Centrifugal Compressor Casing Grooves for Surging Control

Solution Overview

Problem

Centrifugal compressors experience reduced discharge pressure and flow rate when casing treatment is performed to prevent surging, limiting their operation range due to recirculation of downstream fluid.

Innovation Solution

The design includes an annular flow passageway with a downstream groove communicating with high-pressure areas in the impeller-accommodating portion and an upstream groove covering the entire circumference of the inlet, forming a recirculation flow that suppresses surging while minimizing pressure ratio reduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If casing treatment is performed to prevent surging, then surging is suppressed, but discharge pressure and discharge flow rate are reduced

Engineering Contradiction:

Improvesurging suppressionVSAvoiddischarge pressure

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The groove is divided into two separate grooves: a first groove communicating with the inlet and a second groove communicating with the high-pressure part. This segmentation allows independent control of recirculation flow paths, enabling surging suppression while maintaining discharge pressure through selective fluid routing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second groove is positioned specifically at the high-pressure part of the impeller-accommodating portion, creating a localized recirculation path only where needed. This local quality approach prevents widespread pressure reduction while effectively suppressing surging at the critical high-pressure zone.

Inventive Principle:

Principle #3Local quality

2Reliability

If downstream fluid is recirculated upstream through the groove, then surging is suppressed, but pressure ratio during low-flow rate is decreased

Engineering Contradiction:

Improvesurging suppressionVSAvoidpressure ratio

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

Instead of full circumferential recirculation, the invention applies partial recirculation through the second groove only at the high-pressure part. This partial action is sufficient to suppress surging while avoiding excessive recirculation that would unnecessarily reduce pressure ratio and productivity.

Inventive Principle:

Principle #16Partial or excessive action

3Reliability

If the groove is provided over the entire circumference, then surging is effectively suppressed, but discharge flow rate is reduced

Engineering Contradiction:

Improvesurging suppressionVSAvoiddischarge flow rate

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The second groove is positioned specifically at the high-pressure part of the impeller-accommodating portion, creating a localized recirculation path only where needed. This local quality approach prevents widespread pressure reduction while effectively suppressing surging at the critical high-pressure zone.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of full circumferential recirculation, the invention applies partial recirculation through the second groove only at the high-pressure part. This partial action is sufficient to suppress surging while avoiding excessive recirculation that would unnecessarily reduce pressure ratio and productivity.

Inventive Principle:

Principle #16Partial or excessive action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration efficiently prevents surging and maintains discharge pressure and flow rate, extending the compressor's operation range without deteriorating the surging-suppressing effect.

Implementation Method 1

an impeller rotating at a high speed

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Implementation Method 2

a fluid reversely flows upstream of the impeller through the groove from a high-pressure part

Methodology Applied

Scientific EffectReverse flow:

Data Source

PatentUS9816524B2Centrifugal compressor

Publication Date: 2017.11.14 IHI CORP

AI summary

The centrifugal compressor (1) includes: an impeller (3); and a casing (2) accommodating the impeller (3). The casing (2) includes: an inlet (6); an impeller-accommodating portion (14) in which the impeller (3) is disposed; an annular chamber (11) formed around the inlet (6); a downstream groove (13) communicating a downstream end portion of the annular chamber (11) with the impeller-accommodating portion (14); and an upstream groove (12) communicating an upstream end portion of the annular chamber (11) with the inlet (6). In addition, the downstream groove (13) is provided in a predetermined range in a circumferential direction of the impeller (3) so as to communicate with a high-pressure part to occur in part of the impeller-accommodating portion (14), and the upstream groove (12) is provided over the entire circumference of the inlet (6).