Arrayed Mixing Vanes for Gas Turbine Combustor Premixer
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Solution Overview
Problem
Existing gas turbine combustors with lean premixing of fuel and air face issues such as flashback, auto-ignition, non-uniform fuel-air mixing, and high combustion-driven dynamic pressure, leading to emission performance degradation, hardware damage, and reduced stability compared to conventional diffusion flame combustors.
Innovation Solution
A fuel-air premixer design featuring an air inlet, fuel inlet, shroud, central body, and cascade of vanes with internal fuel flow passages and fuel injection holes, creating small mixing eddies that break up the flow field into uniform regions, absorbing turbulence and preventing flashback and auto-ignition, while ensuring uniform fuel-air distribution and reduced dynamic pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If lean premixing of fuel and air is used to reduce NOx emissions, then emission performance is improved, but flashback and auto-ignition occur in the premixing section
Solution Approach 1:
The premixing section is segmented into multiple zones with different fuel-air mixing ratios. A first fuel-air mixture with a first mixing ratio is premixed in a first region, and a second fuel-air mixture with a second mixing ratio is premixed in a second region. This segmentation allows the system to maintain lean premixing for NOx reduction while avoiding flashback and auto-ignition by creating regions with different combustion characteristics.
Solution Approach 2:
Different regions of the premixing section are assigned different local qualities in terms of fuel-air mixing ratios. The first region has a specific mixing ratio optimized for stable combustion, while the second region has a different mixing ratio optimized for NOx reduction. This local differentiation allows each region to perform its specific function without causing flashback or auto-ignition.
2Manufacturing precision
If fuel and air are uniformly mixed to achieve desired emission performance, then mixing uniformity is improved, but flashback and auto-ignition risk increases
Solution Approach 1:
The mixing process is segmented into distinct regions with different mixing ratios rather than creating a completely uniform mixture. This segmentation maintains sufficient uniformity for emission performance while avoiding the conditions that lead to flashback and auto-ignition that would occur with complete uniformity.
Solution Approach 2:
The fuel-air mixing ratio parameter is varied across different regions of the premixing section. By changing this parameter spatially, the system achieves the desired emission performance through adequate mixing uniformity while preventing flashback and auto-ignition by avoiding overly uniform lean mixing throughout the entire section.
3Object-generated harmful factors
If fuel concentration is reduced to meet emission requirements, then NOx emissions are reduced, but flame propagation speed decreases and combustion stability deteriorates
Solution Approach 1:
The combustor is divided into regions with different fuel concentrations. A first fuel-air mixture with higher fuel concentration provides stable combustion and adequate flame propagation speed, while a second fuel-air mixture with lower fuel concentration reduces NOx emissions. This segmentation allows the system to achieve both emission requirements and combustion stability simultaneously.
Solution Approach 2:
Different local regions are assigned different fuel concentrations appropriate to their function. Regions requiring stable combustion receive higher fuel concentration, while regions focused on emission control receive lower fuel concentration. This local quality differentiation resolves the contradiction between emission reduction and 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
The premixer achieves uniform fuel-air mixing, eliminates flashback and auto-ignition, and reduces combustion-driven dynamic pressure, enhancing emission performance and hardware durability by stabilizing the flame and improving mixing efficiency.
Implementation Method 1
The flow field inside the premixer is broken up by the arrayed vanes into a series of small regions each contains a small size mixing eddy
Implementation Method 2
the large scale turbulent of the air flow is absorbed
Data Source
AI summary
A fuel-air premixer for use in a combustor of a gas turbine includes an air inlet, a fuel inlet, a shroud, a central body and a cascade of vanes. The premixer mixes fuel and air in the annular mixing passage into a uniform mixture for injecting into a combustor reaction zone. The air from a compressor is injected into the mixer through an air inlet. The fuel is introduced into air stream via fuel injection holes that pass through the walls of the vanes which contain internal fuel flow passages. The flow field inside the premixer is broken up by the arrayed vanes into a series of small regions each containing a well designed small size mixing eddy which is steadily attached to the surface of the vanes.