Auto-ignited kernels during knocking combustion in a spark-ignition engine

Nobuyuki Kawahara, Eiji Tomita, Yoshitomo Sakata

Research output: Contribution to journalArticle

79 Citations (Scopus)

Abstract

In this study, auto-ignition of end-gas due to flame propagation and intensity oscillations caused by Shockwaves that occur during knocking combustion were visualized in a compression-expansion engine using a high-speed video camera. Chemical luminescence emissions of the end-gas were detected to analyze the chemical reactions caused by the auto-ignition. Four main conclusions were drawn from this study. When the end-gas region was compressed due to the propagating flame front, auto-ignited kernels appeared near a negative curvature of the flame front. This negative curvature was related to low-temperature chemistry. The large amount of unburned mixture generated a strong pressure wave caused by the auto-ignited kernels explosion. Visualized images of a regular propagating flame front and auto-ignited kernels confirmed that the knocking intensity had a strong relationship with the mass fraction of the unburned mixture. Oscillations of OH* radicals were synchronized with the in-cylinder pressure oscillations, which were produced due to the resulting Shockwave. Before auto-ignition of the end-gas occurred, weak OH* radicals and very weak HCHO* radicals appeared in the end-gas region due to low-temperature chemistry. The OH* radicals played an important role in the low-temperature kinetic reactions. This confirms low-temperature chemical reaction of auto-ignited kernel in the end gas region. OH* radicals are a good indicator of the transition from low-temperature chemistry to high-temperature auto-ignition.

Original languageEnglish
Pages (from-to)2999-3006
Number of pages8
JournalProceedings of the Combustion Institute
Volume31 II
DOIs
Publication statusPublished - 2007

Fingerprint

spark ignition
Internal combustion engines
engines
spontaneous combustion
Gases
flame propagation
Ignition
gases
chemistry
Temperature
Chemical reactions
chemical reactions
curvature
pressure oscillations
oscillations
High speed cameras
Video cameras
Engine cylinders
elastic waves
Reaction kinetics

Keywords

  • Auto-ignited kernels
  • Engine knock
  • Low-temperature chemistry
  • Pressure wave formation in knocking combustion
  • Spark-ignition engine

ASJC Scopus subject areas

  • Automotive Engineering

Cite this

Auto-ignited kernels during knocking combustion in a spark-ignition engine. / Kawahara, Nobuyuki; Tomita, Eiji; Sakata, Yoshitomo.

In: Proceedings of the Combustion Institute, Vol. 31 II, 2007, p. 2999-3006.

Research output: Contribution to journalArticle

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