Abstract:
An air cycle machine has a housing which holds a compressor section, and a turbine section having an expansion area, and a fan section disposed outside of the housing. A shaft, which attaches to and is coaxial with the compressor section, the turbine section and the fan section, is supported by an air journal bearing and an air thrust bearing. The shaft has a hollow core for porting cooling air from the air journal bearing and the air thrust bearing, and a tube that extends into said expansion area and communicates cooling air from the turbine expansion area to the thrust bearing.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application relates to air bearings incorporated into an air cycle machine and more particularly to air seals that enable cooling of the air bearings. 
         [0002]    Air cycle machines are known, and may include a centrifugal compressor driven by compressed air and a centrifugal turbine that lowers the temperature of the compressed air. The output of the turbine is utilized as conditioned supply air for a space or components to be conditioned. 
       SUMMARY OF THE INVENTION 
       [0003]    According to an exemplar provided herein, an air cycle machine has a housing that holds a compressor section, and a turbine section having an expansion area, and a fan section disposed outside of the housing. A shaft, which attaches to and is coaxial with the compressor section, the turbine section and the fan section, is supported by an air journal bearing and an air thrust bearing. The shaft has a hollow core for porting cooling air from the air journal bearing and the air thrust bearing. The shaft also has, on an aft portion thereof, a forward opening and an aft opening for porting cooling air into the hollow core. A tube extends into an expansion area and communicates cooling air from the turbine expansion area to the thrust bearing and journal bearing. 
         [0004]    According to an exemplar provided herein, a forward bearing assembly for an air cycle machine has a seal having a flat outer portion, a pair of parallel sides, the sides being attached to a flat inner portion by an angled surface. The inner portion is parallel to the outer portion creating a thickness therebetween. A cylindrical pilot is disposed in an air cycle machine housing and has a flat area for receiving the flat outer portion of the seal. The pilot has an inner diameter wherein a ratio of the forward pilot inner diameter to the thickness of the seal is 20.09-15.05:1. 
         [0005]    According to an exemplar provided herein, an aft bearing assembly for an air cycle machine has a pilot, a seal and a seal land. The seal has a flat outer portion having a first width, a first side wall attaching to a first side of flat inner portion via a first angled wall, the flat inner portion having a second width wider than the first width, a second side wall extending radially outwardly from a second side of the inner portion via a second angled wall, an extension attaching to the second side wall and extending axially toward the first side wall and a radiused portion extending from the extension and attaching to the flat outer portion. The pilot is cylindrical and disposed in an air cycle machine housing. The pilot has a flat area for receiving the flat outer portion of the seal and has an inner diameter wherein a ratio of the forward pilot inner diameter to the thickness of the seal is 10.33-8.03:1. 
         [0006]    According to an exemplar provided herein, an air cycle machine has a curved tube that has a length along a curving central axis and a width along the curving central axis. The central axis is curved at a radius R of 0.500±0.04 inches (or 1.3±0.1 cm) along an upper portion thereof and a ratio of the length to width of the tube is from 1.456-1.657:1. 
         [0007]    According to an exemplar provided herein, a shaft for an air cycle machine has a hollow body, a forward flange extending radially from the hollow body, the forward flange having a first plurality of teeth radially extending teeth disposed thereon for cooperating with a seal, a first opening communicating with an interior of the body, a tooth in close proximity to and aft of the first opening, the tooth creating a barrier to air passing along the shaft and urging the air into the first opening, a second opening aft of the tooth and the second opening, and a second plurality of teeth aft of the tooth, the second opening and the first opening wherein the plurality of teeth creating a barrier to air passing along the shaft by the tooth and urging the air into the first opening. 
         [0008]    According to an exemplar provided herein, a turbine housing for an air cycle machine has an outer shell housing a compressor section and a turbine section, and an inner shell housing a hollow shaft, and defining an expansion area between the inner and outer shell. The inner shell has a forward pilot having a first inner diameter and an aft pilot having a second inner diameter wherein the ratio between the inner diameter of the forward pilot and the inner diameter of the aft pilot is 1.668-1.664:1. The forward pilot and the aft pilot each have a half-tear drop shaped indentation at an axial edge thereof. 
         [0009]    According to an exemplar provided herein, a method of installing a seal into an air cycle machine includes the steps of providing a first seal having an outer diameter and a thickness configured to engage a rotating surface wherein a ratio between the outer diameter and the thickness is 20.09-15.05:1, providing a housing having a first pilot having an inner diameter, and pressing the first seal into the first pilot. 
         [0010]    These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  shows a schematic of an air cycle machine incorporating a plurality of bearing seals. 
           [0012]      FIG. 1A  shows a schematic view of bearing seal arrangement taken along the lines A-A of  FIG. 1 . 
           [0013]      FIG. 1B  shows a schematic view of bearing seal arrangement taken along the lines B-B of  FIG. 1 . 
           [0014]      FIG. 2  is a perspective view of a tube used in the air cycle machine of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]      FIGS. 1 ,  1 A and  1 B, an example air cycle machine  20  (“ACM”) that may be incorporated into an air supply system (not shown) of a vehicle, such as an aircraft, helicopter, or land-based vehicle (not shown) is shown. The ACM  20  includes a compressor section  24 , a turbine section  26  and a fan section  28  all of which are generally disposed about as segmented main shaft  30 . The compressor section  24  includes a compressor rotor  32 . The turbine section  26  includes a turbine rotor  34 , and the fan section  28  includes a fan rotor  36 . The compressor rotor  32 , turbine rotor  34 , and fan rotor  36  are secured on the segmented main shaft  30  that has an axially extending tie rod  37  therewithin for co-rotation with the main shaft about an axis A. 
         [0016]    A forward portion  38  of the main shaft  30  has a plurality of openings  40  to ambient and attaches to the fan rotor  36 . An aft portion  42  of the main shaft attaches to the forward portion  38  of the main shaft  30  and has a circular, radially extending, flange  44  extending from a body  46  thereof to cooperate with a forward pilot  48 . The flange  44  has three teeth  45  extending therefrom in register with a forward seal  50  disposed on the forward pilot  48  (e.g., a flat area on the housing  90 ). Each of the teeth  45  has a roughly triangular cross-section, and is nominally 0.045 in. (0.114 cm) high with a flattened upper portion  49  that is 0.010 in. (0.025 cm) wide. The ratio of height to width of each tooth  45  is about 4.5:1. An aft portion  62  of the body  46  has, a first opening  64  into the body  46  forward of a tooth  66 , a second opening  68  into the body  46  aft of the tooth  66  and a second plurality of teeth  70  aft of the opening  68 . The tooth  66  and the second plurality of teeth  70  are in register with an aft seal  71  mounted on an aft pilot  72 , as will be discussed herein. The tooth  66  and the second plurality of teeth  70 , which includes five teeth, have roughly triangular cross-sections, are nominally 0.045 in high and have a flattened upper portion  51  that is 0.010 in. (0.025 cm) wide. The ratio of height to width of each tooth  66 ,  70  is about 4.5:1 to ensure that a proper amount of air may leak through to cool the bearings as will be discussed infra. 
         [0017]    The ACM  20  has an aft housing (e.g., outer shell)  74  that houses an aft air journal bearing  76 , the forward and aft pilots  48 ,  72 , the turbine section  26 , the compressor section  24 , the aft portion  42  of the main shaft  30 , and a thrust air bearing  78 . The forward housing  80  houses the forward portion  38  of the main shaft  30 , a forward journal air bearing  82  and a forward air seal  84 . The forward housing  80  and the aft housing  74  are attached together by bolts  86  and define an annular area  88  therebetween. 
         [0018]    The aft housing  74  has a conical portion  90  (e.g., inner shell) that defines on a radially outer portion thereof an expansion area  92  for air exiting the turbine rotor  34 . The conical portion  90 , on a radially inner portion thereof has the forward pilot  48  in which the forward seal  50  is mounted the aft pilot  72  in which the aft seal  71  is mounted, and the aft journal air bearing  76  mounted between the two seals  50 ,  71 . 
         [0019]    Referring now to  FIG. 1A , the forward pilot  48 , which is flat and annular with a half teardrop-shaped cut-out  96  at either end thereof, houses the forward seal  50 , which may be made of a graphite-infused polyimide material and which partially covers the half teardrop-shaped cut-outs  96  to allow air to circulate behind the seal to allow cooling thereof. The cut-out  96  insures that upon machining, no impediments are left that would interfere with mounting seal  50  on the pilot  48 . 
         [0020]    The forward pilot ID and the forward seal OD coincide at 2.410±0.001 in. (6.121±0.025 cm) and the seal forward has a thickness T of 0.140±0.020 in. (0.356±0.051 cm), wherein the ratio of the forward pilot ID to the thickness of the forward seal  50  is 20.09-15.05:1. The ratio insures the proper cooperation of the seal to a plurality of teeth, in this case three (though other numbers of teeth are contemplated), that are disposed at the end of flange  44  attached to the main shaft  30 . The forward seal  50  is 0.295±0.005 in. (0.75±0.012 cm) wide to ensure the teeth  45  are always in close proximity to the forward seal  50 . 
         [0021]    The forward seal  50  has a flat back portion  100 , a pair of parallel sides  102  and a top portion  104 . The top portion  104 , which functions as a seal land, is joined to the sides  102  by a pair of angled surfaces  106  that are disposed at a 40° angle relative to the back portion  100 . The top portion interacts with the forward plurality of teeth as will be discussed infra. The seal ID is 2.246±0.001 in. (5.705±0.003 cm) and the ratio between the forward seal internal diameter and the forward seal outer diameter is 1.074-1.072:1. 
         [0022]    Referring now to  FIGS. 1B , the aft pilot  72 , which is flat and annular, houses the aft seal  71 , which may be made of a graphite-infused polyimide material. The aft pilot  72  has an ID of 1.446±0.001 in. (3.67±0.003 cm) and the aft seal has a thickness T 1  of 0.16±0.02 in. (0.406±0.051 cm), wherein the ratio of the aft pilot ID to the thickness of the aft seal is from 10.33-8.03:1. The ratio insures the proper cooperation of the seal to a plurality of teeth  66 ,  70 , in this case six (though other numbers of teeth are contemplated), that are disposed in the body  46  of the aft portion  42  of the main shaft  30 . The aft pilot  72  has a width W of 0.500±0.005 in. (1.27±0.013) and the teeth  66 ,  70  have a height of 0.045 in. (0.114 cm) to ensure the teeth are always in close proximity to the aft seal  71 . 
         [0023]    The aft pilot  72  is flat with a half teardrop-shaped cut-out  110  machined at either end thereof. The aft seal  71  has a flat back portion  112  that mostly covers the half teardrop-shaped cut-outs  110 , which insure that, upon machining, no impediments are left that would interfere with mounting aft seal  71  on the pilot  72 , a forward side portion  114 , a first chamfered portion  116  attaching to the forward side portion  114 , and a top portion  118 , which acts as a seal land, that interacts with the teeth  66 ,  70 . The aft seal  71  also has an aft side portion  120  that attaches to the bottom portion  122  via a radius portion  124  that attaches to an axially extending portion  126 . The extending portion  126  attaches to the flat back portion  112 . The aft side portion  120  attaches to the top portion  118  via a second chamfered surface  128 . 
         [0024]    The top portion  118  interacts with the teeth  66 ,  70  to minimize a flow of relatively warm air flowing past the air journal bearing  76  into the expansion area  92 . The tooth  66  blocks the air flowing through the air journal bearing  76  that tends to be drawn to ambient through the first hole  64  in the body  46 . However, any air flowing past the tooth  66  is induced to flow into the second hole  68  to ambient. The plurality of teeth  70 , which separates the aft journal bearing  76  from the turbine section  26 , creates a relatively high pressure area compared to the second hole  68  to further urge the relatively warmer air flowing from the aft air journal bearing  76  to flow through the second hole  68  to ambient and keep the relatively warmer air from mixing with the relatively cool air in the turbine section  26 . 
         [0025]    The ratio between the ID of the forward seal  50  to the ID of the aft seal  71  ranges from 1.665-1.668 to one. The ratio indicates the relationship required by the forward and aft seal to properly cool the thrust bearing  78  and the air journal bearing  76 . Similarly the ratio between the ID of the forward pilot  48  and the ID of the aft pilot  72  is 1.668-1.664:1. 
         [0026]    A forward opening  40  in shaft  30  has therein adjacent to the forward air seal  84  to ensure that air passing through the forward seal  50  passes to ambient through the interior of the main shaft  30 . The ratio of teeth between the first and second hole and the number of teeth aft of the second hole is about 1:5 to minimize air flow from forward of the aft plurality of teeth to aft of the aft plurality of teeth. Though one tooth and an array of five teeth are shown other numbers of teeth are contemplated. 
         [0027]    Furthermore, the ratio of the aft teeth  66 ,  70  to the forward plurality of teeth  45  is about 2:1. The ratio of the forward teeth  45  to the tooth  66  between the first and second holes  64 ,  68  in the segmented shaft is 3:1. These ratios aid the metering of the correct flow of air from the thrust bearing  78  through the air journal bearing  76  to cool those bearings. 
         [0028]    A first bore  140  is drilled into a bottom portion  150  of the aft housing  74  from the area  144 . The first bore  140  is 0.272±0.005 in. (0.691±0.013 cm) thick and 1.16±0.03 in. (2.946±0.076 cm) long and is drilled at angle of about 15° relative to the Axis A. A second bore  146 , which is nominally 0.25 in. thick and 0.85±0.03 in. (2.16 cm±0.076 cm) long past a countersunk portion  148  and is drilled at angle of about 15° relative to the Axis A and 30° relative to the first bore  140 , is drilled into the bottom portion  150  of the aft housing  74  from a turbine inlet cavity  152  to intersect the first bore  140 . 
         [0029]    Referring to  FIG. 2 , a curved tube  156 , which is 1.18±0.03 in. long along a central axis B thereof, is 0.76±0.03 in. (1.93±0.076 cm) wide along a central axis thereof and is curved at a radius R of 0.500±0.04 inches (or 1.3±0.1 cm) along an upper portion  158  thereof. The tube  156  fits within the second bore  146  and has an opening  170  for inducing air entering the turbine inlet cavity  152  to enter the tube  156 . The opening  170  is positioned into the flow of air in the turbine inlet cavity to encourage flow into the tube  156 . The ratio of the length to width of the tube  156  is from 1.456-1.657:1 that insures that the tube extends properly into the turbine expansion area to draw cooling air. 
         [0030]    Referring back to  FIG. 1 , air in the turbine inlet cavity  152  is captured by the tube  156  and directed through the, the second bore  146 , first bore  140  into the area  144  from which it flows across the forward and aft sides  180 ,  182  of the thrust bearing  78 . Air then migrates from the aft side  182  of the thrust bearing  78  where it is metered through the forward pilot  48  and forward seal  50 , through aft air journal bearing  76  to an aft pilot  72  and aft seal  71  where the air is dumped into the interior of the main shaft  30  through first opening  64  or second opening  68  where it flows through the main shaft  30  through openings  40  to ambient. The combination of the teeth  45  in register with the forward seal  50 , the teeth  66  and  70  in register with the aft seal  71 , and the first and second openings  64 ,  68  act to meter cooling air through the thrust bearing  78  and the aft air journal bearing  76  as discussed herein above. All the teeth herein  45 ,  66 ,  70  are nominally spaced at 0.006 in. (0.015 cm) from each seal  50 ,  71 . 
         [0031]    Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments. 
         [0032]    The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.