Evaluation of ammonia-gasoline co-combustion in a modern spark ignition research engine

Ambalakatte, A.; Geng, S.; Cairns, A.; Harrington, A.; Hall, J.; Bassett, M.

Abstract

Ammonia (NH3) is emerging as a potential favoured fuel for longer range decarbonised heavy transport, particularly in the marine sector, predominantly due to highly favourable characteristics as an effective hydrogen carrier. This is despite generally unfavourable combustion and toxicity attributes, restricting end use to applications where robust health and safety protocols can always be upheld. In the currently reported work, a spark ignited thermodynamic single cylinder research engine equipped with gasoline direct injection was upgraded to include gaseous ammonia port injection fuelling, with the aim of understanding maximum viable ammonia substitution ratios across the speed-load operating map. The work was conducted at varied effective compression ratios under overall stoichiometric conditions, with the spark timing re-optimised for maximum brake torque at all stable logged sites. The experiments included industry standard measurements of combustion, performance, and engine-out emissions (including NH3 “slip”). With a geometric compression ratio of 11.2:1, it was found possible to run the engine on pure ammonia at low engine speeds (1000-1800rpm) and loads of 12bar net IMEP. When progressively dropping down below this load limit an increasing amount of gasoline co-firing was required to avoid engine misfire. When operating at 1800rpm and 12bar net IMEP, all emissions of carbon (CO2, CO, unburned hydrocarbons) and NOx decreased considerably when switching to higher NH3 substitution ratios, with NOx reduced by ~ 45% at 1800rpm/12bar when switching from pure gasoline to pure NH3 (associated with longer and cooler combustion). By further increasing the geometric compression ratio to 12.4 and reducing the intake camshaft duration for maximum effective compression ratio, it was possible to operate the engine on pure ammonia at much lower loads in a fully warmed up state (e.g., linear low load limit line from 1000rpm/6bar net IMEP to 1800rpm/9bar net IMEP). Under all conditions, the indicated thermal efficiency of the engine was either equivalent to or slightly higher than that obtained using gasoline-only due to the favourable anti-knock rating of NH3. Ongoing work is concerned with detailed breakdown of individual NOx species together with measuring the impact of hydrogen enrichment across the operating map.

Citation

Ambalakatte, A., Geng, S., Cairns, A., Harrington, A., Hall, J., & Bassett, M. (2023). Evaluation of ammonia-gasoline co-combustion in a modern spark ignition research engine. Carbon Neutrality, 2(1), Article 35. https://doi.org/10.1007/s43979-023-00075-3

• Journal Article Type: Article
• Acceptance Date: Nov 27, 2023
• Online Publication Date: Dec 20, 2023
• Publication Date: Dec 20, 2023
• Deposit Date: Jan 4, 2024
• Publicly Available Date: Jan 9, 2024
• Journal: Carbon Neutrality
• Print ISSN: 2788-8614
• Electronic ISSN: 2731-3948
• Publisher: Springer
• Peer Reviewed: Not Peer Reviewed
• Volume: 2
• Issue: 1
• Article Number: 35
• DOI: https://doi.org/10.1007/s43979-023-00075-3
• Keywords: Economics, Econometrics and Finance (miscellaneous); Energy (miscellaneous); Environmental Science (miscellaneous)
• Public URL: https://nottingham-repository.worktribe.com/output/28716096
• Publisher URL: https://link.springer.com/article/10.1007/s43979-023-00075-3
• Additional Information: Received: 31 July 2023; Revised: 30 October 2023; Accepted: 27 November 2023; First Online: 20 December 2023; : ; : Not applicable.; : The authors declare that they have no competing interests.