Rotor Vibration Isolation via Elastomeric Bearings
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Solution Overview
Problem
Rotor aircraft experience significant ride vibrations due to oscillations caused by the transfer of lift from the rotor to the wings during high-speed cruise, which are exacerbated by reduced rotor RPM, and increasing the number of blades complicates storage and adds weight.
Innovation Solution
A rotor aircraft design featuring a fuselage with a rotor shaft that allows vertical and horizontal movement, utilizing elastomeric bearings and pneumatic damping to isolate rotor oscillations from the airframe, enabling a two-bladed rotor to operate efficiently at low RPM during high-speed flight without the need for complex blade folding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the rotor speed is reduced during high-speed cruise to decrease drag, then fuel efficiency and cruising speed are improved, but rotor oscillations become more noticeable and cause significant ride vibrations
Solution Approach 1:
The patent introduces an intermediary isolation assembly between the rotor system and the airframe that mediates the transmission of oscillations. This assembly includes elastic elements and dampers that absorb and attenuate the vibration forces generated by the rotor, preventing them from being transmitted to the fuselage and passengers while allowing the rotor to operate at reduced speeds for improved fuel efficiency
Solution Approach 2:
The patent converts the harmful rotor oscillations into a beneficial isolation mechanism by using the elastic elements and dampers to absorb the vibration energy. The isolation assembly transforms the harmful vibrational forces into elastic deformation and heat dissipation, thereby protecting the airframe and passengers from the harmful effects while maintaining the advantage of reduced rotor drag at cruise speeds
2Object-affected harmful factors
If the number of rotor blades is increased to reduce oscillation amplitude, then ride comfort is improved, but device complexity and weight increase
Solution Approach 1:
The patent extracts the vibration reduction function from the rotor blade configuration itself and places it in a separate isolation assembly. Instead of modifying the rotor blades to reduce oscillations, the invention removes the problem source by isolating the rotor system from the airframe using elastic elements and dampers, thereby maintaining the simplicity of the two-bladed rotor configuration while achieving vibration reduction
3Object-affected harmful factors
If the number of rotor blades is increased to three or four blades, then oscillation frequency increases and ride comfort improves, but storage compactness deteriorates due to the need for blade folding
Solution Approach 1:
The patent extracts the vibration control function from the rotor blade design and implements it through a separate isolation assembly with elastic elements and dampers. This allows the rotor to maintain a simple two-bladed configuration that can be stored compactly without folding, while the isolation assembly handles the vibration and frequency control that would otherwise require additional blades
4Object-affected harmful factors
If elastomeric bearings and pneumatic damping are used to isolate rotor oscillations, then ride vibrations are reduced, but device complexity increases
Solution Approach 1:
The patent merges the vibration isolation function with the existing rotor support structure by integrating elastomeric bearings and pneumatic damping elements into the rotor hub and support arms. This combination approach allows the isolation mechanism to be incorporated into the existing design without adding separate complex systems, thereby reducing vibrations while minimizing the increase in device complexity
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 design effectively reduces passenger discomfort by minimizing rotor vibrations, allowing a two-bladed rotor to operate at low RPM during high-speed flight while maintaining compact storage capabilities, particularly beneficial for aircraft carriers with limited space.
Implementation Method 1
One method of accomplishing this movement is to use elastomeric bearings with good dampening characteristics located on either side of the gearbox
Implementation Method 2
elastomeric bearings with good dampening characteristics
Implementation Method 3
piston seal friction
Implementation Method 4
fluid flow through an orifice
Data Source
AI summary
A rotor aircraft has a fuselage with a rotor mounted above by a rotor shaft. An arm is pivotally engaged with a lower portion of the rotor shaft and pivotally engaged with the fuselage, enabling the rotor to move with little restriction vertically and horizontal in all directions relative to the fuselage as the rotor rotates in order to isolate rotor oscillations. An infinitely variable air spring is used to counter vertical and fore and aft loads. Damping in the form of elastomeric materials, piston seal friction, and fluid flow through an orifice may be added as required.