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Investigation into ethanol effects on combustion and particle number emissions in a spark-ignition to compression-ignition (SICI) engine

Fan, Qinhao and Liu, Shang and Qi, Yunliang and Cai, Kaiyuan and Wang, Zhi (2021) Investigation into ethanol effects on combustion and particle number emissions in a spark-ignition to compression-ignition (SICI) engine. Energy, 233 . Art. No. 121170. ISSN 0360-5442. doi:10.1016/j.energy.2021.121170. https://resolver.caltech.edu/CaltechAUTHORS:20210610-093756728

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Abstract

Spark assistance along with oxygenated components addition is a promising method to achieve stable compression ignition, high thermal efficiency and low particle emission. To this end, ethanol blended with non-oxygenated gasoline was fueled to an engine working with spark-ignition to compression-ignition (SICI) mode under air dilution and exhaust-diluted conditions. The effects of ethanol addition on engine performance including combustion characteristics, fuel economy, particle number (PN) emissions, were studied in two categories: changing research octane number (RON) by varying ethanol content and maintaining RON by changing fuel type. The results showed that ethanol addition by splash blending suppressed knock tendency, and the knock intensity could be lowered by up to 65–75% with increasing ethanol content. However, when maintaining the same RON, the ethanol-gasoline blend exhibited higher knock intensity than pure gasoline due to synergistic effects between ethanol and aromatics on auto-ignition. Compared to pure spark ignition with high-RON gasolines, using ethanol-gasoline blends under SICI could reduce the minimum fuel consumption rate by up to 25 g/(kW·h). To characterize the high-efficiency cycles under SICI, two dimensionless parameters were proposed by considering the ratios of heat release amount and duration between the flame propagation stage and auto-ignition stage. The two parameters showed good exponential correlation. As for emissions, blending ethanol could basically reduce PN emissions under SICI mode except for the cases with significant increase in nucleation particles, such as those with high knock intensity under stoichiometric condition and poor combustion quality under heavily exhaust-diluted conditions. The total PN reduction by blending ethanol is mainly due to the decrease of accumulation mode particles, during the stage of flame propagation rather than auto-ignition. Blending ethanol into non-oxygenated gasoline will directly increase unburned hydrocarbons and nitrogen oxides due to the low auto-ignition propensity of ethanol under stoichiometric or moderately lean conditions according to the temperature-pressure trajectory. Therefore, a dedicated combustion system with higher compression ratio and lean-boosted mixture is required to enhance ethanol's reactivity and achieve better fuel economy along with low PN emission for diluted SICI combustion.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.energy.2021.121170DOIArticle
ORCID:
AuthorORCID
Fan, Qinhao0000-0001-6127-3852
Additional Information:© 2021 Elsevier Ltd. Received 1 February 2021, Revised 22 May 2021, Accepted 2 June 2021, Available online 8 June 2021. This work was supported by the National Key Research and Development Program of China (Grant No. 2017YFE0102800) and the National Natural Science Foundation of China (Grant No. 52076118). The assistance of Dr. Haoye Liu at the University of Birmingham in paper writing and language improvement was also gratefully acknowledged. Credit author statement: Qinhao Fan: Conceptualization, Methodology, Investigation, Data curation, Writing – original draft. Shang Liu: Investigation, Formal analysis. Yunliang Qi: Methodology, Writing – review & editing, Project administration. Kaiyuan Cai: Investigation, Resources. Zhi Wang: Supervision, Project administration, Funding acquisition. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Group:GALCIT
Funders:
Funding AgencyGrant Number
National Key Research and Development Program of China2017YFE0102800
National Natural Science Foundation of China52076118
Subject Keywords:Spark-ignition to compression-ignition; Ethanol blends; Fuel economy; Particle number emission; Fuel reactivity
DOI:10.1016/j.energy.2021.121170
Record Number:CaltechAUTHORS:20210610-093756728
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20210610-093756728
Official Citation:Qinhao Fan, Shang Liu, Yunliang Qi, Kaiyuan Cai, Zhi Wang, Investigation into ethanol effects on combustion and particle number emissions in a spark-ignition to compression-ignition (SICI) engine, Energy, Volume 233, 2021, 121170, ISSN 0360-5442, https://doi.org/10.1016/j.energy.2021.121170. (https://www.sciencedirect.com/science/article/pii/S0360544221014183)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109464
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:10 Jun 2021 16:53
Last Modified:02 Jul 2021 20:03

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