Multistaged Lean Prevaporizing Fuel Injector for Low NOx Combustion
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Solution Overview
Problem
Gas turbine engines face challenges in reducing NOx emissions due to high temperatures and lean combustion conditions, which lead to incomplete combustion and instability, especially when handling fuel composition changes.
Innovation Solution
A multistaged lean prevaporizing premixing dual fuel injector is designed to finely atomize and vaporize liquid fuel using high-temperature combustion air, ensuring stable combustion and low NOx emissions by achieving thorough fuel and air mixing before combustion, thereby avoiding issues like coking, flashback, and autoignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If lean combustion conditions are used to reduce NOx emissions, then NOx emissions are reduced, but combustion stability deteriorates and incomplete combustion occurs
Solution Approach 1:
The combustion process is divided into multiple stages with different air-fuel ratios. A first fuel injector provides a richer mixture (e.g., 0.6-0.8 lambda) for stable combustion, while a second fuel injector provides a leaner mixture (e.g., 0.3-0.6 lambda) for lower NOx emissions. This segmentation allows each stage to operate in its optimal combustion regime, resolving the contradiction between stability and emissions.
Solution Approach 2:
Different regions of the combustion system are assigned different fuel-air mixture qualities. The core combustion zone receives a richer mixture to ensure stability, while outer regions receive leaner mixtures to reduce NOx formation. This local differentiation allows simultaneous achievement of stable combustion and low emissions.
2Object-generated harmful factors
If very lean combustion conditions are used to lower temperatures and reduce NOx, then NOx emissions are reduced, but combustion cannot be sustained
Solution Approach 1:
A pilot fuel injection stage is implemented before the main lean combustion stage. The pilot injection establishes a stable flame core with richer mixture, which then serves as the ignition source and stability anchor for the subsequent lean main combustion. This preliminary action enables the system to sustain lean combustion that would otherwise be impossible.
Solution Approach 2:
The pilot flame acts as an intermediary between the fuel injection system and the lean main combustion. It mediates the energy transfer and stabilizes the combustion process, allowing the lean main combustion to proceed without extinguishing. This intermediary enables sustained lean operation.
3Object-generated harmful factors
If lean premixed combustion is used to achieve low NOx emissions, then NOx emissions are reduced, but the system becomes sensitive to fuel composition changes
Solution Approach 1:
The fuel injection system is designed with dynamic control capabilities that allow real-time adjustment of fuel-air ratios and injection timing. When fuel composition changes are detected or anticipated, the control system dynamically modifies the operation of different fuel injectors to maintain optimal combustion. This dynamic adaptation preserves both low NOx emissions and tolerance to fuel variations.
Solution Approach 2:
The system can change operational parameters (fuel injection rates, air-fuel ratios, injection timing) in response to fuel composition changes. By adjusting these parameters across different combustion stages, the system maintains stable low-NOx combustion regardless of fuel variability, thereby improving adaptability.
4Manufacturing precision
If high-temperature combustion air is used for prevaporization, then fuel vaporization and mixing are improved, but the risk of autoignition and flashback increases
Solution Approach 1:
The prevaporization process is segmented into multiple zones with progressively higher temperatures. The first zone uses moderate temperature air for initial vaporization, while subsequent zones use progressively hotter air for complete vaporization. This segmentation allows thorough mixing without exposing the fuel-air mixture to temperatures that would cause premature autoignition or flashback.
Solution Approach 2:
Fuel vaporization and pre-mixing are performed in advance in controlled zones before the mixture reaches the high-temperature combustion region. This preliminary action ensures complete vaporization and mixing occurs at lower temperatures, eliminating the risk of autoignition and flashback while still achieving high mixing quality.
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 solution achieves stable combustion and significantly reduces NOx emissions below 9 ppmv, improving system reliability and tolerance to fuel composition changes while maintaining combustion stability and efficiency.
Implementation Method 1
A liquid fuel injection nozzle is located centrally within the inner tubular wall and receives liquid fuel through a liquid fuel supply passage and atomization air through atomization air supply passage
Implementation Method 2
the fuel and air preparation process to finely atomize, fully vaporize the liquid fuel and then fully mix the fuel with combustion air prior to the onset of the combustion process
Implementation Method 3
High temperature air is used to provide energy for vaporizing the atomized liquid fuel droplets
Implementation Method 4
A final flow distributor is located upstream of the final prevaporizing premixing chamber for distributing a fuel-air mixture of the first and second fuels and air across a cross section of the final prevaporizing premixing chamber
Data Source
AI summary
A multistaged lean prevaporizing premixing fuel injector apparatus is provided. The fuel injector may be utilized with a turbogenerator. Preheated combustion air from the turbogenerator's recuperator may be utilized by the fuel injector to prevaporize liquid fuel. The injector may provide for premixing of multiple fuel streams and include multiple stages with a flow distributor plate separating adjacent stages. The injector may include multiple stages, with a pilot tube located in a final stage splitting the fuel stream into a premixed pilot stream and a premixed final fuel and air mixture stream.