Session: Technical Posters

Paper Number: 120637

120637 - Turbulent Jet Ignition for Ammonia Engines With an Actively Fueled Pre-Chamber 

Abstract:

Anhydrous ammonia (NH₃) as a fuel has potential to decarbonize internal combustion engines because of its carbon-free nature and its energy dense storage properties under practical temperatures and pressures. However, NH₃ combustion in engines is challenged by its narrow flammability limits, slow flame speed, and high ignition energy [1,2]. Turbulent jet ignition (TJI) may mitigate some of of the NH­₃ combustion challenges while improving efficiency and emissions. TJI refers to igniting a small portion of the combustible mixture in a pre-chamber which is connected to the engine cylinder by several nozzles. Turbulent flames and/or hot combustion gases are ejected into the engine cylinder, igniting the main charge. This strategy has been shown to extend the lean flammability limit of natural gas engines [3] suggesting possibility of extending the lean operating limit of NH₃ in engines to achieve greater thermal efficiency. Additionally, TJI increases turbulent kinetic energy at the flame front leading to a faster turbulent flame speed [4] and deposits more ignition energy at distributed sites throughout the main chamber [5]. This experimental work investigates the performance of a single cylinder engine using an actively fueled pre-chamber, with the injection of either hydrogen (H₂) or NH₃. Injecting H₂ into the pre-chamber enhances the ignitability of the pre-chamber mixture, while injecting NH₃ provides a slightly rich NH₃-air mixture which has been shown to produce on the order of 10% H₂ at engine conditions [6] which is ejected into the engine cylinder to enhance local flame speeds. Pre-chamber pressure rise (which drives the strength of the turbulent jets) is primarily impacted by the pre-chamber equivalence ratio and H₂ fraction (if H₂ is the injected fuel). Results show that the addition of a pre-chamber speeds up the initial burning phase (CA10-Spark Timing), enabling a retarded spark timing for MBT compared to regular spark ignition. Working synergistically, the high compression ratio engine provides additional combustion enhancement in the main chamber through SACI mode, characterized by a dual-peaked heat release rate. Overall, the present work demonstrates that TJI offsets some of the challenges of burning NH₃ and provides insights into the in-cylinder phenomena through indicated engine/pre-chamber performance, heat release rate analysis, and emissions characterization.

References

1. Kobayashi H, Hayakawa A, Somarathne KDK, Okafor EC. Science and Technology of Ammonia Combustion. Proceedings of the Combustion Institute. 2019 November; 37(1): 109-133.

2. Mounaïm Rousselle C, Bréquigny P, Dumand C, Houillé S. Operating Limits for Ammonia Fuel Spark-Ignition Engine. Energies. 2021 July; 14(14).

3. Distaso E, Amirante R, Cassone E, De Palma P, Sementa P, Vaglieco BM. Analysis of the combustion process in a lean-burning turbulent jet ignition engine fueled with methane. Energy Conversion and Management. 2020 November; 223(113257).

4. Silva MR, Houidi MB, Hlaing P, Sanal S, Cenker E, AIRamadan A, et al. The effects of piston shape in a narrow-throat pre-chamber engine. SAE Technical Paper. 2022 August.

5. Gholamisheeri M, Wichman IS, Toulson E. A study of the turbulent jet flow field in a methane fueled turbulent jet ignition (TJI) system. Combustion and Flame. 2017 September; 183: 194-206.

6. Reggeti SA, Kane SP, Northrop WF. Hydrogen Production in Ammonia-Fuelled Spark Ignition Engines. Applications in Energy and Combustion Science. 2023 June; 14(100136).

Presenting Author: Shawn Reggeti University of Minnesota

Presenting Author Biography: Shawn Reggeti is postdoctoral associate at the University of Minnesota performing experimental investigation of ammonia/hydrogen fueled ICE's. He earned his PhD from the University of Alabama where he focused on the study of reacting fuel sprays using optical diagnostics.