Centrifugal Compressor Scroll Passage Concave Arc Design
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Solution Overview
Problem
Centrifugal compressors face efficiency issues in low flow rate operating points due to separation in the scroll passage, which is caused by swirl flows interfering with compressed air discharged from the diffuser passage.
Innovation Solution
The centrifugal compressor design includes a scroll passage with a specific cross-sectional shape where the inclination angle of the concave arc portion has a minimum value in the range of 30° to 120°, reducing interference between swirl flows and compressed air from the diffuser passage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the scroll passage has a conventional smooth spiral shape, then the manufacturing is simple, but separation occurs in the scroll passage at low flow rate operating points due to swirl flow interference
Solution Approach 1:
The invention applies local quality by introducing concave arc portions only in specific regions of the scroll passage where swirl flow interference occurs, rather than changing the entire scroll passage geometry. The concave arc portions are positioned at specific angular intervals (30° to 120° from the tongue) to locally modify the flow characteristics and reduce separation, while maintaining the overall simple spiral shape for ease of manufacturing.
Solution Approach 2:
The invention uses curvature by forming concave arc portions with specific curvature radii in the scroll passage wall. These curved portions create favorable flow patterns that reduce swirl flow interference and prevent separation. The concave curvature modifies the flow trajectory of compressed air, allowing it to follow the wall surface more smoothly without separating from the passage.
2Reliability
If the inclination angle of the concave arc portion is increased to reduce separation, then the efficiency improves, but the manufacturing precision requirements increase
Solution Approach 1:
The invention optimizes parameters by specifying particular ranges for the inclination angle (30° to 120° from the tongue) and curvature radius of the concave arc portions. These parameter ranges are determined to achieve the best balance between reducing separation and maintaining manufacturability. By defining specific parameter ranges rather than exact values, the invention allows for manufacturing tolerances while still achieving the desired flow control effects.
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 reduces separation in the scroll passage, thereby improving the efficiency of the centrifugal compressor in low flow rate operating points.
Implementation Method 1
compressed air discharged from a diffuser passage in the vicinity of a tongue of a scroll part forming the scroll passage swirls and flows through the scroll passage along the inner wall surface of the scroll passage
Implementation Method 2
separation occurs by a factor other than the recirculation flow described in Patent Document 1. More specifically, compressed air discharged from a diffuser passage in the vicinity of a tongue of a scroll part forming the scroll passage swirls and flows through the scroll passage along the inner wall surface of the scroll passage
Data Source
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AI summary
An inclination angle between a direction perpendicular to a rotational axis and a tangential direction of a radially outer edge of a radially outermost concave arc portion, which is located outermost in the radial direction of an impeller among at least one concave arc portion, has a distribution along the circumferential direction of a scroll passage, and when a circumferential position in the scroll passage from a tongue of a scroll part to an outlet of the scroll passage is represented by a central angle about the rotational axis by using the tongue as a reference, the distribution of the inclination angle has a local minimum value or a minimum value in a range of the central angle of 30° to 210°.