Gas Turbine Airfoil Frequency Design
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Solution Overview
Problem
Turbomachinery airfoils face durability issues due to vibrational stresses caused by resonant frequencies, which can lead to shortened lifespan if they operate at these frequencies during engine operation, and existing methods lack effective solutions for designing or repairing airfoils to avoid such stresses.
Innovation Solution
Designing and repairing turbomachine airfoils with specific frequency modes, such as 1EB and 1T modes, within precise frequency ranges (1049±10% Hz and 1271±10% Hz) using aluminum-based alloys, to manage vibrational responses and extend airfoil life, and incorporating these airfoils in various sections of gas turbine engines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If airfoils operate at resonant frequencies during engine operation, then power and performance are maintained, but the life of the airfoil is significantly shortened due to high vibrational stresses
Solution Approach 1:
The patent applies parameter changes by modifying the airfoil's physical dimensions (span, chord length, thickness) and material properties (aluminum-based alloy with specific density and modulus of elasticity) to alter its resonant frequencies. This ensures the airfoil's natural frequencies do not coincide with engine operating frequencies, thereby reducing vibrational stresses while maintaining power output and extending component life.
2Duration of action of stationary object
If airfoils are designed with specific frequency modes to avoid resonant stresses, then airfoil life is prolonged, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise parameter ranges for airfoil design (span: 2.13-2.43 inch, chord length: 3.56-3.86 inch, frequency tolerances: ±10%) to achieve desired vibrational characteristics. These controlled parameter variations allow manufacturers to produce airfoils with consistent frequency properties that avoid resonance while maintaining reasonable manufacturing tolerances.
Solution Approach 2:
The patent employs local quality by using aluminum-based alloys with specific localized properties (density of about 0.103 lb/in3, modulus of elasticity of about 10.4 Mpsi) in critical airfoil regions. This localized material optimization helps achieve the desired frequency characteristics without requiring excessive precision across the entire component.
3Reliability
If airfoils are repaired to restore specific mode frequencies, then reliability is improved by superseding unrestored frequencies, but repair complexity increases
Solution Approach 1:
The patent guides repair processes by specifying target frequency parameters (1049±10% Hz for 1EB mode, 1271±10% Hz for 1T mode) that repaired airfoils should achieve. This parameter-based approach simplifies repair complexity by providing clear frequency targets for restoration, allowing technicians to verify repair quality through frequency measurement rather than complex structural assessment.
Data Source
AI summary
A turbomachine airfoil element includes an airfoil that has pressure and suction sides spaced apart from one another in a thickness direction and joined to one another at leading and trailing edges. The airfoil extends in a radial direction a span that is in a range of 2.13-2.43 inch (54.2-61.8 mm). A chord length extends in a chordwise direction from the leading edge to the trailing edge at 50% span and is in a range of 3.56-3.86 inch (90.3-97.9 mm). The airfoil element includes at least one of a first mode with a frequency of 1049±10% Hz and a second mode with a frequency of 1271±10% Hz.