Centrifugal Compressor Return Vane Curvature for Swirl Removal

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Solution Overview

Problem

In multistage centrifugal compressors, the reduction in size of the return channel leads to increased fluid velocity and decreased return vane length, causing flow separation and an increase in the swirl velocity component at the exit of the return vane, which reduces energy efficiency and pressure increase.

Innovation Solution

The multistage centrifugal compressor design includes a return flow path with a radial flow path, an L-shaped bend flow path, and an axial flow path, where the return vane is arranged in both the radial and L-shaped bend flow paths. The rear edge of the return vane near the hub-side connection has a linear shape, while the rear edge near the shroud-side connection has a curved shape protruding downstream, with the hub-side connection part positioned on the inner radial side of the shroud-side connection part.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the return channel is moved toward the inner radial side for size reduction, then the compressor size is reduced, but flow separation occurs and swirl velocity component increases

Engineering Contradiction:

Improvecompressor sizeVSAvoidenergy efficiency

Core Design Contradiction:

Volume of moving objectVSLoss of energy

Solution Approach 1:

The return vane rear edge is designed with non-uniform curvature: the hub-side connection part has a smaller curvature radius while the shroud-side connection part has a larger curvature radius. This local differentiation optimizes flow characteristics at different radial positions, preventing flow separation and reducing swirl velocity component while maintaining compact compressor size.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The return vane rear edge incorporates curved surfaces with varying curvature radii instead of a linear or uniformly curved shape. The curved design at the shroud-side connection part and the different curvature at the hub-side connection part create smoother flow transitions, reducing flow separation and energy losses while achieving compact dimensions.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Volume of moving object

If the return vane length is decreased for size reduction, then the compressor size is reduced, but swirl velocity component removal becomes insufficient

Engineering Contradiction:

Improvecompressor sizeVSAvoidswirl velocity removal effectiveness

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of simply extending the return vane length in the radial direction, the design utilizes the circumferential dimension by creating a curved rear edge profile. This allows the vane to effectively interact with flow at multiple radial positions (hub and shroud sides) without increasing overall vane length, thus maintaining compact size while improving swirl removal effectiveness.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 design effectively removes the swirl velocity component across the entire flow path height from the shroud to the hub, enhancing energy efficiency and pressure increase in the multistage centrifugal compressor.

Implementation Method 1

The centrifugal impeller provides energy to a fluid by rotating

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Implementation Method 2

The diffuser converts dynamic pressure of the fluid increased by the centrifugal impeller, to static pressure

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 3

Return vanes for removing a swirl velocity component of the fluid about a rotational shaft of the centrifugal impeller are arranged in the return channel

Methodology Applied

Scientific EffectFlow separation: Flow Separation

Data Source

PatentEP4538540A1Multistage centrifugal compressor

Publication Date: 2025.04.16 HITACHI IND PROD LTD

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AI summary

A multistage centrifugal compressor (100) according to the present invention is provided with: a rotational shaft (2); a centrifugal impeller (1) fixed to the rotational shaft (2); and a return flow path (4) constituted by a shroud (1b) and a hub (1a). In the return flow path (4), an L-shaped flow path is constituted by a radial flow path (9), an L-shaped bend flow path (7), and an axial flow path (8), a return vane (5) is disposed in the radial flow path (9) and the L-shaped bend flow path (7), a rear edge (51) of the return vane (5) extending to an inner diameter side up to the inside of the L-shaped bend flow path (7) has a linear shape near a hub-side connection part (51a) and a curved shape protruding toward a downstream side near a shroud-side connection part (51b), and the hub-side connection part (51a) of the return vane (5) is positioned closer to an inner diameter side than the shroud-side connection part (51b).