Centrifugal compressor with casing treatment bypass

Abstract

A centrifugal compressor for a chiller system includes a casing, an inlet guide vane, an impeller disposed downstream of the inlet guide vane, a motor and a diffuser. The casing has inlet and outlet portions with the inlet guide vane disposed in the inlet portion. The impeller is attached to a shaft rotatable about a rotation axis, and the motor rotates the shaft in order to rotate the impeller. The centrifugal compressor further includes a casing treatment bypass having an entrance port and an exit port. The casing treatment bypass injects refrigerant from a gap between the impeller and the inlet portion of the casing toward an area between the impeller and the inlet guide vane. The exit port of the casing treatment bypass is positioned upstream in a direction of a refrigerant flow with respect to the entrance port of the casing treatment bypass.

Description

BACKGROUND[0001]Field of the Invention[0002]The present invention generally relates to a centrifugal compressor used in a chiller system. More specifically, the present invention relates to a centrifugal compressor with a casing treatment bypass.[0003]Background Information[0004]A chiller system is a refrigerating machine or apparatus that removes heat from a medium. Commonly a liquid such as water is used as the medium and the chiller system operates in a vapor-compression refrigeration cycle. This liquid can then be circulated through a heat exchanger to cool air or equipment as required. As a necessary byproduct, refrigeration creates waste heat that must be exhausted to ambient or, for greater efficiency, recovered for heating purposes. A conventional chiller system often utilizes a centrifugal compressor, which is often referred to as a turbo compressor. Thus, such chiller systems can be referred to as turbo chillers. Alternatively, other types of compressors, e.g. a screw comp...

AI Technical Summary

Benefits of technology

[0009]In a conventional centrifugal compressor as shown in FIG. 10, a hot gas bypass may be provided to connect the discharge side of the compressor and the suction side of the compressor to expand the operation range of the compressor. While this technique works relatively well, this system requires a pipe of a large diameter for the hot gas bypass, which results in increased costs. Especially in a case where a centrifugal compressor uses low pressure refrigerant such like R1233zd, the specific volume of the refrigerant is large compared to a case of conventional refrigerant such like R134a. This requires a large-diameter pipe for the hot gas bypass, which results in increased costs.

Problems solved by technology

The compressor loses the ability to maintain its lift when surge occurs and the entire system becomes unstable.

Surging can cause damage to the mechanical impeller / shaft system and / or to the thrust bearing due to the rotor shifting back and forth from the active to the inactive side.

While this technique works relatively well, this system requires a pipe of a large diameter for the hot gas bypass, which results in increased costs.

This requires a large-diameter pipe for the hot gas bypass, which results in increased costs.

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