at low wind speeds will become better, but the no-load peripheral speed ratio tends to decrease, so depending on the specifications and the convenience of production There is room to choose as appropriate.

The present invention can be applied to a vertical straight blade generally used as a gyromill wind turbine. In the experiment, the upper and lower ends of the wing were shortened in the experiment, and the wing length, which is the upper and lower length, was shortened. General both-end treatment can also be applied.
Further, since the blades are divided, a new support / fixing method is required. For example, the spacers (5, 6) shown in FIG. 14 are appropriately inserted in the vertical longitudinal direction and fixed with fastening parts (7) such as screws, There are also methods to connect stays to these, or to wrap them with bands as needed.

Embodiments will be described below with reference to the drawings. The data shown below was obtained with the following experimental wind turbine. In the data, for example, the no-load peripheral speed ratio is lower than a common value such as 2 or less. Because it has been shortened, the wind pressure resistance of the stay that supports the wing cannot be ignored, the wind escaping up and down the wing can not be ignored, and the influence of the vortex generated at the upper and lower wing tips is large, but there are some differences from the practical wind turbine, It is considered sufficient for comparing the performance of various types of wings.
Experimental windmill outermost radius (outermost circumference of wing): 110mm (unified for all experimental wings)
Number of wings: 3
Occupation angle of each wing: 45 degrees (unified for all experimental wings)
Blade length (vertical straight blade): 64mm (unified for all experimental blades)
Maximum blade thickness (unified in two types): W = 15mm, 20mm
Simple wind tunnel specifications (wide wind speed range depends on driving)
Three-stage wind speed switching: L = 1.5m / s, M = 2.7m / s, H = 3.5m / s

FIG. 1 is a blade cross-sectional view of one embodiment showing the basic operation of the divided blade of the present invention. The wing of the basic shape that is the basis is a straight symmetric wing that is partially connected as shown by the dotted line in the figure, but this is the position of the maximum blade thickness, for example, at the position (Lf) in the middle of the basic shape as shown by the thick solid line. The rear part cut in the step is divided into a leading part (3) of the cavity and a trailing part (4) starting from the cutting position, such that the cutting surface behind the cutting position is closed to the center of the blade thickness, In the middle of the wing along the chord, there is a passage that allows the wind to pass through the wing thickness while turning. As shown by the thick dotted line in the figure, the trailing portion may be thinned so that the wind can easily enter.

In FIG. 1, the upper pressure in the figure is high, and the flow of wind entering from the upper side and pushing the leading part from the inside and discharged downward and rearward is indicated by arrows. However, when the lower pressure is high, the flow is reversed. . The force that the leading part is pushed from the inside by the wind that entered seems to be the drag of the paddle type windmill, but for example, the wind that entered while turning from the top of the figure pushes the wing in the orthogonal direction, and is further discharged diagonally backward on the lower side Therefore, since the operation that becomes the propulsive force in the orthogonal direction also corresponds to the definition of lift, it will be simply referred to as the propulsive force without specifying either.
The split wing of the present invention is based on a lift wing. Naturally, the effective force acting on the wing is a combined force of the lift force generally described and the propulsion force. Explain with a focus on propulsion.

FIG. 8 shows the change at each rotational position of the split blade (1) operating in this way, FIG. 8 shows the state at the time of stop or low speed rotation, and FIG. 9 shows the ratio of the rotational speed at the outermost periphery of the blade to the wind speed. A state in a state where the peripheral speed ratio is 1 is shown.
In FIG. 8, the propulsive force described in FIG. 1 is generated on almost the entire circumference except for the vicinity of 270 degrees where there is no pressure difference between the upper surface and the lower surface of the blade from about 315 degrees to about 225 degrees counterclockwise with respect to the wind direction.
In FIG. 9 in the case of the peripheral speed ratio 1, the wind and the rotational movement of the blade are combined, and the wind direction with respect to the blade at each position is inclined forward of the blade as shown in the figure. However, even in this case, a part of the wind flows into the cutting position with a slight pressure difference as shown in FIG.

In general, a vortex is generated in a discontinuous region in the fluid such as the cutting position, and the resistance should be increased as the speed increases. However, as the rotational speed increases, the air near the cutting position receives centrifugal force and is pushed out of the rotating circle, so the flow from the inside to the outside increases in the middle and high wind speed range, which is due to resistance and division by vortex flow. It can be considered that the decrease in lift is compensated by the propulsive force generated by this flow.

FIG. 3 shows an embodiment in which the present invention is applied to a curved wing. Although it has already been described that there are various blade shapes, in this embodiment, as shown in FIG. 2, as a blade dedicated to a vertical axis wind turbine, a curved blade (1b) whose blade chord is curved along an arc centered on the rotation axis. ). The outermost peripheral radius, the maximum blade thickness W, and the occupation angle are defined as shown in FIG.

FIG. 3 shows that the present invention is applied to the curved wing (1b), and the length (Lf) of the leading portion (3b) is set to 1/3 (A), 1/4 (B) and 1/2 (C ), And the trailing part (4b) swells gently along the chord starting from the approximate center of the blade thickness at the cutting position of the leading part, and is the largest at the approximate center of the trailing part. This is an example in which the thickness becomes a thickness that gradually decreases thereafter and closes at the trailing edge, and any portion has a thickness equal to or less than the basic shape.

  Using the blade having the split blade (2b) having the maximum blade thickness W of 20 mm and the occupation angle of 45 degrees, the rising characteristics under no load were examined. Rise is measured by constraining rotation at each of the set wind speeds of wind speed L (1.5 m / s), M (2.7 m / s), and H (3.5 m / s), and the time after the restraint is released And compared with the rotation speed from time to peripheral speed ratio. In addition, when it did not stand up at any rotational position within the set wind speed, the subsequent values were measured after the forced start, and when it stood up depending on the blade position, the restraint was released at that position. In this example, only the basic shape has a position where the wind speed L does not stand up at any position and the wind speed M does not stand up.

  The measurement results for wind speeds L, M, and H are shown in FIG. From these figures, it can be seen that the rise of the basic form is significantly slower at any wind speed and the characteristics are curved, so that the generated torque depends on the rotational speed. Since it rises linearly, it can be seen that it has risen characteristics that do not depend much on the rotational speed but depend on the almost constant torque according to the wind speed and the moment of inertia of the windmill itself.

However, the peripheral speed ratio to be reached is the highest in the basic form, and all the divided blades are slightly lowered. In the diagram of the no-load peripheral speed ratio in the wide wind speed region of FIG. 14, (W20 basic form) and (W20 1 / As shown in the graph of the three-split blade), it tends to decrease by about 8% in the high wind speed region as well, but no extreme deterioration is observed.

Since only the micromotor is connected to the experimental wind turbine, the output power that can actually be extracted with the split blades was compared with the power coefficient ratio, which is the relative value of the power coefficient, as follows.
(AA) Generally, the power of a rotating machine can be expressed by the product of torque and angular velocity. When a motor is used as a brake, the fact that the braking torque is proportional to the motor current is used.
(BB) According to the theory that the maximum output can be obtained when the peripheral speed ratio at no load is 100% and the load is reduced to 70%, the wind speeds L, M, and H are respectively at no load. A current brake is applied from the external power source to the motor so that the peripheral speed ratio is reduced to 70%, and the product of the current value and the angular velocity is calculated as the brake power.
(CC) Using the product of the outermost peripheral diameter of the experimental wind turbine and the upper and lower blade length as the wind receiving area, calculate the wind power proportional to the cube of each wind speed, and remove the brake power obtained in (BB) above to simulate the pseudo power Find the coefficient.
(DD) In the basic form shown in FIG. 2, the maximum blade thickness W = 20 mm and the occupancy angle of 45 degrees is obtained by standardizing the pseudo power coefficient of various blades with the pseudo power coefficient being 1 when the wind speed H is in the wind speed H, The power coefficient ratio is a relative value.

As a result, it has been found that the split blade (2b) has an increased torque compared to the basic shape (1b), and as shown in the power coefficient graph of FIG. In the wind speeds M and H, although the 1/4 and 1/2 split blades are slightly lower than the basic shape, it can be seen that the 1/3 split blade can obtain almost the same power as the basic blade.

  The basic symmetrical wing used in this example is a straight line of the shape shown in FIG. 1 by removing the lower part of the NACA 2412 airfoil whose shape and other data are disclosed as airplane wings and turning the upper part back. A symmetric wing is converted into a polar coordinate having the X axis on the orthogonal coordinates as an occupied angle and the Y axis as a radius from the central axis, and is curved. This method is convenient as a method of bending not only the target wing but also other airplane wings with an arbitrary radius.

  FIG. 5 shows an embodiment based on an airplane wing. There are many cases where airplane wings are used as they are as vertical axis windmill wings. FIG. 4 shows an airplane wing of the basic form (1a) of the third embodiment. This figure is a cross-sectional view of a straight wing for an airplane with an elevation angle of about 3 degrees. As for the angle of attack, in the case of the linearly symmetric wing (1) shown in FIG. 1 or the curved symmetric wing (1b) shown in FIG. For airplane wings with a large thickness, it is better to give an angle of elevation with a no-load peripheral speed ratio and a power coefficient ratio. In the case of a symmetric wing, there is almost no difference even if an elevation angle is added, but if a depression angle that is a negative angle of attack is added, the performance tends to deteriorate.

FIG. 5 shows the leading part (3a) obtained by cutting the basic shape of FIG. 4 by the length Lf from the leading edge and gently starting from the approximate center of the blade thickness at the cutting position regardless of the position of the chord relative to the blade thickness. The bulge is the largest bulge at the almost half position of the trailing part, and the split wing (2a) is formed by the trailing part (4a) closed at the trailing edge.

  In FIG. 5, the dimensions of the leading portion on the orthogonal coordinates are taken in accordance with the convention of airplane wings. However, when this is used for a vertical axis wind turbine, the cutting position of the leading portion (3a) is cut at polar coordinates. Is slightly different depending on the cutting position on the upper and lower surfaces, but has little effect on the blade performance. What is important is that the trailing part starts from approximately the center of the cut surface connecting the cutting positions of the upper surface and the lower surface. This is in order to achieve both the fact that the wind passing through the cutting position has to bend and that as much wind as possible can pass through.

In other words, the size of the wind inlet and outlet is almost the same size, to prevent the wind that passes without bending, and to make the shortest passage, for example, if the starting point of the trailing part is shifted so as to enter the inside of the preceding part However, if the starting point is shifted backward to create a gap between the cut surface and the gap between the cut surface increases, the flow of wind increases, and the performance of the divided blades deteriorates. Although this tendency is not so sensitive, it is desirable to suppress the deviation within ± 10% of the blade thickness dimension at the cutting position in any blade shape.

As a specific example, the NACA4412 airfoil used for airplanes and windmills with data such as shapes is applied to a maximum blade thickness W = 15 mm and an occupation angle of 45 degrees, and the ratio of the chord length is slightly The present invention was carried out on the shrunken blade, and the split blade (2a) with the split position (Lf) being 1/3 of the chord length was attached to the experimental wind turbine and examined.

  FIG. 12 shows the rising characteristics at the wind speed L in (W15 basic type) and (W15 1/3 divided blade). In this test, the basic shape does not rise at any rotational position, so it was not possible to compare the time because it started to rotate considerably at time 0, but in the case of a split blade as shown in the figure It can be seen that it has risen linearly and has been greatly improved. Further, the peripheral speed ratio to be reached is slightly lower than that of the basic type in substantially the same manner as (W20 1/3 split blade) in FIG. 10, and in the unloaded peripheral speed ratio in the wide wind speed region of FIG. 14 (W15 1/3). The split blade) gradually decreases to a wind speed of about 3 m / s, and is almost the same as (W20 1/3 split blade) above this, but is about 10% lower than (W15 basic type).

  The power coefficient ratio shown in (W15 basic type) and (W15 1/3 split blade) in FIG. 13 is higher than the basic type at the wind speed L as in the case of the W20 blade, and slightly higher power is obtained at the wind speeds M and H. I understand that The power coefficient ratio is relatively low because the blade is thinner than the W20 blade, but this does not mean that the W15 blade is bad. If you use the W15 blade, increase the occupancy angle or increase the number of blades. It just indicates that there is room for such.

  6 and 7 show an embodiment in which the bulge of the trailing portion is eliminated. In the split wing of FIG. 1 of Example 1, it has been described that the bulge of the trailing part (4) can be thinned. However, when this is pushed forward, a curved flat plate as shown in (4d) of FIG. As shown, it can be a straight flat plate. Hereinafter, a split wing using a flat plate that does not bulge as a trailing portion is referred to as a split flat wing. The trailing part (4c) is a flat plate in which the starting point at the center of the blade thickness and the trailing edge are connected by a straight line at the cutting position (Lf) of the leading part (3b), and the power coefficient ratio is (4d). Since it seems to be slightly better than the divided flat blade, it was examined as a divided flat blade (2d) having a maximum blade thickness W = 20 mm and an occupation angle of 45 degrees.

The rising characteristics of this blade are shown in the graph of (W20 1/3 split flat blade) in FIG. As is apparent from the figure, the unloaded peripheral speed ratio reached by the split flat blades is slightly lower than that of the other divided blades. The unloaded peripheral speed ratio in the wide wind speed range shown in FIG. 13 is 5 m / s. It gradually declines to a certain extent, and has remained at about 18% below the basic form since then. However, it can be seen that the rising characteristics of the split flat blades are the fastest at any wind speed because the wind is likely to enter the cutting position. Further, in the power coefficient ratio of the W20 blade shown in FIG. 11, even though (1/3 split flat blade) is equivalent to (basic shape) and (1/3 leading blade) at wind speeds M and H, the wind speed L greatly exceeds these. You can see that

As another example, FIG. 7 shows an example of a split flat wing (2c) using an airplane wing used in the second embodiment as a basic form. Here, the maximum blade thickness w = 15 mm, the occupation angle = 45 degrees, and the case where the length L of the leading portion was greatly changed to 1/6, 1/3 and 2/3 of the chord length in FIG. . The difference from FIG. 6 is that, in addition to the blade thickness, the W15 wing is not a curved wing, and as shown in FIG. 7, the angle of the flat plate (4c) is small because the wing chord is a straight wing. That is. The split flat blade was measured with the angle of attack of about 3 degrees as described in the basic form of FIG.

The rise characteristics of this example overlapped in FIG. 12, but (W15 1/3 split flat blade) and (W15 1/6 split flat blade) are both the fastest, and (W15 2/3 split flat blade) is the basic shape. Although it was better, it did not stand up at any rotational position, and the result was insufficient. Also, the unloaded peripheral speed ratio reached is lower than that of the basic type. As shown in the unloaded peripheral speed ratio (W15 1/3 split flat blade) in the wide wind speed region in FIG. The result was almost the same as (W20 1/3 split flat blade), which was about 20% lower than the basic shape. In the power coefficient ratio of FIG. 13, (1/3 split flat blade) is the best at any wind speed, and at wind speed L, (1/6 split flat blade) greatly exceeds the basic shape (2/3 split flat blade). Then, the result was close to the basic form.
From these and the results of Example 2, it is better to set the split position between 1/6 and 1/2 of the chord length for the split blade, and from the above experiments, the vicinity of 1/3 is the best result. It was.

Blade cross-sectional view of the first embodiment showing the basic operation of the split blade A figure that defines the dimensions when using curved wings The figure which shows Example 2 applied to the curved wing | blade. A figure that defines the dimensions when using a straight wing The figure which shows Example 3 applied to the straight wing | blade The figure which shows Example 4 applied to the curved wing | blade. The figure which shows Example 4 applied to the straight wing | blade Operation diagram of split blade during stop or low speed rotation Operation diagram of split wing rotating at peripheral speed ratio 1 Graph of rising characteristics of W20 curved wing Graph of power coefficient ratio of W20 curved wing Graph of rising characteristics of W15 straight wing at wind speed L Graph of power coefficient ratio of straight wing of W15 Graph of no-load peripheral speed ratio in wide wind speed range The figure which shows an example of the support tool of a division | segmentation wing | blade

Explanation of symbols

1: Lifting blade as basic shape 1a: Straight blade 1b: Curved blade 2: Split blade 2a: Split blade with straight blade as basic shape 2b: Split blade with curved basic shape 2c: Reduced blade thickness at the trailing part Straight segmented blade 2d: Curved segmented blade with reduced trailing blade thickness 3: Leading portion 3a: Leading portion of straight blade 3b: Leading portion of curved blade 4: Trailing portion 4a: Trailing portion of straight blade 4b: The trailing part 4c of the curved wing: the linear trailing part 4d with a reduced thickness 4d: the curved trailing part 5 with a reduced thickness 5: a spacer that maintains the distance between the leading part and the trailing part 6: a spacer 7 that is housed in the trailing part : Fastening parts

Claims (1)

It is a blade of a vertical axis windmill, and is a cross section representing an airfoil shape along a chord of a lift wing, and is approximately 1/6 to 1/2 of the chord length from the leading edge of the basic wing (1). The cut back is the leading part (3) of the cavity and the trailing part (4) extending from the substantially center of the blade thickness at the cutting position to the trailing edge with a thickness within the blade thickness of the basic blade. A split wing (2) characterized by being split.

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