Gas Turbine Combustor Asymmetry Reduces Thermoacoustic Pulsations
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Solution Overview
Problem
Gas turbine assemblies with sequential combustors experience self-excited thermoacoustic pulsations due to reheat burner flames, which can exceed acceptable limits and restrict operational range, and existing damping devices are not always effective or space-efficient.
Innovation Solution
The combustor unit employs a non-uniform distribution pattern for fuel and air injection units, varying their geometry, fuel-to-air ratios, and mixing characteristics to control flame behavior and reduce thermoacoustic pulsations by introducing uneven flame distributions and disruptive interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a plurality of identical injection units are circumferentially arranged to uniformly inject fuel, then uniform fuel distribution is achieved, but self-excited thermoacoustic pulsations occur that exceed acceptable limits
Solution Approach 1:
The patent applies asymmetry by deliberately designing injection units with different geometries, positions, or injection characteristics around the combustion chamber. This asymmetric arrangement creates non-uniform fuel distribution that disrupts the coherent flame structures responsible for thermoacoustic pulsations, while still maintaining adequate mixing and combustion efficiency.
Solution Approach 2:
The patent implements local quality by varying the injection characteristics (such as injection angle, flow rate, or geometry) of individual injection units based on their specific location around the combustion chamber. This localized customization allows each injection unit to contribute differently to the overall combustion process, preventing synchronized flame oscillations while maintaining local combustion quality.
2Object-generated harmful factors
If damping devices are added to reduce pressure oscillations, then thermoacoustic pulsations are damped, but device complexity increases and space requirements are not always met
Solution Approach 1:
The patent applies self-service by designing the injection units to inherently suppress thermoacoustic pulsations through their geometric and operational characteristics. The combustion system itself becomes the damping mechanism, eliminating the need for separate damping devices. The injection units' asymmetric configuration creates disruptive interference that naturally dampens pressure oscillations without additional components.
3Device complexity
If identical injection units are used for simplicity, then device complexity is reduced, but flame pulsations cannot be controlled
Solution Approach 1:
The patent deliberately introduces asymmetry in the injection unit configuration, using units with different geometries, orientations, or injection rates. This asymmetric design increases device complexity slightly but effectively controls flame pulsations by preventing synchronized combustion across all injection points, thereby disrupting the feedback loop that sustains thermoacoustic oscillations.
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 reduces flame pulsations without increasing NOx emissions, enhancing operational flexibility and efficiency while eliminating the need for costly damping devices.
Implementation Method 1
the compressed air is mixed with at least one fuel and combusted
Implementation Method 2
The reheat burner flames, in certain operating conditions, generate self-excited thermoacoustic pulsations
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3c
AI summary
A combustor unit (10) for a gas turbine assembly (1) comprises a premix combustor (15) and a reheat combustor (16), which are arranged in series along the gas flow direction (M); the reheat combustor (16) comprises: a housing (20) extending substantially along a longitudinal axis (B) and defining a reheat combustion chamber (23), a plurality of injection units (27) distributed around the reheat combustion chamber (23) and fed with air and fuel; at least one first injection unit (27a) of the plurality of injection units (27) being configured to inject fuel and air differently with respect to the others injection units (27b, 27c, 27d, 27e).