Turbine Blade Shroud Spring Strip Vibration Damping
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Solution Overview
Problem
Gas turbine blades experience out-of-plane vibration leading to relative anti-phase motion between shrouds, causing fretting, deterioration, and reduced natural frequency, with existing solutions either increasing manufacturing complexity or not addressing inter-blade vibration effectively.
Innovation Solution
A spring strip with a flat portion, curved portion, and tab is used to couple adjacent turbine blade shrouds, providing preload damping by inserting the spring strip through a slot in the labyrinth seal segment, allowing it to bend and form contact interfaces that reduce vibration amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hollow airfoil filled with a preloaded spring is used to dampen vibratory response, then vibration damping is improved, but manufacturing complexity and cost increase due to requiring a pocket to receive the filler
Solution Approach 1:
The invention extracts the damping function from a complex hollow airfoil structure with internal pockets and fillers, and implements it through a simple external spring strip attached to the shroud surface. This separates the damping functionality from the airfoil structure, eliminating the need for manufacturing pockets and complex internal configurations.
Solution Approach 2:
The spring strip functions as a flexible element that provides vibration damping through its elastic deformation. This thin, flexible component achieves the same damping effect as complex internal structures but with much simpler manufacturing and installation.
2Reliability
If existing damping solutions are applied, then vibration damping is improved, but they do not specifically address vibration from inter-blade interaction (nodal-diameter-type vibration)
Solution Approach 1:
The spring strip is specifically positioned at the shroud tip region where inter-blade vibration occurs during nodal-diameter-type vibration. This localized placement ensures the damping force is applied precisely where needed to counteract the relative anti-phase motion between adjacent blade shrouds, making the solution specifically effective for inter-blade interaction vibrations.
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 spring strip effectively dampens vibrations, reducing amplitude by more than ten-fold and preventing natural frequency drift, thereby enhancing the durability and performance of turbine blades.
Implementation Method 1
a curved portion (720) and a tab (730), the curved portion having a first end connected to the flat portion (710) and a second end opposite the flat portion (710); and wherein the second end of the curved portion (720) is malleable to bend into the tab (730)
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
During operation, a bladed rotor disk typically experiences out-of-plane vibration which can result in deterioration and/or cracking at the interface between adjacent shrouds of the turbine blades. In an embodiment, slots are formed at the end of a labyrinth seal segment of each shroud. Preloaded spring strips are inserted through the slots to couple adjacent shrouds while preventing the natural frequency of the turbine blades from drifting to the operating speed range and/or providing vibration damping to the untuned blade mode.