Investigation of Triply Periodic Minimal Surfaces as an Ammonia Cracking Structure

In a novel turbofan design, ammonia will be utilized as a hydrogen carrier to eliminate carbon emissions. High fuel flow rate and pressure requirements for aviation engines bring the need for advanced catalytic and heat transfer structures within an ammonia cracker. In this analysis, triply periodic minimal surfaces (TPMS) will be investigated in CFD simulations as a potential reactor structure due to their high surface area and heat transfer capabilities. Simulations were conducted in ANSYS Fluent with the SST k-ω turbulent model. By employing a CHEMKIN surface reaction mechanism tuned for pressures up to 20 bar, diamond (Schwarz-D) and gyroid geometries were investigated for their effects on ammonia conversion efficiency in comparison to a smooth reactor structure. It was found that TPMS geometries increased ammonia conversion by 17-23% compared to the smooth cases. TPMS structures enhanced catalytic surface area, improved heat distribution, and induced mixing within the channel at a low pressure drop cost. This CFD model will inform the design of the cracker and larger engine cycle and acts as an advancement towards the reduction of carbon emissions in the aviation industry.