Fluidic Vibration Damper for Turbomachine Rotor Blades
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Solution Overview
Problem
Conventional vibration damping methods for turbomachine rotor blades, such as shrouds, increase weight and cost while causing aero performance losses and high aeroelastic flutter instability, and are ineffective for aft-stage blades with short shanks.
Innovation Solution
A vibrational dampening element with a mass enclosed in a casing and filled with fluid, featuring a fluidic chamber with accumulator portions and a primary passage, is attached to the rotor blade to adjust and dampen oscillations without the need for shrouds, utilizing fluid dynamics to counteract vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shrouds are used for vibration damping, then vibrational damping is provided, but weight increases and aerodynamic efficiency decreases
Solution Approach 1:
The patent replaces the mechanical shroud structure with a fluid-based vibration damping system. A fluid chamber is created within the blade structure, containing a fluid that responds to vibrational movements. The fluid's inertia and viscosity provide damping forces without requiring additional mechanical structures like shrouds, thereby eliminating the weight penalty while maintaining vibration control.
Solution Approach 2:
The invention utilizes a hydraulic approach by incorporating a fluid chamber filled with fluid that interacts with vibrational movements. The fluid's physical properties (density, viscosity) are leveraged to provide damping forces during blade oscillation. This hydraulic mechanism replaces solid mechanical damping structures, achieving vibration control without the weight and aerodynamic drag of traditional shrouds.
2Reliability
If shrouds are used for vibration damping, then vibrational damping is provided, but aerodynamic efficiency is reduced
Solution Approach 1:
The patent substitutes mechanical shroud structures with an internal fluid-based damping system. By placing the fluid chamber inside the blade structure rather than adding external shrouds, the aerodynamic flow path remains unobstructed. The fluid provides damping forces through its physical response to vibration without creating aerodynamic drag or blocking the flow path, thus preserving aerodynamic efficiency.
Solution Approach 2:
The invention nests the fluid chamber within the existing blade structure. The fluid damping system is integrated into the blade's internal volume rather than being added as an external component. This nesting approach allows the damping mechanism to occupy space that would otherwise be unused, eliminating the need for external shrouds that would interfere with aerodynamic flow.
3Reliability
If tip shrouds are used for vibration damping, then damping is provided, but tip losses increase due to large tip fillet requirements
Solution Approach 1:
The fluid chamber is nested within the blade structure away from the tip region, eliminating the need for large tip fillets. By internalizing the damping mechanism, the blade tip geometry can be optimized for aerodynamic flow without the stress-concentration-reducing fillets that large shrouds would require. This preserves the aerodynamic efficiency at the blade tip while still providing vibration damping through the internal fluid system.
4Reliability
If part-span shrouds are used for vibration damping, then damping is provided, but flow path blockage increases reducing aero efficiency
Solution Approach 1:
The fluid damping chamber is nested within the blade structure, occupying internal volume rather than protruding into the flow path. This internal placement eliminates the flow blockage that would occur with external part-span shrouds. The fluid provides damping forces through its response to vibration while the blade's external geometry remains smooth and aerodynamic, preventing flow separation and maintaining efficiency.
5Reliability
If tip shrouds are used for vibration damping, then damping is provided, but aeroelastic flutter instability increases
Solution Approach 1:
The patent replaces rigid mechanical shroud connections with a fluid-based damping system that is integrated into the blade structure. The fluid's ability to move and deform allows it to absorb vibrational energy without creating the rigid constraints that shrouds impose. This flexibility prevents the shroud-induced twist in vibration mode shapes that leads to aeroelastic flutter instability, while still providing effective damping.
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 the amplitude of oscillations in turbomachine rotor blades, minimizing weight and cost increases while maintaining aerodynamic efficiency and stability, and is specifically effective for aft-stage blades where shrouds are ineffective.
Implementation Method 1
A fluidic chamber is defined between the mass and the casing and filled with a fluid
Implementation Method 2
utilizing fluid dynamics to counteract vibrations
Data Source
AI summary
A vibrational dampening element is attached to a component and configured to adjust the amplitude of oscillations of the component. The vibrational dampening element includes a mass. The mass includes a main body and a member extending from the main body. A casing that encapsulates the mass. A fluidic chamber defined between the mass and the casing. A first fluidic portion is disposed between a first side of the mass and the casing. The first fluidic portion includes a first accumulator portion directly neighboring the member. A second fluidic portion is disposed between a second side of the mass and the casing. The second fluidic portion includes a second accumulator portion directly neighboring the member. The first accumulator portion is in fluid communication with the second accumulator portion. The vibrational dampening element further includes a primary passage that extends between the first fluidic portion and the second fluidic portion.