Abstract:
A centrifugal fan is described. The fan uses a blade that is tapered across the span of the blade. The taper can be larger towards the end opposite of the inlet or larger at the inlet. The blade may be backwardly inclined and/or curved. The fan may also include a turning vane.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The field of the disclosure relates generally to a centrifugal fan for an air moving application, and more specifically, to methods and apparatus for uniform airflow distribution within an air moving system comprised of a centrifugal fan and possibly housing assembly. 
         [0002]    Fans and centrifugal fan in particular are used widely for a variety of an air moving application. The air typically is preferred to move in a particular manner. Among terms used to describe air flow is the term flow distribution. Flow distribution describes the uniformity of the flow at the exit of the fan or assembly. Flow quality describes the level of disturbance in the flow such as turbulence, vortices, eddies, or other unfavorable flow structures. 
         [0003]    Typically a centrifugal fan has a blade section that is constant across the span of the blade. 
         [0004]    Fans and centrifugal fan in particular are used widely for an air moving application. Such applications include those for heating, ventilation and air conditioning, commonly known as HVAC as well as any others including chillers for commercial buildings. Blowers used in furnaces in HVAC commonly used centrifugal fans. For use in such applications and for all fan applications uneven air flow distribution and air flow quality issues are a plaguing problem. Such uneven air flow distribution and air flow quality may negatively affect the efficiency of a fan. Further uneven air flow distribution and flow quality issues may result in excessive noise and vibration as well as reduced service life. 
         [0005]    The present invention is directed to alleviate at least one of these problems. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    In one embodiment, a centrifugal fan is described. The fan uses a blade that is tapered across the span of the blade. The taper can be larger towards the end opposite of the inlet or larger at the inlet. 
         [0007]    In an aspect of this embodiment, a turning vane may be added that would separate the volumes of air as it enters into the blades therefore improving the efficiency and flow distribution from the fan. 
         [0008]    In another embodiment, a fan is described. The fan includes a plurality of blades. At least one of the blades has a length along a direction parallel to the axis of fan rotation. The at least one of the blades has a width transverse to its length. The width of the at least one of the blades is progressive increasing in width in a direction parallel to the axis of fan rotation and in the direction opposed to air flow. 
         [0009]    In an aspect of this embodiment, an element is placed in the internal air flow passage of the fan. The element may be a turning vane. The turning vane may include a smoothly-rounded entry nose and a thin extended trailing edge. The turning vane may be circular ring internally mounted to tine internal periphery of the blades. Further, multiple turning vanes may be used across the fan. Such multiple turning vanes may each be identical to each other in a particular far or some or all may be different from some each other in a particular fan. 
         [0010]    In an aspect of this embodiment, at least one of the fan blades is a backward inclined fan blade. A backward inclined fan blade is a type of centrifugal fan blade in which the blades is inclined such that its ends are pointing in the opposite direction to the rotation of the fan wheel. The fan blade is adapted to provide a non-overloading characteristic. 
         [0011]    In an aspect of this embodiment, the fan is adapted to provide improved fan efficiency. 
         [0012]    In another an aspect of this embodiment, the fan is adapted to provide improved flow quality providing reduced flow driven sound. 
         [0013]    In another an aspect of this embodiment, the fan is adapted to provide improved inertial and dynamic balance. 
         [0014]    In another an aspect of this embodiment, the fan is adapted to provide improved flow distribution. 
         [0015]    In another an aspect of this embodiment, the fan is adapted to provide reduction of active material. 
         [0016]    In another embodiment, a fan is described. The fan includes a plurality of blades. At least one of the blades has a length along a direction parallel to the axis of fan rotation. The at least one of the blades has a width transverse to its length. The width of the at least one of the blades is progressive decreasing in width in a direction parallel to the axis of fan rotation and in the direction of air flow. 
         [0017]    In an aspect of this embodiment, at least one of the fan blades is a backward inclined fan blade. A backward inclined fan blade is a type of centrifugal fan blade in which the blades is inclined such that its ends are pointing in the opposite direction to the rotation of the fan wheel. The fan blade is adapted to provide a non-overloading characteristic. 
         [0018]    In an aspect of this embodiment, the fan is adapted to provide improved fan efficiency. 
         [0019]    In another an aspect of this embodiment, the fan is adapted to provide improved flow quality providing reduced flow driven sound. 
         [0020]    In another an aspect of this embodiment, the fan is adapted to provide improved inertial and dynamic balance. 
         [0021]    In another an aspect of this embodiment, the fan is adapted to provide improved flow distribution. 
         [0022]    In another an aspect of this embodiment, the fan is adapted to provide reduction of active material. 
         [0023]    In another embodiment, a fan is described. The fan includes a plurality of blades. At least one of the blades is a turning vane. The turning vane is one of a single or multiple turning vane the turning vane has x, y and z. 
         [0024]    In another an aspect of this embodiment, the fan is adapted to provide improved fan efficiency. 
         [0025]    In another an aspect of this embodiment, the fan is adapted to provide improved flow quality providing reduced flow driven sound. 
         [0026]    In another an aspect of this embodiment, the fan is adapted to provide improved flow distribution. 
         [0027]    In another an aspect of this embodiment, the fan is adapted to provide improved blade assembly stiffness. 
         [0028]    In another embodiment, a fan is described. The fan includes a plurality of blades. At least one of the blades has a length along a direction parallel to the axis of fan rotation. The at least one of the blades has a width transverse to its length. The width of the at least one of the blades is progressive increasing in width in a direction parallel to the axis of fan rotation. The fan may also include a turning vane and may include multiple turning vanes. 
         [0029]    In another an aspect of this embodiment, the fan is adapted to provide improved fan efficiency. 
         [0030]    In another an aspect of this embodiment, the fan is adapted to provide improved flow quality providing reduced flow driven sound. 
         [0031]    In another an aspect of this embodiment, the fan is adapted to provide improved flow distribution. 
         [0032]    In another an aspect of this embodiment, the fan is adapted to provide improved blade assembly stiffness. 
         [0033]    In another an aspect of this embodiment, the fan is adapted to provide reduction of active material. 
         [0034]    In another an aspect of this embodiment, the fan is adapted to provide improved inertial and dynamic balance. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]      FIG. 1  is a perspective view of the one embodiment of a fan according to the present invention including tapered blades and a turning vane; 
           [0036]      FIG. 2  is a perspective view of the another embodiment of a fan according to the present invention including tapered blades; 
           [0037]      FIG. 3  is a plan view of one embodiment of a tapered fan blade according to the present invention; 
           [0038]      FIG. 4  is a plan view of the another embodiment of a tapered fan blade according to the present invention; 
           [0039]      FIG. 5  is a perspective view of one embodiment of a turning vane according to the present invention; and 
           [0040]      FIG. 6  is a cross sectional view of the turning vane of  FIG. 5  along the line  6 - 6  in the direction of the arrows. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0041]    Referring first to  FIG. 1 , an embodiment of the invention is shown as a centrifugal fan  10 . The fan  10  has a plurality of tapered blades  12 . The fan  10  rotates about axis of rotation  13 . The blades  12  may as shown be oriented such that the blades  12  are inclined such that their first and second ends  14  and  15 , respectively, are pointing in the direction of the rotation  16  of the fan  10 . This blade direction configuration is known as forwardly inclined blade configuration. It should be appreciated that the fan may be backwardly inclined or have a radial configuration. 
         [0042]    As shown the blades  12  are curved and defined by a radius R and a centerline  18 . It should be appreciated that the fan blades may be straight or may be curved in an orientation opposite that shown. It should be appreciated that the fan blades may have an arcuate shape more complex than a circular arc or may be bent. 
         [0043]    An element  20  may, as shown is placed in the internal air flow passage of the fan. Such an element may be generally known as a baffle. The element or baffle  20  may be a turning vane and will be described as such hereinafter. However, it should be appreciated that the baffle may be a flow straightener or separator or any device that baffles or turns the air flowing in or through a fan. It should be appreciated that any of the devices that may baffle or turn the air flowing in or through a fan including, but not limited to a flow straightener or separator may be positioned in a similar fashion and in similar locations to those described herein for turning vanes. 
         [0044]    The turning vane  20  may include a smoothly-rounded entry nose  22  and a thin extended trailing edge  24 . The turning vane  20  may be a circular ring internally mounted to the internal periphery  26  of the blades  12 . As shown the thin extended trailing edge  24  of the turning vane  20  intersects the blades  12 . The turning vanes may alternatively only touch and not intersect the blades. Further, the turning vanes may completely intersect the blades. Further, the turning vanes may be mounted through the blades and even completely intersect the blades. While, as shown, the turning vane  200  is mounted to the internal periphery  26  of the blades  12 , it should be appreciated that the turning vane may be mounted to the blades on the outer side of the blades. 
         [0045]    It should be appreciated that the fan with tapered blades of the present invention may be an axial or centrifugal or any other known fan. 
         [0046]    Referring now to  FIG. 2 , an embodiment of the invention is shown as a centrifugal fan  110 . The fan  110  has a plurality of tapered blades  112 . The fan  110  rotates about axis of rotation  113 . The blades  112  may as shown be oriented such that the blades  112  are inclined such that their ends  114  are pointing in the opposite direction to that of the rotation  116  of the fan  110 . This blade direction configuration is known as backwardly inclined blade configuration. It should be appreciated that the fan may be forwardly inclined or have a radial configuration. The blades  112  may, as shown, be generally planar and had an outer portion  128  and an inner portion  130  separated by a bend  132 . 
         [0047]    The fan  110  is an example of a backward inclined airfoil design fan with tapered blade section. 
         [0048]    Referring now to  FIG. 3 , an embodiment of the invention is shown as a centrifugal fan blade  212 . The fan blade  212  is typically one of a plurality of tapered blades  212 , only one of which is shown for use with a centrifugal fan (not shown). The blade  212  is as shown a single tapered blade  212 . The blade  212  as shown is preferably curved or arcuate in cross section, but may be planar or have any suitable shape or cross section. The blade  212  is defined by a first end  234  and a parallel spaced apart second end  236 . The ends  234  and  236  are connected by first and second sides  238  and  240  respectively. The sides  238  and  240  diverge from first end  234  to second end  236  and as show form blade angle Θ from centerline  242  of the blade  212 . It should be appreciated that the blade angle Θ may be different on each of the sides  238  and  240 . The blade  212  as shown may be used on a forward inclined fan design. It should be appreciated that the fan blade  212  may be used on a backwardly inclined fan design or a radial design. 
         [0049]    Referring now to  FIG. 4 , an embodiment of the invention is shown as a centrifugal fan blade  312 . The fan blade  312  is typically one of a plurality of tapered blades  212 , only one of which is shown for use with a centrifugal fan (not shown). The blade  312  is as shown a single tapered blade  312 . The blade  312  is preferably curved or arcuate in cross section, but may be planar or have any suitable shape or cross section. The blade  212  is defined by a first end  334  and a parallel spaced apart second end  336 . The ends  334  and  336  are connected by first and second sides  338  and  340  respectively. The second side  340  diverges from first side  338  from first end  334  to second end  336  and as show forms blade angle ΘΘ from first side  338  of the blade  312 . The blade  312  as shown may be used on a forward inclined fan design. It should be appreciated that the fan blade  312  may be used on a backwardly inclined fan design or a radial design. 
         [0050]    Referring now to  FIGS. 5 and 6 , an embodiment of the invention is shown as a centrifugal fan  410 . The fan  410  rotates about axis of rotation  413 . The fan  410  as shown includes a turning vane  420 . The turning vane  420  may, as shown, include a smoothly-rounded entry nose  422  and a thin extended trailing edge  424 . The turning vane  420  may be a circular ring internally mounted to the internal periphery of the blades. It should be appreciated that the turning vane may be mounted to the blades on the outer side of the blades. As shown the rounded entry nose  422  is curved and defined by a radius RR and a centerline  418 . 
         [0051]    It should be appreciated that multiple turning vanes (not shown) may be used across the span of the centrifugal fan. These turning vanes may extend to various depths inside of the fan inlet volume. The curvature of the turning vane is intended to capture incoming flow and separate the volume of air to improve the distribution of the airflow exiting the fan. 
         [0052]    The improved distribution across the blades provided by the use of a fan with tapered blades, whether forwardly inclined, backwardly inclined, radial, curved or planar, and whether including a turning vane or not, improves the efficiency of the fan and the reduction in flow disturbance downstream improves the overall sound quality of the system. Sound quality is improved by reduction of flow driven noise and instabilities by evening out the flow distribution through the housing. 
         [0053]    It should be appreciated that the features of the various embodiments may be combined in any possible way to provide the advantages of the present invention. Further, for example, each of the blade sections between the added turning vanes may have various tapered sections. 
         [0054]    The blade, turning vanes and other fan components as well as the fan may be made by any available manufacturing process and may be made of any suitable durable materials, including but not limited to metals, polymers and composites.