Session: 03-02 Ammonia as Fuel and Hydrogen Carrier – Combustion, Storage, and Safety II

Submission Number: 176916

Fuel-Lean Ammonia-Hydrogen Combustion in a Jet-Stirred Reactor: NO and H2O Speciation in RQL Stage 2 Conditions 

The need for more sustainable fuel alternatives in the modern aircraft industry is growing. The acceleration of climate change has catalyzed the search for alternative fuels. Carbon dioxide (CO₂) is 80% of US greenhouse gas emissions. Transportation contributes to 28.5% of those CO₂ emissions, and 10% of transportation CO₂ emissions are due to aviation (U.S. Environmental Protection Agency, 2024). It is imperative that all sectors that use fossil fuels decarbonize. SAF is the current sustainable jet fuel in use but still produces harmful carbon emissions. A promising alternative to SAF is hydrogen, which produces zero carbon emissions.  Hydrogen (H₂) has been identified as a prime fuel candidate for decarbonization (Otto et al., 2022; Valera-Medina et al., 2021). However, with its low liquefaction temperature and high flammability, storage and transportation are complex and costly. Instead, ammonia can be used as a hydrogen carrier, which minimizes both the engineering difficulties and cost of using pure hydrogen (Valera-Medina et al., 2021). Liquid ammonia contains more hydrogen than an equal volume of liquid hydrogen and stays as a liquid at higher temperatures and over a wider range than hydrogen (Otto et al., 2023). By decomposing ammonia (NH₃) into its constituents of N₂ and H₂ using a chemical catalyst, a hydrogen-ammonia fuel mix is created. H₂/NH₃ mixtures still have the desired characteristic of burning without carbon emissions but are less reactive than pure hydrogen. Additionally, ammonia is a widely used compound, so infrastructure already exists for production, transportation, and storage. One drawback of burning ammonia-hydrogen fuels is the combustion byproduct, nitrogen oxide (NOx), and unburned NH₃. These emissions are both poisonous to humans and harmful to the environment.

This work focuses on the measurement of total emissions from an NH₃/H₂ combustor in a rich-burn, quick-quench, lean-burn (RQL) combustor, this paper will focus on the results from the lean-burn stage (Lefebvre et al., 2010). Combustion experiments will be performed in a toroidal jet stirred reactor at atmospheric pressure. A sensor using laser absorption spectroscopy (LAS) is designed and developed to measure combustion byproducts: NO, NH₃, and H₂O, as well as temperature, using two infrared lasers. H₂O will be measured at 1936.21 cm^-1 using fixed-wavelength LAS. NO and H₂O will be measured at 1937.02 cm^-1 and 1937.94 cm^-1 respectively, using scanned-wavelength LAS. NH₃ will be measured at 962.16 cm^-1 using fixed-wavelength LAS. Equivalence ratios will range from 0.4-0.8. Fuel fraction of NH₃/H₂ will range from 0-1. NO, NH₃ and H₂O will be measured at each testing parameter.  This study will look at pure ammonia as well as cracked ammonia as a fuel, which can be simulated with a mixture of ammonia/hydrogen. The results from this research will be used to validate NH₃ chemical kinetic mechanisms for their applicability in fuel lean combustion relevant to RQL stage 2. Experimental results will be compared to model predictions using three different chemical kinetic mechanisms, Glarborg (2023), Zhang et al. (2021), and Stagni et al. (2020). The results presented here will help in the design and development of ammonia combustors operating on RQL configurations.

Presenting Author: Marzuqa Ahmed University of Central Florida

Presenting Author Biography: Marzuqa is a graduate student at the University of Central Florida studying alternative fuels for aviation, with a focus on ammonia.

Authors:

Marzuqa Ahmed University of Central Florida
Amanda Maia University of Central Florida
Guillermo Barrios Cadenas University of Central Florida
Oli Marquez Valenzuela University of Central Florida
Avril Elmer-Santiago University of Central Florida
Ashley Thornton University of Central Florida
Ramees K. Rahman University of Central Florida
Farhan Arafin University of Central Florida
Justin Urso University of Central Florida
Subith Vasu University of Central Florida