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Understanding the difference in combustion and flame propagation characteristics between ammonia and methane using an optical SI engine

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journal contribution
posted on 2022-06-21, 09:33 authored by Ren Zhang, Lin Chen, Haiqiao Wei, Jinguang Li, Rui Chen, Jiaying Pan

As a carbon-free hydrogen-carrier fuel with a high content of hydrogen, ammonia (NH3) exhibits unfavorable combustion properties such as low flammability and large cyclic variations, requiring further investigation in actual engines. In this work, for the first time, using a single-cylinder optical spark ignition (SI) engine with a high compression ratio, engine performance as well as combustion and flame propagation characteristics were investigated. Synchronization measurement of in-cylinder pressure and high-speed photography was performed, and the combustion characteristics were compared between ammonia and methane under the same operating conditions. The results show that the combustion stability and power capability of ammonia are significantly lower than that of methane. Further analysis combining combustion phasing and flame propagation characteristics indicates that the burning time loss mainly comes from the initial flame development process rather than the main combustion duration which results in a deficit in engine performance. The average probability maps of the flame location indicate that the flame front propagation of the two fuels emerges with obviously different characteristics. Quantitative flame solving shows that NH3 flame propagation features a higher flame stretch sensitivity which is macroscopically reflected in the cyclic variations. Furthermore, the quantification of flame response to turbulence was solved and observed much higher effects for NH3 flame than methane, which indicates NH3 flame propagation is mainly driven by the flame response to turbulence while the flame propagation of methane exhibits higher sensitivity to temperature than ammonia. The current study shall provide insights into the application of ammonia in the internal combustion engine.

Funding

National Natural Science Foundation of China (52076149, 51825603)

Educational Commission of Hubei Province of China (Q20211509)

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Aeronautical and Automotive Engineering

Published in

Fuel

Volume

324

Issue

Part C

Publisher

Elsevier

Version

  • AM (Accepted Manuscript)

Rights holder

© Elsevier

Publisher statement

This paper was accepted for publication in the journal Fuel and the definitive published version is available at https://doi.org/10.1016/j.fuel.2022.124794

Acceptance date

2022-06-03

Publication date

2022-06-09

Copyright date

2022

ISSN

0016-2361

Language

  • en

Depositor

Prof Rui Chen. Deposit date: 17 June 2022

Article number

124794

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