Variable Pitch Airfoil Damping Element for Open Fan Rotor
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Solution Overview
Problem
Variable pitch open rotor fans experience high vibrations due to flutter, fan blade wakes, and engine core vibrations, which traditional damping technologies cannot effectively address, as they do not allow for blade pitch change.
Innovation Solution
The implementation of a damping element placed in the outer periphery of the blade platform, utilizing centrifugal loading to dampen motion between the blade platform and the hub disk, allowing for pitch change while providing sufficient damping for fundamental modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional damping technologies are used, then vibration damping is provided, but blade pitch change is not allowed
Solution Approach 1:
The damping system is segmented into multiple independent damping elements distributed around the blade platform perimeter, allowing the blade to rotate for pitch change while each damping element independently provides vibration damping through friction contact
Solution Approach 2:
A damping element is introduced as an intermediary component between the blade platform and the disk, utilizing friction contact to damp vibrations while allowing rotational movement for pitch change
2Reliability
If damping elements are added to provide vibration damping, then device complexity increases, but the solution should be retrofittable without changing existing blade components
Solution Approach 1:
The damping system is divided into discrete, independent damping elements that can be individually installed around the blade platform perimeter, allowing incremental installation without redesigning the entire blade structure
Solution Approach 2:
The damping elements are designed as simple, low-cost friction-based components that can be easily manufactured and installed, prioritizing simplicity and retrofittability over complex integrated solutions
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 solution effectively reduces vibrations, allowing for blade pitch change while being a low-cost, passive, retrofittable device that does not require changes to existing blade components, providing efficient damping for variable pitch fan blades.
Implementation Method 1
provide vibration damping by friction between the damping element, the platform, and the disk
Implementation Method 2
utilizing centrifugal loading to dampen motion between the blade platform and the hub disk
Data Source
AI summary
A variable pitch airfoil assembly for an engine includes a disk having an annular shape extending about an axial direction and an airfoil coupled to the disk via a platform. The airfoil extends outwardly from the disk in a radial direction and is rotatable relative to the disk about a pitch axis. The variable pitch airfoil assembly further includes a damping element positioned at least partially within the disk exterior of and adjacent to a perimeter of the platform so as to provide vibration damping by friction between the damping element, the platform, and the disk while also allowing for a pitch change of the airfoil.