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.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation application of PCT Patent Application No. PCT / CN2014 / 084414, entitled “Multi-stage Centrifugal Compressor and Air Conditioning Unit”, filed on Aug. 14, 2014, which claims priority to Chinese Patent Application No. 201310377356.2, entitled “Multi-stage Centrifugal Compressor and Air Conditioning Unit”, filed on Aug. 26, 2013, the entire contents of which are incorporated herein by reference.TECHNICAL FIELD[0002]The present disclosure relates to the technical field of compressors and air conditioners, more especially, to a multi-stage centrifugal compressor and an air conditioning unit.BACKGROUND[0003]In the prior art, the centrifugal compressor for refrigeration use is a one-stage or two-stage compressor. In the common refrigeration range, such as the temperatures 12 / 7° C. of the inflow and outflow freezing water, and the temperatures 30 / 35° C. of the inflow and outflow cooling water, as the pressure rati...

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Benefits of technology

[0030]As compared with the prior art, the present disclosure has following beneficial effects: as the pressure ratio of the multi-stage centrifugal compressor is higher, the multi-stage centrifugal compressor and the air conditioning unit operate efficiently and stably; the connections between the components and parts of the unit are optimized, which makes the production cost lower and the area occupied smaller; the intermediate gas injection can save energy, and enhance the efficiency; the gas flow state of other impellers except the first stage impeller are improved, thereby lowering the gas temperature and reducing the compression work; flexible connection pipeline arrangements are allowed, and thus the pipelines are easy to fix, to operate and to maintain; the overall unit is compact in structure, which reduces noises effectively, and it is easy to meet the customers' requirements for the overall dimensions of the overall air conditioning unit; the axial forces are smaller, and the service life is longer.

Problems solved by technology

However, in order to realize a higher pressure ratio, the outer diameter or the rotating speed of the impeller has to be increased, which conflicts with the requirement of the material strength of the impeller.

If the increase of the pressure ratio is realized only by increasing the rotating speed but keeping the dimensions of the impeller unchanged, it is likely that the speed of the rotating part approaches or reaches the inherent critical rotating speed and thus causes resonances, thereby affecting the reliable operation of the compressor and the air conditioning unit.

But, with no doubt, these solutions have the following defects: the overall production cost and maintenance cost of the unit are too high, the overall dimensions are oversized, and the area occupied by the relative equipment room is too large, and thus it is difficult to meet the practical application requirements of customers.

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