Wind turbine designs. What is the differences between the multice-hasting screws and the fibrous habits the speed of rotation of the wind turf blades
Very often, people are mistaken in the fact that the multilave screws for the weak wind, and the three-two bladed for a strong one. And many believe that it is more effective for weak winds that are more effective precisely the multicast screw, because many blades, from this traction above, more winds cover the blades, torque above, and therefore power, but it is not. Of the larger number of blades above the starting point, so if the generator has a strong magnetic sticking, then you have to do something to increase the starting point, and usually adding blades.
Let's imagine one blade first and physical factors acting on it. The blade has a twist, angles relative to the wind stream, and the wind leaving on it, causes the blade under pressure to move (squeezed out along the axis of rotation). But the blade moving in its plane overcomes the windshield (frontal) resistance of a dense air flow. This flow and slows down the blade without giving it to gain more revolutions, and the higher the turnover, the higher the aerodynamic resistance.
If the blades are more than one, two or three, or 12 pieces, the aerodynamic resistance of all the blades does not remain equal to one, it consists, the losses are folded into the general and turnover of the screw. Many energy is spent simply on rotation. Plus, the passing blades are very indignant to the stream spinning it, from this behind the running blades get even more windscreen resistance and again spent the power is spent at the wind and turns. It is at turns that spend a lot of power selected from the wind.
Just when the whole forest of the blades in a circle, the wind becomes harder to fall through the screw. The windwood delays the wind stream, the front of the screw is formed by the air hat, and new portions of the wind rolling into this "cap" are dissipated on the parties. You know how the wind envelopes obstacles, like this and the wind screw as a solid shield.
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But many will think that the greater the blades, the more energy can be taken away from the wind per unit of time, but it is also not so, it is not the number of blades, but the turnover and speed of the screw. For example, 6 blades Let's say at 60 bub / m to make one turn by passing the wind cube and taking a certain portion of energy, and 3 blades will make two turns over the same time, and take away the same energy. If you even raise the speed, then more energy is torn. It does not matter how many blades, one or ten, as one blade rotating ten times faster takes the same energy as ten slowly rotating blades.
The speedlessness of the windwall.
The screw speed is the ratio of the speed of the tip of the blade to the wind speed in meters per second. So with the same turns, the speed of the blade is different, then the corners of the installation of the blade along its length are different. The tip of the blade always moves twice as fast as the middle of the blade, so the tip the angle is equal to almost zero to reduce the windshield, so that the blade cut the air having minimal resistance.Just the faster the blade moves the stronger the angle of the wind attack on the blade changes. Let's imagine that you are sitting in the car and you in the side glass beats the snow, but when you begin to go, then the snow will already beat in the windshield, and when you get the speed, then the snow will already beat directly into the windshield, although when you stop Snow will beat the side again. So and the blade when he picks up the speed, the wind will lean on it under a different angle. Therefore, the tip of the blade makes only 2-5 degrees, as it will get involved in the optimal angle of the wind attack and will take a maximum of possible energy. In the middle of the blade, the speed is two times less, therefore, the angle is twice as much, 8-12Gradusov, and the root is even more, because there are fewer speeds there.
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For high-blasting screws, the corners are less and less. For example, for three-bladed screws, the usual highlightness is about Z5, then the screw has the maximum power rotating at a speed five times higher than wind speed. In this case, the tip of the blade has about 4 degrees, the middle of 12 degrees, and the root has about 24 degrees. If the blades are six, then the speed is twice as lower, it means that the angles are twice as much. Well, even the thinner of the blade and less its area, it is high-speed, and less her aerodynamic resistance, therefore three blades if they will have low high-speed, and six or twelve thin, narrow blades will have greater high-speed.
As a result, such a three-bladed and six-odd screw will have equal power in a small wind, because the three blades of the Z5 speed will be twice as turns than six blades with the speed of Z2.5 in the same time, which means that the amount of energy is taken away. But on a stronger wind, a six-odd screw will lose and strongly three-sandy, since three blades have less aerodynamic resistance and will be able to score large speeds, and therefore it will take place for a time of time with a large number of winds, because the faster the blade moves, the more power of the wind she will select .
The only plus that the more blades, the better the starting moment, and if the generator has magnetic sticking, then the multilave screw will start earlier, but the torque and power will be higher in the fibrous screws.
Yes, and torque, as the high-speed screw will be rotated, the corners of the blade will become optimal for the wind stream actually on the blade, and we know that the real angle changes depending on the speed of the blade itself and the torque will be higher, since less energy loss On the windshield resistance to the blades.
The same multilave screws are heavier, which means that the flywheel works. If the wheel has gained momentum, then the screw itself poices energy and it is harder to stop sharply, but when the wind will enlister this flywheel, it is necessary to promote more, so the multilave screws react worse to the change of wind strength, and the short-term gusts of the wind may not even notice. And light screws can give energy even with a short gust of wind. It is well noticeable by an ammeter when you watch the current power. Hexless works more softly, there are no large surges in the current. And the three-bladed manifests each gust and the arrow runs there here, and this is the energy that ultimately accumulates in the battery, and the difference in the return may be very significant, especially on the impact wind and if the mast is lowered where the wind flow is turbulent.
Another factor is the turnover, the multilavenic screw means slightly, it means that the generator is the same, which means the generator more, magnets are greater, the winding wires are greater, the weight of iron is greater, as a result, the price is much larger. And the generator is usually the most expensive part of the wind generator. And the turnups have the most important role, because the higher the screw turnover at the same wind speed the generator will give more power, and then if the revolutions are not enough, then or the generator is more and more powerful, or the multiplier is invented.
But everywhere there is our own, of course, the cheapest and efficient screws are single-blade, but they need to be done very accurately and balanced, all count, the aerodynamics of the blade should be perfect, otherwise the vibrations and the swolossing of the screw, and then the broken windmill are guaranteed. In principle, on this, even nobody releases the single-blade windmills. Three-bladed screws were more optimal, they are not such high-speed, therefore some screw imbalance is not terrible, but the turns are high, which means the generator is cheaper.
But all the same, high-speed blades require proper aerodynamics, otherwise all efficiency may fall at times. Therefore, at home, it is often easier, although it's more expensive to make a rough, big, ineffective, but simple in the manufacture of the windmill, without any calculations and the campaign to improve it, redo, and redo it, and finally, or gain knowledge and bring everything to mind, or throw knowledge And to say that all this garbage, bought from the Chinese and do not suffer, still better than the factory you can't do, only the money is in vain on the wind wave.
Energy production growth due to use not renewable natural resources Is limited to the threshold, followed by the full production of raw materials. Alternative energy, including energy wind generation, will provide a reduction in the burden on the habitat.
The movement of any mass, including air, generates energy. Wind turbine converts the kinetic energy of the air flow into mechanical. This device is the basis of wind power, an alternative direction in the use of natural resources.
Efficiency
Estimate the energy efficiency of the unit of a certain type and design, compare it with the indicators of such engines is quite simple. It is necessary to determine the coefficient of use of wind energy (Keev). It is calculated as the ratio of the power obtained on the shaft of the wind turbine, to the power of the wind stream acting on the surface of the windyllus.
The wind energy utilization factor for various settings is from 5 to 40%. The assessment will be incomplete without taking into account the costs of designing and building the object, the number and cost of generated electricity. In an alternative energy, the payback period of the cost of a wind turbine is an important factor, but also obligatory accounting for the resulting environmental effect.
Classification
Wind turbbles on the principles of using developed energy are divided into two classes:
linear;
Cyclic.
Linear type
A linear or mobile wind turbine converts the energy of the air flow into the mechanical energy energy. It can be a sail, wing. From a engineering point of view, this is not a wind turbine, but a propulsion.
Cyclic type
In cyclic engines, the housing itself is fixed. The air flow rotates, performing cyclic movements, its work parts. The mechanical rotation energy is most suitable for generating electricity, a universal energy type. Cyclic wind turbines include windwalls. Windscape from the ancient windmills ending with modern wind power plants, differ in construction solutions, to the completeness of the use of the strength of the air flow. Devices are divided into high-speed and low-speed, as well as horizontal or vertical direction of the axis of rotation of the rotor.
Horizontal
Wind turbbles with a horizontal axis of rotation are called impert. On the shaft of the rotor, several blades (wings) and flywheel are fixed. The tree itself is located horizontally. The main elements of the device: wind vehicles, head, tail and tower. The windwall is mounted in the head rotating around the vertical axis, in which the motor shaft is mounted, transfer mechanisms are placed. The tail performs the role of a fluger, turning the head with a wind-boiler against the direction of the wind stream.
At high speeds of moving air flows (15 m / s and above), the use of high-speed horizontal wind turbines is rational. Two, three bladed units from leading manufacturers provide 30% keeve. Self-made wind turbine has a coefficient of use of the air flow to 20%. The efficiency of the device depends on the careful calculation and the quality of the manufacture of blades.
The wing wind turbines and wind installations provide a high rotation speed of the shaft, which allows the power directly to the generator shaft. A significant disadvantage is that with a weak wind, such wind turbines will not work at all. There are launch problems when moving from ulution to wind strengthening.
Slowing horizontal engines have a greater number of blades. A significant area of \u200b\u200binteraction with air flow makes them more efficient with weak winds. But the installations have significant sailboat, which requires the adoption of measures to protect them from the bust of wind. The best indicator of the cyser 15%. On an industrial scale, such installations are not used.
Vertical carousel type
In such devices on the vertical axis of the wheel (rotor), blades that take the flow of air are installed. The housing and the damper system ensures the ingress of the wind stream on one half of the wind vehicles, the resulting response moment of the application forces ensures rotation of the rotor.
Compared to the wing aggregates, the carousel wind turbine produces a greater point of rotation. With an increase in the air flow rate, it is faster on the operating mode (according to the strength of the thrust), stabilizes the rotation speeds. But such aggregates are slow. To transform the rotation of the shaft into electrical energy, a special generator is required (multipole), capable of working on small revolutions. The generators of this type are not very common. The use of the gearbox system is limited to low efficiency.
A carousel wind turbine is easier to exploit. The design itself provides automatic regulation of the number of rotor revolutions, allows you to track the wind direction.
Vertical: orthogonal
For large energy, orthogonal wind turbines and wind installations are most promising. The range of use of such aggregates, by wind speed, from 5 to 16 m / s. The power generated by them is adjusted to 50 thousand kW. The profile of the orthogonal installation blades is similar to the profile of the wings of the aircraft. In order for the wing to start working, the air flow is on it, as during the run of the aircraft during takeoff. The wind turbine also needs to be previously promoted, spending energy. After completing this condition, the installation goes into the generator mode.
conclusions
Wind energy is one of the most promising renewable energy sources. The experience of industrial use of wind turbines and windings shows that efficiency depends on the placement of wind generators in places, with favorable air flows. The use of modern materials in the structures of the aggregates, the use of new generation and accumulation schemes will ensure further increase in the reliability and energy efficiency of wind turbines.
Flow power, or as it is also called second energy, proportional to the wind speed cube. What does it mean - if the wind speed increases, admissible, twice, then the energy of the air flow will increase by 2 3 times, namely 2 3 \u003d 2x2x2 \u003d 8 times.
The power developed by the wind turbine will vary in proportion to the square of the diameter of the wind vehicle. What means with an increase in two times the diameter of the windwall - we get an increase in power at the same wind speed four times.
However, not all the energy flowing through the wind vehicles can be turned into a useful work. Some of the energy will be lost when overcoming the resistance of the wind flow of the wind flow, as well as on other losses. Also, quite most of the air energy will be contained in the stream that has already passed through the windywell. In the theory of imperted wind turbines, it is proved:
- The speed of the wind stream behind the wind housing is not zero;
- The best mode of operation of the wind turbine is the one in which the flow rate behind the windley will be 2/3 from the initial flow rate, which will be blocked on the windweight.
Energy utilization factor
This is a number that shows which part of the air flow power will be useful to be used by winder. This coefficient is usually the Greek letter χ (KSI). Its value depends on a number of factors, such as the type of velotor, the quality of the manufacture and shape of its blades and other factors. For high-speed wind turbines, which have a streamlined aerodynamic shape of the wings, the coefficient χ is from about 0.42 to 0.46. This means that the machines of this type can turn into a useful mechanical work of about 42% -46% of the wind flow passing through the installation. For the lowest machines, this coefficient is about 0.27 - 0.33. The theoretical maximum value χ for ideal impeller wind turbines is approximately 0.593. Foreign installations were quite widespread, and they massively began to be produced by industry. They are divided into two groups:
- Running - the number of blades to 4;
Sour - from 4 to 24 blades;
Right and low-speed wind turbines
Specificity is one of the advantages, since it makes the simpler wind energy transmission with such high-speed devices as an electric generator. Moreover, they are lighter and has a higher wind speed utilization ratio than low-speed, as mentioned above.
However, in addition to the merits, they have a serious disadvantage, such as several times less than a torque at a fixed winder and with the same diameters of the wheels and wind speed than the low-speed installations. Below are two aerodynamic characteristics:
Where the dotted is shown 18-blade wind-free, and solid - 3-way paddle. According to the horizontal axis, the number of wind velocity modules is postponed or its high-speed. This value is determined by the ratio of the velocity of the end of the blade to the wind speed V.
From the characteristic of the wind turbine, it can be concluded that each wind speed can have only the only number of revolutions at which it is possible to obtain the maximum χ. In addition, in the presence of the same wind speed, the low-speed device will have a moment more than the high-speed, and, accordingly, it will start working at a wind speed smaller than the speed. This is a rather significant factor, as it increases the number of hours of wind turbine.
Foreign wind turbines
The principle of their work is based on the aerodynamic forces, which will arise on the voctern blades when the air flow is running. In order to increase the power of the wings give streamlined, aerodynamic profiles, and the clarification angles are made by variables along the blade (the closer to the shaft - the greater the corners, and at the end smaller). The scheme is shown below:
There are three main parts of this mechanism - the blade, max, with which the wheel is attached to the hub. The angle of the clarification φ is the angle between the plane of rotation of the wheel with the blade. The angle of attack α is the angle of the wind raid on the elements of the blade.
With the inverted windweight, the direction of the flux by the blade and the direction of the wind coincided (by arrow V). But since the wheel has some speed of rotation, then, accordingly, each of the elements of the blade will have a certain rate of ωXR, which will increase with a distance from the axis of the wheel. Therefore, the flow that blows the blade at some speed will consist of a velocity ΩXR and V. This speed has the name of the relative flow rate and has the designation W.
Since only at certain angles of the attack, there is the best mode of operation of the imperative impeller, then the angles of the clarification φ have to make variables along the entire length of the blade. The power of the wind turbine, as well as any other, is determined by the product of the angular velocity ω at its moment M: p \u003d MXω. It can be concluded that with a decrease in the number of blades, the moment M will also decrease, but the number of revolutions Ω will increase. That is why, the power P \u003d MXω will remain almost constant and it will be weakly dependent on the number of windmill blades.
Other types of wind turbines
As you know except the impertured, there are also drum, carousel and rotary wind turbines. Carousel and rotary types of rotation axis vertical, and in drum - horizontal. Perhaps the main difference between the impertured wind turbines from the drum and the carousels will be that the impertants work all the blades at the same time, while the drum and carousers work only the part of the blades, the movement of which will coincide with the direction of wind movement.
To reduce resistance to the blades that go to the wind towards the wind, they are either curved, or cover the screen. The torque when using this type of engine occurs due to different pressure in the blades.
Since rotary, carousel and drum types of wind turbines have a rather low efficiency (χ for these types does not exceed 0.18), as well as rather bulky and low-spirited in practice they did not receive mass application.
Wind turbine
device transforming wind energy into energy rotational motion. The main working body of the wind turbine is the rotating unit - the wheel driven by the wind and rigidly associated with the shaft, the rotation of which drives the equipment that performs the useful operation. The shaft is installed horizontally or vertically. Wind turbbles are commonly used to generate energy consumed periodically: when pumping water in a container, grinding grain, in temporary, emergency and local power networks.
Historical reference. Although the surface winds do not always blow, change their direction and the strength of them is inconstant, the wind turbine is one of the most ancient machines to produce energy from natural sources. Due to the dubious reliability of the ancient written messages about the wind turbines, it is not quite clear when and where such machines appeared for the first time. But, judging by some records, they already existed to 7 century. AD It is known that in Persia they were used in the 10th century, and in Western Europe The first devices of this type appeared at the end of the 12th century. During the 16th century Finally formed the tent type of Dutch windmill. Special changes in their design were not observed until the beginning of the 20th century, when the shapes and coating of the wings of the mills were significantly improved as a result of studies. Since low-speed bulk machines, in the second half of the 20th century. High-speed wind turbines began to build, i.e. Such, which can perform a large number of revolutions per minute with a high coefficient of using wind energy.
Modern types of wind turbines. Currently, three main types of wind turbines are applied - drum, wing (screw type) and rotary (with an S-shaped repeller profile).
Drum and roof. Although the drum type winder has the smallest wind energy utilization rate compared to other modern repellers, it is most widely applied. On many farms with it, water is swing, if for any reason there are no network electricity. A typical shape of such a wheel with sheet metal blades is shown in Fig. 1. Drum and imperted type wind velocities are rotated on a horizontal shaft, so that they must be turned to the wind to get the best operational characteristics. For this, they are given the steering wheel of the direction - the blade located in the vertical plane than and is ensured by the reversal of the wind to the wind. The diameter of the wheel in the world in the world of the wing type wind turbine is 53 m, the maximum width of its blade is equal to 4.9 m. The windwall is directly connected to an electric generator with a capacity of 1000 kW, which develops at wind speed at least 48 km / h. Its blades are regulated in such a way that the speed of rotation of the wind-boas remains a constant and equal to 30 rpm in the range of wind velocities from 24 to 112 km / h. Due to the fact that in the area where such wind turbines are located, the winds blow quite often, wind power unit usually produces a wind turbine 50% of the maximum power and nourishes public circuit. Foreign wind turbines are widely used in remote rural areas to provide electricity farms, including charging radio communications batteries. They are also used in the onboard energy installations of aircraft and managed missiles.
S-shaped rotor. The S-shaped rotor mounted on the vertical shaft (Fig. 2) is good because the wind turbine with such a repeller does not have to withdraw on the wind. Although the torque on his shaft changes from the minimum to one third of the maximum value for half a turn, it does not depend on the direction of the wind. When a sleek circular cylinder rotates, being under the influence of wind, the strength is acting on the body of the cylinder, perpendicular to the wind direction. This phenomenon is called the effect of Magnus, in honor of the German physics, which he studied (1852). In 1920-1930, A.Flettner applied rotating cylinders (Flettner rotors) and S-shaped rotors instead of blade vocales, as well as the ship drivers, which made the transition from Europe to America and back.
The coefficient of use of wind energy. The power obtained from the wind is usually small - less than 4 kW develops an aggregate of the outdated type of Dutch windmill at a wind speed of 32 km / h. The power of the wind stream, which can be used, is formed from the kinetic energy of the mass of air, rushing perpendicular to the area of \u200b\u200bthe specified size perpendicularly. In the wind turbine, this area is determined by the surface of the refill. When taking into account height above sea level, air pressure on it and its temperature, the disposable power n (in kW) per unit area is determined by the equation n \u003d 0.0000446 v3 (m / s). The wind energy utilization factor is usually determined as the ratio of the power developed on the shaft of the wind turbine, to the disposable power of the wind flow, acting on the implanted surface of the wind vehicle. Maximum, this coefficient becomes with a certain relationship between the speed of the outer edge of the windbreaker W and wind velocity U; The value of this ratio W / U depends on the type of wind turbine. The coefficient of use of wind energy depends on the type of wind vehicles and ranges from 5-10% (Dutch mill with flat wings, W / U \u003d 2.5) to 35-40% (profiled impeller, 5 ј w / u ј 10).
LITERATURE
Wind power. M., 1982 Yaras L. et al. Wind energy. M., 1982.
The encyclopedia of the colley. - Open Society. 2000 .
Synonyms:Watch what is "wind turbine" in other dictionaries:
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Wings of the windywell are the most important part of the windmill. From the form of their blades, the power and revolutions of the wind generator depend on.
We will not dwell in this brochure on the calculation of new wings due to the complexity of this problem, and we use ready-made wings that have a certain shape and different high-speed wind energy ratio and high-speed. We only need to solve the question of how to determine the size of new wings on the desired power, based on the size of the known wings while maintaining their initial characteristics.
We will take a speed-blade vengeneck for low-power windmills with the following characteristic characteristic:
The coefficient of use of wind energy .................................... 0.35
Under the speed of the wind velocity, it is necessary to understand the relation of the district velocity of the end of the blade to the wind speed
Taking one and the same high-speed, equal to 7, for the windy of different diameters, we will receive different revolutions of the wind-boys at the same wind speed. The greatest turns will develop the windwall with the smallest diameter. In general, the revolutions of the wind and equal speed will relate to each other inversely proportional to their diameters, i.e.
This means the wind velocity with a diameter D 1 will be revolutions per minute in so many times more, which is how much the diameter of this winder D 1 is less than D diameter D 2 of another windwell. For example, if the windweight with a diameter of 1.5 m makes 714 rpm, then the windwall with a diameter of 3 m will do 357 rpm, i.e., two times less, although their speeds are the same.
For the convenience of counting the size of the blades of the windy of different diameters, but with the same speed in Table. 4 are given dimensions of two-blade winds with a diameter of 1 m. Top Table Dan drawing blade with lettering symbols Its sizes, and under the figure in the table give digital values \u200b\u200bof these sizes.
On the left in 4 columns are the dimensions of the blade to the left drawing; Right in 10 columns are given the size of five profiles of this blade. How to lift the profile size, is shown in the table figure on the right.
In order to comply with the accepted characteristic of the windercasses with a change in its diameter, all the dimensions of these blades are necessary to change in the same respect, in which we change the diameter of the windyoles. At the same time, we will have a geometric similarity, without which it was impossible to take advantage of this method of recalculation.
Since the wind velocity with the size shown in Table. 4, has 1 m in diameter, the ratio of the diameter of another wind-booster to one will be equal to D, i.e.
Consequently, to get the size of the windbreaker blades with another diameter, each size is necessary in the table. 4, multiply by the magnitude of this diameter. Alternatively should remain only the angles of the clarification of each cross section of the blade and the number of them. For example, for a winder, a diameter of 1.2 m, each size of the table is necessary. 4 Multiply 1.2, while we get:
To increase the table, click on it with the mouse
To get the finished shape of the blade, it is necessary in size,
dotted in table. 5, construct on a sheet of paper sheet for five blades and circuit profiles and circuit through the point of contours using pattern, as shown in FIG. 13. Profiles each section is drawn up to a natural value so that it is possible to cut patterns in the manufacture of the blade.
For a generator with a capacity of 1 kW, a venereso is needed with a diameter of 3.5 m. To obtain the sizes of the blade of this wind wheel, are required in Table. 4 DIMENSIONS OF AUTROPOLES DIMETER 1 M multiply by 3.5 and draw up a table, and then draw the profiles of the blades that will be needed in the manufacture.
The power and turnover of the two-bladed wind velocoles with the above characteristic are given in Table. 6.
This table should be used when selecting the diameter of the wind velocity of this power and determining the gear ratio of the gearbox, if the generator turnover is more revolutions of the wind-sized, developed by im at wind speed of 8 m / s.
For example, when used for the wind turbine unit of an automotive type GBF with a capacity of 60 W at 900 rpm, a venereso is suitable, having D \u003d\u003d 1.2 m, with a capacity of 0.169 liters. from. at 895 rpm (see the first two lines Table 6).
this case, the wind velocity can be fixed on the generator shaft. The wind electrical unit is the easiest and most convenient in the exploration.
If we had conceived to construct a wind-electrical unit with a capacity of 400 W, it would be necessary to take the diameter of the windwall 3 m, which at wind speed 8 m / s develops 1,060 liters. from. or 1,060 x 0.736 \u003d 0.78 kW. Taking to. P. D. Generator equal to 0.5, we get:
The wind velocity at wind speed 8 m / s is developing 357 rpm, and the generator at a capacity of 390 W requires 1,000 rpm. Consequently, in this case, a gearbox is required, increasing turns in the transmission from the wind-makes to the generator. The gearbox should increase the revolutions.
The value of 2.8 is called a gear ratio. With this relationship determines the number of gears gear gear. For example, if we take the gear based on the generator shaft, 16 ze.Byev, then the lead gear sitting on the tree of the wind vehicle must be
High-speaking winds suffer a very significant disadvantage in the fact that they are poorly drowning from the spot, therefore, they can start working only at high wind speeds.
Many novice wind vestments seem that, the greater the number of blades from the wind-makes, the greater power it will develop. This representation is erroneous. Two wind vessels are prefabricated and multiply with equally well-built blades and with the same diameters of the windy surface will develop the same power. This is explained by the fact that since they are equally well performed, then the coefficients of using wind energy will be equal, that is, they will transmit the same amount of energy to the working machine. The number of incoming wind energy is equal to the other winding energy, as they are equal to the oversized surfaces. As for the revolutions, they will be the greater the less blades, if they have the same width of the same vocales; In other words, the number of revolutions is the greater, the smaller the overall surface of the blades that form a worm surface.
How to determine the sizes of the wings of the homemade windmill (wind generator) to the specified power
Wings of the windywell are the most important part of the windmill. From the form of their blades, the power and revolutions of the wind generator depend on. We will not stop in this brochure on the calculation of new wings due to the complexity of this task, and we use ready-made wings that have a certain shape and characterized high
Calculation of wind-generator blades
On the optimal coal of the attack of the propeller windmill
In the techniques for the calculation of windmills, the recommendation is given to the angle of attack, in which the maximum aerodynamic quality of the blade is achieved. Those. It is proposed to build a tangent to the polar from the beginning of the coordinates, and the coordinates of the touch point are for initial to calculate the windmill. Most likely, it is refers to analogy with aviation, where with an increase in the relationship of the lifting force to the windshield, the duration of planning the aircraft is growing. Or it is proposed to use a blade with maximum lifting force. Windmill work occurs according to other laws.
Fig. 1 aerodynamic forces in the windmill
Figure 1 presents the diagram of the effects of aerodynamic forces on the blade. Wind speed when approaching the windmill slows down on a certain value A, which is 2/3 on the theory of Zhukovsky (Betz), and according to Sabinin theory 0.586. The circumferential movement of the blades gives an additional component of the speed, which can be found if you consider the blades stationary, and the air moving in the opposite direction. These two components add up according to the rule of the triangle and give the total flow of the flow of the stream to the plane of the wind vehicle. The speed angle ψ is determined by the ratio A / Z and does not depend on the wind speed:
Here and then all the calculations are conducted for the tip of the blade. For other sections, it is necessary to replace everywhere in the formulas z on the expression Zr / R, where Z is the speed-determining defined as the ratio of the wind speed to the speed of the blade; R - windmill radius; R is the radius of the selected section.
The speed angle of ψ is from an angle of attack α and the installation angle of the blades β. The angle of attack is located according to the characteristics of the blade, therefore, by setting the speed of the windmill, the task of calculating the blades is unambiguous.
The flowing flow causes two strengths: the length of the windscreen resistance X to meet the stream, and the lifting force y, perpendicular to it.
C x, c y - windshield coefficients and lifting force;
ρ - air density;
S - the area of \u200b\u200bthe blade element;
V. - the magnitude of the incidence vector, which in turn is equal to:
The last term in brackets is very small, and in high-speed windmills, the running rate is almost equal to the circumferential velocity of the blade.
District force is obtained as the difference in the projection of the lift and the projection of the windshield on the rotation plane.
The expression in the recent brackets can be called the aerodynamic coefficient of the district force or briefly circular coefficient
Windmill capacity is a piece of circumferential force for circular speed
This formula does not give the power of the windmill, but the power of the blade element located on the tip. The wind power is calculated by integrating by radius, but the purpose of the article in the other.)
Consider the polar blade in Fig.2.
Fig. 2 Finding the coefficient of the district force.
We will spend tangential OA to the polar. And we construct the high-speed direct OZ, which is given by the equation
Those. The high-speed direct forms with the axis of the CY speed angle ψ, discussed earlier.
OB is equal to the value of the lift at point A. Consequently:
The ABD angle is equal to the angle ψ, and AB hypotenuse is the windshield coefficient at point a. Therefore, BD catat is equal to:
Cut DE is the difference of two segments
It turned out the same expression as in the wind power formula. All other components in the power formula are set, so the power is determined by this segment or, in other words, the distance from the speed OZ line to the operating point. From the graph, it can be seen that the coefficient is maximized at the point of touching the speed line z 'to the polar, and not at the point of maximum aerodynamic quality. Therefore, by setting the speed and building a high-speed line, you can visually analyze the windmill work.
TsAGA profile R -LL-12
In fig. 3 shows the profile of the QAG R-LL -12, superimposed for comparison to the popular Clark profile in the windmills. Polar Poland profile P-LL -12 profile for elongation 5 is shown in Fig. four
Fig. 3 Tsagi profiles R- LL -12 and Clark - Y
Poles on the left is given in normal form with different scale across the axes of coordinates. On the right polar, drawn up in the same scale, the same construction was performed. The high-speed straight line at z \u003d 2 gives the maximum of the circumferential coefficient at the angle of attack in 16th. The point of maximum aerodynamic quality is achieved at an angle of attack in 2 degrees. At this point, the circumferential coefficient is about three times less than at the point of optimum. Of course, in the windmill, you can choose for the working angle of the attack 2 degrees. Windmill power depends on wind energy. Therefore, the circumferential coefficient decreased three times will need to be compensated by increasing three times chord the blade. (The idealized case is considered) in a square, 9 times, the volume of the blade will increase. With increasing area, friction losses increase. Cave drops. The elongation of the blade decreases, its inductive resistance increases. At the point of maximum aerodynamic quality, the windmill is better consistent with the degree of air inhibition in the wind turbine plane and the value of the district force. Coordination increases the cyser. Therefore, the calculation should be carried out with regard to all factors. It addresses only the value of the circumferential coefficient and its dependent blade width.
Fig.4 Pole of the profile of the TsAGA R- LL -12
With increasing speed, the point of optimum (minimizing the width of the blade) is approaching the point of maximum aerodynamic quality. At speeds 6 and the corner of the attack 8o winnings in the circumferential coefficient, and therefore in the width of the blades compared to 2 o, is 1.5 times. But from the analysis of the polar, it follows that with large values \u200b\u200bof the speed, it makes sense to choose the operating point below the polar. With insufficient load or absence of a load in emergency mode, the windmill is gaining speed, goes to the spread. The speed angle is reduced, and since the angle of installation in unregulated windmills remains constant, the angle of attack decreases. The working point shifts down, and the high-speed straight is approaching the polar. At some speed, the circumferential coefficient will become zero. The onset of this moment (the boundary value of z) during the separation depend on the initial position of the working point. The starting point is chosen below, the smaller the velocity rate will pick up the windmill. But this statement must be checked in practice.
When constructing a speed straight line Z \u003d 6, it is clearly seen that the polar in the range of an attack corners from 3 to 12 degrees is almost parallel to the speed direct. This gives an explanation for the application of a variety of theories and concepts for the calculation of windmills, practically do not affect the work of a designed high-speed windmill.
The cross sections of the blades located closer to the axis are moving slower than the external sections, so their high-speed straight lies below. In the inner sections, the point of optimum, i.e. The maximum value of the circumferential coefficient lies at large corners of the attack, therefore the installation angle and the blade twist, complicated, decreases.
As a result of the construction of high-speed direct, the family of optimal points for different speeds is obtained. Which of these points is the most optimal? What accumulation should be preferred? In the wind power formula, the ZV's highlightness is included in the third degree, and the circumferential coefficient in the first. Therefore, moving the circumferential coefficients to the corresponding cubes corresponding to them, we get a number of maxima from which you can choose the maximum. Maximum Maximurum lies about in the area of \u200b\u200bhalf aerodynamic quality, when speeding
Here K is the maximum CY / CX ratio. For the profile under consideration, the maximum occurs at the angle of attack 2 degrees and is equal to 24.
This blade has aerodynamic quality equal to 24, therefore, the maximum maximour will be in the z \u003d 10 area. This estimate is approximate, in order to understand the order of magnitude.
On the left graph in Figure 4, it is impossible to carry out the constructions of the district coefficient. There is a different scale on the axes, straight corners are distorted and the lengths are distorted. According to the right graph, you can determine that
with z \u003d 2, the product Z3COKO is equal to:
Those. At the speed of the Z \u003d 10, the width of the blades at the tip decreases compared to a rather high-speed propeller Z \u003d 6 2.3 times.
Once again I will pay attention to that the maximum maximum point gives a militant width of the blades, and not the maximum power. Power is determined by the wind. And the power is determined by losses, i.e. Windmill Kiev, which are not considered here.
PROGRAM - Design and calibration aerodynamic calculations of the wind generator - File Technical Report.doc
Technical report.doc.
Calculation of the aerodynamic characteristics of the wind turbine blade and determining its geometric parameters.
B - the number of blades
The report presents the results of calculations of the aerodynamic characteristics of the vocabulary and windmill in general. The geometric characteristics of the blade are presented.
^ 1. Source data for calculation.
The estimated wind speed V \u003d 12 m / s.
From the experience of creating wind generators of this class, the value of the relative speed is within 6 ... 8. The coefficient of use of wind energy (or CP power coefficient), in existing wind generators, is in the range of 0.43 ... 0.47. The velocity of the end of the blade is within up to 80 ... 100 m / s. This limitation is associated with aerodynamic noise and erosion wear of the blade. As an aerodynamic profile of the sections of the wind turbine, the profile of the NACA 44100 series, which is currently widely used. The use of laminar profiles allows you to get higher characteristics, but under the condition of high precision manufacturing, the lack of surface contamination blade, the absence of vibrations of the structure and turbulence of the wind stream. Not adherence to the above conditions reduces the characteristics of wind generators with laminar profiles of blades by 25 ... 30%.
Relative speed \u003d 7.
^ Table 1. Coordinates of the NACA 44100 profile.
Where: - a new relative thickness of the profile.
Relative speed (speed) \u003d 7.
Figure 2. Power of wind vehicles and turnover from wind speed (\u003d 7).
As can be seen from the results of calculations, the impected windywell satisfies the requirements of the source data and the practice of creating wind turbines of this class.
The construction of the geometry of the blade is made as follows. The direction of rotation of the rotor is counterclockwise, if you look at the wind direction. The angles of the sections are indicated from the rotation plane. A positive value - against the wind direction (Figure 3).
Resulting geometric data blades are presented in Table 2
In electronic form, data for the construction of the geometry of the blades are presented in files:
VG100.Scr - script file (or script file) for the program
VG100.DWG - built in AutoCAD model of the blade (Figure 4) according to the data from the VG100.SCR file.
VG100.catPart - Built in Catia Model Blades (Figure 5)
Figure 4. Frame model blade.
1. Patrick J. Moriarty, Aerodyn Theory Manual , National Renewable Energy Laboratory, December 2005 NREL / EL-500-36881.
2. John Wiley & Sons, Wind Energy Explained - Theory, Design and Application,
3. E. M. Fateev, wind turbines and wind installations, Oziz-Agriculture, m., 1948
4. H. Pigot, Calculation of windmills blades, 2000
5. G. Glauert, Fundamentals of the Theory of Wings and Screw, Great, 1931
6. E. Makarov, Engineering settlements in Mathcad 14, Peter, 2007
Technical Report - Program - Design and Taming Aerodynamic Calculations of the Wind Generator - Technical
Title: Program - Design and calibration aerodynamic calculations of the wind generator; File: Technical report.doc; Date: 03/16/2010 15:48; Size: 467KB.
