On the Z-shaped explosion limits of acetylene-oxygen mixtures

Jianhang Li, Wenkai Liang, Wenhu Han, Chung K. Law

Research output: Contribution to journalArticlepeer-review

Abstract

The explosion limits of the acetylene-oxygen (C2H2-O2) mixture have been investigated and it is demonstrated, for the first time, that the C2H2-O2 explosion exhibits a Z-shaped response in the pressure-temperature regime with three distinct limits from low to high pressures, which resembles the explosion limits of hydrogen-oxygen (H2-O2) mixtures. Kinetic analysis shows that the first limit is mainly controlled by the reaction of C2H2 (+ M) = H2CC (+ M) and the subsequent pathways of H2CC→HCO→H. The second and third limits are controlled by the H-addition reaction of C2H2 to form the C2H3 radical. The C2H3 radical is less reactive at intermediate pressures, and its pressure dependent formation, C2H2 + H (+ M) = C2H3 (+ M), results in the second limit. However, C2H3 radical is reactivated at high pressures through C2H2 + HO2 = C2H3 + O2, from which the HO2 radical formed activates the HO2→H2O2→OH chain branching channel, leading to the third limit. Further, we explored the explosion limits of the H2-C2H2-O2 mixtures, which shows that with increasing H2 concentrations, the explosion limit curve rotates clockwise around a turnover point. Such rotation only occurs in the second and third limits, while the first limit basically coincides with that of the C2H2-O2 system. The kinetic reasons responsible for the observed behavior are identified through the competing pathways of H2 and C2H2. Furthermore, the effects of changing of equivalent ratio, dilutions of nitrogen and water, with and without surface reactions on the explosion limits are also discussed. The results of the present work are useful to better understand the explosion limits of C2H2-O2 and H2-C2H2-O2mixtures and further study of more complex hydrocarbon fuels.

Original languageEnglish (US)
Article number105300
JournalProceedings of the Combustion Institute
Volume40
Issue number1-4
DOIs
StatePublished - Jan 2024
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Chemical Engineering
  • Mechanical Engineering
  • Physical and Theoretical Chemistry

Keywords

  • Acetylene-oxygen
  • Explosion limits
  • Hydrogen

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