CN101608640B

CN101608640B - Fan blades and modifications

Info

Publication number: CN101608640B
Application number: CN2009101505341A
Authority: CN
Inventors: R·M·安斯利
Original assignee: Delta T LLC
Current assignee: Delta T LLC
Priority date: 2004-07-21
Filing date: 2005-01-28
Publication date: 2012-02-08
Anticipated expiration: 2025-01-28
Also published as: AU2005278207B2; WO2006022812A1; JP4987147B2; NO20070961L; KR20130036381A; CN101099028B; AU2005278207A1; RU2008144966A; NZ553003A; SG139757A1; RU2007106444A; JP2011236914A; NZ578817A; RU2353817C2; KR20130008635A; MX2007000821A; AU2010214764A1; CN101099028A; CA2574762A1; KR101297469B1

Abstract

A winglet includes a vertical member and a mounting member. The mounting member is configured to facilitate the mounting of the winglet to the tip of a fan blade. The vertical member is configured to extend perpendicularly relative the tip of a fan blade. Adding winglets to fan blades may improve the aerodynamics of the fan blades, and thereby increase efficiencies of a fan.

Description

Fan blade and variants

The application is a divisional application of patent applications with international application date of 28.1.2005, international application number of PCT/US2005/002703 and Chinese national application number of 200580030869. X.

Technical Field

The applicant claims priority from united states provisional Patent Application Serial No. 60/589945 (u.s. Patent Application Serial No.60/589,945) entitled fan blades and variants (FanBlades and Modifications) published on 21.7.2004.

Background

The present invention relates generally to blades and blade variations, and more particularly to airfoils suitable for use with blades and winglets suitable for use with blades.

People working in large buildings, such as warehouses and manufacturing facilities, may be exposed to uncomfortable to dangerous working conditions. The same may also occur in agricultural locations, such as in buildings that are full of livestock. On hot days, the temperature in buildings can reach a level where humans or other animals are not kept healthy, or where the body temperature is undesirable. In areas where the temperature is uncomfortable or unsafe, a means to create or enhance airflow within the area is desirable. Such a gas flow may locally contribute to reducing the temperature in this area.

In addition, certain activities performed in these environments, such as welding or operating internal combustion engines, can produce airborne contaminants that can harm exposed personnel. If the flow of air is less than ideal in this region, the effects of airborne contaminants may be amplified. In these or similar situations, a means of creating or enhancing airflow within the area is desired. Such gas flow may locally be beneficial in reducing the harmful effects of the contaminants, for example by diluting and/or removing the contaminants.

In certain buildings and environments, a problem that can arise is that heat collects and remains near the ceiling of the building. This may be associated with a cooler area near the floor of the building. Those hazards that may occur in the event of this or other unbalanced air/temperature distribution will be immediately apparent to the ordinarily skilled artisan. In these and similar situations, a means of creating or enhancing airflow within the area is desired. Such airflow may be locally beneficial in eliminating temperature stratification and in inducing a more desirable air/temperature distribution.

It is also desirable to have a fan that can reduce power consumption. This reduction in power consumption may be effected by the fan operating efficiently (i.e., the energy required to operate the fan is less than the other fans). Reduced energy consumption may also be achieved as the fan improves air distribution, thereby reducing heating or cooling costs associated with other devices.

Drawings

The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention; it is to be understood, however, that the invention is not limited to the precise arrangements shown. Like reference symbols in the various drawings indicate like elements throughout the several views. In these drawings:

FIG. 1 is a plan view of a hub for mounting fan blades;

FIG. 2 is a cross-sectional view of an exemplary blade airfoil;

FIG. 3 is a cross-sectional view of an alternative exemplary blade airfoil;

FIG. 4 depicts a graph showing two ellipses;

FIG. 5 depicts a portion of the graph shown in FIG. 4;

FIG. 6 is a side view of an exemplary winglet blade variation;

FIG. 7 is a cross-sectional view of the winglet shown in FIG. 6;

FIG. 8 is a top view of the winglet shown in FIG. 6;

FIG. 9 is an end view of the fan blade of FIG. 2 modified from the winglet of FIG. 6;

FIG. 10 is an exploded perspective view of the winglet-fan blade assembly shown in FIG. 9.

Reference will now be made in detail to the preferred embodiments of the present invention, an example of which is illustrated in the accompanying drawings.

Detailed Description

Referring now to the details of the drawings in which like reference numerals refer to like parts throughout the several views, FIG. 1 shows an exemplary fan hub 10 that may be used to configure a fan having fan blades 30 or 50. In this example, fan hub 10 includes a plurality of hub mounting members 12 on which fan blades 30 or 50 may be mounted. In one embodiment, fan hub 10 is coupled to a drive mechanism that rotates fan hub 10 at a selectable or predetermined speed. A suitable hub assembly may thus comprise the hub 10 and a drive mechanism connected to the hub 10. Of course, the hub assembly may include a variety of other components, including different hubs, and the hub 10 may be driven by any suitable means. Further, hub 10 may have any suitable number of hub mounting members 12.

As shown in fig. 1-3, each hub mounting member 12 has a top surface 14 and a bottom surface 16 that terminate in a leading edge 18 and a trailing edge 20. In addition, each hub mounting member 12 includes an opening 22 formed in the top surface 14 and through the bottom surface 16. In this example, the opening 22 is sized to receive the fastener 26. Each hub mounting member 12 is configured to receive a fan blade 30 or 50. One of ordinary skill will appreciate that the hub mounting member 12 may be provided in a variety of alternative shapes.

In one embodiment, fan blades 30 or 50 are mounted on a hub assembly as disclosed in U.S. patent No. 6244821 (U.S. patent No.6,244,821). Of course, fan blades 30 or 50 may be mounted on any other hub and/or hub assembly. A suitable hub assembly can be operated to rotate hub 10 at any suitable angular velocity. By way of example only, such angular velocity may be any velocity in the range of about 7 to 108 revolutions per minute.

FIG. 2 shows a cross-sectional view of an exemplary fan blade 30 having a curved trailing edge 38, which is mounted to hub 10. The cross-sectional view is taken along a cross-sectional plane located at the center of fan blade 30, facing hub 10. Fan blade 30 has a top surface 32 and a bottom surface 34, each of which terminates in a leading edge 36 and a trailing edge 38. As shown, the trailing edge 38 has a slope that is approximately 45 relative to the portion of the top surface 32 near the trailing edge 38 and the portion of the bottom surface 34 near the trailing edge 38. Of course, the trailing edge 38 may have any other slope, by way of example only, and may be 0 ° to the extent that it comprises a single flat surface. Other suitable shapes for the trailing edge 38 will be apparent to those of ordinary skill.

In this example, fan blades 30 are substantially hollow. A plurality of flanges or bosses 40 are located inside the fan blades 30. As shown, when hub mounting member 12 is inserted into fan blades 30, flanges or bosses 40 are positioned such that they contact top surface 14, bottom surface 16, leading edge 18, and trailing edge 20 of hub mounting member 12. Thus, the boss 40 forms a snug fit between the fan blades 30 and the hub mounting member 12. Alternative shapes for fan blades 30 will be apparent to those of ordinary skill in the art and include, but are not limited to, those that affect the relationship between fan blades (30) and hub mounting member (12).

As used herein, terms such as "chord" (chord), "wing length" (chord), "maximum thickness" (maximum camber), "angle of attack" (angle of attack), and the like are intended to have the same meaning as terms used in the art of aircraft wings or other wing designs. In one embodiment, fan blades (30) have a wing length of about 6.44 inches. The maximum thickness of the blade (30) is 16.2% of the chord and the maximum camber is about 12.7% of the chord. The radius of the leading edge (36) is about 3.9% of the chord. The trailing edge (38) of the quadrant of the bottom surface (34) has a radius of about 6.8% of the chord. In an alternative embodiment, fan blade (30) has a chord of about 7 inches. In another alternative embodiment, the chord of blade (30) is approximately 6.6875 inches. Of course, any other suitable dimensions and/or proportions may be used.

By way of example only, the lift-to-drag ratio of fan blade (30) may range from about 39.8 at a Reynolds Number of about 120000 to about 93.3 at a Reynolds Number of about 250000. Of course, other lift-to-drag ratios may be achieved with the fan blade (30).

In one embodiment, the drag coefficient of fan blade (30) ranges from about 0.027 at a Reynolds number of about 75000 to about 0.127 at a Reynolds number of about 112500. Of course, other drag coefficients may be obtained for the fan blade (30).

In one embodiment, the fan blade (30) moves air at a Reynolds number of about 200000, such that the velocity ratio at the bottom surface (34) of the trailing edge (38) of the fan blade (30) is about 1.6. Other speed ratios may also be achieved for the fan blades (30).

In one embodiment, fan blades (30) provide non-retarded aerodynamics for angles of attack of about-1 ° to 7 ° at a Reynolds number of about 112000; and provides such aerodynamics for an angle of attack of about-2 to 10 at a reynolds number of about 250000. Of course, these values are merely examples.

FIG. 3 shows a cross-sectional view of another exemplary fan blade (50) having a generally oval top surface (52) and bottom surface (54), each of which terminates at a leading edge (56) and a trailing edge (58), the fan blade being mounted on the hub (10). The cross-sectional view is taken along a cross-sectional plane located at the center of the fan blade (50), facing the hub (10). In this example, the fan blade (50) is hollow. The plurality of protrusions (60) are located on the back side of the fan blade (50). As shown, when the hub mounting member (12) is inserted into the fan blades (50), the projections (60) are positioned such that they contact the top surface (14), bottom surface (16), leading edge (18), and trailing edge (20) of the hub mounting member (12). Thus, the boss (60) forms a snug fit between the fan blade (50) and the hub mounting member (12). Alternative shapes for fan blades (50) will be apparent to those of ordinary skill in the art and include, but are not limited to, shapes that have an effect on the relationship between fan blades (50) and hub mounting member (12).

As shown, fan blade (50) has a lower radius of curvature towards its leading edge (56) than a higher radius of curvature towards its trailing edge (58). The fan blade (50) can at least partially acquire curvature by generating two ellipses using the following formula. As will be appreciated by those of ordinary skill, the first ellipse on the x-axis and y-axis, with its origin at the Cartesian intersection, can be generated by the following equation:

[ 1 ] x ═ a (cos (t)); and

〔2〕y＝b(sin(t))

wherein,

a is the length of the major radius;

b is the length of the minor radius; and

t is the angle of the radius rotation around the origin (i.e., radians).

Accordingly, the first ellipse may be generated using the above equation. Similarly, equations [ 1 ] and [ 2 ] can be used to obtain a set of coordinates for the first ellipse. An exemplary first ellipse (200) is depicted in the graph of fig. 4, where a-3 and b-2.

The coordinates of the second ellipse can be obtained using the following equation:

〔3〕x₂x (cos (θ)) -y (sin (θ)); and

〔4〕y₂＝y(cos(θ))-x(sin(θ))

wherein,

x₂the coordinates of a second "x" after the first ellipse has been rotated counterclockwise around the origin by theta radians; and

y₂after the first ellipse has been rotated counterclockwise around the origin by theta radians, the coordinates of the second "y".

Thus, the size of the second ellipse is dependent on the size of the first ellipse. An exemplary second ellipse (300) is depicted in the graph of fig. 4, where θ is 0.525 radians. It will be appreciated that the first and second ellipses are labeled according to equations [ 1 ] to [ 4 ], and that the two ellipses may intersect at 4 points ("intersection of ellipses"). Fig. 4 shows 4 intersections (400) between the first ellipse (200) and the second ellipse (300).

The curvature of the top surface (52) and the bottom surface (54) may be based, at least in part, on the curvature of the first and second ellipses between the intersection points of two successive ellipses. An example of a segment of such a first ellipse (200) and second ellipse (300) is shown in fig. 5, which depicts the portions of the ellipses (200 and 300) between successive ellipse intersections (400). Accordingly, equations [ 1 ] through [ 4 ] may be used to generate surface coordinates for at least a portion of the top surface (52) and the bottom surface (54) of the fan blade (50).

It will be appreciated that the ratio of wing length to thickness of the fan blade (50) may vary with the amount of rotation theta relative to the two ellipses.

Of course, various portions of the fan blade (50) may deviate from the curvature of the first and second ellipses. By way of example only, and as shown in fig. 3, the leading edge (56) may be modified to have a generally circular curvature. Other deviations will be apparent to the ordinarily skilled artisan.

In one embodiment, fan blade (50) is formed using equations [ 1 ] to [ 4 ] such that a is 3 units, b is 2 units, and θ is 0.525 radians. In this embodiment, the fan blade (50) is provided with an annular leading edge (56) having a diameter of 3.5% of the blade length. The curvature of the leading edge (56) matches the curvature of the top surface (52) and the bottom surface (54) tangentially. This fit is envisioned by comparing fig. 3 with fig. 5. Of course, other dimensions may be used.

In one embodiment, fan blade (50) has a wing length of about 7.67 inches. In another embodiment, the blades have a wing length of about 7.687 inches. Of course, fan blades (50) may be of any other suitable blade length.

In this example, the radius of the leading edge (56) is about 3.5% of the chord. The maximum thickness of the blade (50) is about 14.2% of the chord. The maximum camber of the blade (50) is about 15.6% of the chord. Of course, any other suitable dimensions and/or proportions may be used.

In one example, a fan having a diameter of 24 feet and comprising 10 fan blades (50) mounted at a 10 ° angle of attack, when rotated at a rate of about 7 revolutions per minute (rpm), produces a thrust of about 5.2 pounds with a replacement rate of about 87302 cubic feet per minute (cfm). When the fan is rotating at a rate of about 14 rpm, the fan generates about 10.52 pounds of thrust with a displacement rate of about 124174 cubic feet per minute. When the fan was rotated at a rate of about 42 revolutions per minute, a thrust of about 71.01 pounds was generated, with a displacement rate of about 322613 cubic feet. Other thrusts and/or displacements may be obtained with a fan having blades (50).

By way of example only, a lift-to-drag ratio range for fan blade (50) having an angle of attack of about 10 may be expressed from about 39 at a Reynolds number of about 120000 to about 60 at a Reynolds number of about 250000. Other lift-to-drag ratios may also be obtained for fan blade (50).

In one embodiment, fan blades (50) provide non-retarded aerodynamics for angles of attack between about 1 ° and 11 ° with a reynolds number of about 112000, between about 0 ° and 13 ° with a reynolds number of about 200000, and between about 1 ° and 13 ° with a reynolds number of about 250000. Of course, these values are merely examples.

In one embodiment, a 14 foot diameter fan includes 10 fan blades (50) rotating at a rate of about 25 revolutions per minute. The fan was operated at about 54 watts of power, a torque of about 78.80 inches/pound, and a flow rate of about 34169 cubic feet/minute. The fan efficiency is then about 632.76 cfm/watt.

In another example, a 14 foot diameter fan includes 10 fan blades (50) rotating at a rate of about 37.5 revolutions per minute. The fan was operated at about 82 watts of power, a torque of about 187.53 inches/pound, and a flow rate of about 62421 cubic feet/minute. The fan efficiency is then about 761.23 cfm/watt.

In yet another example, a 14 foot diameter fan includes 10 fan blades (50) rotating at a rate of about 50 revolutions per minute. The fan was operated at about 263 watts of power, a torque of about 376.59 inches/pound, and a flow rate of about 96816 cubic feet/minute. The fan efficiency is then about 368.12 cfm/watt.

The following description may apply to any fan, including, by way of example only, fan (30) or fan (50).

In one embodiment, each fan blade (30 or 50) comprises a homogenous continuous material. By way of example only, the fan blades (30 and 50) may be constructed from extruded aluminum. However, it is to be appreciated that fan blades (30 and/or 50) may be constructed from any other suitable material including, but not limited to, any metal and/or plastic. Further, it is to be appreciated that fan blades (30 and/or 50) may be made by any suitable manufacturing method including, but not limited to, stamping, twisting, welding, and/or molding. Other suitable materials and methods of manufacture will be apparent to those of ordinary skill.

When fan blades (30 or 50) are mounted on hub (10), hub mounting member (12) may extend approximately 6 inches into fan blades (30 or 50), by way of example only. Alternatively, hub mounting member (12) may extend any suitable length into fan blades (30 or 50). It is also understood that the hub (10) may have the mounting member (12) mounted outside of the fan blades (30 or 50) rather than inside. Alternatively, the mounting member (12) may be mounted where the fan blade (30 or 50) is partially outside and partially inside.

The fan blade (30 or 50) may also include one or more openings configured to align with the openings (22) on the hub mounting member (12). In this embodiment, when the openings in the fan blades (30 or 50) are aligned with the openings (22) in the hub mounting member (12), fasteners (26) may be inserted through each opening to secure the fan blades (30 or 50) to the hub mounting member (12). In one embodiment, the fastener (26) is a bolt. Other suitable alternatives for the fastener (26) will be apparent to those of ordinary skill in the art, including, but not limited to, adhesives. Accordingly, it is to be understood that the openings (22) may be selected at will.

The fan blade (30 or 50) may be about 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14 feet long. Alternatively, fan blades (30 or 50) may be any other suitable length. In one embodiment, fan blades (30 or 50) and hub (10) are sized such that the fan diameter including fan blades (30 or 50) and hub (10) is about 24 feet. In another embodiment, fan blades (30 or 50) and hub (10) are sized such that the fan diameter including fan blades (30 or 50) and hub (10) is about 14 feet. Other suitable dimensions will be apparent to the skilled person.

It is to be understood that all cross-sectional views drawn along the length of fan blade (30 or 50) need not be identical. In other words, the shape of the fan blade (30 or 50) need not be uniform along the entire length of the fan blade (30 or 50). By way of example only, a portion of the "hub mounting end" of fan blade (30 or 50), i.e., the end of fan blade (30 or 50) that is to be mounted on hub (10), may be removed. In one example, the leading edge (56) of the fan blade (50) is chamfered to receive another fan blade (50) on the hub (10).

Alternatively, fan blades (30 or 50) may be formed or configured to omit, remove, or "lose" one or the other of the hub mounting ends. It will be appreciated that the absence of such a portion (whether it is removed or not removed at all from the outset) may eliminate some of the problems associated with the fan blades (30 or 50) at the hub (10) interfering with each other. This interference may be due to a variety of factors, including but not limited to the wing length of the fan blades (30 or 50). Of course, other factors besides interference may also affect the removal or other absence of a portion of fan blade (30 or 50). The missing portion may include a portion of the leading edge (36 or 56), a portion of the trailing edge (38 or 58), or both.

Optionally, to address the interference of fan blades (30 or 50) at the hub (10), the hub diameter may be increased (e.g., without increasing the number of hub mounting members (12)). Alternatively, the chord of the fan blade (30 or 50) may be reduced. Alternative arrangements and modifications of the hub (10) and fan blades (30 or 50) will be apparent to those of ordinary skill.

One of ordinary skill in the art will appreciate that the angle of attack of fan blades (30 or 50) may be zero or non-zero. By way of example only, when the fan blades (30 or 50) are mounted on the hub mounting member (12), the angle of attack of the fan blades may be in the range of about-1 ° to 7 °, between-2 ° to 10 °, or about 7 °,8 °, 10 °, or, for example, about 13 °. Of course, the angle of attack of the fan blades (30 or 50) may be any other suitable angle. The fan blades (30 or 50) are substantially straight along their length and their angle of attack is provided by a desired angle of attack carried by the hub mounting member (12).

Alternatively, the angle of attack of the hub mounting member (12) may be zero and the angle of attack of the fan blades (30 or 50) may be provided by twisting of the fan blades (30 or 50). In other words, fan blades (30 or 50) may be substantially straight along the length of hub mounting member (12) extending in fan blades (30 or 50), and twisting may be provided to provide an angle of attack to the remainder of fan blades (30 or 50). Such twisting may occur over any suitable length of blade (30 or 50) (e.g., twisting the entire remaining length of blade (30 or 50; or twisting may be brief so that all remaining portions of blade (30 or 50) are substantially straight, etc.). Moreover, other suitable shapes and methods of providing an angle of attack for the fan blades (30), in whole or in part, will be apparent to those of ordinary skill. Further, it is understood that all or any portion of fan blades (30 or 50) may have one or more twists for any purpose.

One of ordinary skill in the art will appreciate that the fan blades (e.g., 30 or 50) may be modified in a number of ways. Such variations may change the characteristics of the fan performance. As shown by way of example in fig. 6-10, one such variation may include a winglet (70). Although winglet (70) is discussed in the context of fan blades (30 and 50), it will be appreciated that winglet (70) may be used with any other suitable fan blade.

The winglet (70) in this example comprises an upstanding member (72). The upstanding member (72) is comprised of a flat inner surface (74) and a rounded outer surface (76). Other suitable shapes for the inner surface (74) and the outer surface (76) will be apparent to those of ordinary skill. In this example, the perimeter of the upright member (72) is defined by a lower edge (78), an upper edge (80), and a rear edge (82). Each edge (78, 80, and 82) meets at a corresponding corner (84). Thus, in this example, the upright member (72) has three corners (84). As shown, each corner (84) is rounded. Accordingly, the term "corner" as that term is used in this description should not be read as requiring an acute angle. In other words, a corner need not be limited to a point or region where a pair of straight lines meet or intersect. Although the upright member (72) is described in this example as having three corners, it is to be understood that the upright member (72) may have any suitable number of corners (84).

Other variations of the upright member (72) will be apparent to those of ordinary skill.

The winglet (70) in this example further comprises a winglet mounting member (90) extending substantially perpendicular to the inner surface (74) of the upstanding member (72). As shown, the winglet mounting member (90) is configured similarly to the hub mounting member (12). The winglet mounting member (90) has a top surface (92) and a bottom surface (94), each terminating in a leading edge (96) and a trailing edge (98). Further, each winglet mounting member (90) includes an opening (100) through the top surface (92) and the bottom surface (94). In this example, each opening (100) is sized to receive a fastener (26). A winglet mounting member (90) is configured to be inserted into one end of a fan blade (30 or 50). One of ordinary skill will appreciate that the winglet mounting member (90) may be provided in a variety of alternative shapes.

FIG. 9 shows a cross-sectional view of a fan blade (30) with a winglet (70) installed. The cross-sectional view is taken along a cross-sectional plane located at the center of the fan blade (30), facing the winglet (70) (i.e. facing away from the hub (10)). As shown in fig. 9 and 10, in this example the winglet mounting member (90) is arranged to fit within the tip of a fan blade (30 or 50). Like the hub mounting member (12), the winglet mounting member (90) is a snug fit against the boss (40 or 60) of the fan blade (30 or 50). In this example, the upper edge (80) of the winglet (70) extends above the top surface (32 or 52) of the fan blade (30 or 50) and also extends beyond the leading edge (36 or 56). Similarly, the lower edge (78) of the winglet (70) extends below the bottom surface (34 or 54) of the fan blade (30 or 50). The trailing edge (82) of the winglet (70) extends below the trailing edge (38 or 58) of the fan blade (30 or 50). Of course, winglet (70) and fan blade (30 or 50) may have any other relevant size and/or shape.

The fan blade (30 or 50) may have one or more openings formed near the tip of the fan blade (30 or 50) through the top surface (32 or 52) and/or the bottom surface (34 or 54) that align with the winglet opening (100) when the winglet mounting member (90) is inserted into the fan blade (30 or 50), and the fan blade opening is sized to receive the fastener (26). Thus, one or more fasteners (26) may be used to secure winglet (70) to fan blade (30 or 50). In one embodiment, the fastener (26) is a bolt. In another embodiment, the fastener (26) is comprised of a pair of complementary pointed interlocking clamping screws, such as threaded studs (e.g., a "male" screw threaded on the outer surface to mate with a "female" screw threaded on the inner surface) that are occasionally used to clamp a large number of papers together. However, any other suitable fastener may be used, including but not limited to an adhesive. Accordingly, it is to be understood that the opening (100) may be selected at will.

It will also be appreciated that it is not necessary to insert the winglet mounting member (90) into the end of a fan blade (30 or 50). In other words, and similar to the case of the hub mounting member (12), the winglet mounting member (90) may be arranged to fit on the outside of the fan blade (30 or 50) rather than on the inside. Alternatively, the winglet mounting member (90) may be fitted where the fan blade (30 or 50) is partly inboard and partly outboard. Other configurations will be apparent to those of ordinary skill.

In an alternative embodiment, the winglet (70) lacks a mounting member (90) and instead has a recess formed in the inner surface (74) of the upstanding member (72). In this embodiment, the tip of a fan blade (30 or 50) is inserted into the winglet (70) to attach the winglet (70) to the fan blade (30 or 50). In yet another embodiment, the fan blade (30 or 50) is formed integrally with the winglet (70). Accordingly, it will be appreciated by those of ordinary skill that a variety of configurations exist for providing a fan blade (30 or 50) with a winglet (70).

Although the upright member (72) is shown as being substantially perpendicular to the mounting member (90), it will be appreciated that the two members may be at any suitable angle relative to each other. Thus, and by way of example only, the upstanding member (72) may be inclined inwardly or outwardly when the winglet (70) is attached to a fan blade (30 or 50). Optionally, the upright member (72) may include more than one angle. In other words, the upright member (72) may be arranged such that the top portion of the upright member and the bottom portion of the upright member are each inclined inwardly when the winglet is attached to a fan blade (30 or 50). Other variations of winglet (70), including but not limited to angular variations, will be apparent to those of ordinary skill in the art.

Although the winglet (70) is described herein as a variation of the fan blade (30 or 50), it will be appreciated that any other fan blade may be modified with the winglet (70).

In one embodiment, winglet (70) is made from a homogenous continuously molded plastic. It is to be understood, however, that winglet (70) may be made from a variety of materials including, but not limited to, any suitable metal and/or plastic, and that it may be formed from multiple pieces. Furthermore, it will be appreciated that the winglet may be made by any suitable method of manufacture.

It will also be appreciated that the trailing edge vortices formed at or near the tips of the fan blades (30 or 50) may increase lift near the fan blades (30 or 50). The winglet (70) may inhibit radial airflow on the top surface (32 or 52) and/or the bottom surface (34 or 54) near the tip of the fan blade (30 or 50). This inhibition may force air to flow more normally from the leading edge (36 or 56) to the trailing edge (38 or 58), thereby increasing the efficiency of a fan having its blades (30 or 50) with winglets (70), at least at some rotational speed.

In one example, a winglet (70) is attached to the end of a blade (30 or 50) of a 6 foot diameter fan. Due to the addition of the winglet (70), the air flow rate of the fan is increased by 4.8% at a speed of 171 revolutions per minute.

In another example, a winglet (70) is attached to the end of a fan blade (30 or 50) of a 14 foot diameter fan. Due to the addition of the winglet (70), the air flow rate of the fan is increased by 4.4% at a speed of 75 rpm.

The following two tables show the efficiencies that can be obtained by adding winglets (70) to a 14 foot diameter fan:

table 1: fan without winglet (70)

Speed (rpm)	Maximum power (Tile)	Average power (Tile)	Torque (in/lb)	Flow rate (cubic feet per minute)	Efficiency (cubic feet/minute/tile)
						12.5	54	50	17.86	0	0
25	66	54	78.80	34169	632.76
						37.5	125	82	187.53	62421	761.23
50	339	263	376.59	96816	368.12
						62.5	700	660	564.01	110784	167.85
75	1170	1140	839.75	129983	114.02

Table 2: fan with winglet (70)

Speed (rpm)	Maximum power (Tile)	Average power (Tile)	Torque (in/lb)	Flow rate (cubic feet per minute)	Efficiency (cubic feet/minute/tile)
						12.5	50	42	18.56	26815	638.45
25	58	43	18.39	46547	1082.49
						37.5	68	49	186.00	61661	1258.39
50	241	198	354.61	87552	442.18
						62.5	591	528	582.78	120859	228.90
75	980	950	847.41	136560	143.75

Of course, other values may be achieved by using winglets (70). Further, suitable variations of winglets will be apparent to those of ordinary skill, including but not limited to alternative winglet shapes.

In summary, many of the benefits described are derived from applying the principles of the present invention. The foregoing description of one or more embodiments of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. One or more embodiments were chosen and described in order to best illustrate the principles of the invention and its application, to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. The appended claims define the scope of the invention.

Claims

1. A fan blade configured to be mounted on a rotating fan hub, the fan blade comprising:

(a) a top surface, a portion of the top surface having a substantially elliptical curvature, wherein at least a portion of the curvature of the top surface is based on a first ellipse;

(b) a bottom surface having a substantially elliptical curvature, wherein at least a portion of the curvature of the bottom surface is based on a second ellipse, wherein the second ellipse is formed based on the first ellipse;

(c) a leading edge, wherein the top surface and the bottom surface each terminate at the leading edge; and

(d) a trailing edge, wherein the top surface and the bottom surface each terminate at the trailing edge.

2. The fan blade of claim 1 wherein the fan blade is substantially hollow.

3. The fan blade of claim 2, wherein an inside of the fan blade includes one or more projections configured to engage the fan hub mounting member.

4. The fan blade of claim 1, wherein the fan blade is formed of an extruded material.

5. The fan blade of claim 4, wherein the extruded material comprises aluminum.

6. The fan blade of claim 1, wherein the first ellipse is generated based at least in part on the following equation:

x ═ a (cos (t)); and [ 1 ]

y＝b(sin(t))〔2〕

Wherein x and y provide x-y positions for the first ellipse,

a is the length of the major radius;

b is the length of the minor radius; and

t is the angle of the radius rotation around the origin.

7. A fan blade configured to be mounted on a rotating fan hub, the fan blade comprising:

wherein, when the first ellipse and the second ellipse are labeled on a common graph, the first ellipse and the second ellipse intersect at four intersection points, the substantially elliptical curvature of the top surface and the substantially elliptical curvature of the bottom surface being based on the curvature of the first ellipse and the second ellipse, respectively, in a region between a pair of adjacent intersection points.

8. A fan blade configured to be mounted on a rotating fan hub, the fan blade comprising:

(b) a bottom surface having a substantially elliptical curvature, wherein at least a portion of the curvature of the bottom surface is based on a second ellipse;

wherein the second ellipse is formed according to the first ellipse.