Centrifugal refrigerant vapour compressors

Abstract

A centrifugal compressor for compressing a refrigerant vapour in a refrigeration cycle. The compressor comprises an impeller drive shaft supported by first and second radial bearings for rotation within the compressor housing and an impeller assembly including at least one centrifugal impeller wheel mounted on the impeller drive shaft to rotate with the impeller drive shaft. The first and second radial bearings are hydrodynamic fluid bearings in which the bearing fluid is the refrigerant vapour. The compressor further comprises a conduit for supplying a portion of the refrigerant vapour from the impeller assembly to the first and second fluid bearings.

1 . A centrifugal compressor for compressing a refrigerant vapour in a refrigeration cycle, the compressor comprising:
 an impeller drive shaft supported by first and second radial bearings for rotation within the compressor housing; and   an impeller assembly including at least one centrifugal impeller wheel mounted on the impeller drive shaft to rotate with the impeller drive shaft;   wherein the first and second radial bearings are hydrodynamic fluid bearings in which the bearing fluid is the refrigerant vapour, the compressor further comprising a conduit for supplying a portion of the refrigerant vapour from the impeller assembly to the first and second fluid bearings.   
     
     
         2 . A centrifugal compressor according to  claim 1 , further comprising an external supply of pressurised refrigerant vapour that is independent of the operation of the compressor and is adapted to be connected to the bearings to supply pressurised refrigerant vapour to the bearings at low speeds to float the bearings. 
     
     
         3 . A centrifugal compressor according to  claim 2 , wherein the external supply of pressurised vapour comprises a refrigerant pressurisation vessel that is adapted to capture and store pressurised refrigerant vapour from the compressor or a refrigeration system of which the compressor is a part when the compressor is running at normal operating speeds. 
     
     
         4 . A centrifugal vapour compressor according to  claim 2 , comprising a sensor for detecting whether or not the bearings are floated. 
     
     
         5 . A centrifugal vapour compressor according to  claim 4 , wherein the sensor is a sensor to detect reverse rotation of the impeller drive shaft. 
     
     
         6 . A centrifugal compressor according to  claim 1 , configured to operate with the impeller drive shaft oriented substantially vertically. 
     
     
         7 . A centrifugal compressor according to  claim 6 , wherein the impeller wheel or wheels are arranged on the impeller drive shaft so that the net force resulting from the pressure difference(s) across the impeller wheel(s) acts to lift the impeller and shaft/motor assembly upwards. 
     
     
         8 . A compressor according to  claim 1 , comprising variable inlet guide vanes at the inlet to the impeller or in multi-stage compressors at the inlet of one or more of the impeller compression stages. 
     
     
         9 . A centrifugal compressor for compressing a refrigerant vapour in a refrigeration cycle, the compressor comprising:
 an impeller drive shaft supported by first and second radial bearings for rotation within the compressor housing, wherein the first and second radial bearings are hydrodynamic fluid bearings in which the bearing fluid is the refrigerant vapour;   an impeller assembly including at least one centrifugal impeller wheel mounted on the impeller drive shaft to rotate with the impeller drive shaft; and   an external supply of pressurised refrigerant vapour that is independent of the operation of the compressor and is adapted to be connected to the bearings to supply pressurised refrigerant vapour to the bearings.   
     
     
         10 . A centrifugal compressor according to  claim 9 , wherein the external supply of pressurised vapour comprises a refrigerant pressurisation vessel that is adapted to capture and store pressurised refrigerant vapour from the compressor or a refrigeration system of which the compressor is a part when the compressor is running at normal operating speeds. 
     
     
         11 . A compressor system, comprising a plurality of compressors according to  claim 1  serving a single refrigeration circuit and a control system to monitor, control and protect the compressors. 
     
     
         12 . A refrigeration circuit comprising one or more compressors according to  claim 1  and a control system to monitor, control, and protect the compressor. 
     
     
         13 . A chilled water system comprising a refrigeration circuit according to  claim 12 . 
     
     
         14 . A Direction Expansion (DX) refrigeration system, comprising a refrigeration circuit according to  claim 12  serving one or more evaporators. 
     
     
         15 . An industrial process cooling system, comprising a refrigeration circuit according to  claim 12 . 
     
     
         16 . A building air conditioning system, comprising a Chilled Water System or DX System according to  claim 12 . 
     
     
         17 . A method of switching on a compressor, comprising the steps of:
 displacing a compressor shaft from a static (rest) position to a raised (active) position using a hydrodynamic bearing by introducing a volume of vapour through the bearing in order to create a lift force.   
     
     
         18 . A method of switching on a compressor according to  claim 17  wherein, when the compressor reaches a self-sustaining speed, a forced flow of vapour through the bearing in order to create a lift force is stopped. 
     
     
         19 . A method according to  claim 17 , wherein said volume of vapour is introduced when the compressor shaft is static, the method comprising sensing whether the shaft has been displaced to said lifted position and only applying a rotary driving force from a motor to the shaft after it has been displaced. 
     
     
         20 . A method according to  claim 19 , wherein sensing whether the shaft has been displaced comprises sensing a rotation of the shaft caused by the volume of vapour flowing through the bearing.