Abstract: A regulator assembly, comprising a vaned diffuser, a motor, a driving gear engaged with a driven gear, the driven gear having rectangle-shaped through holes thereon, the rectangle-shaped through holes disposed and extending along an axis of the driven gear, and a regulating mechanism including a regulator, a supporting member, wherein the regulator is sleeved on the supporting member, and wherein the vaned diffuser is fixed on the supporting member, and regulator sliding members fixed to the regulator through the rectangle-shaped through holes of the driven gear, whereby the motor is configured to drive the driving gear to rotate, the driving gear is configured to drive the driven gear to rotate, the driven gear is configured to push the regulator sliding members to move, and the regulator sliding members are configured to drive the regulator to rotate relative to the vaned diffuser, thus driving the regulator to move along its axis.

Abstract: A multi-stage centrifugal compressor and an air conditioning unit are disclosed. The multi-stage centrifugal compressor comprises a power portion and an impeller portion. The power portion comprises a motor (6), a shaft of the motor comprises a first end and a second end. The impeller portion comprises N impellers, wherein N is equal to or more than 2 and less than 10. When N is an even, the number of the impellers on the first end of the shaft is equal to that of the impellers on the second end of the shaft. When N is an odd, the number of the impellers on the first end of the shaft is one more than that of the impellers on the second end of the shaft. The first stage impeller farthest away from the motor (6) is arranged at the first end of the shaft; other impellers at the first end of the shaft are arranged in an ascending order. The Nth stage impeller nearest to the motor (6) is arranged at the second end of the shaft; other impellers at the second end of the shaft are arranged in a descending order.