Axial Compressor Blade Ring Friction Damping
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Solution Overview
Problem
Conventional stationary blade rings in axial compressors, such as those in gas turbines, face issues with notch defects and cracking due to fillet welding, leading to low damping of vibrations and limitations in thinning the blades, which affects the reliability and performance of the compressor.
Innovation Solution
A stationary blade ring design that eliminates fillet welding by using a built-up structure with divided inner and outer shroud portions coupled by band members and seal holders, allowing for easier assembly and disassembly, and providing a frictional damping effect to reduce blade vibrations and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If fillet welding is used to fix stationary blades to inner and outer shrouds, then the blades are securely fixed, but notch defects and cracking occur at the weld zones reducing reliability
Solution Approach 1:
The patent extracts and removes the welding process entirely from the stationary blade structure. Instead of using fillet welding to fix the stationary blade to the inner and outer shrouds, the invention uses a built-up structure where the blade is formed as a separate component that fits into the shroud assembly, eliminating the source of notch defects and cracking at weld zones.
Solution Approach 2:
The stationary blade structure is segmented into separate components: the stationary blade itself, the inner shroud, and the outer shroud. These segments are assembled together without welding, allowing each component to be manufactured independently and assembled through interference fits or mechanical connections that avoid crevice formation.
2Stability of the object's composition
If stationary blades are fixed by fillet welding to inner and outer shrouds, then the structure is metallurgically integral, but damping effect is low in response to vibrations
Solution Approach 1:
The patent introduces dynamic characteristics to the stationary blade structure by allowing controlled relative movement or flexibility at the blade-shroud interfaces. The built-up structure enables the blade to vibrate independently with respect to the shrouds, providing damping through friction or controlled clearance, rather than being rigidly fixed in a metallurgically integral manner.
3Strength
If stationary blades are fixed by fillet welding, then the structure is rigid, but blade thinning is limited due to overstress concerns
Solution Approach 1:
The patent applies local quality by concentrating the strength requirements at specific locations within the blade-shroud assembly rather than requiring the entire blade to be thick. The built-up structure with precise fitting and load distribution allows stress to be managed locally at the interface zones, enabling the blade airfoil portion to be thinned for improved performance while maintaining overall structural integrity.
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 enhances the reliability and performance of the compressor by eliminating cracking, improving durability, reducing the need for frequent inspections, and enabling the thinning of blades while maintaining structural integrity and damping vibrations effectively.
Implementation Method 1
providing a frictional damping effect to reduce blade vibrations and stress
Data Source
Figure 1
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Figure 3
AI summary
An inner shroud portion (3) and an outer shroud portion (4) dividedly formed per stationary blade (2) are formed integrally with each stationary blade. A plurality of the stationary blades adjacent to each other in a circumferential direction are coupled together by a band member (5) at the outer shroud portions. The inner shroud portions are held between seal holders (9, 10) which are formed as two divided members in the flowing direction of a working fluid, which are fastened by a bolt (11), and which have a length corresponding to the plurality of the stationary blades. The plurality of stationary blades, the inner and outer shroud portions, the band member, and the seal holders assembled in this manner constitute a unit (1a to 1d). A plurality of the units are connected in the circumferential direction to constitute a stationary blade ring of an axial compressor.