CMC Flow Mixer Lobed Structure Manufacturing
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Solution Overview
Problem
The existing methods for producing flow mixers in composite material with a ceramic matrix (CMC) for aeronautical turbofan gas turbine engines face challenges in creating a single-piece, non-developable lobed structure that minimizes mass while maintaining mechanical strength and reducing aerodynamic disturbances.
Innovation Solution
A method involving the production of a fibrous preform with a specific shape, assembled along connection lines extending in the flow direction, and densified with a ceramic matrix, eliminating the need for a stiffening ring and allowing for a one-piece lobed structure with reduced thickness at overlap areas to minimize flow disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-piece lobed structure is manufactured in CMC, then manufacturing complexity is reduced and mechanical strength is improved, but the aerodynamic pressure drops increase due to flow disturbances caused by assembly lines
Solution Approach 1:
The preform is divided into multiple constituent elements that are assembled along connection lines extending in the flow direction. This segmentation allows the structure to be manufactured in parts while minimizing flow disturbances, as the assembly lines are oriented to reduce aerodynamic interference.
Solution Approach 2:
The thickness of the preform is locally reduced at the connection lines where constituent elements are assembled. This local thinning minimizes the disturbance to the gas flow at critical locations, reducing aerodynamic pressure drops while maintaining structural integrity through the ceramic matrix densification.
2Strength
If a stiffening ring is added to the lobed structure, then mechanical strength is improved, but mass increases and aerodynamic performance deteriorates
Solution Approach 1:
The preform is densified by a ceramic matrix to create CMC material, which provides high mechanical strength and stiffness without the additional mass of metal stiffening rings. The composite structure inherently provides the necessary structural support.
Solution Approach 2:
The preform thickness is locally increased at specific locations to provide structural reinforcement without adding global mass. This allows the structure to maintain mechanical strength while avoiding the need for separate stiffening rings that would increase overall weight and interfere with aerodynamics.
3Ease of manufacture
If the preform is assembled along connection lines perpendicular to flow direction, then manufacturing is simplified, but aerodynamic disturbances are maximized
Solution Approach 1:
Instead of assembling the preform along traditional transverse lines, the constituent elements are assembled along connection lines that extend in the flow direction. This inverted assembly approach minimizes flow disturbances while remaining manufacturable.
Solution Approach 2:
The preform thickness is locally reduced at the connection lines to minimize flow disturbances. This local modification allows the assembly lines to be positioned optimally for aerodynamic performance while maintaining ease of manufacture through the assembly process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in a CMC flow mixer with reduced aerodynamic pressure drops and minimized flow disturbances, achieving a lightweight, mechanically strong, and aerodynamically efficient design without the need for a stiffening ring.
Implementation Method 1
densification of the fiber preform shaped and assembled, by a matrix at least partly made of ceramic
Implementation Method 2
densification of the fiber preform shaped and assembled, by a matrix at least partly made of ceramic
Data Source
Figure 1~2
Figure 3~5
Figure 6~10
AI summary
Method of manufacturing a gas turbine flow mixer lobed structure having an annular upstream part extended in the downstream direction by a part that forms a multi-lobed skirt, the method involving: producing a fibrous preform (100) using refractory fibres of a shape corresponding to that of the lobed structure that is to be manufactured, from several constituent elements of fibrous texture which are joined together or shaped using tooling of a shape corresponding to that of the lobed structure that is to be manufactured in order to obtain an assembled fibrous preform with a first preform part (111) corresponding to the annular part of the lobed structure and a second preform part (112) corresponding to the multi-lobed skirt of the lobed structure, the constituent elements of the fibrous preform being assembled at least partially along connecting lines (121) which run substantially in the direction in which the flow travels in the region of the lobes of the multi-lobed skirt preform part; and densifying the shaped and assembled fibrous preform using a matrix at least partially made of ceramic.