Diffuser throttle ring control

Claim 1

A centrifugal vapor compressor comprising: a housing forming an inlet passageway for directing vapor into the compressor and a diffuser passageway for directing compressed vapor out of the compressor, said diffuser including a wall with an annular recess therein; an impeller rotatably mounted in the housing between the inlet passageway and the diffuser passageway; a diffuser throttle ring mounted in the annular recess to form a substantially sealed cavity between the walls of the annular recess and the back surface of the throttle ring, said throttle ring supported in the annular recess for movement across the diffuser passageway between a minimum throttling position and a maximum throttling position; control means for determining volumetric vapor flow rate through the compressor, and for generating a first control signal when the volumetric vapor flow rate through the compressor is equal to or greater than a predetermined flow rate corresponding to stable flow conditions for the compressor and a second control signal when the volumetric vapor flow rate through the compressor is less than the predetermined flow rate; and valve means for detecting the control signals generated by the control means, and for connecting the cavity behind the throttle ring to a relatively low pressure source to provide a pressure difference across the throttle ring which positively maintains the throttle ring at its minimum throttling position when the first control signal is detected, and for connecting the cavity behind the throttle ring to a relatively high pressure source to provide a pressure difference across the throttle ring which positively maintains the throttle ring at its maximum throttling position when the second control signal is detected.

Claim 5

A method of operating a centrifugal vapor compressor having a pressure controlled diffuser throttle ring which is positioned in either a minimum throttling position or a maximum throttling position in response to pressure differences between pressure in the diffuser passageway and pressure in a cavity behind the throttle ring, which comprises: determining the volumetric vapor flow rate through the compressor; generating a first control signal when the detected flow rate is equal to or greater than a predetermined flow rate which corresponds to stable flow conditions for the compressor; generating a second control signal when the detected flow rate is less than the predetermined rate; connecting the cavity behind the throttle ring to a relatively low pressure source in response to generation of the first control signal to provide a pressure difference across the throttle ring to positively maintain the throttle ring in its minimum throttling position; and connecting the cavity behind the throttle ring to a relatively high pressure source in response to generation of the second control signal to provide a pressure difference across the throttle ring to positively maintain the throttle ring in its maximum throttling position.

Claim 6

A method of operating a centrifugal vapor compressor having a pressure controlled diffuser throttle ring which is positioned in either a minimum throttling position or a maximum throttling position in response to pressure differences between pressure in the diffuser passageway and pressure in a cavity behind the throttle ring, which comprises: determining the volumetric vapor flow rate through the compressor; generating a first control signal when the detected flow rate is equal to or greater than a predetermined flow rate which corresponds to stable flow conditions for the compressor; generating a second control signal when the detected flow rate is less than the predetermined rate; connecting the cavity behind the throttle ring to a relatively low pressure source in response to generation of the first control signal to provide a pressure difference across the throttle ring to positively maintain the throttle ring in its minimum throttling position; and connecting the cavity behind the throttle ring to a relatively high pressure source in response to generation of the second control signal to provide a pressure difference across the throttle ring to positively maintain the throttle ring in its maximum throttling position.