Multi-stage centrifugal compressor and air conditioning unit

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. A gas outlet of the impellers arranged at the first end of the shaft communicates with a gas inlet of the impellers arranged at the second end of the shaft through a connection pipeline, so that the pressure ratio and the energy efficiency are improved.

What is claimed is: 
     
         1 . A multi-stage centrifugal compressor, comprising a power portion and an impeller portion, wherein,
 the power portion comprises a motor having a shaft; the 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, number of the impellers on the first end of the shaft is equal to number 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 the number of the impellers on the second end of the shaft;   a first stage impeller farthest away from the motor is arranged at the first end of the shaft;   other impellers at the first end of the shaft are arranged in an ascending order;   an Nth stage impeller nearest to the motor is arranged at the second end of the shaft; other impellers at the second end of the shaft are arranged in a descending order;   a gas outlet of the impellers arranged at the first end of the shaft communicates with a gas inlet of the impellers arranged at the second end of the shaft through a connection pipeline;   wherein, the gas outlet of the impellers arranged at the first end of the shaft is same gas outlet of the impeller nearest to the motor and arranged at the first end of the shaft; the gas outlet of the impellers arranged at the second end of the shaft is same gas outlet of the impeller farthest to the motor and arranged at the second end of the shaft.   
     
     
         2 . The multi-stage centrifugal compressor according to  claim 1 , wherein, a connection pipeline is disposed outside the multi-stage centrifugal compressor or inside a casting of the multi-stage centrifugal compressor. 
     
     
         3 . The multi-stage centrifugal compressor according to  claim 1 , wherein, except the first stage impeller, gas-injection inlets are provided at inlets of other impellers, including a first gas-injection inlet provided at the inlet of the second stage impeller, . . . , and an (N−1)th gas-injection inlet provided at the Nth stage impeller. 
     
     
         4 . The multi-stage centrifugal compressor according to  claim 1 , wherein, the centrifugal compressor further comprises at least two bearings; at least one bearing is sleeved on the first end of the shaft and at least one bearing is sleeved on the second end of the shaft. 
     
     
         5 . The multi-stage centrifugal compressor according to  claim 4 , wherein, the bearings are embodied as a roll bearing, slide bearing or magnetic floating bearing. 
     
     
         6 . An air conditioning unit, comprising an evaporator and a condenser, wherein, the air conditioning unit further comprises the multi-stage centrifugal compressor as defined in  claim 1 . 
     
     
         7 . The air conditioning unit according to  claim 6 , wherein, a connection pipeline is disposed outside the multi-stage centrifugal compressor or inside a casting of the multi-stage centrifugal compressor. 
     
     
         8 . The air conditioning unit according to  claim 6 , wherein, the centrifugal compressor further comprises at least two bearings; at least one bearing is sleeved on the first end of the shaft and at least one bearing is sleeved on the second end of the shaft. 
     
     
         9 . The air conditioning unit according to  claim 6 , wherein, the connection pipeline, which is disposed between the gas outlet of the impellers arranged at the first end of the shaft and the gas inlet of the impellers arranged at the second end of the shaft, is arranged inside the evaporator or inside the condenser. 
     
     
         10 . The air conditioning unit according to  claim 7 , wherein, the connection pipeline, which is disposed between the gas outlet of the impellers arranged at the first end of the shaft and the gas inlet of the impellers arranged at the second end of the shaft, is arranged inside the evaporator or inside the condenser. 
     
     
         11 . The air conditioning unit according to  claim 8 , wherein, the connection pipeline, which is disposed between the gas outlet of the impellers arranged at the first end of the shaft and the gas inlet of the impellers arranged at the second end of the shaft, is arranged inside the evaporator or inside the condenser. 
     
     
         12 . The air conditioning unit according to  claim 9 , further comprising an economizer;
 other impellers except the first stage impeller are each provided with a gas-injection inlet;   gas flash evaporated from the economizer is guided into the gas-injection inlet of the multi-stage centrifugal compressor.   
     
     
         13 . The air conditioning unit according to  claim 10 , further comprising an economizer;
 other impellers except the first stage impeller are each provided with a gas-injection inlet;   gas flash evaporated from the economizer is guided into the gas-injection inlet of the multi-stage centrifugal compressor.   
     
     
         14 . The air conditioning unit according to  claim 11 , further comprising an economizer;
 other impellers except the first stage impeller are each provided with a gas-injection inlet;   gas flash evaporated from the economizer is guided into the gas-injection inlet of the multi-stage centrifugal compressor.   
     
     
         15 . The air conditioning unit according to  claim 12 , wherein, the gas flash evaporated from the economizer is guided into an (N−1)th gas-injection inlet preferably. 
     
     
         16 . The air conditioning unit according to  claim 12 , wherein, the air conditioning unit comprises N−1 economizers corresponding to N−1 gas-injection inlets;
 each economizer comprises an economizer inlet and an economizer outlet, and further comprises an economizer gas outlet in communication with the corresponding gas-injection inlet. 
 
     
     
         17 . The air conditioning unit according to  claim 12 , wherein, the air conditioning unit comprises only one economizer; the economizer is partitioned into several independent economizer parts, number of the economizer parts is the same as the number of the gas-injection inlets;
 each economizer part comprises an economizer inlet and an economizer outlet, and further comprises an economizer gas outlet in communication with the corresponding gas-injection inlet.   
     
     
         18 . The air conditioning unit according to  claim 13 , wherein, the air conditioning unit comprises only one economizer; the economizer is partitioned into several independent economizer parts, number of the economizer parts is the same as the number of the gas-injection inlets;
 each economizer part comprises an economizer inlet and an economizer outlet, and further comprises an economizer gas outlet in communication with the corresponding gas-injection inlet.   
     
     
         19 . The air conditioning unit according to  claim 14 , wherein, the air conditioning unit comprises only one economizer; the economizer is partitioned into several independent economizer parts, number of the economizer parts is the same as the number of the gas-injection inlets;
 each economizer part comprises an economizer inlet and an economizer outlet, and further comprises an economizer gas outlet in communication with the corresponding gas-injection inlet.   
     
     
         20 . The air conditioning unit according to  claim 8 , wherein, throttling devices are arranged on the refrigerant connection pipeline of an economizer inlet and arranged at an economizer outlet respectively.