Axially Staggered Premixer Vanes for Combustion Dynamics Reduction
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Solution Overview
Problem
Gas turbine engines using lean premixed combustion suffer from combustion dynamics issues due to pressure fluctuations and oscillations, leading to reduced performance and increased NOx emissions, which are exacerbated by the sensitivity to fuel composition.
Innovation Solution
The implementation of a dual premixer system with axially staggered vane packs and diffusion tips to create a phase difference between heat release and pressure oscillations, thereby dampening combustion dynamics through destructive interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If lean premixed combustion is used to reduce NOx emissions, then emission performance is improved, but combustion stability deteriorates due to combustion dynamics and pressure oscillations
Solution Approach 1:
The combustion system is divided into multiple independent premixers (first premixer and second premixer) with axially staggered vane packs. Each premixer operates semi-independently, and the staggered arrangement creates phase differences in the fuel-air mixing processes, which disrupts the coherent pressure oscillations that drive combustion dynamics while maintaining lean premixed combustion for low NOx emissions
Solution Approach 2:
The axially staggered vane packs create periodic variations in the fuel-air mixing process with different phase angles. This periodic action introduces a phase shift between the heat release oscillations from different premixers, causing destructive interference of the pressure waves that would otherwise reinforce each other and amplify combustion dynamics
2Object-generated harmful factors
If lean premixed combustion is used to reduce NOx emissions, then emission performance is improved, but combustion dynamics cause performance degradation through large amplitude pressure oscillations
Solution Approach 1:
By segmenting the combustion system into multiple staggered premixers, the patent prevents the synchronized pressure oscillations that degrade performance. The segmented arrangement ensures that pressure oscillations from one premixer do not directly reinforce oscillations from others, maintaining stable combustion and consistent system performance while preserving the emission benefits of lean premixed combustion
Solution Approach 2:
The patent converts the potentially harmful pressure oscillations into a beneficial phase-distributed mixing pattern. The axially staggered vane packs transform what would be coherent, amplitude-amplifying pressure waves into incoherent, phase-distributed fluctuations that cancel each other out, turning a source of performance degradation into a mechanism for stabilizing combustion
3Stability of the object's composition
If traditional diffusion flame combustion is used, then combustion stability is maintained, but NOx emissions become unacceptably high
Solution Approach 1:
The patent changes the combustion parameters by implementing lean premixed combustion with multiple axially staggered vane packs. This parameter change allows the system to operate at lower equivalence ratios (leaner mixtures) while maintaining stability through the staggered configuration, thereby reducing flame temperatures and suppressing thermal NOx formation mechanisms without sacrificing combustion stability
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 combustion dynamics, enhances fuel flexibility, and improves emission performance by stabilizing the combustion process and reducing NOx emissions.
Implementation Method 1
The implementation of a dual premixer system with axially staggered vane packs and diffusion tips to create a phase difference between heat release and pressure oscillations, thereby dampening combustion dynamics through destructive interference
Implementation Method 2
The thermal mass of the excess air present in the combustion chamber absorbs the heat generated during combustion, thus limiting the temperature rise to a level where thermal NOX is not formed
Data Source
AI summary
Methods and systems for combustion dynamics reduction are provided. A combustion chamber may include a first premixer and a second premixer. Each premixer may include at least one fuel injector, at least one air inlet duct, and at least one vane pack for at least partially mixing the air from the air inlet duct or ducts and fuel from the fuel injector or injectors. Each vane pack may include a plurality of fuel orifices through which at least a portion of the fuel and at least a portion of the air may pass. The vane pack or packs of the first premixer may be positioned at a first axial position and the vane pack or packs of the second premixer may be positioned at a second axial position axially staggered with respect to the first axial position.