Gas Turbine Combustion Device Helmholtz Dampers
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Solution Overview
Problem
Lean premixed low emission combustion devices in gas turbines generate thermo acoustic pulsations, leading to mechanical vibrations and high NOx emissions due to inefficient damping systems that require large air mass flow diversion for cooling, reducing damping efficiency and increasing emissions.
Innovation Solution
A combustion device with a layered structure featuring inner and outer walls, intermediate layers, and strategically designed passages and chambers that minimize air diversion for cooling, incorporating Helmholtz dampers and diffusers to maintain damping efficiency while reducing NOx emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional acoustic screen with impingement plate is used for damping, then damping efficiency is reduced, but cooling of the acoustic screen requires large air mass flow diversion
Solution Approach 1:
The acoustic screen is divided into multiple segments or zones with different hole patterns and geometries, allowing different regions to perform different functions (damping vs. cooling) simultaneously. This segmentation enables the screen to maintain structural integrity while reducing the overall air mass flow requirement by optimizing the distribution of cooling passages.
Solution Approach 2:
The acoustic screen is designed to perform multiple functions simultaneously: acoustic damping, structural support, and thermal management. By integrating cooling channels directly into the screen structure and using the screen itself as a heat dissipation component, the design eliminates the need for separate cooling systems that would require additional air mass flow diversion.
2Temperature
If large air mass flow is diverted for cooling the acoustic screen, then the acoustic screen is cooled effectively, but NOx emissions increase due to higher flame temperature
Solution Approach 1:
Cooling is applied locally only where thermally critical, rather than uniformly across the entire acoustic screen. The cooling channels are strategically positioned in high-heat-flux regions, allowing effective thermal management with minimal air mass flow diversion, thereby preserving combustion efficiency and reducing NOx emissions.
Solution Approach 2:
The patent replaces conventional mechanical cooling systems (which require large air mass flow) with a thermally integrated design where the acoustic screen's own structure facilitates heat dissipation. This substitution reduces the mechanical intervention in the airflow system, maintaining better combustion conditions and lower NOx emissions.
3Temperature
If large air mass flow is diverted from the plenum for cooling, then cooling is improved, but damping efficiency is reduced
Solution Approach 1:
The damping function and cooling function are merged into a single integrated acoustic screen structure. The same components that provide acoustic damping (holes, passages, resonant chambers) also serve as cooling channels, eliminating the need for separate cooling systems that would divert additional air mass flow and compromise damping efficiency.
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 solution effectively suppresses thermo acoustic pulsations with high damping efficiency and reduced NOx emissions by optimizing air flow and cooling, preventing air recirculation and maintaining damping performance.
Implementation Method 1
In order to suppress oscillations, combustion devices are usually provided with damping devices; typically damping devices consist of quarter wave tubes, Helmholtz dampers or acoustic screens.
Implementation Method 2
second passages (12) having inlets (13) connected to the outer (14) of the combustion device (1) and passing through the outer wall (8) for cooling the inner wall (7)
Implementation Method 3
Between the inner and outer wall (7, 8) an intermediate layer (17) is provided defining a plurality of chambers (18)
Data Source
Figure 1
Figure 2~3
Figure 4~8
AI summary
The combustion device (1) for a gas turbine comprises a portion (6) provided with an inner and an outer wall (7, 8). The inner wall (7) comprises first passages (9) connecting the zone between the inner and outer wall (7, 8) to the inner (10) of the combustion device (1). The outer wall (8) comprises second passages (12) for cooling the inner wall (7). Between the inner and outer wall (7, 8) an intermediate layer (17) is provided defining a plurality of chambers (18), each connected to at least one first passage (9) and a plurality of second passages (12) and defining Helmholtz dampers. These second passages (12) open in third passages (22) connected to the chambers (18) and have facing outlets (23).