Vibration Isolation for Advancing Blade Rotorcraft
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Solution Overview
Problem
Advancing blade concept rotorcraft experience excessive vibration due to counter rotating rotors combining harmonics, leading to crew fatigue, increased maintenance, and structural instability, with existing active force generators adding weight, having reliability issues, and consuming significant power.
Innovation Solution
A vibration isolation system using a dual rotor system with a Liquid Inertia Vibration Eliminator unit and active force generators to counteract multidirectional oscillations, reducing vibration transmission to the airframe, and incorporating pylon links with passive or active Liquid Inertia Vibration Eliminator units to isolate vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If counter rotating rotors are used in advancing blade concept rotorcraft, then forward airspeed capability is improved, but vibration levels increase due to combined harmonics
Solution Approach 1:
A pylon link is introduced as an intermediary component between the pylon assembly and airframe. This pylon link incorporates vibration isolation mechanisms (such as elastomeric elements or tuned mass dampers) to mediate the transmission of vibration from the counter rotating rotors to the airframe, thereby reducing the harmful vibration effects while preserving the speed capability
Solution Approach 2:
The vibration isolation system converts the harmful vibration energy from counter rotating rotors into beneficial damping through elastomeric elements or tuned mass dampers. The system absorbs and dissipates the vibrational energy that would otherwise be transmitted to the airframe, transforming the harmful harmonic combination into a controlled energy dissipation process
2Object-affected harmful factors
If active force generators are used to reduce fuselage vibration, then vibration levels decrease, but system weight increases significantly
Solution Approach 1:
The patent replaces active force generators (electromechanical systems requiring power and control) with passive vibration isolation mechanisms embedded in the pylon link. These passive mechanisms use elastomeric elements or tuned mass dampers that provide vibration reduction through mechanical properties alone, eliminating the need for complex active control systems and significantly reducing weight
Solution Approach 2:
The vibration isolation system uses simple, lightweight passive elements (elastomeric isolators or small tuned mass dampers) in the pylon link rather than expensive, heavy active force generators. These passive elements provide sufficient vibration reduction without requiring power systems, control electronics, or extensive maintenance, offering a cost-effective and lightweight solution
3Object-affected harmful factors
If active force generators are used to counteract vibration, then vibration transmission is reduced, but reliability decreases due to maintenance problems
Solution Approach 1:
The passive vibration isolation elements in the pylon link are self-service mechanisms that automatically dampen vibration without requiring external power, control systems, or maintenance. The elastomeric elements or tuned mass dampers continuously provide vibration isolation through their inherent mechanical properties, eliminating the reliability issues associated with active force generators that require power systems and control electronics
4Object-affected harmful factors
If active force generators are used to reduce vibration, then vibration levels decrease, but power consumption increases
Solution Approach 1:
The patent replaces active force generators that consume electrical power with passive mechanical vibration isolation elements in the pylon link. These passive elements use elastomeric materials or tuned mass dampers that dissipate vibration energy through mechanical damping without requiring any power input, thereby eliminating the power consumption issue entirely
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 system effectively reduces vibration in advancing blade concept rotorcraft, minimizing crew fatigue, maintenance costs, and structural instability while avoiding the drawbacks of active force generators by using a lighter, more robust, and cost-effective vibration isolation method.
Implementation Method 1
The pylon link includes a Liquid Inertia Vibration Eliminator unit operable to reduce transmission of the pylon assembly vibration to the airframe
Implementation Method 2
The active force generators include a first active force generator producing a force in a first direction and a second active force generator producing a force in a second direction different from the first direction to counteract multidirectional oscillations of the pylon assembly
Data Source
AI summary
An advancing blade concept rotorcraft includes an airframe and a pylon assembly subject to vibration. The pylon assembly includes a dual rotor system having coaxially disposed top and bottom rotor assemblies that counter rotate relative to one another. The advancing blade concept rotorcraft includes a vibration isolation system including at least one pylon link coupled to the airframe and the pylon assembly. The pylon link includes a Liquid Inertia Vibration Eliminator unit operable to reduce transmission of the pylon assembly vibration to the airframe. The advancing blade concept rotorcraft includes active force generators adjacent to the pylon assembly. The active force generators include a first active force generator producing a force in a first direction and a second active force generator producing a force in a second direction to counteract multidirectional oscillations of the pylon assembly, thereby reducing vibration of the advancing blade concept rotorcraft.