Adjustable Damper Assembly for Combustion Chamber Acoustic Oscillations
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Solution Overview
Problem
Conventional gas turbine combustion chambers experience severe mechanical stress due to acoustic oscillations, which are difficult to manage with fixed-frequency Helmholtz dampers that require shutdown and disassembly for adjustments, leading to inefficient testing and potential engine outages.
Innovation Solution
A damper assembly with a movable element and compressed air feeding system allows for adjustable damping frequencies and deactivation, enabling online frequency adjustments and optimized damper usage by varying the volume of the damper cavity through a plug and sealing mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed geometry Helmholtz dampers are used, then the damper provides specific damping characteristics for certain frequencies, but the geometry cannot be changed during operation and requires shutdown and disassembly for adjustments
Solution Approach 1:
The patent applies the dynamics principle by introducing a movable element (piston) that can shift position within the damper cavity, allowing the effective volume of the damper to change dynamically during operation. This enables continuous adjustment of the resonance frequency without requiring shutdown or disassembly, resolving the contradiction between maintaining reliable damping characteristics and enabling operational adjustability.
Solution Approach 2:
The patent implements parameter changes by varying the volume of the damper cavity through piston displacement, which directly changes the resonance frequency of the Helmholtz damper. This allows the damping characteristics to be adapted to different operating conditions while maintaining system reliability, eliminating the need for physical reconfiguration.
2Adaptability or versatility
If multiple damper assemblies are connected to the combustion chamber to achieve different damping frequencies, then various frequencies can be tested, but the number of dampers increases and all dampers remain active whether needed or not
Solution Approach 1:
The patent applies universality by designing a single damper assembly that can perform multiple functions: it can operate at different resonance frequencies through piston adjustment and can be completely deactivated when not needed. This multi-functional capability replaces the need for multiple specialized dampers, reducing system complexity while maintaining adaptability across different operating regimes.
Solution Approach 2:
The movable piston element enables dynamic reconfiguration of the damper's characteristics during operation, allowing one damper to replace multiple fixed-frequency dampers. The system can adapt its damping frequency or deactivate entirely based on operational requirements, eliminating the need for multiple static damper assemblies.
3Reliability
If several damper assemblies are used to cover different operation regimes, then damping coverage is improved, but purge air still cools down the combustor chamber and increases NOx when dampers are not needed
Solution Approach 1:
The patent enables dynamic deactivation of the damper by positioning the movable piston to block the neck completely, stopping the purge air flow. This eliminates the harmful side effect of unnecessary cooling and NOx generation while maintaining damping coverage when needed, resolving the contradiction between reliable damping coverage and reduction of harmful emissions.
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
Enables efficient adjustment and deactivation of damping frequencies during engine operation, reducing testing time and minimizing unnecessary damper assemblies, thereby enhancing combustion chamber stability and reducing NOx emissions.
Implementation Method 1
the compressed air feeding system (15) is arranged such to feed compressed air in a pressurised volume delimited by a wall of the movable element and an internal wall of the hollow body
Implementation Method 2
acoustic oscillation usually occurs in the combustion chambers... To reduce the acoustic oscillations noise it is well known in the art to install acoustic damping devices like Helmholtz resonators
Data Source
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AI summary
The present invention generally relates to gas turbines and more in particular it relates to a damper assembly for a combustion chamber of a gas turbine. Advantageously, the damper assembly according to the present invention may be adjusted to different frequencies during operation and/or deactivated for different operation regimes.