Compressor Cover Diffuser Radius Layout for Backflow Suppression
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Solution Overview
Problem
Centrifugal compressors experience local low speed regions and backflow in the diffuser flow path due to asymmetric scroll flow paths, leading to reduced efficiency and a limited operating range when the diffuser radius is reduced to mitigate these issues.
Innovation Solution
An annular compressor cover is designed with varying diffuser radii, where the average radius from 0° to 180° is smaller than from 180° to 360° in the circumferential direction, and the diffuser radius is cut eccentrically to form a diffuser flow path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the diffuser radius is reduced to suppress local low speed region and backflow, then the operating range is expanded to low flow rate side, but the pressure recovery is suppressed and compressor efficiency is reduced
Solution Approach 1:
The patent applies local quality by making the diffuser radius variable in the circumferential direction. Specifically, the diffuser radius is set to be smaller in the region corresponding to the asymmetric part of the scroll flow path (where backflow occurs) and larger in other regions. This localized variation allows suppression of backflow where needed while maintaining pressure recovery in other areas, thus resolving the contradiction between expanding operating range and maintaining compressor efficiency.
2Reliability
If the diffuser radius is uniformly reduced, then backflow in diffuser flow path is suppressed, but pressure recovery is reduced and efficiency is lowered
Solution Approach 1:
Instead of uniformly reducing the diffuser radius, the patent implements a non-uniform distribution where the radius is selectively reduced only in the circumferential region corresponding to the asymmetric scroll flow path. This localized approach ensures backflow suppression is achieved where the asymmetric geometry causes problems, while other regions maintain sufficient radius for effective pressure recovery.
Solution Approach 2:
The patent utilizes asymmetry by deliberately creating an asymmetric diffuser radius distribution that mirrors the asymmetric scroll flow path geometry. The diffuser radius is designed to be smaller in the asymmetric region and larger in symmetric regions, creating a coordinated asymmetric-diffuser configuration that addresses backflow issues while preserving overall pressure recovery characteristics.
Data Source
AI summary
Provided is an annular compressor cover forming a passage wall of a diffuser passage in a centrifugal compressor, wherein, when the end-of-winding position of a scroll passage of the centrifugal compressor is defined as the 360° position of the compressor cover in the circumferential direction, the direction in which a fluid flows through the scroll passage in the circumferential direction is defined as the positive direction of positions in the circumferential direction, and the distance between outlets of the diffuser passage at each position in the circumferential direction and the central axis of the inner circumferential surface of the compressor cover is defined as the diffuser radius, the average value of the diffuser radius in a range up to 180° from the position of a tongue section of the scroll passage in the circumferential direction is smaller than the average value of the diffuser radius in a range from 180° to 360° in the circumferential direction.