Multi-Staged Turbine Combustor for Low NOx Emissions
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Solution Overview
Problem
Current turbine engine combustors face challenges in balancing NOx, nvPM, CO, and UHC emissions across various power operations, with high fuel-air ratios leading to increased NOx emissions and incomplete combustion at low power, and traditional designs failing to optimize stoichiometry for advanced engine cycles.
Innovation Solution
A multi-staged combustor system incorporating radial and axial staging with a nested flame structure and secondary combustion chambers to achieve lean combustion, utilizing a pilot mixer and main mixers for fuel and air injection, and secondary combustion chamber swirlers to enhance flame stability and reduce NOx emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high fuel-air ratios are used to maintain combustion efficiency at low power, then combustion efficiency is improved, but NOx emissions increase
Solution Approach 1:
The combustor is divided into multiple combustion zones (primary combustion zone, secondary combustion zone, tertiary combustion zone) with different fuel-air ratios. The primary zone uses higher fuel-air ratio for efficiency at low power, while secondary and tertiary zones use lower fuel-air ratios to reduce NOx emissions, thereby segmenting the combustion process to address the contradiction between efficiency and emissions.
Solution Approach 2:
Different regions of the combustor are assigned different stoichiometric conditions. The primary combustion zone operates with richer mixture for efficiency, while secondary and tertiary zones operate with leaner mixtures to control temperatures and reduce NOx formation locally, creating a spatial variation in combustion characteristics to resolve the contradiction.
2Device complexity
If traditional combustor designs are used, then structural simplicity is maintained, but emissions optimization across various power operations is insufficient
Solution Approach 1:
The combustor is segmented into multiple zones with independent fuel injection and air supply systems, allowing each zone to be optimized for specific emission control functions. This segmentation enables the combustor to achieve comprehensive emissions optimization across various power operations while maintaining a relatively simple overall structure through modular zone design.
Solution Approach 2:
The combustor incorporates variable geometry features including movable partition walls and adjustable fuel injection rates for each combustion zone, enabling dynamic adaptation to different operating conditions. This dynamic capability allows the combustor to optimize emissions performance across the entire power range without requiring complete structural redesign.
3Object-generated harmful factors
If lean combustion is implemented to reduce NOx emissions, then NOx emissions are reduced, but combustion stability deteriorates
Solution Approach 1:
The combustion process is segmented into multiple zones where the primary zone can operate with richer mixtures to ensure stability and ignition, while secondary and tertiary zones operate with leaner mixtures to reduce NOx emissions. This segmentation allows the system to achieve both stability and low emissions by distributing different combustion characteristics across spatial zones.
Solution Approach 2:
The primary combustion zone performs preliminary combustion of a richer mixture to establish stable flame and generate initial heat release before the leaner mixtures in secondary and tertiary zones are introduced. This preliminary action ensures combustion stability is established first, allowing subsequent lean combustion zones to operate stably with reduced NOx emissions.
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 multi-staged combustor design significantly reduces NOx emissions by up to 50% below regulatory limits, while maintaining efficient combustion and operability across the entire mission cycle of a turbine engine, achieving improved stoichiometric capabilities and reduced emissions.
Implementation Method 1
utilizing a pilot mixer and main mixers for fuel and air injection
Implementation Method 2
A combustor is arranged in the core section to generate combustion gases for driving a turbine of the turbine engine
Implementation Method 3
secondary combustion chamber swirlers to enhance flame stability
Data Source
AI summary
A combustor for a turbine engine includes a main combustion chamber, an annular dome, and a secondary combustion chamber positioned downstream of the annular dome. A plurality of first mixing assemblies are disposed through the annular dome and include a pilot mixer. The pilot mixer injects a pilot mixer fuel-air mixture axially into the main combustion chamber and generates a first recirculation zone within the main combustion chamber. A plurality of second mixing assemblies are disposed at the secondary combustion chamber axially aft of the first mixing assemblies and include a main mixer. The main mixer injects a main mixer fuel-air mixture into the secondary combustion chamber to produce combustion gases and to generate a second recirculation zone within the secondary combustion chamber axially aft of the first recirculation zone. The secondary combustion chamber injects the combustion gases into the main combustion chamber.