Patent Publication Number: US-2019184785-A1

Title: Fan stator construction to minimize axial depth

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Ser. No. 62/599,859, filed Dec. 18, 2017, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Exemplary embodiments relate generally to transport refrigeration systems and, more particularly, to a condenser fan assembly for use in a transport refrigeration system. 
     Transport refrigeration systems are commonly employed in connection with refrigerated transport trailers used in shipping perishable goods. The transport trailer is adapted to be connected to and towed by a truck tractor. The transport refrigeration system includes a refrigeration unit, an electric generator assembly and an engine for driving the electric generator, all supported on a framework structural support configured to be mounted to the front wall of the trailer. 
     European regulations strictly limit the length of a transport refrigeration trailer and how far a transport refrigeration unit can protrude from the front wall of such trailers. These limits severely restrict the front-to-back space (depth) available within the unit for component arrangement. As a result, the axial (depth-wise) extent of all components must be minimized without impacting the functionality of the unit. This constraint particularly impacts the air management system components, i.e., fans, which must not only be compact while providing high performance, but also take full advantage of the space available to provide a flow path sufficient to minimize flow losses. 
     BRIEF DESCRIPTION 
     According to an embodiment, a transport refrigeration unit for use with a transport trailer includes a structural framework mountable to a wall of the transport trailer, a condenser heat exchanger unit mounted to the structural framework, an evaporator housing separated from the condenser heat exchanger by a distance, and at least one condenser fan assembly positioned aft of the condenser heat exchanger unit and forward of the evaporator housing. The at least one condenser fan assembly includes a fan rotor defining an inlet end. The fan rotor is rotatable about a fan axis. A casing defines a central opening and the fan rotor is arranged within the central opening. The casing includes a plurality of openings spaced about a periphery of the casing. A portion of an airflow moving through the at least one condenser fan assembly is expelled from the at least one condenser fan assembly radially via the plurality of openings. 
     In addition to one or more of the features described herein, or as an alternative, in further embodiments substantially all of the airflow output from a discharge end of the at least one condenser fan assembly turns radially relative to the fan axis at a position upstream from the evaporator housing. 
     In addition to one or more of the features described herein, or as an alternative, in further embodiments the casing of the at least one condenser fan assembly further comprises a shroud body having a hollow interior, a plurality of pylons extending from a surface of the shroud body, and a stator coupled to the plurality of pylons. The stator includes a plurality of guide vanes defining a discharge end of the fan assembly. The stator is arranged downstream from the fan rotor with respect to the airflow. 
     In addition to one or more of the features described herein, or as an alternative, in further embodiments the shroud body has a generally planar configuration. 
     In addition to one or more of the features described herein, or as an alternative, in further embodiments axial length of the shroud body is less than an axial length of the fan rotor. 
     In addition to one or more of the features described herein, or as an alternative, in further embodiments the fan rotor includes a plurality of fan blades and an axial length of the shroud body is less than an axial length of the plurality of fan blades. 
     In addition to one or more of the features described herein, or as an alternative, in further embodiments the plurality of pylons maximize the distance between the plurality of fan blades and the plurality of guide vanes. 
     In addition to one or more of the features described herein, or as an alternative, in further embodiments fan rotor further comprises a central hub, and the shroud body is axially offset from central hub. 
     In addition to one or more of the features described herein, or as an alternative, in further embodiments the shroud body is arranged upstream from the central hub. 
     In addition to one or more of the features described herein, or as an alternative, in further embodiments the plurality of pylons is spaced about a periphery of the shroud body and a plurality of openings is defined between adjacent pylons of the plurality of pylons. 
     In addition to one or more of the features described herein, or as an alternative, in further embodiments the plurality of pylons is spaced equidistantly. 
     In addition to one or more of the features described herein, or as an alternative, in further embodiments the plurality of pylons includes a first pylon, a second pylon, and a third pylon, and a distance between the first pylon and the second pylon is different that a distance between the second pylon and the third pylon. 
     In addition to one or more of the features described herein, or as an alternative, in further embodiments the plurality of pylons extend substantially perpendicular to the surface of the shroud body. 
     In addition to one or more of the features described herein, or as an alternative, in further embodiments the plurality of pylons extend at an angle between 0 degrees and 90 degrees relative to the surface of the shroud body. 
     In addition to one or more of the features described herein, or as an alternative, in further embodiments the shroud body, the plurality of pylons, the stator hub, and the plurality of guide vanes are integrally formed. 
     According to another embodiment, a transport refrigeration unit for use with a transport trailer includes a structural framework mountable to a wall of the transport trailer, a condenser heat exchanger unit mounted to the structural framework, an evaporator housing separated from the condenser heat exchanger by a distance, and at least one condenser fan assembly for blowing air toward the evaporator housing and over the condenser heat exchanger unit. The at least one condenser fan assembly includes a fan rotor rotatable about a fan axis. A casing defines a central opening. The fan rotor is arranged within the central opening. The casing includes a plurality of openings spaced between pylons that extend axially. The condenser fan assembly is in close proximity to the evaporator housing such that a portion of an airflow moving through the at least one condenser fan assembly is expelled from the at least one condenser fan assembly radially via the plurality of openings due to the proximity of the evaporator housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  is perspective view of a portion of a transport refrigeration system; 
         FIG. 2  is a side view of a portion of a transport refrigeration unit of a transport refrigeration system; 
         FIG. 3  is a perspective view of a portion of a transport refrigeration unit of a transport refrigeration system; 
         FIG. 4  is a top view of the portion of the transport refrigeration unit  FIG. 3 ; 
         FIG. 5  is a side view of a condenser fan assembly of a transport refrigeration unit according to an embodiment; 
         FIG. 6  is a perspective view of an inlet end of a condenser fan assembly of  FIG. 5  according to an embodiment; 
         FIG. 7  is a perspective view of a discharge end of the condenser fan assembly of  FIG. 5  according to an embodiment; 
         FIG. 8  is a perspective view of a stator and casing of the condenser fan assembly of  FIG. 5  according to an embodiment; and 
         FIG. 9  is another perspective view of a stator and casing of the condenser fan assembly of  FIG. 5  according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
     Referring now to  FIGS. 1-4 , an example of a transport refrigeration system  20  is illustrated. As shown, the transport refrigeration system  20  includes a trailer  22  towed or otherwise transported by a tractor  24  including an operator&#39;s compartment or cab  26  and also including an engine (not shown), which acts as the drivetrain system of the system  20 . The system  20  additionally includes a transport refrigeration unit  30  configured to maintain cargo located within the trailer  22  at a selected temperature by cooling the cargo space of the trailer  22 . The transport refrigeration unit  30  is mounted at the front wall  28  of the trailer  22 . Although the transport refrigeration unit  30  is illustrated as being mounted to a trailer  22  pulled by a tractor  24 , in other embodiments, the transport refrigeration unit  30  may be adapted to cool a confined space, such as a rail car for example. 
     The transport refrigeration unit  30  includes a structural framework, designated generally at  32 , that forms a skeletal structure from which various components of the transport refrigeration unit  30  are supported. The transport refrigeration unit  30  includes an outer cover  34  ( FIG. 1 ) supported on the structural framework  32 . As is common, various panels or other portions of the outer cover  34  may be hinged and/or removable to provide efficient access to the interior of the transport refrigeration unit  30  to perform routine maintenance. The cover  34  is configured to cover not only the framework  32 , but also all of the components of the refrigeration unit  30 , including but not limited to a compressor (not shown), an evaporator and associated evaporator fan/motor assembly (not shown) disposed within the confines of the evaporator housing  36 , a condensing heat exchanger  38 , and the at least one condenser fan assembly  40 . 
     The transport refrigeration unit  30  is typically powered by a diesel engine  42 , separate from the engine of the tractor  24 . The engine  42  drives an electric generator (not shown) that produces and supplies electrical power to portion of the transport refrigeration unit including a compressor motor (not shown) that drives the compressor (not shown), the evaporator fan motor (not shown), and the motors associated with the one or more condenser fan assemblies  40 , as well as any other electrically powered equipment associated with the transport refrigeration unit  30 . 
     In the illustrated, non-limiting embodiment, best shown in  FIGS. 3 and 4 , the transport refrigeration unit  30  includes two condenser fan assemblies  40 , positioned above the diesel powered engine  42  and the electric generator (not shown) driven by the engine  42 , at the forward side of the structural framework  32 , aft of the condenser  38  and forward of the evaporator housing  36 . The condenser fan assemblies  40  may be arranged within the same plane, or alternatively, may be arranged at an angle relative to one another, as shown in the FIGS. By positioning the condenser fan assemblies  40  vertically and generally parallel to the plane of the evaporator housing  36 , the air, illustrated schematically with arrow A, output from the condenser fan assemblies  40  flows naturally along a horizontal axis towards the evaporator housing  36 . However, the evaporator housing  36  presents a barrier to further progression of the air flow, such that a major portion of the air flow discharged from the condenser fan assemblies  40  must turn ninety degrees and flow upward toward the top of the transport refrigeration unit  30  to be released to the atmosphere. In addition, about a quarter of the flow is designed to exit downwards through the engine compartment to help cool the engine container therein. The flow going downward has to make about a hundred and fifty degree turn to get around the evaporator housing  36 . As a result, in conventional systems, the amount of flow provided to the engine compartment is limited. 
     With reference now to  FIGS. 5-9 , an example of a condenser fan assembly  40  usable in a transport refrigeration unit  30  is shown in more detail. In the illustrated, non-limiting embodiment, the condenser fan assembly  40  is an axial flow fan including a fan rotor  42  and a fan stator  44  arranged in a serial airflow relationship; however, it should be understood that other suitable types of fans, such as a mixed flow fan for example, are also within the scope of the disclosure. 
     The fan rotor or impeller  42  has a plurality of fan blades  46  extending radially outwardly from a rotor hub  48  into an opening  50  defined by an outer casing  52 . Although the radially outer end  54  of each fan blade  46  is illustrated as being connected to or integrally formed with a fan shroud  56 , embodiments where the impeller  42  does not include a shroud  56  are also contemplated herein. A motor  58  operably coupled to the fan rotor  42  may be used to rotate the fan rotor  42  and the fan blades  46  about the fan axis X to cause air A to be drawn in and pass through the opening  50 . The motor  58  may be oriented such that an axis of rotation of the motor  58  is arranged parallel to or coaxial with the fan axis X. 
     The stator  44  includes a stationary central hub  60  and a plurality of stationary guide vanes  62  extending radially outward from the hub  60 . The distal ends  64  of the one or more of the guide vanes  62  may, but need not be connected to the outer casing  52 . The guide vanes  62  are located downstream from the fan blades  46  relative to the direction of airflow A through the opening  50 . The plurality of guide vanes  62  may be formed with any configuration, for example a planar configuration, or configurations including lean or sweep in the circumferential or axial directions. In operation, the fan rotor  42  is rotated at relatively high speeds to induce the flow of air A through the casing  52 , and in the process it creates a swirl in the direction of the fan rotation, such that the air A has both an axial component and a tangential component. The guide vanes  62  are disposed and shaped to straighten the flow exiting from the fan rotor  42 . 
     With specific reference now to  FIGS. 8 and 9 , the stator  44  and casing  52  of the condenser fan assembly  40  are illustrated in more detail. As shown, the casing  52  includes a cylindrical shroud frame  70  having a hollow interior  72  configured to define the opening  50  within which the fan rotor  42  is received. The inner diameter of the shroud frame  70  is slightly larger than the outer diameter of the fan rotor  42  to avoid interference during operation of the fan assembly  40 . Unlike conventional casings  52  which typically extend from an inlet end to a discharge end of a fan assembly  40 , the shroud frame  70  of the casing  52  extends over only a portion of the axial flow length of the fan assembly  40 . In the illustrated, non-limiting embodiment, an axial length of the shroud frame  70 , measured parallel to the fan axis X, is selected such a downstream surface  74  of the shroud frame  70  is arranged upstream from the stator hub  60 . As a result, no portion of the shroud frame  70  is arranged concentrically with the stator hub  60 . Alternatively, or in addition, the axial length of the shroud frame  70  may be less than an axial length of the fan blades  46  of the fan rotor  42 . 
     The casing  52  additionally includes a plurality of pylons  76  extending from the downstream surface  74  of the shroud frame  70 . Although the pylons  76  are illustrated as being substantially perpendicular to the downstream surface  74 , pylons  76  oriented at any angle to the downstream surface between 0 and 90 degrees are contemplated herein. The pylons  76  may be integrally formed with the shroud body  70 , or alternatively, may be connected thereto via any suitable means, such as fasteners for example. As shown, the pylons  76  are spaced at intervals about the periphery of the shroud frame  70  such that an opening  78  is formed between adjacent pylons  76 . The pylons  76  may, but need not be equidistantly spaced based on the geometry of the surrounding components. 
     The plurality of pylons  76  provides structural rigidity to the shroud body  70 . Accordingly, the contour of each of the plurality of pylons  76  may be selected based on stresses anticipated during operation of the condenser fan assembly  40 . In the illustrated embodiment, the circumferential width of each pylon  76  decreases along an axial length of the pylon  76 . However, it should be understood that a pylon  76  having any contour as well as a plurality of pylons  76  having varying contours are within the scope of the disclosure. Further, the outer end  64  of each of the stator guide vanes  62  is connected to a corresponding pylon  76  of the casing  52 , such as at a distal end  80  of the pylon  76  for example. In an embodiment, the stator  44  and the casing  52  may be integrally formed as a single component, such as via a die casting, plastic injection molding, or three-dimensional printing process for example. In other embodiments, the stator guide vanes  62  may be configured to removably or permanently connect to the pylons  76  via any suitable mechanism, including but not limited to fasteners, welds, and/or interlocking connectors for example. 
     The pylons  76  projecting downstream from the shroud frame  70  maximize the distance between the fan blades  46  and the guide vanes  62  to minimize noise generated during operation of the condenser fan assembly  40 . Further, by using a plurality of spaced pylons  76  rather than a conventional casing  52  having a solid sidewall, significantly sized openings  78  are formed between adjacent pylons  76 . Because the condenser fan assembly  40  is positioned in close proximity to the evaporator housing  36 , i.e. such as a distance of less than 4 inches in some embodiments, a portion of the airflow A downstream from the rotor  42  is able to turn and exit the fan assembly  40  radially through these openings  78  due to the proximity to the evaporator housing  36 . As a result, radial turning of the entire flow occurs much sooner than if the condenser fan assembly  40  included a conventional casing extending the full length (i.e. from inlet end to discharge end) of the fan assembly  40 . 
     In an embodiment, the construction illustrated and described herein, reduces the total power required by the condenser fan assembly  40 , such as in a transport refrigeration unit  20 , by 40% or more when used in close proximity to the evaporator housing. As used herein the term close proximity, may refer to clearances between the discharge end of the fan assembly  40  and the evaporator housing  36  of up to about 4 inches. Further, the construction illustrated and described herein, reduces the total power required by the condenser fan assembly, such as in a transport refrigeration unit  20 , by up to about 50% when used in constructions of a transport refrigeration unit where the clearance between the discharge end of the fan assembly  40  and the evaporator housing  36  is equal to or greater than about 4 inches. 
     The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof. 
     While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.