Blade Disk Arrangement for Gas Turbine Frequency Tuning
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Solution Overview
Problem
Gas turbine rotor assemblies face unwanted dynamic responses due to inadvertent excitation of resonant frequencies, necessitating the ability to tune or mistune the rotor to avoid specific frequencies or lessen their effect.
Innovation Solution
A method and arrangement for tuning a bladed rotor in a gas turbine engine by adding or removing mass from platform projections, which form a circumferentially interrupted rib on the hub, allowing for alteration of the natural frequency of the rotor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotor blades are tuned to have uniform natural frequencies, then the rotor operates efficiently at design speeds, but the rotor becomes susceptible to resonant vibrations when operating speeds coincide with these frequencies
Solution Approach 1:
The patent applies local quality by introducing platform projections at specific locations (every second blade) rather than uniformly across all blades. This creates localized mass variations that selectively affect the natural frequencies of specific blades, allowing the rotor to avoid resonant frequencies while maintaining operational stability. The localized modifications enable frequency mistuning without requiring changes to the entire rotor assembly.
Solution Approach 2:
The patent employs asymmetry by creating intentional frequency mismatches between adjacent blades through the platform projections. Instead of all blades having identical natural frequencies, the projections cause alternating blades to have different frequencies, breaking the symmetry that would otherwise make the entire rotor susceptible to resonant vibrations at specific speeds.
2Reliability
If mass is added to platform projections to alter natural frequency, then the frequency response is tuned to avoid resonances, but the manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating platform projections during the manufacturing process rather than adding them as post-processing modifications. The projections are formed as part of the blade platform structure, allowing mass adjustment through material removal or addition during manufacturing. This approach integrates the tuning function into the base manufacturing process, reducing overall complexity compared to separate tuning operations.
3Reliability
If platform projections are provided on every second blade, then a circumferentially interrupted rib is formed for effective frequency control, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the rotor blade array into groups with different frequency characteristics. Platform projections are provided on every second blade, creating distinct segments (alternating blades) with modified mass properties. This segmentation allows independent frequency control of different blade groups, achieving effective frequency tuning while maintaining a relatively simple overall structure compared to modifying all blades.
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 approach effectively modifies the frequency response of the bladed rotor, preventing unwanted vibrations by mismatching the natural frequencies of adjacent blades, thereby enhancing the engine's operational stability.
Implementation Method 1
tuning the bladed rotor by adding or removing mass from at least one platform projection to alter the natural frequency of the rotor
Data Source
AI summary
A gas turbine engine and a method of tuning a rotor in the gas turbine engine wherein the rotor includes an array of blades extending from a rotor hub each having an airfoil mounted to a blade platform. The method includes adding or removing material from bladed rotor projections to alter the mass of the rotor and change the frequency of the respective airfoil.