Rotary kinetic fluid motors or pumps – With means for controlling casing or flow guiding means in... – Natural fluid current force responsive
Reexamination Certificate
2001-08-13
2003-10-07
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
With means for controlling casing or flow guiding means in...
Natural fluid current force responsive
C415S907000, C416S24400R
Reexamination Certificate
active
06629815
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of Invention
This invention relates to turbines, and more particularly to the support structure of turbines and translation of wind energy to useful mechanical and/or electrical energy.
2. Background of the Invention
Wind turbines are built to harness the wind's energy. A typical wind turbine system for an electricity generation application includes a rotor, i.e., blades, a tower that supports the rotor, a gearbox, a generator, and other equipment including controls, electrical cables, ground support equipment, and interconnection equipment. The rotor converts the energy in the wind to rotational shaft energy. There are two common groupings for wind turbines, the horizontal axis wind turbine (herein “HAWT”) and the vertical axis wind turbine (herein “VAWT”). A wind turbine that has an axis of rotation vertical with respect to the ground and substantially perpendicular to the wind stream is a VAWT. The VAWT allows a generator and other associated relatively heavy equipment to be located on the ground and a tower may not be needed, thus reducing costs of construction. Also, a VAWT does not require a yaw mechanism to turn the rotor against the wind. However, because the VAWT is located near ground level, the wind speeds are typically lower and more turbulent thus reducing the efficiency of the wind turbine. To date, the only vertical axis turbine to be manufactured commercially with any success is the Darrieus machine that is characterized by its C-shaped rotor blades and similar in appearance to an “eggbeater.” The more common wind turbine is the HAWT that incorporates a horizontal axis of rotation with respect to the ground and the axis of rotation is substantially parallel to the wind stream. The HAWT typically has a propeller like configuration with two or three narrow blades. As the wind passes over both surfaces of the blade, the wind passes more rapidly over the upper side of the blade creating a lower pressure and a resulting aerodynamic lift force. The lift force of the blade causes the blade to turn about the center of the turbine.
Turbines with many blades or very wide blades are considered as having a high “solidity,” which is based on the amount of area the blades take up of the circle they define, i.e., swept area, while turning. This allows the blades to turn in low velocity winds. Although turbines with high solidity allow for maximum capture of the wind”s energy, a solid rotor is not capable of sustaining high winds. A wind turbines energy production potential can also be estimated by its rotor diameter that defines the swept area. Many features of a wind turbine”s design affect the energy output of a wind turbine. For example, the power the wind turbine produces at moderate wind speeds is largely determined by blade airfoil shape and geometry. Recent refinements in blade airfoil shapes have increased annual energy output from 10 to over 25 percent. Additionally, the operating characteristics of a wind turbine determine the turbine”s ability to produce power when the wind speeds are in its operating range. The efficiency of the generator and gear box also are significant factors in a wind turbine”s ability to produce power.
The power that can be extracted by a wind turbine is best characterized by the following wind turbine power equation: P=(0.5)(&rgr;)(A)(C
p
)(V
3
)(N
g
)(N
b
)where:P=power (watts) &rgr;=air density (kg/m
3
)A=rotor swept area (m
2
)C
p
=coefficient of performance V=wind velocity (m/sec)N
g
=generator efficiency N
b
=pearbox/bearings efficiency The air density of air at sea level is approximately 1.225 kg/m. The theoretical maximum is 0.59 for a coefficient of performance based on Betz” law for the aerodynamics of wind turbines. However a value of 0.35 is a more reasonable coefficient of performance for a good design. Thus, as can be deduced from the wind turbine power equation, an increase in the rotor swept area is directly proportional to the power that can be extracted from the wind turbine for a given wind velocity if all other variables remain substantially constant. Continuing efforts are being made to increase the size of rotor blades and consequently the rotor swept area. By way of example is the huge German Growian HAWT with a rotor diameter of 100 meters that was designed to deliver several megawatts of electricity. However, the Growian was ultimately a failed attempt to increase the size and capability of power generation of a wind turbine because the Growian wind turbine was taken out of service after less than three weeks of operation. The enormous stresses experienced by the rotor hub during its short operation revealed that the rotor hub was inadequately constructed and effectively irreparable.
Manufacturers generally build turbines with few, long, narrow blades that rotate relatively quickly. The blades are subject to repeated bending and vibration that can result in fatigue and failure of the rotor blades. Metal is known to be susceptible to fatigue and is generally not used as a material for large rotor blades. In addition, the tower supporting the rotor will oscillate back and forth based on the particular configuration of the wind turbine. The rotor blade may amplify the oscillations of the tower thus increasing the stress imposed on the wind turbine. Wind turbine manufacturers validate that their turbines can withstand extreme winds using computer models to simulate the structural dynamics of a wind turbine during high wind conditions. Wind turbines that utilize relatively large blades typically require the stiffness of the blades to be increased and the weight of the blades decreased. The upper limit size of large blades is constrained by the advances in rotor blade materials and the ability of the wind turbine to support the large blades and other components being subjected to extreme dynamic forces.
Accordingly, what is needed in the art is a wind turbine with an increased rotor diameter that overcomes the structural dynamic limitations of the prior art wind turbines and provides an improvement that is a significant contribution to the advancement of the wind turbine art.
It is, therefore, to the effective resolution of the aforementioned problems and shortcomings of the prior art that the present invention is directed.
However, in view of the prior art in at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how the identified needs could be fulfilled.
SUMMARY OF INVENTION
The longstanding but heretofore unfulfilled need for an improved apparatus for supporting turbines is now met. The new, useful, and nonobvious turbine support includes a rotor having a generally vertical axis of rotation, a plurality of blades distributed about the rotor, the blades across their width being shaped and angularly pitched to the flow of air therebetween to effect rotation of the rotor and the blades defining a peripheral boundary of the rotor, a support system for the blades including a single support ring concentric with the vertical axis of rotation and underlying the peripheral boundary of the rotor that utilizes a dual ring design, and a rolling assembly for each blade comprising an upper rolling assembly mounted in rotational supporting association with the support ring so that the mass and forces generated by each blade is substantially supported at the peripheral boundary of the rotor by an upper surface of the support ring.
Distributing the weight of the rotor blades to the periphery, as in the present invention, instead of concentrating the loads at a central axis allows for larger wind turbines that have higher power generation capability to be constructed. The present invention also provides for heavier construction materials to be used in the fabrication of the wind turbine. The peripheral support apparatus of the present invention is adaptable for use with prior art rotor blades and designs. In the following embodiments, rolling support assemblies and support mechanisms are
Hopen Anton J.
Look Edward K.
McCoy Kimya N
Smith & Hopen , P.A.
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