Journal bearing with dual pass cooling for air machine

Abstract

A compressor rotor compresses air and delivers the compressed air to a downstream inlet and across a turbine rotor. A shaft rotates with the turbine rotor and the compressor rotor. The shaft is hollow with an inner bore and an outer periphery. At least one journal bearing supports a portion of the shaft, and has an inner bore spaced from the outer periphery of the shaft. A cooling air path is provided between the shaft outer periphery and the bearing inner periphery, and along a length of the bearing to at least one connection hole. The connection hole provides cooling air from an outer periphery of the shaft to the inner bore of the shaft. In a separate feature, a shaft for use in an air supply machine includes a hollow interior, with such a connection hole.

What is claimed is: 
     
         1 . An air supply machine comprising:
 a compressor rotor for compressing air and delivering compressed air to a downstream inlet, air from said downstream inlet passing across a turbine rotor to drive said turbine rotor to rotate, and said turbine rotor being connected to said compressor rotor such that rotation of said turbine rotor drives said compressor rotor to rotate and compress the air;   a shaft connected to rotate with said turbine rotor and said compressor rotor, said shaft being hollow with an inner bore and an outer periphery, and a journal bearing positioned to support a portion of said shaft, and to have an inner bore with an inner periphery spaced from said outer periphery of said shaft; and   a cooling air path to provide cooling air between said outer periphery of said shaft and said inner periphery of said journal bearing, and along a length of said journal bearing to at least one connection hole, said at least one connection hole providing cooling air from said outer periphery of said shaft to said inner bore of said shaft, the cooling air path then passing through said inner bore of said shaft and along a length of said journal bearing.   
     
     
         2 . The air supply machine as set forth in  claim 1 , wherein there are at least two of said journal bearings, with each of said journal bearings having cooling air flow at both an outer periphery of said shaft, and at an inner bore of said shaft. 
     
     
         3 . The air supply machine as set forth in  claim 2 , wherein the cooling air path passing along said outer periphery of said shaft in a first direction for a first of said journal bearings, and in a second direction for a second of said journal bearings, but the cooling air path within said inner bore of said shaft for both said first and second journal bearing being in a same direction. 
     
     
         4 . The air supply machine as set forth in  claim 3 , wherein the air passing along said inner bore of said shaft extending across said shaft to said connection hole at an end of one of said first and second journal bearing, and then passing along a length of both of said first and second journal bearings. 
     
     
         5 . The air supply machine as set forth in  claim 4 , wherein the cooling air passing to said second journal bearing extending to an exit downstream of the length of said second journal bearing, and said air passing along a length of both said first and second journal bearing also leaving said air supply machine through the same exit. 
     
     
         6 . The air supply machine as set forth in  claim 3 , wherein said journal bearing has an interior bearing foil forming a non-cylindrical inner face between said journal bearing and said outer periphery of said shaft. 
     
     
         7 . The air supply machine as set forth in  claim 6 , wherein said foil is generally corrugated. 
     
     
         8 . The air supply machine as set forth in  claim 1 , wherein the cooling air path is tapped from an inlet leading to said turbine rotor. 
     
     
         9 . The air supply machine as set forth in  claim 1 , wherein said air supply machine supplies air to a downstream use on an aircraft. 
     
     
         10 . The air supply machine as set forth in  claim 1 , wherein the cooling air path extends along the entire length of said journal bearing at both the outer periphery of said shaft, and the inner bore of said shaft. 
     
     
         11 . The air supply machine as set forth in  claim 1 , wherein a ratio of a diameter of said at least one connection hole to an outer diameter of said outer periphery of said shaft is between 0.077 and 0.094. 
     
     
         12 . An air machine comprising:
 a compressor rotor for compressing air and delivering compressed air to a downstream inlet, air from said downstream inlet passing across a turbine rotor to drive said turbine rotor to rotate, and said turbine rotor being connected to said compressor rotor such that rotation of said turbine rotor drives said compressor rotor to rotate and compress the air;   a shaft connected to rotate with said turbine rotor and said compressor rotor, said shaft being hollow with an inner bore, and an outer periphery, and at least two journal bearings positioned to support a portion of said shaft, and to each have an inner bore with an inner periphery spaced from said outer periphery of said shaft; and   a cooling air path to provide cooling air between said outer periphery of said shaft and said inner periphery of each said journal bearing, and along a length of one of said journal bearings to at least one connection hole, said at least one connection hole providing cooling air from said outer periphery of said shaft to said inner bore of said shaft, said cooling air then passing through said inner bore of said shaft and along a length of each of said journal bearings;   the cooling air path passing along said outer periphery of said shaft in a first direction for a first of said journal bearings, and in a second direction for a second of said journal bearings, but the cooling air path within said inner bore of said shaft for both said first and second journal bearing being in a same direction, the air passing along said inner bore of said shaft extending across said shaft to said at least one connection hole at an end of said first journal bearing, and then passing along a length of both of said first and second journal bearings, the cooling air passing to said second journal bearing extending to an exit downstream of the length of said second journal bearing, and the cooling air passing within the inner bore of the shaft also leaving said air machine through the same exit; and   said air machine supplying air to a downstream use on an aircraft.   
     
     
         13 . The air machine as set forth in  claim 12 , wherein the cooling air path extends along the entire length of said first and second journal bearings at both the outer periphery of said shaft, and the inner bore of said shaft. 
     
     
         14 . The air machine as set forth in  claim 12 , wherein at least one of said at least two journal bearings has an interior bearing foil forming a non-cylindrical inner face between said at least one journal bearing and said outer periphery of said shaft, and wherein said foil is generally corrugated. 
     
     
         15 . The air machine as set forth in  claim 12 , wherein the cooling air path is tapped from an inlet leading to said turbine rotor. 
     
     
         16 . The air machine as set forth in  claim 12 , wherein a ratio of a diameter of said at least one connection hole to an outer diameter of said outer periphery of said shaft is between 0.077 and 0.094.