Patent Publication Number: US-8979026-B2

Title: Air compressor backing plate

Description:
BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to air compressors and, in particular, to a backing plate for a cabin air compressor in an aircraft. 
     Current commercial aircraft are routinely equipped with a variety of systems for controlling the temperature, pressure, and other parameters and conditions within the aircraft. For example, an environmental control system (ECS) of the aircraft may include an air compressor, e.g., a cabin air compressor, in order to maintain desired cabin pressure. An air compressor or other component may experience degradation in effectiveness, efficiency, lifespan, or other operating characteristics if operated outside of a preferred range of operating conditions such as may occur in aircraft that are subjected to a wide variety of conditions (e.g., vastly different pressures and temperatures at ground level and cruising altitude). 
     SUMMARY 
     According to one embodiment, a compressor for pressurizing a flow of air within an aircraft is disclosed. The compressor includes an inlet providing the flow of air to the compressor. An outlet provides the flow of air, after pressurization by the compressor, to a chamber of the aircraft. A diffuser assembly is disposed between the inlet and the outlet. The diffuser assembly includes one or more vanes at least partially impeding the flow of air through the diffuser assembly. A backing plate is included having a surface adjacent to the one or more vanes. The surface includes a relief feature that enables air to bypass the one or more vanes. 
     According to another embodiment, a method of operating a compressor in an aircraft is disclosed. The method includes pressurizing air with the compressor as the air travels from an inlet to an outlet and through a diffuser assembly disposed between the inlet and the outlet. Pressurized air is provided to a chamber of the aircraft via the outlet. A portion of air bypasses the one or more vanes of the diffuser assembly via a relief feature formed in a surface of a backing plate of the diffuser assembly adjacent to the one or more vanes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  schematically illustrates an aircraft having an environmental control system; 
         FIG. 2  is a cross-sectional view of an air compressor of the environmental control system of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of a backing plate of the air compressor of  FIG. 2 ; 
         FIG. 4  is a perspective view of a surface of the backing plate of  FIG. 3  having a relief feature formed therein; and 
         FIG. 5  is an enlarged view of the area of the backing plate encircled in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein with reference to the Figures by way of exemplification and not limitation. 
       FIG. 1  schematically illustrates an aircraft  10 . The aircraft  10  has various chambers, including a cabin  12 , in which conditions related to the environment of the chamber, such as temperature, pressure, etc. are controlled. Other chambers may include or be defined by a galley, cargo area, etc. In the illustrated embodiment, an ECS  14  is included to control the environment (e.g., temperature, pressure, etc.) of the cabin  12  and/or other chambers of the aircraft. The ECS  14  can be arranged to receive, monitor, and/or condition ram air, ambient outside air, air recycled from the cabin  12  or other chambers of the aircraft  10 , bleed air from turbines or other components of the aircraft  10 , etc., or a combination thereof. In the illustrated embodiment, the ECS  14  includes an air compressor  16  for assisting in the maintenance of a desired air pressure within the cabin  12 , i.e., cabin pressure. In this way, the air compressor  16  may be referred to as a cabin air compressor (CAC), although it is to be understood that other compressors may benefit from the embodiments disclosed herein. 
     The air compressor  16  is shown in more detail in  FIG. 2 . The compressor  16  includes a rotor or impeller  18  that is driven by a motor  20 . The impeller  18  includes one or more blades  22  for directing a flow of air through the compressor  16  while the impeller  18  is rotated by the motor  20 . The flow of air is generally represented by arrows in  FIG. 2  designated with the numeral  24 . It is noted that the arrows  24  are only indicated on one half of the compressor  16  for better clarity of the components of the compressor  16 , but that the flow of air occurs as indicated about the entire circumference of the impeller  18 . 
     The impeller  18  and the motor  20  are contained within a housing  25 , which may be constructed from multiple housing portions secured to one another. The housing  25  has an inlet  26  for providing air to the compressor  16 . Air drawn through the inlet  26  is pumped radially outwardly to an outlet  28  by the blades  22 , as indicated by the arrows  24 . Before reaching the outlet  28 , the air is passed through a diffuser assembly  30 , as also indicated. 
     The diffuser assembly  30  includes a backing plate  32  supported by the housing  25 , e.g., via a mounting plate  34 . A shroud  36  is supported by the housing  25  on the side of the backing plate  32  opposite to the mounting plate  34 . The flow of air as indicated by the arrows  24  is directed by the impeller  18  through the space between the backing plate  32  and the shroud  36 . A plurality of vanes  38  are retained in this space between the backing plate  32  and the shroud  36  in order to impede the flow of air as it passes through the compressor  16 . The vanes  38  can be arranged to exhibit some degree of movement relative to the backing plate  32  in order to vary a flow area through the diffuser assembly  30 . In the illustrated embodiment, the vanes  38  are arranged to oscillate or pivot about a set of pins, bolts, or fasteners  40 , e.g., between an open position in which the flow of air is relatively unimpeded and a partial open position in which the flow of air is relatively impeded and slowed. The fasteners  40  extend through the backing plate  32  between the mounting plate  34  and the shroud  36 . 
     The backing plate  32  is shown in without the other components of the air compressor  16  in  FIGS. 3-5 . The backing plate  32  includes bores or openings  42 , for receiving corresponding ones of the fasteners  40 . A surface  44  of the backing plate  32  is adjacent to the vanes  38  and at least partially defines the flow path taken by the flow of air through the diffuser assembly  30 . A relief feature  46  is provided in the surface  44  of the backing plate  32  that enables a portion of the air in the diffuser assembly  30  to bypass the vanes  38 . The bypass provided by the relief feature  46  is generally represented by an arrow designated with the numeral  48  in  FIG. 2 . Similar to the arrows  24 , only one of the arrows  48  is illustrated for clarity, but it is to be appreciated that the bypass of air will be provided by the relief feature  46  for each of the vanes  38 . It has been found that the bypass of air provided by the relief feature  46  advantageously improves operation of the compressor  16 . For example, one benefit obtainable by use of the relief feature  46  in the surface  44  of the backing plate  32  is an increase in the surge margin of the compressor  16  under some operating conditions of the compressor  16 . Improved surge margin translates to a corresponding increase in the overall operating range of the compressor  16 , which may improve the lifespan, efficiency, and/or effectiveness of the compressor  16  while maintaining a desired pressure within a chamber of the aircraft  10 , such as the cabin  12 . 
     The relief feature  46  is created in one embodiment by machining or cutting a groove or recess into the surface  44  of the backing plate  32 . In one embodiment, the backing plate  32  is formed with the relief feature  46 , e.g., via a die or mold. The backing plate  32  includes a hub portion  50  and a flange portion  52 , which may similarly be formed via machining, or via a die or mold, or some other manufacturing process before, during, or after creation of the relief feature  46 . The backing plate  32  in embodiments other than that illustrated may also be formed of an essentially constant thickness, e.g., not having both the hub portion  50  and the flange portion  52 , or take some other size or shape than that shown. 
     It is noted that the amount of air bypassing the vanes  38  via the relief feature  46  can be relatively small in comparison to the total volumetric flow of air passing through the diffuser assembly  30  and still advantageously improve the performance of the compressor  16  as noted above. For example, a set of dimensions for the relief feature  46  according to one embodiment can be appreciated in view of  FIG. 5 . In the embodiment of  FIG. 5 , a diameter D1 defines the radial bounds of the relief feature  46  with respect to the axis or center of the backing plate  32 , while a dimension D2 denotes the axial depth of the relief feature  46 , i.e., the amount that the relief feature  46  is recessed into the surface  44 . The relief feature  46  may be abruptly formed in the surface  44  or gradually transition via a ramp or chamfer, as indicated along a distance D3. 
     In one embodiment, the depth D2 is between about 0.5% and 5% of a thickness D4 of the flange portion  52  of the backing plate  32 , and more particularly, about 1.5% to 2.5% of the thickness D4. This corresponds to about 0.5% to 2.5%, or more particularly about 0.75% to 1.5%, of a width D5 of the flow path through the diffuser assembly  30  as shown in  FIG. 2  and measured axially between the surface  44  of the backing plate  32  and the shroud  36 . In one specific embodiment, the depth D2 is about 0.004 inches (approximately 0.10 mm), the thickness D4 is about 0.2 inches (approximately 5.08 mm), and the width D5 is between about 0.3 inches (approximately 7.62 mm) and 0.5 inches (approximately 12.7 mm). It is also noted that in the illustrated embodiment, the relief feature  46  is formed entirely within the radial extents of the hub portion  50 , but in other embodiments the dimension D1 of the relief feature  46  can be enlarged to extend radially into the flange portion  52 . 
     While the invention 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 invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.