Centrifugal Compressor Secondary Flow Path for Surge-Limited Operation
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Solution Overview
Problem
Centrifugal compressors face efficiency challenges in low-flow rate ranges due to surge, which limits their working range.
Innovation Solution
A centrifugal compressor design featuring a secondary flow path with a throttle and fins that redirects and temporarily stores air, reducing the flow rate and pressure loss, and includes fins aligned with the impeller's leading edges to minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a secondary flow path is added to reduce surge effects, then working range in low-flow rate range is expanded, but device complexity increases
Solution Approach 1:
The secondary flow path is arranged concentrically around the primary flow path, with the diffuser of the secondary flow path nested within the housing. This nesting arrangement allows the secondary flow path to be integrated into the existing compressor structure without requiring additional external components, thereby expanding working range while minimizing increases in device complexity.
Solution Approach 2:
The secondary flow path serves multiple functions: it provides an alternative flow route during surge conditions to stabilize operation, acts as a pressure relief path, and can function as part of the overall compression system. This multi-functionality allows a single structural addition to address multiple performance requirements simultaneously.
2Adaptability or versatility
If air flows backward in primary flow path during low-flow rate, then surge occurs limiting working range, but efficiency in low-flow rate range deteriorates
Solution Approach 1:
The invention converts the harmful backward flow during surge into a beneficial effect by providing a controlled secondary flow path. The backward-flowing air that would normally cause surge instability is redirected through the secondary flow path with its throttle and diffuser, transforming the harmful surge phenomenon into a controlled flow redistribution that stabilizes operation and actually improves efficiency in low-flow rate ranges.
Solution Approach 2:
The secondary flow path acts as an intermediary between the primary flow path's inlet and outlet. During surge conditions, it mediates the pressure imbalance by providing an alternative route for air to flow from the outlet side back to the inlet side, reducing the severity of surge oscillations and improving overall system efficiency in low-flow rate operation.
3Loss of energy
If throttle is added to secondary flow path to control flow, then pressure loss is reduced, but device complexity increases
Solution Approach 1:
The throttle is merged with the diffuser structure of the secondary flow path, forming an integrated component rather than a separate element. The diffuser blades themselves create the throttling effect through their geometry and arrangement, combining the flow control function with the existing pressure recovery structure, thereby reducing pressure loss without proportionally increasing device complexity.
Solution Approach 2:
The throttle is positioned specifically at the inlet of the secondary flow path where flow control is most critical. The diffuser blades are arranged with specific angles and spacing in this localized region to create the throttling effect, while the rest of the secondary flow path maintains a simpler structure optimized for pressure recovery. This localized application of complexity achieves pressure loss reduction without overall structural over-engineering.
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
Improves efficiency in both low- and high-flow rate ranges by extending the working range and reducing pressure and flow losses through the secondary flow path configuration.
Implementation Method 1
a part of air pressurized by the compressor impeller may flow backward
Implementation Method 2
the secondary flow path including an throttle that is continuous with the first end and that is narrowed toward the first end
Data Source
AI summary
A centrifugal compressor includes: an impeller; and a housing that accommodates the impeller, the housing including: a primary flow path that accommodates the impeller; and a secondary flow path that surrounds the primary flow path in a cross-section perpendicular to an axial direction of the impeller, the secondary flow path including: a first end that opens to the primary flow path at a position upstream of the impeller in a flow of air in the primary flow path; and a second end that opens to the primary flow path at a position downstream of the first end, the first end opening to the primary flow path in a direction opposite to the impeller in the axial direction of the impeller, the second flow path including a throttle that is continuous with the first end and that is narrowed toward the first end.