Nested Lattice Damping for Turbine Blade Vibration Control
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Solution Overview
Problem
Conventional vibration damping methods for industrial gas turbine blades, such as shrouds, are ineffective for aft-stage blades, leading to high cycle fatigue and premature failure, and increase rotor weight and cost, while also causing aerodynamic inefficiencies and aeroelastic flutter instability.
Innovation Solution
A lattice structure with nested lattice structures is used internally within the turbine blade to provide distributed vibration damping, eliminating the need for shrouds and enhancing power output by absorbing and dissipating vibrations through friction and viscous damping mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shrouds are used for vibration damping in aft-stage blades, then vibration damping is provided, but blade weight increases and aerodynamic efficiency decreases
Solution Approach 1:
The shroud structure is segmented into multiple lattice elements arranged in a three-dimensional configuration. This segmentation allows the damping function to be distributed throughout the shroud volume, providing effective vibration damping while using less material than a solid shroud, thereby reducing blade weight.
Solution Approach 2:
The shroud is designed as a lattice structure with inherent porosity, creating a three-dimensional framework of interconnected struts and nodes. This porous configuration provides vibration damping through friction and material hysteresis while significantly reducing the mass compared to a solid shroud construction.
2Reliability
If shrouds are used for vibration damping, then damping is achieved, but aerodynamic performance deteriorates due to tip losses and flow blockage
Solution Approach 1:
The porous lattice structure of the shroud allows aerodynamic flow to pass through the structure rather than being completely blocked. This reduces flow separation and tip losses while maintaining the vibration damping function, thereby preserving aerodynamic efficiency.
Solution Approach 2:
The shroud combines structural support and damping functions in a single lattice construction that integrates mechanical strength with aerodynamic flow permeability, creating a composite structure that simultaneously addresses vibration control and aerodynamic performance.
3Reliability
If tip shrouds are used, then damping is provided, but significant twist is induced in vibration mode shapes causing aeroelastic flutter instability
Solution Approach 1:
The lattice shroud structure provides locally distributed damping throughout the shroud volume rather than concentrating damping forces at the tip. This distributed approach reduces the induced twist in vibration mode shapes and minimizes aeroelastic flutter instability while maintaining effective vibration damping.
4Reliability
If platform dampers are used, then vibration damping is effective for medium and long shank blades, but they are ineffective for aft-stage blades with short shanks
Solution Approach 1:
The lattice shroud structure serves multiple functions simultaneously: it provides vibration damping, maintains aerodynamic efficiency, reduces blade weight, and can be applied to various blade configurations including aft-stage blades with short shanks. This multi-functionality makes the solution universally applicable across different turbine blade types.
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 nested lattice structure effectively dampens vibrations, reducing the need for shrouds, increasing the flow path annulus area, and enhancing power output by absorbing and dissipating vibrations, thereby reducing the risk of fatigue and aerodynamic inefficiencies.
Implementation Method 1
absorbing and dissipating vibrations through friction and viscous damping mechanisms
Implementation Method 2
absorbing and dissipating vibrations through friction and viscous damping mechanisms
Data Source
Figure 1~3
Figure 4~6
AI summary
A nested lattice structure 29 for use in a damping system includes a first lattice structure 26 including: a first outer passage 30 including a hollow interior 45; a second outer passage 32 including a hollow interior; and an outer node 42 including a hollow interior and forming an intersection of the first outer passage 30 and the second outer passage 32. The nested lattice structure 29 includes a second lattice structure 28 nested within the hollow interior of the first lattice structure 26 including: a first inner passage 44; a second inner passage 46; and an inner node 50 forming an intersection of the first inner passage 44 and the second inner passage 46. Each of the first inner passage 44, the second inner passage 46 and the inner node 50 are nested within the respective first outer passage 30, the second outer passage 32 and the outer node 42.