Counter-Directional Swirl Air Swirler for Lean Combustion Stability
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Solution Overview
Problem
Gas turbine engines face challenges in reducing NOx, carbon monoxide, and hydrocarbon emissions due to high flame temperatures and incomplete combustion, particularly when operating under fuel lean conditions, and existing air swirler designs are inadequate for efficient mixing of gaseous fuel and air.
Innovation Solution
The air swirler assembly features a plurality of fuel injection ports and air passages with counter- and co-directional swirls to enhance mixing, including inner, outer, and secondary air passages, ensuring rapid and uniform fuel-air mixing, which helps in achieving fuel lean conditions and reducing emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the combustor operates under fuel lean conditions to lower flame temperature and reduce NOx emissions, then NOx emissions are reduced, but combustion instability and flame-out may occur
Solution Approach 1:
The air supply is segmented into multiple passages (first inner air passage, second inner air passage, outer air passage) that deliver air to different regions of the mixing chamber. This segmentation allows different zones to have different air-fuel mixing characteristics, enabling stable combustion under fuel-lean conditions by ensuring adequate mixing in all regions while maintaining overall lean operation.
Solution Approach 2:
Swirl vanes are installed in each air passage to impart rotational motion to the air flow. The curved geometry of the swirl vanes creates swirling flows that enhance mixing between fuel and air through centrifugal forces and increased turbulence, ensuring complete combustion and preventing flame-out even under fuel-lean conditions.
2Productivity
If multi-pass air swirlers are used to enhance fuel-air mixing, then mixing efficiency is improved, but device complexity increases
Solution Approach 1:
The air supply system is divided into multiple independent passages (first inner, second inner, and outer air passages), each equipped with its own swirl vanes. This segmentation allows each passage to be optimized for specific mixing requirements while maintaining modular simplicity in the overall design, balancing mixing efficiency with structural manageability.
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 design improves fuel-air mixing efficiency, reducing NOx, carbon monoxide, and hydrocarbon emissions by creating a stable and uniform combustion environment, suitable for supersonic cruise vehicles powered by gas turbine engines.
Implementation Method 1
A first swirl vane assembly imparts a swirl to an air flow passing through the first inner air passage and a second swirl vane assembly imparts a counter-directional swirl to an air flow passing through the second inner air passage
Implementation Method 2
an air flow passing through the second inner air passage has a swirl imparted thereto that is counter-directional to a swirl imparted to an air flow passing through the first inner air passage
Data Source
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AI summary
An air swirler, a fuel and air admission assembly, and a staged combustor are disclosed. The air swirler (20) has a number of air passages (76, 78), and the air in the different passages can be made to swirl in different directions to improve mixing. The fuel and air assembly has inner and outer fuel ports, which allow fuel to be introduced to different regions of the assembly at the same time. The staged combustor may be equipped with the fuel and air admission assemblies incorporating the air swirlers for use in gas turbine engines, such as for example gas turbine engines powering aircraft having supersonic cruise capability.