Variable-speed oil-free refrigerant centrifugal compressor with variable geometry diffuser

摘要

A refrigerant compressor includes a housing providing a refrigerant outlet having a throat. An electric motor is provided in the housing to directly drive an impeller via a shaft about an axis in response to a variable speed command. The impeller includes an outlet end aligned with variable geometry diffuser. A magnetic bearing assembly rotationally supports the shaft relative to the housing in response to a magnetic bearing command. A member is arranged to adjust the throat area, and which can move in a direction generally parallel to the axis in response to an actuator receiving a compressor regulation command. A controller is configured to respectively provide the variable speed command, the magnetic bearing command and the compressor regulation command to the electric motor to vary throat area, the magnetic bearing assembly and the actuator to obtain a desired compressor operation without the need of variable inlet geometry.

主权项

1. A refrigerant centrifugal compressor comprising:
a housing providing an inlet, an outlet consisting of a diffuser having a throat area and a volute; an electric motor provided in the housing and configured to directly drive an impeller via a shaft about an axis in response to a variable speed command, the impeller including an outlet end aligned with a variable geometry diffuser, wherein the variable geometry diffuser includes vanes; a magnetic bearing assembly configured to rotationally support the shaft relative to the housing in response to a magnetic bearing command; an actuator; a variable geometry diffuser member downstream of the impeller receiving a compressor regulation command, wherein the actuator adjusts the position of the variable geometry diffuser member, and wherein the variable geometry diffuser member is configured to at least partially extend into a vane throat between adjacent vanes of the variable geometry diffuser; and a controller in communication with the electric motor, magnetic bearing assembly and the actuator, the controller configured to respectively provide the variable speed command, magnetic bearing command and the compressor regulation command to the electric motor to vary the throat area, magnetic bearing assembly and the actuator to obtain a desired compressor operating condition; and wherein the variable geometry diffuser member is configured to completely surround each vane of the variable geometry diffuser.