Dual-Zone Gas Turbine Combustor for NOx Reduction
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Solution Overview
Problem
Conventional annular combustors for gas turbine engines are ineffective in reducing NOx emissions across the entire range of engine operating conditions, particularly at low and moderate power settings, as they operate closer to stoichiometric fuel-to-air ratios during these conditions, failing to maintain the fuel-rich, quick quench, lean burn (RQL) combustion strategy's effectiveness.
Innovation Solution
The combustor design features a dual-zone combustion system with first and second fuel injectors arranged in the bulkhead and liners, respectively, to create a forward and downstream combustion zone, allowing for selective fuel and air distribution to achieve fuel-rich conditions at low power and fuel-lean conditions at high power, with a greater number of second fuel injectors to enhance NOx control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional single-zone combustors operate at low and moderate power settings, then fuel-to-air ratio approaches stoichiometric conditions, but NOx emissions cannot be effectively reduced
Solution Approach 1:
The combustor is divided into two separate combustion zones: a forward combustion zone with fuel injectors in the bulkhead and a downstream combustion zone with fuel injectors in the liners. This segmentation allows independent control of fuel-to-air ratios in each zone, enabling the forward zone to maintain fuel-rich conditions for NOx reduction while the downstream zone provides additional combustion control across different power settings
Solution Approach 2:
Different regions of the combustor are given different functional characteristics. The forward combustion zone is designed to operate fuel-rich specifically for NOx reduction, while the downstream combustion zone handles additional fuel combustion. This local differentiation allows the system to maintain effective NOx control at low and moderate power settings while still meeting overall combustion requirements across the full operating range
2Object-generated harmful factors
If dual-zone combustion system with multiple fuel injectors is implemented, then NOx emissions are reduced across all power settings, but device complexity increases
Solution Approach 1:
Both the forward and downstream combustion zones use similar fuel injector designs and combustion principles. The downstream fuel injectors, positioned in the liners aftward of the bulkhead, replicate the fuel injection functionality of the bulkhead injectors but in a different location. This universality allows the system to achieve complex dual-zone control while using standardized components, thereby managing device complexity
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 design achieves lower NOx emissions across all power settings by optimizing fuel distribution between the forward and downstream combustion zones, ensuring stable combustion and high efficiency while maintaining weight and operability equivalent to conventional combustors.
Implementation Method 1
combusting a first flow of fuel and a first flow of combustion air in a forward region of the combustor thereby establishing a forward combustion zone
Implementation Method 2
The swirlers impart a swirl to inlet air entering the forward end of the combustion chamber at the bulkhead to provide rapid mixing of the fuel and inlet air
Data Source
Figure 1~3
Figure 2
Figure 4
AI summary
A combustor (30) for a gas turbine engine includes a radially inboard liner (36), a radially outboard liner (38), and a bulkhead (34) that cooperatively define an annular combustion chamber (32), a plurality of first fuel injectors (54) that are disposed in the bulkhead (34), and a plurality of second fuel injectors (62) that are disposed in at least one of the inboard liner (36) and the outboard liner (38) aftward of the bulkhead (34). A method is also provided for operating the combustor (30) wherein fuel distribution between a forward combustion zone (60) and a downstream combustion zone (64) is selectively varied in response to the power operating mode of the gas turbine engine with an objective to control NOx formation.