An experimental and modeling study of the shock tube ignition of a mixture of n-heptane and n-propylbenzene as a surrogate for a large alkyl benzene

D. Darcy, M. Mehl, J. M. Simmie, J. Würmel, W. K. Metcalfe, C. K. Westbrook, W. J. Pitz, H. J. Curran

Research output: Contribution to journalArticlepeer-review

43 Citations (Scopus)

Abstract

Alkyl aromatics are an important chemical class in gasoline, jet and diesel fuels. In the present work, an n-propylbenzene and n-heptane mixture is studied as a possible surrogate for large alkyl benzenes contained in diesel fuels. To evaluate it as a surrogate, ignition delay times have been measured in a heated high pressure shock tube (HPST) for a mixture of 57% n-propylbenzene/43% n-heptane in air (≈21% O2, ≈79% N2) at equivalence ratios of 0.29, 0.49, 0.98 and 1.95 and compressed pressures of 1, 10 and 30 atm over a temperature range of 1000-1600 K. The effects of reflected-shock pressure and equivalence ratio on ignition delay time were determined and common trends highlighted. A combined n-propylbenzene and n-heptane reaction mechanism was assembled and simulations of the shock tube experiments were carried out. The simulation results showed very good agreement with the experimental data for ignition delay times. Sensitivity and reaction pathway analyses have been performed to reveal the important reactions responsible for fuel oxidation under the shock tube conditions studied. It was found that at 1000 K, the main consumption pathways for n-propylbenzene are abstraction reactions on the alkyl chain, with particular selectivity to the allylic site. In comparison at 1500 K, the unimolecular decomposition of the fuel is the main consumption pathway.

Original languageEnglish
Pages (from-to)411-418
Number of pages8
JournalProceedings of the Combustion Institute
Volume34
Issue number1
DOIs
Publication statusPublished - 2013
Externally publishedYes

Keywords

  • Alkylbenzene
  • N-heptane
  • N-propylbenzene
  • Oxidation
  • Shock tube

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