Centrifugal compressor

Abstract

A centrifugal compressor includes a high-speed shaft, an impeller, a housing having a partition wall and a discharge passage, and a sealing member. The centrifugal compressor includes a bypass that is formed in the partition wall and has an inlet connected to the discharge passage and an outlet connected to a space between a back surface of the impeller and the partition wall. The inlet is located outward of the outlet and the outlet is located outward of the sealing member in a radial direction of the high-speed shaft. The bypass includes an outlet passage that extends to the outlet outwardly in the radial direction of the high-speed shaft. Air introduced from the inlet flows out of the outlet through the outlet passage so as to form a flow of air flowing away from the sealing member in the space.

What is claimed is: 
     
         1 . A centrifugal compressor comprising:
 a low-speed shaft that is rotated by a drive source;   a high-speed shaft that is configured to rotate at a rotation speed that is higher than a rotation speed of the low-speed shaft;   a speed-up gear that is configured to transmit power of the low-speed shaft to the high-speed shaft;   an impeller mounted on the high-speed shaft;   a housing having an impeller chamber for accommodating the impeller, a speed-up gear chamber for accommodating the speed-up gear and oil, a partition wall that separates the impeller chamber from the speed-up gear chamber and has an insertion hole through which the high-speed shaft is inserted, a pressure-relief passage for releasing air in the speed-up gear chamber to an outside of the housing, and a discharge passage to which the air compressed by rotation of the impeller is discharged; and   a sealing member disposed between an outer peripheral surface of the high-speed shaft and an inner peripheral surface of the insertion hole, wherein   the centrifugal compressor includes a bypass that is formed in the partition wall and has an inlet connected to the discharge passage and an outlet connected to a space between a back surface of the impeller and the partition wall,   the inlet is located outward of the outlet and the outlet is located outward of the sealing member in a radial direction of the high-speed shaft, and the bypass includes an outlet passage that extends to the outlet outwardly in the radial direction of the high-speed shaft, and   the air introduced from the inlet flows out of the outlet through the outlet passage so as to form a flow of air flowing away from the sealing member in the space.   
     
     
         2 . The centrifugal compressor according to  claim 1 , wherein
 the outlet of the bypass has a ring shape to surround the high-speed shaft.   
     
     
         3 . The centrifugal compressor according to  claim 1 , wherein
 the partition wall includes a projected portion that projects toward the back surface of the impeller, and   the outlet passage opens outward of the projected portion in the radial direction of the high-speed shaft.   
     
     
         4 . The centrifugal compressor according to  claim 1 , wherein
 the outlet passage extends, in an axial direction of the high-speed shaft, from a side on which the speed-up gear chamber is located toward the impeller to chamber, so as to become gradually distant from the high-speed shaft.   
     
     
         5 . The centrifugal compressor according to  claim 1 , wherein
 the bypass is formed in the housing.