Fluid reaction surfaces (i.e. – impellers) – Plural impellers having relative movement or independent... – Coaxial rotation
Reexamination Certificate
2002-04-12
2004-05-18
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Plural impellers having relative movement or independent...
Coaxial rotation
C416S22700R
Reexamination Certificate
active
06736600
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a rotor, which in operation is flown through by a fluid in a main flow direction, the rotor having a rotor blade arranged rotatable around a rotor axis and extending at least partially away from the rotor axis into the fluid, the rotor blade being split into at least two partial blades at a predetermined distance from the rotor axis, one partial blade being curved in a turning direction away from the rotor blade and the other partial blade being curved against the turning direction away from the rotor blade, the two partial blades being connected to form a loop.
BACKGROUND OF THE INVENTION
From the prior art, rotors for the generation of thrust or propulsion or for the generation of an angular momentum are known and comprise in the first case propellers and marine propellers, blowers, fans, and ventilators etc., and, in the second case, flow-driven repellers, turbines and windmills. In the case of marine or aeronautic propellers, a rotor blade mounted on a hub is turning around an axis of revolution and generates a propulsion force due to its profile shape or due to its incidence while rotating around the axis of revolution. Averaged over one revolution, the propulsion force extends essentially parallel to the axis of revolution and propels the ship or the plane. In the case of helicopter rotors, a shifting of the rotor blades during the rotation around the axis of revolution may generate a propulsion force, which is inclined relative to the axis of revolution. In this context, the main flow direction is understood as the direction, under which the flow passes the rotor if the rotor is reduced to a plane in a far-field view.
The efficiency of rotors is lessened by flow losses in the form of vortex generation, swirl, and—if the rotor is operated in liquid media—by cavitation. Often, sound emission is a problem. The noise generated by marine or aeronautic propellers, by helicopter rotors, wind mills, various fans and blowers, for example in air conditioning systems, contributes significantly to today's acoustic environmental load.
From the prior art, rotors of the general type are known that, in comparison to previously known rotors, lead to an improved efficiency and to a reduction of the sound emission or of the sound generation.
For example, a rotor is known from DE 42 26 637 A1 having a rotor blade, which is split into two partial blades. This rotor may reduce the vibrations during operation.
Another rotor is known from DE-PS 83050. This rotor leads to an increase in the reaction pressure.
In U.S. Pat. No. 1,418,991 a rotor is described having a rotor blade that is split into two partial blades at a distance from the axis of revolution, the partial blades extending in and against the direction of rotation of the rotor with respect to the rotor blade. The rotor of U.S. Pat. No. 1,418,991 may reduce the flow resistance.
Rotors of this general type are also known from U.S. Pat. No. 3,504,990 and from U.S. Pat. No. 4,445,817.
The rotor shown in U.S. Pat. No. 3,504,990 has support arms that do not affect the flow. At the ends of the support arms there is mounted an annular surface, which generates the propulsion of the rotor over its circumference or perimeter.
From U.S. Pat. No. 4,445,817, there is known a rotor having rotor blades that are made from a planar rotor stand extending perpendicular to the main flow direction and from a strip-shaped rotor blade. Each strip-shaped rotor blade is bent and fastened tot the rotor blade coming next in the turning direction. This rotor, too, generates propulsion exclusively at the outer perimeter of the rotor blade.
Further, in DE 197 52 369 a propulsive body is shown that has an end lying transverse to the flow direction and being split while forming a loop.
In EP 0 266 802 a curved-surface propeller is shown, of which the conveying blades form sections of an envelope of a cone. The curved surface and the conveying blades each surround holes through which the conveyed mass flows.
The disadvantages of the rotors known from the prior art is that the improvements they achieve in the efficiency and in the noise emission are no longer sufficient for today's applications.
SUMMARY OF THE INVENTION
Therefore, it is the objective of the present invention to improve the initially mentioned rotors by simple design measures so that their efficiency is increased.
In particular, it is intended that, besides having an improved efficiency, the rotor generates less noise and is thus particularly beneficial to the environment.
This object is solved by a rotor of the initially mentioned type on one side in that a propulsion force or an angular momentum around the rotor axis is generated in operation by the rotor blade, and in that the rotor axis passes through the loop area enclosed by the loop.
On the other side this object is solved for a rotor of the initially mentioned type in that a propulsion force or an angular momentum around the rotor axis is generated in operation by the rotor blade, and in that the leading edge of the one, front, partial blade is situated in the main flow direction upstream of the leading edge of the other, rear, partial blade at least in an area close to the rotor blade.
This solution is simple and results in a significant noise reduction with the rotors.
By the connecting or combining the partial blades to a loop, the circulations changes continuously along the blade contour from one partial blade to the other. The circulation must be zero at one point along the blade contour, where the sign of the circulation between the two partial blades changes. Thus, the loop forms a means by which the circulation of the rotor over the whole perimeter of the loop and therefore in the trailing vortices generated in the wake is distributed uniformly. Thereby, a more even distribution of the circulation may be reached along the rotor blade and along the loop-forming partial blades than is known in the prior art. The vorticity is distributed spatially over the whole blade perimeter or circumference of the loop, which leads to decreased losses due to vortex generation and to a decreased generation of flow noise.
The loop-shaped ring closure of the partial blades also results in a high mechanical stability of the rotor. This may reduce the structural weight and may lead to an altogether more filigree design. Further, the depth or chord of the profile may be reduced at those parts of the loop formed by the partial blades, which parts only make a small contribution to the thrust. This may reduce the frictional resistance.
If, in the case of a single-bladed propeller, the axis of revolution passes through the plane of the loop, imbalances during the rotation of the propeller may be avoided by this simple design measure.
For simple applications, such as simple fans or ventilators or toy planes or toy wind wheels, the rotor blade and the partial blades may be formed for example as inclined flat planes; for technically more complex applications, such as airplane propellers or ship propellers, the rotor blade and the partial blades may be formed by wing-like profiles with a particular thickness distribution and camber. A profile that, depending on the local flow conditions, changes along the rotor blade and along the partial blades, leads to particularly advantageous flow characteristics and to an improved efficiency. In this context, the change of the blade depth and of the local angle of attacks may be adapted to the local flow conditions.
The generation of thrust or propulsion, or of an angular momentum by the rotor blades themselves is essential to the invention. By this principle, the inventive rotor differs from the rotor of U.S. Pat. No. 4,445,817. Although this rotor may form a loop, the rotor disclosed there does not have rotor blades that extend away from the axis of revolution into the flow and generate thrust. Rather, the loop-shaped ribbon is held by support arms, which must interact with or disturb the fluid flow as little as possible. The rotor of U.S. Pat. No. 4,445,817 generate
Edgar Richard A.
Look Edward K.
Marshall & Gerstein & Borun LLP
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