A centrifugal compressor (20) includes an impeller (85) that defines an outside diameter (190) and is rotatable about an axis to provide a flow of compressed fluid. A portion of the compressed fluid passes around the outside diameter to define a leakage flow. An extension (200) extends from the impeller and includes a first seal portion (215) that has an average diameter (230) that is greater than or equal to about 50 percent of the outside diameter. A stationary seal ring (270) includes a second seal portion (275) that has a plurality of teeth (320). The second seal portion is disposed adjacent the first seal portion (215) to define a seal that inhibits the passage of the leakage flow.
