Composite Gas Turbine Casing Stiffening via Angular Discontinuity
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Solution Overview
Problem
Gas turbine fan casings made of composite materials face challenges in maintaining rigidity without increasing weight or size, as existing solutions like stiffeners or omega-shaped profiles lead to weight gain and complexity in installation and manufacturing.
Innovation Solution
A composite material gas turbine casing with an axisymmetric shape featuring inclined portions that meet at a vertex between a retention zone and a flange, creating a discontinuity that enhances stiffness without adding material, thereby reducing undesirable vibration modes and natural frequency resonance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If stiffeners are added to the composite material casing, then the stiffness is improved, but the weight and device complexity increase significantly
Solution Approach 1:
The invention introduces an asymmetric discontinuity in the casing profile by creating an angle between the first and second inclined portions. This angular discontinuity, positioned at a specific distance from the mean radius, breaks the symmetry of the cylindrical casing and creates stress concentration zones that enhance stiffness without requiring additional stiffener components.
Solution Approach 2:
The invention modifies the geometric parameters of the casing by creating an angular discontinuity with specific dimensions. The angle is positioned at a distance of 0.015 to 0.04 times the mean radius from the mean radius, and the inclined portions form specific angles with the axial direction. These parameter changes fundamentally alter the vibration characteristics and natural frequencies of the casing.
2Strength
If the thickness of the casing is increased locally, then the stiffness is improved, but the weight increases significantly
Solution Approach 1:
The invention applies local quality modification by creating an angular discontinuity at a specific location rather than uniformly increasing thickness. The discontinuity is positioned between the retention zone and one of the flanges, creating localized stiffness enhancement through geometric discontinuity rather than material addition.
3Strength
If an omega-shaped profile is provided to stiffen the casing, then the stiffness is improved, but the size, weight, and device complexity increase
Solution Approach 1:
The invention extracts the essential stiffening function from the complex omega-shaped profile and reduces it to a simpler angular discontinuity. By removing the unnecessary complexity of the omega shape and retaining only the critical angular feature, the invention achieves stiffness enhancement with minimal geometric modification.
4Reliability
If an angular discontinuity is created in the casing profile, then the natural frequencies are increased and vibration modes are improved, but the manufacturing complexity increases
Solution Approach 1:
The invention incorporates the angular discontinuity directly into the casing manufacturing process itself, rather than adding it as a separate post-processing step. The discontinuity is formed during the composite material fabrication by shaping the fiber preform and densification process, integrating the stiffening feature into the primary manufacturing operation.
Data Source
AI summary
A gas turbine casing made of composite material, the casing presenting an axisymmetric shape and including, in an axial direction: an upstream flange; a retention zone presenting thickness greater than the remainder of the casing; and a downstream flange. The casing presents, in section on a plane defined by the axial direction and by a radial direction, a profile including at least first and second inclined portions that are inclined relative to each other and relative to the axis of the casing. The first and second inclined portions meet at a point situated between the retention zone and one of the flanges, this point corresponding to the vertex of an angle formed by the first and second inclined portions. The distance between the vertex of the angle and the mean radius of the casing lies in the range 1.5% and 4% of the mean radius of the casing.