Keywords

Supercritical, Ammonia Cracking, turbofan, Aircraft Engine, CO2, heat exchanger

Subject Categories

Aerospace Engineering | Heat Transfer, Combustion

Abstract

The aviation industry’s transition toward lower-carbon propulsion systems has accelerated interest in alternative fuels, including ammonia–hydrogen fuel blends. In this work, a supercritical CO2 Brayton cycle is integrated with the exhaust stream of a turbofan engine to recover waste heat and utilize it for ammonia preheating and cracking. The recovered thermal energy raises the ammonia temperature to the level required for catalytic decomposition, enabling onboard hydrogen production. The proposed architecture combines ammonia cracking with a high-bypass, two-shaft turbofan engine representative of the propulsion system employed on the Boeing 737 MAX 8. This approach addresses the challenges associated with onboard hydrogen storage while simultaneously enhancing ammonia combustion performance and reducing NOx emissions. The present study focuses on the development of a counterflow heat exchanger incorporating a triply periodic minimal surface (TPMS) core for thermal energy exchange between supercritical CO2 and NH3. Owing to their large surface-area-to-volume ratios and interconnected flow passages, TPMS structures offer enhanced heat transfer capabilities relative to conventional smoothtube configurations. Computational investigations were performed to characterize the fluid flow and thermal behavior using experimentally relevant operating conditions for both working fluids. To reduce the computational expense of the conjugate heat transfer simulations, the CFD analysis was divided into separate core and header domains. The conjugate model simultaneously resolves fluid flow in the hot and cold channels together with heat conduction through the TPMS structure and outer shell. Periodic and symmetry boundary conditions were employed to estimate exchanger performance and determine the required core dimensions. The optimized design will subsequently be fabricated using additive manufacturing techniques and evaluated through experimental testing.

Completion Date

2026

Semester

Summer

Committee Chair

Kapat, Jayanta

Degree

Master of Science in Mechanical Engineering (M.S.M.E.)

College

College of Engineering and Computer Science

Department

Mechanical and Aerospace Engineering

Format

PDF

Document Type

Thesis

Language

English

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