Late Lean Injection Fuel Staging for Gas Turbine NOx Reduction
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Solution Overview
Problem
Gas turbine engines face inefficiencies and high NOx emissions due to high combustion temperatures, which are challenging to mitigate with conventional premixed lean fuels, leading to significant thermal NOx formation.
Innovation Solution
The implementation of a late lean injection (LLI) system in gas turbine engines, featuring a combustor with a transition zone and multiple fuel injectors configured for staged fuel delivery, allowing for flexible fuel staging and air split control to manage combustion temperatures and reduce NOx formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional premixed lean fuels are used in gas turbine engines, then combustion efficiency can be maintained, but thermal NOx emissions increase significantly due to high combustion temperatures
Solution Approach 1:
The combustion process is divided into two distinct stages: a first combustion stage in the combustor using conventional premixed lean fuel, and a second combustion stage in the transition zone using late lean injection fuel. This segmentation allows each stage to operate under optimized conditions - the first stage maintains efficiency while the second stage controls temperatures to minimize NOx formation
Solution Approach 2:
Different fuel injection strategies are applied to different spatial zones: the combustor uses premixed lean injection for efficient combustion, while the transition zone receives late lean injection to maintain lower temperatures and reduce NOx. This local differentiation of combustion characteristics resolves the contradiction between efficiency and emissions
2Power
If combustor temperature is increased to maintain required combustion product temperatures, then energy output is improved, but thermal NOx formation threshold is exceeded
Solution Approach 1:
The temperature control function is segmented between two combustion zones: the combustor generates high temperatures for required thermal output, while the transition zone operates at lower temperatures to prevent excessive NOx formation. The late lean injection in the transition zone provides just enough energy to maintain product temperatures without exceeding NOx thresholds
Solution Approach 2:
The injection timing and fuel distribution parameters are changed to achieve staged combustion. By injecting fuel later in the process in the transition zone rather than premixing it, the combustion occurs at lower peak temperatures, changing the thermal parameters to stay below NOx formation thresholds while maintaining overall energy output
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 enables efficient operation by creating local zones of stable combustion, reducing NOx emissions, and allowing for the use of more reactive fuels, thereby improving engine efficiency and emissions control.
Implementation Method 1
a second fuel supplied thereto by the fuel circuit and the products of the combustion of the first fuel are combustible
Data Source
AI summary
A gas turbine engine is provided and includes a combustor having a first interior in which a first fuel supplied thereto is combustible, a turbine, including rotating turbine blades, into which products of at least the combustion of the first fuel are receivable to power a rotation of the turbine blades, a transition zone, including a second interior in which a second fuel supplied thereto and the products of the combustion of the first fuel are combustible, the transition zone being disposed to fluidly couple the combustor and the turbine to one another, and a plurality of fuel injectors, which are supported by the transition zone and coupled to a fuel circuit, and which are configured to supply the second fuel to the second interior in any one or more of a single axial stage, multiple axial stages, a single axial circumferential stage and multiple axial circumferential stages.