Patent Application
20240418089
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The present disclosure generally relates to rotating airfoil designs; more specifically, to a substantially unique fan blade having novel air movement characteristics.
In general fan and propeller blade designs comprise angled surfaces or upper and lower surfaces of differing shapes and sizes that operate to impart fluid movement (i.e., air movement) as a result in the differential pressures on each surface. For example, a fan blade or propeller with a relatively flat lower surface and curved upper surface area (i.e., camber) will generate air movement by the higher pressure on the lower surface of the fan blade and the lower pressure on the upper surface of the fan blade created as the air travels over the differing surface areas. This pressure differential is increased with increasing angle of incidence in addition to the contribution of the airfoil camber. As used herein, “angle of incidence” generally means the local blade incidence relative to the plane of blade rotation.
The intent of the novel blade disclosed herein is to generate greater amount of air movement at a reduced angle of incidence as compared with conventional blades which generally have fixed incidence angles between 10 and 15 degrees. The current invention introduces performance improvements over traditional blade design by providing a substantially novel blade with a primary, longer chord airfoil with a lower, offset, secondary smaller chord airfoil in a slotted, configuration. A twist is imparted throughout the span of the blade to optimize the angle of incidence of the blade. This design minimizes airflow separation, increases downward air movement, and achieves significantly better performance than a traditional flat bladed fan design. The intent of this design is to generate improved performance at a reduced angle of incidence relative to a flat blade with no camber.
Any documents or publications cited in this disclosure are incorporated by reference in their entirety, to the extent they are not inconsistent with the explicit teachings set forth herein.
The novel fan blade generates increased air movement perpendicular to the plane of rotation. The air movement mechanism is based on increased pressure differential between the upper and lower surface of the primary airfoil which is based on increased camber and the addition of a secondary airfoil. The slotted configuration between the primary airfoil and secondary airfoil allows for higher pressure fluid from the lower surface of the primary airfoil to flow through the slot and re-energize the flow along the upper surface of the secondary airfoil, resulting in attached flow and increased re-direction of the flow in the thrust or axial direction. This design is more effective at producing thrust as compared to the flat airfoil design.
The novel blade design includes a primary airfoil having a root section which is adjacent to the rotating hub, a tip opposite the root, a leading edge, and a trailing edge. The primary airfoil has an angle of incidence relative to the plane of rotation of the blade of between 3° and 25°.
A secondary airfoil is situated generally aft and below the primary airfoil having a root generally proximate the root of the primary airfoil, a tip opposite the root and generally proximate the tip or the primary airfoil, a leading edge, and a trailing edge. The secondary airfoil is disposed below and connected proximate the trailing edge of the primary airfoil. The secondary airfoil has an angle of incidence which varies along the span of the blade relative to the plane of rotation of the blade of between about 5° and 40°.
The novel blade design further includes a plurality of vertical supports connecting the primary airfoil to the secondary airfoil. The vertical supports are connected to the bottom of the primary airfoil at the top of the support and connected to the top of the secondary airfoil at the bottom of the support.
Both the primary airfoil and the secondary airfoil can include a twist to provide a lower angle of incidence towards the tip.
The novel blade design can include an angle of incidence of the primary airfoil between about 10° and 30° proximate the root and between about 3° and 8° proximate the tip.
The novel blade design can include an angle of incidence of the secondary airfoil between about 20° and 30° proximate the root and between about 8° and 20° proximate the tip.
The novel blade can rigidly affixed to a rotating hub wherein there is no variation in pitch of the overall blade structure or it may be affixed to a variable geometry hub wherein its pitch may be changed and controlled by a pitch controller, such as, for example a prop governor or a constant speed unit.
Accordingly, it is an object of the present invention to provide a fan blade having a primary airfoil and smaller secondary airfoil positioned aft and below the primary airfoil to increase lift. The increase in lift results in an associated increase in downwash below the blade.
It is a further object of the invention to provide a novel blade design that minimizes airflow separation, maximizes downward air movement, and achieves significantly better performance than a traditional fan blade design.
According to further aspects of the present invention, adaptations of the novel blade may prove applicable in other areas, such as: aircraft propeller design, helicopter rotor design, drone propeller design, wind turbine design, computer cooling fans, and any other application wherein airflow is induced by a rotating blade.
Referring now to the diagram in
In general, the structural design of the novel blade 10 design includes a primary airfoil 20 having a root 22 for connecting to a rotating hub 50, a tip 24 opposite the root 22, a leading edge 26, and a trailing edge 24. The primary airfoil 20 can have an angle of incidence relative to the plane of rotation of the blade of between about 3° and 25° and preferably between about 4° and 12°.
The novel blade 10 design includes a secondary airfoil 30 generally parallel to the primary airfoil 20 having a root 32 generally proximate the root 22 of the primary airfoil 20, a tip 34 opposite the root 32 and generally proximate the tip 22 or the primary airfoil 20, a leading edge 36, and a trailing edge 38, wherein the secondary airfoil 30 is disposed below and connected proximate the trailing edge 28 of the primary airfoil 20. The secondary airfoil 30 can have an angle of incidence relative to the plane of rotation of the blade of between about 5° and 40° and preferably between about 15° and 30°.
The novel blade 10 design further includes a plurality of vertical supports 40 connecting the primary airfoil 20 to the secondary airfoil 40. The vertical supports 40 are connected to the bottom of the primary airfoil 20 at the top 42 of the support 40 and connected to the top of the secondary airfoil 30 at the bottom 44 of the support 40.
Either, or both, of the primary airfoil 20 and secondary airfoil 30 can include a twist to provide a reduced angle of incidence towards the tip 24 or root 22, as desired. In general, the effective angle of incidence of the leading edges 26, 36 decrease moving from the roots 22, 32 to the tips 24, 34. The inclination of the blade 10 matches the descending movement of air close to the roots 22, 32. Move towards the tips 24, 34, however, the tangential speed of the blade 10 outgrows the speed of descending air and requires the angle of incidence to decrease. This is a direct consequence of the blade tangential speed increasing with radius while the vertical movement of air remains comparatively constant.
The novel blade 10 design can include curvatures in either, or both, of the primary airfoil 20 or secondary airfoil 30 to increase the camber of the respective airfoils 20, 30.
The novel blade 10 can rigidly affixed to a rotating hub 50 wherein there is no variation in pitch of the overall structure of the blade 10 or it may be rotatably affixed to a rotating hub (not shown) wherein its pitch may be variable and controlled by a pitch controller (not shown), such as, for example a prop governor or a constant speed unit.
This design minimizes airflow separation, increases downward air movement, and achieves significantly better performance than a traditional fan flat blade design at a similar angle of incidence. While the novel blade planform 10 illustrated herein is generally rectangular in shape, it may be tapered or modified to almost any shape.
The novel blade 10 can be used in a fan wherein it functions by accelerating the air flow beneath the fan using a multi-element airfoil consisting of a primary airfoil 20 with camber and a lower offset secondary airfoil 30.
The novel blade 10 can use a twisted blade geometry that minimizes airflow separation and reduces drag along the span of the blade. It increases air flow more effectively resulting in a greater cubic foot per minute (CFM) rate at a smaller angle of incidence and achieves significantly better performance than a traditional fan blade design.
The novel blade 10 generates significantly higher axial speeds. The increased angle of incidence of the secondary airfoil 30 and the open area between the primary airfoil 20 and secondary airfoil 30 allows for higher velocities and therefore greater pressure differential to be created and this will direct more air down in spite of its lower angle of incidence. The downdraft is faster and thicker as compared to the baseline fan blade design (not shown).
In addition to generating a faster and thicker down draft, the novel blade 10 generates more turbulence.
Following are examples illustrating procedures for practicing the invention. These examples should be construed to include obvious variations and not limiting.
The intent of the novel fan blade is to generate greater volume of air movement at a reduced angle of incidence as compared with conventional fan blades which generally have fixed incidence angles between 10 and 15 degrees. Both 2-dimensional and 3-dimensional analyses were conducted for a 52″ fan size at standard operating conditions of 160 RPM. Based on the results, the novel fan blade design was found to have a 31% increase in air flow at 48″ below the plane of the fan, which is an Industry standard for measuring efficiency. More importantly, this significant improvement was obtained at an average incidence angle of approximately 7-degrees, which is almost half the 13-degrees in conventional fans.
Table 1, below, shows the increase in volume of air movement of the novel fan blade (NFB) design disclosed herein as compared to a baseline fan blade (not shown).
Referring now to
Referring finally to
In as much as the preceding disclosure presents the best mode devised by the invention for practicing the invention and is intended to enable one skilled in the pertinent art to carry it out, it is apparent that methods incorporating modifications and variations will be obvious to those skilled in the art. As such, it should not be construed to be limited thereby but should include such aforementioned obvious variations and be limited only by the spirit and scope of the following claims.
