Patent Publication Number: US-9890793-B2

Title: Variable diffuser vane

Description:
BACKGROUND 
     The present disclosure relates to aircraft environmental control systems. More specifically, the present disclosure relates to a vane for a variable diffuser in a cabin air compressor. 
     Air cycle machines are used in environmental control systems in aircraft to condition air for delivery to an aircraft cabin. Conditioned air is air at a temperature, pressure, and humidity desirable for aircraft passenger comfort and safety. At or near ground level, the ambient air temperature and/or humidity is often sufficiently high that the air must be cooled as part of the conditioning process before being delivered to the aircraft cabin. At flight altitude, ambient air is often far cooler than desired, but at such a low pressure that it must be compressed to an acceptable pressure as part of the conditioning process. Compressing ambient air at flight altitude heats the resulting pressured air sufficiently that it must be cooled, even if the ambient air temperature is very low. Thus, under most conditions, heat must be removed from air by the air cycle machine before the air is delivered to the aircraft cabin. 
     A cabin air compressor can be used to compress air for use in an environmental control system. The cabin air compressor includes a motor to drive a compressor section that in turn compresses air flowing through the cabin air compressor. A variable diffuser is also positioned in the cabin air compressor. The variable diffuser has a plurality of vanes that are configured to pivot about a point in order to vary the size of a gap between adjacent vanes to vary the flow of air through the variable diffuser. The plurality of vanes on the variable diffuser are held between a shroud and a backing plate. A small clearance is typically provided between the shroud and the vanes and between the shroud and the backing plate, which can cause the vanes to float freely. Under unstable airflow conditions, the vanes may dither, vibrate, or resonate if they are floating freely. This can lead to significant wear between the vanes and the shroud and between the vanes and the backing plate and can also cause failure of the vanes. 
     SUMMARY 
     A vane for a variable diffuser includes a body with an inlet end and an outlet end, a leading surface extending from the inlet end to the outlet end, a trailing surface opposite the leading surface and extending from the inlet end to the outlet end, a first surface extending from the inlet end to the outlet end, and a second surface opposite the first surface and extending from the inlet end to the outlet end. The vane further includes a first cavity on the first surface of the vane adjacent the inlet end, a second cavity on the first surface of the vane adjacent the outlet end, a third cavity on the second surface of the vane adjacent the inlet end, and a fourth cavity on the second surface of the vane adjacent the outlet end. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is cross-sectional view of an air compressor. 
         FIG. 2  is a perspective cut-away view of a variable diffuser. 
         FIG. 3A  is a front plan view of a vane from the variable diffuser. 
         FIG. 3B  is a back plan view of the vane seen in  FIG. 3A . 
         FIG. 3C  is a cross-sectional view of the vane seen in  FIG. 3A , taken along line  3 C- 3 C of  FIG. 3A . 
         FIG. 4A  is a cross-sectional view of a prior art vane between a shroud and a backing plate in the variable diffuser. 
         FIG. 4B  is a cross-sectional view of the vane according to the present disclosure between a shroud and a backing plate in the variable diffuser. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is cross-sectional view of air compressor  10 . Air compressor  10  includes motor  12 , compressor section  14 , variable diffuser  16 , and tie rod  18 . Also shown in  FIG. 1  is axis A. Motor  12  drives compressor section  14  in air compressor  10 . Air will enter into compressor section  14  and then flow through variable diffuser  16  before exiting compressor section  14 . Tie rod  18  extends through air compressor  10  and is centered on axis A. Motor  12  and compressor section  14  are mounted to tie rod  18 . Motor  12  will drive tie rod  18  and cause it to rotate, which in turn will rotate compressor section  14 . 
     Motor  12  includes motor housing  20 , motor rotor  22 , and motor stator  24 . Motor housing  20  surrounds motor rotor  22  and motor stator  24 . Motor  12  is an electric motor with motor rotor  22  disposed within motor stator  24 . Motor rotor  22  is rotatable about axis A. Motor rotor  12  is mounted to tie rod  18  to drive rotation of tie rod  18  in air compressor  10 . 
     Compressor section  14  includes compressor housing  30 , compressor inlet  32 , compressor outlet  34 , and compressor rotor  36 . Compressor housing  30  includes a duct that forms compressor inlet  32  and a duct that forms compressor outlet  34 . Compressor inlet  32  draws air into compressor section  14 . Positioned in compressor housing  30  is compressor rotor  36 . Compressor rotor  36  is driven with motor  12  and is mounted on tie rod  18  to rotate with tie rod  18  about axis A. Air that is drawn into compressor section  14  through compressor inlet  32  is compressed with compressor rotor  36 . The compressor air is then routed through variable diffuser  16  before exiting compressor section  14  through compressor outlet  34 . 
     Variable diffuser  16  includes shroud  40 , vanes  42 , backing plate  44 , mounting plate  46 , fasteners  48 , pivot pins  50 , drive ring  52 , drive pins  54 , and diffuser actuator  56 . Shroud  40  of variable diffuser  16  can be attached to compressor housing  30 . Vanes  42  are positioned between shroud  40  and backing plate  44 . Backing plate  44  is held against vanes  42  with mounting plate  46 . Fasteners  48  extend through openings in mounting plate  46 , backing plate  44 , vanes  42 , and shroud  40 . Vanes  42  are positioned between shroud  40  and backing plate  44  so that there is a small clearance between vanes  42  and shroud  40  and between vanes  42  and backing plate  44 . 
     Pivot pins  50  extend between openings in vanes  42  and openings in shroud  40 . Vanes  42  can rotate about pivot pins  50 . Drive ring  52  is positioned adjacent shroud  40 . Drive pins  54  extend from drive ring  52  through shroud  40  into a slot in vanes  42 . Drive ring  52  can be rotated about axis A with diffuser actuator  56 . As drive ring  52  is rotated, drive pins  54  engaged in the slots in vanes  42  will drag vanes  42  and cause them to rotate about pivot pins  50 . This movement of vanes  42  will vary the gap between adjacent vanes  42  to vary the amount of air flowing between vanes  42 . 
     Varying the amount of air that flows between vanes  42  allows variable diffuser  16  to be used in different settings. First, when an aircraft is positioned on the ground the air that is taken into variable diffuser  16  is typically at a pressure that is suitable for use in the cabin. Vanes  42  can thus be positioned to allow air to flow through variable diffuser  16  without compressing the air. Alternatively, when an aircraft is in flight the air that is taken into variable diffuser  16  is typically at a low pressure that is unsuitable for use in the cabin. Vanes  42  can thus be positioned to compress the air flowing through variable diffuser  16  before that air is routed to an environmental control system. 
       FIG. 2  is a perspective cut-away view of variable diffuser  16 . Variable diffuser  16  includes shroud  40 , vanes  42 , fasteners  48 , pivot pins  50 , drive ring  52 , and drive pins  54 . Each vane  42  includes inlet end  60 , outlet end  62 , first surface  64 , second surface  66 , leading surface  68 , trailing surface  70 , first aperture  80 , second aperture  82 , third aperture  84 , first recess  86 , second recess  88 , slot  90 , first cavity  100 , second cavity  102 , third cavity  104  (not shown in  FIG. 2 ), fourth cavity  106  (not shown in  FIG. 2 ), first notch  110 , second notch  112 , third notch  114  (not shown in  FIG. 2 ), and fourth notch  116  (not shown in  FIG. 2 ). 
     Variable diffuser  16  includes vanes  42  positioned on shroud  40 . Fasteners  48  extend through a mounting plate (now shown in  FIG. 2 ), a backing plate (not shown in  FIG. 2 ), vanes  42 , and shroud  40  to hold vanes  42  between the backing plate and shroud  40 . Pivot pins  50  extend through vanes  42  and shroud  40  so that vanes  42  can pivot about pivot pins  50 . Drive ring  52  is positioned adjacent shroud  40  and has a retaining ring that extends up to be flush with the surface of shroud  40  that abuts vanes  42 . Drive pins  54  extend from drive ring  52  into vanes  42  to engage vanes  42 . Drive ring  52  can be rotated, causing drive pins  54  to rotate vanes  42 . 
     Vanes  42  are pivotally positioned in variable diffuser  16 . Each vane  42  includes inlet end  60  positioned radially inward in relation to variable diffuser  16  and outlet end  62  positioned radially outward in relation to variable diffuser  16 . Each vane  42  also includes first surface  64  and second surface  66  extending from inlet end  60  to outlet end  62 . First surface  64  abuts the backing plate (now shown in  FIG. 2 ) and second surface  64  abuts shroud  40 . Each vane  42  also includes leading surface  68  and trailing surface  70  extending from inlet end  60  to outlet end  62 . Leading surface  68  faces radially inward in relation to variable diffuser  16  and trailing surface  70  faces radially outward in relation to variable diffuser  16 . 
     Each vane  42  includes first aperture  80  and second aperture  82  extending from first surface  64  to second surface  66 . First aperture  80  receives one fastener  48  and second aperture  82  receives one fastener  48 . First aperture  80  and second aperture  82  are sized so that first aperture  80  and second aperture  82  do not limit the movement of vane  42  when it pivots. A number of stand-offs can also be positioned in first aperture  80  and second aperture  82 . The stand-offs are attached to shroud  40  and extend a slight distance over vanes  42  so that the backing plate does not rest on vanes  42 . This allows for a small clearance between vanes  42  and shroud  40  and between vanes  42  and the backing plate. 
     Each vane  42  also includes third aperture  84  extending from first surface  64  to second surface  66 . Third aperture  84  is sized to receive pivot pin  50 . Vanes  42  pivot on pivot pins  50 . Each vane  42  further includes first recess  86 , second recess  88 , and slot  90 . First recess  86  is positioned on first surface  64  of vane  42 . Second recess  88  is positioned on second surface  66  of vane  42 . Second recess  88  is positioned around slot  90 . Slot  90  extends a distance into vane  42  from second surface  66 . Slot  90  is sized to slidably engage drive pin  54 . As drive ring  52  rotates, drive pins  54  can slide through slots  90  to rotate vanes  42  about pivot pins  50 . 
     Each vane  42  further includes first cavity  100 , second cavity  102 , third cavity  104 , and fourth cavity  106 . First cavity  100  and second cavity  102  are positioned on first surface  64 . Third cavity  104  and fourth cavity  106  are positioned on second surface  66 . Third cavity  104  and fourth cavity  106  are not shown in  FIG. 2 , as third cavity  104  is positioned below first cavity  100  on second surface  66  facing shroud  40  and fourth cavity  106  is positioned below second cavity  102  on second surface  66  facing shroud  40 . Vane  42  further includes first notch  110 , second notch  112 , third notch  114 , and fourth notch  116 . First notch  110  in on first surface  64  and extends from leading surface  68  to first cavity  100 . Second notch  112  is on first surface  64  and extends from leading surface  68  to second cavity  102 . Third notch  114  is on second surface  66  and extends from trailing surface  70  to third cavity  104 . Fourth notch  116  is on second surface  66  and extends from trailing surface  70  to fourth cavity  106 . Third notch  114  and fourth notch  116  are not shown in  FIG. 2 , as they are positioned on second surface  66  facing shroud  40 . 
     First cavity  110 , second cavity  112 , third cavity  114 , and fourth cavity  116  are included on vane  42  to load vane  42  against the backing plate (now shown in  FIG. 2 ) to prevent vanes  42  from dithering, vibrating, and resonating. First notch  110 , second notch  112 , third notch  114 , and fourth notch  116  are included on vane  42  to vent first cavity  100 , second cavity  102 , third cavity  104 , and fourth cavity  106 , respectively. This allows air that is flowing through variable diffuser  16  to flow into first cavity  100 , second cavity  102 , third cavity  104 , and fourth cavity  106  through first notch  110 , second notch  112 , third notch  114 , and fourth notch  116 , respectively. First cavity  100 , second cavity  102 , third cavity  104 , and fourth cavity  106  are vented to different pressures to create the load that holds vane  42  against the backing plate. 
       FIG. 3A  is a front plan view of vane  42  from variable diffuser  16 .  FIG. 3B  is a back plan view of vane  42  seen in  FIG. 3A .  FIG. 3C  is a cross-sectional view of vane  42  seen in  FIG. 3A , taken along line  3 C- 3 C of  FIG. 3A . Vane  42  includes inlet end  60 , outlet end  62 , first surface  64 , second surface  66 , leading surface  68 , trailing surface  70 , first aperture  80 , second aperture  82 , third aperture  84 , first recess  86 , second recess  88 , slot  90 , first cavity  100 , second cavity  102 , third cavity  104 , fourth cavity  106 , first notch  110 , second notch  112 , third notch  114 , and fourth notch  116 . 
     Vane  42  includes inlet end  60  and outlet end  62 . Vane  42  also includes first surface  64  and second surface  66  on opposite sides of vane  42  and extending from inlet end  60  to outlet end  62 . Vane  42  also includes leading surface  68  and trailing surface  70  on opposite sides of vane  42  and extending from inlet end  60  to outlet end  62 . Vane  42  further includes first aperture  80 , second aperture  82 , and third aperture  84 . First aperture  80 , second aperture  82 , and third aperture  84  all extend through vane  42  from first surface  64  to second surface  66 . Vane  42  further includes first recess  86 , second recess  88 , and slot  90 . First recess  86  is positioned on first surface  64  of vane  42 . Second recess  88  is positioned on second surface  66  of vane  42 . Second recess  88  is positioned around slot  90 . Slot  90  extends a distance into vane  42  from second surface  66 . 
     Vane  42  includes first cavity  100 , second cavity  102 , third cavity  104 , and fourth cavity  106 . First cavity  100  and second cavity  102  are positioned on first surface  64 . Third cavity  104  and fourth cavity  106  are positioned on second surface  66 . First cavity  100 , second cavity  102 , third cavity  104 , and fourth cavity  106  all have a triangular shape. Vane  42  further includes first notch  110 , second notch  112 , third notch  114 , and fourth notch  116 . First notch  110  in on first surface  64  and extends from leading surface  68  to first cavity  100 . Second notch  112  is on first surface  64  and extends from leading surface  68  to second cavity  102 . Third notch  114  is on second surface  66  and extends from trailing surface  70  to third cavity  104 . Fourth notch  116  is on second surface  66  and extends from trailing surface  70  to fourth cavity  106 . 
     Vane  42  has distance D 1  between first surface  64  and second surface  66 . Distance D 1  is between 0.345 inches and 0.347 inches. First cavity  100  of vane  42  is positioned between inlet end  60  of vane  42  and third aperture  84 . First cavity  100  has a first edge that is distance D 2  away from a center of third aperture  84 . Distance D 2  is between 0.196 inches and 0.216 inches. First cavity  100  has a second edge that is distance D 3  away from a center of third aperture  84 . Distance D 3  is between 1.347 inches and 1.367 inches. First cavity  100  extends distance D 4  into vane  42 . Distance D 4  is between 0.030 inches and 0.050 inches. First notch  110  is positioned near the second edge of first cavity  100  adjacent inlet end  60  of vane  42 . Distance D 5  is the distance between a first edge of first notch  110  and a second edge of first notch  110 . Distance D 5  is between 0.178 inches and 0.198 inches. 
     Second cavity  102  of vane  42  is positioned between outlet end  62  of vane  42  and first recess  86 . Second cavity  102  has a first edge that is distance D 6  away from a center of third aperture  84 . Distance D 6  is between 2.630 inches and 2.650 inches. Second cavity  102  extends distance D 7  into vane  42 . Distance D 7  is between 0.090 inches and 0.110 inches. Second notch  112  is positioned near the first edge of second cavity  102  adjacent first recess  86 . Distance D 5  is the distance between a first edge of second notch  112  and a second edge of second notch  112 . Distance D 5  is between 0.178 inches and 0.198 inches. 
     Third cavity  104  of vane  42  is positioned between inlet end  60  of vane  42  and third aperture  84 . Third cavity  104  has a first edge that is distance D 2  away from a center of third aperture  84 . Distance D 2  is between 0.196 inches and 0.216 inches. Third cavity  104  has a second edge that is distance D 3  away from a center of third aperture  84 . Distance D 3  is between 1.347 inches and 1.367 inches. Third cavity  104  extends distance D 4  into vane  42 . Distance D 4  is between 0.030 inches and 0.050 inches. Third notch  114  is positioned near the first edge of third cavity  104  adjacent third aperture  84 . Distance D 5  is the distance between a first edge of third notch  114  and a second edge of third notch  114 . Distance D 5  is between 0.178 inches and 0.198 inches. 
     Fourth cavity  106  of vane  42  is positioned between outlet end  62  of vane  42  and second recess  88 . Fourth cavity  106  has a first edge that is distance D 6  away from a center of third aperture  84 . Distance D 6  is between 2.630 inches and 2.650 inches. Fourth cavity  106  extends distance D 7  into vane  42 . Distance D 7  is between 0.090 inches and 0.110 inches. Fourth notch  116  is positioned near the first edge of fourth cavity  116  adjacent second recess  88 . Distance D 5  is the distance between a first edge of fourth notch  116  and a second edge of fourth notch  116 . Distance D 5  is between 0.178 inches and 0.198 inches. 
     Vane  42  also includes distance D 8 . Distance D 8  is the distance between leading surface  68  and a first side of first cavity  100 ; the distance between trailing surface  70  and a second side of first cavity  100 ; the distance between leading surface  68  and a first side of second cavity  102 ; the distance between trailing surface  70  and a second side of second cavity  102 ; the distance between trailing surface  70  and a first side of third cavity  104 ; the distance between leading surface  68  and a second side of third cavity  104 ; the distance between trailing surface  70  and a first side of fourth cavity  106 ; and the distance between leading surface  68  and a second side of fourth cavity  106 . Distance D 8  is between 0.060 inches and 0.080 inches. 
     Table 1 below is a list of different ratios of distances D 1 -D 8 . 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 A list of ratios of distances D1-D8. 
               
            
           
           
               
               
               
            
               
                 Ratio 
                 Minimum 
                 Maximum 
               
               
                   
               
            
           
           
               
               
               
            
               
                 D1/D2 
                 1.597 
                 1.770 
               
               
                 D1/D3 
                 0.252 
                 0.258 
               
               
                 D1/D4 
                 6.900 
                 11.567 
               
               
                 D1/D5 
                 1.742 
                 1.949 
               
               
                 D1/D6 
                 0.130 
                 0.132 
               
               
                 D1/D7 
                 3.136 
                 3.856 
               
               
                 D1/D8 
                 4.313 
                 5.783 
               
               
                 D2/D3 
                 0.143 
                 0.160 
               
               
                 D2/D8 
                 2.450 
                 3.600 
               
               
                 D3/D5 
                 6.803 
                 7.680 
               
               
                 D3/D8 
                 16.838 
                 22.783 
               
               
                 D6/D8 
                 32.875 
                 44.167 
               
               
                   
               
            
           
         
       
     
       FIG. 4A  is a cross-sectional view of prior art vane  42 ′ between shroud  40 ′ and backing plate  44 ′ in variable diffuser  16 ′. Variable diffuser  16 ′ includes shroud  40 ′, vane  42 ′, backing plate  44 ′, and pivot pin  50 ′. Vane  42 ′ includes inlet end  60 ′, outlet end  62 ′, first surface  64 ′, second surface  66 ′, first cavity  120 ′, second cavity  122 ′, and aperture  124 ′. 
     Shroud  40 ′ has milled portion  40   a ′ that is manufactured with a milling process and turned portion  40   b ′ that is manufactured with a turning process. There is a small step between milled portion  40   a ′ and turned portion  40   b ′ of shroud  40 ′ due to the different manufacturing processes. Vane  42 ′ is positioned between shroud  40 ′ and backing plate  44 ′ with a small clearance between vane  42 ′ and shroud  40 ′ and between vane  42 ′ and backing plate  44 ′. Pivot pin  50 ′ extends from shroud  40 ′ through vane  42 ′ so that vane  42 ′ can pivot about pivot pin  50 ′. 
     Vane  42 ′ includes inlet end  60 ′ and outlet end  62 ′. Air flowing through variable diffuser  16 ′ will flow across vane  42 ′ from inlet end  60 ′ to outlet end  62 ′. Vane  42 ′ also includes first surface  64 ′ that abuts backing plate  44 ′ and second surface  66 ′ that abuts shroud  40 ′. Prior art vane  42 ′ includes first cavity  120 ′, second cavity  122 ′, and aperture  124 ′. First cavity  120 ′ and second cavity  122 ′ are positioned adjacent to inlet end  60 ′. First cavity  120 ′ is on first surface  64 ′ and second cavity  122 ′ is on second surface  66 ′. Aperture  124 ′ is positioned adjacent to outlet end  62 ′ and extends from first surface  64 ′ to second surface  66 ′. 
     As air flows through variable diffuser  16 ′ and across vane  42 ′, air will flow into first cavity  120 ′ and second cavity  122 ′. First cavity  120 ′ and second cavity  122 ′ each have a notch that extends from a side surface of vane  42 ′ into first cavity  120 ′ or second cavity  122 ′ to vent first cavity  120 ′ and second cavity  122 ′. First cavity  120 ′ and second cavity  122 ′ can be vented to different pressures to create a load on vane  42 ′. First cavity  120 ′ with have a high pressure and second cavity  122 ′ will have a low pressure. This difference in pressure will create a load that holds vane  42 ′ against shroud  40 ′. Loading vane  42 ′ against shroud  40 ′ will prevent vane  42 ′ from free floating, and in turn dithering, vibrating, and resonating, between shroud  40 ′ and backing plate  44 ′. 
     One problem present with prior art vane  42 ′ is that the difference in pressure between first cavity  120 ′ and second cavity  122 ′ will create a overturning moment that will cause vane  42 ′ to tilt between shroud  40 ′ and backing plate  44 ′. Aperture  124 ′ at the opposite end of vane  42 ′ will not put a load on vane  42 ′, as air will not gather and create a pressure in aperture  124 ′. As vane  42 ′ tilts due to the overturning moment, a first tip of vane  42 ′ adjacent inlet end  60 ′ will come into contact with shroud  40 ′ and create a point load on shroud  40 ′. Additionally, a second tip of vane  42 ′ adjacent outlet end  62 ′ will come into contact with backing plate  44 ′ and create a point load at backing plate  44 ′. The point loads on shroud  40 ′ and backing plate  44 ′ will cause significant wear between vane  42 ′ and shroud  40 ′ and between vane  42 ′ and backing plate  44 ′. Further, the tilt created on vane  42 ′ will cause vane  42 ′ to be more susceptible to dithering, vibrating, and resonating in unstable flow conditions. This can wear vane  42 ′ and cause vane  42 ′ to fail. 
       FIG. 4B  is a cross-sectional view of vane  42  according to the present disclosure between shroud  40  and backing plate  44  in variable diffuser  16 . Variable diffuser  16  includes shroud  40 , vane  42 , backing plate  44 , and pivot pin  50 . Vane  42  includes inlet end  60 , outlet end  62 , first surface  64 , second surface  66 , first cavity  100 , second cavity  102 , third cavity  104 , and fourth cavity  106 . 
     Shroud  40  has milled portion  40   a  that is manufactured with a milling process and turned portion  40   b  that is manufactured with a turning process. There is a small step between milled portion  40   a  and turned portion  40   b  of shroud  40  due to the different manufacturing processes. Vane  42  is positioned between shroud  40  and backing plate  44  with a small clearance between vane  42  and shroud  40  and between vane  42  and backing plate  44 . Pivot pin  50  extends from shroud  40  through vane  42  so that vane  42  can pivot around pivot pin  50 . 
     Vane  42  includes inlet end  60  and outlet end  62 . Air flowing through variable diffuser  16  will flow across vane  42  from inlet end  60  to outlet end  62 . Vane  42  also includes first surface  64  that abuts backing plate  44  and second surface  66  that abuts shroud  40 . Vane  42  according to the present disclosure includes first cavity  100 , second cavity  102 , third cavity  104 , and fourth cavity  106 . First cavity  100  and third cavity  104  are positioned adjacent to inlet end  60 . First cavity  100  is on first surface  64  and third cavity  104  is on second surface  66 . Second cavity  102  and fourth cavity  106  are positioned adjacent to outlet end  62 . Second cavity  102  is on first surface  64  and fourth cavity  106  is on second surface  66 . 
     As air flows through variable diffuser  16  and across vane  42 , air will flow into first cavity  100 , second cavity  102 , third cavity  104 , and fourth cavity  106 . First cavity  100 , second cavity  102 , third cavity  104 , and fourth cavity  106  each have a notch that extends from a side surface of vane  42  into first cavity  100 , second cavity  102 , third cavity  104 , and fourth cavity  106  to vent each of first cavity  100 , second cavity  102 , third cavity  104 , and fourth cavity  106 . First cavity  100 , second cavity  102 , third cavity  104 , and fourth cavity  106  can all be vented to different pressures to create a load on vane  42 . First cavity  100  and second cavity  102  will have a low pressure and third cavity  104  and fourth cavity  106  will have a high pressure. This difference in pressure will create a load that holds vane  42  against backing plate  44 . Loading vane  42  against backing plate  44  will prevent vane  42  from free floating, and in turn dithering, vibrating, and resonating, between shroud  40  and backing plate  44 . 
     Vane  42  according to the present disclosure is advantageous over prior art vanes. Vane  42  loads against backing plate  44 . Backing plate  44  is a flat surface compared to shroud  40  that has a step between milled surface  40   a  and turned surface  40   b . Loading vane  42  against the flat surface of backing plate  44  is advantageous, as it allows vane  42  to abut backing plate  44  across the entirety of first surface  64  of vane  42 . In alternate embodiments, vane  42  can also be designed to be loaded against shroud  40  if shroud  40  was manufactured as a flat surface without the step between milled surface  40   a  and turned surface  40   b.    
     Further, providing second cavity  102  and fourth cavity  106  helps to balance the load put on vane  42 . Second cavity  102  and fourth cavity  106  can gather air and create a pressure in each of second cavity  102  and fourth cavity  106  adjacent outlet end  62  of vane  42 . The pressures in second cavity  102  and fourth cavity  106  will balance the pressures in first cavity  100  and third cavity  104  to create a uniform load across vane  42 . This prevent vanes  42  from tilting between shroud  40  and backing plate  44 , as the overturning moment is eliminated with the addition of second cavity  102  and fourth cavity  106 . Further, the uniform load on vane  42  will distribute forces from vane  42  against backing plate  44  and decrease point loading between vane  42  and backing plate  44 . This will prevent vane  42  from wearing on backing plate  44 , allowing both parts to maintain structural integrity for a longer period of time before having to be replaced. 
     Discussion of Possible Embodiments 
     The following are non-exclusive descriptions of possible embodiments of the present invention. 
     A vane for a variable diffuser includes a body with an inlet end and an outlet end, a leading surface extending from the inlet end to the outlet end, a trailing surface opposite the leading surface and extending from the inlet end to the outlet end, a first surface extending from the inlet end to the outlet end, and a second surface opposite the first surface and extending from the inlet end to the outlet end. The vane further includes a first cavity on the first surface of the vane adjacent the inlet end, a second cavity on the first surface of the vane adjacent the outlet end, a third cavity on the second surface of the vane adjacent the inlet end, and a fourth cavity on the second surface of the vane adjacent the outlet end. 
     The vane of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components: 
     The vane further includes a first notch in the first surface extending from the leading surface to the first cavity, a second notch in the first surface extending from the leading surface to the second cavity, a third notch in the second surface extending from the trailing surface to the third cavity, and a fourth notch in the second surface extending from the trailing surface to the fourth cavity. 
     A ratio of a distance from the first surface to the second surface of the vane and a distance from a first edge to a second edge of the first notch is between 1.742 and 1.949. 
     A ratio of a distance from the first surface to the second surface of the vane and a distance from a first edge to a second edge of the second notch is between 1.742 and 1.949. 
     A ratio of a distance from the first surface to the second surface of the vane and a distance from a first edge to a second edge of the third notch is between 1.742 and 1.949. 
     A ratio of a distance from the first surface to the second surface of the vane and a distance from a first edge to a second edge of the fourth notch is between 1.742 and 1.949. 
     A ratio of a distance from the first surface to the second surface of the vane and a distance from the first surface to a surface of the first cavity is between 6.900 and 11.567. 
     A ratio of a distance from the first surface to the second surface of the vane and a distance from the second surface to a surface of the third cavity is between 6.900 and 11.567. 
     A ratio of a distance from the first surface to the second surface of the vane and a distance from the first surface to a surface of the second cavity is between 3.136 and 3.856. 
     A ratio of a distance from the first surface to the second surface of the vane and a distance from the second surface to a surface of the fourth cavity is between 3.136 and 3.856. 
     The vane further includes an aperture in the body upon which the vane pivots, wherein the aperture extends from the first surface to the second surface, and wherein the aperture is positioned between the inlet end and the outlet end. 
     A ratio of a distance from the center of the aperture to a first end of the first cavity and a distance from the leading surface to a first side of the first cavity is between 2.450 and 3.600. 
     A ratio of a distance from the center of the aperture to a first end of the first cavity and a distance from the trailing surface to a second side of the first cavity is between 2.450 and 3.600. 
     A ratio of a distance from the center of the aperture to a first end of the third cavity and a distance from the leading surface to a first side of the third cavity is between 2.450 and 3.600. 
     A ratio of a distance from the center of the aperture to a first end of the third cavity and a distance from the trailing surface to a second side of the third cavity is between 2.450 and 3.600. 
     A ratio of a distance from the center of the aperture to a first end of the second cavity and a distance from the leading surface to a first side of the second cavity is between 32.875 and 44.167. 
     A ratio of a distance from the center of the aperture to a first end of the second cavity and a distance from the trailing surface to a second side of the second cavity is between 32.875 and 44.167. 
     A ratio of a distance from the center of the aperture to a first end of the fourth cavity and a distance from the leading surface to a first side of the fourth cavity is between 32.875 and 44.167. 
     A ratio of a distance from the center of the aperture to a first end of the fourth cavity and a distance from the trailing surface to a second side of the fourth cavity is between 32.875 and 44.167. 
     A ratio of a distance between from the first surface to the second surface of the vane and a distance from the center of the aperture to a first end of the first cavity is between 1.597 and 1.770. 
     A ratio of a distance between from the first surface to the second surface of the vane and a distance from the center of the aperture to a first end of the third cavity is between 1.597 and 1.770. 
     A ratio of a distance between from the first surface to the second surface of the vane and a distance from the center of the aperture to a first end of the second cavity is between 0.130 and 0.132. 
     A ratio of a distance between from the first surface to the second surface of the vane and a distance from the center of the aperture to a first end of the fourth cavity is between 0.130 and 0.132. 
     A variable diffuser includes a shroud, a backing plate, and a plurality of vanes positioned between the shroud and the backing plate and pivotally connected to the shroud. Each vane includes an inlet end, an outlet end, a first surface adjacent to the shroud, a second surface adjacent to the backing plate, a leading surface extending from the inlet end to the outlet end, and a trailing surface extending from the inlet end to the outlet end. Each vane also includes a first cavity on the first surface of the vane adjacent the inlet end, a second cavity on the first surface of the vane adjacent the outlet end, a third cavity on the second surface of the vane adjacent the inlet end, and a fourth cavity on the second surface of the vane adjacent the outlet end. 
     The variable diffuser of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components: 
     The variable diffuser further includes a first notch in the first surface extending from the leading surface to the first cavity, a second notch in the first surface extending from the leading surface to the second cavity, a third notch in the second surface extending from the trailing surface to the third cavity, and a fourth notch in the second surface extending from the trailing surface to the fourth cavity. 
     Each vane further includes a first aperture configured to receive a pivot pin, wherein the aperture extends from the first surface to the second surface, a second aperture configured to receive a fastener to connect the shroud to the backing plate, wherein the second aperture extends from the first surface to the second surface, and a third aperture configured to receive a fastener to connect the shroud to the backing plate, wherein the third aperture extends from the first surface to the second surface. 
     A ratio of a distance from the center of the first aperture to a first end of the first cavity and a distance from the leading surface to a first side of the first cavity is between 2.450 and 3.600. 
     A ratio of a distance from the center of the first aperture to a first end of the first cavity and a distance from the trailing surface to a second side of the first cavity is between 2.450 and 3.600. 
     A ratio of a distance from the center of the first aperture to a first end of the third cavity and a distance from the leading surface to a first side of the third cavity is between 2.450 and 3.600. 
     A ratio of a distance from the center of the first aperture to a first end of the third cavity and a distance from the trailing surface to a second side of the third cavity is between 2.450 and 3.600. 
     A ratio of a distance from the center of the first aperture to a first end of the second cavity and a distance from the leading surface to a first side of the second cavity is between 32.875 and 44.167. 
     A ratio of a distance from the center of the first aperture to a first end of the second cavity and a distance from the trailing surface to a second side of the second cavity is between 32.875 and 44.167. 
     A ratio of a distance from the center of the first aperture to a first end of the fourth cavity and a distance from the leading surface to a first side of the fourth cavity is between 32.875 and 44.167. 
     A ratio of a distance from the center of the first aperture to a first end of the fourth cavity and a distance from the trailing surface to a second side of the fourth cavity is between 32.875 and 44.167. 
     While the invention has been described with reference to an exemplary embodiment(s), 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(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.