Radial Fuel Injection Biasing for Combustion Stability
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Solution Overview
Problem
Gas turbine engines face challenges in minimizing nitrogen oxide (NOx) emissions and combustion instabilities, particularly in radial-staged lean combustors, due to concentrated heat release and weak flame holding at certain operating conditions.
Innovation Solution
The introduction of a radial fuel injection system downstream of an axial pilot fuel injection system in a gas turbine engine, featuring a swirler with multiple fuel injector orifices that allow for a selective fuel flow split and distribution, enhancing flame anchoring and stability through tailored fuel-air mixing and distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a radial-staged lean combustor configuration is used to minimize NOx emissions, then emissions are reduced, but combustion instabilities occur due to concentrated heat release and weak flame holding
Solution Approach 1:
The fuel injection system is segmented into multiple axial stages (pilot stage, intermediate stage, main stage) with distinct fuel injector orifices at different axial locations. This segmentation allows controlled distribution of heat release along the axial direction, preventing concentrated heat release at one location while maintaining lean combustion for low NOx emissions.
Solution Approach 2:
Different fuel injector orifices are provided with different diameters and positioned at different axial locations to create locally optimized fuel-air mixing zones. The pilot stage uses smaller orifices for stable flame holding, while the main stage uses larger orifices for high-load combustion, ensuring stable combustion across varying operating conditions without compromising emissions performance.
2Object-generated harmful factors
If main stage air is increased to support lean combustion, then NOx emissions are reduced, but flame holding capability deteriorates at certain operating conditions
Solution Approach 1:
The pilot stage fuel injection system is positioned upstream to establish a stable pilot flame before the main combustion zone. This preliminary action creates a reliable ignition source that maintains flame holding capability even when main stage air flow is increased for lean combustion operations, preventing flame extinction while achieving low NOx emissions.
Solution Approach 2:
The intermediate stage fuel injection acts as an intermediary between the pilot stage and main stage, providing a transition zone that bridges the gap between stable low-load combustion and high-load combustion. This intermediate stage ensures continuous stable combustion across the full operating range while maintaining the lean combustion benefits for emissions reduction.
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 configuration reduces NOx emissions and mitigates combustion instabilities by optimizing fuel distribution, ensuring stable combustion and improved dynamic stability in the combustor.
Implementation Method 1
an axial staged combustor including an axial pilot fuel injection system and a radial main fuel injection system downstream of the axial pilot fuel injection system
Implementation Method 2
Arrays of circumferentially distributed combustion air holes penetrate multiple axial locations along each liner to radially admit the pressurized air into the combustion chamber
Implementation Method 3
the first set of fuel injector orifices, having a larger diameter, is arranged to bias a circumferential fuel distribution profile within the swirler
Implementation Method 4
Gas turbine engines, such as those which power modern commercial and military aircrafts, include a compressor for pressurizing a supply of air, a combustor for burning a hydrocarbon fuel in the presence of the pressurized air
Data Source
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AI summary
An injector (200) of a radial fuel injection system for a combustor of a gas turbine engine includes a swirler (204); and a fuel nozzle (202) located within the swirler (204), the fuel nozzle (202) operable to provide a biased circumferential fuel distribution within the swirler (204).