Gas Turbine Fuel Nozzle Frequency Tuning via Alloy Selection
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Solution Overview
Problem
Gas turbine engine fuel nozzle assemblies experience low cycle and high cycle fatigue, stress concentrations, and premature failure due to natural frequency matching operating rotor frequencies, combustion tones, and thermal expansion differences in materials used for various components.
Innovation Solution
Fabricating the flange and premix tube from different alloys to exhibit frequencies distinct from the natural operating frequency of the gas turbine engine, coupled using an electron beam weld to enhance structural strength and resilience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the fuel nozzle assembly components (flange, premix tube, swirler) are manufactured from different materials and coupled with welded and brazed joints, then the assembly can be constructed with appropriate material properties for each component, but the different material properties cause different thermal growth rates and magnitudes of thermal expansion and contraction, leading to stress concentrations and joint fatigue
Solution Approach 1:
The patent applies parameter changes by carefully selecting and controlling the material properties (thermal expansion coefficients, strength characteristics) of each component to ensure that despite using different materials for the flange, premix tube, and swirler, their thermal growth rates are substantially matched. This parameter optimization prevents differential thermal expansion from causing stress concentrations or joint failures during engine operation.
2Device complexity
If the natural frequency of the fuel nozzle assembly is similar to or substantially the same as the operating rotor frequency, combustion tones, and siren tones of the gas turbine engine, then the design may be simpler, but stress concentrations around the fuel nozzle assembly and structural break-out into the fuel holes develop due to resonance
Solution Approach 1:
The patent applies mechanical vibration principles by calculating and adjusting the natural frequency of the fuel nozzle assembly to ensure it does not coincide with the operating rotor frequency, combustion tones, or siren tones of the gas turbine engine. This frequency tuning prevents resonant vibrations that would cause stress concentrations and structural break-out, thereby eliminating the need for overly conservative design margins.
3Ease of manufacture
If the fuel nozzle assembly operates at frequencies matching the operating frequencies of the gas turbine engine, then the components can be designed with standard dimensions, but low cycle and high cycle fatigue develop in fuel nozzle components and joints over time
Solution Approach 1:
The patent applies parameter changes by optimizing the natural frequency parameter of the fuel nozzle assembly to avoid resonance with engine operating frequencies. This frequency parameter adjustment prevents both low cycle and high cycle fatigue in the components and joints, thereby extending the service life of the fuel nozzle assembly without requiring non-standard component dimensions.
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 solution reduces stress concentrations, minimizes break-out into fuel holes, and extends the life of fuel nozzle components by tuning natural frequencies, improving durability and reducing production costs through optimized frequency margin and material selection.
Implementation Method 1
coupled using an electron beam weld to enhance structural strength and resilience
Data Source
AI summary
A method of assembling a fuel nozzle assembly for a gas turbine engine having a natural operating frequency includes providing a flange and providing a premix tube. The flange is fabricated from a first alloy such that the flange is configured to exhibit a first frequency that is different than the natural operating frequency of the gas turbine engine. The premix tube is fabricated from a second alloy such that the premix tube is configured to exhibit a second frequency that is different from the natural operating frequency of the gas turbine engine. The premix tube is coupled to the flange.