Patent Publication Number: US-11022140-B2

Title: Fan blade winglet

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from and the benefit of U.S. Provisional Application Ser. No. 62/726,878, entitled “FAN BLADE WINGLET”, filed Sep. 4, 2018, which is herein incorporated by reference in its entirety for all purposes. 
    
    
     BACKGROUND 
     This disclosure relates generally to heating, ventilation, and/or air conditioning (HVAC) systems. Specifically, the present disclosure relates to a fan blade winglet for a fan. 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present techniques, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as an admission of any kind. 
     A heating, ventilation, and/or air conditioning (HVAC) system may be used to thermally regulate an environment, such as a building, home, or other structure. The HVAC system generally includes a vapor compression system, which includes heat exchangers such as a condenser and an evaporator, which cooperate to transfer thermal energy between the HVAC system and the environment. In many cases, a fan, such as an axial fan, is configured to direct an air flow across a heat exchanger. For example, the fan typically includes a motor configured to rotate a fan hub about a central axis of the fan. A plurality of angled fan blades extend radially from the fan hub, such that rotation of the fan blades generates an air flow from an upstream end portion of the fan to a downstream end portion of the fan. Unfortunately, conventional fan blades may incur relatively significant aerodynamic drag during operation, which may increase a power consumption of the fan motor, and thus, reduce an operational efficiency of the HVAC system. 
     SUMMARY 
     The present disclosure relates to a flow generating device for a heating, ventilation, and/or air conditioning system. The flow generating device includes a housing having a channel defining a flow path of a fluid and a fan blade having a rotational axis extending through the channel, where the fan blade is configured to rotate to force the fluid along the flow path. A portion of the fan blade axially protrudes beyond the channel in a direction generally aligned with the flow path and a winglet extends from the portion of the fan blade. 
     The present disclosure also relates to a flow generating device for a heating, ventilation, and/or air conditioning system, where the flow generating device includes a housing having a channel defining a flow path of a fluid. The flow generating device also includes a plurality of fan blades disposed partially within the channel, where the plurality of fan blades is configured to rotate about an axis within the channel and direct the fluid along the flow path. The flow generating device further includes a winglet coupled to a portion of a fan blade of the plurality of fan blades, where the portion of the fan blade axially protrudes beyond the channel. 
     The present disclosure also relates to a flow generating device for a heating, ventilation, and/or air conditioning system, where the flow generating device includes a housing having a channel defining a flow path for a fluid flow. An end portion of the channel is configured to receive the fluid flow from an ambient environment. The flow generating device also includes a fan blade disposed partially within the channel and configured to rotate about an axis within the channel, where rotation of the fan blade facilitates the fluid flow through the channel from the ambient environment. A portion of the fan blade axially protrudes beyond the end portion of the channel and a winglet brackets the portion of the fan blade. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which: 
         FIG. 1  is a perspective view of an embodiment of a building that may utilize a heating, ventilation, and/or air conditioning (HVAC) system in a commercial setting, in accordance with an aspect of the present disclosure; 
         FIG. 2  is a perspective view of an embodiment of a packaged HVAC unit, in accordance with an aspect of the present disclosure; 
         FIG. 3  is a perspective view of an embodiment of a residential split HVAC system, in accordance with an aspect of the present disclosure; 
         FIG. 4  is a schematic diagram of an embodiment of a vapor compression system that may be used in the packaged HVAC unit of  FIG. 2  and the residential HVAC system of  FIG. 3 , in accordance with an aspect of the present disclosure; 
         FIG. 5  is a perspective view of an embodiment of a flow generating device that may be used in an HVAC system, in accordance with an aspect of the present disclosure; 
         FIG. 6  is a perspective view of an embodiment of a winglet that may couple to the flow generating device of  FIG. 5 , in accordance with an aspect of the present disclosure; 
         FIG. 7  is a plan view of an embodiment of the winglet coupled to a fan blade of the flow generating device of  FIG. 5 , in accordance with an aspect of the present disclosure; 
         FIG. 8  is a plan view of an embodiment of a fan assembly of the flow generating device of  FIG. 5 , in accordance with an aspect of the present disclosure; and 
         FIG. 9  is a perspective view of an embodiment of the flow generating device of  FIG. 5 , in accordance with an aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments of the present disclosure will be described below. These described embodiments are only examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     As mentioned above, a heating, ventilation, and/or air conditioning (HVAC) system may include one or more fans that are configured to direct a flow of air across certain components of the HVAC system, such as a condenser and/or an evaporator. Typical fans include an actuator, such as an electric motor, which is configured to rotate a central fan hub about a central axis of the fan. A plurality of fan blades extend radially from the fan hub, relative to the central axis, such that rotation of the fan hub drives rotation of the fan blades. The fan hub and the fan blades collectively form a fan assembly, which may be partially disposed within a channel, or a venturi, defined by a fan housing. Accordingly, a portion of the fan blades may protrude axially from the channel, which will be referred to herein as an exposed portion of the fan blades. The fan blades each include an angled blade member having a pressure surface, or a first surface, and a suction surface, or a second surface, which is disposed opposite the first surface. Rotation of the fan assembly enables the pressure surface of the fan blades to engage with ambient air surrounding the fan assembly to generate an air flow through the channel from an upstream end portion of the channel to a downstream end portion of the channel. In some embodiments, the fan may include an axial fan, which directs the air flow in a direction generally parallel to the central axis of the fan. The fan assembly may thus generate a pressure differential between the upstream and downstream end portions of the channel. Unfortunately, conventional fan blades may enable a backflow of air to occur around a radial edge of the fan blades and, in particular, around a radial edge of the exposed portion of the fan blades from a high pressure region near the pressure surface of the fan blades to a low pressure region near the suction surface of the fan blades. This backflow of air may generate vortices near the radial edges of the fan blades, which may increase a velocity of the air flow near the suction surface of the fan blades and, as such, decrease a pressure of the low pressure region near the suction surface. Accordingly, such vortices generate an induced drag on the fan blades during operation of the fan, which may increase a power consumption of the actuator, and thus, reduce an operational efficiency of the fan. Unfortunately, typical fan blades may be ill-equipped to block an undesirable backflow of air around respective radial edges of the fan blades. 
     It is presently recognized that it may be desirable to block the backflow of air around the radial edges of the fan blades during operation of the fan. Specifically, it may be desirable to block air flow from the high pressure region to the low pressure region to reduce induced drag on the fan blades, and thus, increase an efficiency of the fan. 
     With the foregoing in mind, embodiments of the present disclosure are directed toward a fan blade winglet that is configured to substantially block air flowing around the exposed portion of the fan blades from the pressure surface to the suction surface. As described in greater detail herein, the winglet may couple to a radial edge of a respective fan blade and extend generally outward from the pressure surface. A lower edge of the winglet mates with an angled profile or curvature of the fan blade, and thus, blocks air flow around the radial edge of the fan blade to reduce or substantially eliminate the generation of vortices near the radial edge. In some embodiments, the winglet mates with a portion of the radial edge corresponding to the exposed portion of the fan blades. A profile of the winglet may be selected based on a geometric shape of the fan blades, as well as a position of the fan blades relative to a housing of the fan. These and other features will be described below with reference to the drawings. 
     Turning now to the drawings,  FIG. 1  illustrates an embodiment of a heating, ventilation, and/or air conditioning (HVAC) system for environmental management that may employ one or more HVAC units. As used herein, an HVAC system includes any number of components configured to enable regulation of parameters related to climate characteristics, such as temperature, humidity, air flow, pressure, air quality, and so forth. For example, an “HVAC system” as used herein is defined as conventionally understood and as further described herein. Components or parts of an “HVAC system” may include, but are not limited to, all, some of, or individual parts such as a heat exchanger, a heater, an air flow control device, such as a fan, a sensor configured to detect a climate characteristic or operating parameter, a filter, a control device configured to regulate operation of an HVAC system component, a component configured to enable regulation of climate characteristics, or a combination thereof. An “HVAC system” is a system configured to provide such functions as heating, cooling, ventilation, dehumidification, pressurization, refrigeration, filtration, or any combination thereof. The embodiments described herein may be utilized in a variety of applications to control climate characteristics, such as residential, commercial, industrial, transportation, or other applications where climate control is desired. 
     In the illustrated embodiment, a building  10  is air conditioned by a system that includes an HVAC unit  12 . The building  10  may be a commercial structure or a residential structure. As shown, the HVAC unit  12  is disposed on the roof of the building  10 ; however, the HVAC unit  12  may be located in other equipment rooms or areas adjacent the building  10 . The HVAC unit  12  may be a single package unit containing other equipment, such as a blower, integrated air handler, and/or auxiliary heating unit. In other embodiments, the HVAC unit  12  may be part of a split HVAC system, such as the system shown in  FIG. 3 , which includes an outdoor HVAC unit  58  and an indoor HVAC unit  56 . 
     The HVAC unit  12  is an air cooled device that implements a refrigeration cycle to provide conditioned air to the building  10 . Specifically, the HVAC unit  12  may include one or more heat exchangers across which an air flow is passed to condition the air flow before the air flow is supplied to the building. In the illustrated embodiment, the HVAC unit  12  is a rooftop unit (RTU) that conditions a supply air stream, such as environmental air and/or a return air flow from the building  10 . After the HVAC unit  12  conditions the air, the air is supplied to the building  10  via ductwork  14  extending throughout the building  10  from the HVAC unit  12 . For example, the ductwork  14  may extend to various individual floors or other sections of the building  10 . In certain embodiments, the HVAC unit  12  may be a heat pump that provides both heating and cooling to the building with one refrigeration circuit configured to operate in different modes. In other embodiments, the HVAC unit  12  may include one or more refrigeration circuits for cooling an air stream and a furnace for heating the air stream. 
     A control device  16 , one type of which may be a thermostat, may be used to designate the temperature of the conditioned air. The control device  16  also may be used to control the flow of air through the ductwork  14 . For example, the control device  16  may be used to regulate operation of one or more components of the HVAC unit  12  or other components, such as dampers and fans, within the building  10  that may control flow of air through and/or from the ductwork  14 . In some embodiments, other devices may be included in the system, such as pressure and/or temperature transducers or switches that sense the temperatures and pressures of the supply air, return air, and so forth. Moreover, the control device  16  may include computer systems that are integrated with or separate from other building control or monitoring systems, and even systems that are remote from the building  10 . 
       FIG. 2  is a perspective view of an embodiment of the HVAC unit  12 . In the illustrated embodiment, the HVAC unit  12  is a single package unit that may include one or more independent refrigeration circuits and components that are tested, charged, wired, piped, and ready for installation. The HVAC unit  12  may provide a variety of heating and/or cooling functions, such as cooling only, heating only, cooling with electric heat, cooling with dehumidification, cooling with gas heat, or cooling with a heat pump. As described above, the HVAC unit  12  may directly cool and/or heat an air stream provided to the building  10  to condition a space in the building  10 . 
     As shown in the illustrated embodiment of  FIG. 2 , a cabinet  24  encloses the HVAC unit  12  and provides structural support and protection to the internal components from environmental and other contaminants. In some embodiments, the cabinet  24  may be constructed of galvanized steel and insulated with aluminum foil faced insulation. Rails  26  may be joined to the bottom perimeter of the cabinet  24  and provide a foundation for the HVAC unit  12 . In certain embodiments, the rails  26  may provide access for a forklift and/or overhead rigging to facilitate installation and/or removal of the HVAC unit  12 . In some embodiments, the rails  26  may fit into “curbs” on the roof to enable the HVAC unit  12  to provide air to the ductwork  14  from the bottom of the HVAC unit  12  while blocking elements such as rain from leaking into the building  10 . 
     The HVAC unit  12  includes heat exchangers  28  and  30  in fluid communication with one or more refrigeration circuits. Tubes within the heat exchangers  28  and  30  may circulate refrigerant through the heat exchangers  28  and  30 . For example, the refrigerant may be R-410A. The tubes may be of various types, such as multichannel tubes, conventional copper or aluminum tubing, and so forth. Together, the heat exchangers  28  and  30  may implement a thermal cycle in which the refrigerant undergoes phase changes and/or temperature changes as it flows through the heat exchangers  28  and  30  to produce heated and/or cooled air. For example, the heat exchanger  28  may function as a condenser where heat is released from the refrigerant to ambient air, and the heat exchanger  30  may function as an evaporator where the refrigerant absorbs heat to cool an air stream. In other embodiments, the HVAC unit  12  may operate in a heat pump mode where the roles of the heat exchangers  28  and  30  may be reversed. That is, the heat exchanger  28  may function as an evaporator and the heat exchanger  30  may function as a condenser. In further embodiments, the HVAC unit  12  may include a furnace for heating the air stream that is supplied to the building  10 . While the illustrated embodiment of  FIG. 2  shows the HVAC unit  12  having two of the heat exchangers  28  and  30 , in other embodiments, the HVAC unit  12  may include one heat exchanger or more than two heat exchangers. 
     The heat exchanger  30  is located within a compartment  31  that separates the heat exchanger  30  from the heat exchanger  28 . Fans  32  draw air from the environment through the heat exchanger  28 . Air may be heated and/or cooled as the air flows through the heat exchanger  28  before being released back to the environment surrounding the rooftop unit  12 . A blower assembly  34 , powered by a motor  36 , draws air through the heat exchanger  30  to heat or cool the air. The heated or cooled air may be directed to the building  10  by the ductwork  14 , which may be connected to the HVAC unit  12 . Before flowing through the heat exchanger  30 , the conditioned air flows through one or more filters  38  that may remove particulates and contaminants from the air. In certain embodiments, the filters  38  may be disposed on the air intake side of the heat exchanger  30  to prevent contaminants from contacting the heat exchanger  30 . 
     The HVAC unit  12  also may include other equipment for implementing the thermal cycle. Compressors  42  increase the pressure and temperature of the refrigerant before the refrigerant enters the heat exchanger  28 . The compressors  42  may be any suitable type of compressors, such as scroll compressors, rotary compressors, screw compressors, or reciprocating compressors. In some embodiments, the compressors  42  may include a pair of hermetic direct drive compressors arranged in a dual stage configuration  44 . However, in other embodiments, any number of the compressors  42  may be provided to achieve various stages of heating and/or cooling. As may be appreciated, additional equipment and devices may be included in the HVAC unit  12 , such as a solid-core filter drier, a drain pan, a disconnect switch, an economizer, pressure switches, phase monitors, and humidity sensors, among other things. 
     The HVAC unit  12  may receive power through a terminal block  46 . For example, a high voltage power source may be connected to the terminal block  46  to power the equipment. The operation of the HVAC unit  12  may be governed or regulated by a control board  48 . The control board  48  may include control circuitry connected to a thermostat, sensors, and alarms. One or more of these components may be referred to herein separately or collectively as the control device  16 . The control circuitry may be configured to control operation of the equipment, provide alarms, and monitor safety switches. Wiring  49  may connect the control board  48  and the terminal block  46  to the equipment of the HVAC unit  12 . 
       FIG. 3  illustrates a residential heating and cooling system, also in accordance with present techniques. The residential heating and cooling system  50  may provide heated and cooled air to a residential structure, as well as provide outside air for ventilation and provide improved indoor air quality (IAQ) through devices such as ultraviolet lights and air filters. In the illustrated embodiment, the residential heating and cooling system  50  is a split HVAC system. In general, a residence  52  conditioned by a split HVAC system may include refrigerant conduits  54  that operatively couple the indoor unit  56  to the outdoor unit  58 . The indoor unit  56  may be positioned in a utility room, an attic, a basement, and so forth. The outdoor unit  58  is typically situated adjacent to a side of residence  52  and is covered by a shroud to protect the system components and to prevent leaves and other debris or contaminants from entering the unit. The refrigerant conduits  54  transfer refrigerant between the indoor unit  56  and the outdoor unit  58 , typically transferring primarily liquid refrigerant in one direction and primarily vaporized refrigerant in an opposite direction. 
     When the system shown in  FIG. 3  is operating as an air conditioner, a heat exchanger  60  in the outdoor unit  58  serves as a condenser for re-condensing vaporized refrigerant flowing from the indoor unit  56  to the outdoor unit  58  via one of the refrigerant conduits  54 . In these applications, a heat exchanger  62  of the indoor unit functions as an evaporator. Specifically, the heat exchanger  62  receives liquid refrigerant, which may be expanded by an expansion device, and evaporates the refrigerant before returning it to the outdoor unit  58 . 
     The outdoor unit  58  draws environmental air through the heat exchanger  60  using a fan  64  and expels the air above the outdoor unit  58 . When operating as an air conditioner, the air is heated by the heat exchanger  60  within the outdoor unit  58  and exits the unit at a temperature higher than it entered. The indoor unit  56  includes a blower or fan  66  that directs air through or across the indoor heat exchanger  62 , where the air is cooled when the system is operating in air conditioning mode. Thereafter, the air is passed through ductwork  68  that directs the air to the residence  52 . The overall system operates to maintain a desired temperature as set by a system controller. When the temperature sensed inside the residence  52  is higher than the set point on the thermostat, or the set point plus a small amount, the residential heating and cooling system  50  may become operative to refrigerate additional air for circulation through the residence  52 . When the temperature reaches the set point, or the set point minus a small amount, the residential heating and cooling system  50  may stop the refrigeration cycle temporarily. 
     The residential heating and cooling system  50  may also operate as a heat pump. When operating as a heat pump, the roles of heat exchangers  60  and  62  are reversed. That is, the heat exchanger  60  of the outdoor unit  58  will serve as an evaporator to evaporate refrigerant and thereby cool air entering the outdoor unit  58  as the air passes over outdoor the heat exchanger  60 . The indoor heat exchanger  62  will receive a stream of air blown over it and will heat the air by condensing the refrigerant. 
     In some embodiments, the indoor unit  56  may include a furnace system  70 . For example, the indoor unit  56  may include the furnace system  70  when the residential heating and cooling system  50  is not configured to operate as a heat pump. The furnace system  70  may include a burner assembly and heat exchanger, among other components, inside the indoor unit  56 . Fuel is provided to the burner assembly of the furnace  70  where it is mixed with air and combusted to form combustion products. The combustion products may pass through tubes or piping in a heat exchanger separate from heat exchanger  62 , such that air directed by the blower  66  passes over the tubes or pipes and extracts heat from the combustion products. The heated air may then be routed from the furnace system  70  to the ductwork  68  for heating the residence  52 . 
       FIG. 4  is an embodiment of a vapor compression system  72  that can be used in any of the systems described above. The vapor compression system  72  may circulate a refrigerant through a circuit starting with a compressor  74 . The circuit may also include a condenser  76 , an expansion valve(s) or device(s)  78 , and an evaporator  80 . The vapor compression system  72  may further include a control panel  82  that has an analog to digital (A/D) converter  84 , a microprocessor  86 , a non-volatile memory  88 , and/or an interface board  90 . The control panel  82  and its components may function to regulate operation of the vapor compression system  72  based on feedback from an operator, from sensors of the vapor compression system  72  that detect operating conditions, and so forth. 
     In some embodiments, the vapor compression system  72  may use one or more of a variable speed drive (VSDs)  92 , a motor  94 , the compressor  74 , the condenser  76 , the expansion valve or device  78 , and/or the evaporator  80 . The motor  94  may drive the compressor  74  and may be powered by the variable speed drive (VSD)  92 . The VSD  92  receives alternating current (AC) power having a particular fixed line voltage and fixed line frequency from an AC power source, and provides power having a variable voltage and frequency to the motor  94 . In other embodiments, the motor  94  may be powered directly from an AC or direct current (DC) power source. The motor  94  may include any type of electric motor that can be powered by a VSD or directly from an AC or DC power source, such as a switched reluctance motor, an induction motor, an electronically commutated permanent magnet motor, or another suitable motor. 
     The compressor  74  compresses a refrigerant vapor and delivers the vapor to the condenser  76  through a discharge passage. In some embodiments, the compressor  74  may be a centrifugal compressor. The refrigerant vapor delivered by the compressor  74  to the condenser  76  may transfer heat to a fluid passing across the condenser  76 , such as ambient or environmental air  96 . The refrigerant vapor may condense to a refrigerant liquid in the condenser  76  as a result of thermal heat transfer with the environmental air  96 . The liquid refrigerant from the condenser  76  may flow through the expansion device  78  to the evaporator  80 . 
     The liquid refrigerant delivered to the evaporator  80  may absorb heat from another air stream, such as a supply air stream  98  provided to the building  10  or the residence  52 . For example, the supply air stream  98  may include ambient or environmental air, return air from a building, or a combination of the two. The liquid refrigerant in the evaporator  80  may undergo a phase change from the liquid refrigerant to a refrigerant vapor. In this manner, the evaporator  80  may reduce the temperature of the supply air stream  98  via thermal heat transfer with the refrigerant. Thereafter, the vapor refrigerant exits the evaporator  80  and returns to the compressor  74  by a suction line to complete the cycle. 
     In some embodiments, the vapor compression system  72  may further include a reheat coil in addition to the evaporator  80 . For example, the reheat coil may be positioned downstream of the evaporator relative to the supply air stream  98  and may reheat the supply air stream  98  when the supply air stream  98  is overcooled to remove humidity from the supply air stream  98  before the supply air stream  98  is directed to the building  10  or the residence  52 . 
     It should be appreciated that any of the features described herein may be incorporated with the HVAC unit  12 , the residential heating and cooling system  50 , or any other suitable HVAC systems. Additionally, while the features disclosed herein are described in the context of embodiments that directly heat and cool a supply air stream provided to a building or other load, embodiments of the present disclosure may be applicable to other HVAC systems as well. For example, the features described herein may be applied to mechanical cooling systems, free cooling systems, chiller systems, or other heat pump or refrigeration applications. 
     With the foregoing in mind,  FIG. 5  is a perspective view of an embodiment of a flow generating device  100 , such as an axial fan, which may be used in the HVAC unit  12 , the residential heating and cooling system  50 , or any other suitable HVAC system. For example, in some embodiments, the flow generating device  100  discussed herein may include the fan  32  of the HVAC unit  12  or the fan  64  of the outdoor unit  58 . To facilitate discussion, the flow generating device  100  and its components will be described with reference to a longitudinal axis or direction  102 , a vertical axis or direction  104 , and a lateral axis or direction  106 . The flow generating device  100  includes a housing  108 , or a fan shroud, which includes a channel  110 , or a venturi, defined therein. The channel  110  defines a flow path  112  for a fluid, such as air, which may flow through the housing  108  via the channel  110 . A fan assembly  114  is disposed within a portion of the channel  110 , or all of the channel  110 , and is configured to facilitate directing the air along the flow path  112 . 
     The fan assembly  114  includes a central shaft  118  that is positioned along the longitudinal axis  102  and is configured to rotate about an axis or centerline  120  of the channel  110  and/or the central shaft  118 . The central shaft  118  is coupled to an actuator that is configured to drive rotation of the central shaft  118  about the centerline  120 . For example, the actuator may include an electric motor, a hydraulic motor, a servo motor, or any other suitable actuator that may be used to rotate the central shaft  118  about the centerline  120 . The actuator may be coupled to the housing  108  via mounting brackets that substantially restrict movement of the actuator and/or the central shaft  118  relative to the housing  108 . Accordingly, the mounting brackets may substantially maintain a position of the central shaft  118  with respect to the centerline  120 . 
     The fan assembly  116  further includes a hub  122  that is coupled to the central shaft  118 . The hub  122  includes a plurality of fan blades  124  that extend radially therefrom relative to the centerline  120 . The fan blades  124  extend toward an interior surface  125  of the channel  110 , such that a radial gap  127  is formed between the fan blades  124  and the interior surface  125 . The fan blades  124  may be coupled to the hub  122  using fasteners, such as rivets, bolts, pressure pins, any suitable adhesive, such as bonding glue, a metallurgical process, such as welding or brazing, or the like. However, in other embodiments, the hub  122  and the fan blades  124  may be a single piece component that is integrally formed during manufacture of the flow generating device  100 . In any case, each of the fan blades  124  includes an angled profile or curvature, which facilitates generation of an air flow through the channel  110  during operation of the flow generating device  100 . 
     For example, as described in greater detail herein, each of the fan blades  124  includes a pressure surface  126 , which is shown in  FIG. 7 , that is oriented toward an intended direction of air flow through the channel  110 , and a suction surface  128  disposed opposite the pressure surface  126 . The pressure surface  126  may engage with air surrounding the fan assembly  114  while the fan assembly  114  rotates about the centerline  120 , such that the pressure surface  126  may direct the air through the channel  110  of the flow generating device  100 . For example, in some embodiments, the actuator may be configured to rotate the fan assembly  114  counter-clockwise about the centerline  120 , as shown by arrow  130 , to cause the fan blades  124  to generate an air flow through the channel  110  along the flow path  112  from an upstream end portion  136  of the housing  108  to a downstream end portion  138  of the housing  108 . In other embodiments, the actuator is configured to rotate clockwise about the centerline  120  and, thus, direct the air flow in a direction  139  along the axis  102 . In such embodiments, the suction surfaces  128  of the blades shown in the illustrated embodiment would be pressure surfaces of the fan blades  124 , and, similarly, the pressure surfaces  126  would be suction surfaces. 
     As noted above, operation of the flow generating device  100  may generate a region of high pressure air proximate the downstream end portion  138  and a region of low pressure air proximate the upstream end portion  136 . In other words, an air pressure near the downstream end portion  138  of the housing  108  may be greater than an air pressure near the upstream end portion  136  of the housing  108 . This pressure differential may generate a secondary air flow, or a backflow of air, which flows through the radial gap  127  from the pressure surface  126  toward the suction surface  128  of the fan blades  124 . As such, the backflow of air may flow in the direction  139 , which is generally opposite to a direction of the air flow along the flow path  112  that is generated by the fan blades  124 . The backflow of air generates vortices near radial edges  132  of the fan blades  124 , which may increase a velocity of air flowing across the suction surface  128  and generate an induced drag force on the fan blades  124  that increases a power consumption of the actuator during operation of the flow generating device  100 . 
     Accordingly, embodiments of the flow generating device  100  discussed herein include a winglet  140  that is coupled to each of the fan blades  124  and is configured to reduce or substantially eliminate the backflow of air through the radial gap  127  and around the radial edges  132  of the fan blades  124 . As discussed in greater detail herein, the winglet  140  may extend from the pressure surface  126  of the fan blades  124  into the channel  110 , such that the winglet  140  extends along a direction of the flow path  112  through the channel  110 . In other words, the winglets  140  may extend generally along the longitudinal direction  102 . The winglets  140  may thus block undesirable air flow around the radial edge  132  from the pressure surface  126  to the suction surface  128  of the fan blades  124  during operation of the flow generating device  100 . As such, the winglets  140  may reduce aerodynamic drag generated while the fan assembly  114  rotates about the centerline  120 , and thus, reduce a power consumption of the actuator. In this manner, the winglets  140  may enhance an operational efficiency of the HVAC system that utilizes the flow generating device  100 . As described in greater detail herein, in some embodiments, the winglets  140  couple to a portion of the radial edge  132  corresponding to a section of the fan blades  124  protruding axially from the channel  110  along the direction  139 . Accordingly, the winglets  140  may reduce a backflow of air, in particular, around the portion of the fan blades  124  axially protruding from the channel  110 . 
       FIG. 6  is a perspective view of an embodiment of the winglet  140 . The winglet  140  includes an upper edge  142 , or a leading edge, and a lower edge  144 , or a coupling edge, that cooperatively form a perimeter of the winglet  140 . As described in greater detail herein, the lower edge  144  may be configured to couple to, or otherwise be positioned proximate to, the pressure surface  126  of one of the fan blades  124  to enable blockage of air flow between the lower edge  144  of the winglet  140  and the pressure surface  126  of the fan blade  124 . A portion of the upper edge  142  of the winglet  140  may be a leading edge  146  that is disposed near a first end portion  148  of the winglet  140 . Additionally, the winglet  140  includes a trailing edge  150  that is disposed near a second end portion  152  of the winglet  140 . Specifically, the leading edge  146  may be defined as a first portion of the upper edge  142  extending between a commencing point  154  of the winglet  140  and an apex  156  of the winglet  140 . The apex  156  may be indicative of a point along the upper edge  142  at which a height  158  of the winglet  140  or, in other words, a distance between the upper edge  142  and the lower edge  144 , is at a maximum value. Accordingly, the height  158  may be indicative of a total height of the winglet  140  and the upper edge  142 . For example, in some embodiments, the height  158  of the winglet  140  at the apex  156  may extend approximately 0.5 centimeters (cm), 1 cm, 2 cm, 3 cm, 4 cm, or more centimeters. 
     In certain embodiments, a height of the leading edge  146  may increase from substantially zero at the commencing point  154  to the height  158  of the apex  156 . For example, in some embodiments, the height of the leading edge  146  may increase linearly from the commencing point  154  to the apex  156 . In other embodiments, the height of the leading edge  146  may increase from the commencing point  154  to the apex  156  in an exponential profile, a logarithmic profile, or in any other suitable profile. For example, as described in greater detail herein, the height of the leading edge  146  may increase proportionally to a change in radial thickness of the fan blades  124 . It should be noted that in certain embodiments, the commencing point  154  of the leading edge  146  may be disposed at a predetermined height, rather than a height that is substantially zero, such as in the illustrated embodiment of  FIG. 6 . The trailing edge  150  may be defined as a second portion of the upper edge  142  extending between the apex  156  and a terminating point  160  of the winglet  140 . That is, the trailing edge  150  may be disposed posterior to the leading edge  146  relative to a rational direction of the fan blades  124 . Similar to the leading edge  146  discussed above, the trailing edge  150  may include any suitable profile that extends between the apex  156  and the terminating point  160 . 
     A distance along the lower edge  144  between the commencing point  154  and the terminating point  160  of the winglet  140  will be referred to herein as a total length  162  of the winglet  140 . A position of the apex  156  along the total length  162  may be determined by a projection point  164 , which is indicative of a point along the total length  162  at which the apex  156  is positioned. A distance between the commencing point  154  and the projection point  164  will be referred to herein as a leading edge length  166  of the winglet  140 . In other words, the total length  162  is indicative of a length of both the leading edge  146  and the trailing edge  150 , while the leading edge length  166  is indicative of a length of the leading edge  146  relative to the total length  162 . As such, adjusting a magnitude of the leading edge length  166  and adjusting a magnitude of the height  158  of the apex  156  will adjust a profile of the winglet  140 . In some embodiments, the leading edge length  166  may be 50%, 60%, 70%, 80%, or more than 80% of the total length  162 , while the height  158  of the apex  156  may be 20%, 30%, 40%, 50%, or more than 50% of the total length  162 . In other embodiments, the leading edge length  166  may be 0% or 100% of the total length  162 . In such embodiments, the winglet  140  may include a generally triangular profile, rather than a generally teardrop profile as shown in the illustrative embodiment of  FIG. 6 . In yet further embodiments, the winglet  140  may include, for example, a rectangular profile, or any other suitable geometric profile. 
     As shown in the illustrated embodiment of  FIG. 6 , the winglet  140  may include one or more mounting tabs  170  that extend substantially crosswise from an interior surface  167  of the winglet  140 . In other embodiments, the mounting tabs  170  may form any suitable angle with the interior surface  167  of the winglet  140 . The mounting tabs  170  enable the winglet  140  to couple to a respective fan blade  168 , as shown in  FIG. 7 , of the fan blades  124 . Accordingly, the winglet  140  may bracket a portion of the fan blade  168 . For example, each of the mounting tabs  170  may include an aperture  172  that is configured to concentrically align with a respective aperture  173 , as shown in  FIG. 7 , extending through, or into, the fan blade  168 . Accordingly, fasteners such as bolts, rivets, friction pins, or the like may be disposed within the apertures  172 ,  173  to couple the mounting tabs  170  to the fan blade  168 . In other embodiments, the mounting tabs  170  may be coupled to the fan blade  124  using an adhesive, such as bonding glue, spot welds, or other fastening process. In such embodiments, the aperture  172  may be omitted from the mounting tabs  170 , such that an adhesive may engage with a full surface area of the mounting tabs  170  to couple the mounting tabs  170  to the fan blade  168 . In any case, the mounting tabs  170  may be disposed either on the pressure surface  126  of the fan blade  168  or on the suction surface  128 , as shown in  FIG. 9 , of the fan blade  168 . 
     In other embodiments, the mounting tabs  170  may be omitted from the winglet  140 , such that the lower edge  144  of the winglet  140  may couple directly to the fan blade  168 . For example, the lower edge  144  of the winglet  140  may be coupled to the fan blade  168  using a suitable fastening process or material such as, for example, a weld or bonding glue. It should be noted that the winglet  140  may be constructed of sheet metal, aluminum, fiberglass, polymeric materials, or any other suitable material. In some embodiments, the winglet  140  may be constructed of a same material as the fan blade  168 . For example, the fan blade  168  and the winglet  140  may each be constructed of sheet metal. However, in other embodiments, the winglet  140  and the fan blade  168  may each include a different material. In still further embodiments, the winglet  140  may be integral to the fan blade  168 , such that the winglet  140  and the fan blade  168  are constructed from a single, continuous piece of material. 
     Turning now to  FIG. 7 , each fan blade  168  of the fan blades  124  includes a leading edge  180  that faces a direction of travel or rotation, as shown by arrow  134 , of the fan blade  168  and a trailing edge  182 . Specifically, the leading edge  180  is defined as extending between a leading tip  184  of the fan blade  168  and a first engagement point  190  of the fan blade  168  and the hub  122 . The trailing edge  182  is defined as extending between a trailing tip  192  of the fan blade  168  and a second engagement point  194  between the fan blade  168  and the hub  122 . Accordingly, the radial edge  132  of the fan blade  168  extends between the leading tip  184  and the trailing tip  192 . However, it should be noted that in certain embodiments, the radial edge  132  may include a portion or all of the leading edge  180  and/or the trailing edge  182 . 
     The fan blade  168  includes a non-uniform profile that extends from the leading edge  180  to the trailing edge  182  of the fan blade  168 . For example, the fan blade  168  may include a tip portion  196  disposed near the leading edge  180 , which initially engages with the air with respect to rotation of the fan blade  168  about the centerline  120  in the direction indicated by the arrow  134 . In the illustrative embodiment of  FIG. 7 , the tip portion  196  includes a portion of the fan blade  168  disposed between the leading edge  180  and a line  195 . In some embodiments, the line  195  extends from the centerline  120  toward the commencing point  154  of the winglet  140 . The tip portion  196  thus includes a portion of both the pressure surface  126  and the suction surface  128  of the fan blade  168 . As described in greater detail herein, a first radial thickness  198 , as shown in  FIG. 8 , of the tip portion  196  may be relatively small, such that a relatively small surface area of the pressure surface  126  corresponding to the tip portion  196  engages with air during operation of the flow generating device  100 . Accordingly, a pressure differential between the pressure surface  126  and the suction surface  128  near the tip portion  196  may be relatively small. As such, this relatively small pressure differential may generate a marginal backflow of air between the pressure surface  126  and the suction surface  128  at the tip portion  196 , which may insignificantly affect an operational efficiency of the flow generating device  100 . Accordingly, in some embodiments, the commencing point  154  of the winglet  140  may be disposed counter clockwise from the tip portion  196  with respect to the axis  102  and/or the centerline  120  or downstream from the tip portion  196  relative to a direction of travel or rotation of the fan blade  168 . Accordingly, the radial edge  132  may include a first open edge  200 , or an uncovered edge, which extends along the radial edge  132  from the leading tip  184  to the commencing point  154  in a counter clockwise direction  197 . However, it should be noted that in other embodiments, the winglet  140  may be coupled to the tip portion  196  of the fan blade  168 . In such embodiments, the commencing point  154  of the winglet  140  may be disposed adjacent to the leading tip  184  of the fan blade  168 , such that the radial edge  132  does not include the first open edge  200 . 
     The winglet  140  may be coupled to the fan blade  168  in a position that is counter clockwise to the first open edge  200  along the radial edge  132  and extends along the radial edge  132  toward the trailing tip  192  of the fan blade  168 . The winglet  140  may thus block a backflow of air from the pressure surface  126  to the suction surface  128  along the radial edge  132  of the fan blade  168 . As discussed in greater detail herein, in some embodiments, the winglet  140  may not extend fully toward the trailing tip  192  of the fan blade  168 . In such embodiments, the radial edge  132  of the fan blade  168  includes a second open edge  202  that extends from the terminating point  160  of the winglet  140  to the trailing tip  192  of the fan blade  168  in the counter clockwise direction  197 . However, it should be noted that, in other embodiments, the winglet  140  may extend fully to the trailing tip  192  of the fan blade  168 , such that the radial edge  132  does not include the secondary open edge  202 . 
     In some embodiments, a radial thickness of the fan blade  168  may increase from the leading edge  180  or along the radial edge  132  in the counter clockwise direction  197 . The increasing radial thickness of the fan blade  168  generates a pressure gradient along the pressure surface  126  that increases from the leading edge  180  to the trailing edge  182  as the fan blade  168  rotates about the centerline  120  in the direction  134 . For example, the fan blade  168  may compress air from the leading edge  180  toward the trailing edge  182  while the fan blade  168  rotates about the centerline  120  in the direction indicated by the arrow  134 . In such embodiments, a tendency of air to backflow around the radial edge  132  increases proportionally to an increase in the pressure gradient along the pressure surface  126  of the fan blade  168 . In other words, the tendency of air to backflow around the radial edge  132  increases from the leading tip  184  to the trailing tip  192  of the fan blade  168 . As such, a height of the leading edge  146  of the winglet  140  may increase from the commencing point  154  to the apex  156  to account for the variation in air pressure along the radial edge  132  of the fan blade  168 . 
     As shown in  FIG. 8 , a radial thickness along the fan blade  168  may be indicative of a percentage of a radius  203 , or a total radius, of the fan assembly  114 , which extends from the centerline  120  toward an outermost point of the fan blades  124 . For example, the radial thickness may be defined by a distance between intersection points  204  of the fan blade  168  and respective lines  206  that extend radially from the centerline  120 . The tip portion  196  of the fan blade  168  may include a substantially small percentage of the radius  203 , referred to herein as the relatively small first radial thickness  198 , and thus, generate a marginal backflow of air around the radial edge  132  during rotation of the fan assembly  114 . For example, the relatively small first radial thickness  198  may be 5%, 7%, 12%, or 15% of the radius  203 . However, in other embodiments, the relatively small first radial thickness  198  may be less than 5% of the radius  203  or greater than 15% of the radius  203 . In any case, the winglet  140  may be omitted from a section of the radial edge  132  corresponding to the tip portion  196 , referred to herein as the first open edge  200 . The fan blade  168  includes a relatively small second radial thickness  208  disposed counter clockwise of the tip portion  196  with respect to the axis  102  or the centerline  120 , which may thus correspond to a relatively small second height  210  of the upper edge  142 . For example, the relatively small second radial thickness  208  may include 5%, 10%, 15%, 20%, or more than 20% of the radius  203 . Accordingly, the winglet  140  may substantially block a backflow of air near this section of the fan blade  168 . Similarly, a relatively medium third radial thickness  212  of the fan blade  168  may correspond with a relatively medium third height  214  of the upper edge  142 . In some embodiments, the relatively medium third radial thickness  212  may include 40%, 50%, 60%, 70%, or more than 70% of the radius  203 . A relatively large fourth radial thickness  216  of the fan blade  168  may be indicative of a section of the radial edge  132  at which a tendency of the air to backflow is greatest. For example, the relatively large fourth radial thickness  216  may be 60%, 70%, 80%, 90%, or more than 90% of the radius  203 . Accordingly, the apex  156  of the winglet  140  may be radially aligned with the relatively large fourth radial thickness  216  of the fan blade  168 . The height  158  of the apex  156  may be sufficient to block substantially all backflow of air near the relatively large fourth radial thickness  216  of the fan blade  168 . As such, a height of the winglet  140  may gradually increase along the winglet  140  based on the increase in radial thickness of the fan blade  168 , such that the height of the winglet  140  increases proportional to an increase in the pressure gradient on the pressure surface  126 . 
     Turning now to  FIG. 9 , as noted above, the fan blades  124  may each include a first section  220 , or an exposed portion, which protrudes axially from the channel  110  relative to the longitudinal axis  102  and a second section  222  that extends into the channel  110 . In other words, the fan assembly  114  is disposed partially within the channel  110 , such that the first section  220  of the fan blades  124  is disposed upstream of an end portion  224  of the channel  110  relative to a direction  223  of fluid flow through the channel  110 . For clarity, the direction  223  of fluid flow may be along the flow path  112  from the upstream end portion  136  of the housing  108  to the downstream end portion  138  of the housing  108 . Conversely, the second section  222  of the fan blades  124  is disposed downstream of the end portion  224  of the channel  110  relative to the direction  223  of fluid flow through the channel  110 . The end portion  224  of the channel  110  may be indicative of an upstream end portion of the channel  110 , which may be axially aligned with the upstream end portion  136  of the housing  108 . Similarly, a downstream end portion  226  of the channel  110  may be axially aligned with the downstream end portion  138  of the housing  108 . 
     In some embodiments, the second open edge  202  of the radial edge  132  may correspond to the second section  222  of the fan blades  124 . In other words, the second open edge  202  may be disposed downstream of the end portion  224  of the channel  110 , and thus, within the channel  110 . The radial gap  127  between the interior surface  125  of the channel  110  and the second open edge  202  of the fan blades  124  may be relatively small, and thus, substantially mitigate air flow through the radial gap  127  from the pressure surface  126  to the suction surface  128  of the fan blades  124 . Accordingly, the winglet  140  may not be coupled to the second open edge  202  of the fan blades  124 , as noted above, because the housing  108  may substantially block a backflow of air along the second section  222  of the fan blades  124 . 
     The winglets  140  may couple to a portion of the radial edge  132  corresponding to the first section  220  of the fan blades  124 . In other words, the winglets  140  are coupled to a portion of the fan blades  124  that is disposed upstream of the end portion  224  of the channel  110  relative to the direction  223  of the fluid flow through the channel  110 . Specifically, the terminating point  160  of each of the winglets  140  may be disposed adjacent to, or upstream of the end portion  224  of the channel  110 . Accordingly, the winglets  140  substantially block the backflow of air around a portion of the radial edge  132  corresponding to the first section  220  of the fan blades  124  or, in other words, a portion of the radial edge  132  that is disposed upstream of the end portion  224  of the channel  110 . It should be noted that, in certain embodiments, the winglet  140  may be coupled to a portion of the radial edge  132  that is disposed within the channel  110  or, in other words, the winglet  140  may be disposed along a portion or all of the second section  222  of the fan blades  124 . In some embodiments, the first section  220  of the fan blades  124  may include 50%, 60%, 70%, 80%, or more than 80% of a total surface area of the pressure surface  126  of the fan blades  124 , the suction surface  128  of the fan blades  124 , or both. However, in other embodiments, the first section  220  of the fan blades  124  may include less than 50% of a total surface area of the fan blades  124 . 
     In some embodiments, a blade angle  230  of the fan blades  124  with respect to the axis  104  may enable a portion of the winglet  140  to axially protrude downstream of the end portion  224  and into the channel  110  even while the winglet  140  is coupled to the first section  220  of the fan blades  124  that is disposed upstream of the end portion  224 . For example, in some embodiments, the height  158  of the apex  156  may enable the apex  156  of the winglet  140  to extend within at least a portion of the channel  110  due to the orientation of the winglets  140  via the blade angle  230 . In such embodiments, the terminating point  160  of the winglet  140  is disposed upstream of the end portion  224  of the channel  110 , such that the lower edge  144  of the winglet  140  does not extend into the channel  110 . In some cases, the apex  156  of the winglet  140  may thus facilitate blocking the backflow of air along a transitioning point that is disposed between the first section  220  of the fan blades  124  and the second section  222  of the fan blades  124 . 
     Technical effects of the winglet  140  may include a reduction in induced drag on the fan blades  124  during operation of the flow generating device  100 . For example, the winglet  140  may block, or substantially mitigate the formation of drag inducing vortices near the radial edge  132  of the fan blades  124 . Accordingly, the winglet  140  may enhance an operation efficiency of the flow generating device  100 , and thus, enhance an operational efficiency of an HVAC system utilizing the flow generating device  100 . 
     As discussed above, the aforementioned embodiments of the flow generating device  100  may be used on the HVAC unit  12 , the residential heating and cooling system  50 , or in any other suitable HVAC system. However it should be noted that the specific embodiments described above have been shown by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure.