University of Hertfordshire

By the same authors


  • Balazs Ihracska
  • Theodosios Korakianitis
  • Paula Ruiz Hincapie
  • David R. Emberson
  • Roy J. Crookes
  • Alvaro Diez
  • Dongsheng Wen
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Original languageEnglish
Pages (from-to)696-710
JournalCombustion and Flame
Early online date12 Aug 2013
Publication statusPublished - 31 Mar 2014


Premixed fuel–air flame propagation is investigated in a single-cylinder, spark-ignited, four-stroke optical test engine using high-speed imaging. Circles and ellipses are fitted onto image projections of visible light emitted by the flames. The images are subsequently analysed to statistically evaluate: flame area;
flame speed; centroid; perimeter; and various flame-shape descriptors. Results are presented for gasoline, isooctane, E85 and M85. The experiments were conducted at stoichiometric conditions for each fuel, at two engine speeds of 1200 rpm (rpm) and 1500 rpm, which are at 40% and 50% of rated engine speed.
Furthermore, different fuel and speed sets were investigated under two compression ratios (CR: 5.00 and 8.14). Statistical tools were used to analyse the large number of data obtained, and it was found that flame speed distribution showed agreement with the normal distribution. Comparison of results assuming spherical and non-isotropic propagation of flames indicate non-isotropic flame propagation should be considered for the description of in-cylinder processes with higher accuracy. The high temporal resolution
of the sequence of images allowed observation of the spark-ignition delay process. The results indicate that gasoline and isooctane have somewhat similar flame propagation behaviour. Additional differences between these fuels and E85 and M85 were also recorded and identified.


This document is the Accepted Manuscript of the following article: Balazs Ihracska, Theodosios Korakianitis, Paula Ruiz, David Robert Emberson, Roy James Crookes, Alvaro Diez, and Dongsheng Wen, ‘Assessment of elliptic flame front propagation characteristics of iso-octane, gasoline, M85 and E85 in an optical engine’, Combustion and Flame, Vol. 161(3): 696-710, March 2014, DOI:, made available under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License CC BY NC-ND 4.0 ( ), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.

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