Coaxial Shaft Assembly for Aircraft Propulsion Rigidity
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Solution Overview
Problem
The existing aircraft propulsion units with boundary layer ingestion (BLI) configuration face inefficiencies due to the lack of rigidity in the nacelle, assembly of fixed blades, and fan housing, leading to significant deformations and increased fuel consumption, as the structural braces are overstressed and require larger gaps to accommodate these deformations.
Innovation Solution
The implementation of an assembly of coaxial shafts connecting the fan, fixed blades, and fan housing, along with a planetary gear train and an auxiliary fan, creates a more compact and rigid structure, reducing deformations and optimizing the gap between fan blades and the housing, while an auxiliary fan enhances pressurization at the roots of the blades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If structural braces are used to connect the nacelle and assembly of fixed blades to the fuselage, then the propulsion unit can be mounted on the rear part of the fuselage, but the substantial aerodynamic stresses cause deformation and displacement of the nacelle and assembly, requiring large gaps that negatively impact performance
Solution Approach 1:
The patent merges the nacelle, assembly of fixed blades, and fan into a single integrated unit with a common support structure. The assembly of fixed blades is directly mounted on the fan housing, and both are supported by common structural braces connected to the fuselage, creating a unified rigid structure that resists aerodynamic stresses together rather than separately.
Solution Approach 2:
The patent segments the support function by introducing separate support braces for the nacelle and for the assembly of fixed blades, with the assembly's braces connected to the fuselage rather than to the nacelle. This segmentation allows each component to be independently supported, reducing the cumulative deformation effect and improving overall rigidity.
2Reliability
If large gaps are provided between fan blades and fan housing to accommodate deformations, then friction between blades and housing is avoided, but propulsion efficiency and performance are significantly reduced
Solution Approach 1:
The patent provides beforehand cushioning by pre-loading the assembly of fixed blades against the fan housing using adjustable support braces. This pre-applied force creates initial contact or near-contact between the blade tips and housing, allowing for much smaller gaps than would be required without pre-loading, thereby maintaining propulsion efficiency while preventing friction under operational loads.
Solution Approach 2:
The patent changes the mechanical parameter of gap size from large (in conventional designs) to small (in this invention) by simultaneously changing the support structure configuration. The adjustable support braces allow precise control of the assembly's position, enabling optimization of the gap size to a minimum value that prevents friction while maximizing propulsion efficiency.
3Stability of the object's composition
If structural braces are made larger to reduce deformation, then rigidity is improved, but aerodynamic drag increases and fuel consumption rises
Solution Approach 1:
The patent segments the support function into multiple separate braces distributed around the assembly, rather than using fewer large braces. This segmentation allows each individual brace to be smaller and more aerodynamically efficient, while the collective arrangement of multiple braces provides the necessary overall rigidity and support.
Solution Approach 2:
The patent optimizes the spatial arrangement of support braces by connecting them directly to the fuselage in three-dimensional space, rather than chaining supports through intermediate structures. This dimensional optimization allows for more efficient load paths and reduced brace sizes, minimizing aerodynamic drag while maintaining structural rigidity.
Data Source
AI summary
An aircraft propulsion unit includes a drive unit with a static part and a rotary part which rotates a fan situated downstream from the drive unit, an assembly of fixed blades situated downstream from the fan, and a nacelle in which the fan and the assembly of fixed blades are accommodated. The propulsion unit also includes an assembly of at least two coaxial shafts, wherein a fan shaft connects the fan to the rotary part, and a stator blading shaft connecting the assembly of fixed blades to the static part extends concentrically, and for at least part of its length in the interior of the fan shaft. This rigid and compact configuration limits the variations of distance between the end of the fan blades and a fan housing situated in the inner duct of the nacelle.