Composite Turbine Blade Bulbous Root via Segmented Plates
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Solution Overview
Problem
Existing methods for manufacturing composite material blades with a bulbous root for turbomachines face challenges such as delicate production processes, machining-induced degradation of mechanical strength, and thermal shear stresses due to differential expansion between metal and composite materials.
Innovation Solution
A composite material blade with a blade root sandwiched between two independent composite material plates, forming a bulbous shape, which simplifies production, enhances mechanical strength, and eliminates thermal shear stresses by using flat interfaces and materials with high warp-to-weft ratios or unidirectional fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If an insert is added during weaving to create a raised section for the bulbous root, then the bulb shape can be formed, but the manufacturing process becomes delicate and complex
Solution Approach 1:
The blade root is divided into two separate components: a plate-shaped base and two independent plates that form the bulbous shape. This segmentation simplifies the manufacturing process by eliminating the need for complex inserts during weaving, while still achieving the desired bulb shape through assembly of simpler components.
Solution Approach 2:
The plate-shaped base is prepared in advance with a flat surface that facilitates subsequent assembly. The two independent plates are also pre-formed with their specific geometries, allowing for straightforward assembly to create the final bulbous root shape without complex in-situ forming operations.
2Shape
If the raised section is machined to final bulb shape, then the correct geometry is achieved, but fibers are cut and mechanical strength is degraded
Solution Approach 1:
The final bulb shape is achieved through assembly of pre-formed plates rather than through machining of a solid block. This preliminary formation of the shape avoids the need for post-weaving machining operations that would cut fibers and compromise mechanical strength.
Solution Approach 2:
Different regions of the blade root have different structural requirements. The plate-shaped base provides a flat mounting surface with high strength, while the two independent plates provide the bulbous geometry. Each component is optimized for its specific function, with fibers oriented to maximize strength in critical areas without requiring uniform geometry throughout.
3Shape
If metal plates are used to clamp the blade root, then the bulb shape can be formed, but thermal shear stresses occur due to differential expansion
Solution Approach 1:
All components of the blade root (the plate-shaped base and the two independent plates) are made from the same composite material with matching thermal expansion properties. This material homogeneity eliminates thermal shear stresses that would otherwise occur at interfaces between dissimilar materials during thermal cycling in turbine operation.
Solution Approach 2:
The use of composite material plates instead of metal plates provides both the necessary mechanical strength and thermal compatibility. The composite material can be engineered to have low thermal expansion and high strength-to-weight ratio, eliminating the thermal mismatch problems associated with metal-clamped configurations.
Data Source
Figure 1~4
AI summary
The invention relates to a vane (10) for a turbine engine, made of a composite material including a fiber reinforcement obtained by means of three-dimensional weaving of threads and densified by a matrix. The vane includes a blade (12) and a vane base (14) that form a single part, the vane base having two substantially planar, opposite side flanks closed between two separate composite material plates (24) that are attached onto the side flanks of the vane base such as to form a bulb-shaped vane base.