Two stage electrically powered compressor

Abstract

An electrically powered compressor designed for providing high pressure ratio at low flow rate, yet having low power consumption. The compressor is designed for optimizing efficiency in fuel cell systems. The inventive compressors are however not limited to fuel cell system applications.

I claim:  
     
         1 . A two stage centrifugal compressor assembly comprising: 
 a rotor shaft ( 20 ) having first and second ends;    a first compressor casing ( 24 ) having a fluid inlet ( 25 ) and a fluid outlet ( 26 );    a first impeller ( 32 ) rotatable within the first compressor casing ( 24 );    a second compressor casing ( 24 ′) having a fluid inlet ( 28 ) and a fluid outlet ( 29 );    a second impeller ( 32 ′) rotatable within the second compressor casing ( 24 ′);    a motor disposed between the first and second compressor casings and comprising a stator ( 23 ,  23 ′) and a rotor ( 22 ,  22 ′) rotatable within the stator;    wherein the first impeller ( 32 ), second impeller ( 32 ′) and rotor ( 22 ,  22 ′) are mounted fixed against rotation on the rotor shaft ( 20 ) and rotatable therewith, and wherein the fluid outlet ( 26 ) of the first compressor casing communicates with the fluid inlet ( 28 ) of the second compressor casing.    
     
     
         2 . A compressor assembly as in  claim 1 , further comprising a pulley ( 21 ) mounted fixed against rotation on the rotor shaft ( 20 ).  
     
     
         3 . A compressor assembly as in  claim 1 , wherein said motor is a magnetically loaded composite motor.  
     
     
         4 . A compressor assembly as in  claim 1 , wherein said magnetically loaded composite motor rotor ( 22 ,  22 ′) and stator ( 23 ,  23 ′) serve as a magnetic bearing system.  
     
     
         5 . A compressor assembly as in  claim 1 , further comprising a bypass conduit ( 30 ) for bypassing said first compressor casing fluid inlet ( 25 ), and valve means for regulating flow through said bypass conduit.  
     
     
         6 . A two stage centrifugal compressor assembly comprising: 
 a rotor shaft ( 20 );    a first compressor casing ( 24 ) having a fluid inlet ( 25 ) and a fluid outlet ( 26 );    a first impeller ( 32 ) rotatable within the first compressor casing ( 24 );    a second compressor casing ( 24 ′) having a fluid inlet ( 28 ) and a fluid outlet ( 29 );    a second impeller ( 32 ′) rotatable within the second compressor casing( 24 ′);    a motor disposed between the first and second compressor casings and comprising a stator ( 23 ,  23 ′) and a rotor ( 22 ,  22 ′) rotatable within the stator;    wherein the first impeller ( 32 ), second impeller ( 32 ′) and rotor ( 22 ,  22 ′) are mounted fixed against rotation on the rotor shaft ( 20 ) and rotatable therewith, and    wherein the fluid outlet ( 26 ) of the first compressor casing communicates with the fluid inlet ( 28 ) of the second compressor casing;    and wherein said motor is a magnetically loaded composite motor.    
     
     
         7 . A compressor assembly as in  claim 6 , wherein said magnetically loaded composite motor rotor ( 22 ,  22 ′) and stator ( 23 ,  23 ′) serve as a magnetic bearing system.  
     
     
         8 . A compressor assembly as in  claim 7 , wherein said assembly further comprises a pulley ( 21 ) mounted fixed against rotation on said rotor shaft ( 20 ), wherein said assembly comprises first and second motors, and wherein said first and second motors are provided on first and second sides of said pulley.  
     
     
         9 . A compressor assembly as in  claim 6 , further comprising a bypass conduit ( 30 ) for bypassing said first compressor casing fluid inlet, and valve means for regulating flow through said bypass conduit.  
     
     
         10 . A power generating system comprising: 
 a fuel cell,    an electric motor ( 2 ) driven first stage centrifugal compressor ( 4 ), said compressor having a fluid inlet and a fluid outlet,    an electric motor ( 1 ) driven second stage centrifugal compressor ( 3 ), said compressor having a fluid inlet and a fluid outlet,    wherein said first stage centrifugal compressor fluid inlet is in communication with a source of oxidizing gas,    wherein said first stage centrifugal compressor fluid outlet is in communication with said second stage centrifugal compressor fluid inlet, and    wherein said second stage compressor fluid outlet is in communication with said fuel cell.    
     
     
         11 . A power generating system as in  claim 10 , wherein said oxidizing gas is air.  
     
     
         12 . A power generating system as in  claim 10 , wherein said first and second electric motors ( 1 ,  2 ) are driven by a source of feedback selected from fuel cell electrical output, fuel cell fuel consumption, fuel cell temperature, and operator input.  
     
     
         13 . A power generating system as in  claim 10 , wherein said fuel cell is provided in a hybrid vehicle.  
     
     
         14 . A power generating system as in  claim 10 , further including a catalytic burner for decomposing any hydrocarbons, unburned fuel, nitric oxide, carbon monoxide and particulates in the exhaust stream leaving the fuel cell.  
     
     
         15 . A power generating system as in  claim 10 , further comprising a bypass conduit for bypassing said first compressor casing fluid inlet, and valve means ( 5 ) for regulating flow through said bypass conduit.  
     
     
         16 . A method for imparting to a gas a high pressure ratio and low flow rate, with low power consumption, said method comprising: 
 precompressing gas in an electric motor ( 2 ) driven first stage centrifugal compressor ( 3 ), said compressor having a fluid inlet and a fluid outlet,    conveying gas precompressed in said first compressor ( 4 ) to an electric motor ( 1 ) driven second stage centrifugal compressor ( 3 ), said compressor having a fluid inlet and a fluid outlet,    further compressing said gas in said second stage centrifugal compressor.