Centrifugal compressor

A centrifugal compressor, comprising:

• a low speed shaft that is rotated by a drive source;
• an impeller that is attached to a high speed shaft, which rotates at a speed higher than a speed of the low speed shaft;
• a speed increaser that transmits power of the low speed shaft to the high speed shaft;
• a housing that includes
• a drive source chamber that accommodates the drive source,
• an impeller chamber that accommodates the impeller,
• a speed increaser chamber that accommodates the speed increaser, and
• a dividing wall having an insertion hole through which the high speed shaft is passed, the dividing wall dividing the impeller chamber and the speed increaser chamber from each other;
• a seal member provided between an outer circumferential surface of the high speed shaft and an inner circumferential surface of the insertion hole;
• an oil pan that stores oil supplied to the speed increaser;
• an oil passage that supplies oil stored in the oil pan to the speed increaser, and returns the oil to the oil pan;
• and
• a pressure relief passage that connects the oil pan to a pressure relief hole that opens in an outer surface of the housing, wherein
• the pressure relief passage includes a first pressure relief passage and a second pressure relief passage that extend from the oil pan in a branching manner,
• the second pressure relief passage merges with the first pressure relief passage to form a merging portion,
• the pressure relief hole is arranged above the merging portion in a direction of gravitational force,
• the first pressure relief passage is arranged below the merging portion in the direction of gravitational force,
• a minimum cross-sectional area of the second pressure relief passage is smaller than a minimum cross-sectional area of the first pressure relief passage,
• the second pressure relief passage includes a bent portion formed by bending the second pressure relief passage, the bent portion being configured to perform gas/liquid separation by crushing bubbles,
• when reaching the merging portion from the bent portion, oil is returned to the oil pan via the first pressure relief passage, and
• when reaching the merging portion from the bent portion, gas is discharged to an outside of the housing via the pressure relief hole.