Radial Fuel Injection Combustor for NOx Reduction
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Solution Overview
Problem
Gas turbine engines face challenges in minimizing nitrogen oxide (NOx) emissions due to the formation of NOx at elevated combustion flame temperatures during the rich burn, quick quench, lean burn (RQL) combustion process, despite efforts to derich the fuel-rich combustion products and reduce flame temperature.
Innovation Solution
A dual fuel injection system is implemented in the gas turbine engine, comprising a forward fuel injection system and a downstream fuel injection system that surrounds the combustion chamber, with multiple fuel nozzle assemblies axially upstream of a necked region and within a significant portion of the combustor, to optimize fuel-air mixing and reduce NOx formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a stoichiometrically excessive quantity of fuel is introduced into the rich burn zone, then the energy content of the fuel is partially released, but NOx formation still occurs at elevated combustion flame temperatures
Solution Approach 1:
The fuel injection system is divided into multiple zones: a forward fuel injection system introducing fuel axially into the rich burn zone, and a downstream fuel injection system introducing fuel radially into the quench zone. This segmentation allows different regions to perform different functions - the forward system provides primary combustion while the downstream system controls flame temperature and reduces NOx formation in the quench zone.
Solution Approach 2:
Different fuel injection characteristics are applied to different spatial locations. The forward fuel injection system uses axial injection for efficient combustion in the rich burn zone, while the downstream fuel injection system uses radial injection to uniformly distribute fuel and control temperature in the quench zone, thereby locally optimizing both energy release and NOx reduction.
2Stability of the object's composition
If pressurized air jets radially enter the quench zone to derich combustion products, then the fuel-air ratio changes from fuel rich to stoichiometric causing flame temperature to rise, but this initial quench process produces quantities of NOx
Solution Approach 1:
The downstream fuel injection system introduces fuel radially into the quench zone before the combustion products complete their transition through this region. This preliminary fuel addition ensures that as air mixes in and the fuel-air ratio approaches stoichiometric, there is already sufficient fuel present to maintain controlled combustion and limit temperature spikes that would generate excessive NOx.
Solution Approach 2:
The downstream fuel injection system acts as an intermediary between the rich burn zone and the lean burn zone. By introducing fuel radially in the quench zone, it mediates the transition process, ensuring smooth deriching of combustion products while maintaining flame temperatures within acceptable limits to minimize NOx formation.
3Temperature
If additional pressurized air is supplied in the lean burn zone to regulate peak temperature, then turbine exposure to excessive temperatures is reduced, but the complexity of the fuel injection system increases
Solution Approach 1:
The fuel injection system is segmented into forward and downstream components with distinct functions. The downstream fuel injection system, positioned radially in the quench zone, provides temperature control functionality that would otherwise require additional air supply systems in the lean burn zone. This segmentation consolidates temperature regulation into the existing dual-injection architecture rather than adding separate systems.
Solution Approach 2:
The downstream fuel injection system serves multiple functions: it continues the deriching process initiated in the quench zone, maintains controlled flame temperatures during the fuel-air ratio transition, and regulates peak temperatures before products enter the lean burn zone. This multi-functionality eliminates the need for separate temperature regulation systems, reducing overall system complexity while achieving effective temperature control.
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 dual fuel injection system effectively reduces NOx emissions by controlling the fuel-air ratio and flame temperature, enhancing combustion efficiency and minimizing turbine exposure to excessive temperatures and temperature gradients.
Implementation Method 1
a combustor for burning a hydrocarbon fuel in the presence of the pressurized air
Implementation Method 2
The dual fuel injection system effectively reduces NOx emissions by controlling the fuel-air ratio and flame temperature
Data Source
AI summary
A combustor for a gas turbine engine includes an forward fuel injection system in communication with a combustion chamber and a downstream fuel injection system that communicates with the combustion chamber downstream of the forward fuel injection system.