Composite Blade Preform with Set-Back Zone for Weight Reduction
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Solution Overview
Problem
Current composite blades for turbojet engines face challenges in reducing weight while maintaining mechanical strength, as increasing blade span leads to increased weight and mechanical strength issues, necessitating a more efficient design for large-span blades.
Innovation Solution
A fibrous preform for composite blades is created using a 3D weaving technique with a set-back zone of reduced thickness, allowing for lighter materials to be used in less mechanically loaded areas, maintaining structural integrity in loaded areas, and incorporating a filler block with lower density to reduce overall weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the blade span is increased to increase rotor diameter, then the thrust and efficiency of the engine increase, but the weight of the rotating machine increases
Solution Approach 1:
The blade is designed with varying thickness along its span, with the root portion maintaining greater thickness for structural strength while the tip portion having reduced thickness to minimize weight. This local differentiation of material distribution allows the blade to achieve both the structural integrity needed for large span and the weight reduction necessary for efficient rotation.
Solution Approach 2:
The blade employs composite material construction combining multiple materials with different properties - denser materials in the root for strength and lighter materials in the tip for weight reduction. This composite approach enables the blade to simultaneously satisfy the conflicting requirements of structural strength and weight minimization.
2Length of stationary object
If the blade span is increased, then the rotor diameter increases, but the natural frequencies of the blades decrease requiring increased thickness
Solution Approach 1:
The blade features non-uniform thickness distribution along its span, with thicker sections at the root where structural strength and natural frequency requirements are critical, and thinner sections toward the tip where these requirements are less stringent. This localized variation in geometry allows the blade to maintain adequate natural frequencies while achieving large span.
Solution Approach 2:
The blade design transitions from a uniform cross-section to a variable cross-section along the span dimension, introducing geometric variation in the third dimension. This dimensional change allows the blade to optimize its structural properties at different locations along its length, maintaining strength where needed while reducing weight where possible.
Data Source
AI summary
Fibrous preform for a composite blade and also a composite blade formed by means of such a preform, a rotor and a rotating machine comprising such a blade, the preform comprising a first longitudinal section, configured to form a blade root, and a second longitudinal section, extending from the first longitudinal section, configured to form a portion of an airfoil, wherein the first longitudinal section has a first thickness at its upper end and wherein the second longitudinal section comprises at least one set-back zone having a thickness at least three times less than the first thickness, said set-back zone occupying at least 50% of the second longitudinal section.