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

Abstract

Emissions from aviation are a pressing topic today, and nitrogen oxides are among the most harmful emissions produced by turbofan engines. Tighter controls on NOx emissions are likely to become increasingly important, and reducing these emissions will be a key challenge in the coming years. Even under current regulations, significantly decreasing NOx without a performance penalty at a given design 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 turbofan engine and present major durability challenges due to the hostile operating environment. This thesis investigates the novel possibility of coating the internal surfaces of the low-pressure turbine of a turbofan engine with a durable catalytic alloy that acts as an integrated, albeit less efficient, catalytic converter. Building on previous work and in collaboration with NASA, a coupled model combining computational fluid dynamics and surface chemistry in 2D and was used to evaluate NOx conversion over a stator row in the first stage of the low-pressure turbine of the NASA E3 engine and lay the groundwork for 3D simulations. The aim was to assess the concept and provide an initial proof of principle for its viability. Several RANS models were used for flow simulations in COMSOL, culminating in a compressible k˘ω model and coupled chemistry was modelled using Chalmers catalyst data. The results suggest that further work is warranted and that integrated catalytic turbine surfaces represent a promising avenue for NOx reduction in aviation.