Turbine Blade Tip Pockets for Vibration Control
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Solution Overview
Problem
Longer turbine rotor blades in gas turbine engines face increased mechanical loads and vibratory responses, leading to reduced efficiency and shorter component life due to increased stress and vibratory loads, which existing damping methods like tip shrouds struggle to effectively manage while also adding weight and complexity.
Innovation Solution
The implementation of mid-span shrouds and hollow outboard regions with cavities in turbine blades, which reduce the overall weight and alter the frequency and mode shape of the blade, thereby reducing vibrational loads and enhancing efficiency by distributing stress more evenly and providing structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If longer turbine rotor blades are used to increase engine power and efficiency, then the engine efficiency and power output are improved, but the mechanical loads and vibratory responses increase leading to reduced component life
Solution Approach 1:
The blade is divided into distinct regions with different structural characteristics: an inboard region with higher material density and an outboard region with lower material density (including hollow sections and cavities). This segmentation allows each region to be optimized independently - the inboard region provides structural strength near the root while the outboard region reduces weight and vibratory loads at the tip, resolving the contradiction between achieving long blade length for efficiency while maintaining component life through reduced mechanical loads.
Solution Approach 2:
Different portions of the blade are given different material properties and structural characteristics. The inboard region maintains higher density and solid construction for strength, while the outboard region incorporates hollow sections, cavities, and reduced density materials. This local differentiation allows the blade to simultaneously achieve the strength needed for reliability at the root and the weight reduction needed to降低 vibratory loads at the tip, enabling longer blades without proportionally increasing mechanical loads throughout.
2Object-affected harmful factors
If traditional tip shrouds are added to reduce vibratory loads, then the vibrational forces are reduced, but the blade weight and structural complexity increase
Solution Approach 1:
Instead of adding external tip shrouds to the blade, the invention extracts material from the outboard region to create hollow sections and cavities directly within the blade structure. This removes the need for separate external damping components while still achieving vibratory load reduction. The hollow outboard regions and cavities serve as built-in mass reduction features that lower natural frequencies and vibratory responses without requiring additional attached components, thus reducing structural complexity compared to traditional tip shroud solutions.
Solution Approach 2:
The vibratory load reduction function is merged into the primary blade structure itself rather than being a separate component. The hollow sections and cavities are integrated directly into the blade airfoil and internal structure, combining the structural function with the vibrational damping function. This integration eliminates the need for separate tip shrouds and their associated mounting hardware, reducing overall structural complexity while achieving the same harmful factor mitigation.
3Object-affected harmful factors
If hollow outboard regions with cavities are implemented to reduce weight and vibrational loads, then the vibrational forces and mechanical loads are reduced, but the manufacturing complexity increases
Solution Approach 1:
The hollow outboard regions and cavities are designed to be formed during the primary blade manufacturing process itself, rather than requiring post-manufacturing assembly. The manufacturing method creates these hollow sections and cavities as integral features of the blade structure from the outset, using techniques such as selective material removal, additive manufacturing with internal cavities, or forming hollow sections during casting or forging. This preliminary creation of complex geometries during manufacturing avoids the need for complex post-assembly operations, thereby reducing the overall manufacturing complexity despite the sophisticated internal structures.
Data Source
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AI summary
A rotor blade (16) for use in a turbine of a combustion turbine engine (10) comprises an airfoil (25). The airfoil (25) including a concave pressure sidewall (26) and a convex suction sidewall (27) extending axially between corresponding leading and trailing edges (20, 21) and radially between the base (121) and an outboard tip end (41). The rotor blade (16) further including at least one mid-span shroud (51) configured to engage a corresponding mid-span shroud (51) on at least one neighboring rotor blade (16) during operation. The airfoil (25) further includes an inboard region (58) between the at least one mid-span shroud (51) and the base (121) of the blade (216) with an inboard direction of the airfoil (25) toward the base (121); and an outboard region (59) between the at least one mid-span shroud (51) and the outward tip end (41) of the blade (121) with an outboard direction of the airfoil (25) toward the outward tip end (41). The outboard region (59) includes at least two cavities (61, 66) extending from the outboard tip end (41) inboard of the airfoil (25) toward the at least one mid-span shroud (51); and inboard of the at least one mid-span shroud (51), the inboard region (58) is substantially solid.