1. Technical Field of the Invention
This invention relates to airfoil shapes and their mounting, and to add-on blades to enhance the performance of windmills.
2. Description of the Art
The existing art focuses on a very seductive windmill aerodynamics sometimes called ‘planar flow’, ‘kiting’ or my own deflected air flow as a “squished” sheet of air' that accelerates after impacting against virtually flat to the wind blade(s). A body of moving air (wind) can be squished down to a very thin sheet that is moving off the trailing edge of a blade at up to 10 times the relative speed of the incoming air to the departing rotating blade. The currently used blade design force dynamics produces this great rotating speed, but with little usable torque.
I have invented a new airfoil mounting performance principle (optimal center of pressure caused angle of attack positioning). The new aerodynamics means any windmill will be dramatically improved at much lower air speeds.
The preferred embodiments are disclosed in the attached drawings, from which it will be appreciated that I have invented a high-speed airfoil for use on the rotor of a windmill which also can be mounted in front of an existing rotor. The blade has a leading edge lip ahead of the squish—to make the swish—with good torque.
The blades may be approximately one half the diameter of existing blades—when used in the “piggy back” mounting (in front of standard blades) as shown in
My new blades add power, while providing some braking to reduce speed. This new airfoil design (with optional hinged blade mounting mechanics) recognizes and enhances the ‘squish’ power potential with two innovations.
a) initially (for more start-up power) hold the blade at the higher torque providing lower angle of attack to wind from approximately 80 degrees to 65 degrees, and
b) as (if) the lower torque speed up occurs transferring the air pressure (squish) resultant more directly against the ‘blade edge’ (now with leading edge air catcher lip) geometric pivoting raises the angle of attack to the high speed position—without springs or other extra force means.
In small diameter wind turbines it is more effective when the blade is twisted so that the blade root is at an angle of attack of 10 to 15 degrees to rotation; most preferably 11 to 14 degrees; and the outer (faster) tip is at 8-10 degrees less to the plane of rotation.
In larger diameter mills blade twist is less critical, so production costs can be reduced by having a constant angle (no twist). This constant angle is best in the 7-10 degree angle to the plane of rotation (80-83 degrees to the wind).
Referring to
A typical blade cross-section taken as indicated by the lines and arrows 4-4 in
In addition, I provide end caps 26
The hub 12 is flat (that is, at 90 degrees) to the wind “AIR FLOW” as shown in
In the preferred embodiment, the lip may be shaped as at 20,
Test results are shown in the following chart.
Comparison of 4.5 inch air foils in a small wind tunnel at a wind speed of 15 mph
These results show that the new aerodynamics squish/swish (NASS) flat against the wind positioning (between 90 and 75 degrees) out performs the old aerodynamics and standard air foils by a ⅔ increase.
In the normal angle of attack range, the NASS air foil out performs the standard airfoil by 25-35%. More recent testing suggests a preferred range of 78 to 83 degrees.
As can be seen, the NASS is a fast rotating wind turbine air foil that has vastly higher torque than standard air foils.
While the blade may be mounted in a fixed position; as shown by the nut and bolt arrangement designated generally at 22
The preferred location of the blades with respect to the center line of the shaft is off-center. Referring to
End caps 26 at the outer edges of the blades 10
The air foil may also be mounted in front of an existing prior art rotor blade 30 of a wind turbine 32 as shown in
From this description it has been shown that I have invented a windmill having blades mounted on a shaft, at least some of which blades have a transverse cross-sectional shape having a predominately flat chord section, said blades being mounted such that the chord section lies in a plane that is substantially at 90 degrees to the axis of the shaft. The plane may be positioned at an angle in the range of 78 to 87 degrees to the axis of the shaft. Furthermore, the blades can be positioned off-center to the axis of the shaft.
The blades have a leading edge positioned in the range of ¼ to ⅓ the width of the blade from the axis of the shaft.
The windmill may be mounted in front of the blades of a wind turbine.
I have also invented a method of mounting windmill blades on the shaft of a windmill, at least some of which blades have a transverse cross-sectional shape having a predominately flat chord section, comprising mounting said blades such that the chord section lies in a plane that is substantially at 90 degrees to the axis of the shaft.
The plane may be at an angle in the range of 78 to 87 degrees to the axis of the shaft.
The blades may be positioned off-center to the axis of the shaft.
The blades have a leading edge positioned in the range of ¼ to ⅓ the width of the blade from the axis of the shaft.
The windmill may be mounted in front of the blades of a wind turbine.
This application is a Continuation-in-Part of my prior Provisional application entitled Squish swish windmill blade to enhance performance, Ser. No. 60/673,508, filed Apr. 21, 2005 the disclosure of which is incorporated herein by reference as if fully set forth.
Number | Name | Date | Kind |
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2458419 | Reinmann | Jan 1949 | A |
4171929 | Allison | Oct 1979 | A |
4877374 | Burkett | Oct 1989 | A |
5711653 | McCabe | Jan 1998 | A |
7186083 | Bayly | Mar 2007 | B2 |
Number | Date | Country | |
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20060239821 A1 | Oct 2006 | US |
Number | Date | Country | |
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60673508 | Apr 2005 | US |