Experimental study on thermal efficiency and emission characteristics of a lean burn hydrogen enriched natural gas engine

In order to analyze the effect of hydrogen addition on natural gas (NG) engine's thermal efficiency and emission, an experimental research was conducted on a spark ignition NG engine using variable composition hydrogen/CNG mixtures (HCNG). The results showed that hydrogen enrichment could signi...

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Bibliographic Details
Published in:	International journal of hydrogen energy 2007-12, Vol.32 (18), p.5067-5075
Main Authors:	Ma, Fanhua, Wang, Yu, Liu, Haiquan, Li, Yong, Wang, Junjun, Zhao, Shuli
Format:	Article
Language:	eng
Subjects:	Applied sciences Emission Energy Energy. Thermal use of fuels Engines and turbines Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc Exact sciences and technology Hydrogen enrichment natural gas Indicated thermal efficiency Lean burn Lean operation limit
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Summary:	In order to analyze the effect of hydrogen addition on natural gas (NG) engine's thermal efficiency and emission, an experimental research was conducted on a spark ignition NG engine using variable composition hydrogen/CNG mixtures (HCNG). The results showed that hydrogen enrichment could significantly extend the lean operation limit, improve the engine's lean burn ability, and decrease burn duration. However, nitrogen oxides ( NO x ) were found to increase with hydrogen addition if spark timing was not optimized according to hydrogen's high burn speed. Also found when spark timing was set at constant was that hydrogen addition actually increases heat transfer out of the cylinder due to smaller quenching distance and higher combustion temperature, thus is not good to improve thermal efficiency if combined with the effect of non-ideal spark timing. But if spark timing was retarded to MBT, taking advantage of hydrogen's high burn speed, NO x emissions exhibited no obvious increase after hydrogen addition and engine thermal efficiency increased with the increase of hydrogen fraction. Unburned hydrocarbon always decreased with the increase of hydrogen fraction.
ISSN:	0360-3199 1879-3487