CFD Analysis of a Low-Pressure Turbine for Evaluating High-Temperature NOx Emission Control Catalysts in Turbofan Engines

Sammanfattning

Emissions from aviation are a pressing topic today, and nitrogen oxides are amongthe most harmful emissions produced by turbofan engines. Tighter controls onNOx emissions are likely to become increasingly important, and reducing theseemissions will be a key challenge in the coming years. Even under current regulations,significantly decreasing NOx without a performance penalty at a givendesign point could enable new high-efficiency engine designs.The common solution for NOx reduction in other industries is a catalytic converter.However, such a device would incur severe performance losses in a turbofanengine and present major durability challenges due to the hostile operatingenvironment.This thesis investigates the novel possibility of coating the internal surfaces of thelow-pressure turbine of a turbofan engine with a durable catalytic alloy that acts asan integrated, albeit less efficient, catalytic converter. Building on previous workand in collaboration with NASA, a coupled model combining computational fluiddynamics and surface chemistry in 2D and was used to evaluate NOx conversionover a stator row in the first stage of the low-pressure turbine of the NASA E3engine and lay the groundwork for 3D simulations. The aim was to assess theconcept and provide an initial proof of principle for its viability. Several RANSmodels were used for flow simulations in COMSOL, culminating in a compressiblek˘ω model and coupled chemistry was modelled using Chalmers catalyst data.The results suggest that further work is warranted and that integrated catalyticturbine surfaces represent a promising avenue for NOx reduction in aviation.