Lean-Direct Injectors for Gas Turbine Combustor NOx Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing combustion systems face challenges in reducing NOx emissions due to difficulties in achieving uniform fuel-air mixing, leading to locally stoichiometric zones and increased NOx formation, as well as issues with flame holding and flashback in lean-premixed combustors.
Innovation Solution
Combining lean-premixed combustion with axially-staged lean-direct injection concepts, where lean-direct injectors are used to facilitate rapid and uniform mixing of air and fuel, reducing NOx emissions by stabilizing lean premixed turbulent flames and minimizing flashback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If lean-direct injection is used to rapidly mix fuel and air, then mixing speed is improved, but uniformity of mixing deteriorates leading to locally stoichiometric zones
Solution Approach 1:
The combustor is divided into multiple combustion zones with separate fuel and air injection systems. Each zone has its own injectors positioned to create distinct mixing patterns, preventing localized stoichiometric conditions while maintaining rapid overall mixing. The segmentation of injection points and zones allows control over mixing uniformity without sacrificing speed.
Solution Approach 2:
Different regions of the combustor are designed with locally optimized injection characteristics. Fuel and air injectors are positioned and configured to create appropriate local mixing conditions in each zone, ensuring that no single region develops stoichiometric proportions. This local quality control prevents NOx formation hotspots while maintaining high mixing rates.
2Object-generated harmful factors
If lean-premixed combustion is used to reduce NOx emissions, then NOx formation is reduced, but flame stability deteriorates causing flashback and blowout
Solution Approach 1:
The combustor system dynamically adjusts fuel and air injection rates based on operating conditions. Multiple injection zones allow the system to adapt the fuel-air mixture composition and velocity profiles in real-time, maintaining flame stability across varying loads while preserving lean combustion characteristics. This dynamic control prevents flashback during low-load operation and maintains stability during transients.
Solution Approach 2:
Secondary air injection zones act as intermediaries between the primary fuel injection and the combustion chamber. These intermediate zones provide additional mixing and temperature control, stabilizing the flame front and preventing flashback to the injectors. The intermediary air zones buffer the lean mixture, maintaining reliability without sacrificing NOx reduction.
3Productivity
If longer residence time is provided for complete combustion, then combustion completeness is improved, but NOx formation increases due to prolonged exposure to high temperatures
Solution Approach 1:
The combustion process is segmented into multiple zones with different residence times and temperature profiles. Primary combustion occurs in controlled zones with sufficient residence time for complete fuel oxidation, while subsequent zones provide cooler environments that complete the combustion process without sustaining high temperatures. This segmentation achieves both combustion completeness and NOx reduction by decoupling the time-temperature exposure.
Solution Approach 2:
The design rushes the fuel through high-temperature zones quickly to complete the primary combustion reaction, then immediately transitions the products through cooler zones where remaining combustion occurs at lower temperatures. This rushing through of the combustion process minimizes the residence time at peak temperatures, reducing NOx formation while maintaining combustion completeness through the multi-zone approach.
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 effectively reduces NOx emissions by stabilizing combustion, reducing flashback, and enhancing the operability of combustion systems, while allowing for shorter residence times and increased fuel flexibility, thus improving the efficiency and compliance of gas turbine systems.
Implementation Method 1
lean-direct injectors are used to facilitate rapid and uniform mixing of air and fuel
Implementation Method 2
stabilizing lean premixed turbulent flames
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A gas turbine combustor system is provided. The gas turbine combustor system includes a combustion liner (50) including a center axis, an outer wall, a first end (56,62,80), and a second end (60,82), the outer wall is orientated substantially parallel to the center axis, a transition piece (52) coupled to the liner second end, the transition piece including an outer wall, and a plurality of lean-direct injectors (64) spaced axially along at least one of the liner outer wall and the transition piece outer wall.