Aircraft Engine Catalyst Coating for NOx Reduction
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Solution Overview
Problem
Current solutions for reducing nitrogen oxide emissions in aircraft gas turbine engines, such as catalytic converters and Selective Catalytic Reduction (SCR) systems, are not practical due to their impact on thrust efficiency.
Innovation Solution
A gas turbine engine design that incorporates a catalyst in the hot post-combustion section, where nitrogen oxides are converted into diatomic nitrogen and water using an exhaust fluid additive, such as diesel exhaust fluid (DEF), injected upstream of the catalyst.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a catalytic converter or SCR system is fitted to a gas turbine engine to reduce nitrogen oxide emissions, then emissions are reduced, but thrust efficiency is negatively affected
Solution Approach 1:
The invention divides the gas turbine engine into two separate air flow paths: a core stream that passes through the combustion chamber and catalyst for NOx reduction, and a bypass stream that circumvents these components. This segmentation allows the catalyst to treat only a portion of the exhaust gases, minimizing its impact on overall thrust while still achieving emission reductions.
Solution Approach 2:
The catalyst is applied locally to specific surfaces within the core stream path, such as turbine blades or nozzle walls, rather than requiring a separate catalytic converter component. This localized application reduces the overall volume and impact of the catalyst on the engine's thrust-generating flow path.
2Object-generated harmful factors
If a catalytic converter is used to reduce nitrogen oxide emissions, then emissions are reduced, but device complexity increases
Solution Approach 1:
The catalyst function is merged with existing engine components such as turbine blades, compressor blades, or nozzle structures. By coating these existing surfaces with catalytic material, the invention eliminates the need for a separate catalytic converter assembly, thereby reducing system complexity while maintaining NOx reduction capability.
Solution Approach 2:
Existing engine components are given multiple functions: they continue to perform their primary aerodynamic roles while also serving as substrates for the catalyst to reduce NOx emissions. This multi-functionality reduces the number of separate components needed in the system.
3Object-generated harmful factors
If SCR is applied to a gas turbine engine to reduce nitrogen oxide emissions, then emissions are reduced, but thrust efficiency is negatively affected
Solution Approach 1:
The SCR system is implemented only in the core stream portion of the engine, while the bypass stream remains unaffected. This segmentation ensures that the chemical reduction process occurs in a controlled region that represents only a fraction of the total exhaust flow, minimizing the impact on overall thrust generation.
Solution Approach 2:
The exhaust fluid additive is injected at specific locations within the core stream, and the catalyst is positioned on specific surfaces within the same stream. This localized implementation confines the SCR chemistry to a specific region, preventing it from interfering with the broader thrust-generating airflow.
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 solution effectively reduces nitrogen oxide emissions while minimizing the impact on thrust efficiency by limiting the catalyst's presence to the core thrust region and using a bypass section to maintain propulsive efficiency.
Implementation Method 1
The catalyst is configured to convert nitrogen oxides into diatomic nitrogen and water in the presence of an exhaust fluid additive
Implementation Method 2
nitrogen oxides are converted into diatomic nitrogen and water using an exhaust fluid additive
Implementation Method 3
The catalyst being arranged downstream of the exhaust fluid additive injection site helps with the dispersion/mixing of exhaust fluid additive (because of it being injected into turbulent air passing through the gas turbine engine)
Implementation Method 4
the hot post-combustion section is where the combusted air and fuel performs work on hot post-combustion turbine blades
Data Source
AI summary
An aircraft engine incudes: a catalyst, e.g. platinum, applied to turbine blades (580c, 590c) and/or to a catalytic grid downstream of the engine's combustion chamber. An exhaust fluid additive injection system is incorporated upstream of the catalyst via a line 560, in a stator blade within the engine. The catalyst is used to reduce NOx emissions from the engine by a Selective Catalytic Reduction reaction.