Acoustic Damper Recess Design for Grazing Flow Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing acoustic damping devices in gas turbines are ineffective due to the disturbance caused by grazing flow, which limits their ability to dampen combustion dynamics and noise at specific frequencies.
Innovation Solution
An acoustic damper design featuring a neck with a mouth that opens into a recess, reducing grazing flow effects, and optionally using shields to deflect grazing flow further, ensuring the mouth operates in a region with minimal or no grazing flow, thereby enhancing the damper's effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the mouth of the neck opens directly into the chamber, then the acoustic damper can be installed with simple structure, but the grazing flow disturbs the bias flow inside the neck and reduces damping effectiveness
Solution Approach 1:
The recess acts as an intermediary space between the chamber and the neck mouth. By introducing this intermediate region, the patent isolates the neck mouth from the direct impact of grazing flow while maintaining the acoustic connection to the chamber. This mediator structure allows the bias flow to remain undisturbed while still enabling acoustic pressure waves to reach the damping volume effectively.
2Reliability
If a recess is introduced to reduce grazing flow effects, then the damping effectiveness is improved, but the device complexity increases
Solution Approach 1:
The patent segments the flow path by introducing a recess that separates the high-velocity grazing flow region from the low-velocity bias flow region in the neck. This segmentation allows independent optimization of each region: the chamber can handle high-velocity flow while the neck maintains controlled, undisturbed flow conditions necessary for effective acoustic damping.
3Reliability
If shields are added to deflect grazing flow, then the protection of the neck mouth from grazing flow is enhanced, but the device complexity and flow resistance increase
Solution Approach 1:
The shields are strategically positioned to provide localized protection only where needed - at the mouth of the neck where grazing flow impact is most problematic. Rather than attempting to protect the entire chamber or use complex flow control systems, the shields apply protection locally at the critical interface between the chamber and neck, minimizing overall device complexity while achieving the desired effect.
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 proposed design significantly improves the acoustic damper's performance by minimizing the impact of grazing flow, leading to more effective noise reduction across various frequencies, as demonstrated by improved reflection coefficient measurements.
Implementation Method 1
These acoustic damping devices have one or more resonance frequencies. If under operation of the gas turbine the combustions dynamics stimulate the resonance frequencies of the acoustic damping devices, the combustion dynamics are reduced or damped.
Implementation Method 2
Grazing flow in the meaning of the claimed invention is the flow of gas inside the chamber that streams more or less parallel to an inner surface of the wall where the recess is located or perpendicular to the bias flow of gas through the neck of the damper.
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
An acoustic damper (11) comprising a neck (13) and a damping volume (15) is disclosed, wherein the neck (13) comprises a mouth (17) being in fluid connection with a chamber (5) and wherein the chamber (5) is limited by an inner surface (9) of at least one wall (7). The acoustic damper device is characterized in, that a recess (23) is located between the mouth (17) of the neck (13) and the inner surface (9) of the wall (7).