Design and Evaluation of a Multitubular Catalytic Membrane Reactor for Onboard Ammonia Cracking in Commercial Aviation

Abstract Ammonia is a promising zero-carbon fuel for aviation, but its low flame speed and high ignition temperature hinder direct use in gas turbines. While a blend of ammonia and hydrogen can enable stable combustion, supplying hydrogen onboard through storage poses significant technical challenges. To address this, we propose an onboard ammonia cracking system based on a novel multitubular catalytic membrane reactor that can decompose ammonia to hydrogen during flight. The reactor comprises 16 microtubes (1.05 m length, 0.1 m outer, 0.04 m inner diameter), each featuring a 0.75 m palladium membrane section for hydrogen separation and a 0.3 m silica membrane section for nitrogen removal. A detailed simulation model incorporating reaction kinetics, multicomponent diffusion, and permeation behavior is developed to assess performance. At 450 °C and 30 bar, the system achieves over 98.9% ammonia conversion with minimal pressure drop, processing up to 180 g/s per tube. Sensitivity analyses confirm strong thermal efficiency, scalability, and reactor stability under varying flow and packing conditions. The system is benchmarked against the fuel demands of Rolls-Royce Trent 900 and GP7000 engines, demonstrating feasibility for integration into large commercial aircraft such as the Airbus A380. This design offers a viable pathway toward zero-carbon, hydrogen-ammonia sustainable aviation fuel systems.