Composite Vane Dovetail Mounting Preload
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Solution Overview
Problem
Existing mounting systems for composite airfoils in aircraft gas turbine engines lack the necessary robustness and longevity, which is crucial for enhancing the life of both the airfoils and the fan frame assembly, particularly in bypass gas turbine engines where structural stiffness and weight reduction are desired.
Innovation Solution
A dovetail root system is used, where a composite airfoil is secured with a dovetail root that fits into a dovetail slot in an inner vane mount, utilizing biasing means such as jack screws, axially curved flat springs, or transversely curved flat springs to preload the crush faces, ensuring secure and durable attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal materials are used for fan struts and outlet guide vanes, then structural stiffness is improved, but weight increases
Solution Approach 1:
The patent applies composite materials to manufacture outlet guide vane assemblies, replacing traditional metal materials. This substitution maintains the required structural stiffness while significantly reducing the weight of the engine components, thereby resolving the contradiction between strength and weight.
2Reliability
If existing mounting systems are used for composite airfoils, then manufacturing simplicity is maintained, but reliability and longevity are insufficient
Solution Approach 1:
The mounting system is segmented into distinct components including a dovetail root attached to the composite airfoil, a dovetail slot in the fan frame assembly, and separate biasing means. This segmentation allows each component to be optimized for its specific function while collectively providing enhanced reliability and longevity.
Solution Approach 2:
The biasing means applies a preliminary preload force to the dovetail root before operational loads are applied. This preliminary action ensures proper seating and contact of the crush faces, preventing misalignment and enhancing the durability and reliability of the mounting system throughout its service life.
3Reliability
If a secure mounting system is implemented for composite airfoils, then reliability is improved, but device complexity increases
Solution Approach 1:
The dovetail root and dovetail slot act as intermediary elements between the composite airfoil and the fan frame assembly. These intermediaries provide a specialized mechanical interface that enhances reliability through positive engagement and load distribution, while the modular nature of the intermediary components keeps the overall system complexity manageable.
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
The proposed solution provides a robust and secure mounting system for composite airfoils, enhancing their life and the structural integrity of the fan frame assembly, while allowing for the use of lighter composite materials, thereby improving fuel efficiency and reducing weight.
Implementation Method 1
A vane includes a composite airfoil, a single dovetail root connected to the composite airfoil, a dovetail slot in an inner vane mount, and a biasing means for urging the root bottom of the dovetail root away from the slot bottom along the dovetail slot and pressing and preloading the flat dovetail root pressure and suction side crush faces of the dovetail root against the slot pressure and suction side slot crush faces
Data Source
AI summary
A vane includes a composite airfoil having a single dovetail root extending chordwise between or near leading and trailing edges of the airfoil. The root is connected to the airfoil and is slidably received in a dovetail slot in an inner vane mount. The dovetail slot has a triangular slot cross section and a flat slot bottom and flat slot pressure and suction side crush faces corresponding to pressure and suction sides of the airfoil. The root has a triangular root cross section, a flat root bottom, and flat dovetail root pressure and suction side crush faces. A biasing means urges the root bottom of the dovetail root away from the slot bottom and presses and preloads the dovetail root pressure and suction side crush faces against the slot pressure and suction side slot crush faces.