Centrifugal Compressor Shroud Openings for Blade Vibration Reduction
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Solution Overview
Problem
Centrifugal compressors in gas turbines experience undesirable vibrations in impeller blades due to periodic pressure distribution fluctuations at the impeller outlet and diffuser inlet, which can lead to durability issues and potential damage.
Innovation Solution
The design incorporates a shroud with alternating first and second openings at specific intervals, creating an angular phase difference that equalizes pressure variations along the circumference, reducing vibrations and enhancing rotor blade durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If small openings are provided at the same pitch as impeller blades in the diffuser inlet portion, then pressure equalization is attempted, but the periodic pressure distribution cannot be effectively equalized and impeller blade vibration is not prevented
Solution Approach 1:
The diffuser inlet portion is segmented into multiple zones with different opening arrangements. First openings are arranged at the same pitch as impeller blades, while second openings are arranged at a different pitch. This segmentation allows different regions to serve different functions in pressure equalization, effectively reducing periodic pressure fluctuations and preventing impeller blade vibration.
Solution Approach 2:
Different opening configurations are applied to different local regions of the diffuser inlet portion. The first openings are positioned to align with impeller blade passages for primary pressure equalization, while second openings are positioned at intermediate locations to provide additional equalization at different phases. This local differentiation enables comprehensive suppression of pressure fluctuations throughout the circumferential direction.
2Reliability
If openings are provided in the shroud adjacent to the impeller outlet portion, then pressure fluctuations can be reduced, but the structural integrity of the shroud may be compromised
Solution Approach 1:
The shroud is designed with openings that allow pressure equalization while maintaining structural integrity. The openings are strategically positioned and sized to provide sufficient pressure equalization effect without creating weak points that would compromise the shroud's structural strength. The communication passages connect these openings to form a distributed pressure equalization system that preserves overall structural rigidity.
3Reliability
If multiple rows of openings with different pitches are provided in the shroud, then pressure equalization effectiveness is improved, but manufacturing complexity increases
Solution Approach 1:
The opening pattern is segmented into two distinct sets: first openings arranged at the same pitch as impeller blades, and second openings arranged at a different pitch. This segmentation simplifies the manufacturing process by allowing each set to be positioned and sized independently, rather than requiring a complex single-pattern arrangement. The segmented approach makes the manufacturing process more manageable while achieving superior pressure equalization.
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 configuration effectively reduces pressure fluctuations and minimizes rotor blade vibrations, thereby improving the durability of the impeller blades and preventing damage.
Implementation Method 1
a communication passage (82) communicating the openings (80) with one another, the openings including first openings (80A) that are arranged at a same interval as the stator vanes, and second openings (80B) arranged intermediately between the adjacent first openings
Data Source
AI summary
In a centrifugal compressor including an impeller (70) having rotor blades (74), a shroud (72) surrounding the impeller, and a diffuser (76) having stator vanes (78), the shroud (72) includes a plurality of openings (80) opening toward the impeller (70) in a part thereof adjacent to an impeller outlet portion (42B), and a communication passage (82) communicating the openings (80) with one another, the openings including first openings (80A) that are arranged at a same interval as the stator vanes, and second openings (80B) arranged intermediately between the adjacent first openings.