WO2014091264A1

WO2014091264A1 - Rotor for a wind machine with pneumatic power transmission

Info

Publication number: WO2014091264A1
Application number: PCT/HU2013/000124
Authority: WO
Inventors: Endre Mucsy
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-12-14
Filing date: 2013-12-12
Publication date: 2014-06-19
Anticipated expiration: 2015-06-14
Also published as: DE212013000252U1; HU1200735D0; HU4888U

Abstract

The invention relates to a rotor for a wind machine with pneumatic power transmission, which rotor (4) comprises a rotor hub (3) having a hollow inner space and rotor blades (10) connected thereto. Each of the rotor blades (10) comprise an inner blade section (7) having an air duct channel adjoining the hollow inner space of the rotor hub (13), a suction section (8) connected to the outer end of the inner blade section (7), which suction section (8) is provided with an air outlet opening being in flow communication with the air duct channel, and an end section (9, 12) connected to the outer end of the suction section (8) tapering to a cross-section smaller than that of the inner blade section (7). The invention further relates to a wind machine with pneumatic power transmission having the above rotor (4).

Description

ROTOR FOR A WIND MACHINE WITH PNEUMATIC POWER TRANSMISSION TECHNICAL FIELD

The invention relates to a rotor for a wind machine with pneumatic power transmission, the rotor comprising a rotor hub having a hollow inner space and rotor blades attached thereto. The invention further relates to a wind machine with pneumatic power transmission arranged with the rotor.

BACKGROUND ART

In conventional wind machines, the rotor is coupled by means of mechanical power transmission to the machine, most frequently an electric generator, utilizing the energy. Various different assemblies have so far been tested, nevertheless, most of the presently manufactured power-generating wind machines have horizontal axis, fast-running, three-blade rotors.

The power of wind machines is proportional to the surface of the circle swept by the blades, air density, and the third power of wind speed, whereof the only free variable is size. An increase of size will result in an increased power, but will decrease rotational speed of the rotor. An 80-120 m diameter rotor of a state-of- the-art 1-5 MW power wind machine takes 10-20 revolutions per minute. As the generator advisably takes 1500/1600 revolutions per minute, a three-gear speed increaser driving-gear having a minimum of 1/100 gear ratio is required to be fitted between the rotor and the generator. According to the experiences, this driving- gear is the most problematic element in the wind energy industry. Its manufacture is expensive, it has a short life and hinders the start of the wind machine. Such wind machine is worthwhile to be started at growing winds, i.e. at a wind of 5m/s with the help of external energy, as the torque exerted from the wind is higher at this point than the braking torque originating from the friction of the gearbox.

For eliminating the driving-gear, ever more wind machines are produced with a rotor directly rotating a multi-pole generator. This generator generates a so-called raw-current having a frequency that varies with the wind speed, and which can only be fed onto the network following rectification and inversion. Such an apparatus is also complex, expensive and it converts a lot of energy into heat loss. Another idea for eliminating the driving-gear is provided by the concept of pneumatic transmission wind machine, which came up a number of decades prior to the application of the multi-pole generator. A first description of such a wind machine can be found in Swiss patent specification No. CH 282829. In this construction, the hollow blade of the rotor is cut by a plane normal to the radius, through which opening the air is carried out of the blade by means of the centrifugal force. The thus generated inner flow turns a turbine and an electric generator. In the beginning of the 1950's, a 100 kW experimental wind machine was built in the South of England with pneumatic power transmission, based on this patent. The machine and the acquired experiences were disclosed in an article of the March 25, 1955 edition of 'Engineering'. Here, the channel within the blade ends in an opening disposed backward relative to the direction of movement. The airflow passing by the opening with a high relative speed sucks the air from the blade. During the operation of the experimental machine, wind speed and electric power were measured. The power efficiency factor of the machine was 14.5%, meaning that this portion of the wind power was utilized by the machine. At the time, the power efficiency factor of conventional wind machines having been developed for decades was approximately 30%. Based on the results, the concept of pneumatic power transmission was rejected instead of attempting to increase the efficiency of the machine.

In Hungarian patent No. 224 256 multiple solutions are disclosed for improving the wind machine with pneumatic power transmission by increasing the suction effect. An experimental wind machine configured with a two-meter diameter, wing-profile cross sectional suction profile built on the basis of the invention converted 26-28% of wind power into internal pneumatic power.

In known wind machines with pneumatic power transmission, the rotor freely rotates, and is set off by wind speeds as low as 1 m/s. The blades, the head, and the pillar constitute a closed, continuous channel. At the end of each blade, there is a suction profile arranged with a respective air outlet opening, through which air outlet openings the air is caused to exit in consequence of the suction effect and enter the closed inner channel of the wind machine through the bottom of the pillar, rotates the turbine along its path, which in turn rotates the generator. A common problem of known rotors of wind machine with pneumatic power transmissions is that the blade used for converting wind energy into mechanical energy should be as slim as those used in conventional power transmission wind machines. However, the airflow within the rotor can only be effectively guided by means of a blade having greater cross section. To the present, no rotor is able to meet both these requirements.

DESCRIPTION OF THE INVENTION

The primary object of the invention is to improve the rotor of a wind machine with pneumatic power transmission, namely to increase the power efficiency factor of the wind machine. An additional object of the invention is to develop a rotor and a wind machine with pneumatic power transmission which are free of the disadvantages of prior art rotors to the greatest possible extent. It is an object of the invention to develop a rotor which best complies with the double requirements set towards such rotors, namely to efficiently convert wind energy into mechanical energy, at the same time, effectively guiding the airflow within the rotor.

It is the recognition of the invention that the set object can be achieved by a rotor, wherein the air outlet opening is located closer to the axis instead of being disposed at the end of each blade. Thereby, wind energy can be collected from a significant part of the utilized wind area by means of slim, highly-efficient blade portions, while less-efficient blade portions of larger cross-section affect a minor part of the utilized wind area only.

The object of the invention can be achieved by the rotor according to claim 1 and by the wind machine with pneumatic power transmission according to claim 9. Preferred embodiments of the invention are defined in the dependent claims. By means of the inner blade portion according to the invention, air flow to the air outlet opening can be effectively achieved. The suction part can serve to realize a cross-sectional transition between the inner blade portion having an air duct channel and the end part of smaller cross section, which is efficient in terms of rotation. The air outlet opening is preferably positioned at the section of the blade length between one-fourth and three-fourth thereof, more preferably it is located in the middle third of the blade length. In an especially preferred configuration, it is positioned in the vicinity of the half-length of the blade. In this manner, wind energy can be collected by means of slim, highly-efficient blade portions from a significant part - from three-fourth, in the case of a lengthwise halving - of the utilized wind area, and only a smaller - one-fourth, in the case of a lengthwise halving - part of the utilized wind area is affected by less-efficient blade portions of greater cross-section. By repositioning the air outlet opening, however, the peripheral speed generating the suction effect is also reduced - to its half in the case of a lengthwise halving. Therefore, it is especially preferable to also increase the suction effect affecting the air outlet opening, simultaneously therewith. Advisably, this can be achieved by speeding up the outer flow in the vicinity of the suction profile by means of an air deflector profile.

Specific new features of the invention are that three sections can be distinguished along the lengths of the rotor blades. The first section connected to the rotor hub is hereinafter referred to as inner blade section, which is a hollow section forming an air duct channel. The second section is the suction section comprising the air outlet opening and being directly or indirectly connected to the outer, i.e. distal end relative to the rotational axis, of the inner blade section. The third section is a fast- running rotor blade end section of conventional shape and structure, having small cross-section and being directly or indirectly connected to the outer end of the suction section. The respective shapes and sizes of each of the sections are to be determined and formulated by means of experiments such that the suction and air deflector profiles should brake the rotor to the highest possible power and accelerate the inner airflow to the highest speed. During operation, blades and profiles need not and should not be adjusted to the varying wind speed, as both the torque of the blades and the braking torque of the profiles increase in proportion to the third order of speed. ln a preferred embodiment of the invention, the second section of the rotor blade, i.e. the suction profile is encased by an air deflector profile.

Preferably, the third section of the rotor blade is not straight, but is inclined backwards relative to the direction of movement, namely it has a convex inclined shape in the direction (plane) of rotation. In this manner, a simple and passive, therefore, inexpensive storm protection can be achieved. The peripheral speed and rotational speed of the straight blade increase in approximate proportion to the wind speed. The inclined blade flexibly curves and twists, to an extent depending on its rigidity, in consequence of the wind pressure increasing together with wind speed. The variation of shape will cause the blade angle to increase, thereby reducing the increase of rotational speed as a consequence.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary preferred embodiments of the rotor and the wind machine with pneumatic power transmission according to the invention are herebelow described with reference to the following drawings, in which

Fig. 1 is a schematic side view of an embodiment of the rotor and the wind machine according to the invention, as shown in a side view with respect to the direction of the wind,

Fig. 2 is a front view of the line schematic of the rotor of Fig. 1 ,

Fig. 3 is an enlarged schematic front view of the rotor blade of the rotor according to Fig. 2 hereof, with an air deflector profile,

Fig. 4 is a schematic radial view of the air deflector profile,

Fig. 5 is a partial schematic tangential view of the air deflector profile and the rotor blade, and

Fig. 6 is a schematic front view of a preferred embodiment of the rotor according to the invention having an inclined end section.

MODES FOR CARRYING OUT THE INVENTION

Fig. 1 is a schematic representation of a preferred embodiment of the invention depicting a rotor 4 and a wind machine with pneumatic power transmission. A neck 2 mounted for pivotal movement around a vertical axis adjoins the upper end of the pillar 1 of the wind machine. Underneath, air intake openings 15 are formed thereon; above which a generator 6 and a turbine 5 are arranged. The air flows through a section of preferably flat streamlined profile of the neck 2 into the head 3 of the wind machine, and into the rotor's 4 rotor hub 13 having a hollow inner space, and then branching into three directions it flows into the rotor blades 10 connected to the rotor hub 13. The rotor blades 10 according to the invention comprise an inner blade section 7 having an air duct channel adjoining the hollow inner space of the rotor hub 13. The inner blade section 7 according to the invention provides efficient realization of an inner airflow, at the same time less-efficient blade sections of larger cross- section only affect a minor part of the utilized wind area. By way of example, the air duct channel may be configured with an inner blade section 7 having a hollow structure. In case of the hollow structure, it is preferred to have a constant cross- sectional shape along its entire length. In case of a variable-shape longitudinal cross-section, preferably, the cross-sectional area is constant along the length or slowly decreases outwardly. The inner surface of the hollow structure, similarly to its outer surface, is preferably smooth, free of eddy-generating sharp edges or projections, which would otherwise decrease efficiency.

The rotor blades 0 according to the invention further comprise a suction section 8 connected to the outer end, i.e. the distal end relative to the rotational axis, of the inner blade section, which suction section 8 is provided with an air outlet opening 16 facing at least partially in a direction other than the direction of rotation, and being advisably disposed on the blade side opposite the side exposed to the wind and being in flow communication with the air duct channel. The suction section 8 may serve as a cross-sectional transition between the inner blade section 7 configured with an air duct channel and the end section 9 of smaller cross-section, which is efficient in terms of rotation. By way of example, the suction section 8 may also be configured with a hollow structure meeting the above criteria. The end section 9 connected to the outer end of the suction section 8 and has a shape outwardly tapering to a cross-section smaller than that of the inner blade section 7. The configuration of the slim end section 9 having small cross-section is preferably identical with that of the end of the blade of a conventional, fast-running rotor. The end section 9 is not associated with the inner airflow guidance within the rotor blades 10; incidentally it can have any hollow or solid configuration. As an important feature of the end section 9, it comprises a range having a cross-section smaller than that of the inner blade section 7 taken at any point thereof. This is able to ensure that the double requirements according to the invention are met, and it is especially preferable, if the end section 9 has along its entire length a cross-section smaller than that of the inner blade section 7 taken at any point thereof.

When the rotor 4 is revolved by the wind, it causes an overpressure to develop on the front side of the preferably wing profile cross-sectional suction part 8, and depression, suction is caused on its convex back side. This effect causes the air to move within the air duct channel of the inner blade section 7, and guides the energy from the rotor 4 to the turbine 5.

An air outlet opening 16 of the suction section 8 is preferably located at a section between the one-fourth and three-fourth of the blade length, more preferably it is located in the middle third section of the blade length. It was proved to be especially advantageous, when it was positioned in the vicinity of the half-length of the blade. In this manner, wind energy can be collected by means of slim, highly- efficient blade portions from a significant part - from three-fourth, in the case of a lengthwise halving - of the utilized wind area, and only a smaller - one-fourth, in the case of a lengthwise halving - part of the utilized wind area is affected by less- efficient blade portions of a greater cross-section.

Fig. 2 is a front view of the rotor 4 taken against the W direction of the wind, depicting an air outlet opening 16 arranged on the suction section 8.

In the case of the configuration as illustrated in Figs. 1 and 2, the suction effect is lower than in the case when the suction profile is placed at the known place, namely at the end of the blade. According to the invention, by placing the suction section 8 closer to the axis and due to the air outlet opening 16, the peripheral speed generating the suction decreases. In order to improve the power efficiency factor, it is advisable to compensate the decrease in suction effect.

In one preferred embodiment of the invention, the suction effect can be increased by placement of an air deflector profile at the suction section 8 in order to accelerate outer airflow, i.e. to increase the suction effect directed onto the air outlet opening 16 during rotation. The preferred shape and arrangement of the air deflector profile is herebelow described in more detail.

Fig. 3 shows the line schematic of a rotor blade 10 of the rotor 4 presented in Fig. 2 with an air deflector profile 17 placed onto the suction section 8, viewed in an axial direction. The air deflector profile 17 comprises a space portion expanding in a direction opposite the direction of rotation, being in communicating connection with the air outlet opening 16 as will be described herebelow.

Preferably, the air deflector profile 17 arranged in a manner as seen in Figs. 4 and 5 around the suction section 8 to accelerate the airflow is a short pipe profile of rectangular cross-section as viewed from a plane normal to the direction of rotation, which pipe profile is mounted to the rotor blade 10 to rotate therewith. The inner cylindrical mantle surface f1 of the air deflector profile 17 is part of a cylindrical mantle having a radius of r1 and has an opening g1 of a size and configuration identical to those of a profile of the suction section 8 disposed at a distance of radius r1. On the outer cylindrical mantle surface f2 - being a part of a cylindrical mantle having a radius of f2 -, the air deflector profile 17 has an opening g2 of a size and configuration identical with those of a profile of the suction section 8 located at a distance of radius r2. By means of these openings g1 and g2, the air deflector profile is connected to the rotor blades 10, encasing the suction section 8 and the air outlet opening 16 - with its open ends providing for free airflow at the same time. Preferably, the axes of surfaces f1 and f2 of the cylindrical mantle coincide with the rotational axis O.

The air deflector profile 17 also comprises a surface f4 diverging from the plane of rotation in a direction opposite the direction of rotation, and which surface f4 is disposed opposite the air outlet opening 16 (i.e. the latter faces the surface f4) and interconnects the cylindrical mantle surfaces f1 and f2 with one another. This surface f4 constitutes the space portion expanding in a direction opposite the direction of rotation, which space portion causes the suction effect to increase during rotation by means of exerting a Venturi effect, and is illustrated at the upper right part of Fig. 4. The illustrated preferred air deflector profile 17 further comprises a surface f3 approaching the plane of rotation in a direction opposite the direction of rotation, interconnecting the cylindrical mantle surfaces f1 and f2 with one another on the blade side opposite the air outlet opening 16. Preferably, the surface f3 of the air deflector profile 17 is a portion of an Archimedean spiral of 10-30 degree pitch angle falling around the radii r1 and r2 and behaves as if it were a short section of a fan blade. This surface f3 accelerates the rotation, thereby increasing the speed of air traveling into the air deflector profile 17. Preferably, the geometrical axes of the cylindrical mantles and the spiral are identical to the axis of rotation of the rotor 4.

Fig. 6 shows a yet another preferred embodiment of the rotor according to the invention, with an air deflector profile 17 and an inclined outer end, in axial view. The inclined outer end part 12 flexibly curves and twists in consequence of wind pressure increasing together with wind speed. This causes an increase of the blade angle and a reduction of increasing of speed of revolution. The maximum rotational speed can be influenced by the thickness and rigidity of the outer end part 12 having a convex inclined shape in the direction of rotation.

Conventional power-generating wind machines are at a risk that rotational speed of the rotor increases to approximately twice the normal rotational speed when the braking effect of the generator ceases, e.g. in case of a network failure, whereby the centrifugal power acting on the rotating parts will quadruple, leading to terminal breakage in the machine. The damage can be prevented by quick intervention, by placement of a false load on the generator, by an increase of the blade angle or by effective brake operation. On the contrary, wind machines with pneumatic power transmission are not at such risks, as the drag of the suction and air deflector profiles is not dependent on the load of the generator.

Furthermore, a blade angle adjustment apparatus may be advisably built into high power wind machine with pneumatic power transmissions. The use of such blade adjustment apparatus can decrease wind pressure acting on the apparatus in case of storms, such that the blades are turned in a direction normal to the plane of rotation of the wheel, i.e. into a so-called flag position. Another unanticipated advantage is that the wind machine according to the invention will still generate electric energy in this position, i.e. with held-up rotor as well, since the wind blowing through the airflow deflector profile 17 is able to generate inner flow. At this point, the power is low, i.e. only a few percent of the nominal power, similarly to the power yielded from winds less than 5m/s. The two fractional capacities, however, are valuable in networks requiring continuous input, because of the frequent occurrence of such wind conditions.

The wind machine with pneumatic power transmission according to the invention has the advantage of a more simple structure thus less expensive manufacture, longer life-span and therefore more economic operation than that of conventional wind machines.

The invention is not limited to the preferred embodiments described in details above, but further variants and modifications are possible within the scope of protection defined by the claims.

Claims

1. A rotor for a wind machine with pneumatic power transmission, the rotor (4) comprising a rotor hub (3) having a hollow inner space, and rotor blades (10) connected thereto, characterized in that each of the rotor blades (10) comprise - an inner blade section (7) having an air duct channel adjoining the hollow inner space of the rotor hub (13),

- a suction section (8) connected to the outer end of the inner blade section (7), which suction section (8) is provided with an air outlet opening being in flow communication with the air duct channel, and

- an end section (9, 12) connected to the outer end of the suction section (8), tapering to a cross-section smaller than that of the inner blade section (7).

2. The rotor according to claim 1 , characterized in that the air outlet opening (16) is arranged within a blade section being between the one-fourth and three- fourth of the length of the blade.

3. The rotor according to claim 2, characterized in that the air outlet opening

(16) is arranged in a middle third section of the blade length.

4. The rotor according to any of claims 1 to 3, characterized by comprising an air deflector profile (17) arranged at the suction section (8) to increase the suction effect directed onto the air outlet opening (16) during rotation.

5. The rotor according to claim 4, characterized in that the air deflector profile

(17) comprises a space portion expanding in a direction opposite the direction of rotation and being in communicating connection with the air outlet opening (16).

6. The rotor according to claim 5, characterized in that the air deflector profile (17) comprises an inner cylindrical mantle surface (f1) and an outer cylindrical mantle surface (f2), the axes of which cylindrical mantle surfaces (f 1 , f2) are identical with the axis of rotation (O), as well as a surface (f4) diverging from the plane of rotation in a direction opposite the direction of rotation, the surface (f4) interconnecting the cylindrical mantle surfaces (f1 , f2) with one another, wherein the air outlet opening (16) faces the surface (f4).

7. The rotor according to claim 6, characterized in that the air deflector profile (17) comprises a surface (f3) approaching the plane of rotation in a direction opposite the direction of rotation, and interconnecting the cylindrical mantle surfaces (f1 , f2) with one another on the blade side opposite the air outlet opening (16).

8. The rotor according to claim 1 , characterized in that the end section (12) has a convex inclined shape in the direction of rotation.

9. A wind machine with pneumatic power transmission, comprising a pillar (1) and a head (3) mounted to its upper end for pivoting movement around a vertical axis, and a rotor connected to the head (3) for pivoting movement around a horizontal axis, characterized in that the rotor (4) has a configuration according to any of claims 1-8.