Bonded Skins for Ducted-Rotor Aircraft Tip-Gap Control
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Solution Overview
Problem
Maintaining tight tip-gap tolerances in ducted-rotor aircraft is challenging due to variations in cross-sectional thickness of components, which can lead to non-uniformity and degraded performance.
Innovation Solution
Adhesively bonding aerodynamic skins with varying adhesive bondline thicknesses to account for tolerance stackups and maintain uniformity of the tip gap between rotor blades and duct surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional bonding methods with uniform adhesive thickness are used, then manufacturing process is simple, but tip-gap uniformity deteriorates due to tolerance stackups
Solution Approach 1:
The patent applies local quality by varying the adhesive bondline thickness at different locations around the duct cross-section. Specifically, the adhesive thickness is adjusted based on the local tolerance stackups of the skin and spar components, allowing tighter tolerances at critical locations and more relaxed tolerances elsewhere. This non-uniform adhesive distribution compensates for manufacturing variations and maintains consistent tip-gap clearance throughout the rotor assembly.
Solution Approach 2:
The patent changes the parameter of adhesive bondline thickness from a uniform value to a spatially varying value. By modifying this geometric parameter across different locations, the invention compensates for tolerance stackups in the skin and spar thicknesses. The adhesive thickness is specifically increased in regions where tolerance accumulation would otherwise create excessive tip-gap variation, thereby maintaining overall tip-gap uniformity.
2Reliability
If tight tip-gap tolerances are enforced uniformly, then rotor performance improves, but manufacturing difficulty increases due to cumulative tolerances
Solution Approach 1:
The patent applies local quality by differentiating tolerance requirements across different locations. Instead of enforcing uniform tight tolerances on skin and spar thicknesses around the entire duct, the invention allows varying local tolerances that are relaxed in non-critical areas. The adhesive bondline thickness is adjusted locally to compensate, ensuring that tip-gap uniformity is maintained only where it critically affects rotor performance, thereby reducing overall manufacturing difficulty.
Solution Approach 2:
The adhesive bondline acts as an intermediary element that absorbs and compensates for tolerance variations in the skin and spar components. By allowing the adhesive thickness to vary, it serves as a buffer that decouples the tight tip-gap requirement from the manufacturing tolerances of individual components. This intermediary approach enables relaxed component tolerances while still achieving the desired rotor performance.
3Manufacturing precision
If cross-sectional thickness variations of components are reduced, then tip-gap uniformity improves, but manufacturing cost and complexity increase
Solution Approach 1:
The patent changes the parameter of adhesive bondline thickness from uniform to spatially varying to compensate for component thickness variations. Instead of requiring all skin and spar components to have tightly controlled thicknesses, the invention allows broader thickness tolerances and uses the adhesive layer as a compensating mechanism. This parameter change shifts the precision requirement from the structural components to the adhesive application process, which is easier to control.
Solution Approach 2:
The patent replaces the mechanical precision requirement (tight control of skin and spar thicknesses) with a chemical/process-based solution (controlled adhesive application). Instead of relying on mechanical tolerancing of structural components, the invention uses the adhesive bondline thickness as the primary control variable for achieving tip-gap uniformity. This substitution reduces the complexity of component specifications while maintaining the desired precision in the final assembly.
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 improves the performance characteristics of ducted-rotor aircraft by ensuring consistent tip-gap uniformity, enhancing thrust and overall efficiency.
Implementation Method 1
adhesively bonding aerodynamic skins with varying adhesive bondline thicknesses
Data Source
AI summary
A duct for a ducted-rotor aircraft may include an internal structure and an aerodynamic exterior skin that is adhesively bonded to the internal structure. The skin may include a leading-edge portion disposed at an inlet of the duct and an inner portion disposed along an interior of the duct. The inner portion of the skin may be bonded to the internal structure with a first bondline of adhesive and the leading-edge portion of the skin may be bonded to the inner portion of the skin with a second bondline of adhesive. One or both of the first and second bondlines of adhesive may be of non-uniform thickness to take up tolerance stackups between the inner portion of the skin, the leading-edge portion of the skin, and the internal structure.