Turbine Combustor Fuel Injector Asymmetry for Thermoacoustic Stability
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Solution Overview
Problem
Turbine engine combustors face instability issues due to thermoacoustic instabilities caused by the coupling of acoustic modes with unsteady heat release, leading to large pressure oscillations and potential structural damage, particularly in annular combustors with equi-spaced fuel injectors.
Innovation Solution
The combustor design incorporates a fluctuating pattern for downstream fuel injectors with varying fuel injection rates and inter-injector spacings, creating different flame zones with distinct thermoacoustic properties to dissipate instability, and arranges upstream and downstream fuel injectors in distinct patterns to mitigate these instabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If equi-spaced fuel injectors are used in annular combustors, then uniform fuel distribution is achieved, but thermoacoustic instabilities occur leading to large pressure oscillations
Solution Approach 1:
The patent applies asymmetry by arranging fuel injectors in a non-uniform pattern around the combustor circumference. Specifically, the injectors are positioned at different angular intervals rather than equidistantly, creating an asymmetric fuel injection distribution that disrupts the coupling between acoustic modes and heat release, thereby mitigating thermoacoustic instabilities while maintaining acceptable fuel distribution uniformity.
Solution Approach 2:
The patent implements local quality by varying the spatial distribution of fuel injection rates at different locations around the combustor. Each injector or group of injectors operates with locally optimized injection characteristics, creating zones of different fuel concentration and combustion intensity. This local variation in combustion quality disrupts the global acoustic resonance patterns that cause thermoacoustic instabilities.
2Device complexity
If uniform fuel injection pattern is used, then simple injector configuration is maintained, but thermoacoustic instabilities cause structural damage risk
Solution Approach 1:
The patent introduces asymmetry in the injector configuration by positioning fuel injectors at non-uniform angular intervals around the combustor. This asymmetric arrangement breaks the symmetry that allows thermoacoustic instabilities to develop, reducing pressure oscillations and structural damage risk while adding minimal complexity to the overall system design.
3Reliability
If fluctuating fuel injection pattern is implemented, then thermoacoustic instabilities are reduced, but injector arrangement complexity increases
Solution Approach 1:
The patent resolves this contradiction by implementing a fixed asymmetric injector pattern rather than a dynamically fluctuating one. The non-uniform angular positioning of injectors provides the stability benefit of reduced thermoacoustic instabilities while avoiding the complexity of active control systems required for dynamic pattern adjustment.
Solution Approach 2:
The patent uses local quality by creating specific zones with different fuel injection characteristics at predetermined locations around the combustor. This static zonation approach achieves combustion stability benefits without requiring complex real-time control mechanisms, as each zone maintains its optimized characteristics throughout operation.
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 design effectively reduces or eliminates thermoacoustic instabilities by creating uneven fuel injection patterns, resulting in stable combustor operation and reduced risk of structural damage.
Implementation Method 1
Each of these fuel injectors injects fuel into the combustion chamber for mixing with core air and combustion
Implementation Method 2
The combustor design incorporates a fluctuating pattern for downstream fuel injectors with varying fuel injection rates and inter-injector spacings, creating different flame zones with distinct thermoacoustic properties to dissipate instability
Implementation Method 3
fuel injects fuel into the combustion chamber for mixing with core air and combustion
Data Source
AI summary
A combustor assembly includes a first wall, a second wall, a bulkhead and a plurality of fuel injectors. The bulkhead forms a combustion chamber with the first and the second walls. The fuel injectors are configured with the first wall in a unique and/or a fluctuating pattern.