Adjustable Acoustic Damper for Combustor Liners
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Solution Overview
Problem
Gas turbine engine combustors using lean premixed combustion systems face combustion instability leading to high dynamic pressure oscillations, which cause mechanical and thermal fatigue, and existing damping solutions are either ineffective or create structural vulnerabilities.
Innovation Solution
An acoustic damping device comprising a resonating tube with a predetermined characteristic length and a vented ferrule aligned with perforations in the combustor liner to form fluidic communication, attenuating specific frequency ranges of acoustic energy through dissipative losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If passive pressure dampers are used to reduce dynamic pressure oscillations, then pressure pulse amplitude is reduced, but the dampers are effective only at specific fixed amplitudes and frequencies, rendering them of limited use due to varying operating conditions
Solution Approach 1:
The patent applies dynamics by making the resonating tube length adjustable rather than fixed. The tube can be extended or retracted to different lengths depending on the operating conditions, allowing the damper to adapt to varying amplitudes and frequencies of pressure pulses. This dynamic adjustment capability enables the same device to remain effective across multiple operating regimes, resolving the contradiction between reducing pressure oscillations and maintaining adaptability.
Solution Approach 2:
The patent changes the physical parameter of the resonating tube length to adapt to different operating conditions. By adjusting the tube length parameter, the resonant frequency of the damper can be tuned to match the frequency of pressure oscillations under different operating conditions. This parameter change approach allows the damper to maintain effectiveness across varying amplitudes and frequencies, resolving the adaptability issue.
2Object-affected harmful factors
If existing passive pressure damper designs project through openings formed through the liner of the combustor, then damping function is achieved, but structurally vulnerable regions of high thermal stress are created
Solution Approach 1:
The patent applies the nesting principle by placing the resonating tube inside a case that is mounted to the outer surface of the liner, rather than having the tube project through openings in the liner. The case contains the resonating tube and provides a sealed mounting structure. This nested arrangement eliminates the need for openings through the liner, preserving the liner's structural integrity while still achieving the pressure damping function through the sealed connection between the case and liner outer surface.
Solution Approach 2:
The patent introduces a case as an intermediary structure between the resonating tube and the liner. The case serves as a mediator that connects the damping mechanism to the liner without requiring openings through the liner itself. The case is mounted to the outer surface and provides a sealed interface, allowing the resonating tube to function while protecting the liner from structural vulnerability. This intermediary approach resolves the contradiction between achieving damping and maintaining structural integrity.
3Object-generated harmful factors
If lean premixed combustion systems are used to reduce NOx emissions, then NOx emissions are reduced, but combustion instability increases leading to high dynamic pressure oscillations
Solution Approach 1:
The patent applies the 'blessing in disguise' principle by converting the harmful dynamic pressure oscillations generated by lean premixed combustion into a controllable parameter. The acoustic damper uses the oscillating pressure itself as the driving force for the resonating tube, transforming the harmful instability into a useful mechanism for damping. The resonating tube responds to the pressure oscillations and generates counter-phase vibrations that cancel the harmful effects, thus converting the harm into a beneficial self-regulating damping action.
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
Effectively reduces combustion dynamics by absorbing and dissipating acoustic energy across a range of frequencies, minimizing structural stress and enhancing operational stability of the combustor.
Implementation Method 1
a resonating tube with a predetermined characteristic length and a vented ferrule aligned with perforations in the combustor liner to form fluidic communication, attenuating specific frequency ranges of acoustic energy through dissipative losses
Implementation Method 2
attenuating specific frequency ranges of acoustic energy through dissipative losses
Implementation Method 3
attenuating specific frequency ranges of acoustic energy through dissipative losses
Data Source
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AI summary
An acoustic damping device is provided that includes a resonating tube defining a resonating cavity with a predetermined characteristic length and a tube end defining a cavity opening, as well as a case configured to reversibly secure the tube end in fluidic communication with a fluid volume enclosed by a liner. The cavity opening is connected with the resonating cavity. The case includes a vented ferrule adpressed over a perforated region of the liner. The vented ferrule defines a ferrule opening that is aligned with the perforated region of the liner and the cavity opening to form the fluidic communication between the fluid volume and the resonating cavity.