Secondary Combustion System for Turbomachine Emissions Control
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Solution Overview
Problem
Existing lean direct injection (LDI) combustion systems in turbomachines face challenges with significant NOx emissions due to peak operation temperatures exceeding thermal NOx formation thresholds, requiring costly active cooling systems and non-uniform fuel and air distribution, which can lead to local hot streaks and increased energy consumption.
Innovation Solution
A combustion system with a primary and secondary reaction zone, where the secondary zone incorporates multiple injectors for adjusting the fluid distribution and utilizing a passive cooling system, eliminating the need for active cooling by leveraging compressor discharge airflow for cooling and fuel apportioning between zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If lean premixed combustion is used to reduce thermal NOx emissions, then NOx emissions are reduced, but the combustor cannot achieve high enough exit temperatures for some turbomachine requirements
Solution Approach 1:
The combustion system is divided into a primary combustion zone that operates with lean premixed combustion to minimize NOx formation, and a secondary combustion zone that adds heat to raise the exit temperature. This segmentation allows each zone to perform its specific function optimally without compromising the other.
Solution Approach 2:
A secondary combustion zone acts as an intermediary between the primary lean premixed combustion and the turbine inlet. This intermediate zone provides additional heat input through a separate fuel injection system, raising the gas temperature to required levels without disrupting the low-NOx combustion process in the primary zone.
2Temperature
If peak gas temperature is used to meet turbomachine temperature requirements, then combustor exit temperature is sufficient, but thermal NOx formation increases significantly
Solution Approach 1:
The combustion process is segmented into two distinct zones: primary combustion that controls NOx formation through lean premixed operation, and secondary combustion that controls exit temperature. This allows independent optimization of each parameter without trade-offs.
Solution Approach 2:
Different regions of the combustion system are given different functional qualities - the primary zone is optimized for low-NOx combustion with excess air, while the secondary zone is optimized for temperature control through additional fuel addition. Each local region performs its specific function with high effectiveness.
3Object-generated harmful factors
If lean direct injection is used to reduce NOx emissions, then NOx levels are reduced, but an active cooling system is required which consumes significant energy
Solution Approach 1:
The secondary combustion zone serves a dual function: it raises the combustor exit temperature to meet turbine requirements, and it provides thermal management for the combustion system. The heat released in the secondary zone compensates for the energy that would otherwise be consumed by active cooling systems, making the system self-sufficient for thermal control.
4Device complexity
If fixed injector position is used in LDI system, then system structure is simplified, but uniform distribution of fuel and air mixture is not achieved leading to local high-NOx regions
Solution Approach 1:
The injector system incorporates adjustable or movable components that allow the injection pattern and fluid distribution to be dynamically optimized. This enables uniform mixing of fuel and air throughout the combustion zone, preventing localized rich mixtures that would lead to high-NOx regions, while maintaining reasonable system complexity through standardized mechanical adjustment mechanisms.
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 optimizing temperature control and fuel distribution, minimizing the need for active cooling systems, and allowing for adjustable fluid injection, thereby enhancing turbomachine efficiency and reducing operational costs.
Implementation Method 1
a primary combustion system comprising at least one primary fuel nozzle that generates a stream of combustion products; a secondary combustion system located downstream of the primary combustion system; wherein the secondary combustion system comprises at least one injector for delivering a fluid into the stream of combustion products
Data Source
AI summary
An embodiment of the present invention provides a method and system of operating a combustion system that has Lean direct injection (LDI) functionality. The method and system provides a passive cooling system for an injector of the LDI system. The method and system may also provide a means to direct the flow of the fluid exiting the injector of the LDI system.