Aerovortex mill

Description

Aerovortex Mill: A Wind Mill using a device which generates high-speed air jet streams or vortices behind the rotor blades, inducing the increase of the free stream velocity of air (Wind) hitting the rotor blades. The vortex generator device is given the name VIASAD which stands for Vortex Induced Air Speed Amplification Device. The jet-stream generator device is given the name JETIASAD which stands for JET stream Induced Air Speed Amplification Device. The Aerovortex Mill using the VIASAD/JETIASAD device, can generate higher power output in regions with low mean annual wind speeds.

CROSS-REFERENCE TO RELATED APPLICATIONS

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STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX

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BACKGROUND OF INVENTION

Wind constitutes one of the major sources of renewable or “green” energy production. Windmills are widely used all over the world in order to harness this power from the wind.

Currently there are two types of windmills: vertical axis and horizontal axis machines. They both use some kind of propeller which is primarily used for extracting or converting the Kinetic Energy of the wind into mainly two types of energies: (1) Electrical energy (Power generators) and (2) Potential energy of the water (Water pumps). These propellers or rotors are either drag-based or lift-base devices. The drag-based rotors have slower rotational speeds than the lift-based devices. Generally the lift-based devices are a lot more efficient than the drag-based devices, and consequently the wind power generators are mostly lift-based devices.

A lot of research and development has been done by a number of companies around the world in order to improve the efficiency and performance of lift-based windmills. This lead to a number of considerable advances in this field, primarily focused on the following three areas:

• • 1. The aerodynamics of the rotor blades. Basically maximize the Lift-to-Drag ratio of the rotor blades.
  • 2. Wind mill yaw control and rotor blade pitch control.
  • 3. Improvement of the gear system which amplifies rotation from the main rotor with the blades to the generator. Lately a gearless design has been introduced. This advancement drives down considerably the maintenance costs, since the gear system is one of the most sensitive parts and wares out the most.

How many advances have been achieved in Windmill technology, even the most advanced and efficient Windmills can only operate in areas with mean annual wind speeds exceeding 4.5 m/s. Only then, they can generate enough useful energy or electricity to justify their extremely high cost. As a result, areas with low mean annual wind speeds (below 4.5 m/s), are left with no reliable and efficient enough technology to harness the energy of the wind.

The recommended invention/mechanism, does not radically changes the most widely used way of harnessing the wind energy, which is the use of horizontal axis lift-based wind turbines. This technology has been in development the last three decades and it has reached very high standards of efficiency. The recommended invention builds on this existing and proven technology and renders it more efficient and hence a lot more attractive. Exactly for this reason, from a practical and financial point of view, the implementation of the invention becomes very feasible and economically viable.

BRIEF SUMMARY OF THE INVENTION

The use of a vortex generator device to generate vortices in the vicinity behind the wind mill rotor blades, can render the conventional wind mill a far more efficient device at low wind speeds. The same applies for a mechanism blowing high-speed air jet streams behind the wind mill rotor blades. By using these devices, the wind mill will be able to operate in an environment with winds in the lower speed spectrum (1 m/s<v<5 m/s) and at the same time produce electricity (power) efficiently and cost effectively.

The vortices as well as the jet streams generated by the proposed mechanism or device, in the vicinity behind the wind mill rotor blades, help accelerate the free stream air by lowering the static pressure in that region and hence inducing a suction effect. As a result, the wind mill's output performance is improved.

The vortex generator mechanism is given the name VIASAD which stands for “Vortex Induced Air Speed Amplification Device”. The jet-stream generator device is given the name JETIASAD which stands for “JET stream Induced Air Speed Amplification Device”. The Wind Mill carrying the VIASAD/JETIASAD device, is called: “Aerovortex Mill”.

In simple terms, the concept mechanism will especially benefit areas with low mean annual wind speeds. The production of electricity at low wind speeds by an Aerovortex Mill, will be comparable to that produced at a lot higher wind speeds with current wind mill technology not using the VIASAD/JETIASAD device.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1: Swimming/Propulsion of a human swimmer in water. The feet stroke up and down in the water generating ‘barrel’ like trailing vortices.

FIG. 2: Fish/Shark swimming. The periodical (left/right) movement of the shark's caudal fin shreds trailing vortices. A jet stream flows in between the trailing vortices with a direction opposite to the direction of travel of the shark.

FIG. 3: Insect flapping flight. Shredding of vortices which induces a jet stream on top of the flapping wings.

FIG. 4: 3D view of a type1 VIASAD/JETIASAD Device: Two convergent wind tunnels (Contraction), each with a single exhaust nozzle behind the rotor of a wind mill.

FIG. 5: 3D view of a type1 VIASAD/JETIASAD Device with two convergent wind tunnels. Generated vortices, one from each exhaust nozzle and with a direction of flow perpendicular to the plane of rotation of the rotor. A horizontal flap controls the vortices flow.

FIG. 6: 2D side view of a type1 VIASAD/JETIASAD Device with two convergent wind tunnels: A generated vortex flows from a single exhaust nozzle.

FIG. 7: 3D view of a type2 VIASAD/JETIASAD Device with four convergent wind tunnels: Accelerated air flow through the nozzles is ejected from four exhaust nozzles behind the rotor of a wind mill.

FIG. 8: 2D side view of a type2 VIASAD/JETIASAD Device with four convergent wind tunnels: Two generated vortices flow out of double exhaust nozzles, one on each side of the wind mill (Right/Left sides).

FIG. 9: 3D view of a VIASAD/JETIASAD Device with two convergent wind tunnels: A casing or walls isolate the space behind the wind mill rotor.

FIG. 10: 3D view of a type3 VIASAD/JETIASAD Device with two convergent wind tunnels, one on each side of the wind mill rotor. The exhaust nozzle of the first wind tunnel blows air behind the top half of the rotor and the exhaust nozzle of the second wind tunnel blows air behind the bottom half of the rotor. Generated vortices flow along a direction parallel to the plane of rotor rotation.

FIG. 11A: 2D TOP view of a type3 VIASAD/JETIASAD Device with two convergent wind tunnels on each side of the wind mill rotor.

FIG. 11B: 2D FRONT view of a type3 VIASAD/JETIASAD Device with two convergent wind tunnels on each side of the wind mill rotor.

FIG. 11C: 2D SIDE view of a type3 VIASAD/JETIASAD Device with two convergent wind tunnels on each side of the wind mill rotor.

FIG. 12: 3D view of a type4 VIASAD/JETIASAD Device with its wind tunnels converging to a unified exhaust nozzle behind the wind mill rotor. The flow direction of the generated vortices makes an angle with the rotor plane.

FIG. 13A: 2D TOP view of a type4 VIASAD/JETIASAD Device.

FIG. 13B: 2D FRONT view of a type4 VIASAD/JETIASAD Device.

FIG. 13C: 2D SIDE view of a type4 VIASAD/JETIASAD Device.

FIG. 14: 3D view of a type5 VIASAD/JETIASAD Device with two convergent wind tunnels, one on each side of the wind mill rotor. The exhaust nozzle of the first wind tunnel blows air behind the top half of the rotor and the exhaust nozzle of the second wind tunnel blows air behind the bottom half of the rotor. Double counter-rotating vortices are exiting each exhaust nozzle of the convergent wind tunnels.

FIG. 15: 3D view of a type6 VIASAD/JETIASAD Device with its two wind tunnels converging to “scissors” like exhaust nozzles.

FIG. 16: 3D view of a type6 VIASAD/JETIASAD Device with one of its two converging wind tunnels. The generated counter-rotating vortices induce a jet stream of air through the “scissors” like exhaust nozzle.

FIG. 17: 2D TOP view of a type7 VIASAD/JETIASAD Device. Swept-forward wings at an angle of attach to the incoming wind generate vortices at their roots, behind the wind mill rotor.

FIG. 18: 2D SIDE view of a type7 VIASAD/JETIASAD Device with swept-forward wings at an angle of attach to the incoming wind.

DETAILED DESCRIPTION OF THE INVENTION

The paragraphs 0012 to 0019 that follow, provide necessary background information related to the invention in order to be fully understood. This introductory information naturally leads to a detailed description of the invention.

The Power Available in the Wind:

The following formula gives the total power contained in the Wind of a certain speed and through a given cross-sectional area.
P_W=(½)*(Density)*A*V³

• P_W=Power available in the wind (W)
• Density=Density of air (Kg/m³).
• A=Swept rotor area (m²)
• V=Wind speed (m/s)
  Power Produced by a Wind Mill:

The following formula calculates the power output from a wind mill given the available power in the wind.
P_M=C_P*P_W

• P_M=Power available from the wind machine (W)
• C_P=Coefficient of performance of the wind mill
  C_P depends on a number of factors like the type of the wind mill (drag-based or lift-based) and the rotor used. The drag-based devices achieve their maximum performance efficiency at low wind speeds and hence low tip-speed ratio. On the other hand, the lift-based devices achieve their maximum performance efficiency at high tip-speed ratios. However, it is very important to note here that the maximum performance output achieved by the lift-based devices is a lot higher than the corresponding performance output given out by the drag-based devices.

According to the Betz Law (Known as Betz limit) there is a maximum value of C_P which is equal to 59.3%. In practice, though, real wind rotors have maximum C_P values in the range of 10%-40%.

Based on the formula of paragraph 0012, the Power which can be harnessed from the wind by propellers is heavily dependent on the wind speed (speed cubed).

The Wind as an Energy Resource

Large areas of the world appear to have mean annual windspeeds below 3 m/s, and are unsuitable for wind power systems, and almost equally large areas have windspeeds in the intermediate range of 3-4.5 m/s where wind power may or may not be an option. In these areas, drag-based wind machines are the most efficient but rarely are used for power generation because of their low rotational speeds.

Those areas with mean annual windspeeds exceeding 4.5 m/s are the most economically competitive for power generation. In these areas lift-based devices are being used, because they are usually more efficient than drag-based devices, even though at extremely high wind speeds their efficiency considerably drops.

In summary, the most efficient current technology based on lift-generating rotor wind mills, can operate in areas with mean annual wind speeds exceeding 4.5 m/s and generate enough useful energy or electricity to justify their extremely high cost. On the other hand, areas with low mean annual wind speeds (below 4.5 m/s), are left with no reliable and efficient enough technology to harness the energy of the wind.

The Inspiration

The source of inspiration for the recommended concept device (VIASAD/JETIASAD), consists of specific lessons from nature which can be summarized as follows: The Hydrodynamic mechanisms of Aquatic Locomotion used by fishes to propel their way through fluids and the Flight propulsion mechanisms used by birds and insects moving through Air.

1. Aquatic Locomotion

The Momentum-Impulse Couple of Vortex REAR DRIVEN Bodies:

The rear body parts (feet, caudal fin) can both (A) accelerate the vortex flow generated by the body moving through the water and/or (B) generate vortices.

• • A. The vortex flow generated by the body of the fish is allowed to expand laterally and eventually it is beaten by the caudal fin. This effectively restricts its path and hence the vortex flow is being accelerated.
  • B. The rear body parts preform the aquatic surroundings by applying some work on the water, which in turn stores this energy. The preformed water masses flow into the zone of the underpressure creating a rolling vortex (Ungerechts et al). Due to the high geometrical organization, vortex ‘carry a high amount of momentum in relation to the energy spent for their production’ (Lighthill, 1969). This generated trailing vortex induces a velocity field which is influencing the flow in front of the moving body.

1.1 Human Swimmer

• • The feet strokes up and down in the water generate ‘barrel’ like trailing vortices. It looks as if the human body is translating through the water between rollers. See FIG. 1.

1.2 Shark

• • The periodical (left/right) movement of the shark's caudal fin shreds vortices on each side which are rotating in an opposite sense (Blickman, 1992). Due to the lasting rotation of the generated vortices, a jet stream is produced. This jet stream flows in between the trailing vortices and with a direction opposite to the direction of travel of the shark (backwards). The thrusting impulse responsible for pushing the shark forwards is a reaction to this jet stream (similar to the jet stream behind modern aircraft). See FIG. 2.
    2. Flight Propulsion

2.1 Insect Flapping Flight

• • The very slow velocities by which insects fly in the air and hence the low Reynolds numbers associated with these velocities, do not justify the lift generated on their wings in order to keep them airborne. For this reason, insects use flapping along with rotational movement of their wings, in order to increase the airflow in the vicinity of each of their flapping wings and in this way generate the required lift so that they are able to fly. The way this is achieved is by generating wing leading-edge vortices (LEV) which in turn produce a jet stream on top of the wing. See FIG. 3.
    The Invention

A device which increases the speed of Air Flow (Wind) in the vicinity of the wind mill rotor blades. Based on the formulas given in paragraphs 0012 and 0013 above, the power output of a wind mill is proportional to the 3^rd Power of the speed of the air stream hitting the wind mill rotor blades. Consequently, by increasing the speed of the air seen by the rotor blades, the power output will surpass the level corresponding to the free stream air speed.

The proposed device generates a high-speed jet stream or a system of vortices behind the wind mill rotor blades (downstream). These vortices lower the static pressure in the region where they are generated and hence they are inducing a suction effect. Also, due to the high geometrical organization, these vortices carry a high amount of momentum, which helps accelerate the free stream air hitting the wind mill rotor blades (upstream). This is the reason I call this device: VIASAD, which stands for “Vortex Induced Air Speed Amplification Device”. The version of this device which blows air jet streams behind the rotor blades, is called JETIASAD: “JET stream Induced Air Speed Amplification Device”.

The Wind Mill operating with the help of the VIASAD/JETIASAD device, I call it an “Aerovortex Mill”.

The mechanism described above, will render the wind mill a far more efficient device at low wind speeds. It will be able to operate in an environment with winds in the lower speed spectrum (1 m/s<v<5 m/s) and at the same time produce electricity (power) efficiently and cost effectively.

In simple terms, the concept device will especially benefit areas with low mean annual wind speeds. The production of electricity at low wind speeds by an Aerovortex Mill, will be comparable to that produced at a lot higher wind speeds with current wind mill technology not using the VIASAD/JETIASAD device.

Specification:

The VIASAD/JETIASAD device helps increase the speed of air flow hitting the wind mill rotor blades by inducing suction in the vicinity behind the rotor blades, and it is based on the following (A)Functional principles and (B)Design variations:

A. Functional Principles:

The principles described below, provide valuable insight into the functionality of the VIASAD/JETIASAD device. They can be very helpful in building and operating the device. Essentially, the VIASAD/JETIASAD device makes use of the Wind in a number of steps/stages as described below:

• • (1) Use of a contraction or an open-circuit wind tunnel in order to accelerate a large mass of incoming free stream air flow.
  • (2) Vortex generators are positioned in the incoming air flow which is accelerated by the open-circuit wind tunnel.
  • (3) The vortex generator can take various forms and/or configurations. The following are a few examples:
    • Stationary swept-forward wings.
    • Flapping swept-forward wings.
    • Fins like the shark's caudal fin.
    • Fences positioned vertically or at an angle along the walls of the open-circuit wind tunnel.
  • (4) Generate a vortex or a number (system) of vortices positioned in a certain pattern/configuration (VIASAD) or blow high-speed jet streams (JETIASAD) in the space behind the wind mill rotor blades.
  • (5) For the generation of the above vortices, make use of air masses in front and on the side, away from the wind mill rotor blades circumference. The use of air masses from the undisturbed free stream away from the buffered area behind the rotor blades, maximizes the strength of the generated vortex and as a result it contributes to its increased effectiveness. The same applies to the generation of air jet streams.
  • (6) Allow some spacing for the generated vortices to expand laterally (perpendicularly to the direction of flow).
  • (7) Use horizontal and/or vertical flaps or other devices in order to control/restrict the lateral expansion of the generated vortices.
  • (8) By restricting the flow path of the generated vortices, the flow accelerates and consequently the following two effects take place:
    • The angular momentum of the rotating air masses increases.
    • The static pressure within the accelerated vortices drops.
  • (9) Use walls in order to isolate the region behind the wind mill rotor blades. Basically, this will only allow incoming air masses hitting the wind mill rotor blades to be sucked in the region with the generated vortices.
  • (10) The air masses moving within an imaginary tube with cross-sectional area described by the disc plane of the rotating wind mill rotor blades, flow into the underpressure of the generated rolling vortices or the blowing air jet streams behind the rotor blades
  • (11) The induced jet stream as a result of the vortex suction effect (or jet stream suction effect) on the wind, influences the air flow in front of the wind mill rotor blades by increasing its incoming speed and ultimately increasing the energy content of the air masses hitting the rotor blades. This effectively raises the power output of the wind mill, because it is proportional to the power (or energy) content of the air flow masses hitting the wind mill rotor blades.
    B. Design Variations:

The following Design variations describe a number of different configurations for the VIASAD device. All recommended designs, aim at generating vortices and/or air jet streams behind (or downstream) the wind mill rotor blades, which induce acceleration of the wind hitting the rotor blades (In the vicinity of the wind mill blades).

(1) Stationary Swept-Forward Wings. (See FIGS. 17-18)

Location/Position:

I. Case1: A single pair of wings is used. The horizontal plane of the wings lies on the same height as the horizontal diameter of the wind mill rotor disc.

• • II. Case2: Two pairs of wings are used. The horizontal plane of each pair of wings lies at a height, which makes an offset (up/down) from the horizontal diameter of the wind mill rotor disc
  • III. Wing tips are preferably well ahead of the vertical plane described by the rotating wind mill rotor blades
  • IV. Wing root located behind the wind mill rotor blades.

Functionality:

• • I. Spanwise flow of air develops, originating at the wing tips and moving towards the root of the wings.
  • II. By increasing the angle of attack of the wings to the wind, a pressure differential is created between the lower and upper surfaces of the wing. With the low pressure on the lower surface and the high pressure on the top surface, upwash builds up which results in air flow rolling up the edge along the root of the wing.
  • III. The low pressure within the core of each of the pair of vortices generated along the wing roots, as well as the impulsive effect of the air masses rotating and moving backwards in the vortices, result in a suction effect.
  • IV. The suction generated by the vortices, and with the help of the wind direction, accelerates the air flow from the space in front of the wind mill rotor blades towards the space behind them.
  • V. The influence on the air hitting the rotor blades can be amplified with the use of a containment or walls preventing the influx of air masses from the sides entering the space where the vortices are generated.
  • VI. Use flaps or other surfaces in various forms (flat, cylindrical) in order to restrict the path of the vortices and hence increase the speed of the rotating air within them.

(2) Flapping Swept-Forward Wings.

Location/Position:

• • Similar to Design Variation (1).

Functionality:

• • Similar to Design Variation (1). One extra functionality parameter can be used and/or varied: Flapping frequency.

(3) Fins Like the Shark's Caudal Fin.

(4) Contractions Where Air is Initially Accelerated and Eventually Diffused in a Rolling Vortex or a High-Speed Jet Stream. These Contractions are Basically Open Circuit Converging Wind Tunnels. See FIGS. 4-16.

Location/Position:

• • I. Case1: A single pair of contractions generating a pair of vortices. The intake sections of the tunnels/contractions are outside the disc area of the rotating wind mill rotor blades. They can be placed either ahead or behind the plane of the rotating wind mill rotor blades.
  • II. Case2: Two pairs of contractions generating two pair of vortices. The intake sections of the tunnels/contractions are outside the disc area of the rotating wind mill rotor blades. They can be placed either ahead or behind the plane of the rotating wind mill rotor blades.
  • III. The center line of the contractions will be either curved or straight.
  • IV. The exhaust section of the diffuser of each contraction will end up behind the wind mill rotor blades.

Functionality:

• • I. Free stream air flows into the intake section of the contraction and eventually is diverted towards the exhaust section.
  • II. By diverting the air flow from a large cross sectional area to a small cross sectional area, the air is accelerated (Bernoulli's Principle).
  • III. The air flow exiting the exhaust section of the diffuser, hits a vortex generator and rolls into a vortex.
  • IV. The low pressure within the core of the vortices generated, as well as the impulsive effect of the air masses rotating and moving backwards in the vortices, result in a suction effect.
  • V. The suction generated by the vortices, and with the help of the wind direction, accelerates the air flow from the space in front of the wind mill rotor blades towards the space behind them.
  • VI. The influence on the air hitting the rotor blades can be amplified with the use of a converging nozzle placed behind the rotating wind mill blades and in front of the generated vortices.