Downstream Fuel Injection for Gas Turbine NOx Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in gas turbine engines is to reduce NOx emissions while maintaining higher operating temperatures and efficiency, as existing technologies face limitations in controlling residence time and emissions of CO and UHC with downstream injection.
Innovation Solution
A two-stage downstream injection system is implemented, with the first stage positioned at least 6 milliseconds aft of the primary injection system and the second stage positioned less than 2 milliseconds from the combustor end-plane, using multiple injectors to inject air and fuel at specific axial locations to optimize residence time and combustion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher operating temperatures are used to improve engine efficiency, then engine efficiency is improved, but NOx emissions increase
Solution Approach 1:
The combustor is divided into multiple zones with different injection stages (primary, intermediate, and final stages) along the flowpath. Each stage injects fuel at specific locations to create distinct combustion regions, allowing temperature and residence time control in different zones to reduce NOx while maintaining overall efficiency
Solution Approach 2:
Different regions of the combustor are given different local characteristics through staged injection. The primary stage creates a high-temperature zone for efficient combustion, while intermediate and final stages add fuel in regions with shorter residence times to maintain combustion without excessive NOx formation. Each zone has optimized local temperature and mixing conditions
2Object-generated harmful factors
If downstream injection is used to reduce NOx emissions, then NOx emissions are reduced, but residence time control becomes limited affecting CO and UHC emissions
Solution Approach 1:
The injection system is segmented into multiple stages positioned at different axial locations downstream of the primary injection. The intermediate stage is positioned 0.15-0.30D from the primary injection, and the final stage is positioned 0.30-0.45D from the primary injection, where D is the combustor diameter. This segmentation creates multiple opportunities to control residence time at different points in the flowpath
Solution Approach 2:
The system dynamically controls residence time by adjusting the timing and amount of fuel injection at each stage. The intermediate and final stage injections are timed to extend the combustion process into regions with shorter residence times, allowing flexible adaptation of residence time characteristics to meet both NOx and CO/UHC emission requirements
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 reduces NOx emissions by shortening the residence time of reactants at high temperatures, allowing for higher combustor firing temperatures and improved engine efficiency while maintaining acceptable emission levels.
Implementation Method 1
A first residence time comprises a period of time during a predetermined mode of engine operation in which combustion flow takes to travel along the interior flowpath from a first position defined at the primary air and fuel injection system to a second position defined at the first stage of the downstream injection system
Implementation Method 2
a combustor coupled to a turbine that together define an interior flowpath, the interior flowpath extending aftward about a longitudinal axis from a primary air and fuel injection system
Data Source
AI summary
A gas turbine that includes: a combustor coupled to a turbine that together define an interior flowpath, the interior flowpath extending aftward about a longitudinal axis from a primary air and fuel injection system that defines a forward end, through an interface at which the combustor connects to the turbine, and through a row of stator blades in the turbine that defines an aft end; and a downstream injection system that includes two injection stages, a first stage and a second stage, that are axially spaced along the longitudinal axis of the interior flowpath. The first stage and the second stage each includes multiple injectors configured to inject an air and fuel mixture into the interior flowpath.