Structural Design and Analysis for a DeNOₓ Catalyst in Aviation

Abstract

Nitrogen oxides, collectively known as NOₓ, are compounds that can cause health damage to humans, lead to smog production and acid rain, and cause the formation of ground-level ozone that is detrimental to life. NOₓ formation in aircraft engines occurs because of high-temperature reactions between the nitrogen and oxygen naturally present in the air and is a spontaneous and unintended pollutant. One technology that has proven effective in controlling NOₓ emissions in other industries is selective catalytic reduction (SCR). As a post-combustion emissions control (PCEC) exhaust treatment, the technology works by introducing a nitrogen-rich reductant into the exhaust stream, then passing the flow through a catalyst. This device facilitates reactions between the dosed exhaust flow and catalyst wall to create harmless N₂ and H₂O at the cost of lost engine efficiency due to adding back pressure to the engine system. In prior work, a “pleated filter” design of an SCR catalyst was proposed as a potential solution for reducing NOₓ in aviation. The work covered in this thesis describes the design and analysis approach of such a device to meet the dynamic loads encountered during flight. A multi-level structural finite element analysis (FEA) of both the honeycomb plates is needed to enable this technology and of the frame components that support these plates. Using a stiffness matrix approach, the honeycomb catalyst was simplified into equivalent panels that were used to analyze the catalyst overall structure. The overall additional weight from the structure necessary to support this novel catalyst is estimated to be between 80-90 kg, which is within the additional mass required that was estimated in the original work. This implies that this design is structurally feasible.