| CPC F04D 29/124 (2013.01) [F04D 17/122 (2013.01)] | 20 Claims |

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1. A compressor comprising:
a first compressor wheel;
a second compressor wheel;
a drive shaft connecting the first compressor wheel to the second compressor wheel, the drive shaft comprising:
an outer shaft extending from the first compressor wheel to the second compressor wheel; and
an inner shaft disposed radially inwards of the outer shaft and extending through the first compressor wheel and the second compressor wheel; and
two or more helical seals disposed on the outer shaft of the drive shaft, each helical seal of the two or more helical seals extending away from an outer surface of the outer shaft and around a circumference of the outer shaft, wherein an outer diameter of each helical seal of the two or more helical seals is greater than an outer diameter of the outer shaft, and wherein the two or more helical seals are configured to inhibit flow of fluid between the first compressor wheel and the second compressor wheel.
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