Centrifugal Compressor Diffuser Tapered Shroud Backflow Control

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Solution Overview

Problem

Centrifugal compressors face challenges in extending their operational range to low flow rates without surging, while maintaining performance at high flow rates, due to backflow area expansion on the upstream side.

Innovation Solution

The design incorporates a diffuser with a tapered surface and a protruding portion on the shroud-side wall, which minimizes the flow passage area and effectively blocks backflow, ensuring sufficient choking flow rate and preventing surging.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the diffuser has a conventional design with parallel walls, then the manufacturing is simple, but the operational range cannot be extended to low flow rates without surging

Engineering Contradiction:

Improveoperational rangeVSAvoiddiffuser structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The diffuser structure is designed with different geometric characteristics in different regions: the upstream portion has a tapered configuration to suppress backflow and extend low-flow operational range, while the downstream portion maintains a parallel configuration for simple manufacturing. This local differentiation allows the system to achieve both extended adaptability and manufacturing simplicity.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If the flow passage area is reduced to prevent backflow, then the operational range extends to low flow rates, but the high flow rate performance deteriorates

Engineering Contradiction:

Improvelow flow rate operational rangeVSAvoidhigh flow rate performance

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The diffuser flow passage is segmented into two distinct portions: an upstream tapered portion with smaller cross-sectional area to suppress backflow at low flow rates, and a downstream parallel portion with larger cross-sectional area to maintain high flow rate performance. This segmentation allows each portion to optimize for its specific operating condition without compromising the other.

Inventive Principle:

Principle #1Segmentation

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 suppresses the expansion of the backflow area on the upstream side at low flow rates, allowing the operational range to be extended to lower flow rates without deteriorating high flow rate performance.

Implementation Method 1

a centrifugal compressor, including: a housing (29) having a shroud (31s) inside; a compressor wheel (35) rotatably provided in the housing (29)

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Implementation Method 2

a ring-shaped diffuser (diffuser flow passage) that decelerates compressed fluid (compressed fluid such as compressed air) to increase its pressures

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS9874224B2Centrifugal compressor and turbocharger

Publication Date: 2018.01.23 IHI CORP

AI summary

A diffuser includes a ring-shaped parallel part, and a ring-shaped throttling part formed continuously to the inside of the parallel part in a radial direction. A wall surface of the throttling part includes a flow passage area minimum portion which makes minimal a flow passage area of the diffuser, and a ring-shaped protruding portion located closer to the outlet side of the compressor wheel than the flow passage area minimum portion, and protruding toward the flow passage of the diffuser.