Centrifugal Compressor Scroll Casing Curvature Optimization
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Solution Overview
Problem
Centrifugal compressors experience pressure loss in the scroll passage due to sudden changes in curvature between arc portions of the scroll cross-section, which affects efficiency, and existing solutions do not adequately address this issue.
Innovation Solution
A scroll casing design with a near-circular scroll cross-section that includes multiple arc portions, where the curvature radius of the second arc portion is larger than the third arc portion, reducing the change in curvature and minimizing pressure loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the scroll cross-section is distorted to include a flatter second arc portion to guide fluid easier, then fluid guidance is improved, but the scroll cross-section deviates from circular shape causing pressure loss
Solution Approach 1:
The patent applies local quality by creating different curvature radii in different arc portions of the scroll cross-section. Specifically, the first arc portion has a first curvature radius, the second arc portion has a second curvature radius that is flatter (larger), and the third arc portion has a third curvature radius. This localized variation in curvature allows each portion to perform its specific function: the flatter second arc portion guides fluid easier while the other portions maintain pressure, collectively forming an optimized non-circular scroll cross-section.
2Shape
If most of the scroll cross-section is formed with the first arc portion and the rest with the second arc portion to make it closer to a perfect circle, then the scroll cross-section circularity is improved, but a dramatic change in curvature occurs between the arc portions causing pressure loss
Solution Approach 1:
The patent segments the scroll cross-section into three distinct arc portions with different curvature radii. The first arc portion, second arc portion, and third arc portion are clearly divided and connected. This segmentation allows each portion to have optimized curvature characteristics, avoiding the dramatic curvature change that would occur if only two arc portions with vastly different radii were used, thereby reducing pressure loss while maintaining near-circular shape.
3Loss of energy
If the difference between the first curvature radius and the second curvature radius is reduced to make the scroll cross-section close to a circle, then the change in curvature is gentle suppressing pressure loss, but further efficiency improvement is limited
Solution Approach 1:
The patent overcomes the limitation of gentle curvature changes by applying local quality differently: instead of making all arc portions have similar curvature radii, it optimizes each portion's curvature radius according to its specific function. The second arc portion has a deliberately flatter (larger) curvature radius to guide fluid easier, while the first and third arc portions have smaller curvature radii. This localized optimization achieves both pressure loss suppression and enhanced efficiency.
Data Source
AI summary
A scroll casing of a centrifugal compressor includes a scroll part forming a scroll passage of the centrifugal compressor. The scroll part has a near-circular scroll cross-section which includes a first arc portion extending from a connection position with a hub-side passage surface of a diffuser passage of the centrifugal compressor (first position) to a one-direction side (side toward fourth position), a second arc portion formed on the one-direction side of the first arc portion so as to include at least a part of a region between an outermost end in the radial direction (second position) and an innermost end in the radial direction (fourth position), and a third arc portion formed on the one-direction side of the second arc portion so as to include an end position of the scroll part on the one-direction side (fifth position) and satisfies a relationship of R2>R3, where R2 is a curvature radius of the second arc portion, and R3 is a curvature radius of the third arc portion.