Composite Gas Turbine Casing Omega Stiffener Resonance
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Solution Overview
Problem
The use of composite materials in gas turbine casings reduces overall weight but lowers resonant frequencies, leading to potential interference with fan blade wakes and the need for increased stiffness without adding weight or complexity.
Innovation Solution
A gas turbine casing with a composite material reinforcement featuring an omega-type stiffener portion that creates an annular recess, providing self-stiffening without additional dedicated stiffeners, and optionally filled with a filler or acoustic attenuation material, maintaining airflow passage continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If composite material is used for casing, then weight is reduced, but resonant frequency decreases leading to potential resonance with fan blade wakes
Solution Approach 1:
The patent applies local quality by creating a stiffener portion with a specific omega-type cross-section at a defined location on the casing. This localized structural feature increases stiffness and raises resonant frequency in the critical area without requiring the entire casing to be thicker or heavier, thus resolving the contradiction between weight reduction and resonance resistance.
Solution Approach 2:
The patent uses composite materials (fiber reinforcement densified by organic matrix) for the casing and the stiffener portion, maintaining material consistency while achieving the desired mechanical properties. The composite structure allows for tailored stiffness-to-weight ratio, enabling weight reduction while maintaining or improving resonant frequency characteristics through proper structural design.
2Reliability
If additional stiffeners are added to increase stiffness, then resonant frequency increases, but device complexity and weight increase
Solution Approach 1:
The patent merges the stiffening function with the casing structure itself by integrating the stiffener portion as an inherent feature of the composite casing during fabrication. The stiffener portion is formed as part of the fiber preform before densification, combining what would traditionally be separate components (casing and stiffeners) into a single integrated structure, thereby reducing complexity while maintaining stiffness.
Solution Approach 2:
The casing structure serves its own stiffening needs through the integrated stiffener portion formed during fabrication. The fiber preform is shaped to include the stiffener geometry, and the densification process creates the stiffening effect without requiring additional manufacturing steps or separate assembly operations, thus simplifying the overall device complexity.
3Reliability
If additional stiffeners are added to increase stiffness, then resonant frequency increases, but weight increases
Solution Approach 1:
The stiffener portion is localized to specific areas of the casing where stiffness is most needed, rather than uniformly thickening the entire casing. The omega-type cross-section provides efficient stiffness with minimal material, and the fiber preform is shaped to concentrate reinforcement only where required, thus increasing resonant frequency without proportionally increasing overall weight.
Solution Approach 2:
The use of composite materials enables high stiffness-to-weight ratio in the stiffener portion. The fiber reinforcement provides the necessary structural stiffness while the organic matrix binds the fibers, creating a lightweight but stiff structure that raises resonant frequency without the weight penalty associated with traditional metal stiffeners.
Data Source
AI summary
A gas turbine casing made of composite material from fiber reinforcement densified by a matrix. The casing includes at least one stiffener portion extending at a radius greater than the radius of upstream and downstream portions of the casing that are adjacent to the stiffener portion so as to form an annular recess in the inside surface of the casing.