Ammonia thermal atmosphere compression ignition engine: Stable combustion mechanism and intake control strategy

Abstract

Ammonia is a promising carbon-free fuel for internal combustion engines (ICEs). However, existing research has not yet provided satisfactory solutions for ammonia combustion, a crucial gap that significantly limits its practical application. In this study, ammonia thermal atmosphere compression ignition (TACI) combustion mode was proposed as a promising solution to achieve efficient and clean ammonia diffusion combustion in ICEs. This study investigates the stable combustion mechanism of ammonia spray, the formation characteristics of nitrogen oxides, and the greenhouse gas (GHG) reduction potential of the ammonia TACI combustion mode. Experimental results of the TACI mode demonstrate high thermal efficiency, low NO_x emissions, ultra-low N₂O emissions, and negligible unburned ammonia slip. Intake control strategies, including intake pressure and intake temperature, are explored to further improve the ammonia substitution ratio (ASR) and GHG reduction performance. Intake air heating significantly improves the ASR, but must be coupled with high intake pressure to ensure sufficient oxygen supply. The combined strategy of intake air heating and high intake pressure increases the ASR by 17% and the GHG reduction ratio by 9%. Under medium-load conditions, this approach achieves an ASR over 80% and GHG reduction exceeding 70%, meeting the International Maritime Organization (IMO) 2040 GHG reduction target.

Graphical abstract

Keywords

thermal atmosphere compression ignition / ammonia diffusion combustion / intake control strategy / carbon reduction / internal combustion engine

References

[1] Ammonia Energy Association (AEA) . Australia conference: Ammonia = Hydrogen 2.0. , 2019,

[2] Iowa Energy Center . Ammonia — the key to US energy independence. , 2006,

[3] U.S. Department of Energy . Potential roles of ammonia in a hydrogen economy. , 2006,

[4] Japan Science , Technology Agency (JST) . SIP energy carriers. , 2016,

[5] Japan Science , Technology Agency (JST) . The green ammonia consortium founding assembly. , 2017,

[6] Hou F , Liu Y , Ma Z . et al. Study of the carbon neutral path in China: A literature review. Chinese Journal of Urban and Environmental Studies, 2023, 11(2): 21–43

[7] Child M , Bogdanov D , Breyer C . The role of storage technologies for the transition to a 100% renewable energy system in Europe. Energy Procedia, 2018, 155: 44–60

[8] Giddey S , Badwal S P S , Munnings C . et al. Ammonia as a renewable energy transportation media. ACS Sustainable Chemistry & Engineering, 2017, 5(11): 10231–10239

[9] International Energy Agency (IEA) . Net zero by 2050: A roadmap for the global energy sector. , 2021,

[10] Jonasson E , Fjellstedt C , Temiz I . Grid impact of co-located offshore renewable energy sources. Renewable Energy, 2024, 230: 120784

[11] Xu T , Gao W , Qian F . et al. The implementation limitation of variable renewable energies and its impacts on the public power grid. Energy, 2022, 239: 121992

[12] de Oliveira I A , Schaeffer R , Szklo A . The impact of energy storage in power systems: The case of Brazil’s Northeastern grid. Energy, 2017, 122: 50–61

[13] Jafari M , Botterud A , Sakti A . Decarbonizing power systems: A critical review of the role of energy storage. Renewable & Sustainable Energy Reviews, 2022, 158: 112077

[14] Yan J , Liu S , Yan Y . et al. How to choose mobile energy storage or fixed energy storage in high proportion renewable energy scenarios: Evidence in China. Applied Energy, 2024, 376: 124274

[15] Elalfy D A , Gouda E , Kotb M F . et al. Comprehensive review of energy storage systems technologies, objectives, challenges, and future trends. Energy Strategy Reviews, 2024, 54: 101482

[16] Hren R , Vujanović A , Van Fan Y . et al. Hydrogen production, storage and transport for renewable energy and chemicals: An environmental footprint assessment. Renewable & Sustainable Energy Reviews, 2023, 173: 113113

[17] International Energy Agency (IEA) . World energy outlook. , 2025,

[18] Sun Z , Liu F S , Liu X . et al. Research and development of hydrogen fueled engines in China. International Journal of Hydrogen Energy, 2012, 37(1): 664–681

[19] Valera-Medina A , Xiao H , Owen-Jones M . et al. Ammonia for power. Progress in energy and combustion science, 2018, 69: 63–102

[20] International Maritime Organization (IMO) . Marine environment protection committee (MEPC 80). , 2023,

[21] Elçiçek H . Bibliometric analysis on hydrogen and ammonia: A comparative evaluation for achieving IMO’s decarbonization targets. International Journal of Environmental Science and Technology, 2024, 21(10): 7039–7060

[22] Zhou X , Li T , Chen R . et al. Ammonia marine engine design for enhanced efficiency and reduced greenhouse gas emissions. Nature Communications, 2024, 15(1): 2110

[23] Cornelius W , Huellmantel L W , Mitchell H R . Ammonia as an engine fuel. SAE Transactions, 1965, 74: 300–326

[24] Starkman E S , James G E . , Newhall H K. Ammonia as a spark ignition engine fuel: Theory and Application. SAE Transactions, 1966, 75: 765–784

[25] Yang R , Tang Q , Cheng H . et al. Experimental study on the spray characteristics of high-pressure liquid ammonia under different ambient conditions. Journal of the Energy Institute, 2024, 117: 101771

[26] Dimitriou P , Javaid R . A review of ammonia as a compression ignition engine fuel. International Journal of Hydrogen Energy, 2020, 45(11): 7098–7118

[27] Liu R , Ting D S-K , Checkel M D . Ammonia as a fuel for SI engine. SAE Technical Paper 2003-01-3095, 2003,

[28] Chiong M C , Chong C T , Ng J H . et al. Advancements of combustion technologies in the ammonia-fuelled engines. Energy Conversion and Management, 2021, 244: 114460

[29] Kobayashi H , Hayakawa A , Somarathne K D K A . et al. Science and technology of ammonia combustion. Proceedings of the Combustion Institute, 2019, 37(1): 109–133

[30] Yu Z , Yang R , Yue Z . et al. Investigating the impacts of charge composition and temperature on ammonia/hydrogen combustion in a heavy-duty spark-ignition engine. International Journal of Hydrogen Energy, 2024, 95: 31–42

[31] Wang B , Yang C , Wang H . et al. Study on injection strategy of ammonia/hydrogen dual fuel engine under different compression ratios. Fuel, 2023, 334: 126666

[32] Wang Y , Zhou X , Liu L . Theoretical investigation of the combustion performance of ammonia/hydrogen mixtures on a marine diesel engine. International Journal of Hydrogen Energy, 2021, 46(27): 14805–14812

[33] Lhuillier C , Brequigny P , Contino F . et al. Experimental study on ammonia/hydrogen/air combustion in spark ignition engine conditions. Fuel, 2020, 269: 117448

[34] Kurien C , Mittal M . Review on the production and utilization of green ammonia as an alternate fuel in dual-fuel compression ignition engines. Energy Conversion and Management, 2022, 251: 114990

[35] Zhang S , Yang R , Tang Q . et al. Combustion and emission characteristics of an ammonia–diesel dual-fuel engine under high ammonia substitution ratios. Energy & Fuels, 2025, 39(13): 6559–6571

[36] Nadimi E , Przybyła G , Lewandowski M T . et al. Effects of ammonia on combustion, emissions, and performance of the ammonia/diesel dual-fuel compression ignition engine. Journal of the Energy Institute, 2023, 107: 101158

[37] Yousefi A , Guo H , Dev S . et al. Effects of ammonia energy fraction and diesel injection timing on combustion and emissions of an ammonia/diesel dual-fuel engine. Fuel, 2022, 314: 122723

[38] Yang R , Yu Z , Yue Z . et al. Effect of fuel injection spatial and temporal arrangement on high-pressure direct-injection ammonia/diesel dual-fuel combustion. Fuel, 2025, 387: 134409

[39] Zhang Z , Long W , Dong P . et al. Performance characteristics of a two-stroke low speed engine applying ammonia/diesel dual direct injection strategy. Fuel, 2023, 332: 126086

[40] Bjørgen K O P , Emberson D R , Løvås T . Combustion of liquid ammonia and diesel in a compression ignition engine operated in high-pressure dual fuel mode. Fuel, 2024, 360: 130269

[41] Dong P , Liu K , Zhang L . et al. Study on the synergistic control of nitrogenous emissions and greenhouse gas of ammonia/diesel dual direct injection two-stroke engine. Energy, 2024, 307: 132657

[42] Zhang S , Tang Q , Liu H . et al. Numerical investigation and optimization of the ammonia/diesel dual fuel engine combustion under high ammonia substitution ratio. Journal of the Energy Institute, 2024, 117: 101797

[43] Zhou X , Li T , Wang N . et al. Pilot diesel-ignited ammonia dual fuel low-speed marine engines: A comparative analysis of ammonia premixed and high-pressure spray combustion modes with CFD simulation. Renewable & Sustainable Energy Reviews, 2023, 173: 113108

[44] Li T , Zhou X , Wang N . et al. A comparison between low- and high-pressure injection dual-fuel modes of diesel-pilot-ignition ammonia combustion engines. Journal of the Energy Institute, 2022, 102: 362–373

[45] Yang R , Yue Z , Zhang S . et al. A novel approach of in-cylinder NO_x control by inner selective non-catalytic reduction effect for high-pressure direct-injection ammonia engine. Fuel, 2025, 381: 133349

[46] Mi S , Zhang J , Shi Z . et al. Optimization of direct-injection ammonia-diesel dual-fuel combustion under low load and higher ammonia energy ratios. Fuel, 2024, 375: 132611

[47] Wang Q , Long W , Sun H . et al. A comparative study of premixed and diffusion combustion strategies in a high-speed ammonia/diesel dual-direct-injection engine. Energy, 2025, 334: 137630

[48] Yang R , Yue Z , Zhang S . et al. Ammonia thermal atmosphere compression ignition combustion mode to achieve efficient combustion and low greenhouse gas emissions. Energy Conversion and Management, 2025, 325: 119427

[49] Yang R , Liu H , Li B . et al. Experimental and numerical investigation on the superheated and subcooled ammonia spray characteristics under high injection pressure. Fuel, 2025, 387: 134320

[50] Yang R , Liu H , Zhang S . et al. Optical and numerical study on high-pressure liquid ammonia spray atomization and ignition characteristics under different injector nozzle diameters. Energy Conversion and Management, 2025, 333: 119781

[51] European Union . Regulation (EU) 2024/1257 of the European parliament and of the council. , 2024,

[52] Wolfram P , Kyle P , Zhang X . et al. Using ammonia as a shipping fuel could disturb the nitrogen cycle. Nature Energy, 2022, 7(12): 1112–1114

[53] Yao M , Zheng Z , Liu H . Progress and recent trends in homogeneous charge compression ignition (HCCI) engines. Progress in Energy and Combustion Science, 2009, 35(5): 398–437

RIGHTS & PERMISSIONS

Higher Education Press