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Investigation on end-gas auto-ignition and knock characteristics of iso-octane over wide thermodynamic conditions under jet ignition using a rapid compression machine

Liu, Wei and Qi, Yunliang and Zhang, Ridong and Zhang, Qihang and Wang, Zhi (2022) Investigation on end-gas auto-ignition and knock characteristics of iso-octane over wide thermodynamic conditions under jet ignition using a rapid compression machine. Fuel, 313 . Art. No. 122665. ISSN 0016-2361. doi:10.1016/j.fuel.2021.122665. https://resolver.caltech.edu/CaltechAUTHORS:20211209-456383000

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Abstract

Jet ignition (JI) is increasingly considered a promising way to increase engine thermal efficiency due to its faster burning velocity than conventional spark ignition (SI). However, as an ignition method, JI does not change the nature of premixed combustion, and knock can still occur. This study investigated knock characteristics and end-gas auto-ignition behaviors of the stoichiometric iso-octane-air mixture under JI at an initial temperature ranging from 650 to 830 K and an initial pressure ranging from 10 to 20 bar. Experiments under SI were also conducted for comparison. The results showed that compared with SI, JI could reduce both combustion duration and knock intensity. The combustion mode of the end-gas transitioned from non-auto-ignition to mild auto-ignition and eventually to detonation as the initial pressure increased, which was similar to the situation under SI. Thermodynamic analysis indicated that compared with SI, the auto-ignition under JI tended to occur at higher thermodynamic states due to less heat loss, which led to higher burned mass fractions at the instant of auto-ignition. Further analysis using Bradley’s ε-ξ diagram showed that, under low initial temperatures, the initial pressure had little impact on ε but could change ξ significantly, and the auto-ignition mode mainly depends on ξ rather than ε as the pressure changed. The effect of initial pressure on ε and ξ became inversed under high initial temperatures. Finally, the auto-ignition regime was analyzed using the Da_t-Re_t diagram. The result showed that the auto-ignition cases were all in the Mixed/DDT region, and the detonation cases were all in the strong ignition region.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.fuel.2021.122665DOIArticle
ORCID:
AuthorORCID
Qi, Yunliang0000-0003-4718-5025
Wang, Zhi0000-0001-5932-9124
Additional Information:© 2021 Elsevier Ltd. Received 27 September 2021, Revised 16 November 2021, Accepted 18 November 2021, Available online 9 December 2021. This study was supported by the National Natural Science Foundation of China (Grant No.: 52076118). The authors would like to thank Prof. Rémy Mével from the Center for Combustion and Energy at Tsinghua University for his help in chemical analysis and Dr. Erin Burkett from the Hixon Writing Center at California Institute of Technology for the feedback on the writing.
Group:GALCIT
Funders:
Funding AgencyGrant Number
National Natural Science Foundation of China52076118
Subject Keywords:Jet ignition; Auto-ignition; Knock characteristic; Ignition regime
DOI:10.1016/j.fuel.2021.122665
Record Number:CaltechAUTHORS:20211209-456383000
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20211209-456383000
Official Citation:Wei Liu, Yunliang Qi, Ridong Zhang, Qihang Zhang, Zhi Wang, Investigation on end-gas auto-ignition and knock characteristics of iso-octane over wide thermodynamic conditions under jet ignition using a rapid compression machine, Fuel, Volume 313, 2022, 122665, ISSN 0016-2361, https://doi.org/10.1016/j.fuel.2021.122665. (https://www.sciencedirect.com/science/article/pii/S001623612102531X)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112323
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:10 Dec 2021 23:08
Last Modified:01 Feb 2022 17:41

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