Paper ID: 1359

Combustion Characteristics of High Concentration Ammonia/Ethanol Blends Under Varied Boost Pressures in a Spark-Assisted Compression Ignition Engine with a Sub-Chamber  

 

Takanobu Okada1, Mitsuhisa Ichiyanagi2, Emir Yilmaz2, Rizal Mahmud2, Christian Dennis Marcelo1, Ferdinand Ronaldo Tjiotijono1, Evan Widjaja3, Jason Sutedjo3, Gabriel Jeremy Gotama4, Willyanto Anggono3,4,*, & Takashi Suzuki2

1Graduate School of Science and Technology, Sophia University, Tokyo 102-8554, Japan

2Department of Engineering and Applied Sciences, Faculty of Science and Technology, Sophia University, Tokyo 102-8554, Japan

3Mechanical Engineering Department, Petra Christian University, Surabaya 60236, Indonesia

4Centre for Sustainable Energy Studies, Petra Christian University, Surabaya 60236, Indonesia

 

*Corresponding author: willy@petra.ac.id

 

Abstract

Ammonia (NH3) has been proposed as a carbon-free alternative to replace fossil fuels and reduce carbon dioxide (CO2) emissions. Ammonia can be transported more easily than hydrogen and has a higher volumetric energy density. However, direct combustion of ammonia is difficult because of its slow-burning nature and high ignition temperature. To address this problem, ammonia can be co-fired with more reactive fuels such as ethanol, which is considered a promising ammonia enhancer due to its carbon-neutral origin and low carbon content. To explore their combustion potential, in this study, we employed a customized engine with a sub-chamber and compression ratio of 17.7, where the effects of ammonia energy ratios (50 and 60%) and boost pressures (0, 5, 10, and 15 kPa) were examined at a constant engine speed of 1000 rpm and excess air ratio of 1.2. The novelty of this study lies in investigating the potential of ammonia/ethanol combustion using a spark-assisted compression ignition (SACI) engine with a sub-chamber, focusing on the unexplored combined effects of boost pressures and ammonia energy ratios. The findings suggest that a higher boost pressure reduced the thermal efficiency, leading to a decrease in the engine indicated mean effective pressure (IMEP). Accordingly, this resulted in a lower in-cylinder pressure and heat release rate, which slowed down the combustion process. This unusual behavior can be attributed to an increase in the latent heat of vaporization of ethanol with pressure, which requires more heat energy to achieve fuel vaporization and effectively cool the combustion chamber. The engine performance can be improved by employing lower ammonia energy ratios. However, this comes at the expense of 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 use of ammonia/ethanol in combustion engines. 

Keywords: ammonia; co-combustion; engine performance; ethanol; boost pressure; sub-chamber.

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