Composite Turbomachine Blade Root Attachment for Bending Stiffness
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Solution Overview
Problem
Existing blade fixing systems for turbomachines, particularly those using composite material blades, face issues with geometric modifications that affect stress distribution and rigidity, leading to reduced bending stiffness and torsion resistance.
Innovation Solution
A blade preform made of three-dimensionally woven composite material with a specific geometry and attachment elements that maintain stress within the weaving plane, enhancing quadratic moment and stiffness through spaced-apart blade root portions and flared attachment elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a blade root is formed with a 90° angle (clamping fixing geometry), then the quadratic moment and bending stiffness are increased, but out-of-plane stresses are generated that can prove limiting for composite technologies
Solution Approach 1:
The blade root is segmented into two separate portions (first and second portions) that are spaced apart from each other, creating a cavity between them. This segmentation allows the blade root to maintain high quadratic moment for bending stiffness while keeping all stresses within the plane of the airfoil, avoiding out-of-plane stresses that are limiting for composite materials.
2Stress or pressure
If a tangential fixing geometry is used, then out-of-plane stresses are avoided and stresses remain in the plane of the airfoil, but the quadratic moment is reduced making the structure much less rigid and resistant
Solution Approach 1:
The invention introduces a new spatial dimension by spacing the two blade root portions apart from each other in the direction perpendicular to the airfoil plane. This creates a cavity and increases the quadratic moment without generating out-of-plane stresses, as the spacing is achieved through the three-dimensional woven material structure rather than through out-of-plane loading.
3Strength
If the blade root portions are spaced apart to increase quadratic moment, then bending stiffness is enhanced, but the structural complexity and manufacturing difficulty increase
Solution Approach 1:
The invention utilizes three-dimensionally woven composite material to create the blade root structure with two spaced-apart portions. This composite material approach allows the complex geometry of spaced root portions forming a cavity to be manufactured as a monolithic structure without requiring separate components or complex assembly, thus enhancing bending stiffness while managing structural complexity through material integration.
Data Source
AI summary
A system including: a blade including, at the level of the blade root, two portions spaced apart from each other in the transverse direction X so as to provide therebetween a cavity extending downwards in the direction Y of the height of the blade, from a cavity bottom to a cavity opening on the outside, located at the level of the lower end of the blade root, an attachment element of the blade partially engaged inside the cavity, the engaged part having a shape, taken in a plane defined by the directions X and Y, which extends towards the bottom while flaring out in the direction X, the two spaced apart portions of the blade root which are in contact with the flared shape of the attachment element having corresponding flared shapes.