Multi-Nozzle Compressor Intake for Uniform Pre-Rotation Control

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Solution Overview

Problem

Single-shaft multi-stage centrifugal compressors face challenges in maintaining stable operation over a wide range of flow rates from the rated flow rate to significantly small flow rates while ensuring uniform flow rate distribution and maintaining discharge pressure, particularly due to non-uniform flow rate distribution caused by pre-rotation application in the first-stage centrifugal impeller.

Innovation Solution

The compressor design incorporates multiple intake nozzles, including a first intake nozzle aligned with the rotary shaft and a second intake nozzle deviated from the shaft, along with a rotation prevention plate and inflow control devices, to manage pre-rotation and enhance uniformity of flow rate distribution across the centrifugal impeller.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If pre-rotation is applied to the first-stage centrifugal impeller to expand the stable operation range to small flow rates, then the stable operation range is improved, but the discharge pressure is reduced

Engineering Contradiction:

Improvestable operation rangeVSAvoiddischarge pressure

Core Design Contradiction:

Adaptability or versatilityVSStress or pressure

Solution Approach 1:

The intake nozzle is divided into multiple independent nozzles (first intake nozzle and second intake nozzle) that can operate independently or simultaneously. This segmentation allows selective control of pre-rotation application: when pre-rotation is needed for small flow rate operation, only the second intake nozzle is activated; when rated flow rate operation is required, only the first intake nozzle is activated, thereby maintaining discharge pressure while expanding operational flexibility.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If multiple intake nozzles are provided to enable selective pre-rotation control, then the adaptability is improved, but the device complexity is increased

Engineering Contradiction:

Improveinflow control flexibilityVSAvoidintake nozzle configuration

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Multiple intake nozzles are merged into a single annular flow path part that receives flow from all nozzles. The flow paths of multiple nozzles are combined and merged before entering the centrifugal impeller, ensuring uniform flow rate distribution across the impeller inlet regardless of which nozzles are active. This merging approach provides inflow control flexibility while minimizing additional complexity compared to completely separate intake systems.

Inventive Principle:

Principle #5Merging (Combining)

3Speed

If the second intake nozzle is arranged in a direction deviated from the rotary shaft to create pre-rotation, then the pre-rotation effect is improved, but the flow rate distribution uniformity is worsened

Engineering Contradiction:

Improvepre-rotation velocityVSAvoidflow rate distribution uniformity

Core Design Contradiction:

SpeedVSStability of the object's composition

Solution Approach 1:

Different intake nozzles are arranged in different directions relative to the rotary shaft: the first intake nozzle is arranged toward the rotary shaft direction while the second intake nozzle is arranged in a direction deviated from the rotary shaft. This local quality differentiation allows the second intake nozzle to provide pre-rotation velocity when activated, while the first intake nozzle maintains uniform flow distribution when activated alone, thus optimizing both pre-rotation effect and flow rate distribution uniformity according to operational requirements.

Inventive Principle:

Principle #3Local quality

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 allows for adjustable pre-rotation application, improving flow rate distribution uniformity and enabling stable operation across a wide range of flow rates, from rated to small flow rates, by controlling the inflow of working fluid through multiple nozzles.

Implementation Method 1

an L-shaped bend part which is provided between the annular flow path part and an inlet of the centrifugal impeller and redirects a flow of the working fluid in an axial direction of the rotary shaft

Methodology Applied

Scientific EffectFluid flow redirection:

Implementation Method 2

compress and boost the gas sequentially by means of the centrifugal impellers provided in multiple stages on the rotary shaft

Methodology Applied

Scientific EffectCentrifugal compression: Centrifugal Force

Data Source

PatentUS20260078761A1Centrifugal fluid machine and single-shaft multi-stage centrifugal compressor

Publication Date: 2026.03.19 HITACHI IND PROD LTD

AI summary

A centrifugal fluid machine includes: a rotary shaft; a plurality of centrifugal impellers; a bearing; and a casing. An intake flow path is provided in the casing, and includes: a first intake nozzle; an annular flow path part provided around the rotary shaft; an L-shaped bend part which redirects the flow in an axial direction of the rotary shaft; a second intake nozzle provided in the casing on the side opposite to the first intake nozzle and connected to the annular flow path part; and a rotation prevention plate. The first intake nozzle is arranged toward a direction of the rotary shaft, and the second intake nozzle is arranged in a direction deviated therefrom. The first and second intake nozzles are equipped with an inflow control device. Accordingly, pre-rotation is applied to the working fluid from the intake nozzle and the flow rate distribution is suppressed from becoming non-uniform.