Centrifugal compressor

Abstract

In order to reduce the rotating stall onset flowrate, this centrifugal compressor comprises: a vaneless diffuser (12) provided on a discharge outlet (6B) side of an impeller (6); and a fluid circulation flow path (21) having an inlet (21A) that opens into a first wall section (22) of a hub casing (2B) forming the vaneless diffuser (12) and also having an outlet (21B) that opens into a second wall section (23) of the hub casing (2B) facing a hub disk (6C) rear surface in the impeller (6). As a result of causing the first wall section (22) to protrude on to a wall section (31) side of the shroud casing (2A), the flow path width (D) of the vaneless diffuser (12) is smaller than the width (W) of the discharge outlet (6B) in the impeller (6). In addition, the hub casing (2B) comprises an inclined wall section (24) having a protruding end (24A) between the discharge outlet (6B) of the impeller (6) and the inlet of the vaneless diffuser (12), said inclined wall section (24) connecting the second wall section (23) and the first wall section (22).

Description

TECHNICAL FIELD[0001]The present invention relates to a centrifugal compressor in which a vaneless diffuser is provided on an outlet side of an impeller.BACKGROUND ART[0002]In general, an industrial centrifugal compressor is used in a petrochemical plant, a natural gas plant, or the like. In this kind of centrifugal compressor, a configuration is widely adopted, which uses a vaneless diffuser in which a vane is not provided in a diffuser portion on the outlet side of an impeller. The configuration which uses the vaneless diffuser has advantages in which the structure is simple, a loss decreases if a flow angle is appropriate, an operation range is wide, and a fluid vibrating force with respect to the impeller does not occur. However, in the vaneless diffuser, if the flow angle increases, the loss increases, a rotating stall occurs in which flows are nonuniform in the circumferential direction, and variation in pressures, shaft vibrations, vibrations of a discharge pipe, or the like ...

AI Technical Summary

Benefits of technology

The present invention provides a centrifugal compressor with a vanless diffuser that reduces distortion and flow disturbance. The design has an inclined wall section that allows a smooth transition of the circulating flow from the impeller to the diffuser, preventing any negative effects on the flow. Additionally, the narrowed flow path width by the inclined wall section allows for a smooth flow even at small flow rates, shifting the rotating stall generation point to the small flow rate side.

Problems solved by technology

However, in the vaneless diffuser, if the flow angle increases, the loss increases, a rotating stall occurs in which flows are nonuniform in the circumferential direction, and variation in pressures, shaft vibrations, vibrations of a discharge pipe, or the like occurs due to the rotating stall.

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