Centrifugal Compressor Diffuser Scroll Boundary Concave Part
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Solution Overview
Problem
In centrifugal compressors, flow separation at the diffuser outlet leads to a decrease in effective flow passage area and deteriorates static pressure recovery performance, resulting in reduced compressor efficiency due to turbulence caused by low-pressure regions colliding with the main flow in the scroll.
Innovation Solution
A concave part is formed inside the radial direction in the boundary between the shroud-side wall surface of the diffuser and the scroll wall surface, allowing low-pressure regions from flow separation to be directed inward, thereby avoiding collisions with the main flow and maintaining effective flow passage area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the diffuser outlet shape is rapidly changed to increase compression ratio, then compression performance is improved, but flow separation occurs causing effective flow passage area to decrease
Solution Approach 1:
The diffuser outlet shape is divided into multiple sections along the flow direction, with each section having a different expansion angle. This segmentation allows the flow passage to be expanded in stages rather than rapidly, preventing flow separation while achieving the desired compression ratio.
Solution Approach 2:
The diffuser outlet shape is designed to dynamically adapt to flow conditions by implementing a gradual expansion profile. The expansion angle varies along the flow direction, being smaller near the outlet and larger further downstream, allowing the flow to adjust progressively rather than encountering a sudden geometric change.
2Stress or pressure
If flow separation occurs at the diffuser outlet, then static pressure recovery performance deteriorates, but compressor efficiency is reduced due to turbulence in the scroll
Solution Approach 1:
A flow guide member is introduced as an intermediary element between the diffuser outlet and the scroll inlet. This flow guide member redirects the separated flow away from the main flow path, preventing turbulence and energy loss in the scroll while maintaining static pressure recovery performance in the diffuser.
Solution Approach 2:
The flow separation that would normally cause harmful turbulence is converted into a beneficial effect by directing the separated flow into a separate region. The separated flow is redirected along the diffuser outlet wall, preventing it from colliding with the main flow in the scroll and causing energy loss.
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 solution effectively reduces turbulence and enhances static pressure recovery performance, improving compressor efficiency by keeping low-pressure regions away from the main flow, thus maintaining efficient flow velocity and pressure recovery.
Implementation Method 1
An annular diffuser (a diffuser flow passage) that decreases a velocity of a compressed fluid (a compression fluid) to thereby raise a pressure thereof
Implementation Method 2
a centrifugal compressor that compresses a fluid (gas, such as air, is included) utilizing a centrifugal force
Data Source
AI summary
An annular diffuser is formed on an outlet side of a wheel in a housing. A spiral scroll is formed on an outlet side of the diffuser in the housing. An annular concave part is formed to be depressed to an inside in a radial direction in a boundary between a shroud-side wall surface of the diffuser and a wall surface of the scroll.