Title:
High efficiency fan blades with airflow-directing baffle elements
Kind Code:
A1


Abstract:
Fan blades are provided that increase aerodynamic and operational efficiency, and which include baffle elements positioned on the distal ends of the fan blades. The baffle elements operate by shearing blade tip vortices, thereby minimizing turbulent fluid effects, and further providing fluid shunt that imparts a radial velocity component to the fluid. The baffle elements produce a more focused and collimated fluid flow perpendicular to the plane of rotation during forward rotation, and produce a more diffuse, radially-outward directed fluid flow during reverse rotation. The baffle elements are positioned such that they are characterized by a first angle with respect to the radial axis of the fan blade and a second angle with respect to the low pressure surface of the fan blade.



Inventors:
Walls, Gary C. (Clymer, PA, US)
Application Number:
11/786816
Publication Date:
10/16/2008
Filing Date:
04/13/2007
Primary Class:
International Classes:
F01D5/14
View Patent Images:
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Primary Examiner:
EDGAR, RICHARD A
Attorney, Agent or Firm:
K&L GATES LLP-Pittsburgh (210 SIXTH AVENUE, PITTSBURGH, PA, 15222-2613, US)
Claims:
What is claimed is:

1. A fan blade comprising: a blade body including a leading edge, a trailing edge, a proximal end, a distal end, a high pressure surface, a low pressure surface, and a radial axis; and at least one baffle element positioned on the blade body at a first angle with respect to the radial axis and at a second angle with respect to the low pressure surface.

2. The fan blade of claim 1, further comprising a plurality of baffle elements positioned on the blade body at a first angle with respect to the radial axis and at a second angle with respect to the low pressure surface.

3. The fan blade of claim 1, wherein the at least one baffle element is positioned on the distal end.

4. The fan blade of claim 1, wherein the first angle with respect to the radial axis is in the range of approximately 30-degrees to approximately 60-degrees.

5. The fan blade of claim 1, wherein the first angle with respect to the radial axis is approximately 45-degrees.

6. The fan blade of claim 1, wherein the at least one baffle element extends from the low pressure surface.

7. The fan blade of claim 1, wherein the second angle with respect to the low pressure surface is approximately 90-degrees.

8. The fan blade of claim 1, wherein the at least one baffle element extends from both the low pressure surface and the high pressure surface.

9. The fan blade of claim 8, wherein the second angle with respect to the low pressure surface is approximately 90-degrees, and a third angle between the baffle element and the high pressure surface is approximately 90-degrees.

10. The fan blade of claim 1, wherein the at least one baffle element extends from the high pressure surface.

11. The fan blade of claim 1, wherein the second angle with respect to the low pressure surface is approximately 270-degrees.

12. The fan blade of claim 1, wherein the at least one baffle element is configured to be removably attached to the blade body.

13. The fan blade of claim 1, wherein the blade is utilized in an assembly comprising a plurality of fan blades.

14. A fan blade comprising: a blade body including a leading edge, a trailing edge, a proximal end, a distal end, a high pressure surface, a low pressure surface, and a radial axis; and at least one baffle element positioned on the distal end of the blade body at a first angle of approximately 45-degrees with respect to the radial axis and extending from the low pressure surface at a second angle of approximately 90-degrees with respect to the low pressure surface.

15. A fan blade comprising: a blade body including a leading edge, a trailing edge, a proximal end, a distal end, a high pressure surface, a low pressure surface, and a radial axis; and a plurality of baffle elements each positioned on the blade body at a first angle with respect to the radial axis and at a second angle with respect to the low pressure surface.

16. An fan comprising: a hub; a plurality of blades, each blade comprising a leading edge, a trailing edge, a proximal end, a distal end, a high pressure surface, a low pressure surface, and a radial axis, and each blade attached to the hub at the proximal end and positioned such that the distal end projects in a substantially radial direction away from the hub along the radial axis; and a plurality of baffle elements attached to the plurality of blades and positioned at a first angle with respect to the radial axis and at a second angle with respect to the low pressure surface.

17. The fan of claim 16, wherein the baffle elements are positioned on the distal ends of the fan blades.

18. The fan of claim 16, wherein the baffle elements are attached to the low pressure surfaces of the blades.

19. The fan of claim 16, wherein the first angle with respect to the radial axis is approximately 45-degrees and the second angle with respect to the low pressure surface is approximately 90-degrees.

20. A baffle element configured to be retrofit to a fan blade, the fan blade comprising a leading edge, a trailing edge, a proximal end, a distal end, a high pressure surface, a low pressure surface, and a radial axis, wherein the baffle element is configured to be positioned on the fan blade at a first angle with respect to the radial axis and at a second angle with respect to the low pressure surface.

Description:

TECHNICAL FIELD

The present invention relates generally to fan blades and, more particularly, to fan blades with airflow-directing baffle elements disposed thereon.

BACKGROUND OF THE INVENTION

The purpose of a fan is to move fluid continuously against moderate pressures. As used herein, the term fluid is intended to indicate material in a liquid, gaseous or vapor state. Accordingly, fan operation is highly dependent upon the total static pressure generated to overcome ambient fluid pressures and create fluid flow. An operating fan produces a pressure rise across the unit because the rotating fan blades function as aerofoils.

A moving aerofoil is essentially a flat plate inclined at an angle and moving through air or other fluids. The aerofoil experiences a force exerted thereon, which is resolvable to a component parallel to the direction of motion (drag) and a component perpendicular to the direction of motion (lift). In a fan, the rotating fan blades experience drag in the direction opposite that of rotation, and experience lift perpendicular to the plane of rotation. The lift forces produced on the high pressure surface of the aerofoil fan blade generate a discharge pressure that results in volume flow of fluid from the surface.

The performance of a fan in terms of pressure, volume flow, fluid velocity, power, and efficiency depends on a number of factors, the most critical of which are:

(a) the design and type of fan;
(b) the size of the fan;
(c) the speed of rotation of the fan impeller;
(d) the condition of the fluid passing through the fan; and
(e) the geometry of the fan blades comprising the impeller.
Consequently, it is a goal of fan design to develop fan blade geometries that optimize operating characteristics and performance.

There are four common types of fans: centrifugal fans, cross-flow fans, propeller fans, and axial-flow fans. As used herein, the term “impeller” or “fan impeller” is intended to indicate a rotating set of blades designed to impart motion to a mass of fluid. Centrifugal, or radial-flow, fans include an impeller running in a casing having a spirally shaped contour. The fluid enters the impeller in an axial direction and is discharged at the periphery, with the impeller rotation being toward the casing outlet. The amount of work done on the fluid, evident in the pressure development of the fan, depends primarily on the angle of the fan blades with respect to the direction of rotation at the periphery of the impeller. Three main forms of blades are commonly: (1) backward bladed, in which the blade tips incline away from the direction of rotation; (2) radial bladed, where the blade tips are radially disposed; and (3) forward curved, where the blade tips incline toward the direction of rotation.

Most centrifugal fan impellers have shrouded blades as part of a fan wheel. The shrouds include annular plates that are fitted at each end of the blades, giving mechanical strength to the fan impeller and reducing leakage between blades and casing. Fluid leakage around fan impeller blades and between blades and fan casings substantially reduce fan efficiency, requiring more power for a given total fan pressure or volume flow.

Cross-flow, or tangential, fans have impellers with blades shaped like forward-curved centrifugal fan impellers. However, both ends of the impeller in a cross-flow fan are sealed and it is fitted into a casing in which fluid enters at the periphery on one side, passes through the impeller, and leaves from the periphery at the other side. The axes of the inlet and outlet are roughly perpendicular; therefore, the flow through a cross-flow fan is curved rather than diametral. Cross-flow fan blades are generally of rectangular shape and considerable length, disposed in a parallel longitudinal orientation, forming a cylindrical impeller comprised of blades that allow for the curved fluid flow path through the impeller unit.

Propeller fans are comprised of a motor driven sheet metal impeller, positioned in an orifice with relatively large clearance. Fluid flow through a propeller fan is analogous to flow through an orifice rather than strict linear/axial flow. Propeller fans and axial flow fans are generally analogous in terms of structure and the fluid mechanics of operation, and are equivalent for most applications.

Axial flow fans are those where the flow of the fluid is substantially parallel to the axis of the impeller hub. Axial flow fans can be placed in three primary categories: (1) fluid circulator, or free fan; (2) diaphragm-mounted fan; or (3) ducted fan. A free fan is one that rotates in a common unrestricted fluid space, for example, desk, wall, pedestal, and ceiling fans. Diaphragm-mounted fans transfer fluid from one relatively large space to another, as for example an exhaust or ventilation fan that drives fluid from a factory or warehouse to the external atmosphere, or alternatively, drives outside fluid into an open internal area or transfers fluid between inside areas. Diaphragm-mounted fans do not use ductwork or fine-clearance cylindrical casings. Ducted fans constrain fluid flow in an axial direction with an enclosing shroud or duct. The minimum duct length required to satisfy the ducted condition must be in excess of the axial distance between inlet to, and outlet from, the impeller blades.

Generally, fluid approaches the fan impeller on the low pressure inlet side in an axial direction and leaves from the high pressure outlet side with an axial and rotational component due to work done by the impeller torque. Since the purpose of a fan is to move fluids against ambient pressures, the rotational velocity component is disadvantageous because it reduces the available total pressure generated by a fan to produce volume flow in an axial direction.

Notwithstanding the numerous fan designs developed to maximize fan efficiency while minimizing noise, vibration, and cost, a number of problems still exist in fan design for which adequate solutions have yet to be developed. For example, like centrifugal fans, axial flow and propeller-type fans suffer from fluid leakage around the fan impeller blade tips, and between blade tips and fan casings, which substantially reduces fan efficiency, requiring higher rotational impeller speeds and more power to produce a given total fan pressure or volume flow. This problem is characterized in that the fluid passing through the fan reverses direction at the blade tips, flows around the blade tips from the outlet surface to the inlet surface in a countercurrent fashion, and lowers efficiency as fluid discharged from the high pressure side bleeds back to the low pressure side creating vortices, stall conditions, and other turbulent flow characteristics, and further increasing undesirable noise and vibration.

An additional problem with conventional fan blades, for example, circular arc, flat undersurface, elliptical, and planar blades, is the rotational velocity component imparted to the fluid due to the torque of the fan blades. This component can decrease fan efficiency by decreasing the amount of available total static pressure on the discharge side, and as a result, decreasing the total volume flow for a given impeller speed and configuration. While conventional methods exist to reduce this problem, for example, upstream or downstream guide vanes and contra-rotating assemblies, these methods possess attendant problems of their own, including, for example, increased noise and power requirements.

Moreover, conventional fan blades are not capable of redirecting the rotational velocity component to create a radial component, which in effect would push residual fluid flow (i.e. fluid flow that is not in an axial direction) in a radial direction and would form a more collimated and laminar volume flow from the fan unit.

An additional problem with conventional fan blades in axial flow and propeller-type fan systems is the clearance space on the low pressure suction/inlet side required to achieve acceptable operating performance. In particular, axial flow and propeller-type fans need sufficient clearance between the low pressure side of the blades and an adjacent surface, for example a solid and continuous wall or ceiling, in order to achieve efficient flow-through performance. If an impeller assembly is located too closely adjacent to a solid and continuous surface, turbulent flow characteristics such as stalls and vortices develop on the suction surface of the impeller blades. This poses a problem in areas of limited space, for example, in rooms with low ceilings or limited floor space, where it would be advantageous to achieve maximal fluid flow while minimizing the dead space behind the low pressure suction side of any fan units.

Accordingly, it would be desirable to provide a fan blade configuration that increases fan efficiency (increased total static fan pressure and volume flow at lower impeller speeds and lower power requirements), decreases noise and vibration, and creates a more focused and collimated volume flow.

BRIEF SUMMARY OF THE INVENTION

The present invention is generally directed toward improved fan blades which reduce, minimize, or eliminate countercurrent fluid bleeding, blade tip vortices, stalling effects, turbulent flow conditions, low pressure suction/inlet side clearance space, noise, vibration, and the rotational fluid velocity component, and further which increase the radial fluid velocity component and overall fan efficiency. Fluid-directing blade structures (described hereinafter as “baffles” or “baffle elements”) are disposed at the distal end (i.e., the tip end) of the fan blades provided herein. The baffle elements are positioned on the distal end of each fan blade, directed toward the low pressure suction/inlet side, the high pressure discharge/outlet side, or both, and further at a first specified angle with respect to the radial axis of the fan blade, a second specified angle with respect to the low pressure surface of the fan blade, and/or at a third specified angle with respect to the high pressure surface of the fan blade.

In one embodiment, the present invention is directed toward fan blades including a blade body having a leading edge, a trailing edge, a proximal end, a distal end, a high pressure surface, a low pressure surface, and a radial axis, and a baffle element, such that the baffle element is positioned on the distal end of the blade body at a first angle with respect to the radial axis, at a second angle with respect to the low pressure surface, and/or at a third angle with respect to the high pressure surface.

In another embodiment, the present invention is directed toward fan blades including a blade body having a leading edge, a trailing edge, a proximal end, a distal end, a high pressure surface, a low pressure surface, and a radial axis, and a baffle element, such that the baffle element is positioned on the distal end of the blade body and extending from the low pressure surface at an angle of approximately 45-degrees with respect to the radial axis, and at an angle of approximately 90-degrees with respect to the low pressure surface.

In yet another embodiment, the present invention is directed toward axial-flow fans including a drive mechanism, a hub rotatably coupled to the drive mechanism, a plurality of fan blades, and a baffle element attached to at least one of the high pressure surface, the low pressure surface, or both of at least one blade of the plurality of blades at the distal end of the blade, such that the blades are attached to the hub at the proximal ends, and positioned such that the distal ends project in a substantially radial direction away from the hub, and such that the baffle element is positioned on the distal end at a first angle with respect to the radial axis, at a second angle with respect to the low pressure surface, and/or at a third angle with respect to the high pressure surface of the blade.

Other features and advantages will be apparent from the following description, including the drawings, and from the claims set forth.

BRIEF DESCRIPTION OF THE DRAWINGS

The various described embodiments will hereinafter be described in conjunction with the appended drawings provided to illustrate and not limit the described embodiments, wherein like designations denote like elements, and in which:

FIG. 1 is a side view parallel to the plane of rotation of a conventional propeller or axial flow type fan illustrating fluid flow currents when operating in forward rotation;

FIG. 2 is a bottom or front view, orientation depending, of a conventional propeller or axial flow type fan illustrating peripheral tip vortices;

FIG. 3 is a side view parallel to the plane of rotation of a fan with baffle elements according to non-limiting embodiments of the present invention illustrating fluid flow currents when operating in forward rotation;

FIG. 4 is a bottom or front view, orientation depending, of a fan with baffle elements according to non-limiting embodiments of the present invention;

FIG. 5 is a side view parallel to the plane of rotation of a conventional propeller or axial flow type fan illustrating fluid flow currents when operating in reverse rotation;

FIG. 6 is a side view parallel to the plane of rotation of a fan with baffle elements according to non-limiting embodiments of the present invention when operating in reverse rotation;

FIG. 7 is view perpendicular to the plane of rotation of a fan blade according to non-limiting embodiments of the present invention;

FIG. 8 is a view perpendicular to the plane of rotation of an assembly of fan blades according to non-limiting embodiments of the present invention;

FIG. 9A is a side view parallel to the plane of rotation of an assembly of fan blades according to non-limiting embodiments of the present invention, FIG. 9B is a view perpendicular to the plane of rotation of the assembly depicted in FIG. 9A;

FIG. 10 is a side view parallel to the plane of rotation of a fan blade according to non-limiting embodiments of the present invention;

FIG. 11A is a partial view parallel to the plane of rotation of a baffle element according to non-limiting embodiments of the present invention, FIG. 11B is a partial view to the plane of rotation of a baffle element according to non-limiting embodiments of the present invention;

FIG. 12 is a view parallel to the plane of rotation of a baffle element according to non-limiting embodiments of the present invention;

FIGS. 13A, 13B, and 13C are views parallel to the plane of rotation of assemblies of fan blades according to non-limiting embodiments of the present invention;

FIG. 14A and FIG. 14B are views perpendicular to the plane of rotation of fan blades according to non-limiting embodiments of the present invention;

FIG. 15 is a view parallel to the plane of rotation of a baffle element according to non-limiting embodiments of the present invention;

FIG. 16A is a view parallel to the plane of rotation of a fan blade according to non-limiting embodiments of the present invention. FIG. 16B is a view perpendicular to the plane of rotation of the fan blade depicted in FIG. 16A;

FIG. 17A is a view parallel to the plane of rotation of a fan blade according to non-limiting embodiments of the present invention. FIG. 17B is a view perpendicular to the plane of rotation of the fan blade depicted in FIG. 17A;

FIG. 18 is a view perpendicular to the plane of rotation of a fan blade according to non-limiting embodiments of the present invention;

FIG. 19 is a view perpendicular to the plane of rotation of a fan blade according to non-limiting embodiments of the present invention;

FIG. 20 is a view perpendicular to the plane of rotation of a fan blade according to non-limiting embodiments of the present invention;

FIG. 21 is a view perpendicular to the plane of rotation of a fan blade according to non-limiting embodiments of the present invention;

FIG. 22 is a view perpendicular to the plane of rotation of a fan blade according to non-limiting embodiments of the present invention;

FIG. 23 is a view perpendicular to the plane of rotation of a fan blade according to non-limiting embodiments of the present invention;

FIG. 24 is a view perpendicular to the plane of rotation of a fan blade according to non-limiting embodiments of the present invention; and

FIG. 25 is a side view of an axial-flow fan according to non-limiting embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The described embodiments provide improved fan blades for reducing, minimizing, or eliminating countercurrent fluid bleeding, blade tip vortices, stalling effects, turbulent flow conditions, low pressure inlet/suction side clearance space, noise, vibration, and the rotational fluid velocity component, and further for increasing the radial fluid velocity component and overall fan efficiency.

Before various embodiments are explained in detail, it is to be understood that the described embodiments are not limited in application to the construction and arrangement of the structures, components, steps, and/or examples set forth in the following description or illustrated in the drawings. The described embodiments are capable of other forms and may be carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for purpose of description and should not be regarded as limiting.

As used herein, the term “forward rotation” is intended to indicate the direction of rotation of a fan impeller such that the discharge surface corresponds to the forward-facing side of the impeller. For example, in a ceiling fan application, the orientation of the pitch of the blades is such that forward rotation would produce fluid flow down into the space below the fan, while alternatively, reverse rotation would produce fluid flow up through the fan impeller and into the space above the fan. There is no convention in the art defining forward or reverse rotation as either clockwise or counterclockwise rotation. Designers of fans determine what direction of rotation is forward rotation by setting the orientation of the blade pitch on a fan impeller and setting which side of the impeller is the forward-facing side. The fan blades disclosed herein are capable of application regardless of the respective directions of rotation. However, for purposes of illustration, and not to be regarded as limiting, forward rotation corresponds to clockwise rotation and reverse rotation corresponds to counterclockwise rotation of the fan impellers illustrated in FIGS. 2, 4, 7, 8, 9B, 14A, 14B, 16B, 17B, 18, 19, 20, 21, and 22, which are front views of the forward-facing sides of the illustrated fan blades and fan impellers.

FIG. 1 illustrates a conventional fan blade assembly 10 in forward rotation, and the fluid flow currents associated therewith. During operation, the forwardly-rotating blades 20 generate lower pressure on the inlet/suction surface 22 and higher pressure on the outlet/discharge surface 23. The low pressure surface 22 induces influx of fluid into the rotating blades 20, while the high pressure surface 23 forces volume flow 25 from the blades. Due to the pressure gradient across the rotating blades 20, a portion of the volume flow from the high pressure surface 23 bleeds back, around the tips of the fan blades, to the low pressure surface 22, producing vortex currents 24.

The vortices 24 produced by the rotating blades 20 reduce the total static pressure generated by the fan, and therefore reduce the volume flow 25 for given operating conditions (i.e., given power input and blade rotational speed). The vortices 24 produced by the rotating blades 20 further disrupt the volume flow in the annular region formed by the circular path of the tip portion of blades 20, as illustrated in FIG. 2 rotating in the direction indicated by arrow 60. The disrupted fluid region includes vortices 24, which can induce the formation of stall conditions (not shown), which are large secondary rotational fluid flows along the length of the low pressure surface 22 of the fan blade 20. These turbulent fluid flow characteristics substantially reduce the efficiency of conventional fan blades.

As illustrated in FIG. 3, the baffle elements 150 according to various embodiments of the present invention increase fan blade efficiency by redirecting the fluid in the tip region of rotating blades 100. The redirection of the fluid by the baffle elements 150 locally increases the pressure on the low pressure surface 122 at the distal tip region 58 of the fan blade 100, thereby locally reducing the pressure gradient across the fan blade at the distal tip region 58 relative to the pressure gradient across the fan blade 100 proximally from the distal tip region 58. Baffle element 150 further provides a barrier to prevent the formation of vortices around the blade tip. As illustrated in FIG. 4, this reduces the fluid turbulence in the annular region 59 formed by the path of the tip portion of rotating blades 100. The reduction of vortices and other turbulent effects decreases the prevalence of stall conditions on the low pressure surface 122 of the rotating blades 100.

The baffle element 150 additionally shunts fluid in the direction indicated by arrow 57 in FIG. 4. The shunt imparts a radial velocity component to the fluid adjacent to the side of the rotating fan blades on which baffle element 150 is positioned. When the baffles 150 are positioned on the low pressure surface 122 of the fan blade, the radial velocity component directs fluid radially inward to the low pressure side of the rotating blade assembly, where it is worked upon by the blades 100 and discharged from the high pressure outlet surface 123. In this mode, the fan blade 100 with baffle element 150 has two propulsion areas: the high pressure outlet surface 123 and the surface of the baffle element 150. The radial shunt of the fluid due to the propulsion area of baffle element 150 partially offsets the efficiency losses due to the rotational component of the fluid discharged from the high pressure outlet surface 123 due to the torque of rotating fan blades 100. The combined vortex shearing and fluid-shunting due to the baffle elements 150 results in a more focused and collimated volume flow 125. Accordingly, the baffle elements 150 increase the available static fan pressure and volume flow for given operating conditions, and function as flow directing elements.

By way of example, and not intended as limiting, in fan applications where the fan can be operated in forward and reverse, the vortices that are produced by conventional fan blades are a substantial problem regardless of the direction of blade rotation. Various embodiments of the present invention provide baffle elements that function to increase fan efficiency and performance during operation in both forward and reverse directions.

FIG. 5 illustrates a conventional fan blade assembly 10 in reverse rotation, and the fluid flow currents associated therewith. During operation, the reversely-rotating blades 20 generate lower pressure on the bottom-facing surface and higher pressure on the top-facing surface. The low pressure surface 22 induces influx of fluid 30 from below into the rotating blades 20, while the high pressure surface 23 discharges volume flow from the blades 20. A portion of the volume flow from the high pressure surface 23 bleeds back, around the tips of the fan blades, to the low pressure surface 22 producing vortex currents 24 due to the pressure gradient across the rotating blades 20.

As illustrated in FIG. 6, the baffle elements 150 redirect the fluid in the distal tip region 58 reducing, minimizing, or eliminating the vortices and flow disruptions in the periphery of the impeller area as in the case with forward rotation. However, in reverse rotation, the baffle elements shunt fluid in an outward radial direction. In this mode, the baffle elements 150 redirect at least a portion of the velocity component in the discharge flow from high pressure surface 123 into an outwardly radial component 134.

The effect of the baffle elements 150, as illustrated in FIGS. 3 and 6 respectively, is that in forward rotation, the baffle elements 150 are positioned on the low pressure surface 122 and produce a more densely focused and collimated discharge volume flow 125 approximately perpendicular to the plane of the fan impeller, whereas in reverse rotation, the baffle elements 150 are positioned on the high pressure surface 123 and produce a more radially-distributed discharge volume flow 134 approximately parallel to the plane of the fan impeller.

FIG. 7 is a view perpendicular to the plane of rotation of a fan blade 100 according to non-limiting embodiments of the present invention. The blade 100 rotates in forward rotation in the direction indicated by arrow 60 and the view is of high pressure surface 123. Blade 100 is attached to hub 160 at the proximal end 140 of the blade. Blade 100 is comprised of blade body including distal end 130, leading edge 10, trailing edge 120, and radial axis A. Radial axis A designates a reference line originating at the center point of hub 160 and projecting in a radial direction, indicated as direction B in FIG. 7, through the body of blade 100. Positioned on the distal end 130 of blade 100 is baffle element 150. Baffle element 150 is positioned such that it forms an angle 170, indicated as θ, with respect to radial axis A of blade 100.

FIG. 8 is a view perpendicular to the plane of rotation of an assembly 105 of fan blades according to non-limiting embodiments of the present invention. The fan blades 100 rotate in forward rotation in the direction indicated by arrow 60. Each blade 100 is attached to hub 160 at the proximal end 140 of the blade. Each blade is further comprised of distal end 130, leading edge 110, trailing edge 120, radial axis A, and baffle elements 150 positioned on the distal ends 130 of the blades 100 forming angle 170 with respect to radial axis A. In this embodiment, leading edge 110, tailing edge 120 and radial axis A are substantially parallel. The blade and hub assembly 105 of FIG. 8 depicts four baffled fan blades attached to hub 160. It is understood that fan assemblies according to non-limiting embodiments of the present invention are not limited to any number of fan blades or baffled fan blades, and could include any number of baffled fan blades as part of an impeller or fan blade assembly suitable for the particular purposes and operating conditions of the fan.

FIG. 9A is a side view parallel to the plane of rotation of an assembly of fan blades according to non-limiting embodiments of the present invention. FIG. 9B is a view perpendicular to the plane of rotation of the assembly depicted in FIG. 9A. The baffle elements 150 are attached to fan blades 100 at their distal ends. The fan blades 100 are attached to hub 160 at their proximal ends. Leading edge 110 and trailing edge 120 are indicated in both FIGS. 9A and 9B.

FIG. 10 is a side view parallel to the plane of rotation and along the length of a fan blade 100 according to non-limiting embodiments of the present invention. The baffle element 150 is positioned on the distal end of the blade 100 extending from the low pressure surface 122. Baffle element 150 is positioned such that it forms an angle 200, indicated as φ, with respect to the low pressure surface 122.

The baffle element 150 is depicted extending from the low pressure surface 122 in FIGS. 10, 11A, 13A, and 15. However, the positioning of the baffle element 150 is not limited to extension from the low pressure surface 122 of the fan blade, and can be positioned to extend from the high pressure surface 123, as depicted in FIG. 11B, or from both the low pressure surface 122 and the high pressure surface 123, as depicted in FIG. 12. In embodiments where baffle element 150 is positioned such that it extends from both the low pressure surface 122 and the high pressure surface 123, the baffle element forms a third angle 250, indicated as λ in FIG. 12, with respect to the high pressure surface 123.

As used herein, the term “approximately” to describe angle values in degrees is interpreted to encompass the stated value ±10-degrees. Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of “1 to 10” is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10.

In embodiments where the baffle element 150 extends from the low pressure surface 122 of the fan blade, the angle 200 ranges from approximately 0-degrees to approximately 180-degrees, preferably from approximately 45-degrees to approximately 135-degrees, and is most preferably 90-degrees. See, for example, FIGS. 10, 11 and 15. In embodiments where the baffle element 150 extends from the high pressure surface 123, the angle 200 ranges from approximately 180-degrees to approximately 360-degrees, preferably from approximately 225-degrees to approximately 315-degrees, and most preferably is approximately 270-degrees. In embodiments where the baffle element 150 extends from both the low pressure surface 122 and the high pressure surface 123, the second angle 200 ranges from approximately 0-degrees to approximately 180-degrees, preferably from approximately 45-degrees to approximately 135-degrees, and most preferably is approximately 90-degrees; and the third angle 250 ranges from approximately 0-degrees to approximately 180-degrees, preferably from approximately 45-degrees to approximately 135-degrees, and most preferably is approximately 90-degrees. In embodiments where the baffle element 150 extends from both the low pressure surface 122 and the high pressure surface 123, the second angle 200 and the third angle 250 may be equal or different.

The first angle 170 formed between the baffle element 150 and the radial axis A of the fan blade can range from approximately 0-degrees to approximately 180-degrees, preferably from approximately 30-degrees to approximately 60-degrees, and most preferably is approximately 45-degrees.

FIGS. 13A, 13B, and 13C depict fan blade assemblies where the baffle elements 150 respectively extend from the low pressure surface 122, the high pressure surface 123, and both the low pressure surface 122 and the high pressure surface 123.

Baffle element 150 can be integrally formed as part of fan blade 100 as depicted in FIGS. 7 through 15. An integrally formed fan blade (i.e., a monolithic structure including the body of the blade and the baffle element), according to certain embodiments of the present invention, can be fabricated from any one of the numerous common solid component manufacturing methods well known to those of ordinary skill in the art, including, but not limited to, die casting, injection molding, sheet stamping, extrusion molding, and CNC machining. In addition to the baffle being integrally formed with the fan blade into a monolithic component, the baffle element 150 can be fabricated as a separate component 300, which is structured and configured to be fastened or attached, either permanently or removably, from the correspondingly structured and configured fan blade 375, as depicted in FIGS. 16A and 16B. The baffle element component 300 can be attached to the fan blade 375 at junction 350 by any means known to one of ordinary skill in the art, including, but not limited to, compression mechanisms, rivets, bolts, screws, other fasteners, adhesives, epoxies, and welds.

Baffle element 150 can further be manufactured as an appliance, attachment, or add-on component 400, which can be attached, permanently or removably, to a conventional fan blade 475. In this manner, a baffle element can be applied to a conventional fan blade as a retrofit. As illustrated in FIGS. 17A and 17B, the baffle appliance 400 is structured and configured to mate with and attach to conventional fan blade 475 at junction 450. The appliance 400 can be used to convert conventional fans into more efficient fans by utilizing the baffle element according to various embodiments of the present invention.

The baffle elements have been illustrated in the drawings and described herein as planar rectangular fin or winglet type structures 150. It is to be understood, however, that the baffle elements are not limited to rectangular or square shapes, but may be fabricated in any number of shapes including, but not limited to, rectangular, square, trapezoidal, rhomboidal, quadrilateral, triangular, elliptical, circular, semi-circular, pentagonal, hexagonal, heptagonal, and octagonal. Additionally, the baffle elements are not limited to planar structures, and may be fabricated in convex, concave, or other three-dimensional geometries. Moreover, the baffle elements 150 are not limited to the width of the fan blade, and may be structured and positioned such that they run shorter than (FIG. 18) or exceed (FIGS. 20 through 22) the leading edge 110 and/or the trailing edge 120 of any particular fan blade.

The baffle elements of the present invention have heretofore been described in conjunction with planar, rectilinear blades. However, the baffle elements of the present invention are applicable to any of the conventional types of fan blades, including, but not limited to, circular arc, flat undersurface, elliptical, and planar blades. The baffle elements are further applicable to propeller-type fan blades and any conventional axial-flow fan blade geometry. For example, and without limitation, FIGS. 18 through 21 depict a swept-blade configuration with a baffle element 150 positioned on the distal end 130 at an angle 170 with respect to radial axis A, and extending from the low pressure surface at a second angle of approximately 90-degrees. Dashed line 180 in FIGS. 18 and 20 depicts the outline of the edge of a conventional swept fan blade. In various embodiments of the present invention, the portions of the blade within line 180 and baffle element 150 may be configured analogously to a conventional fan blade, wherein the blade terminates at the distal end. In such embodiments, baffle element 150 extends from the low pressure surface, the high pressure surface, or both, intersecting the conventional swept blade proximal to the distal end. An embodiment where the baffle element intersects a rectilinear fan blade proximal to the distal edge is illustrated in FIG. 22.

In various embodiments of the present invention, the portions of the blade within line 180 and baffle element 150 are eliminated. In such embodiments, the fan blades terminate at the baffle element, which is directly positioned on the distal end as illustrated in FIGS. 19 and 21.

The fan blades have been illustrated and described herein as including at least one baffle element, wherein the baffle element is positioned on the distal end of the fan blade or is positioned at an intermediate location proximally with respect to the distal end. In various embodiments, the fan blades may include a plurality of baffle elements. For example, FIG. 23 illustrates a fan blade according to embodiments of the present invention wherein two baffle elements 150 and 151 are positioned on the blade body. The two baffle elements 150 and 151 are positioned on the blade body at first angles 170 and 171, respectively, with respect to radial axis A. The angles 170 and 171 may be of the same value or of different values. The baffle elements 150 and 151 may be of the same shape, size and configuration or of different shapes, sizes and configurations. The second angles (not shown) between the baffle elements 150 and 151 and the low pressure surface may be of the same value or of different values for each respective baffle element positioned on the blade body.

FIG. 23 depicts baffle element 150 positioned on the distal end 130 of the blade body and baffle element 151 positioned proximal from the distal end. Fan blades according to various embodiments are not limited to this configuration. For example, FIG. 24 depicts baffle elements 150 and 151, where both baffle elements are positioned proximal from the distal end 130.

The fan blades according to various embodiments of the present invention are not limited to any particular number of baffle elements, and can include any number of baffle elements suitable for the particular application of the fan blades. Moreover, regardless of the number of baffle elements per blade and their positioning on the blade body, the baffle elements may be manufactured as an appliance, attachment, or add-on component, which can be attached, permanently or removably, to a conventional fan blade. In this manner, baffle elements can be applied to a conventional fan blade as retrofits.

The baffle elements of the present invention can be incorporated into new fan designs, used as modifications to existing fan designs, or applied as retrofits of existing conventional propeller and/or axial-flow fans. The baffle elements are particularly suited for, but not limited to, use in axial-flow or propeller type fan units such as fluid circulator fans, free fans, diaphragm-mounted fans, propeller fans, and ducted fans.

Fan blades according to various embodiments of the present invention are applicable to common fan units including, but not limited to desk fans, wall fans, floor fans, window fans, pedestal fans, ceiling fans, box fans, ventilation fans, and industrial fans. For example, in ceiling fan applications, as illustrated in FIG. 3, baffle elements 150 reduce the amount of open space necessary between the ceiling and the rotating blades 100 in order to achieve optimal fluid volume flow-through 125, maximizing convectional cooling. Baffle elements 150 are also advantageous when a ceiling fan is operated in reverse rotation, as illustrated in FIG. 6, where baffle elements 150 produce a radial shunt 134 that efficiently distributes fluid throughout a room, rather than creating localized turbulent effects, for example vortices 34 in FIG. 5, common to conventional fan blades. This reduction in low pressure side space is particularly advantageous for rooms with low ceilings, where a conventional ceiling fan would be impractical.

An additional example of a non-limiting embodiment of the present invention would be a large-scale industrial or mobile box fan positioned with a vertical plane of rotation. Such fans conventionally require significant free space on the low pressure suction/inlet side in order to achieve optimal volume flow. The baffle elements according to non-limiting embodiments of the present invention allow such fans to develop optimal volume flow with reduced low pressure side free space at moderate rotational speeds, whereas conventional fans would require substantially higher fan speeds and increased power consumption to achieve comparable flow.

An exemplary fan unit 500 according to various embodiments of the present invention is illustrated in FIG. 23. Fan unit 500 includes a drive mechanism 510, for example a direct current (DC) or a pulse width modulated (PWM) motor; a hub 160 rotatably coupled to the drive mechanism 510; and a plurality of fan blades 100, at least one of which includes a baffle element 150. The methods in which the components are fabricated and assembled, and the incorporation of additional components into the unit, for example control means, support structures, and casings or housings, are the subject of design or engineering choice, the exercise of which does not take the fan unit outside the scope of the present invention.

Advantages of embodiments of the present invention additionally include noise reduction, because turbulent flow conditions that create noise are reduced, minimized, or eliminated; and the aerodynamic efficiency of the fan blades are increased because the baffle elements provide for radial fluid direction and shunting toward the low pressure inlet, providing for increased fluid volume flow and increased static total pressure for the same fan speed, size, and power requirements.

While the present invention has been described in terms of fans and fan blades, which traditionally operate in air environments, it is to be understood that the baffle elements according to various embodiments are applicable to other fluid handling equipment and fluid systems including, but not limited to, compressors and gas turbines, and liquid handling systems, for example propeller-type water conveying equipment.

It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the present invention, while eliminating, for purposes of clarity, other elements, such as, for example, details regarding specific hardware components generally associated with fan equipment. Those of ordinary skill in the art will recognize that the specific fan equipment of interest will dictate the type, configuration, and positioning of the fan unit and dimensioning of components. However, because the technical details and functionality of such elements are well known in the art and because they do not facilitate a better understanding of the present invention, a detailed discussion of such elements is not provided herein.

While several embodiments of the invention have been described, it should be apparent, however, that various modifications, alterations and adaptations to those embodiments may occur to persons skilled in the art with the attainment of some or all of the advantages of the disclosed invention. Therefore, this application is intended to cover all such modifications, alterations and adaptations without departing from the scope and spirit of the disclosed invention as defined by the appended claims.