Authors

S. Tanno, K. Kaneko, K. Kimura, Y. Miyamoto, J. Miyagawa, Toyota Motor Corporation, Aichi, Japan

Year

2026

Print Info

Production/Publication ÖVK

Summary

Hydrogen can be produced from various renewable energy sources, and hydrogen engines are being considered as one of the options for achieving carbon neutrality (CN). Two main combustion approaches have been proposed to meet NO_x emission regulations: stoichiometric combustion aiming for three-way catalyst purification, and lean combustion to reduce engine-out NOx. In both methods, direct injection during the compression stroke is effective for suppressing abnormal combustion, increasing specific output and improving efficiency. However, the mixture becomes inhomogeneous because of a shorter mixing time, and it leads to challenges such as higher exhaust temperatures due to post-combustion of unburned hydrogen in stoichiometric combustion, and increased NO_x emissions in lean combustion. 

When considering the process of a hydrogen jet mixing compared to a conventional liquidfuel spray, a gas jet has not only a shorter mixing time but also inherent difficulty entraining air inside it. Although hydrogen is known for its high molecular diffusivity, in-cylinder turbulent diffusion is two or three orders of magnitude stronger. Therefore, utilizing turbulent diffusion is essential for gas jet mixing. In this study, a gas jet simulation method validated through optical measurement was developed and a systematic investigation using this method was conducted. Based on these analyses, guidelines for achieving well-mixed mixture formation in a hydrogen direct injection engine have been derived.

ISBN

978-3-9504969-5-6

DOI

https://doi.org/10.62626/ozpx-dprq Copy link

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