Lead-lag Damper With Adjustable Orifice for Rotor Hubs
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Solution Overview
Problem
Current lead-lag dampers for rotor hubs do not provide the desired damping characteristics or required exterior dimensions for all applications, particularly in managing oscillating chordwise forces experienced by aircraft rotor blades during flight.
Innovation Solution
The implementation of a fluid-shear damper with an adjustable orifice device and a soft static spring rate, mounted outside the blade grip, which allows for larger damper size and smaller aperture in the yoke arms, and can be retrofitted to existing rotor assemblies, providing effective damping of in-plane motion through fluid restriction and thermal expansion management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing elastomeric or hydraulic dampers are used, then damping function is provided, but desired damping characteristics and required exterior dimensions cannot be achieved for all applications
Solution Approach 1:
The damper incorporates an adjustable orifice device that allows dynamic adjustment of the damping coefficient by changing the orifice area. This enables the same damper structure to adapt to different damping requirements across various applications, resolving the contradiction between providing reliable damping characteristics and achieving versatility for all applications.
Solution Approach 2:
The damping coefficient is made variable through the adjustable orifice mechanism. By changing the orifice area parameter, the damper can achieve different damping characteristics without changing the physical structure, thereby maintaining reliability across diverse applications while achieving adaptability.
2Reliability
If larger damper size is used, then effective damping is achieved, but aperture size in yoke arms must be larger
Solution Approach 1:
The damper is mounted outside the blade grip rather than inside the yoke arm aperture. This dimensional repositioning allows the damper to achieve its full size for effective damping without requiring large apertures in the yoke arms, as the damper occupies space in a different dimension (external mounting location).
3Ease of operation
If discrete lead-lag hinges or flexible yokes are used, then lead-lag motion is provided, but additional damping components are required
Solution Approach 1:
The lead-lag hinge and damper are combined into a single integrated component. The hinge mechanism incorporates the damping function directly, eliminating the need for separate damping components. This merging maintains the lead-lag motion capability while reducing overall device complexity.
Solution Approach 2:
The hinge component is designed to perform multiple functions: providing lead-lag motion and providing damping. This multi-functionality eliminates the need for additional dedicated damping components, thereby reducing device complexity while maintaining operational ease.
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 dampens lead-lag motion of rotor blades, allowing for improved stress relief on rotor components and adaptability to various applications, including existing systems, by optimizing fluid flow and structural design.
Implementation Method 1
fluid-shear damper with an adjustable orifice device... providing effective damping of in-plane motion through fluid restriction
Implementation Method 2
soft static spring rate... and thermal expansion management
Data Source
AI summary
A lead-lag damper for a rotor assembly has a body mounted to either an inboard portion of a blade assembly or a fixed portion of the rotor assembly. A piston carried within the body is configured to allow for relative motion between the body and the piston. The piston defines opposing chambers within the body, the chambers being in fluid communication through a fluid passage. A link connects the piston to the other of the inboard portion of the blade assembly and the fixed portion of the rotor assembly, and the link engages a central portion of the piston. The piston acts on fluid in the chambers during relative motion between the piston and the body and causes fluid flow between the chambers through the fluid passage. Flow through the passage acts to damp lead-lag motion of the blade assembly relative to the fixed portion of the rotor assembly.