Patent Publication Number: US-10787266-B2

Title: Fan bypass and shutoff check valve

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. patent application Ser. No. 15/481,661 filed Apr. 7, 2017, the contents of which are incorporated by reference herein in their entirety. 
    
    
     BACKGROUND 
     Exemplary embodiments pertain to aircraft environmental control systems. More particularly, the present disclosure relates to a bypass control of a ram air fan for an aircraft environmental control system. 
     Environmental control systems (ECS&#39;s) supply airflow to an interior of an aircraft to condition, for example, a passenger cabin, crew compartment and/or cargo compartment. In some ECS architectures a ram air fan is utilized to draw ram air into the ECS and across a ram air heat exchanger to condition a fluid flowing through the ram air heat exchanger. The ram air fan is driven by, for example an electric motor or a turbine. The typical air bearing ram air fan is not required to operate during flight for performance reasons, but will uncontrollably windmill during flight, if not driven by an electric motor or turbine. To control ram air fan rotation during flight and to keep the rotating assembly supported by an air film, the ram air fan is typically powered to operate at a specified minimum speed. 
     BRIEF DESCRIPTION 
     In one embodiment, a ram air fan and fan bypass shutoff check valve assembly includes a ram air fan configured to draw an airflow through a fan inlet, and a ram fan bypass duct positioned downstream of the ram air fan. The ram fan bypass duct includes a valve assembly configured to selectably direct the airflow through the ram air fan when the valve assembly is in an open position, and direct the airflow through a bypass duct thereby bypassing the ram air fan when the valve assembly is in a closed position. 
     Additionally or alternatively, in this or other embodiments the valve assembly includes a support having a plurality of support openings therein in fluid communication with the bypass duct, an inner cage positioned in the support having a plurality of cage openings therein, and a plurality of flappers rotatably secured to the inner cage. The plurality of flappers are movable between the open position covering the plurality of support openings, and the closed position covering the plurality of cage openings. 
     Additionally or alternatively, in this or other embodiments the plurality of flappers are biased to the closed position. 
     Additionally or alternatively, in this or other embodiments each flapper of the plurality of flappers includes a spoiler extending from an outer surface of the flapper over which the airflow from the bypass duct is directed to urge the flapper into the closed position. 
     Additionally or alternatively, in this or other embodiments the inner cage includes a hub, an outer ring, and a plurality of spokes extending from the hub to the outer ring. The plurality of cage openings are formed between adjacent spokes of the plurality of spokes. 
     Additionally or alternatively, in this or other embodiments the plurality of spokes are aerodynamically shaped. 
     Additionally or alternatively, in this or other embodiments the plurality of flaps rotate less than 45 degrees between the open position and the closed position. 
     Additionally or alternatively, in this or other embodiments airflow through the bypass flow and airflow through the ram air fan exit the ram air fan assembly at a common passage exit. 
     In another embodiment, an environmental control system for an aircraft includes a ram air heat exchanger and a ram air fan assembly operably connected to the ram air heat exchanger and configured to urge an airflow across the ram air heat exchanger. The ram air fan assembly includes a ram air fan and a ram fan bypass duct positioned downstream of the ram air fan. The ram fan bypass duct includes a valve assembly configured to selectably direct the airflow through the ram air fan when the valve assembly is in an open position, and direct the airflow through a bypass duct thereby bypassing the ram air fan when the valve assembly is in a closed position. 
     Additionally or alternatively, in this or other embodiments the valve assembly includes a support having a plurality of support openings therein in fluid communication with the bypass duct, an inner cage located in the support having a plurality of cage openings therein, and a plurality of flappers rotatably secured to the inner cage. The plurality of flappers movable between the open position covering the plurality of support openings, and the closed position covering the plurality of cage openings. 
     Additionally or alternatively, in this or other embodiments the plurality of flappers are biased to the closed position. 
     Additionally or alternatively, in this or other embodiments each flapper of the plurality of flappers includes a spoiler extending from an outer surface of the flapper over which the airflow from the bypass duct is directed to urge the flapper into the closed position. 
     Additionally or alternatively, in this or other embodiments the inner cage includes a hub, an outer ring, and a plurality of spokes extending from the hub to the outer ring. The plurality of cage openings are formed between adjacent spokes of the plurality of spokes. 
     Additionally or alternatively, in this or other embodiments the plurality of spokes are aerodynamically shaped. 
     Additionally or alternatively, in this or other embodiments the plurality of flaps rotate less than 45 degrees between the open position and the closed position. 
     In yet another embodiment, a check valve for a ram air fan assembly includes a support having a plurality of support openings therein in fluid communication with the bypass duct, an inner cage positioned in the support having a plurality of cage openings therein, and a plurality of flappers rotatably secured to the inner cage. The plurality of flappers are movable between the open position covering the plurality of support openings, and the closed position covering the plurality of cage openings. 
     Additionally or alternatively, in this or other embodiments the plurality of flappers are biased to the closed position. 
     Additionally or alternatively, in this or other embodiments each flapper of the plurality of flappers includes a spoiler extending from an outer surface of the flapper over which the airflow from a bypass duct is directed to urge the flapper into the closed position. 
     Additionally or alternatively, in this or other embodiments the inner cage includes a hub, an outer ring, and a plurality of spokes extending from the hub to the outer ring, the plurality of cage openings formed between adjacent spokes of the plurality of spokes. 
     Additionally or alternatively, in this or other embodiments the plurality of spokes are aerodynamically shaped. 
    
    
     
       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 schematic view of an embodiment of an environmental control system for an aircraft; 
         FIG. 2  is a first cross-sectional view of an embodiment of a ram air fan and fan bypass/shutoff check valve assembly; 
         FIG. 3  is a second cross-sectional view of an embodiment of a ram air fan and fan bypass/shutoff check valve assembly; 
         FIG. 4  is a partial perspective view of an embodiment of a ram air fan and fan bypass/shutoff check valve assembly; 
         FIG. 5  is a partially exploded view of an embodiment of a ram air fan and fan bypass/shutoff check valve assembly; 
         FIG. 6  is another partial perspective view of an embodiment of a ram air fan and fan bypass/shutoff check valve assembly; 
         FIG. 7  another cross-sectional view of an embodiment of a ram air fan and fan bypass/shutoff check valve assembly; and 
         FIG. 8  is yet another cross-sectional view of an embodiment of a ram air fan and fan bypass/shutoff check valve assembly. 
     
    
    
     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. 
     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. For example, “about” can include a range of ±8% or 5%, or 2% of a given value. 
     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. 
     Referring to  FIG. 1 , a schematic illustration of an environmental control system (ECS)  10  for an aircraft is shown. The ECS  10  includes a ram air heat exchanger  12  and a ram air fan assembly  14  to draw a ram airflow  16  across the ram air heat exchanger  12  to condition a fluid flowing through the ram air heat exchanger  12 . The ram airflow  16  then flows through ram air passage  18 , through the ram air fan assembly  14  and out of a passage exit  20 . 
     Referring to  FIG. 2 , the ram air fan assembly  14  includes a fan housing  22 , in which a ram air fan  24  is located, and is rotatable about a central axis  26 . The fan housing  22  is in flow communication with the ram air duct  28  downstream of the ram air heat exchanger  12 . In the embodiment illustrated, the ram air fan  24  is driven by a tip turbine  30  located in the fan housing  22  radially outboard of the ram air fan  24 . A ram fan bypass duct  32  is located downstream of the fan housing  22  and includes a fan bypass/shutoff check valve consisting of an outer housing  34  and an inner cage  36  located therein. The outer housing  34  includes a support  38  and a plurality of flappers  40  rotationally movable between an opened position shown in  FIG. 2  in which airflow  42  proceeds through the ram air fan  24  and through the passage exit  20 , and a bypass position, shown in  FIG. 3 , in which airflow  42  bypasses the ram air fan  24  and proceeds through a bypass passage  44  in the ram fan bypass duct  32  to the passage exit  20 . 
     Referring now to  FIG. 4 , the support  38  includes a plurality of support openings  46 , the quantity of support openings  46  corresponding to the quantity of flappers  40  in the plurality of flappers  40 . In some embodiments, there are  8  support openings  46  and  8  flappers  40 , but it is to be appreciated that other quantities may be used. When in the opened position, as shown in  FIG. 2  and  FIG. 4 , each flapper  40  engages to the support  38 , closing a respective support opening  46 . In some embodiments, the support openings  46  are recessed into the support  38  such that when the flapper  40  engages the support  38  at the support opening  46  an inner flapper surface is flush with an inner support surface, such that there is a positive seal and a smooth flowpath along the inner support surface, reducing pressure drop along the support  38 . 
     Further, the inner cage  36  includes a plurality of inner cage openings  48 , shown best in the exploded view of  FIG. 5 . In the view of  FIG. 2  and  FIG. 4 , with the flappers  40  in the opened position, the airflow  42  is directed from the ram air fan  24 , through the plurality of inner cage openings  48 , and through the passage exit  20 . When the ram air fan  24  is operating, positive air pressure across the ram air fan  24  forces the flappers  40  into the opened position. 
       FIG. 6  further illustrates the plurality of flappers  40  in a closed position. When in the closed position, the flappers  40  engage the inner cage  36  covering the plurality of inner cage openings  48 . Referring to  FIG. 3 , with the inner cage openings  48  covered, the airflow  42  is diverted through the bypass passage  44  and to the passage exit  20 , bypassing the ram air fan  24 . 
     The flappers  40  are each connected to the support  38  via, for example, a hinge connection  50  at a pivot axis  52 . To move between the open position, illustrated in  FIG. 2  and the closed position illustrated in  FIG. 6 , the flapper  40  is rotated about the pivot axis  52 . In some embodiments, an angle of rotation of the flapper  40  between the open position and closed position is less than 45 degrees. In other embodiments, the angle of rotation is 40 degrees. 
     In some embodiments, the flappers  40  are biased toward the closed position by, for example, a spring or other biasing device (not shown). When the ram air fan  24  is commanded to stop, the flappers  40  move to the closed position due to the lack of positive pressure across the ram air fan  24 , and because of the influence of the biasing device. Further, in some embodiments, as shown in  FIG. 7 , the flapper  40  includes an aerodynamic spoiler  56  extending from an outer surface  58  of the flapper  40 , such that the airflow  42  flowing though the bypass passage  44  flows over the spoiler  56 , exerting aerodynamic forces on the spoiler  56  and urging the flappers  40  into engagement with the inner cage  36  covering the cage openings  48 . In some embodiments, the spoiler  56  extends substantially perpendicularly to a direction of the airflow  42  exiting the bypass passage  44 . 
     Referring again to  FIG. 5  and  FIG. 7 , the inner cage  36  includes a hub  60  located at the central axis  26  and an outer ring  62  coaxial with the hub  60  and defining a radial outwardmost extent of the inner cage  36 . A plurality of spokes  64  extend from the hub  60  to the outer ring  62  defining the cage openings  48  between adjacent spokes  62 . As shown in  FIG. 8 , the spokes  64  each have a cross-sectional shape configured to reduce pressure drop through the cage openings  48 . As shown the spokes  64  may have a tapered V cross-sectional shape, or alternatively another cross-sectional shape, such as an airfoil shape. 
     The ram fan bypass duct  32  including the inner cage  36  and flappers  40  movable between the inner cage  36  and the support  38 , allows airflow  42  to bypass the ram air fan  24  in-flight thus preventing windmilling of the ram air fan  24  and preventing the need to power the ram air fan  24  during flight to provide airflow to an air bearing of the ram air fan  24 . 
     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.