Combustion Characteristics of High Concentration Ammonia/Ethanol Blends under Varied Boost Pressures in a Spark-assisted Compression Ignition Engine with a Sub-chamber

https://doi.org/10.5614/j.eng.technol.sci.2026.58.6.1

Authors

  • Takanobu Okada Graduate School of Science and Technology, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 https://orcid.org/0009-0000-7050-6734
  • Mitsuhisa Ichiyanagi Department of Engineering and Applied Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 https://orcid.org/0000-0001-6021-3719
  • Emir Yilmaz Department of Engineering and Applied Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554
  • Rizal Mahmud Department of Engineering and Applied Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554
  • Christian Dennis Marcelo Graduate School of Science and Technology, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 https://orcid.org/0009-0005-5219-2555
  • Ferdinand Ronaldo Tjiotijono Graduate School of Science and Technology, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554
  • Evan Widjaja Mechanical Engineering Department, Faculty of Industrial Technology, Petra Christian University, Jalan Siwalankerto 121-131, Surabaya 60236,
  • Jason Sutedjo Mechanical Engineering Department, Faculty of Industrial Technology, Petra Christian University, Jalan Siwalankerto 121-131, Surabaya 60236, https://orcid.org/0009-0001-4332-9389
  • Gabriel Jeremy Gotama Mechanical Engineering Department, Faculty of Industrial Technology, Petra Christian University, Jalan Siwalankerto 121-131, Surabaya 60236,
  • Willyanto Anggono Mechanical Engineering Department, Faculty of Industrial Technology, Petra Christian University, Jalan Siwalankerto 121-131, Surabaya 60236, https://orcid.org/0000-0003-4044-7264
  • Takashi Suzuki Department of Engineering and Applied Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554
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Abstract

Ammonia (NH3) is a promising carbon-free fuel that offers higher volumetric energy density and easier transport than hydrogen. However, its direct combustion is limited by its slow burning rates and high ignition temperatures. Co-firing with a more reactive fuel, such as ethanol, can overcome these limitations. In this study, the combustion of ammonia/ethanol blends was evaluated in a customized spark-assisted compression ignition (SACI) engine featuring a sub-chamber and a 17.7 compression ratio. The experimental investigation focused on the interaction between boost pressures (5 to 15 kPa) and ammonia energy ratios (50% and 60%) at 1000 rpm and an excess air ratio of 1.2. The results suggest that increasing boost pressure reduced the thermal efficiency and indicated mean effective pressure (IMEP). Accordingly, this resulted in a lower in-cylinder pressure and heat release rate, which slowed down the combustion process. Such unusual behaviour can be attributed to an increase in the latent heat of vaporization of ethanol with pressure, which requires more heat energy for fuel vaporization and effectively cools the combustion chamber. Furthermore, while adopting lower ammonia energy ratios improved engine performance, it resulted in higher NOx emissions due to the lack of unburned NH3 in the exhaust to undergo the thermal DeNOx process, suggesting the need for careful adjustment of the boost pressure and ammonia energy ratio for the practical application of ammonia/ethanol fuels in combustion engines.

How to Cite

Takanobu Okada, Mitsuhisa Ichiyanagi, Emir Yilmaz, Rizal Mahmud, Christian Dennis Marcelo, Ferdinand Ronaldo Tjiotijono, Evan Widjaja, Jason Sutedjo, Gabriel Jeremy Gotama, Willyanto Anggono, Takashi Suzuki (2026). Combustion Characteristics of High Concentration Ammonia/Ethanol Blends under Varied Boost Pressures in a Spark-assisted Compression Ignition Engine with a Sub-chamber. Journal of Engineering and Technological Sciences, Vol. 58 No. 6 (2026): Vol. 58 No. 6(2026): December (In Progress), 745-761. https://doi.org/10.5614/j.eng.technol.sci.2026.58.6.1

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Date Log

Submitted
November 26, 2025
Accepted
July 22, 2026
Published
September 25, 2026

Keywords

  • ammonia
  • co-combustion
  • engine performance
  • ethanol
  • boost pressure
  • sub-chamber

Issue

Vol. 58 No. 6 (2026): Vol. 58 No. 6(2026): December (In Progress)

Section

Articles

How to Cite

Combustion Characteristics of High Concentration Ammonia/Ethanol Blends under Varied Boost Pressures in a Spark-assisted Compression Ignition Engine with a Sub-chamber. (2026). Journal of Engineering and Technological Sciences, 58(6), 745-761. https://doi.org/10.5614/j.eng.technol.sci.2026.58.6.1

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