Session: 01-11 Electrified Propulsion and Novel Cycles I

Paper Number: 154219

Performance of an Ammonia Turbofan With the Inclusion of an Optimized Bleed Air Heat Exchanger 

With the increasing need for decarbonization in aviation, Ammonia has emerged as a promising fuel source due to its well-established production methods, defined transportation infrastructure, and higher volumetric energy density compared to pure liquid hydrogen. However, the combustion of ammonia presents challenges, primarily due to its slow chemical kinetics and low flame speeds. These issues can be mitigated by introducing a small amount of Hydrogen as a promoter, which necessitates the partial cracking of ammonia during flight.

To achieve this cracking, heat is required, which will be supplied by the Cooling Air extracted from the last stage of the High-Pressure Compressor. A tube bank heat exchanger is optimized using an entropy-based objective function, demonstrating promise compared to traditional energy-based approaches. The performance of the ammonia-powered turbofan is analyzed through the integration of the heat exchanger, utilizing the TMATS library in conjunction with Cantera in SIMULINK.

This study specifically investigates how supplying heat from the Cooling Air to the ammonia impacts the required turbine cooling flow and, consequently, the overall performance of the engine core. Key performance metrics, such as thrust specific fuel consumption and various turbofan efficiencies (including core efficiency and thermal efficiency), are compared across three scenarios: a typical kerosene-powered engine, an ammonia-powered engine, and an ammonia-powered engine employing Cooled Cooling Air.

Preliminary heat transfer calculations suggest that the Cooled Cooling Air lacks sufficient energy to bring ammonia to cracking conditions. To address this, a catalyst-dependent method is proposed, which involves splitting ammonia into two streams—one to be cracked and the other to bypass the heat exchanger. This approach aims to adjust the required cracking efficiency to achieve the desired fuel blend while minimizing additional cracking heat requirements. For this study, a Ru-K/CaO catalyst for high-pressure ammonia decomposition is considered.

Presenting Author: Marcel Otto Center for Advanced Turbomachinery and Energy Research

Presenting Author Biography: Assistant Professor at UCF and manager of the NASA funded University Leadership Initiative program aiming to decarbonize aviation through the investigation of Ammonia as a Hydrogen carrier.

Authors:

Lucas Cavalcante Center for Advanced Turbomachinery and Energy Research
Marcel Otto Center for Advanced Turbomachinery and Energy Research
Jayanta Kapat Center for Advanced Turbomachinery and Energy Research