Patent Publication Number: US-2012027597-A1

Title: Centrifugal fan

Description:
CROSS REFERENCES RELATED APPLICATIONS 
     The present application claims the benefits of priority to Korean Patent Application No. 10-2010-0072163 (filed on Jul. 27, 2010), which is herein incorporated by reference in its entirety. 
     THE BACKGROUND 
     1. The Field 
     The present invention relates to a centrifugal fan. 
     2. Description of the Related Art 
     A centrifugal fan suctions air in an axial direction and discharges the air in a radial direction. The centrifugal fan may be mounted on an evaporation chamber or a machine chamber of an air conditioner and a refrigerator. In particular, in the case of the refrigerator, an area of a cooled air passage is decreased in order to increase a volume in the refrigerator, such that a passage resistance is increased. In order to solve the problem, a centrifugal fan having a high constant pressure property is generally used. 
     However, a general centrifugal fan in the related art has disadvantages to be described below. 
     Specifically, while the axial-direction flow is switched to the radial-direction flow, air is discharged from a trailing edge of a fan blade at an angle between the axial direction and the radial direction. Therefore, a larger flow rate is generated from a lower side than an upper side of the trailing edge of the fan blade. 
     Accordingly, a large pressure difference between the upper side and the lower side of the trailing edge is caused, and as a result, some of the air discharged through the trailing edge flows backward through a bell mouth mounted on the top of the blade. Therefore, the flow is lost and noise increases and an eddy phenomenon occurs at the upper side of the trailing edge, such that fan efficiency deteriorates. 
     THE SUMMARY 
     The present invention has been made in an effort to solve the problems. 
     An exemplary embodiment of the present invention provides a centrifugal fan including: a hub penetrated by a rotational axis; a plurality of main blades extended in a radial direction from a predetermined point of the top of the hub; a bell mouth formed on a top of the exteriors of the plurality of main blades; and a plurality of auxiliary blades extended in the radial direction between the plurality of main blades, wherein a ratio (D 1 /D 2 ) of an inner diameter D 1  to an outer diameter D 1  of each of the auxiliary blades is in the range of 07 to 0.9. 
     The following effects can be achieved by the centrifugal fan according to the exemplary embodiment of the present invention configured as above. 
     First, a constant pressure and a flow rate of a fan are increased by installing an auxiliary blade between main blades. 
     Second, since the flow rate increases at the same rpm, rpm can decrease while the same flow rate is maintained, and as a result, noise is reduced. 
     Third, a velocity distribution of a flow discharged through a trailing edge of the auxiliary blade is substantially uniform, such that a pressure difference between an upper side and a lower side of the trailing edge is minimized, and as a result, a flow property in which the discharged air flows backward is improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a centrifugal fan according to an exemplary embodiment of the present invention. 
         FIG. 2  is a plan view of a centrifugal fan according to an exemplary embodiment of the present invention. 
         FIG. 3  is a bottom view of a centrifugal fan according to an exemplary embodiment of the present invention. 
         FIG. 4  is a side view of a centrifugal fan according to an exemplary embodiment of the present invention. 
         FIG. 5  is a graph showing a comparison of a flow rate for each rpm between a centrifugal fan according to an exemplary embodiment of the present invention and a general centrifugal fan with no auxiliary blade. 
         FIG. 6  is a graph showing a comparison of noise for each frequency between a centrifugal fan according to an exemplary embodiment of the present invention and a general centrifugal fan with no auxiliary blade. 
     
    
    
     THE DETAILED DESCRIPTION 
     In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific preferred embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is understood that other embodiments may be utilized and that logical structural, mechanical, electrical, and chemical changes may be made without departing from the spirit or scope of the invention. To avoid detail not necessary to enable those skilled in the art to practice the invention, the description may omit certain information known to those skilled in the art. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims. 
     Hereinafter, a centrifugal fan according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a perspective view of a centrifugal fan according to an exemplary embodiment of the present invention,  FIG. 2  is a plan view of a centrifugal fan according to an exemplary embodiment of the present invention, and  FIG. 3  is a bottom view of a centrifugal fan according to an exemplary embodiment of the present invention. 
     Referring to  FIGS. 1 to 3 , the centrifugal fan  10  according to the exemplary embodiment of the present invention includes a hub  11  penetrated by a rotational axis and having a circular cone shape in which a diameter increases toward the bottom, a blade extended with being rounded in a radial direction at an edge of the hub, and a bell mouth  14  formed on the top of the blade. 
     Specifically, the blade includes main blades  12  extended from the edge of the bottom of the hub and auxiliary blades  13  each of which the top is connected to the bottom of the bell mouth  14 . The auxiliary blade  13  is provided between the main blade  12  to improve flow loss caused by a difference in velocity and pressure between an upper side and a lower side of a trailing edge of the blade. 
     The hub  11  has the circular cone shape in which the diameter increases toward the bottom to serve to diffuse air suctioned in a rotational axial direction to a radial direction. In addition, the main blade  12  extends in the radial direction starting from a point spaced apart toward the center from the edge of the bottom of the hub  11  by a predetermined distance. In addition, the main blade  12  is extended with being rounded at a predetermined curvature. Further, the auxiliary blade  13  is shorter than the main blade  12  and does not contact the hub  11 . That is, the auxiliary blade  13  is connected to only the bell mouth  14 . 
     Moreover, an outer diameter of the bell mouth  14  is larger than that of the bottom of the hub  11 . In addition, the inner edge of the bell mouth  14  is rounded in an extending direction of the rotational axis of the hub  11 . In other words, the inner edge of the bell mouth  14  is extended by a predetermined length with being rounded toward the top of the hub  11 . 
     Meanwhile, in the structure of the main blade  12 , an end of the main blade at the side of the hub  11  may be defined as a leading edge  121  and an opposite end to the leading edge  121  may be defined as a trailing edge  122 . Of course, similarly, both ends of the auxiliary blade  13  may also be defined as a leading edge  131  and a trailing edge  132 . 
     Specifically, when the centrifugal fan  10  is viewed from the top ( FIG. 2 ), a diameter D 1  of a circumference linking the leading edges of the auxiliary blades  13  may be substantially equal to or larger than the diameter of the bottom of the hub  11 . In addition, the trailing edges  122  and  132  of the main blade  12  and the auxiliary blade  13  are positioned on the same circumference and may be substantially equal to the diameter D 2  of the bell mouth  14 . In other words, the diameter of the circumference passing the leading edges  131  of the auxiliary blades  13  may be represented by D 1  and the diameter of the circumference passing the trailing edges  132  may be represented by D 2 . 
     Further, the diameter D 1  of the circumference passing the leading edges  131  of the auxiliary blades  13  may be equal to or larger than an inner diameter of the bell mouth  14 . In addition, the auxiliary blade  13  may be interposed between one or two or more main blades  12 . Moreover, hereinafter, the diameter D 1  of the circumference passing the leading edges  131  of the auxiliary blade  13  is defined as an inner diameter of the auxiliary blade  13  and the diameter D 2  of the circumference passing the trailing edges  132  is defined as an outer diameter of the auxiliary blade  13 . 
     Meanwhile, the inner diameter D 1  of the auxiliary blade  13  may be larger than the diameter of the circumference linking the leading edges  121  of the main blade  12 , i.e., an inner diameter of the main blade  12 . 
     Further, a ratio (D 1 /D 2 ) of the inner diameter to the outer diameter of the auxiliary blade  13  is preferably in the range of 0.7 to 0.9 and this is a result extracted through tests performed at several times. 
       FIG. 4  is a side view of a centrifugal fan according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 4 , the auxiliary blade  13  is extended by a predetermined length toward the bottom of the hub  11  from the bottom of the bell mouth  14 . Herein, a length from an upper end to a lower end of the trailing edge  132  of the auxiliary blade  13  is defined as a width W 1  of the trailing edge  132  of the auxiliary blade  13 . In another aspect, the width W 1  may be the height of the trailing edge  132  from the bottom of the bell mouth  14 . 
     In addition, the main blade  12  is extended from a predetermined point of the top of the hub  11 . Further, a length from an upper end to a lower end of the trailing edge  122  of the main blade  12  is defined as a width W 2  of the trailing edge  122  of the auxiliary blade  12 . In another aspect, the width W 2  may be the height of the trailing edge  122  from the bottom of the bell mouth  14 . 
     Further, a ratio (W 1 /W 2 ) of the trailing edge  132  of the auxiliary blade  13  to the width of the trailing edge  122  of the main blade  12  is preferably in the range of 0.45 to 0.65 and this is also a result extracted through tests performed at several times. 
       FIG. 5  is a graph showing a comparison of a flow rate for each rpm between a centrifugal fan according to an exemplary embodiment of the present invention and a general centrifugal fan with no auxiliary blade. 
     Referring to  FIG. 5 , a flow rate generated by the centrifugal fan  10  according to the exemplary embodiment of the present invention is more than that of the general centrifugal fan in the same rpm. Accordingly, when the same flow rate is generated, since the rpm of the centrifugal fan  10  of the exemplary embodiment of the present invention may be set to be less than that of the general centrifugal fan, power consumption can be reduced. 
       FIG. 6  is a graph showing a comparison of noise for each frequency between a centrifugal fan according to an exemplary embodiment of the present invention and a general centrifugal fan with no auxiliary blade. 
     Referring to  FIG. 6 , a sound pressure level (SPL) generated in the centrifugal fan  10  according to the exemplary embodiment of the present invention is lower than that of the general centrifugal fan under the same frequency. 
     This means that the magnitude of noise generated in the centrifugal fan  10  is smaller than that of the general centrifugal fan at the same rpm or frequency. Accordingly, fan noise can be reduced by using the centrifugal fan  10  according to the exemplary embodiment of the present invention.