Gas Turbine Injector Shielding Air Flow for NOx Reduction
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Solution Overview
Problem
Existing distributed combustion systems face challenges in reducing NOx emissions due to high flame temperatures, which can be attributed to short residence times of reactants in the combustion stage, and inefficiencies in utilizing cooling air, leading to increased NOx production and reduced engine efficiency.
Innovation Solution
The implementation of injector assemblies that generate a shielding air flow to delay ignition of reactants, allowing for increased entrainment of combustion products and efficient reuse of cooling air to form a shielding flow, thereby reducing NOx emissions and enhancing mixing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If distributed combustion system is used to reduce NOx emissions, then NOx emissions are reduced, but flame temperature becomes too high
Solution Approach 1:
A shielding air flow is introduced as an intermediary substance between the fuel-air reactants and the combustion zone. This shielding air acts as a mediator that delays ignition and reduces flame temperature without requiring complex active control systems
Solution Approach 2:
Cooling air, which is inherently inert and non-combustible, is redirected to form a shielding flow around the reactants. This creates a localized inert environment that suppresses premature combustion and reduces flame temperature while maintaining the distributed combustion architecture
2Temperature
If cooling air is used for component cooling, then component temperature is controlled, but NOx emissions increase due to inefficiency
Solution Approach 1:
The cooling air serves dual functions: it cools the combustor components (original function) and forms a shielding flow to reduce flame temperature and NOx emissions (new function). This multi-functionality eliminates waste and improves overall system efficiency
Solution Approach 2:
Instead of discarding the cooling air after it passes through the combustor walls, the system recovers and redirects this air to form a shielding flow around the reactants, maximizing its utility and preventing NOx formation
3Object-generated harmful factors
If residence time of reactants is reduced to reduce NOx, then NOx emissions are reduced, but mixing performance deteriorates
Solution Approach 1:
The shielding air flow is established in advance before the reactants are introduced into the combustion zone. This preliminary action creates a protective environment that allows extended residence time for mixing while preventing premature ignition that would lead to high 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
This approach effectively reduces NOx emissions by lowering flame temperatures, increases the liftoff distance of the flame, and improves engine efficiency by reusing cooling air, achieving stable operation at high turbine inlet temperatures while maintaining low NOx levels and efficient combustion.
Implementation Method 1
delay ignition of reactants, allowing for increased entrainment of combustion products
Implementation Method 2
efficient reuse of cooling air to form a shielding flow
Data Source
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Figure 5
AI summary
Injector assemblies (12) and ducting arrangement including such injector assemblies are provided. The injector assembly may include a reactant-guiding structure arranged to convey a flow of reactants (19) into the combustion stage and means for injecting (24, 25, 26) a flow of air into the combustion stage. The flow of air injected into the combustion stage may be arranged to condition interaction of the flow of reactants injected into the combustion stage with a crossflow of combustion products, as the flow of reactants is admitted into the combustion stage.